Isolation and characterization of high efficient denitrifying bacteria from deep sea sediments

Abstract:

[Background] With the environmental features of high pressure, low temperature and no light, deep sea areas contain abundant and characteristic microbial resources. [Objective] This study aims to isolate and screen aerobic denitrification bacteria strains with high denitrification efficiency from deep sea sediments, and reveal their denitrification characteristics, so as to provide material basis for the development of water denitrification microtechnology. [Methods] In this paper, deep-sea sediments from 10 stations in the East Pacific Ocean, South Atlantic Ocean and Southwest Indian Ocean were used as research materials. Two consecutive rounds of enrichment culture were carried out with inorganic nitrogen at 28℃. The strains capable of removing ammonia nitrogen, nitrite nitrogen and nitrate nitrogen were isolated, purified and screened by their qualitative denitrification capacities. The obtained strains were preliminary identified and classified through morphological and 16S rRNA gene sequence analysis. The growth and denitrification performance of the obtained strains were quantitatively studied in the media with ammonia nitrogen, nitrite nitrogen and nitrate nitrogen as the only nitrogen source, respectively. [Results] A total of 49 aerobic denitrifying bacteria were isolated from 10 deep-sea sediment samples, of which 3 strains, designated Pseudomonas sp. G111, Pseudomonas sp. G112 and Dietzia maris W023a, showed high denitrifying efficiency under aerobic conditions. Strains G111 and G112 shared 16S rRNA gene similarities of 99.2% with Pseudomonas bauzanensis BZ93^T. The 16S rRNA gene similarity between strain W023a and Dietzia maris ATCC 35013^T was 99.9%. After strains G111, G112 and W023a were cultured for 48 hours, their removal rates of ammonia nitrogen were 98.0%, 85.2% and 97.6%, respectively; their removal rates of nitrite nitrogen were 71.9%, 67.5% and 34.7%, respectively; their removal rates of nitrate nitrogen were 66.0%, 52.6% and 34.7%, respectively. Strains G111, G112 and W023a are three heterotrophic nitrifying-aerobic denitrifying bacteria. These strains could reduce nitrite or nitrate to nitrogenous gases by using aerobic denitrification, and convert ammonia nitrogen to nitrogenous gases by using heterotrophic nitrification-aerobic denitrification. [Conclusion] In this study, three strains of highly efficient aerobic denitrifying bacteria were isolated from deep-sea sediments, and the obtained strains have application potential in water purification, sewage treatment, ecosystem restoration.