Research in microbiology最新文献

Background: Anthrax outbreaks continue to be reported from several districts of Karnataka in India. Many outbreaks in livestock and humans have reported, the soil and climatic conditions would have supported long-term spore persistence. Hence, the state of Karnataka in India was chosen as an initial pilot site to study, isolate, and characterize Bacillus anthracis. In this study, we integrate molecular typing and soil analysis across endemic and non-endemic areas, an approach that has been scarcely explored and could be a novel contribution. By comparing both endemic and non-endemic regions, it would be an opportunity to examine soil-related ecological factors that could have been linked to the anthrax outbreaks. A total of 45 suspected animal anthrax cases were investigated using culture and PCR-based methods. Colonies with Medusa head-like appearance on blood agar plates were subjected to PCR assays targeting protective antigen (pXO1), capsular gene (pXO2), and the chromosomal rpoB genes. Additionally, soil samples from 12 different sites (six endemic and six non-endemic) were processed using the Ground Anthrax Bacillus Refined Isolation (GABRI) method, which was used to enhance the detection of B. anthracis spores by reducing environmental contaminants that may inhibit spore germination and growth.

Results: Out of 45 suspected animal anthrax cases, 09 isolates were confirmed as Bacillus anthracis with colony characteristics of greyish-white, frosted-glass on blood agar, further verified through PCR analysis. Phylogenetic analysis based on the rpoB gene demonstrated a close genetic relationship among these isolates, suggesting that the transmission of spores was localized and likely facilitated by animal movement. The soil analysis showed that the endemic sites had an alkaline pH of 7.81-8.9, higher organic carbon 0.45-4.36 %, elevated phosphorus 10.32 to 123.7 kg/ha, and greater clay content up to 45 % in Bellary, contributing to higher survivability and retention of spores in endemic regions. In contrast, non-endemic soil exhibited neutral to slightly acidic pH (6.1-6.85), lower phosphorus levels, and sandy clay loam texture that may limit long-term spore retention.

Conclusion: The study offers significant insights into the environmental and genetic factors contributing to the persistence of Bacillus anthracis in both endemic and non-endemic regions. The finding shows that soil plays a crucial role in the survival and transmission of anthrax spores, with higher retention observed in endemic areas. The close genetic relationship among isolates further suggests localized transmission, likely influenced by animal movement. These results underline the need for continued surveillance and prevention strategies, especially in regions with a history of anthrax outbreaks.

Bacillus anthracis, a rod-shaped, spore-forming bacterium, is the causative agent of anthrax. The life cycle of B. anthracis involves sporulation and germination processes that are precisely regulated by distinct sigma factors and associated proteins. Its pathogenicity is primarily attributed to a tripartite toxin consisting of lethal factor (LF), edema factor (EF) and protective antigen (PA), as well as an antiphagocytic capsule of Poly-γ-D-Glutamate. The virulence of B. anthracis is further regulated by various post-translational modifications (PTMs), including protein phosphorylation, acetylation, glycosylation, hydroxylation, and lipidation. These modifications play a key role in modulating bacterial virulence by influencing enzymatic activity and protein expression. This review summarizes the role of PTMs in the regulation of B. anthracis virulence. A deeper understanding of how these PTMs contribute to B. anthracis pathogenesis may offer new insights into novel enzyme targets, strategies to disrupt toxin production and the development of therapeutic approaches to combat anthrax infections.

Methods for assembly and annotation of whole genomic sequences were compared for six strains of avian pathogenic Escherichia coli (APEC). Two vertically transferred E. coli clones, represented by three isolates all belonging to pulse field genome electrophoresis (PFGE) type 65- sequence type (ST)95 and three isolates belonging to PFGE type 47- ST131, were selected for Illumina short read sequencing. There was no significant difference between SPAdes and CLC Genomic Workbench for benchmark parameters to assemble the short reads. The six strains were also sequenced by long read sequencing (Nanopore) and these reads were hybrid assembled with the short reads. Unicycler provided a lower number of contigs and higher NG50 compared to Flye. No significant differences between total length of genomes were obtained from the four assemblers. At least 2.1 and 0.9 % of coding gene sequences (CDSs) annotated with Rapid annotations using subsystems technology (RAST) and PROKKA, respectively were wrongly annotated. The errors were most often associated to CDS of shorter length (<150 nt) with functions such as transposases, mobile genetic elements or being hypothetical. The investigation points out the importance of controlling automatic annotations and suggest further work to improve annotations in strains not belonging to the K12 or B lineages.

