Membrane proteins of Pseudoalteromonas tunicata during the transition from planktonic to extracellular matrix‐adherent state

Abstract

Pseudoalteromonas tunicata is a marine bacterium that was originally isolated from the surface of the tunicate Ciona intestinalis. Since C. intestinalis expresses extracellular matrix (ECM) and P. tunicata has a gene encoding a functional ECM-binding protein, we hypothesized that P. tunicata could adhere to this host via protein-ECM interactions and as a result change its membrane proteome. An in vitro adhesion assay was developed to show that P. tunicata adheres strongly to ECM. To further study the adhesion biology of P. tunicata, two-dimensional (2D) electrophoresis was used to explore the membrane-associated sub-proteome of P. tunicata during planktonic, adherent and non-adherent states. More than 30 proteins were resolved using blue native (BN)/SDS 2D PAGE, many of which were identified by mass spectrometry. BN/SDS PAGE also allowed the identification of several novel protein complexes, which indicate structural and functional relationships for these proteins and related proteins in several other organisms. A proteomic change associated with adhesion was identified by comparison of 2D gels from the three model states. Collectively, these studies explore the membrane proteome of P. tunicata during the transition from planktonic to ECM-adherent states.

Proteomic studies highlight outer‐membrane proteins related to biofilm development in the marine bacterium Pseudoalteromonas sp. D41

“…Previous proteomic analyses in two distinct Pseudoalteromonas species detected the upregulation of TBDR during biofilm development . Moreover, a recent study in P. tunicata identified the increase of a TBDR associated to the ECM adhesion . In agreement to these findings, we speculate that the strong TBDR induction in Pseudoalteromonas sp.…”

“…D41 TBDR could be involved in sugar transport. Previous proteomic analyses in two distinct Pseudoalteromonas species detected the upregulation of TBDR during biofilm development . Moreover, a recent study in P. tunicata identified the increase of a TBDR associated to the ECM adhesion .…”

“…Additionally, the heterologous expression in Escherichia coli of the P. tunicata protein PTD2‐05920 allowed to show that it is an ECM‐interacting protein . Recently, a proteomic approach highlighted the increased abundances of a wide variety of TonB‐dependent receptors (TBDRs) in the membrane fraction of P. tunicata , in association to its transition from planktonic to ECM‐adherent state . A better knowledge of these mechanisms in marine bacteria is a prerequisite to understand their adhesion behavior on solid surfaces.…”

An ortholog of the Leptospira interrogans lipoprotein LipL32 aids in the colonization of Pseudoalteromonas tunicata to host surfaces

“…Changes in the membrane proteome of P. tunicata between cells grown on either BSA-coated or ECM-coated surfaces have recently been observed (Hoke et al, 2011) and therefore it is likely that P. tunicata utilizes a distinct subset of proteins to adhere to different surfaces. Thus the available data suggests a conserved function for LipL32-like proteins in facilitating interaction with ECM structures (Hauk et al, 2008; Hoke et al, 2008), a novel finding given the absence of an overlapping niche between P. tunicata and Leptospira species.…”

“…P. tunicata rapidly attaches to ECM structures (Hoke et al, 2011) and the tunicate, C. intestinalis , a natural host of P. tunicata , possesses the genes necessary for ECM synthesis, including those encoding for collagen type IV, fibronectin, laminin, and nidogen (Huxley-Jones et al, 2007). In addition, Ulva liza , a close relative of U. australis , possesses the genes encoding ECM-like proteins, including collagen (Stanley et al, 2005).…”