Genome Editing with Cas9 in Lactobacilli

Characterization of agr-like Loci in Lactiplantibacillus plantarum and L. paraplantarum and Their Role in Quorum Sensing and Virulence Inhibition of Staphylococcus aureus

The pathogenicity of Staphylococcus aureus is largely regulated by the agr quorum sensing (QS) system encoded by agrBDCA, which coordinates virulence factor production through secretion and sensing of auto-inducing peptides (AIPs). agr-like systems are also present in coagulase-negative staphylococci, and several of these encode AIPs that inhibit S. aureus QS. In lactic acid bacteria, a similar locus was previously identified in Lactiplantibacillus plantarum WCSF1 termed lamBDCA. Here, we characterized the lamBDCA locus in L. plantarum LMG 13556 and L. paraplantarum CIRM-BIA 1870, and explored the effects on S. aureus QS. Notably, we found that co-cultivation with L. paraplantarum significantly inhibits S. aureus QS and hemolysin production, while less so for L. plantarum. The inhibition by L. paraplantarum was lost upon disruption of its lamBDCA locus, suggesting that the L. paraplantarum AIP mediates cross-species interference with S. aureus agr activation. Transcriptomic analysis revealed that lamBDCA in L. paraplantarum controls the expression of genes belonging to various functional categories, including stress response and metabolism. The latter includes genes encoding riboflavin (B2 vitamin) biosynthesis, which enabled the growth of the L. paraplantarum lamB mutant in the presence of roseoflavin, a toxic riboflavin analogue. Collectively, our results show that L. paraplantarum CIRM-BIA 1870 interferes with S. aureus virulence gene expression through QS suppression, and they implicate QS in the probiotic properties of L. paraplantarum.

CRISPR/Cas tools for enhancing the biopreservation ability of lactic acid bacteria in aquatic products

Lactic acid bacteria (LAB) plays a crucial role in aquatic products biopreservation as it can inhibit many bacteria, in particular the specific spoilage organisms (SSOs) of aquatic products, by competing for nutrients or producing one or more metabolites which have antimicrobial activity, such as bacteriocins. Lactobacillus spp. and Lactococcus spp. are the most commonly used Lactic acid bacterias in aquatic products preservation. The improvement of gene editing tools is particularly important for developing new lactic acid bacteria strains with superior properties for aquatic products biopreservation. This review summarized the research progress of the most widely used CRISPR/Cas-based genome editing tools in Lactobacillus spp. and Lactococcus spp. The genome editing tools based on homologous recombination and base editor were described. Then, the research status of CRISPRi in transcriptional regulation was reviewed briefly. This review may provide a reference for the application of CRISPR/Cas-based genome editing tools to other lactic acid bacteria species.

Development and Applications of CRISPR/Cas9-Based Genome Editing in Lactobacillus

Lactobacillus, a genus of lactic acid bacteria, plays a crucial function in food production preservation, and probiotics. It is particularly important to develop new Lactobacillus strains with superior performance by gene editing. Currently, the identification of its functional genes and the mining of excellent functional genes mainly rely on the traditional gene homologous recombination technology. CRISPR/Cas9-based genome editing is a rapidly developing technology in recent years. It has been widely applied in mammalian cells, plants, yeast, and other eukaryotes, but less in prokaryotes, especially Lactobacillus. Compared with the traditional strain improvement methods, CRISPR/Cas9-based genome editing can greatly improve the accuracy of Lactobacillus target sites and achieve traceless genome modification. The strains obtained by this technology may even be more efficient than the traditional random mutation methods. This review examines the application and current issues of CRISPR/Cas9-based genome editing in Lactobacillus, as well as the development trend of CRISPR/Cas9-based genome editing in Lactobacillus. In addition, the fundamental mechanisms of CRISPR/Cas9-based genome editing are also presented and summarized.