Taxonomic structure and function of the corn stover degradative microbial consortium GF‐20 following growth on different sources of nitrogen

Abstract

AbstractMicrobial consortia have substantial promise to degrade returned straw biomass and implement conversion strategies for soil nutrients to improve the quality of cultivated land. However, the composition of microbial consortia under different nitrogen conditions, the interaction between members and the functions during the process of decomposition of lignocellulose remain poorly understood. This study comprehensively examines the functional potential and structural diversity of the GF‐20 microbial consortium that degrades lignocellulose and soil used for inoculation and will explore the associated metabolic pathway networks in Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) using metagenomic analyses. Analyses of the metagenomic taxonomic affiliation data showed that the soil used for inoculation primarily contained members from the phyla Proteobacteria, Bacteroidetes, Acidobacteria, Chloroflexi and Acidobacteria, as well as Proteobacteria and Bacteroidetes in microbial consortia (N1 and N6). However, N6 is likely to be able to reduce the diversity of microbial species and change the community structure in a more concentrated comparison with N1. Notably, the key microbes were determined to be Cellvibrio, Brevundimonas, Flavobacterium and Achromobacter, whose analogous physiological functions were critical for the degradation of lignocellulosic substrates. The COG annotation indicated that the microbial metabolic cluster was the predominant category in all the samples, while the metabolic genes in N6 were relatively less abundant compared with those in N1. The KEGG annotation demonstrated that the inoculation soil (Q) has more metabolic functions and pathways than those of the microbial consortia, and the number of orthologies, modules, pathways and enzymes in N6 was observably lower than that in N1. A more detailed analysis showed that both of the consortia had functional profiles that were highly similar. These functional profiles clearly differed compared with those in the Q community. The relative abundance (RA) of ABC transporters in the Q was higher than that in the microbial consortia and higher in N1 than in N6. However, the two‐component system of N1 and N6 was higher than that of Q because of their relation to the microbial degradation of lignocellulosic materials. Most of the abundances of lignocellulolytic enzymes in the Q were lower than those in the microbial consortia (N1 and N6), and the RAs of some of these enzymes (e.g., β‐glucosidase, xylan 1,4‐β‐xylosidase, arabinoxylan arabinofuranohydrolase, β‐galactosidase, feruloyl esterase, mannan endo‐1,4‐β‐mannosidase, alpha‐glucuronidase and arabinogalactan endo‐1,4‐β‐galactosidase) in N6 were significantly higher than those of N1.The taxonomic structure and function of the Q and that of the consortia differed significantly, and the use of urea resulted in a decrease in the taxonomic species of microorganisms. The changes in functional diversity were accompanied with variation in the microbial composition, many of which were related to the microbial degradation of lignocellulolytic materials. Most of the degradative lignocellulolytic function in Q was lower than those of the microbial consortia N1 and N6, which aid in the degradation of straw.