Competition, not cooperation, dominates interactions among culturable microbial species

Area of Science:

• Microbiology
• Ecology
• Evolutionary Biology

Background:

• Microbial cells release molecules that can benefit neighboring cells, suggesting cooperation within and between species.
• The importance of interspecies cooperation in microbial communities is increasingly recognized.
• A systematic evaluation of mutually positive interactions between different microbial species is lacking.

Purpose of the Study:

• To investigate the prevalence of mutually positive interactions among bacterial strains from a shared aquatic environment.
• To determine if positive interactions increase with species diversity in microbial communities.

Main Methods:

• Analysis of data from two independent experiments assessing community productivity across varying species diversity.
• Examination of pairwise and higher-order species combinations.

Main Results:

• The majority of pairwise bacterial interactions were found to be net negative.
• No significant evidence of strong higher-order positive effects was observed when more than two species were combined.
• While one-way beneficial interactions (e.g., predator-prey) may occur, they do not represent cooperation.

Conclusions:

• Cooperation is not the typical outcome of bacterial interactions in this aquatic environment.
• Competitive interactions appear to be more common than cooperative ones among these microbial species.
• Adaptation to other microbial species more frequently leads to competitive, rather than cooperative, phenotypes.