Microbial degradation of lignin is important to carbon cycling. The gut microbiome of wood‐feeding Hypomeces squamosus Fabricius has been shown to degrade lignin efficiently. However, the specific degradation mechanisms remain incompletely understood. In this study, we investigated the mechanism of lignin degradation using omics comparative analysis, focusing on differentially expressed genes and metabolic pathways in the gut microbiome of insects fed with a lignin‐rich diet. The dominant genus taxon was Pantoea (29.82%), which was predominant in insects fed with high lignin‐containing Iris ensata Thunberg, whereas Wolbachia and Enterobacter were predominant in insects fed with cabbage leaves (MHS_K group). Furthermore, expression levels of carbohydrate‐active enzymes from the auxiliary activities (AAs) families in the MHS_I group were 1.18 times higher than those in the MHS_K group. These mainly included lignin peroxidase and manganese peroxidase of the AA2 family, vanillyl‐alcohol oxygenase of the AA4 family, and 1,4‐benzoquinone reductase of the AA6 family. Expression levels of multiple genes encoding aromatic compound‐degrading genes (2303 accounted for 75.76% of the total upregulated genes) were found, including about 0.03% was related to lignin degradation. Genes MHS‐HN_11398_2 (protocatechuate 2,3‐dioxygenase) and MHS‐HN_4821_1 (muconolactone d ‐isomerase) were enriched in the MHS_I group. Three lignin‐degrading pathways were found: ortho‐cleavage and meta‐cleavage of catechol, as well as ring‐opening of protocatechuate. This study provides a comprehensive and theoretical evidence of the gut microbiome roles of H. squamosus Fabricius in lignin degradation.

With the prevalence of epidemics, disposable face masks have been used in large quantities and has caused global environmental pollution concern. The gut microbiome of Zophobas atratus larvae showed great potential for plastic degradation. In a preliminary study, the larval gut microbiome could degrade masks, which has not been previously reported. This study validated the ability of the gut microbiome to degrade masks. Functional microbiomes and metabolic pathways associated with the degradation of masks were also analyzed. Our findings confirmed that the larvae have high masks-degrading ability with a consumption of 60 ± 0.04 mg/d (dry mass by per 50 larvae), which is gut microbiome-dependent. At the genus level, Hafnia and Corynebaterium were highly abundant and contributed to masks degradation. The degrading metabolites were then identified, of which 46 were significantly upregulated. Steroid hormone biosynthesis and the cytochrome P450 pathway may be linked to DFM (PP) oxidation and degradation. Finally, Stenotrophomonas sp. strain M212 with a masks-degrading ability was screened from these functional microorganisms, further establishing the role of the gut microbiome.

Anaerobic biodegradation is the most affordable method for the degradation of N,N-dimethylformamide. However, the degradation efficiency depends on the concentration. To elucidate the responses of microbial community to N,N-dimethylformamide load, microbial diversity, composition and functional changes at different concentrations of 100, 2000, and 3500 mg/L were analyzed. Results showed that as the N,N-dimethylformamide influent concentration increased from 100 to 2000 mg/L, the removal rate stabilized at 90%, whereas it decreased to ~75% at concentrations over 2000 mg/L. Microbial community diversity increased, and specialists were enriched at 3500 mg/L. Patescibacteria (42.88% and 42.90%), Bacillota (18.52% and 18.54%), and Pseudomonadota (7.13% and 7.09%) were the dominant phyla at 100 mg/L and 2000 mg/L, respectively, and Patescibacteria (16.88%) and Pseudomonadota (15.34%) were the dominant phyla at 3500 mg/L. Methylotrophic methanogeneic (Methanolobus and Methanomassiliicoccus) and syntrophic electron-donating bacteria (Clostridium and Trichococcus) were significantly enriched. DMF-degrading genes (fdh, rfA/nrfH, and ATPase) and methylotrophic methanogenesis genes (mcr, mta, and mtm) were significantly upregulated. Therefore, the degradation of N,N-dimethylformamide was characterized by a parallel carbon flux distribution, “methylamine-driven methanogenesis + further oxidation/integration of single-carbon intermediates”, and the nitrogen flux tended to enter a reductive nitrogen cycle characterized by retention and reuse.