Nitrogen and phosphorus-related functional genes enhance nutrient removal in the integrated aquaculture wastewater bioremediation system in the presence of photosynthetic bacteria

Integrated Aquaculture Wastewater Bioremediation Systems (IAWBSs) are crucial for the treatment of nutrient-rich mariculture water. However, there is a lack of detailed information about the functional mechanisms between nitrogen (N) and phosphorus (P) functional genes and the bacterioplankton community in the presence of photosynthetic bacteria (PSB). This study evaluated the connections between N and P functional genes in IAWBS under the influence of PSB. The results showed significant improvements in effluent quality, with removal efficiencies of 79, 74, 83, 90, and 71% for NO₂⁻-N, NO₃⁻-N, PO₄³⁻₋P, NH₄⁺-N, and COD_Mn, respectively. The addition of PSB enhanced and altered microbial diversity within the system, promoting the expression of functional genes related to N and P cycling. Notably, genes associated in denitrification (nirK and nirS); ammonification (ureC); and nitrogen fixation (nifH) and amoB, involved in nitrification, were significantly increased after the addition of PSB. Furthermore, genes such as phnK, phoD, and phoX, which are involved in P transformation, also showed increased expression levels. These genes were closely linked to the microbial community distribution, species diversity, and nutrient cycling. Microbial community changes can result in changes in functional gene abundance. This study provides important and novel insights for the development of bioremediation strategies for polluted sites. This demonstrates the fundamental relationships between the IAWBSs' functional units. and the distribution of microbial communities under the influence of PSB.