Research in microbiology最新文献

Phytophthora sojae, one of the most devastating Oomycete pathogens, causes severe diseases that lead to economic loss in the soybean industry. The production of zoospores play a crucial role during the development of Phytophthora disease. In this work, CRISPR/Cas9 genome editing technology were used to obtain protein kinase A regulatory subunit (PsPkaR) knockout mutants. The role of PsPkaR in the production of zoospores and pathogenicity of P. sojae was analyzed. The overall findings indicate that PsPkaR is involved in regulating the growth process of P. sojae, primarily affecting the hyphal morphology and growth rate. Additionally, PsPkaR participates in the regulation of the release process of zoospores. Specifically, knocking-out PsPkaR resulted in incomplete cytoplasmic differentiation and uneven protoplast division, leading to abnormal release of zoospores. Furthermore, when the PsPkaR knockout mutants were inoculated on soybean leaves, the pathogenicity was significantly reduced compared to that of the wild-type and control strains. These findings of this study provide important clues and evidence regarding the role of the cAMP-PKA signaling pathway in the interaction between P. sojae and its host. This work contributes to a better understanding of the pathogenic mechanism of P. sojae and the development of corresponding prevention and control strategies.

S. lividans and S. coelicolor are phylogenetically closely related strains with different abilities to produce the same specialized metabolites. Previous studies revealed that the strong antibiotic producer, S. coelicolor, had a lower ability to assimilate nitrogen and phosphate than the weak producer, Streptomyces lividans, and this resulted into a lower growth rate. A comparative proteomic dataset was used to establish the consequences of these nutritional stresses on the abundance of proteins of the translational apparatus of these strains, grown in low and high phosphate availability. Our study revealed that most proteins of the translational apparatus were less abundant in S. coelicolor than in S. lividans whereas it was the opposite for ET-Tu 3 and a TrmA-like methyltransferase. The expression of the latter being known to be under the positive control of the stringent response whereas that of the other ribosomal proteins is under its negative control, this indicated the occurrence of a strong activation of the stringent response in S. coelicolor. Furthermore, in S. lividans, ribosomal proteins were more abundant in phosphate proficiency than in phosphate limitation suggesting that a limitation in phosphate, that was also shown to trigger RelA expression, contributes to the induction of the stringent response.

Vibrio cholerae can form biofilms in the aquatic environment and in the human intestine, facilitating the release of hyper-infectious aggregates. Due to the increasing antibiotic resistance, alternatives need to be found. One of these alternatives is antimicrobial peptides, including polymyxin B (PmB). In this study, we first investigated the resistance of V. cholerae O1 El Tor strain A1552 to various antimicrobials under aerobic and anaerobic conditions. An increased resistance to PmB is observed in anaerobiosis, with a 3-fold increase in the dose required for 50 % growth inhibition. We then studied the impact of the PmB on the formation and the degradation of V. cholerae biofilms to PmB. Our results show that PmB affects more efficiently biofilm formation under anaerobic conditions. On the other hand, preformed biofilms are susceptible to degradation by PmB at concentrations close to the minimal inhibitory concentration. At higher concentrations, we observe an opacification of the biofilm structures within 20 min post-treatment, suggesting a densification of the structure. This densification does not seem to result from the overexpression of matrix genes but rather from DNA release through massive cell lysis, likely forming a protective shield that limits the penetration of the PmB into the biofilm.

Enterococcus faecalis is a Gram-positive clinical pathogen causing severe infections. Its survival during infection depends on its ability to utilize host-derived metabolites, such as protein-deglycosylation products. We have identified in E. faecalis OG1RF a locus (ega) involved in the catabolism of the glycoamino acid N-acetylglucosamine-L-asparagine. This locus is separated into two transcription units, genes egaRP and egaGBCD1D2, respectively. RT-qPCR experiments revealed that the expression of the ega locus is regulated by the transcriptional repressor EgaR. Electromobility shift assays evidenced that N-acetylglucosamine-L-asparagine interacts directly with the EgaR protein, which leads to the transcription of the ega genes. Growth studies with egaG, egaB and egaC mutants confirmed that the encoded proteins are necessary for N-acetylglucosamine-L-asparagine catabolism. This glycoamino acid is transported and phosphorylated by a specific phosphotransferase system EIIABC components (OG1RF_10751, EgaB, EgaC) and subsequently hydrolyzed by the glycosylasparaginase EgaG, which generates aspartate and 6-P-N-acetyl-β-d-glucosaminylamine. The latter can be used as a fermentable carbon source by E. faecalis. Moreover, Galleria mellonella larvae had a significantly higher survival rate when infected with ega mutants compared to the wild-type strain, suggesting that the loss of N-acetylglucosamine-L-asparagine utilization affects enterococcal virulence.

