Genomic analyses of a novel bioemulsifier-producing Psychrobacillus strain isolated from soil of King George Island, Antarctica

摘要

Cold-adapted bacterial strains are potentially valuable for biotechnological applications involving the production of cold-active enzymes and bioproducts important to various industries. A psychrotolerant, aerobic, Gram-positive, endospore-forming, bioemulsifier-producing strain, named Val9, was isolated from Vale Ulman soil samples, King George Island, Antarctica and identified as a member of the genus Psychrobacillus. To better characterize this novel strain, its whole genome was sequenced revealing a size of 3,986,526 bp with a G + C content of 36.6, and 4042 predicted coding DNA sequences (CDSs). Digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses between strain Val9 and the type strains of the seven Psychrobacillus species revealed that the highest values were observed with Psychrobacillus psychrodurans DSM11713(T) but below the conventional thresholds of 70 dDDH and 95 ANI for bacterial species assignment, suggesting that strain Val9 could represent a distinct species. As potential low-temperature adaptation strategies, genes encoding cold shock proteins, transporters for glycine-betaine, carnitine and choline, and enzymes acting against oxidative stress were found in Val9 genome. DEAD-box RNA helicases, important for cold and oxidative tolerance, and a two-component signal transduction system related to plasmatic membrane fluidity as well as biotechnologically important CDSs, related to levan production, were detected. The sacB gene encoding the enzyme levansucrase was exclusive for Val9 and it was not found in the other Psychrobacillus type strains. Altogether, the comparative genomic analyses presented here highlight important metabolic pathways and the biotechnological potential of this novel strain.