Listeria monocytogenes is primarily a saprophytic bacterium, but it can transition into a pathogenic form when ingested by humans, vertebrates, or invertebrates, thereby initiating infection and proliferating within the host. This bacterium serves as a model for studying the molecular and cellular mechanisms by which environmental microorganisms adapt to mammalian and other host systems, thereby promoting the successful colonization and survival of these microorganisms. Environmental contamination is a significant factor in the transmission of listeriosis and other foodborne diseases. This review provides a comprehensive examination of the microbiological characteristics of L. monocytogenes. It systematically evaluates host-pathogen interactions, focusing on a range of clinically relevant isolates and their pathogenic mechanisms. Furthermore, it evaluates in vitro models employed to investigate the virulence factors of the pathogen while also considering the role of animal models, including Drosophila melanogaster and other insect species, in elucidating infection dynamics. In addition, it discusses the host's innate immune response, specifically highlighting the molecular and cellular pathways activated upon infection, thereby providing a comprehensive understanding of the pathogen's interactions with the host's immune system.

Phages are bacterial viruses considered as therapeutics for treatment of serious infections with antibiotic-resistant pathogens. In Staphylococcus aureus, resistance to cell wall targeting antibiotics is common in the methicillin resistant (MRSA) or vancomycin-intermediate susceptible (VISA) strains. Furthermore, the cell wall anchors the primary phage receptor, the wall teichoic acid (WTA) glycopolymers. Here we demonstrate that mutations resulting in VISA development affect phage susceptibility of clinically and laboratory evolved strains. For clinical strains we observed both increased and decreased susceptibility compared to the ancestral vancomycin susceptible strains when infected with the therapeutically relevant myoviruses, ΦIPLA-RODI, Stab20, Stab21 and ΦK. For laboratory strains adapted to vancomycin from the MRSA strain, JE2, we observed variable resistance development to the phages ΦIPLA-RODI, Stab21 and ΦK with one strain becoming completely phage resistant. In contrast, half of the VISA strains became susceptible to Stab20 to which JE2 is resistant. These changes in part correlated with altered WTA glycosylation patterns as shown by WTA-specific antibodies and for the resistant strain resulted in compromised phage therapy as shown in a Galleria mellonella infection model. This study highlights the need for understanding antibiotic-driven alterations in bacterial physiology when developing phage-based therapies using combination treatments with antibiotics and phages.

The asexual reproduction cycle of the cheese-ripening fungus Penicillium camemberti is typical for a filamentous ascomycete fungus. It involves the production of conidia by successive mitotic divisions from specialized cells called conidiophores. Conidia are used for inoculating the fungus onto French soft cheeses and are produced industrially by submerged fermentation. However, the impact of mycelium macromorphology on conidial production for this type of fermentation has been little investigated. By studying the physiological effect of different sources and concentrations of carbohydrates at the laboratory scale, it was observed that the fungus takes on different morphologies associated with varying ability to produce conidia. Especially, a dispersed morphology was not always associated with production of conidia. Through RNA-seq transcriptomic analyses, we followed the expression profiles of P. camemberti genes during the time course of liquid cultures made in the presence of two concentrations of glucose, one of sucrose and one with a mix of glucose and fructose, which are conditions for which P. camemberti presents varying morphologies and efficiencies to produce conidia. This led to confirm that, like other ascomycetes, P. camemberti likely uses the conidiation pathway first described in the model fungus Aspergillus nidulans. It also enabled the identification of a potential conidiation-inhibiting transcription factor, specific to Eurotiales and only upregulated in conditions without conidia production. Functional studies of its ortholog in A. nidulans, for which the conidiation pathway has been extensively studied, should allow to verify whether this factor indeed plays a role in the asexual cycle.

Cyclic di-guanosine monophosphate (c-di-GMP), a bacterial second messenger, regulates diverse key processes including virulence, biofilm formation, and motility. Its synthesis involves diguanylate cyclases (DGCs) with GGDEF domains, while degradation is mediated by phosphodiesterases (PDEs) containing EAL or HD-GYP domains. This study examines the role of GefC (VP0486), a GGDEF domain protein in Vibrio parahaemolyticus, in c-di-GMP signaling, biofilm dynamics, motility, and virulence. Deletion of gefC markedly reduced cellular c-di-GMP, impaired biofilm formation, and reduced matrix components (exopolysaccharides, extracellular proteins, and extracellular DNA). Conversely, the ΔgefC mutant exhibited enhanced swimming motility and increased cytotoxicity and hemolytic activity, while zebrafish infection assays revealed attenuated lethality. Transcriptional analysis showed GefC differentially regulates EPS-related gene (cpsA), polar flagellar gene (flgM), type III secretion system 1 (vopN and vp1687), type VI secretion system 2 (hcp2, vpa1043, and vpa1044), and the TDH-encoding tdh2. Genetic evidence confirmed vp0485 and gefC form an operon. These findings establish GefC as a critical regulator of c-di-GMP-dependent biofilm development, motility, and virulence in V. parahaemolyticus, highlighting its multifaceted role in pathogenicity.