Functional metagenomics of bark microbial communities from avocado trees (Persea americana Mill.) reveals potential for bacterial primary productivity

Bark microbial communities are poorly understood, and information on the metabolic capacities of their inhabitants is lacking. Bark microbial communities share part of their taxonomic composition with soil, but the functional differences and similarities are unknown. By comparing bark microbial communities of avocado trees (Persea americana, Mill.) with rhizospheric soil, functional processes relevant to the bark environment were identified. DNA from bark and soil communities was extracted from the same trees, and shotgun metagenomics sequencing was performed using nextSeq technology. Genes were identified by BLAST methods, and functional annotation was performed with KEGG databases as a reference. Bacterial oxygenic and anoxygenic photosynthesis genes were highly abundant in bark as compared to soil. Furthermore, increased presence of nitrogenase genes suggests a potential for nitrogen fixation. Genes for methanol utilization were abundant in bark, but no evidence of methane utilization potential was observed. Bark microbial communities have the genetic information for potential primary productivity, which might contribute to microbial growth independent of plant-derived carbon substrates.