| 1. |
- Caffrey, Jane M., et al.
(författare)
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Short exposure to oxygen and sulfide alter nitrification, denitrification, and DNRA activity in seasonally hypoxic estuarine sediments
- 2019
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 366:1
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Tidskriftsartikel (refereegranskat)abstract
- Increased organic loading to sediments from eutrophication often results in hypoxia, reduced nitrification and increased production of hydrogen sulfide, altering the balance between nitrogen removal and retention. We examined the effect of short-term exposure to various oxygen and sulfide concentrations on sediment nitrification, denitrification and DNRA from a chronically hypoxic basin in Roskilde Fjord, Denmark. Surprisingly, nitrification rates were highest in the hypoxic and anoxic treatments (about 5 μmol cm-3 d-1) and the high sulfide treatment was not significantly different than the oxic treatment. Denitrification in the hypoxic treatment was highest at 1.4 μmol cm-3 d-1 and significantly higher than the high sulfide treatment. For DNRA, the rate in high sulfide treatment was 2 μmol cm-3 d-1. This was significantly higher than all oxygen treatments that were near zero. In this system, nitrifiers rapidly recovered from conditions typically considered inhibiting, while denitrifiers had a more muted response. DNRA bacteria appear to depend on sulfide for nitrate reduction. Anammox was insignificant. Thus, in estuaries and coastal systems that experience short-term variations in oxygen and sulfide, capabilities of microbial communities are more diverse and tolerant of suboptimal conditions than some paradigms suggest.
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| 2. |
- Caputo, Andrea, et al.
(författare)
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The genetic diversity and evolution of diatom-diazotroph associations highlights traits favoring symbiont integration
- 2019
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 366:2
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Tidskriftsartikel (refereegranskat)abstract
- Diatom diazotroph associations (DDAs) are a widespread marine planktonic symbiosis between several diatom genera and di-nitrogen (N2)-fixing bacteria. Combining single cell confocal microscopy observations and molecular genetic approaches on individual field collected cells, we determined the phylogenetic diversity, distribution and evolution of the DDAs. Confocal analyses coupled with 3-D imaging re-evaluated the cellular location of DDA symbionts. DDA diversity was resolved by paired gene sequencing (18S rRNA and rbcL genes, 16S rRNA and nifH genes). A survey using the newly acquired sequences against public databases found sequences with high similarity (99–100%) to either host (18S rRNA) or symbiont (16S rRNA) in atypical regions for DDAs (high latitudes, anoxic basin and copepod gut). Concatenated phylogenies were congruent for the host and cyanobacteria sequences and implied co-evolution. Time-calibrated trees dated the appearance of N2 fixing planktonic symbiosis from 100–50Mya and were consistent with the symbiont cellular location: symbioses with internal partners are more ancient. An ancestral state reconstruction traced the evolution of traits in DDAs and highlight that the adaptive radiation to the marine environment was likely facilitated by the symbiosis. Our results present the evolutionary nature of DDAs and provide new genetic and phenotypic information for these biogeochemically relevant populations.
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| 3. |
- Charpentier, Emmanuelle
(författare)
-
Spotlight on... Emmanuelle Charpentier
- 2018
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press. - 0378-1097 .- 1574-6968. ; 365:4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Christel, Stephan, et al.
(författare)
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RNA transcript sequencing reveals inorganic sulfur compound oxidation pathways in the acidophile Acidithiobacillus ferrivorans
- 2016
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 363:7
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Tidskriftsartikel (refereegranskat)abstract
- Acidithiobacillus ferrivorans is an acidophile implicated in low-temperature biomining for the recovery of metals from sulfide minerals. Acidithiobacillus ferrivorans obtains its energy from the oxidation of inorganic sulfur compounds, and genes encoding several alternative pathways have been identified. Next-generation sequencing of At. ferrivorans RNA transcripts identified the genes coding for metabolic and electron transport proteins for energy conservation from tetrathionate as electron donor. RNA transcripts suggested that tetrathionate was hydrolyzed by the tetH1 gene product to form thiosulfate, elemental sulfur and sulfate. Despite two of the genes being truncated, RNA transcripts for the SoxXYZAB complex had higher levels than for thiosulfate quinone oxidoreductase (doxDA genes). However, a lack of heme-binding sites in soxX suggested that DoxDA was responsible for thiosulfate metabolism. Higher RNA transcript counts also suggested that elemental sulfur was metabolized by heterodisulfide reductase (hdr genes) rather than sulfur oxygenase reductase (sor). The sulfite produced as a product of heterodisulfide reductase was suggested to be oxidized by a pathway involving the sat gene product or abiotically react with elemental sulfur to form thiosulfate. Finally, several electron transport complexes were involved in energy conservation. This study has elucidated the previously unknown At. ferrivorans tetrathionate metabolic pathway that is important in biomining.
