# Microbial community and functions involved in smokeless tobacco product: a metagenomic approach

## TL;DR

This study explores the microbial communities in Indian smokeless tobacco products and their role in producing harmful compounds like tobacco-specific nitrosamines.

## Contribution

The first shotgun metagenomic analysis of Indian smokeless tobacco products to identify microbial functions linked to carcinogen synthesis.

## Key findings

- Microbial populations in smokeless tobacco products are dominated by Actinobacteria, Proteobacteria, and Firmicutes.
- Functional genes related to nitrogen metabolism and antibiotic resistance were identified in the STP microbiome.
- Mainpuri Kapoori tobacco had high levels of ochratoxins-A, while Moist-snuff and others had elevated TSNAs and zinc.

## Abstract

Smokeless tobacco products (STPs) are attributed to oral cancer and oral pathologies in their users. STP-associated cancer induction is driven by carcinogenic compounds including tobacco-specific nitrosamines (TSNAs). The TSNAs synthesis could enhanced due to the metabolic activity (nitrate metabolism) of the microbial populations residing in STPs, but identifying microbial functions linked to the TSNAs synthesis remains unexplored. Here, we rendered the first report of shotgun metagenomic sequencing to comprehensively determine the genes of all microorganisms residing in the Indian STPs belonging to two commercial (Moist-snuff and Qiwam) and three loose (Mainpuri Kapoori, Dohra, and Gudakhu) STPs, specifically consumed in India. Further, the level of nicotine, TSNAs, mycotoxins, and toxic metals were determined to relate their presence with microbial activity. The microbial population majorly belongs to bacteria with three dominant phyla including Actinobacteria, Proteobacteria, and Firmicutes. Furthermore, the STP-linked microbiome displayed several functional genes associated with nitrogen metabolism and antibiotic resistance. The chemical analysis revealed that the Mainpuri Kapoori product contained a high concentration of ochratoxins-A whereas TSNAs and Zink (Zn) quantities were high in the Moist-snuff, Mainpuri Kapoori, and Gudakhu products. Hence, our observations will help in attributing the functional potential of STP-associated microbiome and in the implementation of cessation strategies against STPs.

•Smokeless tobacco contains microbes that can assist TSNA synthesis.

•Antibiotic resistance genes present in smokeless tobacco-associated bacteria.

•Pathogens in STPs can cause infections in smokeless tobacco users.

The online version contains supplementary material available at 10.1007/s00253-024-13156-9.