Translations:Lactobacillus acidophilus/7/en

Genomics

The specialization of prokaryotic genomes is distinguishable when recognizing how the prokaryote replicates its DNA during replication. In L. acidophilus, replication begins at an origin called oriC and moves bi-directionally in the form of replication forks. The DNA is synthesized continuously on the leading strand and in discontinuous Okazaki fragments on the lagging strand with help from the DNA polymerase III enzyme. An RNA primer is needed to initiate the DNA synthesis on the leading and lagging strands. DNA polymerase III follows the RNA primer with the synthesis of DNA in the 5' to 3' direction. L. acidophilus consists of a small genome with a low guanine-cytosine content, approximately 30%. A study comparing 46 genomes of varying strains of L. acidophilus found the genome size ranged from 1.95 Mb to 2.09 Mb, with an average size of 1.98 Mb. The average number of coding sequences in the genome was 1780, with the strains isolated from fermented foods and commercial probiotics having more coding sequences on average than those isolated from humans. L. acidophilus has an open state pan-genome (all of the genes within a species), meaning that the pan-genome size increased as the number of genomes sequenced increased. The core-genome (the genes shared by all individuals of a species) consist of around 1117 genes in the case of L. acidophilus. Genetic analysis also revealed that all L. acidophilus strains contained at least 15 families of glycosyl hydrolases, which are the key enzymes in carbohydrate metabolism. Each of the 15 GH families were involved in metabolizing common carbohydrates, such as glucose, galactose, fructose, sucrose, starch, and maltose. Genes encoding antibiotic resistance by means of antibiotic efflux, antibiotic target alteration, and antibiotic target protection were present in all L. acidophilus strains, providing protection against 18 different classes of antibiotic across all strains. Fluoroquinolone, glycopeptide, lincosamide, macrolide and tetracycline were the five classes of antibiotic to which L. acidophilus displayed the highest level of tolerance, with more than 300 genes relevant to these classes.