Comprehensive genomics depict accessory genes encoding pathogenicity and biofilm determinants in Enterococcus faecalis

CRISPR-Cas systems in enterococci

Enterococci are members of the microbiota of humans and other animals. They can also be found in the environment, associated with food, healthcare infections, and hospital settings. Due to their wide distribution, they are inserted in the One Health context. The selective pressure caused by the extensive use of antimicrobial agents in humans, animals, and agriculture has increased the frequency of resistance to various drugs among enterococcal species. CRISPR-Cas system, an important prokaryotic defense mechanism against the entry of mobile genetic elements, may prevent the acquisition of genes involved in antimicrobial resistance and virulence. This system has been increasingly used as a gene editing tool, which can be used as a way to recognize and inactivate genes of interest. Here, we conduct a review on CRISPR systems found in enterococci, considering their occurrence, structure and organization, mechanisms of action and use as a genetic engineering technology. Type II-A CRISPR-Cas systems were shown to be the most frequent among enterococcal species, and the orphan CRISPR2 was the most commonly found system (54.1%) among enterococcal species, especially in Enterococcus faecalis. Distribution of CRISPR systems varied among species. CRISPR systems had 1 to 20 spacers, with size between 23 and 37 bp and direct repeat sequences from 25 to 37 bp. Several applications of the CRISPR-Cas biotechnology have been described in enterococci, mostly in vitro, using this editing tool to target resistance- and virulence-related genes.

A metagenomic survey of bacterial communities from kurut: The fermented cow milk in Kyrgyzstan

Kurut is a traditional dry dairy product mostly consumed in Central Asia. In this study, the distribution of the dominant bacteria present in kurut samples (n=84) originated from seven (Chuy, Issyk-Kul, Talas, Naryn, Jalal-Abad, Osh, and Batken) regions in Kyrgyzstan were analyzed with Illumina iSeq100 platform. The dominant phylum detected was Firmicutes followed by Proteobacteria, Actinobacteria, Cyanobacteria/Chloroplast, and Tenericutes. The most abundant family detected was Lactobacillaceae followed by Streptococcaceae, Enterococcaceae, Chloroplast, and Leuconostocaceae. At the genus level, Lactobacillus was the predominant one in samples and Streptococcus, Enterococcus, Lactococcus, and Streptophyta followed this. Further comprehensive characterization analyses in kurut samples may have potential applications both in industrial starter culture developments and also future therapeutic approaches based on potential strains with probiotic properties.

CRISPR-Cas systems target endogenous genes to impact bacterial physiology and alter mammalian immune responses

CRISPR-Cas systems are an immune defense mechanism that is widespread in archaea and bacteria against invasive phages or foreign genetic elements. In the last decade, CRISPR-Cas systems have been a leading gene-editing tool for agriculture (plant engineering), biotechnology, and human health (e.g., diagnosis and treatment of cancers and genetic diseases), benefitted from unprecedented discoveries of basic bacterial research. However, the functional complexity of CRISPR systems is far beyond the original scope of immune defense. CRISPR-Cas systems are implicated in influencing the expression of physiology and virulence genes and subsequently altering the formation of bacterial biofilm, drug resistance, invasive potency as well as bacterial own physiological characteristics. Moreover, increasing evidence supports that bacterial CRISPR-Cas systems might intriguingly influence mammalian immune responses through targeting endogenous genes, especially those relating to virulence; however, unfortunately, their underlying mechanisms are largely unclear. Nevertheless, the interaction between bacterial CRISPR-Cas systems and eukaryotic cells is complex with numerous mysteries that necessitate further investigation efforts. Here, we summarize the non-canonical functions of CRISPR-Cas that potentially impact bacterial physiology, pathogenicity, antimicrobial resistance, and thereby altering the courses of mammalian immune responses.