The impact of horizontal gene transfer on the adaptive ability of the human oral microbiome

Abstract

The oral microbiome is composed of a multitude of different species of bacteria, each capable of occupying one or more of the many different niches found within the human oral cavity. This community exhibits many types of complex interactions which enable it to colonize and rapidly respond to changes in the environment in which they live. One of these interactions is the transfer, or acquisition, of DNA within this environment, either from co-resident bacterial species or from exogenous sources. Horizontal gene transfer in the oral cavity gives some of the resident bacteria the opportunity to sample a truly enormous metagenome affording them considerable adaptive potential which may be key to survival in such a varying environment. In this review the underlying mechanisms of HGT are discussed in relation to the oral microbiome with numerous examples described where the direct acquisition of exogenous DNA has contributed to the fitness of the bacterial host within the human oral cavity.

Insights into the Evolution of Host Association through the Isolation and Characterization of a Novel Human Periodontal Pathobiont,Desulfobulbus oralis

“…Horizontal gene transfer is an important factor influencing the human oral microbiota and its individual species' positive and negative interactions with the host (56,57). Based on sequence similarity and phylogenetic analyses, we found evidence for multiple horizontal gene transfer events.…”

Extracellular DNA in oral microbial biofilms

“…Competence for genetic transformation is a tightly controlled process, and incorporation of novel genetic material is a relatively rare event. Nevertheless, the genomes of many oral bacteria including streptococci and P. gingivalis show evidence of extensive genetic recombination and horizontal gene transfer, indicating that eDNA uptake has likely driven the evolution of many different oral bacteria [65]. Worryingly, penicillin resistance in S. pneumoniae appears to have arisen from the transfer of portions of the pbp2x gene from S. mitis and/or S. oralis [66].…”

Genomes of Gardnerella Strains Reveal an Abundance of Prophages within the Bladder Microbiome

“…Prior studies have posited that lysogenic lactobacilli phages could contribute to a shift in the vaginal microbiota leading to BV (for a review, see [4]). Phages have been found to play a crucial role in the structuring of microbial communities, including those residing within the human body [24], driving bacterial genetic diversity [25] and adaptation to changes in the environment [26]. Although several phages induced from vaginal lactobacilli have been identified [27–28], currently no phages have been characterized for Gardnerella .…”

“…While evidence suggests that phages are likely contributors to HGT in commensal communities (e.g. [22,26] and review [29]), the extent of their effect on the human microbiome is just now being explored (e.g., [30–32]). Within many other microbiota, including the bladder, the virome remains largely unexplored.…”