Fems Microbiology Letters最新文献

Adaptation to environmental change during both colonization and infection is essential to the pathogenesis of Staphylococcus aureus. Like other bacterial pathogens that require potassium to fulfill nutritional and chemiosmotic requirements, S. aureus has been shown to utilize potassium transport to modulate virulence gene expression, antimicrobial resistance, and osmotic tolerance. Recent studies examining the role for potassium uptake in mediating S. aureus physiology have also described its contribution in mediating carbon flux within central metabolism and generation of a proton motive force. Here, we utilize a pH-sensitive green fluorescent protein to examine the temporal regulation of S. aureus intracellular pH by potassium and sodium under various environmental conditions, including extracellular pH and antibiotic stress. Our results distinguish unique conditions and transport mechanisms that utilize these ions to modulate cytoplasmic pH homeostasis, and they identify these processes as a novel mechanism of intrinsic ampicillin resistance in S. aureus.

In this study, we developed a mycelial dispersion strain by disrupting the pkac2 gene in the white-rot fungus Pleurotus ostreatus. pkac2 is a catalytic subunit gene of protein kinase A, which regulates several transcription factors related to cell wall synthesis. Liquid cultures of the Δpkac2 strains showed very high mycelial dispersibility and were visibly different from the wild-type strain (WT). Although growth on agar medium was slower than that of WT, Δpkac2 strains grew faster in liquid culture and had approximately twice the mycelial dry weight of WT after 5 d of culture. Microscopic observations showed that the cell walls of the Δpkac2 strains were thinner compared to WT. The β-glucan content in the cell walls decreased in the pkac2 disruptants, although the transcription levels of β-glucan synthase genes increased. Furthermore, the Δpkac2 strains showed decreased hydrophobicity and stress tolerance compared to WT. These results indicate that disruption of the pkac2 gene in P. ostreatus alters the structure of the cell wall surface layer, resulting in high-density cultures due to mycelial dispersion.

Divulsuperbac (DSB) is an outreach project involving a Service-Learning component aimed at the educational community. Launched in 2019, it has involved Biology degree students in a Microbiology-focused initiative within the Valencian Community (Spain) for four academic years. The DSB project includes various outreach activities designed to raise awareness of the threat posed by superbugs among pre-university students. Under the supervision of their professors, university students created an exhibition featuring 14 infographics on antimicrobial resistance. These infographics were presented at 23 high schools (HS), where university students explained the issue to HS students (aged 15-16) and assessed their understanding of the topic. The activity was supported by HS teachers. Surveys indicated scores of around 4 out of 5 in terms of overall scientific interest and knowledge gained about antibiotic resistance. These positive results have inspired us to expand the project to other regions of the world.

Streptomyces rochei is a species of Streptomyces with a diverse range of biological activities. S. rochei strain A144 was isolated from desert soils and exhibits antagonistic activity against several plant pathogenic fungi. The genome of S. rochei A144 was sequenced and revealed the presence of one linear chromosome and one plasmid. The chromosome length was found to be 8,085,429 bp, with a GC content of 72.62%, while the Plas1 length was 177,399 bp, with a GC content of 69.08%. Comparative genomics was employed to analyse the S. rochei group. There is a high degree of collinearity between the genomes of S. rochei strains. Based on pan-genome analysis, S. rochei has 10,315 gene families, including 4051 core and 2322 unique genes. AntiSMASH was used to identify the gene clusters for secondary metabolites, identifying 33 secondary metabolite genes on the A144 genome. Among them, 18 clusters were found to be >70% identical to known biosynthetic gene clusters (BGCs), indicating that A144 has the potential to synthesize secondary metabolites. The majority of the BGCs were found to be conserved within the S. rochei group, including those encoding polyketide synthases (PKS), terpenes, non-ribosomal peptide synthetases (NRPS), other ribosomally synthesised and post-translationally modified peptides (RiPP), nicotianamine-iron transporters, lanthipeptides, and a few other types. The S. rochei group can be a potential genetic source of useful secondary metabolites with applications in medicine and biotechnology.