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| 5. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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Comparison of four DNA extraction methods for comprehensive assessment of 16S rRNA bacterial diversity in marine biofilms using high-throughput sequencing
- 2017
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 364:14
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Tidskriftsartikel (refereegranskat)abstract
- High-throughput DNA sequencing technologies are increasingly used for the metagenomic characterization of microbial biodiversity. However, basic issues, such as the choice of an appropriate DNA extraction method, are still not resolved for non-model microbial communities. This study evaluates four commonly used DNA extraction methods for marine periphyton biofilms in terms of DNA yield, efficiency, purity, integrity and resulting 16S rRNA bacterial diversity. Among the tested methods, the Plant DNAzol® Reagent (PlantDNAzol) and the Fast DNATM SPIN Kit for Soil (FastDNA Soil) methods were best suited to extract high quantities of DNA (77 - 130 μg g wet wt-1). Lower amounts of DNA were obtained (
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| 6. |
- Dalusi, Lucy, et al.
(författare)
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Toxigenic Vibrio cholerae identified in estuaries of Tanzania using PCR techniques
- 2015
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:5
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Tidskriftsartikel (refereegranskat)abstract
- The current study assessed the occurrence of the Vibrio cholerae serogroups O1 and O139 in environmental samples along salinity gradients in three selected estuaries of Tanzania both through culture independent methods and by cultured bacteria. Occurrence of V. cholerae was determined by PCR targeting the V. cholerae outer membrane protein gene ompW. Furthermore, the presence of toxigenic strains and serogroups O1 and O139 was determined using multiplex PCR with specific primers targeting the cholera toxin gene subunit A, ctxA, and serotype specific primers, O1-rfb and O139-rfb, respectively. Results showed that V. cholerae occurred in approximately 10% (n = 185) of both the environmental samples and isolated bacteria. Eight of the bacteria isolates (n = 43) were confirmed as serogroup O1 while one belonged to serogroup O139, the first reported identification of this epidemic strain in East African coastal waters. All samples identified as serogroup O1 or O139 and a number of non-O1/O139 strains were ctxA positive. This study provides in situ evidence of the presence of pathogenic V. cholerae O1 and O139 and a number of V. cholerae non-O1/O139 that carry the cholera toxin gene in estuaries along the coast of Tanzania.
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| 7. |
- Dehdarirad, Tahereh, 1984, et al.
(författare)
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Bibliometric mapping of microbiology research topics (2012-16): A comparison by socioeconomic development and infectious disease vulnerability values
- 2019
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968 .- 0378-1097. ; 366:2
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Forskningsöversikt (refereegranskat)abstract
- Amongst health-related scientific disciplines, microbiology appears to play a vital role in creating a sustainable future with respect to health, the environment and a biobased economy. Microbiology research covers a wide range of different disciplines and addresses many important global issues. This study aimed to identify topics being addressed within the last 5 years (2012-16) in the field of microbiology worldwide and to compare them in terms of three different indicators: gross domestic product, Human Development Index and Infectious Disease Vulnerability Index. The dataset of this study comprised 167 874 articles and reviews from 2012 to 2016, which were extracted from the Web of Science Medline. To identify and visualise the topics addressed during the studied period, VOSviewer was used. The construction and visualisation of the term map was done based on 5918 MESH subject headings. The methodology and procedures employed included Kruskal-Wallis test and two-sample proportion test. Overall, our study showed that the field of microbiology has focused on six different topics during 2012-16. The papers written with the collaboration of countries with low socioeconomic status and high vulnerability to infectious diseases mainly addressed topics related to the primary needs of people such as food safety, the prevention and control of infectious diseases, food and energy poverty. In contrast, papers written with the collaboration of countries with high socioeconomic development status and less vulnerability to infectious diseases mainly focused on big data, alternative methods to animal experiments.
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| 8. |
- Dombrowski, Nina, et al.
