Abstract
Biofilms are microbial communities embedded in extracellular matrix. Exopolysaccharide Psl (ePsl) is a key biofilm matrix component that initiates attachment, maintains biofilms architecture, and protects bacteria within biofilms of Pseudomonas aeruginosa, an opportunistic pathogen. There are at least 12 Psl proteins involved in the biosynthesis of this exopolysaccharide. However, it remains unclear about the function of each Psl protein and how these proteins work together during the biosynthesis of ePsl. PslG has been characterized as a degrader of ePsl in extracellular or periplasm and PslD is predicted to be a transporter. In this study, we found that PslG and its glycoside hydrolytic activity were also involved in the biosynthesis of ePsl. PslG localized mainly in the inner membrane and some in the periplasm. The inner membrane association of PslG was critical for the biosynthesis of ePsl. The expression of PslA, PslD, and PslE helped PslG remain in the inner membrane. The bacterial two‐hybrid results suggested that PslE could interacted with either PslA, PslD, or PslG. The strongest interaction was found between PslE and PslD. Consistently, PslD was disabled to localize on the outer membrane in the ΔpslE strain, suggesting that the PslE‐PslD interaction affected the localization of PslD. Our results shed light on the assembly of ePsl biosynthesis machinery and suggested that the membrane‐associated PslG was a part of ePsl biosynthesis proteins complex.
Highlights
Structured, surfaced‐associated communities of bacteria known as biofilms are prevalent in nature, industrial, and clinical settings (Costerton, Lewandowski, Caldwell, Korber, & Lappin‐Scott, 1995; Stoodley, Sauer, Davies, & Costerton, 2002)
Biofilm matrix, which plays a key role in biofilm development, is extracellular substance secreted by biofilm bacteria
To figure out any Psl protein affecting the localization of PslG, we focused on proteins PslA, PslD, and PslE, which were predicted to be localized on the inner membrane and possessed periplasmic domains (Franklin et al, 2011)
Summary
Structured, surfaced‐associated communities of bacteria known as biofilms are prevalent in nature, industrial, and clinical settings (Costerton, Lewandowski, Caldwell, Korber, & Lappin‐Scott, 1995; Stoodley, Sauer, Davies, & Costerton, 2002). There are at least three unique exopolysac‐ charides implicated in P. aeruginosa biofilm development, alginate, ePsl, and Pel (Branda, Vik, Friedman, & Kolter, 2005; Colvin et al, 2012; Ma, Jackson, Landry, Parsek, & Wozniak, 2006; Ramsey & Wozniak, 2005). Twelve proteins are required for the biosynthesis of alginate (Chitnis & Ohman, 1993; Franklin, Nivens, Weadge, & Howell, 2011). They have been characterized to elucidate the alginate biosynthetic mechanism, including polymerization, epi‐ merization, acetylation, secretion, and regulation (Franklin et al, 2011; Moradali, Donati, Sims, Ghods, & Rehm, 2015; Rehman, Wang, Moradali, Hay, & Rehm, 2013). We further investigate the role of PslG and its hy‐ drolytic activity on the biosynthesis of ePsl in P. aeruginosa PAO1. Our results shed light on the assembly of ePsl biosynthesis machinery
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