Menaquinone (MK) is an important electron transporter in Escherichia coli. This isoprenoid quinone can transfer electrons to many terminal acceptors, such as fumarate and nitrate, which helps this organism survive under diverse and challenging conditions. As the isoprenoid quinones with various length of isoprenyl tail are widely distributed in nature, the heterologous expression of polyprenyl diphosphate synthases (PDSs) has been investigated using its counterpart, ubiquinone (UQ). In this study, we investigated the MK production by the expression of various heterologous PDS genes from prokaryotic and eukaryotic species, including Saccharomyces cerevisiae COQ1 (hexa-PDS), Haemophilus influenzae hi0881 (hepta-PDS), Synechocystis sp. strain PCC6803 slr0611 (nona-PDS) and Glunocobacter suboxydans ddsA (deca-PDS) in E. coli. We detected specific isoforms of MK, including MK7, MK9, and MK10, via the expression of HI0881, Slr0611 and DdsA respectively, but rarely detect MK6 via the expression of Coq1. As UQ6 was detected in E. coli harboring COQ1, the acceptance of the side chain lengths by MenA (prenyl transferase for MK) was narrower than UbiA (prenyl transferase for UQ). We also identified a mutation in menA in the E. coli AN386 strain and a transposon insertion of IS186 in menC in E. coli KO229 (∆ispB) and its parental strain FS1576. Taken together, these results elucidate the different nature of MenA from UbiA.

Objective: To conduct an origin tracking and genomic study of the Brucella strain B. melitensis bv.3 ARQ-070, with the aim of addressing the challenges posed by the highly conserved genome of Brucella to conventional typing methods and to gain an understanding of the geographic distribution and interspecies transmission of this pathogen in China.

Methods: Differentiation and genotyping were established via biochemical profiles and polymerase chain reaction (AMOS-PCR). Illumina MiSeq® was applied to sequence the Brucella isolates. Using multilocus sequence typing (MLST) multilocus sequence typing and Fisher's exact test was used for the KEGG enrichment analysis of differential genes. Differential gene protein PPI network analysis was conducted using the STRING database and visualisation was performed using.

Results: According to the final identification results of an A/M serum agglutination test. ARQ-070 was identified as the No. 3 white spirulina biological variety, and mM was identified as the No. 1 white Spirulina biological variety. The genetic information of this strain is very close to that of the M5 vaccine strain, suggesting possible vaccine-escape infection. In the comparative genomics analysis with B. melitensis bv.1 16 M, the main differences between the B. melitensis strains were found to be concentrated in the genes related to amino acid metabolism and environmental perception. A base mutation was found in the Brucella gene virB9, which is associated with the key virulence factor of the type IV secretion system (T4SS), but this mutation did not lead to changes in the protein's tertiary structure, and the strain did not lose its infectivity.

Conclusion: The study discovered a base mutation in the virB9 gene of Brucella, which is linked to T4SS but does not affect the protein's structure or the strain's infectivity. This mutation could influence public health approaches to detecting and preventing Brucella transmission. Future research aims to analyse a wider range of Brucella strains for a deeper understanding of their epidemiology.

The increasing trend of carbapenem resistance amongst Escherichia coli poses a major public health crisis and requires active surveillance of resistance mechanisms to control the threat. Quorum Sensing system plays a role in bacterial resistance to antibiotics. Quorum Sensing is a cell-cell communication system where bacteria alter their gene expression in response to specific stimuli. Here, in this study we investigated the transcriptional response of quorum sensing receptor, sdiA in E.coli under sub-inhibitory concentration of carbapenem in presence of quorum sensing signal molecules. Two E.coli isolates harbouring blaNDM were subjected to treatment with 10% SDS for 20 consecutive days of which blaNDM encoding plasmid was successfully eliminated from one isolate. Both the wild type and the cured mutant were then allowed to grow under eight different inducing conditions and the transcriptional response of sdiA gene was studied by quantitative real time PCR method. We found different response levels of sdiA in wild type and cured mutant under exogenous AHL and imipenem and when co-cultured with P.aeruginosa under imipenem stress. This study highlighted that sub-inhibitory concentration of imipenem in combination with AHL is acting as signal to SdiA, a quorum sensing receptor in E.coli.