(författare)
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Genomic diversity, lifestyles and evolutionary origins of DPANN archaea
- 2019
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 366:2
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Forskningsöversikt (refereegranskat)abstract
- Archaea-a primary domain of life besides Bacteriahave for a long time been regarded as peculiar organisms that play marginal roles in biogeochemical cycles. However, this picture changed with the discovery of a large diversity of archaea in non-extreme environments enabled by the use of cultivation-independent methods. These approaches have allowed the reconstruction of genomes of uncultivated microorganisms and revealed that archaea are diverse and broadly distributed in the biosphere and seemingly include a large diversity of putative symbiotic organisms, most of which belong to the tentative archaeal superphylum referred to as DPANN. This archaeal group encompasses at least 10 different lineages and includes organisms with extremely small cell and genome sizes and limited metabolic capabilities. Therefore, many members of DPANN may be obligately dependent on symbiotic interactions with other organisms and may even include novel parasites. In this contribution, we review the current knowledge of the gene repertoires and lifestyles of members of this group and discuss their placement in the tree of life, which is the basis for our understanding of the deep microbial roots and the role of symbiosis in the evolution of life on Earth.
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| 9. |
- Esparza, Mario, et al.
(författare)
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Expression and activity of the Calvin-Benson-Bassham cycle transcriptional regulator CbbR from Acidithiobacillus ferrooxidans in Ralstonia eutropha
- 2015
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:15
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Tidskriftsartikel (refereegranskat)abstract
- Autotrophic fixation of carbon dioxide into cellular carbon occurs via several pathways but quantitatively, the Calvin-Benson-Bassham cycle is the most important. CbbR regulates the expression of the cbb genes involved in CO2 fixation via the Calvin-Benson-Bassham cycle in a number of autotrophic bacteria. A gene potentially encoding CbbR (cbbR(AF)) has been predicted in the genome of the chemolithoautotrophic, extreme acidophile Acidithiobacillus ferrooxidans. However, this microorganism is recalcitrant to genetic manipulation impeding the experimental validation of bioinformatic predictions. Two novel functional assays were devised to advance our understanding of cbbR(AF) function using the mutated facultative autotroph Ralstonia eutropha H14 Delta cbbR as a surrogate host to test gene function: (i) cbbR(AF) was expressed in R. eutropha and was able to complement Delta cbbR; and (ii) CbbR(AF) was able to regulate the in vivo activity of four A. ferrooxidans cbb operon promoters in R. eutropha. These results open up the use of R. eutropha as a surrogate host to explore cbbR(AF) activity.
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| 10. |
- Fischer, S, et al.
(författare)
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A unique methylation pattern by a type I HsdM methyltransferase prepares for DpnI rare cutting sites in the Pseudomonas aeruginosa PAO1 genome
- 2019
-
Ingår i: FEMS microbiology letters. - : Oxford University Press (OUP). - 1574-6968. ; 366:5
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Tidskriftsartikel (refereegranskat)abstract
- A physical genome map of Pseudomonas aeruginosa PAO1 had been constructed in the late 1980s by combinatorial SpeI/DpnI long-range restriction mapping. Whereas SpeI was known to cleave within the infrequent 5′-ACTAGT hexanucleotide, the rare recognition site 5′-Gm6ATC for the methylation-sensitive 4-cutter DpnI in the PAO1 genome remained elusive. Resequencing the PAO1 genome with the methylation-sensitive Single Molecule Real-Time (SMRT) sequencing technology identified DpnI to cleave the PAO1 genome at 15 palindromic GAC(N)6Gm6ATC(N)6GTC recognition sites with the central Gm6ATC palindrome to be methylated on both strands by the clone PAO1-specific type I HsdM superfamily methyltransferase M.PaePAOI (PA2735).
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| 11. |
- Friberg, Hanna, et al.
(författare)
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Preceding crop and tillage system affect winter survival of wheat and the fungal communities on young wheat roots and in soil
- 2019
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 366
-
Tidskriftsartikel (refereegranskat)abstract
- Agricultural practices like tillage and cropping sequence have profound influence on soil-living and plant-associated fungi, and thereby on plant growth. In a field experiment, we studied the effects of preceding crop and tillage on fungal communities in the soil and on young winter wheat roots in relation to plant winter survival and grain yield. We hypothesized that plant performance and fungal communities (described by amplicon sequencing) differ depending on tillage system and preceding crop; that the effect of preceding crop differs depending on tillage system, and that differences in fungal communities are reflected in plant performance. In line with our hypotheses, effects of preceding crop on plant growth and fungal communities on plant roots and in soil were more pronounced under non-inversion tillage than under inversion tillage (ploughing). Fungal communities on plant roots in treatments with low winter survival were different from those with better survival. In soil, several fungal OTUs (operational taxonomic units) differed significantly between tillage systems. OTUs representing putative plant pathogens were either more abundant (Parastagonospora sp._27) or less abundant (Fusarium culmorum/graminearum 5) after non-inversion tillage. Our findings highlight the influence of cultural practices on fungal communities and thereby on plant health and yield.
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| 12. |
- Hatti-Kaul, Rajni, et al.
