Research in microbiology最新文献

The growth-promoting and immune modulatory properties of different strains of plant growth promoting rhizobacteria (PGPR) fluorescent Pseudomonads complex (PFPC) can be explored to combat food security challenges. These PFPC prime plants through induced systemic resistance, fortify plants to overcome future pathogen-mediated vulnerability by eliciting robust systemic acquired resistance through regulation by nonexpressor of pathogenesis-related genes 1. Moreover, outer membrane vesicles released from Pseudomonas fluorescens also elicit a broad spectrum of immune responses, presenting a rapid viable alternative to whole cells. Thus, PFPC can help the host to maintain an equilibrium between growth and immunity, ultimately leads to increased crop yield.

Phytophthora species are destructive pathogens causing yield losses in different ecological systems, such as potato, black pepper, pepper, avocado, citrus, and tobacco. The diversity of plant growth-promoting microorganisms (PGPM) plays a crucial role in disease suppression. Knowledge of metagenomics approaches is essential for assessing the dynamics of PGPM and Phytophthora species across various ecosystems, facilitating effective management strategies for better crop protection. This review discusses the dynamic interplay between PGPM and Phytophthora sp. using metagenomics approaches that sheds light on the potential of PGPM strains tailored to specific crop ecosystems to bolster pathogen suppressiveness.

Listeria monocytogenes in beef receives less attention compared to other pathogens such as Salmonella and Escherichia coli. To address this gap, we conducted a literature review focusing on the presence of L. monocytogenes in beef. This review encompasses the pathogenic mechanisms, routes of contamination, prevalence rates, and the laws and regulations employed in various countries. Our findings reveal a prevalence of L. monocytogenes in beef and beef products ranging from 2.5% to 59.4%. Notably, serotype 4b was most frequently isolated in cases of beef contamination during food processing, with the skinning and evisceration stages identified as critical points of contamination.

By-products like CO₂ and organic acids, produced during Clostridium botulinum growth, appear to inhibit its development and reduce ATP production. A decrease in ATP production creates an imbalance in the ATP/GTP ratio. GTP activates CodY, which regulates BoNT expression. This toxin is released into the extracellular medium. Its light chains act as a specific endopeptidase, targeting SNARE proteins. The specific amino acids released enter the cells and are metabolized by the Stickland reaction, resulting in the synthesis of ATP. This ATP might then be used by histidine kinases to activate Spo0A, the main regulator initiating sporulation, through phosphorylation.

Despite being classified as microaerophilic microorganisms, most Campylobacter species can grow anaerobically, using formate or molecular hydrogen (H₂) as electron donors, and various nitrogenous and sulfurous compounds as electron acceptors. Herein, we showed that both l-asparagine (l-Asn) and l-aspartic acid (l-Asp) bolster H₂-driven anaerobic growth in several Campylobacter species, whereas the d-enantiomer form of both asparagine (d-Asn) and aspartic acid (d-Asp) only increased anaerobic growth in Campylobacter concisus strain 13826 and Campylobacter ureolyticus strain NCTC10941. A gene annotated as racD encoding for a putative d/l-Asp racemase was identified in the genome of both strains. Disruption of racD in Cc13826 resulted in the inability of the mutant strain to use either d-enantiomer during anaerobic growth. Hence, our results suggest that the racD gene is required for campylobacters to use either d-Asp or d-Asn. The use of d-Asp by various human opportunistic bacterial pathogens, including C. concisus, C. ureolyticus, and also possibly select strains of Campylobacter gracilis, Campylobacter rectus and Campylobacter showae, is significant, because d-Asp is an important signal molecule for both human nervous and neuroendocrine systems. To our knowledge, this is the first report of pathogens scavenging a d-amino acid essential for human health.

The continuous increase in global temperature and ultraviolet radiation (UVR) causes profound impacts on the growth and physiology of photosynthetic microorganisms. The hot-spring cyanobacteria have a wide range of mitigation mechanisms to cope up against current unsustainable environmental conditions. In the present investigation, we have explored the indispensable mitigation strategies of an isolated hot-spring cyanobacterium Nostoc sp. strain VKB02 under simulated ultraviolet (UV-A, UV-B) and photosynthetically active radiation (PAR). The adaptive morphological changes were more significantly observed under PAB (PAR, UV-A, and UV-B) exposure as compared to P and PA (PAR and UV-A) irradiations. PAB exposure also exhibited a marked decline in pigment composition and photosynthetic efficiency by multi-fold increment of free radicals. To counteract the oxidative stress, enzymatic and non-enzymatic antioxidants defense were significantly enhanced many folds under PAB exposure as compared to the control. In addition, the cyanobacterium has also produced shinorine as a strong free radicals scavenger and excellent UV absorber for effective photoprotection against UV radiation. Therefore, the hot-spring cyanobacterium Nostoc sp. strain VKB02 has unique defense strategies for survival under prolonged lethal UVR conditions. This study will help in the understanding of environment-induced defense strategies and production of highly value-added green photo-protectants for commercial applications.

The complete genome of Corynebacterium glutamicum contain a gene encoding murein endopeptidase MepA which maintain cell wall homeostasis by regulating peptidoglycan biosynthesis. In this study, we investigate the physiological function, localization and regulator of MepA. The result shows that mepA overexpression lead to peptidoglycan degradation and the defects in cell division. MepA-EGFP was shown to localizes exclusively at the cell cell septum. In addition, mepA overexpression increased cell permeability and reduced the resistance of cells to isoniazid, an antibiotic used to treat Mycobacterium tuberculosis infection. Furthermore, transcription analysis showed that mepA affected cell division and membrane transport pathways, and was coordinately regulated by the two-component systems MtrAB and MprAB(CgtS/R2).

Unlike Bacillus subtilis, Streptomyces coelicolor contains nine SigB homologues of the stress-response sigma factor SigB. By using a two-plasmid system, we previously identified promoters recognized by these sigma factors. Almost all promoters were recognized by several SigB homologues. However, no specific sequences of these promoters were found. One of these promoters, ssgBp, was selected to examine this cross-recognition in the native host. It controls the expression of the sporulation-specific gene ssgB. Using a luciferase reporter, the activity of this promoter in S. coelicolor and nine mutant strains lacking individual sigB homologous genes showed that sgBp is dependent on three sigma factors, SigH, SigN, and SigI. To determine which nucleotides in the-10 region are responsible for the selection of a specific SigB homologue, promoters mutated at the last three nucleotide positions were tested in the two-plasmid system. Some mutant promoters were specifically recognized by a distinct set of SigB homologues. Analysis of these mutant promoters in the native host showed the role of these nucleotides. A conserved nucleotide A at position 5 was essential for promoter activity, and two variable nucleotides at positions 4 and 6 were responsible for the partial selectivity of promoter recognition by SigB homologues.

Antimicrobial resistance is one of the leading causes of death worldwide and research on this topic has been on the spotlight for a long time. More recently and in agreement with the One Health Approach, the focus has moved towards the environmental resistome. Members of the phylum Planctomycetota are ubiquitously present in the environment including in hotspots for antimicrobial resistance selection and dissemination. Furthermore, phenotypic broad-range resistance has been observed in diverse members of this phylum. Here we review the evidence available on antimicrobial resistance in the underexploited Planctomycetota and highlight key aspects for future studies.