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bioRxiv · 10.64898/2026.11.07.764895

41% of Gram-negative bacteria encode a Type Six Secretion System

Zhang, C.·Hassler, H.·Ratcliff, W.·Speare, L.·Hammer, B. K.
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Abstract

The type six secretion system (T6SS) is a highly studied, versatile bacterial nanoweapon that is important in bacterial pathogenesis and evolution. Despite extensive study, its prevalence remains poorly quantified. Analyzing 35,467 representative genomes, we find that approximately 41% of genomes in the average well-sampled Gram-negative genus (more than 30 sampled genomes) encode a T6SS. Further, we show that the distribution of the T6SS is patchy at all taxonomic levels. The uneven distribution we found is consistent with context-dependent selection, repeated evolutionary loss, or greater evolutionary lability. Our dataset provides a foundation for studying the drivers of T6SS distribution, and our pipeline enables similar surveys of other secretion systems, gene clusters, and multi-protein complexes across bacteria.

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Zhang, C., Hassler, H., Ratcliff, W., Speare, L., Hammer, B. K.. 2026-11-09. 41% of Gram-negative bacteria encode a Type Six Secretion System. https://doi.org/10.64898/2026.11.07.764895

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