Lysine 2-hydroxyisobutyrylation (K hib) is a novel posttranslational modification (PTM), which was thought to play a role in active gene transcription and cellular proliferation. Here we report a comprehensive identification of K hib in Proteus mirabilis (P. mirabilis). By combining affinity enrichment with two-dimensional liquid chromatography and high-resolution mass spectrometry, 4735 2-hydroxyisobutyrylation sites were identified on 1051 proteins in P. mirabilis. These proteins bearing modifications were further characterized in abundance, distribution and functions. The interaction networks and domain architectures of these proteins with high confidence were revealed using bioinformatic tools. Our data demonstrate that many 2-hydroxyisobutyrylated proteins are involved in metabolic pathways, such as purine metabolism, pentose phosphate pathway and glycolysis/gluconeogenesis. The extensive distribution of K hib also indicates that the modification may play important influence to bacterial metabolism. The speculation is further supported by the observation that carbon sources can influence the occurrence of K hib. Furthermore, we demonstrate that 2-hy-droxyisobutyrylation on K343 was a negative regulatory modification on Enolase (ENO) activity, and molecular docking results indicate the regulatory mechanism that K hib may change the binding formation of ENO and its substrate 2-phospho-D-glycerate (2PG) and cause the substrate far from the active sites of enzyme. We hope this first comprehensive analysis of nonhistone K hib in prokaryotes is valuable for further functional investigation of this modification.

The genus Proteus belongs to the Enterobacteriaceae family, where it is placed in the tribe Proteeae, together with the genera Morganella and Providencia. Currently, the genus Proteus consists of five species: P. mirabilis, P. vulgaris, P. penneri, P. hauseri and P. myxofaciens, as well as three unnamed Proteus genomospecies. The most defining characteristic of Proteus bacteria is a swarming phenomenon, a multicellular differentiation process of short rods to elongated swarmer cells. It allows population of bacteria to migrate on solid surface. Proteus bacteria inhabit the environment and are also present in the intestines of humans and animals. These microorganisms under favorable conditions cause a number of infections including urinary tract infections (UTIs), wound infections, meningitis in neonates or infants and rheumatoid arthritis. Therefore, Proteus is known as a bacterial opportunistic pathogen. It causes complicated UTIs with a higher frequency, compared to other uropathogens. Proteus infections are accompanied by a formation of urinary stones, containing struvite and carbonate apatite. The virulence of Proteus rods has been related to several factors including fimbriae, flagella, enzymes (urease - hydrolyzing urea to CO2 and NH3, proteases degrading antibodies, tissue matrix proteins and proteins of the complement system), iron acqusition systems and toxins: hemolysins, Proteus toxin agglutinin (Pta), as well as an endotoxin - lipopolysaccharide (LPS). Proteus rods form biofilm, particularly on the surface of urinary catheters, which can lead to serious consequences for patients. In this review we present factors involved in the regulation of swarming phenomenon, discuss the role of particular pathogenic features of Proteus spp., and characterize biofilm formation by these bacteria.

