Some microorganisms push others out of the way to gain better access to oxygen.

Wook Kim and Kevin Foster at the University of Oxford, UK, studied the soil bacterium Pseudomonas fluorescens, which grows in dense layers called biofilms.

They found that a strain that consistently outgrew others and dominated the colony carried a mutation in a gene called rsmE. This mutant strain secretes polymers that expand, nudging neighbours aside and allowing cells to reach the colony surface where they can receive the most oxygen.

Life in tightly packed communities has selected for this bacterial pushiness, the authors say.

Proc. Natl Acad. Sci. USA (2014)