Our planet boasts of a wide range of microbial species, each of which with their own specific traits and features that set them apart from each other. These differences have baffled scientists for ages, and so have the links between different types of microbes. But a new study might have the answer to some of the more pressing questions about these microscopic creatures — a mathematical model that potentially explains the so-called “paradox of the plankton,” a dilemma first proposed almost 60 years ago by British ecologist G. Evelyn Hutchinson.
As explained by The Hindu, there can be “hundreds, or even thousands” of different microbial species in a single ecosystem, may it be in soil, in water, or even in the gastrointestinal tract. Within these tiny ecosystems, food can be limited, but things can get crowded as the microbes keep growing in number. This, in brief, explains the paradox of the plankton and frames the many questions scientists have had about the behavior of microbes in microscopic ecosystems, including questions about the ability of microbes to survive and remain diverse in such crowded situations, and on how they keep adding up despite the ostensible lack of food.
Explaining the methodologies he used to solve the paradox, National Centre for Biological Sciences doctoral student Akshit Goyal, first author of the new study, told The Hindu that a small percentage of microbial species can be considered “core” species, while the majority are filed under the “peripheral” category. He observed that there are only a few species that are in between those two categories, and when it comes to the prevalence of species, microbial ecosystems tend to form a U-shaped pattern when plotted in graph form.
Additionally, Goyal explained how his team’s food supply model works, stating that microbes oftentimes cannot fully transform food into energy, and end up giving off a certain level of waste. In the case of core and peripheral microbe species, Goyal noted that a core species’ waste byproducts can be used in turn by peripheral species as food.
“These byproducts can sometimes be used as a food source by another species,” said Goyal.
In another interesting note from the study, Goyal and University of Illinois researcher Sergei Maslow wrote that certain conditions can lead to one microbial species displacing another, resulting in “extinction” only if the two species share the same food source. This is in contrast to the theory of competitive exclusion as it stood when Hutchinson proposed the paradox of the plankton in 1961, where only a few dominant species drive others to extinction, instead of many microbial species coexisting within the same ecosystem, according to BioDiverse Perspectives.
In a statement quoted by The Hindu, NCBS cell biologist Mukund Thattai praised Goyal and Maslow’s research on the paradox of the plankton as being capable of explaining the diversity of microbial species within certain ecosystems. However, he added that the new theory is “only one of several” that have sought to explain the cause of microbe diversity.
“The key to discriminating between these ideas would be to not rely on a snapshot, but to actually watch the diversity of a microbiome change over time,” Thattai added.