Molecular analysis of the human faecal archaea in a southern Indian population.

Archaea are an important constituent of the human gut microbiota, but there is no information on human gut archaea in an Indian population. In this study, faecal samples were obtained from different age groups (neonatal babies, preschool children, school-going children, adolescents, adults and elderly) of a southern Indian population, and from a tribal population also resident in southern India). 16S rRNA gene sequences specific to Archaea were amplified from pooled faecal DNA in each group, sequenced, and aligned against the NCBI database. Of the 806 adequate sequences in the study, most aligned with 22 known sequences. There were 9 novel sequences in the present study. All sequences were deposited in the GenBank nucleotide sequence database with the following accession numbers: KF607113 - KF607918. Methanobrevibacter was the most prevalent genus among all the age groups accounting for 98% in neonates, 96% in post-weaning, and 100% each in preschool, school and adult population. In the elderly, Methanobrevibacter accounted for 96% and in tribal adults, 99% of the clones belonged to Methanobrevibacter genus. Other genera detected included Caldisphaera, Halobaculum, Methanosphaeraand Thermogymnomonas. Methanobrevibacter smithii predominated in all age groups, accounting for 749 (92.9%) of the 806 sequences. Archaea can be found in the faeces of southern Indian residents immediately after birth. Methanobrevibacter smithii was the dominant faecal archeon in all age groups, with other genera being found at the extremes of age.