(författare)
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Lactic acid bacteria : From starter cultures to producers of chemicals
- 2018
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 365:20
-
Forskningsöversikt (refereegranskat)abstract
- Lactic acid bacteria constitute a diverse group of industrially significant, safe microorganisms that are primarily used as starter cultures and probiotics, and are also being developed as production systems in industrial biotechnology for biocatalysis and transformation of renewable feedstocks to commodity- and high-value chemicals, and health products. Development of strains, which was initially based mainly on natural approaches, is also achieved by metabolic engineering that has been facilitated by the availability of genome sequences and genetic tools for transformation of some of the bacterial strains. The aim of this paper is to provide a brief overview of the potential of lactic acid bacteria as biological catalysts for production of different organic compounds for food and non-food sectors based on their diversity, metabolicand stress tolerance features, as well as the use of genetic/metabolic engineering tools for enhancing their capabilities.
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| 13. |
- Hellberg Lindqvist, Miriam, 1982-, et al.
(författare)
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Chlorate reductase is cotranscribed with cytochrome c and other downstream genes in the gene cluster for chlorate respiration of Ideonella dechloratans
- 2015
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:6
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Tidskriftsartikel (refereegranskat)abstract
- The chlorate-respiring bacterium Ideonella dechloratans is a facultative anaerobe that can use both oxygen and chlorate as terminal electron acceptors. The genes for the enzymes chlorate reductase (clrABDC) and chlorite dismutase, necessary for chlorate metabolism and probably acquired by lateral gene transfer, are located in a gene cluster that also includes other genes potentially important for chlorate metabolism. Among those are a gene for cytochrome c (cyc) whose gene product may serve as an electron carrier during chlorate reduction, a cofactor biosynthesis gene (mobB) and a predicted transcriptional regulator (arsR). Only chlorate reductase and chlorite dismutase have been shown to be expressed in vivo. Here, we report the in vivo production of a single polycistronic transcript covering eight open reading frames including clrABDC, cyc, mobB and arsR. Transcription levels of the cyc and clrA genes were compared to each other by the use of qRT-PCR in RNA preparations from cells grown under aerobic or chlorate reducing anaerobic conditions. The two genes showed the same mRNA levels under both growth regimes, indicating that no transcription termination occurs between them. Higher transcription levels were observed at growth without external oxygen supply. Implications for electron pathway integration following lateral gene transfer are discussed.
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| 14. |
- Karyolaimos, Alexandros, et al.
(författare)
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Shaping Escherichia coli for recombinant membrane protein production
- 2018
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 365:15
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Forskningsöversikt (refereegranskat)abstract
- The bacterium Escherichia coli has been widely used for the production of both pro- and eukaryotic membrane proteins. Usually, a set of standard strains as well as different culture setups and induction regimes are screened for to enhance production yields. However, on a limited scale, E. coli strains have been isolated for recombinant helical bundle membrane protein production using both selection- and engineering-based approaches. Here, we discuss how such approaches have been used so far to shape E. coli for the production of these recombinant membrane proteins and may be used in the future to further enhance production yields.
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| 15. |
- Kejzar, A., et al.
(författare)
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The unique characteristics of HOG pathway MAPKs in the extremely halotolerant Hortaea werneckii
- 2015
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Ingår i: Fems Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:8
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Tidskriftsartikel (refereegranskat)abstract
- HwHog1A/B, Hortaea werneckii homologues of the MAP kinase Hog1 from Saccharomyces cerevisiae, are vital for the extreme halotolerance of H. werneckii. In mesophilic S. cerevisiae, Hog1 is phosphorylated already at low osmolyte concentrations, and regulates expression of a similar set of genes independent of osmolyte type. To understand how HwHog1 kinases activity is regulated in H. werneckii, we studied HwHog1A/B activation in vivo, by following phosphorylation of HwHog1A/B in H. werneckii exposed to various osmolytes, and in vitro, by measuring kinase activities of recombinant HwHog1A, HwHog1B and Hog1 Delta C. To this end, highly pure and soluble recombinant Hog1 homologues were isolated from insect cells. Our results demonstrate that HwHog1A/B are, in general, transiently phosphorylated in cells shocked with = 3 M osmolyte, yet constitutive phosphorylation is observed at extreme NaCl and KCl concentrations. Importantly, phosphorylation profiles differ depending on the osmolyte type. Additionally, phosphorylated recombinant HwHog1A/B show lower specific kinase activities compared to Hog1 Delta C. In summary, HOG pathway MAPKs in the extremely halotolerant H. werneckii show unique characteristics compared to S. cerevisiae homologues. The reported findings contribute to defining the key determinants of H. werneckii osmotolerance, which is important for its potential transfer to economically relevant microorganisms and crops.
