Isolation and identification of sulfur-oxidizing chemolithotrophic bacteria from Qeshm salt cave

Chemolithotrophic bacteria have an important role in the biogeochemical cycle in natural ecosystems. For instance, the oxidative part of the sulfur cycle is handled by sulfur-oxidizing bacteria. Moreover, these bacteria have an important role in various industrial fields including bioleaching. The aim of this study was isolation and identification of chemolithotrophic sulfur-oxidizing bacteria from the Namakdan cave Qeshm, Iran.
In this cross-sectional study, after sampling from the Namakdan cave in Qeshm and transferring the samples (salt, water, and sediment) to the lab, sample inoculation into enrichment media was carried out with three concentrations of NaCl. Following pH and temperature measurement, samples were transferred into solid and two-phase media. Further characterization of the isolates was performed using 16S rRNA gene amplification. Further analysis was performed to characterize the autotrophic or heterotrophic features of the isolates. Biomass was examined using classical turbidity method.
Totally, 39 strains were isolated from samples, based on differences in primary features such as colony form or growth rate. A total of 5 isolates were selected for further studies. Phylogenetic analysis showed that these isolates belong to Halothiobacillus genus.
Due to 30% salinity and neutral pH of this cave, isolation of chemolithotrophic sulfur-oxidizing bacteria was limited to few genera. Chemolithotrophic bacteria have longer growth time in comparison to heterotrophic ones, increasing generation time to 30 days.