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| 2. |
- Buetti-Dinh, Antoine, et al.
(författare)
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Transcriptomic analysis reveals how a lack of potassium ions increases Sulfolobus acidocaldarius sensitivity to pH changes
- 2016
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 162:8, s. 1422-1434
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Tidskriftsartikel (refereegranskat)abstract
- Extremely acidophilic microorganisms (optimum growth pH of ≤3) maintain a near neutral cytoplasmic pH via several homeostatic mechanisms, including an inside positive membrane potential created by potassium ions. Transcriptomic responses to pH stress in the thermoacidophilic archaeon, Sulfolobus acidocaldarius were investigated by growing cells without added sodium and/or potassium ions at both optimal and sub-optimal pH. Culturing the cells in the absence of added sodium or potassium ions resulted in a reduced growth rate compared to full-salt conditions as well as 43 and 75 significantly different RNA transcript ratios, respectively. Differentially expressed RNA transcripts during growth in the absence of added sodium ions included genes coding for permeases, a sodium/proline transporter and electron transport proteins. In contrast, culturing without added potassium ions resulted in higher RNA transcripts for similar genes as a lack of sodium ions plus genes related to spermidine that has a general role in response to stress and a decarboxylase that potentially consumes protons. The greatest RNA transcript response occurred when S. acidocaldarius cells were grown in the absence of potassium and/or sodium at a sub-optimal pH. These adaptations included those listed above plus osmoregulated glucans and mechanosensitive channels that have previously been shown to respond to osmotic stress. In addition, data analyses revealed two co-expressed IclR family transcriptional regulator genes with a previously unknown role in the S. acidocaldarius pH stress response. Our study provides additional evidence towards the importance of potassium in acidophile growth at acidic pH.
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| 3. |
- Bukowska-Faniband, Ewa, et al.
(författare)
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The PASTA domain of penicillin-binding protein SpoVD is dispensable for endospore cortex peptidoglycan assembly in Bacillus subtilis.
- 2015
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Ingår i: Microbiology. - : Microbiology Society. - 1465-2080 .- 1350-0872. ; 161:Online 6 January, 2014, s. 330-340
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Tidskriftsartikel (refereegranskat)abstract
- Peptidoglycan is the major structural component of the bacterial cell wall. Penicillin-binding proteins (PBPs), located at the exterior of the cytoplasmic membrane, play a major role in peptidoglycan synthesis and remodelling. A PASTA domain (penicillin-binding protein and serine/threonine kinase associated domain) of about 65 residues is found at the C-terminal end of some PBPs and eukaryotic-like protein serine/threonine kinases in a variety of bacteria. The function of PASTA domains is not understood but some of them are thought to bind uncrosslinked peptidoglycan. Bacillus subtilis has sixteen different PBPs but only two of them, Pbp2b and SpoVD, contain a PASTA domain. SpoVD is specific for sporulation and essential for endospore cortex peptidoglycan synthesis. We have studied the role of the PASTA domain in SpoVD by deleting this domain and analyzed effects on endospore formation and subcellular localization of SpoVD. Our results demonstrate that the PASTA domain in SpoVD is not essential for cortex synthesis and not important for targeting SpoVD to the forespore outer membrane during sporulation.
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| 4. |
- Dawe, H., et al.