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| 16. |
- Kondori, Nahid, 1967, et al.
(författare)
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Analyses of black fungi by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS): Species-level identification of clinical isolates of Exophiala dermatitidis
- 2015
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:1
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Tidskriftsartikel (refereegranskat)abstract
- © FEMS 2014. Conventional mycological identifications based on the recognition of morphological characteristics can be problematic. A relatively new methodology applicable for the identification of microorganisms is based on the exploitation of taxonspecific mass patterns recorded from abundant cell proteins directly from whole-cell preparations, using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). This study reports the application of MALDI-TOF MS for the differentiation and identifications of black yeasts, isolated from the respiratory tracts of patients with cystic fibrosis (CF). Initial phenotypic and DNA sequence-based analyses identified these isolates to be Exophiala dermatitidis. The type strains of E. dermatitidis (CBS 207.35T) and other species of Exophiala were included in the MALDI-TOF MS analyses to establish the references for comparing the mass spectra of the clinical isolates of Exophiala. MALDI-TOF MS analyses exhibited extremely close relationships among the clinical isolates and with the spectra generated from the type strain of E. dermatitidis. The relationships observed between the E. dermatitidis strains from the MALDI-TOF MS profiling analyses were supported by DNA sequence-based analyses of the rRNA ITS1 and ITS2 regions. These data demonstrated the applicability of MALDI-TOF MS as a reliable, rapid and cost-effective method for the identification of isolates of E. dermatitidis and other clinically relevant fungi and yeasts that typically are difficult to identify by conventional methods.
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| 17. |
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| 18. |
- Li, Xin, et al.
(författare)
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Differential transcriptional regulation of orthologous dps genes from two closely related heterocyst-forming cyanobacteria
- 2015
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:6
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Tidskriftsartikel (refereegranskat)abstract
- In cyanobacteria, DNA-binding proteins from starved cells (Dps) play an important role in the cellular response to oxidative and nutritional stresses. In this study, we have characterized the cell-type specificity and the promoter regions of two orthologous dps genes, Npun_R5799 in Nostoc punctiforme and alr3808 in Anabaena sp. PCC 7120. A transcriptional start site (TSS), identical in location to the previously identified proximal TSS of alr3808, was identified for Npun_R5799 under both combined nitrogen supplemented and N-2-fixing growth conditions. However, only alr3808 was also transcribed from a second distal TSS. Sequence homologies suggest that the promoter region containing the distal TSS is not conserved upstream of orthologous genes among heterocyst-forming cyanobacteria. The analysis of promoter GFP-reporter strains showed a different role in governing cell-type specificity between the proximal and distal promoter of alr3808. We here confirmed the heterocyst specificity of the distal promoter of alr3808 and described a very early induction of its expression during proheterocyst differentiation. In contrast, the complete promoters of both genes were active in all cells. Even though Npun_R5799 and alr3808 are orthologs, the regulation of their respective expression differs, indicating distinctions in the function of these cyanobacterial Dps proteins depending on the strain and cell type.
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| 19. |
- Li, Xin, et al.
(författare)
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Homologous overexpression of NpDps2 and NpDps5 increases the tolerance for oxidative stress in the multicellular cyanobacterium Nostoc punctiforme
- 2018
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 365:18
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Tidskriftsartikel (refereegranskat)abstract
- The filamentous cyanobacterium Nostoc punctiforme has several oxidative stress-managing systems, including Dps proteins. Dps proteins belong to the ferritin superfamily and are involved in abiotic stress management in prokaryotes. Previously, we found that one of the five Dps proteins in N. punctiforme, NpDps2, was critical for H2O2 tolerance. Stress induced by high light intensities is aggravated in N. punctiforme strains deficient of either NpDps2, or the bacterioferritin-like NpDps5. Here, we have investigated the capacity of NpDps2 and NpDps5 to enhance stress tolerance by homologous overexpression of these two proteins in N. punctiforme. Both overexpression strains were found to tolerate twice as high concentrations of added H2O2 as the control strain, indicating that overexpression of either NpDps2 or NpDps5 will enhance the capacity for H2O2 tolerance. Under high light intensities, the overexpression of the two NpDps did not enhance the tolerance against general light-induced stress. However, overexpression of the heterocyst-specific NpDps5 in all cells of the filament led to a higher amount of chlorophyll-binding proteins per cell during diazotrophic growth. The OENpDps5 strain also showed an increased tolerance to ammonium-induced oxidative stress. Our results provide information of how Dps proteins may be utilised for engineering of cyanobacteria with enhanced stress tolerance.
