Distribution and heterotrophic ammonia-oxidizing characteristics of Alcaligenes sp. in aquaculture systems

Abstract:

[Background] As the intensification in aquaculture keeps increasing, nitrogen pollution and eutrophication in aquaculture water have become increasingly serious, which inhibit the activity of autotrophic ammonia-oxidizing bacteria. Therefore, it is of great significance to understand the distribution and functional characteristics of heterotrophic ammonia-oxidizing microorganisms such as Alcaligenes sp. in aquaculture systems to address nitrogen pollution. [Objective] We studied the distribution of Alcaligenes sp. in aquaculture areas, isolated the strain with efficient nitrogen conversion ability, and characterized the ammonia oxidation of the strain screened out, aiming to provide strain resources and theoretical guidance for the efficient nitrogen removal from aquaculture tail water. [Methods] The high-throughput sequencing of the 16S rRNA gene was employed to reveal the distribution of Alcaligenes sp. in the aquaculture areas in Guangdong. Alcaligenes sp. strain CHO6 with strong heterotrophic ammonia-oxidizing capacity was isolated from an aquaculture sediment sample by continuous enrichment culture. The single factor tests were carried out to explore the factors influencing the heterotrophic ammonia-oxidizing capacity of the strain CHO6. [Results] Alcaligenes sp. widely existed in the aquaculture areas in Guangdong. Alcaligenes sp. CHO6 isolated from an aquaculture sediment sample completely removed 10 mmol/L ammonia nitrogen within 48 h. The ammonia-oxidizing capacity of the strain CHO6 was influenced by a variety of factors including carbon source, temperature, pH, C/N ratio, dissolved oxygen, and initial ammonia nitrogen. [Conclusion] The prevalence of Alcaligenes sp. indicates strong adaptability to the aquaculture environment. Alcaligenes sp. CHO6 as a heterotrophic strain had strong ammonia-oxidizing capacity and resistance to high concentrations of ammonia nitrogen. This study provides strain resources for the removal of nitrogen in aquaculture environments, which is of great significance for the management of aquaculture tail water.