FIG 8.

Conceptual model for the role of viscosity in modulating V. fischeri cell-cell contact and T6SS2 activity. In a low-viscosity, liquid environment, V. fischeri cells are physically dispersed and T6SS2 is functionally and transcriptionally inactive. High-viscosity medium facilitates cell-cell contact between different genotypes: high-viscosity liquid promotes the formation of mixed-strain aggregates by V. fischeri, while surfaces force cells into physical contact. High-viscosity and surface conditions promote increased T6SS2 expression, sheath assembly, and T6SS2-dependent killing.