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| 20. |
- Loftsdottir, Heidur, et al.
(författare)
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Dynamics of insertion sequence element IS629 inactivation of verotoxin 2 genes in Escherichia coli O157:H7
- 2017
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press. - 0378-1097 .- 1574-6968. ; 364:8
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Tidskriftsartikel (refereegranskat)abstract
- There are several anecdotal reports of insertion sequence (IS) element inactivation of verotoxin genes among enterohaemorrhagic Escherichia coli of the serotype O157:H7, a pathogen causing severe gastrointestinal disease in infected humans. These insertions can be expected to drastically reduce the virulence of the bacteria. IS element inactivation has been shown to be reversible in model systems, suggesting the possibility of spontaneous restoration of virulence. In this study, traditional and high-throughput sequencing was used to characterise three patterns of IS629 inactivation of verotoxin 2 genes in EHEC O157:H7, caused by insertion or insertion followed by partial deletion. At least one of the patterns of inactivation appears to have persisted several years among cattle O157:H7, indicating it has no major effect on fitness in the animal reservoir. Digital PCR was used to directly quantify the reversal rates of the insertional inactivation of a selected isolate under laboratory conditions. Inserts were found to be absent from in the order of 1/10(5) of individual genomes, with significantly higher loss frequencies observed in cultures under nutrient-poor conditions. We conclude that strains with this type of inactivation found in food or animal samples should be considered a threat to human health, and may pose a challenge for PCR-based detection methods.
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| 21. |
- Molinas, Andrea, et al.
(författare)
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Protective role of host aquaporin 6 against Hazara virus, a model for Crimean–Congo hemorrhagic fever virus infection
- 2016
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press. - 0378-1097 .- 1574-6968. ; 363:8
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Tidskriftsartikel (refereegranskat)abstract
- Crimean–Congo hemorrhagic fever virus (CCHFV) is an arthropod-borne pathogen that causes infectious disease with severe hemorrhagic manifestations in vascular system in humans. The proper function of the cells in the vascular system is critically regulated by aquaporins (AQP), water channels that facilitate fluxes of water and small solutes across membranes. With Hazara virus as a model for CCHFV, we investigated the effects of viruses on AQP6 and the impact of AQP6 on virus infectivity in host cells, using transiently expressed GFP-AQP6 cells, immunofluorescent assay for virus detection, epifluorescent imaging of living cells and confocal microscopy. In GFP-AQP6 expressing cells, Hazara virus reduced both the cellular and perinuclear AQP6 distribution and changed the cell area. Infection of human cell with CCHFV strain IbAR 10200 downregulated AQP6 expression at mRNA level. Interestingly, the overexpression of AQP6 in host cells decreased the infectivity of Hazara virus, speaking for a protective role of AQP6. We suggest the possibility for AQP6 being a novel player in the virus–host interactions, which may lead to less severe outcomes of an infection.
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| 22. |
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| 23. |
- Nancucheo, Ivan, et al.
(författare)
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Solid and liquid media for isolating and cultivating acidophilic and acid-tolerant sulfate-reducing bacteria
- 2016
-
Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 363:10
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Tidskriftsartikel (refereegranskat)abstract
- Growth media have been developed to facilitate the enrichment and isolation of acidophilic and acid-tolerant sulfate-reducing bacteria (aSRB) from environmental and industrial samples, and to allow their cultivation in vitro. The main features of the 'standard' solid and liquid devised media are as follows: (i) use of glycerol rather than an aliphatic acid as electron donor; (ii) inclusion of stoichiometric concentrations of zinc ions to both buffer pH and to convert potentially harmful hydrogen sulphide produced by the aSRB to insoluble zinc sulphide; (iii) inclusion of Acidocella aromatica (an heterotrophic acidophile that does not metabolize glycerol or yeast extract) in the gel underlayer of double layered (overlay) solid media, to remove acetic acid produced by aSRB that incompletely oxidize glycerol and also aliphatic acids (mostly pyruvic) released by acid hydrolysis of the gelling agent used (agarose). Colonies of aSRB are readily distinguished from those of other anaerobes due to their deposition and accumulation of metal sulphide precipitates. Data presented illustrate the effectiveness of the overlay solid media described for isolating aSRB from acidic anaerobic sediments and low pH sulfidogenic bioreactors.
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| 24. |
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| 25. |
- Ozoline, Olga N., et al.
(författare)
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Secretion and signalling of bacterial RNAs
- 2019
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press. - 0378-1097 .- 1574-6968. ; 366:1
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Tidskriftsartikel (refereegranskat)
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| 26. |
- Plominsky, Alvaro M., et al.
