Characterization of quorum sensing system in Clostridium chauvoei

Regulatory and innovative mechanisms of bacterial quorum sensing-mediated pathogenicity: a review

Quorum sensing (QS) is a system of bacteria in which cells communicate with each other; it is linked to cell density in the microbiome. The high-density colony population can provide enough small molecular signals to enable a range of cellular activities, gene expression, pathogenicity, and antibiotic resistance that cause damage to the hosts. QS is the basis of chronic illnesses in human due to microbial sporulation, expression of virulence factors, biofilm formation, secretion of enzymes, or production of membrane vesicles. The transfer of antimicrobial resistance gene (ARG) among antibiotic resistance bacteria is a major public health concern. QS-mediated biofilm is a hub for ARG horizontal gene transfer. To develop innovative approach to prevent microbial pathogenesis, it is essential to understand the role of QS especially in response to environmental stressors such as exposure to antibiotics. This review provides the latest knowledge on the relationship of QS and pathogenicity and explore the novel approach to control QS via quorum quenching (QQ) using QS inhibitors (QSIs) and QQ enzymes. The state-of-the art knowledge on the role of QS and the potential of using QQ will help to overcome the threats of rapidly emerging bacterial pathogenesis.

Whole-genome sequence analysis of Clostridium chauvoei isolated from clinical case of black quarter (BQ) from India

Black quarter (BQ) is an infectious disease affecting cattle and small ruminants worldwide caused by Gram-positive anaerobic bacterium Clostridium chauvoei. In this study, a draft genome sequence of C. chauvoei NIVEDIBQ1 strain isolated from clinical case of black quarter was analyzed. Sequence analysis indicated that genome had 2653 predicted coding DNA sequences, harbored numerous genes, mobile genetic elements for pathogenesis, and virulence factors. Computational analysis revealed that strain contained 30 virulence-associated genes. An intact genomic region highly similar to the Clostridium phage was present in the genome. Presence of CRISPR systems and the transposon components likely contribute to the genome plasticity. Strain encode diverse spectrum of degradative carbohydrate-active enzymes (CAZymes). Comparative SNP analysis revealed that the genomes of the C. chauvoei strains analyzed were highly conserved. Phylogenetic analysis of strains and available genome (n = 21) based on whole-genome multi-locus sequence typing (wgMLST) and core orthologous genes showed the clustering of strains into two different clusters suggesting geographical links.

Development and utilization of peptide-based quorum sensing modulators in Gram-positive bacteria

Quorum sensing (QS) is a mechanism by which bacteria regulate cell density-dependent group behaviors. Gram-positive bacteria generally rely on auto-inducing peptide (AIP)-based QS signaling to regulate their group behaviors. To develop synthetic modulators of these behaviors, the natural peptide needs to be identified and its structure-activity relationships (SARs) with its cognate receptor (either membrane-bound or cytosolic) need to be understood. SAR information allows for the rational design of peptides or peptide mimics with enhanced characteristics, which in turn can be utilized in studies to understand species-specific QS mechanisms and as lead scaffolds for the development of therapeutic candidates that target QS. In this review, we discuss recent work associated with the approaches used towards forwarding each of these steps in Gram-positive bacteria, with a focus on species that have received less attention.

Autoinducer-2-mediated quorum sensing partially regulates the toxic shock response of anaerobic digestion

This study discovered a strong correlation between the autoinducer-2 (AI-2)-mediated quorum sensing (QS) with the performance of a submerged anaerobic membrane bioreactor during its recovery from a pentachlorophenol (PCP) shock: a decrease in AI-2 levels coincided with a reduction in volatile fatty acid concentrations, and corresponded significantly to a decrease in the relative abundance of Firmicutes, and to an increase in the relative abundance of Bacteroidetes and Synergistetes. Further batch experiments with the addition of an AI-2-regulating Escherichia coli mutant culture showed that a reduction in AI-2 levels resulted in the highest biogas production rate during a PCP shock. In contrast, an increase in AI-2 levels via addition of the E. coli wild type strain or an AI-2 precursor showed no obvious effects on biogas production. These results suggest that the AI-2 level in anaerobic sludge was governed primarily by Firmicutes, and the AI-2-mediated QS partially regulates the toxic shock response of anaerobic sludge via tuning the activities of Firmicutes and Synergistetes. A decrease in the AI-2 level might reduce acetogenesis and favor hydrogenotrophic methanogenesis, thus resulting in less VFA accumulation and higher methane production during the PCP shock. This study is the first of this type that exploits the role of quorum sensing in the toxic shock response of anaerobic sludge; it demonstrates a novel approach to shortening the recovery period of anaerobic processes via manipulating the AI-2-mediated QS.