| 1. |
- Bentzon-Tilia, Mikkel, et al.
(författare)
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Cultivation and isolation of N2-fixing bacteria from suboxic waters in the Baltic Sea
- 2014
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 88:2, s. 358-371
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogenase genes (nifH) from heterotrophic dinitrogen (N-2)-fixing bacteria appear ubiquitous in marine bacterioplankton, but the significance of these bacteria for N cycling is unknown. Quantitative data on the N-2-fixation potential of marine and estuarine heterotrophs are scarce, and the shortage of cultivated specimens currently precludes ecophysiological characterization of these bacteria. Through the cultivation of diazotrophs from suboxic (1.79molO(2)L(-1)) Baltic Sea water in an artificial seawater medium devoid of combined N, we report the cultivability of a considerable fraction of the diazotrophic community in the Gotland Deep. Two nifH clades were present both in situ and in enrichment cultures showing gene abundances of up to 4.6x10(5) and 5.8x10(5)nifH gene copies L-1 within two vertical profiles in the Baltic Sea. The distributions of the two clades suggested a relationship with the O-2 concentrations in the water column as abundances increased in the suboxic and anoxic waters. It was possible to cultivate and isolate representatives from one of these prevalent clades, and preliminary analysis of their ecophysiology demonstrated growth optima at 0.5-15molO(2)L(-1) and 186-194molO(2)L(-1) in the absence of combined N.
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| 2. |
- Björk, Robert G., 1974, et al.
(författare)
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Contrasting effects of wood ash application on microbial community structure, biomass and processes in drained forested peatlands
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 73:3, s. 550-562
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Tidskriftsartikel (refereegranskat)abstract
- The effects of wood ash application on soil microbial processes were investigated in three drained forested peatlands, which differed in nutrient status and time since application. Measured variables included concentrations of soil elements and phospholipid fatty acids (PLFAs), net nitrogen mineralisation, nitrification and denitrification enzyme activity, potential methane oxidation, methane production and microbial respiration kinetics. Wood ash application had a considerable influence on soil element concentrations. This mirrored a decrease in the majority of the microbial biomarkers by more than one-third in the two oligotrophic peatlands, although microbial community composition was not altered. The decreases in PLFAs coincided with reduced net ammonification and net nitrogen mineralisation. Other measured variables did not change systematically as a result of wood ash application. No significant changes in microbial biomass or processes were found in the mesotrophic peatland, possibly because too little time (1 year) had elapsed since the wood ash application. This study suggests that oligotrophic peatlands can be substantially affected by wood ash for a period of at least four years after application. However, within 25 years of the wood ash application, the microbial biomass seemed to have recovered or adapted to enhanced element concentrations in the soil.
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| 3. |
- Collin, Betty, 1976, et al.
(författare)
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Characteristics of potentially pathogenic vibrios from subtropical Mozambique compared with isolates from tropical India and boreal Sweden
- 2013
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Ingår i: Fems Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 83:2, s. 255-264
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Tidskriftsartikel (refereegranskat)abstract
- Reported outbreaks of Vibrio parahaemolyticus have increased worldwide, particularly in regions of high seafood consumption. In Mozambique, seafood constitutes an important food resource and diarrheal diseases are common among its inhabitants. Edible clams were collected in Maputo Bay during both the dry and rainy seasons, with the results showing the number of viable counts of vibrios in clams to peak during the latter. Vibrio parahaemolyticus was the predominant species identified among the isolated strains. Although only one of 109 total strains carried the tdh virulence gene, 69% of isolates showed evidence of hemolytic capacity when subjected to a functional test. Similar virulence patterns and biochemical properties were found in strains isolated from Indian and Swedish marine waters. Antibiotic resistance was, however, more pronounced in strains isolated from these latter two environments.
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| 4. |
- Collin, Betty, 1976-, et al.
(författare)
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Occurrence and potential pathogenesis of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus on the South Coast of Sweden
- 2011
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Ingår i: FEMS Microbiology Ecology. - 0168-6496 .- 1574-6941. ; 78:2, s. 306-313
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Tidskriftsartikel (refereegranskat)abstract
- During the summer of 2006, several wound infections - of which three were fatal caused by Vibrio cholerae were reported from patients who had been exposed to water from the Baltic Sea. Before these reports, we initiated a sampling project investigating the occurrence of potential human pathogenic V. cholerae, Vibrio vulnificus and Vibrio parahaemolyticus in The Sound between Sweden and Denmark. The Blue mussel (Mytilus edulis) was used as an indicator to follow the occurrence of vibrios over time. Molecular analyses showed high frequencies of the most potent human pathogenic Vibrio spp.; 53% of mussel samples were positive for V. cholerae (although none were positive for the cholera toxin gene), 63% for V. vulnificus and 79% for V. parahaemolyticus (of which 47% were tdh(+) and/or trh(+)). Viable vibrios were also isolated from the mussel meat and screened for virulence by PCR. The mortality of eukaryotic cells when exposed to bacteria was tested in vivo, with results showing that the Vibrio strains, independent of species and origin, were harmful to the cells. Despite severe infections and several deaths, no report on potential human pathogenic vibrios in this area had been published before this study.