(författare)
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Intercellular transfer along the trichomes of the invasive terminal heterocyst forming cyanobacterium Cylindrospermopsis raciborskii CS-505
- 2015
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:5
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Tidskriftsartikel (refereegranskat)abstract
- Cylindrospermopsis raciborskii CS-505 is an invasive freshwater filamentous cyanobacterium that when grown diazotrophically may develop trichomes of up to 100 vegetative cells while differentiating only two end heterocysts, the sole sites for their N-2-fixation process. We examined the diazotrophic growth and intercellular transfer mechanisms in C. raciborskii CS-505. Subjecting cultures to a combined-nitrogen-free medium to elicit N-2 fixation, the trichome length remained unaffected while growth rates decreased. The structures and proteins for intercellular communication showed that while a continuous periplasmic space was apparent along the trichomes, the putative septal junction sepJ gene is divided into two open reading frames and lacks several transmembrane domains unlike the situation in Anabaena, differentiating a 5-fold higher frequency of heterocysts. FRAP analyses also showed that the dyes calcein and 5-CFDA were taken up by heterocysts and vegetative cells, and that the transfer from heterocysts and 'terminal' vegetative cells showed considerably higher transfer rates than that from vegetative cells located in the middle of the trichomes. The data suggest that C. raciborskii CS-505 compensates its low-frequency heterocyst phenotype by a highly efficient transfer of the fixed nitrogen towards cells in distal parts of the trichomes (growing rapidly) while cells in central parts suffers (slow growth).
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| 27. |
- Shashkova, Sviatlana, 1987, et al.
(författare)
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The yeast Mig1 transcriptional repressor is dephosphorylated by glucose-dependent and -independent mechanisms
- 2017
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Ingår i: Fems Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 364:14
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Tidskriftsartikel (refereegranskat)abstract
- A yeast Saccharomyces cerevisiae Snf1 kinase, an analog of mammalian AMPK, regulates glucose derepression of genes required for utilization of alternative carbon sources through the transcriptional repressor Mig1. It has been suggested that the Glc7-Reg1 phosphatase dephosphorylates Mig1. Here we report that Mig1 is dephosphorylated by Glc7-Reg1 in an apparently glucose-dependent mechanism but also by a mechanism independent of glucose and Glc7-Reg1. In addition to serine/threonine phosphatases another process including tyrosine phosphorylation seems crucial for Mig1 regulation. Taken together, Mig1 dephosphorylation appears to be controlled in a complex manner, in line with the importance for rapid and sensitive regulation upon altered glucose concentrations in the growth medium.
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| 28. |
- Sjöblom, Magnus, et al.
(författare)
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Catalytic upgrading of butyric acid towards fine chemicals and biofuels
- 2016
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 363:8
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Tidskriftsartikel (refereegranskat)abstract
- Fermentation based production of butyric acid is robust and efficient. Modern catalytic technologies make it possible to convert butyric acid to important fine chemicals and biofuels. Here current chemocatalytic and biocatalytic conversion methods are reviewed with a focus on upgrading butyric acid to 1-butanol or butyl-butyrate. Supported Ruthenium and Platinum based catalyst and lipase exhibit important activities which can pave the way for more sustainable process concepts for the production of green fuels and chemicals.
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| 29. |
- Sundh, Ingvar
(författare)
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The qualified presumption of safety assessment and its role in EFSA risk evaluations: 15 years past
- 2019
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 366
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Forskningsöversikt (refereegranskat)abstract
- Microorganisms are intentionally added at different stages of the food and feed chain (food or feed additive, novel food or plant protection product) and are subjected to regulation and safety assessment by the European Food Safety Authority. Safety evaluation is based on application dossiers for market authorisation to the European Commission. The qualified presumption of safety (QPS) concept was developed in 2003(2) to provide a harmonised generic safety pre-appraisal of the above microorganisms. Unambiguously defined biological taxonomic units (TUs) are assessed for their body of knowledge, their safety and their end use. Identified safety concerns for a certain TU can be, where reasonable in number and not universally present, reflected as 'qualifications.' Strains belonging to TUs having QPS status may benefit of a fast track evaluation. The lowest TU for which the QPS status is granted is the species level for bacteria and yeasts and the family for viruses. The QPS concept is also applicable to genetically modified microorganisms used for production purposes. Based on the current body of knowledge and/or the ambiguous taxonomic position, some TUs, such as filamentous fungi, bacteriophages, Enterococcus faecium, Escherichia coli, Streptomyces spp. and Oomycetes, are not considered liable for QPS status.
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| 30. |
- Székely, Anna J., et al.
