Type VI Secretion System Dynamics Reveals a Novel Secretion Mechanism in Pseudomonas aeruginosa

Abstract

The Type VI Secretion System (T6SS) inhibits growth of neighboring bacterial cells through a contact-mediated mechanism. We describe a detailed characterization of the protein localization dynamics in the T6SS. It has been proposed that Type VI secretion process is driven by a conformational-change induced contraction of the T6SS sheath. However, although the contraction of an optically resolvable TssBC sheath and the subsequent localization of ClpV are observed in, coordinated assembly and disassembly of TssB and ClpV are observed without TssB contraction in These dynamics are inconsistent with the proposed contraction sheath model. Motivated by the phenomenon of dynamic instability, we propose a new model in which ATP hydrolysis, rather than conformational change, generates the force for secretion. The Type VI Secretion System (T6SS) is widely conserved among Gram-negative bacteria and is a central determinant of bacterial fitness in polymicrobial communities. The secretion system targets bacteria and secretes effectors that inhibit the growth of neighboring cells using a contact-mediated-delivery system. Despite significant homology to the previously characterized T6SS, our analysis reveals that effector secretion is driven by a distinct force-generation mechanism in The presence of two distinct force-generation mechanisms in T6SS represents an example of the evolutionary diversification of force-generation mechanisms.

Diverse roles of TssA‐like proteins in the assembly of bacterial type VI secretion systems

“…The sheath dynamics of this cluster is, however, very different from dynamics of sheath assembly of TagA-containing E. coli or V. cholerae clusters. Even though a model excluding sheath contraction was proposed for H1-T6SS (Corbitt et al, 2018), we show here that H1-T6SS sheaths assemble very quickly within 5-20s and immediately contract (Fig 5), which makes it technically challenging to detect the whole sheath assembly, contraction, and disassembly cycle. We also often observed dynamic sheath spots for H1-T6SS, which could be functional contractile sheath assemblies shorter than the diffraction limit of the used fluorescence microscopy technique.…”

The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in Pseudomonas aeruginosa

“…2A ) were downregulated in the mutant. The T6SS, found on three different loci on the chromosome (H1-T6SS, PA0074 to PA0091; H2-T6SS, PA1656 to PA1671; and H3-T6SS, PA2359 to PA2371) target other bacteria by secreting effector proteins that can inhibit or kill them through a contact delivery system ( 41 ). The H2 and H3 systems are important P. aeruginosa pathogenesis mediators ( 42 ).…”

Molecular mechanisms of DNase inhibition of early biofilm formation Pseudomonas aeruginosa or Staphylococcus aureus: A transcriptome analysis

“…Bacterial cells communicate with their surrounding environment through secretion systems. P. aeruginosa is associated with a type VI secretion system [ 31 ] that inhibits the growth of neighboring bacterial cells using a contact-mediated mechanism [ 32 ]. This system is also associated with P. aeruginosa biofilm formation and environmental adaptation [ 33 ].…”