Diversity of Bacillus-like bacterial community in the rhizospheric and non-rhizospheric soil of halophytes (Salsola stocksii and Atriplex amnicola), and characterization of osmoregulatory genes in halophilic Bacilli

Abstract

Salinity is one of the major abiotic stresses; a total of 3% of the world’s land mass is affected by salinity. Approximately 6.3 million hectares of land in Pakistan is affected by salinity to varying degrees, and most of the areas are arid to semiarid with low annual precipitation. The aim of the present study is to identify and characterize Bacillus and Bacillus-derived bacterial genera from the rhizospheric and non-rhizospheric soil samples from the Khewra Salt Mine, Pakistan, by using culture-independent and -dependent methods. Seven Bacillus-like bacterial genera, Bacillus, Halobacillus, Virgibacillus, Brevibacillus, Paenibacillus, Tumebacillus, and Lysinibacillus, were detected by using pyrosequencing analysis, whereas only four genera, Bacillus, Halobacillus, Oceanobacillus, and Virgibacillus, were identified by culture-dependent methods. Most of the Bacillus-like isolates identified in this study were moderately halophilic, alkaliphilic, and mesophilic bacteria and were considered a good source of hydrolytic enzymes because of their ability to degrade proteins, carbohydrates, and lipids. Eight Bacillus-like strains from the genera Bacillus, Halobacillus, Oceanobacillus, and Virgibacillus showed positive results for the presence of ectABC gene cluster (ectoine), six strains could synthesize betaine from choline, and six strains tested positive for the synthesis of proline from either glutamate or ornithine by using proline dehydrogenase enzyme.