Diversity of Culturable Bacteria degrading Antarctic and Arctic Soil Humic Acids

Abstract

Soil humic substances (HS), composed mainly of humic acids (HA), are widely distributed in cold natural environments and are known as an important fraction of soil organic carbon (SOC). Although bacteria dominate the soil environment, their ability to degrade and/or partially biotransform the stable HS has not been reported well. To study the diversity of bacterial degraders of HS in polar area, a total of 99 bacterial strains were isolated on Humic Acid Vitamin Agar from various soil samples: 45 strains from 66 sites in Nome, Alaska (August, 2011) and 54 strains around the King Sejong Station, Barton Peninsula, Antarctica (January, 2012). They were identified based on 16S rRNA sequence similarity using EzTaxon program, and then grouped as follows: Phylum Firmicutes (82.5%), Class r-Proteobacteria (14.7%), and miscellaneous group (2.8%) from Arctic Alaska; r-Proteobacteria (83.3%) and miscellaneous group (16.7%) from Antarctic King Sejong Station. For a detailed analysis, they were affiliated with Pseudomonas (15 strains), Paenibacillus (27 strains),and the other (3 strains) from Arctic samples and Pseudomonas (43 strains) and the other (11 strains) from Antarctic ones. Since the HA-degraders are believed to play an important role in the cycle of SOC, as the first step, we are studying the HA-degradation pathway(s) by polar bacteria.heir ability to degrade and/or partially biotransform the stable HS has not been reported well. To study the diversity of bacterial degraders of HS in polar area, a total of 99 bacterial strains were isolated on Humic Acid Vitamin Agar from various soil samples: 45 strains from 66 sites in Nome, Alaska (August, 2011) and 54 strains around the King Sejong Station, Barton Peninsula, Antarctica (January, 2012). They were identified based on 16S rRNA sequence similarity using EzTaxon program, and then grouped as follows: Phylum Firmicutes (82.5%), Class r-Proteobacteria (14.7%), and miscellaneous group (2.8%) from Arctic Alaska; r-Proteo