Sociology

Population

Bacteria

Biology

Microbiology

Host (biology)

Demography

Vibrio

Ecology

Symbiosis

Secretion

Genetics

Biochemistry

Competition (biology)

Proceedings of the National Academy of Sciences

Significance Competition among cooccurring bacteria can change the structure and function of a microbial community. However, little is known about the molecular mechanisms that impact such interactions in vivo. We used the association between bioluminescent bacteria and their squid host to study how environmentally transmitted bacteria compete for a limited number of host colonization sites. Our work suggests that Vibrio fischeri use a type VI secretion system, acting as a contact-dependent interbacterial “weapon,” to eliminate competing strains from cooccupying sites in the host. This work illuminates a mechanism by which strain-specific differences drive closely related bacteria to engage in lethal battles as they establish a beneficial symbiosis, revealing how genetic variation among potential colonizers directly impacts the spatial structure of the host-associated population.

Bacterial symbionts use a type VI secretion system to eliminate competitors in their natural host