Screening and Characterization of Nitrite-Degrading Bacterial Isolates Using a Novel Culture Medium
In this study, a novel culture medium that simulates shrimp pond conditions was established to screen nitrite-degrading isolates. The medium was supplemented with nitrite as a nitrogen source and shrimp feed as the major carbon source, to achieve the high nitrogen and low carbon nutritional status found in shrimp farming ponds. Screening using this medium identified potent denitrifying Bacillus isolates, among which Bacillus subtilis M7-1 was considered best. M7-1 was able to completely degrade nitrite-N in 24 h without much consumption of dissolved oxygen. Efficient denitrification activity took place in liquid cultures within a set of non-stringent ranges of pH (5.0-9.0), salinity (0-30) and temperature (25-35℃). The denitrifying enzyme gene was amplified, se-quenced and further identified as nirS type. In biosecurity assessments, M7-1 had no negative effects on shrimps at a dose of 106cfu mL−1. M7-1 could therefore be used in aquaculture to reduce and control the nitrogen concentration, and to promote the development of sustainable and healthy culture systems.
Key wordsaerobic denitrification nitrite screening culture medium Bacillus subtilis
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This research was supported by the Special Fund for Qingdao Marine Biomedical science and Technology Innovation Center, China (No. 2017-CXZX01-3-13).
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