(författare)
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Single-stranded DNA phages : from early molecular biology tools to recent revolutions in environmental microbiology
- 2016
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 363:6
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Forskningsöversikt (refereegranskat)abstract
- Single-stranded DNA (ssDNA) phages are profoundly different from tailed phages in many aspects including the nature and size of their genome, virion size and morphology, mutation rate, involvement in horizontal gene transfer, infection dynamics and cell lysis mechanisms. Despite the importance of ssDNA phages as molecular biology tools and model systems, the environmental distribution and ecological roles of these phages have been largely unexplored. Viral metagenomics and other culture-independent viral diversity studies have recently challenged the perspective of tailed, double-stranded DNA (dsDNA) phages, dominance by demonstrating the prevalence of ssDNA phages in diverse habitats. However, the differences between ssDNA and dsDNA phages also substantially limit the efficacy of simultaneously assessing the abundance and diversity of these two phage groups. Here we provide an overview of the major differences between ssDNA and tailed dsDNA phages that may influence their effects on bacterial communities. Furthermore, through the analysis of 181 published metaviromes we demonstrate the environmental distribution of ssDNA phages and present an analysis of the methodological biases that distort their study through metagenomics.
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| 31. |
- Tiukova, Ievgeniia, 1987, et al.
(författare)
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Identification and characterisation of two high-affinity glucose transporters from the spoilage yeast Brettanomyces bruxellensis
- 2019
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Ingår i: FEMS microbiology letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 366:17
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Tidskriftsartikel (refereegranskat)abstract
- The yeast Brettanomyces bruxellensis (syn. Dekkera bruxellensis) is an emerging and undesirable contaminant in industrial low-sugar ethanol fermentations that employ the yeast Saccharomyces cerevisiae. High-affinity glucose import in B. bruxellensis has been proposed to be the mechanism by which this yeast can outcompete S. cerevisiae. The present study describes the characterization of two B. bruxellensis genes (BHT1 and BHT3) believed to encode putative high-affinity glucose transporters. In vitro-generated transcripts of both genes as well as the S. cerevisiae HXT7 high-affinity glucose transporter were injected into Xenopus laevis oocytes and subsequent glucose uptake rates were assayed using 14C-labelled glucose. At 0.1 mM glucose, Bht1p was shown to transport glucose five times faster than Hxt7p. pH affected the rate of glucose transport by Bht1p and Bht3p, indicating an active glucose transport mechanism that involves proton symport. These results suggest a possible role for BHT1 and BHT3 in the competitive ability of B. bruxellensis.
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| 32. |
- Turkina, Maria V, et al.
(författare)
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Helicobacter pylori vesicles carrying CagA localize in the vicinity of cell-cell contacts and induce histone H1 binding to ATP in epithelial cells
- 2015
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 362:11
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Tidskriftsartikel (refereegranskat)abstract
- Helicobacter pylori produces outer membrane vesicles (OMV), delivering bacterial substances including the oncogenic cytotoxin-associated CagA protein to their surroundings. We investigated the effects of H. pylori OMV carrying CagA (OMV-CagA) on cell junctions and ATP-binding proteome of epithelial monolayers, using proteomics, mass spectrometry and imaging. OMV-CagA localized in close vicinity of ZO-1 tight junction protein and induced histone H1 binding to ATP. We suggest the expression of novel events in the interactions between H. pylori OMV and epithelia, which may have an influence on host gene transcription and lead to different outcomes of an infection and development of cancer.
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| 33. |
- Wang, Helen, et al.
(författare)
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Energy shifts induce membrane sequestration of DraG in Rhodospirillum rubrum independent of the ammonium transporters and diazotrophic conditions
- 2018
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 0378-1097 .- 1574-6968. ; 365:16
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic regulation of Rhodospirillum rubrum nitrogenase is mediated at the post-translational level by the enzymes DraT and DraG when subjected to changes in nitrogen or energy status. DraT is activated during switch-off, while DraG is inactivated by reversible membrane association. We confirm here that the ammonium transporter, AmtB1, rather than its paralog AmtB2, is required for ammonium induced switch-off. Amongst several substitutions at the N100 position in DraG, only N100K failed to locate to the membrane following ammonium shock, suggesting loss of interaction through charge repulsion. When switch-off was induced by lowering energy levels, either by darkness during photosynthetic growth or oxygen depletion under respiratory conditions, reversible membrane sequestration of DraG was independent of AmtB proteins and occurred even under non-diazotrophic conditions. We propose that under these conditions, changes in redox status or possibly membrane potential induce interactions between DraG and another membrane protein in response to the energy status.
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