Bioprospecting of 101 facultative rumen bacterial isolates through comprehensive genome analysis

Microbes within the rumen play a pivotal role in the digestion of feed ingested by the ruminants. Researchers have been investigating microbes within rumen to assess its genetic capabilities, which hold immense potential across various fields including agro-industrial advantages. Since rumen is preliminary an anaerobic sac, numerous anaerobic bacteria and fungi have been isolated and characterized, however facultative anaerobic bacteria yet not fully investigated.

In present study, we isolated, characterized and performed whole genome analysis of 101 facultative anaerobic bacteria from rumen, offering a unique perspective compared to metagenomic approaches. All assembled genomes were of high quality, i.e. completeness 100% (only seven were between 92 and 99.5%) and only two had contamination > 5%. We identified 9,542 sequences of Carbohydrate-Active Enzymes (CAZymes). Over 8,136 of these CAZymes were full-length sequences, with 2,048 harbouring signal peptides also. Xylan (n = 634), pectin (n = 604), and starch (n = 312) degrading enzyme sequences were dominant. Several isolates also harbour secondary metabolite biosynthesis gene clusters for various metabolites, including fengycin, lichenysin, bacillibactins, bacilysin etc. All the isolates have metabolic versatility, encompassing pathways such as carbohydrate, amino acid, lipid, and vitamin and cofactor metabolism. Intriguingly, lipoic acid metabolism was absent in most of these facultative bacterial isolates.

This comprehensive study sheds light on the genetic potential of culturable facultative rumen bacteria, emphasizing their pivotal roles in carbohydrate degradation, secondary metabolite production, and metabolic diversity. These findings hold promise for enhancing ruminant nutrition, advancing eco-friendly biomass conversion, and bolstering bioprospecting of industrially important biocules and enzymes biofuel production.