The Diversity of Halotolerant and Halophilic Bacteria in the Soil of the Nasinuan Secondary Forest in Maha Sarakham, Thailand

Abstract

In the present study, we investigated the diversity of halotolerant and halophilic bacteria in the soil of the Nasinuan Secondary Forest using the culturable approach. Halotolerant, slightly halophilic, and moderately halophilic bacteria were isolated from soil samples using the halobacteria medium containing 0%, 3%, and 6% w/v sodium chloride, respectively. In total, 55 isolates were obtained. A decreasing trend of bacterial diversity was found with the increase in concentration of sodium chloride in the medium. From a comparison of cell and colony morphologies, 16 isolates were selected for identification based on 16S rDNA sequence analysis. Of the 16 isolates, 14 isolates were halotolerant bacteria and 2 isolates were slightly halophile. Many of them had an ability to grow in a wide range of NaCl (0-8% w/v). The 16 isolates belonged to 5 genera, namely Bacillus, Enterobacter, Janibacter, Rhodococcus, and Staphylococcus. The dominant species belonged to the genus Bacillus. The phylogenetic analysis showed genetic diversity covering 5 clusters: Gram-negative rods; Gram-positive rods/cocci, nonendospore-forming; Bacillus sensu stricto; Bacillus sensu lato; and Gram-positive cocci. This is the first comprehensive study of culturable halotolarant and halophilic bacterial diversity in a non-saline soil of Thailand.