Alterations in the intestinal microbiome and mental health status of workers in an underground tunnel environment

Abstract

Background: Working in an underground tunnel environment is unavoidable in professions such as miners and tunnel workers, and there is a concern about the health of these workers. Few studies have addressed alterations in the intestinal microbiome of workers within that environment.

Results: Fecal samples were collected from the workers before they entered the tunnel (baseline status, BS) and after they left the tunnel (exposed status, ES), respectively (a time period of 3 weeks between them). We analyzed 16S rRNA sequencing to show the changes in microbial composition and self-evaluation of mental health questionnaire was also performed. The results showed that Shannon and Simpson indices decreased significantly from BS to ES. A higher abundance was found in the phylum Actinobacteria, classes Actinobacteria and Deltaproteobacteria, orders Bifidobacteriales, Coriobacteriales, and Desulfovibrionales, families Bifidobacteriaceae, Peptostreptococcaceae, Coriobacteriaceae, Clostridiaceae_1, Desulfovibrionaceae, Pseudomonadaceae, and Microbacteriaceae, and genera Bifidobacterium, Romboutsia, Clostridium sensu stricto, and Leucobacter in ES, while BS showed greater levels of genera Faecalibacterium and Roseburia. The self-evaluation showed that at least one-half of the tunnel workers experienced one or more symptoms of mental distress (inattention, sleeplessness, loss of appetite, headache or dizziness, irritability) after working in the underground tunnel environment.

Conclusions: Collectively, the underground tunnel environment led to alterations in the intestinal microbiome, which might be relevant to symptoms of mental distress in underground-tunnel workers.

Keywords: 16S rRNA; Brain-gut-microbiota axis; Gut microbiome; Mental distress; Underground tunnel environment.

Fig. 1

a Microbial alpha diversity in ES and BS. Boxplot showed greater gut microbial diversity in BS than ES according to Shannon (t = 3.375, P = 0.001) and Simpson (t = 2.757, P = 0.008) indices with paired samples t-test. b Microbial beta diversity. Principal coordinate analysis (PCoA) of ES compared to BS based on Bray-Curtis dissimilarities in the relative abundance of ASVs (PERMANOVA, R² = 0.028, P = 0.002)

Fig. 2

Bacterial community structural composition and distribution. Dominant bacterial composition detected in each sample and two status were showed with overlapping histogram at five taxonomical levels (phylum, class, order, family, genus)

Fig. 3

LEfSe and LDA analysis revealed changes in the taxonomic composition of the gut microbiota in ES compared to BS tunnel workers. a LDA scores showing the biomarker taxa (LDA score of > 3.5 and a significance of P < 0.05 determined by the Wilcoxon signed-rank test) for ES (red) and BS (green). b Cladogram showing the relationship between taxon (the levels represent, from the inner to outer rings, phylum, class, order, family, and genus) in ES (red) and BS (green). c Difference features histogram in a panel showed relative abundance of mental disorders-related biomarker taxa. The straight and dotted lines plot means and medians of the relative abundance, respectively, in each subgroup

Fig. 4

Sankey diagram of the consistency in current study with published literatures. Left side mainly showed the changes of four critical intestinal microbiome in both current study and published literatures. Middle and Right side represented the result of mood disorder in specific literature