Lipooligosaccharide Core Truncations Affect the Ability of <i>Campylobacter</i> <i>jejuni</i> to Attach to Glass and Form Biofilms under Aerobic Conditions

Abstract

The aim of this study was to investigate the effects of lipooligosaccharide (LOS) core truncations on the ability of Campylobacter jejuni to attach to glass and form biofilms under aerobic conditions. We compared the wild-type and previously constructed glycosyltransferase mutants of two C. jejuni strains, NCTC 11168 and 81-176, in terms of the numbers of attached cells, biofilm formation, autoagglutination (AAG) activity, and extracellular DNA (eDNA) release. All LOS mutants of NCTC 11168, except cj1138 mutant, and 81-176 waaC mutant with most severe LOS truncation, exhibited increased attachment and biofilm formation. Conversely, waaC and lgtF mutant of both NCTC 11168 and 81-176 showed significantly reduced AAG activity. There was no significant difference between all LOS mutants and the wild-type with respect to eDNA production. The biofilm formation levels correlated significantly with the attachment numbers (p < 0.05, R2 = 0.95) but not with the AAG activity and eDNA levels (p ≥ 0.48, R2 ≤ 0.72). These results suggest that various LOS core truncations have different impacts on C. jejuni attachment, biofilm formation under aerobic conditions, and the AAG activity levels, whereas they may not affect eDNA production. Bacterial attachment, but not the AAG activity and eDNA release levels, may cause changes in C. jejuni biofilm formation because of LOS core truncations. Discipline: Food Additional key words: Autoagglutination activity, extracellular DNA release * Corresponding author: akiba@affrc.go.jp † Taketoshi Iwata and Vu Tuan Nguyen contributed equally to this study Received 15 August 2014; accepted 24 December 2014. Introduction Campylobacter jejuni is an important foodborne bacterial pathogen, which is frequently associated with gastrointestinal diseases in humans worldwide (Kirkpatrick & Tribble 2011). Attachment to abiotic surfaces plays an important role in the survival of C. jejuni in food systems and the environment, thereby leading to infections (Nguyen et al. 2012). Because of the importance of bacterial attachment, we previously investigated factors that potentially influence the ability of C. jejuni to attach to abiotic surfaces, thereby elucidating the mechanisms of attachment. We found that cell surface hydrophobicity affected the ability of many C. jejuni strains to attach to abiotic surfaces such as stainless steel and glass (Nguyen et al. 2011). Although it has been suggested that capsular polysaccharides (CPS) and lipooligosaccharides (LOS) contribute to the degree of hydrophobicity of various bacteria (Guerry & Szymanski 2008), CPS removal and LOS core truncation caused by kpsE and waaF mutation, respectively, did not affect cell surface hydrophobicity and attachment in C. jejuni (Nguyen et al. 2013). Various LOS core truncations caused by the mutation of various genes encoding heptose biosynthesis enzymes and glycosyltransferases were found to increase the cell surface hydrophobicity of both C. jejuni NCTC 11168 and 81-176 strains (Iwata et al. 2013). However, it is currently unknown whether LOS core truncations in these sugars affect the attachment ability of C. jejuni. In addition to surface attachment, biofilm formation by C. jejuni has a role in enhanced survival (Joshua et al. 2006,