No abstract

Introduction: Proteus penneri lipopolysaccharide (LPS) core regions are characterized by a greater structural variability than that observed in other Enterobacteriaceae. This fact and the small amount of published data concerning the serological activity of this part of P. penneri LPS prompted an examination of which fragment might determine cross-reactions with antibodies. To date, such epitopes have been found in the LPS core regions of P. mirabilis and P. vulgaris strains. Materials and Methods: Proteus sp. LPSs were tested with unabsorbed rabbit antisera by enzyme-linked immunosorbent assay (ELISA), sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot, and once again by ELISA or passive immunohemolysis after the absorption of these antisera with selected LPSs. Results: The serological studies of P. penneri 8 LPS demonstrated antibodies in the tested antisera recognizing a common epitope located in the core regions of six of the LPSs, i.e. P. penneri 8, 34, 133, 7, 14, and 15. Additionally, another type of antibody directed against some fragment of P. penneri 13 and the core regions of other LPSs investigated was observed in one antiserum. Conclusions: A distal, trisaccharide fragment of the P. penneri 8 LPS core region is suggested to determine the cross-reactions of the tested antisera with the six P. penneri LPSs.Key words: Proteus penneri, lipopolysaccharide, core region, anti-conjugate serum, epitope.Abbreviations: LPS -lipopolysaccharide, Glc -glucose, GlcN -glucosamine, IgG -immunoglobulin G, IgM -immunoglobulin M, ELISA -enzyme-linked immunosorbent assay, PIH -passive immunohemolysis.Corresponding author: Agata Palusiak, Department of General Microbiology, Institute of Microbiology and Immunology, University of £ódŸ, Banacha 12/16, 90-237 £ódŸ, Poland, tel.: +48 42 635-44-69, fax: +48 42 665-58-18, e-mail: agatapal @biol.uni.lodz.pl O-polysaccharide-specific antibodies in such antisera can influence the cross-reactivity of core-specific antibodies and may not demonstrate the real serological activity of the core region of the lipopolysaccharide (LPS). In this paper we report on serological studies performed with two different kinds of sera against P. penneri 8 containing only core-specific antibodies. The application of this material allowed a more precise determination of which fragment of the P. penneri 8 LPS core region may react with specific antibodies. MATERIALS AND METHODS Bacterial strainsP. penneri 8 (O67) was a clinical isolate from the urine of a patient with bacteriuria in Missouri (USA). This strain and 26 others, i.e. P. penneri 1 (O72a), 2 (O66), 4 (O72a,b), 7 (O61), 11 (O58), 12 (O58) ,

No abstract

The frequency of P. penneri isolation from hospital patients, mostly from urine and wounds, keeps on growing, and numerous isolates are multi-drug resistant. P. penneri rods produce lipopolysaccharide (LPS), which may lead to the septic shock. Until now, O-specific polysaccharide has been the best structurally and serologically characterized region of P. penneri LPS. It is worth having an insight into the serological specificity of both poly- and oligosaccharide parts of P. penneri LPS. The P. penneri core region is less structurally diverse than OPS, but still, among other enterobacterial LPS core regions, it is characterized by structural variability. In the present study, the serological reactivity of 25 P. penneri LPS core regions was analyzed by ELISA, passive immunohemolysis and Western blot technique using five polyclonal P. penneri antisera after or without their adsorption with the respective LPSs. The results allowed the assignment of the tested strains to five new core serotypes, which together with published serological studies led to the creation of the first serotyping scheme based on LPS core reactivities of 35 P. penneri and three P. mirabilis strains. Together with the O types scheme, it will facilitate assigning Proteus LPSs of clinical isolates into appropriate O and R serotypes.

No abstract

Introduction: Both smooth and rough Proteus sp. strains can be found. The latter are characterized by their lack of an O--polysaccharide chain in the lipopolysaccharide (LPS) molecule, which makes them suitable for obtaining anti-core sera. Using this kind of material enables identifying fragments of the Proteus LPS core region that might be involved in cross-reactions. To date only a few similar epitopes have been established for the genus Proteus. Materials and Methods: Polyclonal rabbit antisera directed against three rough strains of Proteus sp. were tested by enzymelinked immunosorbent assay (ELISA) with a set of LPSs. The reactivity of the selected cross-reactive and homologous systems was checked by the Western blot technique and by a passive immunohemolysis assay preceded by the absorption of each antiserum with appropriate cross-reactive and homologous alkalized LPSs. Results: On the basis of the ELISA results, 19 cross-reactive antigens were selected among which both smooth and rough LPS forms were found. All the observed reactions involved the core region of the LPS. Using the antisera absorbed with the appropriate LPSs allowed identification of four groups of antigens with serologically identical core regions. Conclusions:Comparing the results of the serological studies with the known chemical structures of the core regions of the LPSs used enabled the identification of a few core oligosaccharide fragments probably involved in the observed cross-reactions. All were located in the most distal part of LPS core region, which made them more easily recognized by specific antibodies.