The genome and surface proteome of Capnocytophaga canimorsus reveal a key role of glycan foraging systems in host glycoproteins deglycosylation

Abstract

SummaryCapnocytophaga canimorsus are commensal Gramnegative bacteria from dog's mouth that cause rare but dramatic septicaemia in humans. C. canimorsus have the unusual property to feed on cultured mammalian cells, including phagocytes, by harvesting the glycan moiety of cellular glycoproteins. To understand the mechanism behind this unusual property, the genome of strain Cc5 was sequenced and analysed. In addition, Cc5 bacteria were cultivated onto HEK 293 cells and the surface proteome was determined. The genome was found to encode many lipoproteins encoded within 13 polysaccharide utilization loci (PULs) typical of the FlavobacteriaBacteroides group. PULs encode surface exposed feeding complexes resembling the archetypal starch utilization system (Sus). The products of at least nine PULs were detected among the surface proteome and eight of them represented more than half of the total peptides detected from the surface proteome. Systematic deletions of the 13 PULs revealed that half of these Sus-like complexes contributed to growth on animal cells. The complex encoded by PUL5, one of the most abundant ones, was involved in foraging glycans from glycoproteins. It was essential for growth on cells and contributed to survival in mice. It thus represents a fitness factor during infection.

New Iron Acquisition System in Bacteroidetes

“…At least 10 of them are expressed, accounting for more than half of the surface-exposed proteins, when Cc5 bacteria are grown on HEK293 cells. All of these findings indicate that surface-exposed complexes specialized in foraging complex glycans or other macromolecules play a central role in the biology of C. canimorsus (37). Indeed, C. canimorsus has the unusual property of harvesting N-linked glycan chains of soluble proteins like immunoglobulins and even of surface glycoproteins from animal cells, including phagocytes.…”

“…The genome of saprophytic Bacteroidetes like F. johnsoniae also contains a large number of PUL (34), indicating that they are a hallmark of the Bacteroidetes phylum rather than of the commensal Bacteroides only. The genome of the clinical isolate type strain C. canimorsus 5 (also called strain Cc5) (35,36) contains 13 such PUL, which may encode surface feeding machineries (37). At least 10 of them are expressed, accounting for more than half of the surface-exposed proteins, when Cc5 bacteria are grown on HEK293 cells.…”

“…Thirty-eight were involved in a variety of processes, but 16 encoded Sus-like feeding complexes (data not shown). The latter 16 genes belong to only 3 polysaccharide utilization loci, namely PUL3 (9 genes), PUL7 (6 genes), and PUL11 (one gene) (37). Because PUL genes represent 16.5% of those differentiating strains that can or cannot grow in HIHS while all of the PUL genes represent only about 4% of the Cc5 complete genome, we first tested the PUL3, PUL7, and PUL11 knockout mutants for growth in HIHS.…”

Comprehensive Spatial Analysis of the Borrelia burgdorferi Lipoproteome Reveals a Compartmentalization Bias toward the Bacterial Surface

“…Some Gram-negative bacteria express surface-exposed lipoproteins (27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45) but, with the exception of recently discovered surface lipoproteins in the phylum Bacteroidetes (43, 45), they remain relatively rare. In the Gram-negative model organism E. coli, only 7 of the about 90 expressed lipoproteins (46, 47) were detected on the bacterial surface but remained restricted to a proportion of total protein and certain protein domains, indicating rather complex and dynamic OM topologies (39,42,(48)(49)(50)(51)(52).…”

Complete Genome Sequence of the Dog Commensal and Human Pathogen Capnocytophaga canimorsus Strain 5

“…These organisms escape the innate immune defenses of the host (19,22,23) and have the unusual ability to feed on the glycan moieties of glycoproteins present on the surfaces of mammalian cells, including phagocytes (14). This property is based on a sialidase and specialized complexes of the Sus family, mainly composed of surface-exposed lipoproteins (15,16,21). Here, we present the genome sequence of C. canimorsus Cc5, a strain that was isolated from a human septicemia patient (22).…”