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Diverse communities of bacteria and humans – lessons learnt

Jithin Sunny & Bins Sebastian

Do bacteria derive benefits by living in diverse communities? How is this important for ecological balance? Jithin Sunny, a PhD scholar in the Department of Biotechnology, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, has often wondered about the philosophical takeaways from his research on bacterial population study. Together with Bins Sebastian, assistant professor in the Department of Philosophy, Madras Christian College, Chennai, he discusses a vital question Can an invisible yet significant group of living organisms give us lessons on our society and the interactions within?’

Community analysis of an unseen world
Community analysis of an unseen world  (Photo: Anurup Mohanty)

What is a community?

A community is a group of co-occurring and interacting species at a given time and place. It is a dynamic entity, with members interacting within the population as well as with their surroundings. A community has some chief characteristic elements. It comprises a group of individuals, has a defined boundary, has a level of similarity amongst the members, uses various communication methods, and possesses skills and resources that can be utilised by its members. 

Behaviours in a bacterial community

The qualities of a community also apply to bacterial communities. Bacterial species are the most diverse organisms. They are found everywhere, even in the most extreme environments such as glaciers, ice caps, thermal springs, hydrothermal vents, and ocean floors. Bacterial species are rarely found in isolation. Often, they survive as part of a population which comprises multiple species. Interactions occur between various species through behaviours such as neutralism, commensalism, amensalism, mutualism, parasitism, and competition. Years of co-evolution has led to a large variety of these relationships.

These interactions have been studied in a pairwise setup. However, a stable community is the result of all the collective behaviours. In other words, the aggregate activity of individual cells determines the ability of a community to accomplish a particular function. It is a very difficult process to observe community dynamics in real time. However, computer simulations have often been performed on two-species systems, which have shed light on changes in population structures. Under identical parameter conditions such as nutrients and space, it has been observed that behaviours such as neutralism and mutualism show balanced population structures. These so-called symmetrical interactions have almost the same abundance of both species. Co-operation is thus seen as a fundamental requirement in bacterial communities, and such communities can have several positive effects. 

Is a diverse community better?

The co-operation within a diverse community has far-reaching consequences. Bacterial diversity has proved important for ecological balance. Soil nutrient cycling is important for maintaining crop growth, and studies have shown that diverse bacterial populations are a necessary requirement for a good crop yield. A higher enzyme activity and increased mineralization are some characteristics of a bacterial community, which can lead to better plant growth. In fact, a study points out that plant species richness is directly proportional to the soil bacterial diversity. A strong relationship exists between bacterial diversity and stability of the environment. The impact of a diverse community on several ecological processes is more significant than previously thought. 

When it comes to human health, research on the positive effects of bacterial diversity has brought out interesting observations. In a recent study by Rebecca M. Rodriguez et al., a higher bacterial diversity shows correlation with the overall survival of cancer patients. The highly-diverse bacterial community that inhabits our body has a positive effect on inflammation and immune responses. A study by Ying et al. shows the effect of a diverse community on the mortality rate in hematopoietic stem cell transplantation. A substantial disturbance in these communities can disturb the maintenance of a healthy state and directly increase the risk of diseases. 

Thus, the aggregate of positive interactions in a bacterial community can be seen as beneficial, not only for the community itself but also the surroundings it interacts with. 

Our takeaway

The observations from these micro-level environments can be representative of higher order functioning. Our understanding of community functioning leads us to believe that diversity’ can be an innate social virtue and perhaps bacterial communities are not the only ones benefiting from it. 

What exactly is the benefit?

Similar to bacteria, humans too have inherited many traits, leading to the current social structure. Studies show that in the last one million years, humans have evolved the ability to learn from each other to promote a cumulative society. The natural selection of pro-social motives has built an inclusive architecture. The process of cooperation involves reframing one’s perceptions and thought processes, being open to critiques and alternative explanations, performing better as a moral agent, and being tolerant and peace-loving in challenging situations. This can be seen from the fact that humans spend a great amount of time and energy in coping with challenging emotions and challenging others. It helps (in an ideal set-up, it should) individuals to become better persons – intellectually and morally (by practicing and cultivating virtues). In comparison, in a homogenous society, there would be less number of such challenges and hence, less scope for improvement. 

This is similar to results from studies on micro-level cooperative traits in bacterial populations. In this regard, there are many lessons yet to be learned from our microscopic friends.