Janibacter sp. isolated from deschampsia antarctica rhizosphere as a potential source of antimicrobial compounds

Abstract

In this study, 106 bacterial strains were isolated from rhizosphere of Deschampsia antarctica and used for the screening of potential antimicrobial compounds. Among all the bacterial strains, 61 (57.55%) were classified as Gram-positive, 34 (32.08%) as Gram-negative, and 11 (10.37%) did not grown under the laboratory culture conditions and were not classified. Organic crude extracts were analysed for potential antimicrobial activity and the B-22-EA ethyl acetate extract was the most effective inhibiting 84% of Escherichia coli growth, and Staphylococcus aureus, Pseudomonas aeruginosa and Micrococcus luteus by 31, 17 and 5%, respectively. The B-22-EA extract showed a MIC of 187 µg/mL on Cryptococcus neoformans, and of 438 µg/mL on Trichophyton rubrum. The strain, coded as B22, was classified as Gram-positive and the taxonomic analysis indicated that this strain belongs to the genera Janibacter, with 98.66% of similarity with Janibacter hoylei PVAS-1 and Janibacter limosus DSM 11140; 98.51% with Janibacter cremeus HR08-44, and 98.36% with Janibacter indicus 0704P10-1, Janibacter anophelis H2.16B and Janibacter terrae CS12. The cellular fatty acids (CFA) composition for B22 (Janibacter sp.) was determined by fatty acid methyl esters (FAME) using gas chromatography and compared with those species for which the B22 strain has a high level of similarity. The comparison among the different species from the genus Janibacter shows that there is a difference in their CFA composition and in their optimum temperature for growth, showing the high biodiversity, even for the same species. The data from this study are important and B-22 (Janibacter sp.) is an interesting source of antimicrobial compounds.