Streptococcus salivarius subsp. thermophilus’UN CRISPR-CAS TİP II SİSTEMİNİN TESPİTİ VE TANIMLAMASI

Abstract

Lactic acid bacteria (LAB) are a group of bacteria characterized by their ability to produce lactic acid as the final product. They are fermentative, acid-tolerant bacteria. Lactic acid bacteria can be Gram-positive cocci or rods; they are microaerophilic, acid-tolerant, catalase-negative, generally non-spore-forming, and have low guanine-cytosine (GC) content. One of the lactic acid bacteria commonly used in the food industry as a starter culture is the Streptococcus genus, particularly the Streptococcus salivarius subsp. thermophilus bacterium, which has been a part of starter cultures for yogurt production throughout history.

Commercial fermentations with Streptococcus salivarius subsp. thermophilus are sensitive to specific phage infections. Contamination of milk fermentation systems containing this microorganism with a virulent phage can lead to product loss by breaking down the starter cultures present in the environment. Therefore, the detection of the bacteriophage resistance of Streptococcus salivarius subsp. thermophilus is of great importance for the formation and identification of CRISPR-Cas systems. CRISPR-Cas systems not only serve as a natural immune system in most prokaryotes but can also be used as a tool in newly developed genome modifications and evolutionary research. Streptococcus salivarius subsp. thermophilus is an important model organism for the study and implementation of CRISPR systems.

In this study, the Cas9 and Csn2 genes of the CRISPR-Cas Type II-A and Type II-C regions of the selected reference microorganism Streptococcus salivarius subsp. thermophilus ATCC 19258 strain were determined in silico. Subsequently, specific primers for the Cas9 and Csn2 genes of the Type II-A region and the Cas9 gene of the Type II-C region were designed. In the final stage, a qualitative qPCR application was performed to detect the CRISPR-Cas Type II-A and Type II-C regions of Streptococcus salivarius subsp. thermophilus strains in the Hacettepe University Food Engineering Department FoodOmics Laboratory Culture Collection, completing the detection and characterization of the CRISPR-Cas Type II system.