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- Mycobacterium tuberculosis PE_PGRS45 (Rv2615c) Promotes Recombinant Mycobacteria Intracellular Survival via Regulation of Innate Immunity, and Inhibition of Cell Apoptosis
- Tao Xu , Chutong Wang , Minying Li , Jing Wei , Zixuan He , Zhongqing Qian , Xiaojing Wang , Hongtao Wang
- J. Microbiol. 2024;62(1):49-62. Published online February 9, 2024
- DOI: https://doi.org/10.1007/s12275-023-00101-0
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Abstract
- Tuberculosis (TB), a bacterial infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), is a significant global public health problem. Mycobacterium tuberculosis expresses a unique family of PE_PGRS proteins that have been implicated in pathogenesis. Despite numerous studies, the functions of most PE_PGRS proteins in the pathogenesis of mycobacterium infections remain unclear. PE_PGRS45 (Rv2615c) is only found in pathogenic mycobacteria. In this study, we successfully constructed a recombinant Mycobacterium smegmatis (M. smegmatis) strain which heterologously expresses the PE_PGRS45 protein. We found that overexpression of this cell wall-associated protein enhanced bacterial viability under stress in vitro and cell survival in macrophages. MS_PE_PGRS45 decreased the secretion of pro-inflammatory cytokines such as IL-1β, IL-6, IL-12p40, and TNF-α. We also found that MS_PE_PGRS45 increased the expression of the anti-inflammatory cytokine IL-10 and altered macrophage-mediated immune responses. Furthermore, PE_PGRS45 enhanced the survival rate of M. smegmatis in macrophages by inhibiting cell apoptosis. Collectively, our findings show that PE_PGRS45 is a virulent factor actively involved in the interaction with the host macrophage.
- Adaptation of Pseudomonas helmanticensis to fat hydrolysates and SDS: fatty acid response and aggregate formation
- Ilya N. Zubkov , Anatoly P. Nepomnyshchiy , Vadim D. Kondratyev , Pavel N. Sorokoumov , Konstantin V. Sivak , Edward S. Ramsay , Sergey M. Shishlyannikov
- J. Microbiol. 2021;59(12):1104-1111. Published online October 26, 2021
- DOI: https://doi.org/10.1007/s12275-021-1214-5
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- 3 Citations
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Abstract
- An essential part of designing any biotechnological process is examination of the physiological state of producer cells in different phases of cultivation. The main marker of a bacterial cell’s state is its fatty acid (FA) profile, reflecting membrane lipid composition. Consideration of FA composition enables assessment of bacterial responses to cultivation conditions and helps biotechnologists understand the most significant factors impacting cellular metabolism. In this work, soil SDS-degrading Pseudomonas helmanticensis was studied at the fatty acid profile level, including analysis of rearrangement between planktonic and aggregated forms. The set of substrates included fat hydrolysates, SDS, and their mixtures with glucose. Such media are useful in bioplastic production since they can help incrementally lower overall costs. Conventional gas chromatography-mass spectrometry was used for FA analysis. Acridine orange-stained aggregates were observed by epifluorescence microscopy. The bacterium was shown to change fatty acid composition in the presence of hydrolyzed fats or SDS. These changes seem to be driven by the depletion of metabolizable substrates in the culture medium. Cell aggregation has also been found to be a defense strategy, particularly with anionic surfactant (SDS) exposure. It was shown that simple fluidity indices (such as saturated/ unsaturated FA ratios) do not always sufficiently characterize a cell's physiological state, and morphological examination is essential in cases where complex carbon sources are used.
- The small RNA RsaF regulates the expression of secreted virulence factors in Staphylococcus aureus Newman
- Niralee Patel , Mrinalini Nair
- J. Microbiol. 2021;59(10):920-930. Published online September 23, 2021
- DOI: https://doi.org/10.1007/s12275-021-1205-6
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- 3 Citations
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Abstract
- The pathogenesis of Staphylococcus aureus, from local infections to systemic dissemination, is mediated by a battery of virulence factors that are regulated by intricate mechanisms, which include regulatory proteins and small RNAs (sRNAs) as key regulatory molecules. We have investigated the involvement of sRNA RsaF, in the regulation of pathogenicity genes hyaluronate lyase (hysA) and serine proteaselike protein D (splD), by employing S. aureus strains with disruption and overexpression of rsaF. Staphylococcus aureus strain with disruption of rsaF exhibited marked down-regulation of hysA transcripts by 0.2 to 0.0002 fold, and hyaluronate lyase activity by 0.2–0.1 fold, as well as increased biofilm formation, during growth from log phase to stationery phase. These mutants also displayed down-regulation of splD transcripts by 0.8 to 0.005 fold, and reduced activity of multiple proteases by zymography. Conversely, overexpression of rsaF resulted in a 2- to 4- fold increase in hysA mRNA levels and hyaluronidase activity. Both hysA and splD mRNAs demonstrated an increased stability in RsaF+ strains. In silico RNA-RNA interaction indicated a direct base pairing of RsaF with hysA and splD mRNAs, which was established in electrophoretic mobility shift assays. The findings demonstrate a positive regulatory role for small RNA RsaF in the expression of the virulence factors, HysA and SplD.
- The inner membrane protein LapB is required for adaptation to cold stress in an LpxC-independent manner
- Han Byeol Lee , Si Hyoung Park , Chang-Ro Lee
- J. Microbiol. 2021;59(7):666-674. Published online May 15, 2021
- DOI: https://doi.org/10.1007/s12275-021-1130-8
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- 10 Citations
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Abstract
- The inner membrane protein lipopolysaccharide assembly
protein B (LapB) is an adaptor protein that activates the proteolysis
of LpxC by an essential inner membrane metalloprotease,
FtsH, leading to a decrease in the level of lipopolysaccharide
in the membrane. In this study, we revealed the
mechanism by which the essential inner membrane protein
YejM regulates LapB and analyzed the role of the transmembrane
domain of LapB in Escherichia coli. The transmembrane
domain of YejM genetically and physically interacted with
LapB and inhibited its function, which led to the accumulation
of LpxC. The transmembrane domain of LapB was indispensable
for both its physical interaction with YejM and
its regulation of LpxC proteolysis. Notably, we found that the
lapB mutant exhibited strong cold sensitivity and this phenotype
was not associated with increased accumulation of LpxC.
The transmembrane domain of LapB was also required for
its role in adaptation to cold stress. Taken together, these
results
showed that LapB plays an important role in both the regulation of LpxC level, which is controlled by its interaction with the transmembrane domain of YejM, and adaptation to cold stress, which is independent of LpxC.
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