Analysis of CRISPR sequences and STX genes responsible for shigatoxin production in E. coli

Shiga toxin is an important factor in the pathogenicity of E. coli O157: H7 diseases. E. coli O157:H7 is an important bacterial pathogen in humans and animals causing disease in the food sector. It is a producer of shiga-like toxins encoded in the Stx gene with E.coli found in STEC. Cattle and chickens are the main propagation reservoirs of this group of bacteria. Shigatoxin-producing E.coli O157: H7 causes diseases in humans called hemorrhagic colitis (HC), thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Shiga toxins are AB5 proteins. These proteins are composed of an active A subunit linked to the 5 B subunit. These subunits are directed to specific glycolipid regions of the basic targeting targets. The RNA-N glycosidase activity of Shiga toxins leads to inactivation of 60S ribosomal subunits, leading to a halt in protein synthesis. CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeat-CRISPR associated) system is defined as an RNA-based adaptive immune system that provides resistance to genetic elements such as virüs and plasmids in bacteria and archeae. When CRISPR repeat and spacer sequences were first discovered in 1987, their role in bacteria was not fully understood. In 2007, CRISPR-Cas system was found to be a resistance mechanism against viruses and plasmids. Approximately 45 nuclease (cas) enzymes have been identified in the CRISPR system. These cas enzymes show nuclease activity by identifying a specific DNA region of about 25-30 bp and identifying and truncating the target DNA. Restriction enzymes, the defense mechanism of bacteria against phages, have paved the way for genetic engineering. In 2013, studies focused on cas9-RNA-mediated specific genome engineering in the human and eukaryotic genome. In this study, food-borne E coli O157: H7s were identified and examined by looking at the diversity of stx genes and identifying the CRISPR1 and CRISPR 2 regions involved in the defense and examining target genes for the regulation of sigatoxin production. Key words: E coli O157:H7, CRISPR, Shigatoxin, Virus, Immune system