Intestinal Bacteria: Stability of Some Bacterial Groups Good for Health

Intestinal bacteria can be either good or bad for health and a recent study showed that the stability of some bacterial groups is what is important. Some have referred to the microorganisms that live in the gut as an ecosystem. This means that there are many kinds of bacteria and other microbes that share the space and they interact with each other in many ways. Scientists have not learned how the ecosystem of bacteria in the gut, technically called the microbiome, is controlled. Overgrowth of some microorganisms can mean the depletion of others. A healthy gut is comprised of the right composition of the various kinds of bacteria and ill health can result if the composition is off kilter.
In a recent study reported in Nature Communications, researchers from the University of Helsinki in Finland and Wageningen University in the Netherlands analyzed the microbial ecosystem of the intestines of 1,000 subjects. They found that there is a bimodal distribution (two bumps in the curve) of some types of bacteria, which means that there is either a lot of the bacteria or only a little. They studied a total of 130 different types of bacteria and only some existed in a bimodal distribution where the bacteria was either abundant in most individuals or nearly absent.
What the scientists who carried out this study were interested in was abrupt switches between otherwise stable states. A concept in ecology is that, when in equilibrium, alternative stable states are separated by a tipping point. If the tipping point is breached, one stable state takes over and the other is defeated. An interesting point about the study is they applied a type of analysis that is normally used in climatology and forest ecosystems to study shifts. Specifically, they used a method for studying “stochastic dynamical systems.” Stochastic means the dynamics come from the accumulation of random variables and not deterministic events that build up in one direction.
A state of abundance or depletion of these bacteria was shown to be not affected by what one eats and the bacterial state varied independently from food intake. What seems to be determining whether the bacteria was in either the abundant or depleted state was more macro-scale factors, such as age and being overweight.
The authors of the study have proposed that the bistable groups of bacteria indicate the tipping elements of the intestinal microbial community. Tipping here means going one way or the other. The authors also proposed that the transitions in these bacterial populations; that is, hitting the tipping point, may be what is key in determining a state of ill-health. Stability of the distributions of these bacteria is associated with a state of health.
An implication of the results from this study is that analyzing the microbial distributions in the intestines may provide some diagnostic value in clinical settings. Looking for instability in the intestinal ecosystem may be an indicator of impending health problems. Rather than trying to analyze the entire microbial community in the intestines of an individual, which would be a very daunting task, a clinician could just analyze the distributions of a few types of bacteria. Stability in some types of intestinal bacteria seems to be the goal for good health.

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