EPS text description
Bacterial surface polysaccharides are considered to be key macromolecules in determining microbe-host interactions, as they display a high degree of variety and diversity among bacterial species in terms of composition, monomer linkages, branching degree, polymer size, production level, etc. Since most bacteria contain more than one type of surface polysaccharides, such as lipopolysaccharides (O-antigens), capsular polysaccharides (CPS), exopolysaccharides (EPS), and/or glycan chains as part of glycoproteins, the elucidation of their exact role is complex. Nevertheless, surface polysaccharides are now known to exert important functions including adherence, biofilm formation, and evasion of host defenses such as phagocytosis (40). All the OGs involved in EPS and CPS biosynthesis are listed in Table 9.
The L. plantarum WCFS1 genome encodes 4 clusters of genes that are associated with surface polysaccharide production (cps-1, cps-2, cps-3, cps-4), and all have reported to be functional (41). The distribution of the cps-1/cps-4 gene cluster across the 54 L. plantarum strains is reported in Table 9. The cps-4 gene cassette was found to be present in the majority of the strains, with the exception of some strains of various origins (NAB2, NIZO2259, NIZO2263, NIZO2457, NIZO2494, NIZO2726, NIZO2776, NIZO2802, NIZO2830, NIZO2831, NIZO2891, P8, JDM1) apparently bearing truncated genes. In contrast, the cps-1-cps-3 gene cluster varies considerably in size, composition, sequence and gene order between strains and it is absent in 4 strains of different origins (NIZO2753, NIZO3893, P8 and 16). In particular, the cps-1 gene cassette appears to be unique to the reference strain WCFS1. The 43 newly sequenced strains contain 64 ORFs in the cps-1-cps-3 region that were not found in any published L. plantarum strain. Most of these ORFs are EPS related or of unknown function, but also ORFs with known functions (e.g. DNA topoisomerase, manganese transporter, etc.) have been found.
Three new gene cassettes (cps-5, cps-6, cps-7) have been found in the pan-genome that are absent in WCFS1. They comprise what appears to be a nearly complete EPS biosynthesis cluster. Cassette cps-5 consists of 9 ORFs and is found in NIZO2877 and NIZO2855 strains, both isolated from meat products in Vietnam, but also in strain ATCC14917, isolated from cabbage in Denmark. NIZO1839, NIZO2889, NIZO2891, NIZO2535, NIZO2484 and NIZO2485, which have different origins, have nearly the same gene cassettes, except for a priming glycosyltransferase and a UDP-galactofuranoyltransferase that are absent in the first two strains. Cassette cps-6 consists of 8 ORFs and is found in NIZO2757, IPLA88, NIZO2766, NIZO2259, NIZO2262 and NIZO3894 of both human and plant origin. The cps-7 gene cassette contains 10 ORFs and is found in a total of 11 strains of various origins (NAB2, NIZO3892, ST-III, ZJ316, NAB1, WJL_IGFL, NIZO2260, NIZO1837, NIZO2457 and NIZO2494). A striking feature of this cassette is the presence of a putative beta-lactamase gene, which is associated with antibiotic resistance instead of EPS biosynthesis. This gene has only been found in L. plantarum species.
40. Lebeer S, Verhoeven TLA, Francius G, Schoofs G, Lambrichts I, Dufrêne Y, et al. Identification of a Gene Cluster for the Biosynthesis of a Long, Galactose-Rich Exopolysaccharide in Lactobacillus rhamnosus GG and Functional Analysis of the Priming Glycosyltransferase. Appl Environ Microbiol. 2009 May 31;75(11):3554–63.
41. Remus DM, van Kranenburg R, van Swam II, Taverne N, Bongers RS, Wels M, et al. Impact of 4 Lactobacillus plantarum capsularpolysaccharide clusters on surface glycancomposition and host cell signaling. Microbial Cell Factories. Microbial Cell Factories; 2012 Nov 21;11(1):1–1.