Bacterial diversity in south coast of the Caspian Sea: Culture-dependent and culture-independent survey

Abstract

Bacterial diversity in the south coast of the Caspian Sea was studied by analyzing 16S rDNA clone library and cultivation technique. Analysis of inserts of 30 clones revealed a total of 13 OTUs. All of these sequences were related to Proteobacteria including Betaproteobacteria (60%), Gammaproteobacteria (22%) and Alphaproteobacteria (18%). The majority of these sequences (40%) branched with member of Limnobacter. Within the cultivation effort, phylotypes related to Gammaproteobacteria (60%), Firmicutes (27%), Actinobacteria (9%) and Bacteroidetes (4%) were retrieved. Members of the Bacillus (14%) and Rheinheimera (18%) were the most common isolates. The secretions of eight hydrolytic enzymes and antibiotic compounds, as well as resistance to heavy metals were studied in these marine strains. Among them 46, 45, 38, 27, 19, 19, 7 and 4% of bacterial isolates were able to produce protease, pectinase, xylanase, amylase, cellulase, lipase, urease and DNase, respectively. Two strains which are phylogenetically related to Streptomyces and Stenotrophomonas produced antimicrobial compounds and could inhibit the growth of Candida albicans and Bacillus subtilis,respectively. A total of 2, 1, 2, 3 and 2 strains could survive in the presence of lead (1500 ppm), cadmium (1000 ppm), zinc (2000 ppm), copper (2000 ppm), and Chromium (2000 ppm), respectively. The investigation showed that this marine environment harbors a high bacterial diversity which is a potential source of hydrolytic enzymes and other valuable biotechnological activities.