Halotolerant Bacillus diversity in hypersaline environments

Abstract

A total of 99 Gram-positive aerobic endospore-forming halotolerant rods were isolated from different hypersaline sources in Spain (salterns as well as saline soils). They were characterized taxonomically for a total of 178 features, including the utilization of 95 different substrates determined by the Biolog microbial identification system. These results were analysed by numerical techniques using the Jaccard (SJ) coefficient and clustering was achieved using the unweighted pair group method with averages algorithm. At 60% similarity level, the majority of the isolates were clustered in seven phenons. The guanine plus cytosine (G + C) content of some representative strains selected from each phenon ranged from 36.0 to 50.4 mol%. The isolates were identified as members of the genus Bacillus, and were assigned to the species B. pantothenticus, B. firmus, B. alcalophilus, B. megaterium, and B. laterosporus. They were extremely halotolerant, most were able to grow in media with up to 20 or 25% salt. The diversity of groups and characteristics of the halotolerant Bacillus isolated in this study indicate that they may play an important ecological role and contribute to the microbial diversity of hypersaline environments.Key words: halotolerant bacteria, Bacillus, taxonomy, hypersaline environments.