Egalitarianism in Biofilms
Microbial biofilms are multicellular communities of sessile microorganisms encased by the hydrated polymeric matrix. They have significant influences on both aquatic/terrestrial ecosystem and anthropogenic activities. Taking advantage of the governing features of selective stress (Tan and Ng in Water Res 42:1122–1132, 2008; Wei in Water Res 45:863–871, 2011; Dereli in Water Res 59C:11–22, 2014), the evenness of microbial communities in a membrane-centered mesocosm was successfully manipulated. By measuring the biofilm growing rates under different evenness levels of communities, an evenly distributed community favors the formation of biofilms was observed. This finding is not only a new evidence linking biofilm diversity to its functionality but also a clear suggestion on controlling a biofilm-based process via a simple and smart way.
KeywordsBiofouling Biofilm Microbial ecology Community evenness
In 1912, Corrado Gini presented the Gini coefficient (GC) to define the inequality of social income. Since then, the interpretation of this economic concept has been extended to a wider area of science such as medicine , chemistry , and ecology . Ecologists adopted the concept of GC to describe the equality of species in an ecosystem . It is a single value that describes a specific degree of evenness ranging from 0 to 1 . An absolutely even community (GC = 1) is defined as a one in which each species is equally abundant, while the community is extremely uneven (GC is close to zero) when a single species is the only dominant one in the community .
Microorganisms always choose to develop an intricate aggregate (biofilms) onto a surface with supply of nutrients and water [8, 12, 16, 17]. It is ubiquitous in many ecosystems and has been hot topics in microbial ecology for a long time [3, 4]. A lot of factors have been proved to affect the growing features of biofilms . However, less is known on how the community biodiversity, as a response to environmental perturbations, reflects the growing status of biofilms. Recent studies have revealed a close relationship between community evenness and its functional stability , indicating that a community evenness could be an important factor governing the growing of biofilms. In this study, the growing rates of biofilms under different evenness levels were measured by manipulating the evenness levels of their communities in a mesocosm based on the selective stresses principle.
This study hints to not ignore the egalitarianism of microorganisms when studying biofilms, and the conclusion would benefit biofilm-based industrial applications. For example, for some wastewater treatment technologies relying on the formation of biofilms , we need to maintain the system with high evenness of microbial community. On the opposite, for a membrane bioreactor, a widely applied technique that is hindered by unwanted biofilms (i.e., membrane fouling) , an uneven microbial community might contribute to slow down the biofilm-forming processes. An in-depth understanding of the relationship of biofilm formation and its community features enables us to better design biofilm-based bioprocesses in future. Hence, from an ecology perspective, biofilm formation could be controlled based on the evenness of microbial community.
D.G. designed the experiments. Y.F. performed the experiments. D.G., Y.T., Y.F., and H.L. analyzed the data. D.G. and Y.T. wrote the manuscript.
This research was supported by the Natural Science Foundation of Heilongjiang Province (No. ZD201412) and the National Natural Science Foundation of China (No. 21177033).
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Conflict of Interest
The authors declare that they have no conflict of interest.