Type 6 secretion dynamics within and between bacterial cells

Abstract

The bacterial type 6 secretion system (T6SS) functions as a virulence factor capable of attacking both eukaryotic and prokaryotic target cells by a process that involves protein transport through a contractile bacteriophage tail-like structure. The T6SS apparatus is composed, in part, of an exterior sheath wrapped around an interior tube. Here, we report that in living cells the cytoplasmic adenosine triphosphatase called ClpV specifically recognizes the contracted T6SS sheath structure, causing its disassembly within seconds. ClpV imaging allowed spatial and temporal documentation of cell-cell interactions (termed T6SS dueling) that likely mark the location of repeated T6SS-mediated protein translocation events between bacterial cells.

Figure 1. ClpV co-localizes with contracted sheath

3×3 µm field of cells is shown. Bar in A is 1 µm and applies to A–D. (A–C) V. cholerae ClpV-mCherry2 + pBAD24-VipA-sfGFP. (A) merge of ClpV-mCherry2 and VipA-sfGFP signals. (B) ClpV-mCherry2 signal. (C) VipA-sfGFP signal. Additional frames and cells are shown in Videos S2 and S3. (D) P. aeruginosa ΔretS/ClpV1-GFP, additional frames and cells are shown in Videos S6 and S7.