Abstract
BackgroundMangroves are highly productive ecosystems, with one of the highest microbial diversities among all ecosystems. The concerted activity of microbial community in mangrove sediment mediates element cycling, but the underpinning mechanism of microbial synergy remains unknown. ResultsHere, we reconstructed 671 strain-resolved metagenome-assembled genomes (MAGs) from three mangrove and two mudflat sediments in Mai Po Nature Reserve. We then inferred the genome-scale co-occurrence and co-transcription networks based on metabolic capacity and transcriptional activity of the carbon, nitrogen, and sulfur cycles. We observed that the centrality was significantly higher in co-transcription networks than in co-occurrence networks, indicating that MAGs had stronger interrelationships when transcriptionally active. Further, we classified 57 microbes with low relative abundance (0.01–0.79%) as keystone taxa, which play key roles in the maintenance of co-transcription network structure, and participate in carbon transformations, denitrification, and sulfate reduction processes. One of the keystone taxa is a newly proposed deltaproteobacterial order, Candidatus Mangrovidesulfobacterales, capable of dissimilatory sulfate reduction and an anaerobic mixotrophic lifestyle. These findings highlight the ecological importance of rare species. ConclusionsCollectively, this first screening of the potential keystone taxa in mangrove ecosystem based on genome-scale transcriptomic analysis revealed unique microbial functional assemblages, shedding light on microbial synergism in this ecosystem.