A comparative analysis of the microbial communities and functional genes of the nitrogen cycling in mangroves of China, Indian and Malaysia

Mangrove wetlands are a unique transitional coastal zone between terrestrial and aquatic ecosystems along the subtropical and tropical coastlines. The abundant biodiversity of mangroves facilitates their various ecological functions, including pollution control and nitrogen cycling. However, the comparison of specific nitrogen metabolic pathways and microbial communities in mangrove ecosystems of different countries is scarce. In this study, microbial communities and functional genes involved in nitrogen cycling were analyzed and compared by Illumina sequencing technique of collected surface and bottom sediments from mangroves in China, India, and Malaysia. The results revealed the highest microbial diversity in India (3310 OTUs), followed by China (2589 OTUs) and Malaysia (1811 OTUs). Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were the main nitrate reduction pathways in mangrove sediments. Anammox was significantly more active in Odisha and Goa of India than in all other samples. Woeseia and Desulfococcus in China, Robiginitalea and Tenacibaculum in India, and Woeseia in Malaysia were identified as the active organisms involved in the nitrogen cycle. The results provided a basis for preliminarily understanding the microbe-driven nitrogen conversion in mangroves of different regions.