Isolation and identification of halophilic and halotolerant bacteria from the sediments of the Qeshm Island mangrove forest

Abstract

Due to specific environmental and ecological conditions, mangrove forests are known as marine transitional zones between sea and land, and, as such, they host organisms with high ecological plasticity. The mangrove forests of Qeshm Island (Iran) are relatively pristine habitats and represent an ideal target for investigating patterns of either aquatic or benthic biodiversity. To provide insights on microbial diversity in this area, nineteen halophilic and halotolerant bacteria were isolated from the sediments in 2017 during low tide. The extracted bacterial strains were studied morphologically by streaking, initial observation of colonies and bacterial staining, and characterized using a battery of biochemical tests including KOH, MR, VP, urease, TSI, S/I/M, Mac, LIA, ODC, ADH, oxidase, catalase, and tryptophan deaminase. The optimum growth of halophilic bacteria was observed in salt concentrations from 5 to 20% NaCl, whereas the extreme halophilic Gram-positive strain grew in salt concentration of up to 30% NaCl. Molecular analyses were also carried out on four halophilic strains and one extreme halophilic gram-positive bacteria. Phylogenetic taxonomy analysis, after 16S rDNA gene Sanger sequencing, revealed that the halophilic bacteria were closely related to the strain types of the genus Bacillus including Bacillus licheniformis, Bacillus velezensis, Bacillus Paralicheniformis and Bacillus sp. with 99% bootstrap value. The extreme halophilic strain was associated to strains of Planococcus plakortidis with 100% bootstrap value.

Keywords

• Halophiles
• Extreme halophile
• Halotalerant
• Gram-Positive
• Molecular identification
• Mangrove sediments