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| 5. |
- Collin, Betty, 1976, et al.
(författare)
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Occurrence and potential pathogenesis of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus on the South Coast of Sweden
- 2011
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Ingår i: FEMS MICROBIOLOGY ECOLOGY. - : Oxford University Press. - 0168-6496 .- 1574-6941. ; 78:2, s. 306-313
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Tidskriftsartikel (refereegranskat)abstract
- During the summer of 2006, several wound infections - of which three were fatal - caused by Vibrio cholerae were reported from patients who had been exposed to water from the Baltic Sea. Before these reports, we initiated a sampling project investigating the occurrence of potential human pathogenic V. cholerae, Vibrio vulnificus and Vibrio parahaemolyticus in The Sound between Sweden and Denmark. The Blue mussel (Mytilus edulis) was used as an indicator to follow the occurrence of vibrios over time. Molecular analyses showed high frequencies of the most potent human pathogenic Vibrio spp.; 53% of mussel samples were positive for V. cholerae (although none were positive for the cholera toxin gene), 63% for V. vulnificus and 79% for V. parahaemolyticus (of which 47% were tdh(+) and/or trh(+)). Viable vibrios were also isolated from the mussel meat and screened for virulence by PCR. The mortality of eukaryotic cells when exposed to bacteria was tested in vivo, with results showing that the Vibrio strains, independent of species and origin, were harmful to the cells. Despite severe infections and several deaths, no report on potential human pathogenic vibrios in this area had been published before this study.
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| 6. |
- Feng, Xin Mei, et al.
(författare)
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Impact of trace element addition on biogas production from food industrial waste - linking process to microbial communities
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 74:1, s. 226-240
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory-scale reactors treating food industry waste were used to investigate the effects of additions of cobalt (Co), nickel/molybdenum/boron (Ni/Mo/B) and selenium/tungsten (Se/W) on the biogas process and the associated microbial community. The highest methane production (predicted value: 860 mL g-1 VS) was linked to high Se/W concentrations in combination with a low level of Co. A combination of quantitative real-time PCR of 16S rRNA genes, terminal restriction fragment length polymorphism (T-RFLP) and clone library sequencing was used for the community analysis. The T-RFLP data show a higher diversity for bacteria than for archaea in all the treatments. The most abundant bacterial population (31-55% of the total T-RFLP fragments' intensity) was most closely related to Actinomyces europaeus (94% homology). Two dominant archaeal populations shared 98-99% sequence homology with Methanosarcina siciliae and Methanoculleus bourgensis, respectively. Only limited influence of the trace metal additions was found on the bacterial community composition, with two bacterial populations responding to the addition of a combination of Ni/Mo/B, while the dominant archaeal populations were influenced by the addition of Ni/Mo/B and/or Se/W. The maintenance of methanogenic activity was largely independent of archaeal community composition, suggesting a high degree of functional redundancy in the methanogens of the biogas reactors.
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| 7. |
- Fernandez-Calvino, David, et al.
(författare)
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Growth response of the bacterial community to pH in soils differing in pH
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 73:1, s. 149-156
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Tidskriftsartikel (refereegranskat)abstract
- The effect of pH on the instantaneous growth of soil bacterial communities was studied in five soils with different pH (4.5-7.8) using leucine (Leu) and thymidine (TdR) incorporation. The pH dependency of bacterial growth was modelled using three different unimodal functions, and the pH(opt) for growth and the pH range in which growth was > 50% of the optimal growth were compared. Leu and TdR incorporation yielded very similar results. The best fits were obtained using a third-degree polynomial function and the cardinal pH model. However, a simple second-degree function was adequate in most cases, yielding very similar pH(opt) values to the other two models. Bacterial growth was highly influenced by pH, showing optimum growth at a pH related to the soil pH. The lowest pH(opt) was found in the most acidic soil and the highest pH(opt) in the soil with the highest pH. The pH(opt) for bacterial growth was close to the soil pH measured in water, but higher (0.7-2.1 units) than the pH measured with 0.1 M KCl. The pH range in which bacterial growth was > 50% of that at optimum was, on average, 1.7 units below and above the optimum pH.
