Draft Genome of Proteus mirabilis Serogroup O18 Elaborating Phosphocholine-Decorated O Antigen

Abstract

Proteus mirabilis is a pathogenic, Gram-negative, rod-shaped bacterium that causes ascending urinary tract infections. Swarming motility, urease production, biofilm formation, and the properties of its lipopolysaccharide (LPS) are all factors that contribute to the virulence of this bacterium. Uniquely, members of the O18 serogroup elaborate LPS molecules capped with O antigen polymers built of pentasaccharide repeats; these repeats are modified with a phosphocholine (ChoP) moiety attached to the proximal sugar of each O unit. Decoration of the LPS with ChoP is an important surface modification of many pathogenic and commensal bacteria. The presence of ChoP on the bacterial envelope is correlated with pathogenicity, as decoration with ChoP plays a role in bacterial adhesion to mucosal surfaces, resistance to antimicrobial peptides and sensitivity to complement-mediated killing in several species. The genome of P. mirabilis O18 is 3.98 Mb in size, containing 3,762 protein-coding sequences and an overall GC content of 38.7%. Annotation performed using the RAST Annotation Server revealed genes associated with choline phosphorylation, uptake and transfer. Moreover, amino acid sequence alignment of the translated licC gene revealed it to be homologous to LicC from Streptococcus pneumoniae encoding CTP:phosphocholine cytidylyltransferase. Recognized homologs are located in the O antigen gene clusters of Proteus species, near the wzx gene encoding the O antigen flippase, which translocates lipid-linked O units across the inner membrane. This study reveals the genes potentially engaged in LPS decoration with ChoP in P. mirabilis O18.

Keywords: Proteus mirabilis; genome; lipopolysaccharide; phosphocholine; urinary tract infection.

Figure 1

KEGG pathway analysis of Proteus mirabilis PrK 34/57 strain. Proteins were identified and categorized using the GhostKOALA tool against the Amino-Acid file generated by RAST server.

Figure 2

Whole genome phylogeny of Proteus mirabilis strains based on single nucleotide polymorphisms (SNPs) using CSI Phylogeny webserver. The sequence of studied P. mirabilis PrK 34/57 strain is indicated by bold font. The obtained Newick file was visualized using Interactive Tree Of Life (iTOL) version 5.

Figure 3

Whole genome comparison of Proteus mirabilis genomes using progressiveMauve option of Mauve software. Genomes are represented in blue, and blocks with borders of different colors are homologous between genomes The backbone file was visualized using the R package genoPlotR.

Figure 4

Proteus mirabilis O18 O antigen gene cluster arrangement. Highlighted genes represent licABCD genes and its organisation in the Wzx/Wzy-dependent O antigen biosynthesis gene cluster. Scheme modified from Yu et al. (2017).