In this study, CRISPR/Cas9 genome editing was used to knockout the bgl2 gene encoding intracellular β-glucosidase filamentous fungus Penicillium verruculosum. This resulted in a dramatic reduction of secretion of cellulolytic enzymes. The study of P. verruculosum Δbgl2 found that the transcription of the cbh1 gene, which encodes cellobiohydrolase 1, was impaired when induced by cellobiose and cellotriose. However, the transcription of the cbh1 gene remains at level of the host strain when induced by gentiobiose. This implies that gentiobiose is the true inducer of the cellulolytic response in P. verruculosum, in contrast to Neurospora crassa where cellobiose acts as an inducer.

The COVID-19 pandemic has highlighted our reliance on biocides, the increasing prevalence of resistance to biocides is a risk to public health. Bacterial exposure to the biocide, benzalkonium chloride (BAC), resulted in a unique transcriptomic profile, characterised by both a short and long-term response. Differential gene expression was observed in four main areas: motility, membrane composition, proteostasis, and the stress response. A metabolism shift to protect the proteome and the stress response were prioritised suggesting these are main resistance mechanisms. Whereas “well-established” mechanisms, such as biofilm formation, were not found to be differentially expressed after exposure to BAC.

Nocardiopsis dassonvillei prevails under harsh environmental conditions and the purpose of this review is to highlight its biological features and recent biotechnological applications. The organism prevails in salt-rich soils/marine systems and some strains endure extreme temperatures and pH. A few isolates are associated with marine organisms and others cause human diseases. Comparative genomic analysis indicates its versatility in producing biotechnologically relevant metabolites. Antimicrobial, cytotoxic, anticancer and growth promoting biomolecules are obtained from this organism. It also synthesizes biotechnologically important enzymes. Bioactive compounds and enzymes obtained from this actinomycete provide evidence regarding its metabolic competence and its potential economic value.

Medical students could be a potential source of Staphylococcus aureus transmission to patients. This cross-sectional study involved samples collected from both nasal nostrils. Samples were processed for S. aureus recovery; the antimicrobial resistance (AMR) phenotype was determined by disc diffusion assays and the spa types and AMR genotypes by PCR/sequencing. A structured questionnaire was administered to students to collate data related to potential risk factors of nasal colonization. Ninety-eight students were included, 50 % were colonized by S. aureus and 12.2 % by MRSA. The mecA gene was detected in all MRSA isolates. The MSSA-CC398-IEC-type C lineage was found among 16.3 % of nasal carriers, of which t571 was the predominant spa-type. MRSA isolates were ascribed to spa types t2226 (CC5, 12 isolates) and t3444 (new spa type, 1 isolate). All MRSA were multi-drug resistant and MSSA were predominantly resistant to erythromycin-clindamycin (inducible-type, mediated by ermT gene). High rates of S. aureus and MRSA nasal carriages were observed in this study. The predominance of the CC398 lineage among MSSA (emergent invasive lineage) represent a relevant finding of public health concern. The role of medical students as potential source of MRSA and MSSA-CC398 transmissions in hospital and community needs to be elucidated in detail.

This review summarizes the literature on efficacy of techniques to sterilize soil. Soil may need to be sterilized if contaminated with pathogens such as Bacillus anthracis. Sterilizing soil in-situ minimizes spread of the bio-contaminant. Soil is difficult to sterilize, with efficacy generally diminishing with depth. Methyl bromide, formaldehyde, and glutaraldehyde are the only soil treatment options that have been demonstrated at full-scale to effectively inactivate Bacillus spores. Soil sterilization modalities with high efficacy at bench-scale include wet and dry heat, metam sodium, chlorine dioxide gas, and activated sodium persulfate. Simple oxidants such as chlorine bleach are ineffective in sterilizing soil.

Proteus mirabilis is known to cause Catheter-associated urinary tract infections (CAUTIs), which exhibit virulence factors linked to forming biofilms. Aptamers have recently been explored as potential anti-biofilm agents. This study demonstrates the anti-biofilm activity of aptamer (PmA2G02) targeting P. mirabilis 1429^T, a pathogenic bacteria known to cause Catheter-associated urinary tract infections (CAUTIs). The studied aptamer inhibited biofilm formation, swarming motility, and cell viability at a concentration of 3 μM. The study also showed that the PmA2G02 had a binding affinity towards fimbrial outer membrane usher protein (PMI1466), flagellin protein (PMI1619), and regulator of swarming behavior (rsbA), which are responsible for adhesion, motility, and quorum sensing, respectively. Crystal violet assay, SEM, and confocal imaging confirmed the effectiveness of the PmA2G02 as an anti-biofilm agent. Moreover, as verified by qPCR, the expression levels of fimD, fliC2, and rsbA were significantly reduced compared to the untreated group. This study suggests that aptamer may be a potential alternative to traditional antibiotics for the treatment of CAUTIs caused by P. mirabilis. These findings shed light on the mechanisms by which the aptamer inhibits biofilm formation.