Ecological Adaptations of Gut Microbiota Members and Their Consequences for Use as a New Generation of Probiotics

Abstract

In this review, we link ecological adaptations of different gut microbiota members with their potential for use as a new generation of probiotics. Gut microbiota members differ in their adaptations to survival in aerobic environments. Interestingly, there is an inverse relationship between aerobic survival and abundance or potential for prolonged colonization of the intestinal tract. Facultative anaerobes, aerotolerant Lactobacilli and endospore-forming Firmicutes exhibit high fluctuation, and if such bacteria are to be used as probiotics, they must be continuously administered to mimic their permanent supply from the environment. On the other hand, species not expressing any form of aerobic resistance, such as those from phylum Bacteroidetes, commonly represent host-adapted microbiota members characterized by vertical transmission from mothers to offspring, capable of long-term colonization following a single dose administration. To achieve maximal probiotic efficacy, the mode of their administration should thus reflect their natural ecology.

Keywords: chicken; gut; human; microbiota; pig; probiotics.

Figure 1

The twenty most abundant bacterial species present in gut microbiota of humans, pigs and chickens. Microbiota composition was determined in 44 human, 50 pig and 37 chicken samples processed in the authors’ laboratory within the last two years, and the most abundant operational taxonomic units (OTUs) were identified. Two Lactobacillus species were common in pigs, while in humans and chickens, not a single Lactobacillus species was present among the twenty most abundant species. Neither Bifidobacterium nor any other Actinobacteria representative was present among the top 20 OTUs in any of these hosts.

Figure 2

Gut microbiota and their adaptation to air survival. There are different forms of adaptation to air exposure. Aerotolerant bacteria or facultative anaerobes survive aerobic exposure in the form of vegetative cells. Another group of gut microbiota survives air exposure in the form of spores. The last group of gut anaerobes, mostly from Bacteroidetes, did not evolve any specific form of air survival and quickly loses viability after air exposure, which negatively affects their transmission via the environment.

Figure 3

Sources of gut microbiota for chickens. Despite continuous supply of aeroresistant gut colonizers from the environment, these usually represent around 50% of microbiota in chickens (or humans or pigs). On the other hand, strict anaerobes without any adaptation to air survival are transferred by less frequent contact, and despite this, usually represent the second half of gut microbiota. If any of the gut microbiota is considered as probiotic, natural ecology and adaptations should be considered and followed.