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| 8. |
- Figge, Marian J, et al.
(författare)
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Historical microbiology : revival and phylogenetic analysis of the luminous bacterial cultures of M. W. Beijerinck.
- 2011
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 78:3, s. 463-72
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Tidskriftsartikel (refereegranskat)abstract
- Luminous bacteria isolated by Martinus W. Beijerinck were sealed in glass ampoules in 1924 and 1925 and stored under the names Photobacterium phosphoreum and 'Photobacterium splendidum'. To determine if the stored cultures were viable and to assess their evolutionary relationship with currently recognized bacteria, portions of the ampoule contents were inoculated into culture medium. Growth and luminescence were evident after 13 days of incubation, indicating the presence of viable cells after more than 80 years of storage. The Beijerinck strains are apparently the oldest bacterial cultures to be revived from storage. Multi-locus sequence analysis, based on the 16S rRNA, gapA, gyrB, pyrH, recA, luxA, and luxB genes, revealed that the Beijerinck strains are distant from the type strains of P. phosphoreum, ATCC 11040(T), and Vibrio splendidus, ATCC 33125(T), and instead form an evolutionarily distinct clade of Vibrio. Newly isolated strains from coastal seawater in Norway, France, Uruguay, Mexico, and Japan grouped with the Beijerinck strains, indicating a global distribution for this new clade, designated as the beijerinckii clade. Strains of the beijerinckii clade exhibited little sequence variation for the seven genes and approximately 6300 nucleotides examined despite the geographic distances and the more than 80 years separating their isolation. Gram-negative bacteria therefore can survive for many decades in liquid storage, and in nature, they do not necessarily diverge rapidly over time.
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| 9. |
- Fransson, Petra, et al.
(författare)
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Elevated CO2 and nitrogen influence exudation of soluble organic compounds by ectomycorrhizal root systems
- 2010
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Ingår i: FEMS Microbiology Ecology. - Hoboken, USA : Wiley-Blackwell. - 0168-6496 .- 1574-6941. ; 71:2, s. 186-196
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Tidskriftsartikel (refereegranskat)abstract
- Root and mycelial exudation contributes significantly to soil carbon (C) fluxes, and is likely to be altered by an elevated atmospheric carbon dioxide (CO2) concentration and nitrogen (N) deposition. We quantified soluble, low-molecular-weight (LMW) organic compounds exuded by ectomycorrhizal plants grown under ambient (360 p.p.m.) or elevated (710 p.p.m.) CO2 concentrations and with different N sources. Scots pine seedlings, colonized by one of five different ectomycorrhizal or nonmycorrhizal fungi, received 70 μM N, either as NH4Cl or as alanine, in a liquid growth medium. Exudation of LMW organic acids (LMWOAs), dissolved monosaccharides and total dissolved organic carbon were determined. Both N and CO2 had a significant impact on exudation, especially of LMWOAs. Exudation of LMWOAs was negatively affected by inorganic N and decreased by 30–85% compared with the organic N treatment, irrespective of the CO2 treatment. Elevated CO2 had a clear impact on the production of individual LMWOAs, although with very contrasting effects depending on which N source was supplied.
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| 10. |
- Hallbeck, Lotta, 1957, et al.
(författare)
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Culture-dependent comparison of microbial diversity in deep granitic groundwater from two sites considered for a Swedish final repository of spent nuclear fuel
- 2012
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 1574-6941 .- 0168-6496. ; 81:1, s. 66-77
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Tidskriftsartikel (refereegranskat)abstract
- Site selection for a spent nuclear fuel (SNF) repository required analysis of microbial abundance and diversity at two Swedish sites, Forsmark and Laxemar-Simpevarp. Information about sulphate-reducing bacteria (SRB) was required, as sulphide could corrode copper SNF canisters. Total number of cells (TNC) and ATP were analysed, and plate counts and most probable number (MPN) analyses were conducted using eight media based on different electron donors and acceptors for specific microorganism physiological groups. Groundwater chemical composition and Eh were analysed; sampling depths were 112-978 m below sea level. TNC was 5.5 × 103 to 4.7 × 105 cells mL-1, correlating with ATP concentrations. Culturability in TNC percentage was 0.01-35.9, averaging 5.12. Culturable numbers varied greatly between sample positions and uncorrelated with depth. SRB were found in 29 samples and were below detection in three; the MPN of SRB correlated negatively with Eh, as did the MPN of acetogens. Data indicated that microbial sulphate reduction was ongoing in many sampled aquifers; published stable isotope data and modelling results supported this observation. The sites did not differ significantly, but the large data range suggested that analysis of more samples would enable detailed evaluation of microbial processes and their relationship with geochemical information. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
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