ABSTRACT
This chapter provides an overview of the composition of the resident microbiotas of the barrier epithelia of the human body based on the use of modern molecular techniques that employ deep sequencing of 16S ribosomal ribonucleic acid. The microbiotas contain transients, allochthonous, members that are not permanent residents but come from other sites or other individuals. Resident microbiotas are generally commensal or mutualistic and exist in a state of dynamic equilibrium with the human host. The composition of the neonatal large bowel microbiota as determined from faeces samples is a function of whether the neonate is delivered vaginally or by caesarean delivery, and this is likely true for the microbiotas at other barrier epithelia. Despite the many variables that contribute to the development of the gut microbiotas of adults, the inter-individual composition of the microbiotas at the phylum level are quite stable, but there is considerable variability at the species level.