(författare)
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D-methionine interferes with non-typeable Haemophilus influenzae peptidoglycan synthesis during growth and biofilm formation
- 2017
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Ingår i: Microbiology-Sgm. - : Microbiology Society. - 1350-0872. ; 163:7, s. 1093-1104
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Tidskriftsartikel (refereegranskat)abstract
- Non-typeable Haemophilus influenzae (NTHi) is an opportunistic pathogen that plays a major role in a number of respiratory tract infections, including otitis media, cystic fibrosis and chronic obstructive pulmonary disease. Biofilm formation has been implicated in both NTHi colonization and disease, and is responsible for the increased tolerance of this pathogen towards antibiotic treatment. Targeting metabolic pathways that are important in NTHi biofilm formation represents a potential strategy to combat this antibiotic recalcitrance. A previous investigation demonstrated increased expression of a putative D-methionine uptake protein following exposure of NTHi biofilms to the ubiquitous signalling molecule, nitric oxide. We therefore hypothesized that treatment with exogenous D-methionine would impact on NTHi biofilm formation and increase antibiotic sensitivity. Treatment of NTHi during the process of biofilm formation resulted in a reduction in biofilm viability, increased biomass, changes in the overall biofilm architecture and the adoption of an amorphous cellular morphology. Quantitative proteomic analyses identified 124 proteins that were differentially expressed following D-methionine treatment, of which 51 (41 %) were involved in metabolic and transport processes. Nine proteins involved in peptidoglycan synthesis and cell division showed significantly increased expression. Furthermore, D-methionine treatment augmented the efficacy of azithromycin treatment and highlighted the potential of D-methionine as an adjunctive therapeutic approach for NTHi biofilm-associated infections.
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| 5. |
- Fröjd, Markus J., et al.
(författare)
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Extrusion of extracellular membrane vesicles from hyphal tips of streptomyces venezuelae coupled to cell-wall stress
- 2019
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Ingår i: Microbiology (United Kingdom). - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 165:12, s. 1295-1305
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Tidskriftsartikel (refereegranskat)abstract
- Extracellular vesicle release is a wide-spread and broadly important phenomenon in bacteria. However, not much is known about the mechanism of vesicle release in Gram-positive bacteria. Observations of polarly growing Streptomyces venezuelae by live cell time-lapse imaging reveal release of extracellular membrane vesicles from tips of vegetative hyphae. Vesicle extrusion is associated with spontaneous growth arrests, but often the apical cell survives and can re-initiate growth by forming new hyphal branches. Treatment with vancomycin to block peptidoglycan synthesis leads to a high frequency of lysis and vesicle extrusion, where some hyphae can survive growth arrest and vesicle extrusion and reinitiate growth after antibiotic is washed away. The extruded vesicles do not contain nucleoids and do not appear able to proliferate. Vesicle extrusion is not affected by the Ser/Thr protein kinase AfsK that phosphorylates the DivIVA at hyphal tips, nor is it affected by the intermediate filament-like protein FilP that localizes in gradient-like structures at hyphal tips. Notably, hyphae of a scy mutant, which has an unstable apical polarisome structure, are prone to spontaneous growth arrests and vesicle extrusion even in the absence of antibiotic treatment, supporting the idea that the nature of the growth zone at the hyphal tips is important for this route of extracellular vesicle formation. We speculate that the propensity for vesicle extrusion is a direct consequence of how polar growth is organized at hyphal tips in Streptomyces, with the cell-wall sacculus being weak and susceptible to bursting at the apical zones of growth where peptidoglycan synthesis is primarily taking place.
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| 6. |
- Kalantari, Aida, 1986, et al.
(författare)
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Serine/threonine/tyrosine phosphorylation regulates DNA binding of bacterial transcriptional regulators
- 2015
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 161:9, s. 1720-1729
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Forskningsöversikt (refereegranskat)abstract
- Reversible phosphorylation of bacterial transcriptional regulators (TRs) belonging to the family of two-component systems (TCSs) is a well-established mechanism for regulating gene expression. Recent evidence points to the fact that reversible phosphorylation of bacterial TRs on other types of residue, i.e. serine, threonine, tyrosine and cysteine, is also quite common. The phosphorylation of the ester type (phospho-serine/threonine/tyrosine) is more stable than the aspartate phosphorylation of TCSs. The kinases which catalyse these phosphorylation events (Hanks-type serine/threonine protein kinases and bacterial protein tyrosine kinases) are also much more promiscuous than the TCS kinases, i.e. each of them can phosphorylate several substrate proteins. As a consequence, the dynamics and topology of the signal transduction networks depending on these kinases differ significantly from the TCSs. Here, we present an overview of different classes of bacterial TR phosphorylated and regulated by serine/threonine and tyrosine kinases. Particular attention is given to examples when serine/threonine and tyrosine kinases interact with TCSs, phosphorylating either the histidine kinases or the response regulators. We argue that these promiscuous kinases connect several signal transduction pathways and serve the role of signal integration.
