title: Attachment of Salmonella strains to a plant cell wall model is modulated by surface characteristics and not by specific carbohydrate interactions.
abstract: Processing of fresh produce exposes cut surfaces of plant cell walls that then become vulnerable to human foodborne pathogen attachment and contamination, particularly by Salmonella enterica. Plant cell walls are mainly composed of the polysaccharides cellulose, pectin and hemicelluloses (predominantly xyloglucan). Our previous work used bacterial cellulose-based plant cell wall models to study the interaction between Salmonella and the various plant cell wall components. We demonstrated that Salmonella attachment was favoured in the presence of pectin while xyloglucan had no effect on its attachment. Xyloglucan significantly increased the attachment of Salmonella cells to the plant cell wall model only when it was in association with pectin. In this study, we investigate whether the plant cell wall polysaccharides mediate Salmonella attachment to the bacterial cellulose-based plant cell wall models through specific carbohydrate interactions or through the effects of carbohydrates on the physical characteristics of the attachment surface.
  
  
  
  We found that none of the monosaccharides that make up the plant cell wall polysaccharides specifically inhibit Salmonella attachment to the bacterial cellulose-based plant cell wall models. Confocal laser scanning microscopy showed that Salmonella cells can penetrate and attach within the tightly arranged bacterial cellulose network. Analysis of images obtained from atomic force microscopy revealed that the bacterial cellulose-pectin-xyloglucan composite with 0.3 % (w/v) xyloglucan, previously shown to have the highest number of Salmonella cells attached to it, had significantly thicker cellulose fibrils compared to other composites. Scanning electron microscopy images also showed that the bacterial cellulose and bacterial cellulose-xyloglucan composites were more porous when compared to the other composites containing pectin.
  
  
  
  Our study found that the attachment of Salmonella cells to cut plant cell walls was not mediated by specific carbohydrate interactions. This suggests that the attachment of Salmonella strains to the plant cell wall models were more dependent on the structural characteristics of the attachment surface. Pectin reduces the porosity and space between cellulose fibrils, which then forms a matrix that is able to retain Salmonella cells within the bacterial cellulose network. When present with pectin, xyloglucan provides a greater surface for Salmonella cells to attach through the thickening of cellulose fibrils.
authors.affiliation: School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor Darul Ehsan, Malaysia.
authors.forename: Michelle Sze-Fan
authors.initials: MS
authors.lastname: Tan
authors.affiliation: CSIRO Agriculture and Food, 671 Sneydes Road, Werribee, VIC, 3030, Australia.
authors.forename: Sean C
authors.initials: SC
authors.lastname: Moore
authors.affiliation: School of Chemistry, Monash University, Clayton campus, Wellington Road, Clayton, VIC, 3800, Australia.
authors.forename: Rico F
authors.initials: RF
authors.lastname: Tabor
authors.affiliation: CSIRO Agriculture and Food, 671 Sneydes Road, Werribee, VIC, 3030, Australia.
authors.forename: Narelle
authors.initials: N
authors.lastname: Fegan
authors.affiliation: School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor Darul Ehsan, Malaysia.
authors.forename: Sadequr
authors.initials: S
authors.lastname: Rahman
authors.affiliation: School of Public Health, Curtin University, Perth, WA, 6845, Australia. gary.dykes@curtin.edu.au.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Dykes
mesh_terms: D001422:Bacterial Adhesion; D002241:Carbohydrates / Q000737:chemistry; D002450:Cell Communication; D002473:Cell Wall / Q000737:chemistry / Q000382:microbiology*; D002482:Cellulose / Q000096:biosynthesis / Q000737:chemistry; D005517:Foodborne Diseases; D005936:Glucans / Q000096:biosynthesis / Q000737:chemistry; D041822:Gluconacetobacter xylinus / Q000502:physiology; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D010368:Pectins / Q000096:biosynthesis / Q000737:chemistry; D059828:Plant Cells / Q000737:chemistry / Q000382:microbiology*; D011134:Polysaccharides; D012475:Salmonella / Q000502:physiology*; D019779:Salmonella enterica / Q000502:physiology; D014990:Xylans / Q000096:biosynthesis / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D005936:Glucans; D011134:Polysaccharides; D014990:Xylans; C029353:xyloglucan; D010368:Pectins; D002482:Cellulose
keywords: Atomic force microscopy; Attachment; Carbohydrate; Confocal laser scanning microscopy; Pectin; Plant cell wall model; Salmonella enterica; Scanning electron microscopy; Xyloglucan