Isolation and identification of sulfur oxidizing bacteria in agricultural soil and evaluating sulfur oxidation yield

Sulfur oxidizing bacteria are important in agriculture. The aim of this study was to identify the sulfur oxidizing bacteria in Sarcheshmeh (Kerman, Iran) agricultural soil.
Sampling was conducted from agricultural soil in Kerman province, Iran. After enrichment, samples were purified in the basic mineral culture containing sulfur as the only source of energy. Sulfur oxidation capability was evaluated based on the variation of pH and sulfate content and then strains of sulfur oxidizing were isolated and identified using morphological characteristics and phylogenic techniques. The best strains were selected and were evaluated for variation of pH and sulfate content by isolates in different pH and temperature.
Six sulfur-oxidizing strains were isolated and identified which had similarity to Thiobacillus and Starkeya genous. Isolates of 103, 129, 190 and 158 were mesophyll and neutrophil, but isolates of 192 and 156 were thermophile and alkalophill. Of these isolates, isolate 103 was 99.86% similar to Starkeya novella, identified as superior isolate, due to the most sulfur oxidation capability in the synthetic mineral medium containing sulfur.
Discussion and Isolate 103 was able to grow in neutral to slightly alkaline conditions with pH 7.5. Most of the growth of this isolate was at 30 ° C as aerobic. This isolate was facultative chemolithotroph and the results of this research showed capacity of the isolate for oxidizing sulfur, so that it could be used as a practical isolate in bio-fertilizers for neutral to alkaline and saline conditions in agriculture.