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.

Phosphocholine decoration of Proteus mirabilis O18 LPS induces hydrophobicity of the cell surface and electrokinetic potential, but does not alter the adhesion to solid surfaces

“…Detection of the signal from the surface of biofilms indicated that phosphocholine could be secreted into the extracellular polymeric matrix that forms the bulk of biofilms, based on previous findings indicating that P. mirabilis ATCC 49565 does not have a chemically distinct capsule, but rather possesses long O-antigen chains ( Dumanski et al, 1994 ). Our previous research ( Czerwonka et al, 2021 ) showed that the decoration mechanism in P. mirabilis O18 is similar to reported earlier in other species, and consists of four genes encoding permease, kinase, cytidylyltransferase and phosphocholine transferase ( Young et al, 2013 ). Presentation of phosphocholine on the bacterial surface is considered an example of molecular mimicry, where bacteria utilise a host-specific molecule to evade the host immune response due to host inability to recognize self-derived molecular structures ( Hergott et al, 2015 ).…”

“…We have focussed on cell surface modification by decoration with ChoP, with a previously described and recently shown mechanism in Proteus mirabilis serogroup O18 (a PrK 34/57 strain) ( Czerwonka et al, 2021 ), and its impact on cell surface properties and its adherence to abiotic surfaces. Bacterial cell adhesion to solid surfaces generally depends on fimbriae/pili.…”

Genomes comparison of two Proteus mirabilis clones showing varied swarming ability

“…The genomic sequences of P. mirabilis K38 and K39 were determined as previously described [ 12 ]. Libraries were prepared with the Nextera XT DNA Library Preparation Kit (Illumina Inc., San Diego, CA, USA), according to the manufacturer’s protocol.…”

“…Over 91.00% of bases in the sequencing reads had quality scores of 30 (Q30) or higher. The genomes were assembled de novo with Unicycler (Galaxy Version 0.4.8.0, https://usegalaxy.org/ [ 14 ], a SPAdes optimizer, as previously described [ 12 ]. The default options of SPAdes were selected, including error correction turned on and k-mer in a range of 0.2–0.95 (expressed as a fraction of the read length).…”

“…The PathogenFinder v1.1 pathogenicity prediction program (available at https://cge.cbs.dtu.dk/services/PathogenFinder/ ) was used to examine the likelihood that P. mirabilis K38 and K39 were human pathogens [ 25 ]. The presence of genes related to the most important virulence factors was also tested, as previously described [ 12 ], using an in-house local database of virulence genes created with the makeblastdb option of BLAST + [ 26 ]. The genes were selected based on the previously described genome of P. mirabilis HI4320 [ 27 ].…”