Review of CRISPR-Cas Systems in Listeria Species: Current Knowledge and Perspectives

Abstract

Listeria spp. are pathogens widely distributed in the environment and Listeria monocytogenes is associated with food-borne illness in humans. Food facilities represent an adverse environment for this bacterium, mainly due to the disinfection and cleaning processes included in good hygiene practices, and its virulence is related to stress responses. One of the recently described stress-response systems is CRISPR-Cas. Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (cas) genes have been found in several bacteria. CRISPR-Cas has revolutionized biotechnology since it acts as an adaptive immune system of bacteria, which also helps in the evasion of the host immune response. There are three CRISPR systems described on Listeria species. Type II is present in many pathogenic bacteria and characterized by the presence of cas9 that becomes the main target of some anti-CRISPR proteins, such as AcrIIA1, encoded on Listeria phages. The presence of Cas9, either alone or in combination with anti-CRISPR proteins, suggests having a main role on the virulence of bacteria. In this review, we describe the most recent information on CRISPR-Cas systems in Listeria spp., particularly in L. monocytogenes, and their relationship with the virulence and pathogenicity of those bacteria. Besides, some applications of CRISPR systems and future challenges in the food processing industry, bacterial vaccination, antimicrobial resistance, pathogens biocontrol by phage therapy, and regulation of gene expression have been explored.

Whole Genome Sequence Analysis of <em>Listeria monocytogenes</em> Isolates Recovered from Cattle Farms, Cattle Abattoirs, and Retail Outlets in Gauteng Province, South Africa

“…It has been suggested that some of the CRISPR-Cas systems detected in L. monocytogenes are functional with spacers matching sequences of known Listeria phages and plasmids [129]. The CRISPR-Cas system, which exists in L. monocytogenes, acts as an adaptive immune system and has been documented to help invade the host immune system [46].…”

“…Isolates of L. monocytogenes may pose a therapeutic threat since Fosfomycin, encoded by the gene, is widely used in the country's livestock industry. The AMR gene, the CRISPR-Cas system, and proviruses/prophages are known to play some roles in the survival of L. monocytogenes in the food system [38,39,46].…”

“…The Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPRassociated (Cas) CRISPR-cas system exists in several bacteria, including Listeria spp., which acts as an adaptive immune system of bacteria, is known to help invade the host immune system [46]. Several types of CRISPR-Cas have been reported in Listeria spp., which include Cas-type IA, Cas-type IB, and Cas-type IIA [47].…”

“…In L. monocytogenes, it has been found that 41.4% of some isolates contain putative cas genes [48,49]. Various CRISPR-Cas systems in L. monocytogenes isolates recovered from cattle farms, abattoirs, foods, food processing environments, and retail outlets have been found [46,50,51,52].…”

Complete genome of the Listeria monocytogenes strain AUF, used as a live listeriosis veterinary vaccine

“…2 ). The majority of these Lm strain AUF-specific genes encoded uncharacterized hypothetical proteins, Listeria CRISPR-associated proteins (Cas1/Cas2/Cas9/Csn2) 77 , phage proteins, Type I restriction-modification system components, and in contrast to some Lm strains, GNAT family Acetyltransferase, Gp45 protein, 4-hydroxy-2-oxoglutarate aldolase (EC 4.1.3.16), 2-dehydro-3-deoxyphosphogluconate aldolase (EC 4.1.2.14), transcriptional regulator, ADP-ribosyl glycohydrolase, putative EsaC protein analog ( Listeria type 3), cassette chromosome recombinase B, and mobile element proteins. Bacteriophage A118 genes which have been known as Listeria phage A118 (NCBI Acc.…”