Poster Presentation Australian Microbial Ecology 2019

Kocuria marina CE7 is salt tolerant, and alkali-producer (#116)

Kyoung Lee 1
  1. Changwon National University, Changwon-si, GYEONGNAM, South Korea

Human skin is the border with the external environment and, as such, is colonized by a diverse collection of microorganisms including bacteria. These microorganisms have been varying between the individuals as well as different parts of the skin. The skin surface pH is 4.8-6.0 and influences various factors for the growth of resident and pathogenic microorganisms. The acidic PH of the skin is one of the significant factors in making the skin less favorable for other foreign harmful bacteria. In this present study, we isolated a strain, CE7, from human skin with the high extracellular buffering property. The isolate is most close to Kocuria marina based on 16S rRNA gene sequencing. Genus Kocuria is gram-positive, coagulase-negative, and coccoid and belongs to a phylum Actinobacteria. Kocuria marina was initially isolated from marine sediment and showed to be salt tolerant. During growth on Nutrient broth, the pH of the medium is changed to alkaline 8.5-9.5, irrespective of an initial pH of the medium. The strain gives rise to the normal growth at pH 6~10, and the same growth level was attained at initial pH 5.0 for 72 h. Even in the latter case, the final pH was 8.5, indicating K. marina CE7 produces a buffering metabolite with a pKa of around 8.5. This strain also can grow at high NaCl concentrations up to 5% in the medium. Amino acid analysis of the supernatant of media following cell growth on mineral salts basal showed an accumulation of citrulline and valine. This result indicated that these metabolites and metabolism related to the biosynthesis of them might be related to the buffering capacity of the medium. Our complete the first genome sequence of K. marina showed that citrulline is biosynthesized by ornithine carbamoyltransferase (ArgF) which is encoded in a gene cluster argCJBDFR.