The aim of this study was to investigate the relationship among pollutant removal performance, microbial community structure and potential gene function of immobilized microorganisms in coking wastewater (CWW) treatment process. The results showed that the immobilized biomass containing strain Comamonas sp. ZF-3 displayed greater resistance to CWW and higher COD, NH4+-N removal efficiency (92%, 60%) than free cells (48%, 7%), meanwhile, the results from GC-MS proved main organic pollutants in CWW including phenolic compounds, heterocyclic compounds and polycyclic aromatic hydrocarbons were basically removed by immobilized microorganisms. During 123 days of degradation experiment, high-throughput 16S rRNA gene sequencing analysis of immobilized carriers showed more stable and diverse microbial community, which was consistent with simultaneous removal of COD and NH4+-N observed in carrier experiment. Among them, Comamonas sp. ZF-3 continuously remained at the highest proportion (23.25%) in immobilized carrier, while Nitrosomonas (1.47%) and Nitrospira (1.90%) were simultaneously detected. Moreover, microbial community of immobilized carriers showed higher relative abundance of potential function in membrane transport and xenobiotics biodegradation and metabolism, which may indirectly displayed biodegradation activity of immobilized functional microorganisms. This work illustrated the survival status and potential gene function of immobilized microorganisms, and provided basis for practical application of immobilized carriers in CWW treatment.

Nano-picoplankton are the dominant primary producers during the post-upwelling period in St Helena Bay, South Africa. Their dynamics on short time scales are not well understood and neither are the community composition, structure, and potential functionality of the surrounding microbiome. Samples were collected over five consecutive days in March 2018 from three depths (1 m, 25 m, 50 m) at a single sampling station in St Helena Bay. There was clear depth-differentiation between the surface and depth in both diversity and function throughout the sampling period for the archaea, bacteria and eukaryotes. Daily difference in eukaryote diversity, was more pronounced at 1 m and 25 m with increased abundances of Syndiniales and Bacillariophyta. Surface waters were dominated by photosynthetic and photoheterotrophic microorganisms, while samples at depth were linked to nitrogen cycling processes, with high abundances of nitrifiers and denitrifiers. Strong depth gradients found in the nutrient transporters for ammonia were good indicators of measured uptake rates. This study showed that nano-picoplankton dynamics were driven by light availability, nutrient concentrations, carbon biomass and oxygenation. The nano-picoplankton help sustain ecosystem functioning in St Helena Bay through their ecological roles, which emphasizes the need to monitor this size fraction of the plankton.

Gut microbiome plays crucial roles in animal adaptation and evolution. However, research on adaptation and evolution of small wild high-altitude mammals from the perspective of gut microbiome is still limited. In this study, we compared difference in intestinal microbiota composition and function in Plateau pikas (Ochotona curzoniae) and Daurian pikas (Ochotona daurica) using metagenomic sequencing. Our results showed that microbial community structure had distinct differences in different pika species. Prevotella, Methanosarcina, Rhizophagus and Podoviridae were abundant bacteria, archaea, eukaryotes and viruses in Plateau pikas, respectively. However, Prevotella, Methanosarcina, Ustilago and Retroviridae were dominated in Daurian pikas. Functional pathways related to carbohydrate metabolism that refer to utilization of pectin, hemicellulose and debranching enzymes were abundant in Plateau pikas, while the function for degradation of chitin, lignin and cellulose was more concentrated in Daurian pikas. Pika gut had abundant multidrug resistance genes, followed by glycopeptide and beta-lactamase resistance genes, as well as high-risk ARGs, such as mepA, tetM and bacA. Escherichia coli and Klebsiella pneumoniae may be potential hosts of mepA. This research provided new insights for adaptation and evolution of wild animals from perspective of gut microbiome, and broadened our understanding of high-risk ARGs and potential pathogens of wild animals.