Abstract
Coculture is an important model system in microbial ecology studies. As a key experimental parameter, the initial inoculation ratio has a crucial impact on the results of the coculture system. However, such an effect has never been investigated under multiple niche conditions. In this study, we established a simple coculture system with two model bacteria in various carbon sources and investigated the influence of initial inoculum ratios of 1:1000 to 1000:1 on community structure, function, and bacterial interaction. We found that the final ratio of the cocultures with different initial inoculum ratios differed in approximately five-sixths of the carbon sources, suggesting that the final ratio is highly dependent on the initial inoculum ratio, while the carbon source preferences of bacteria could not predict the final ratio of cocultures. Furthermore, we found that the initial ratio could regulate the metabolic capacity of the coculture, as only cocultures with initial ratios of 1:1 and 1000:1 gained high capacity on 14 specific carbon sources. The underlying reason may be that the pattern of species interaction is changed by the initial ratio. In conclusion, we showed that the initial ratio can induce emergent properties in coculture. These findings suggest that the initial ratio not only impacts the reproducibility of coculture experiments but also can influence our understanding of generic microbial ecology.
Highlights
The application of bacterial coculture or synthetic bacterial communities is extensive in microbial ecology studies [1]
We found that the frequency of E. coli-preferred carbon sources was higher than that of P. putida-preferred among the nonsignificant results (Fig. 2, see Fig. S2 for complete results of all carbon sources)
The current study investigated the effect of initial inoculation ratios on the final function and structure of bacterial cocultures
Summary
The application of bacterial coculture or synthetic bacterial communities is extensive in microbial ecology studies [1]. Coculture systems have played a fundamental role in studying species interactions [2,3,4,5,6,7], the development of multispecies biofilms [8,9,10], the regulation of bacterial community dynamics [11,12,13], and the construction of synthetic communities with specific functionalities [14,15,16,17].
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