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| 7. |
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| 8. |
- Patterson, Elaine, et al.
(författare)
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Streptozotocin-induced type-1-diabetes disease onset in Sprague-Dawley rats is associated with an altered intestinal microbiota composition and decreased diversity
- 2015
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Ingår i: Microbiology. - London, UK : The Microbiology Society. - 1350-0872 .- 1465-2080. ; 161:Pt 1, s. 182-93
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing appreciation that microbiota composition can significantly affect host health and play a role in disease onset and progression. This study assessed the impact of streptozotocin (STZ)-induced type-1-diabetes (T1D) on intestinal microbiota composition and diversity in Sprague-Dawley rats, compared with healthy controls over time. T1D was induced by injection of a single dose (60 mg STZ kg(-1)) of STZ, administered via the intraperitoneal cavity. Total DNA was isolated from faecal pellets at weeks 0 (pre-STZ injection), 1, 2 and 4 and from caecal content at week 5 from both healthy and T1D groups. High-throughput 16S rRNA sequencing was employed to investigate intestinal microbiota composition. The data revealed that although intestinal microbiota composition between the groups was similar at week 0, a dramatic impact of T1D development on the microbiota was apparent post-STZ injection and for up to 5 weeks. Most notably, T1D onset was associated with a shift in the Bacteroidetes : Firmicutes ratio (P<0.05), while at the genus level, increased proportions of lactic acid producing bacteria such as Lactobacillus and Bifidobacterium were associated with the later stages of T1D progression (P<0.05). Coincidently, T1D increased caecal lactate levels (P<0.05). Microbial diversity was also reduced following T1D (P<0.05). Principle co-ordinate analyses demonstrated temporal clustering in T1D and control groups with distinct separation between groups. The results provide a comprehensive account of how T1D is associated with an altered intestinal microbiota composition and reduced microbial diversity over time.
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| 9. |
- Svensson, Lisbeth, et al.
(författare)
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Group G streptococci mediate fibrinogendependent platelet aggregation leading to transient entrapment in platelet aggregates
- 2016
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 162:1, s. 117-126
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Tidskriftsartikel (refereegranskat)abstract
- Platelets have been reported to become activated in response to bacteria and this is proposed to contribute to the acute response to bacterial infection. In the present study, we investigated platelet aggregation in response to group G streptococci (GGS) in vitro in healthy human donors and in vivo in a mouse model of streptococcal sepsis. Platelet aggregation by GGS was dependent on the bacterial surface protein FOG and engagement of the platelet fibrinogen receptor; however, it was independent of IgG and the platelet Fc receptor. Platelets exerted no antibacterial effects on the bacteria, and aggregates formed were markedly unstable, allowing bacteria to rapidly return to the plasma and grow post-aggregation. Thrombocytopenia and platelet activation occurred during invasive infection with GGS, and platelets were demonstrated to contribute to bacterial dissemination during infection. These findings reveal an important role for bacteria–platelet interactions during the pathogenesis of streptococcal infection.
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| 10. |
- Tiensuu, Teresa, et al.
(författare)
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Flick of a switch : regulatory mechanisms allowing Listeria monocytogenes to transition from a saprophyte to a killer
- 2019
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Ingår i: Microbiology. - : MICROBIOLOGY SOC. - 1350-0872 .- 1465-2080. ; 165:8, s. 819-833
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Forskningsöversikt (refereegranskat)abstract
- In contrast to obligate intracellular pathogens that can remain in relatively stable host-associated environments, the soil-living bacterial pathogen Listeria monocytogenes has to sense and respond to physical and chemical cues in a variety of quite different niches. In particular, the bacterium has to survive the dramatic transition from its saprophytic existence to life within the host where nutritional stress, increased temperature, acidity, osmotic stress and the host defences present a new and challenging landscape. This review focuses on the sB and PrfA regulatory systems used by L. monocytogenes to sense the changing environment and implement survival mechanisms that help to overcome the disparate conditions within the host, but also to switch from a harmless saprophyte to an impressively effective pathogen.
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