Microbial Diversity, Extracellular Enzyme Activity And Antimicrobial Activity Of Culturable Bacteria Of Soil From Grove Mountains, East Antarctica

The Antarctic Continent is the land of Antarctica except the islands surrounding it.It offers a range of extreme climatic conditions that constitutes one of the harshestenvironments on earth. Although most of the continent is covered by glacial ice sheets,ice-free areas comprise around0.4%of the continental land mass. Most of the soilformation results from weathering process or microbial activities on sparse organicmaterial. It was once believed that there was no soil process occured in EastAntarctica inland plateau climate zone due to the extremely low temperature and lessprecipitation. The Grove Mountains area (72°20’-73°10’S,73°50’-75°40’E) is locatedon Princess Elizabeth Land, covered with ice and nuntakes all around the year. Duringthe austral summer during1999-2000, the Chinese16thAntarctica expedition teamentered the inland East Antarctica and found three soil spots in the southern MountHarding, Grove Mountains, East Antarctica. It was the first case that soils werediscovered in the inland of East Antarctica. Extreme habitats harbor a uniquecommunity of microorganisms which attracts us to explore. This paper aimed atexploring the microbial community composition of soil from Grove Mountainsthrough454pyrosequencing and subsequent bioinformatical analysis on the obtainedsequence data as well as exploring the diversity, extracellular enzyme activity andantimicrobial activity of culturable bacteria from the aforementioned soil, discoveringinformation on the microbial community composition of the three soil spots for thefirst time. Our study laid a foundation for the study of functioning of the Antarcticaecosystem and for the exploration of polar microbial resources.Three soil samples were collected during China’s26thAntarctica expedition (Sep.2009-Apr.2010) in the southern Mount Harding, Grove Mountains and stored at-20℃and-80℃, separately. Soil samples stored at-80℃were used for the extraction of total DNA. Specific454barcoded primers were used to amplify thebacterial16S rRNA gene fragments and the eukaryotic18S rRNA gene fragments;different sets of archaea-specific primers and varying PCR stringency were used toamplify the archaeal16S rRNA gene fragments. PCR products were sequenced andprocessed with bioinformatics method. Results show that bacterial phylotypes weremade up of12phyla altoghther, including Firmicutes, Proteobacteria, Actinobacteria,Tenericutes, Bacteroidetes, Cyanobacteria/Chloroplast, Verrucomicrobia, Chloroflexi(only in G1), Acidobacteria (only in G1and G2), Deinococcus-Thermus (only in G3),Gemmatimonadetes (only in G3) and Candidate division TM7(only in G2).Firmicutes were the first dominant bacterial group which accounted for77.00%(G1)、44.56%(G2) and88.76%(G3), separately; Proteobacteria were the second dominantbacterial group in all the three spots. None of the archaea-specific primers succeed togenerate archaeal sequences in all the three samples despite our endeavour, whichsuggested that archaea of soil from Grove Mountains were absent or in lowabundance. Eukaryotic phylotypes were made up of10groups altoghther, includingFungi, Apicomplexa, Dinophyceae, Mycetozoa, metazoa, Bacillariophyta,Chrysophyta, Oomycetes, Chlorophyta and Streptophyta. Fungi were the donimenteukaryotes which accounted for82.99%(G1),89.76%(G2),88.01%(G3),respectively. Almost all fungi grouped into Basidiomycota and Ascomycota lineages.Our analysis on between-habit-diversity showed that the three soil spots shared arelatively large proportion of mutual OTUs in both bacteria and eukaryote lineages.Among the three soil spots, G1and G3were more similar in community compositionin comparison with G2. Our research based on454pyrosequencing presented afull-scale and comprehensive assessment on the microbial diversity of the extremelydry and cold soil from Grove Mountains, getting insight into the ecologicalcomplexity under extreme environmental stress.Soil stored at different temperature were diluted and spread on the plate. A totalof39isolates from all the soil samples were obtained. Phylogenetic relationship wasanalysed based on their16S rRNA gene sequences. They belonged to20genera andgrouped into Firmicutes, Proteobacteria, Actinobacteria, Deinococcus-Thermus, Bacteroidetes lineages, of which each group occupied48.7%,25.6%,20.5%,2.6%,2.6%of the total, respectively. Bacillus was dominant. Different strains from soilstored at different temperatures were isolated, and this may be explained as viablebacteria were different at diverse temperatures. Plate method and agar block methodwere used to detect the production of extracellular enzymes and antimicrobialactivities of these bacteria, separately. Of the39isolates33showed the activity ofproducing at least one extracellular enzyme. Amylase-producing strains were the most(64.1%), and6strains were able to inhibit the growth of at least one tested bacteriumor fungus. Strains with extracellular enzyme activity and antim activity wouldcontribute to the exploration of cold-active enzymes and antibacterial (antifungal)material in Antarctica.