Gut Microbiota Diversity and Human Diseases: Should We Reintroduce Key Predators in Our Ecosystem?

Abstract

Most of the Human diseases affecting westernized countries are associated with dysbiosis and loss of microbial diversity in the gut microbiota. The Western way of life, with a wide use of antibiotics and other environmental triggers, may reduce the number of bacterial predators leading to a decrease in microbial diversity of the Human gut. We argue that this phenomenon is similar to the process of ecosystem impoverishment in macro ecology where human activity decreases ecological niches, the size of predator populations, and finally the biodiversity. Such pauperization is fundamental since it reverses the evolution processes, drives life backward into diminished complexity, stability, and adaptability. A simple therapeutic approach could thus be to reintroduce bacterial predators and restore a bacterial diversity of the host microbiota.

Keywords: Bdellovibrio bacteriovorus; chronic human conditions; dysbiosis; ecosystem; predator; western lifestyle.

Figure 1

Associative links between Western lifestyle, Human conditions, and loss of microbial diversity (LOMD). On one hand, most of the Human diseases affecting westernized countries are associated with LOMD and on the other hand, some western lifestyle patterns cause LOMD. Then, LOMD appears to play a central role linking western lifestyle and western chronic human conditions (see also Table 1). ^*LOMD not assessed.

Figure 2

Environmental factors reduce microbial diversity because of the loss of predatory species. Gut microbiota may be seen as a complex network of many interacting species (nodes) with several kinds of interactions (links). Predators (in red) are key species that maintain the diversity of the microbiota by direct impact on preys (yellow) and indirect effect on other related species (blue). According to Voltera equations, loss of predators causes an increase number of preys but a loss of diversity. We propose that in industrialized countries environmental risk factors reduces the predators in the network causing LOMD.

Figure 3

Mapping concept of microbiota dysbiosis and resilience. (A) In a healthy state, the gut microbiota ecosystem (represented by a ball) is in a steady state (H). The depth of the well in which the ball is located represents its resilience (R). In case of disturbance (d; i.e., ATB course or digestive infection), the gut microbiota changes (H′) and then get back to its anterior state (H). (B) Environmental factors (i.e., western lifestyle) negatively impact the diversity of the microbiota resulting in a decrease of resilience (R′ < R). However, the microbiota still remains in an apparent healthy state, due to the functional redundancy of the ecosystem (H). (C) But in this new situation, the same disturbance (d) results in a shift of the gut microbiota balance to an other state called dysbiosis (D). This new state is also a steady state, but it impacts negatively the individual condition. It represents an “unhealthy” state. (D,E) “Rebiosis” with respective effect of probiotics administration and fecal transplantation on the the gut microbiota ecosystem. A single strain (probiotic) fails to restore a “healthy” ecosystem (D), but a radical change of the ecosystem through fecal transplantation could be able to achieve this goal (E). p, probiotics; FT, Fecal Transplant.