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At least 19 recordsLinked to original sources
PubMed1978

Cyclic AMP-dependent synthesis of fimbriae in Salmonella typhimurium: effects of cya and pts mutations.

Synthesis of bacterial fimbriae (group 1, subtype 1) was shown to be dependent on cyclic AMP and was subject to catabolite repression by many carbohydrates. Mutations in the genes coding for the energy-coupling protein constituents of the phosphoenolpyruvate:sugar phosphotransferase system prevented repression of fimbrial production by the sugar substrates of this enzyme system.

Carbohydrates↗
PubMed1979

Serologic diagnosis of gonococcal infection.

Infection with N. gonorrhoeae stimulates the production of antibodies to many common, species-specific, and type-specific antigens. The L-antigen is an envelop antigen and antibodies to it could be demonstrated by various methods in more than 90% of the patients after the first 10 days of infection. Serologic tests are not yet available in the United States. If and when they become available, they may be recommended for: (1) Screening asymptomatic men and women, (2) Use as an adjunct diagnostic tool in cases of prostatitis, arthritis, disseminated gonococcal infection, and pelvic inflammatory disease, (3) Use (alone or in conjunction with culture) when specimens must be mailed to a central laboratory, when mailing conditions do not allow for incubation within 24-48 hr, or when proper media and qualified bacteriologists are not available.

Antigens, Bacterial↗
PubMed1979

[Purification of Salmonella abortus ovis H antigen by using immunoadsorption].

OH-antiserum was first produced in rabbit immunization with Salmonella abortus ovis cultures and was later used for obtaining an immunoadsorbent after the method of Avrameas and Thernynck. The raw (not purified) H-antigen produced after the method of McCoy et al., was purified by the immunoadsorbent and its activity and specificity were studied serologically by the reaction of Ouchterlony. It was established that the antigen reacts with the anti-H-salmonella serum, but does not react with normal sheep serum, which is an indication that it is purified and active. It was established also that immunoadsorption is a method suitable for H-antigen production from bacterial cilia.

Antigens, Bacterial↗
PubMed2025

Identification of OxyR as an activator of type 1 fimbriae (fim) in Salmonella enterica serovar Typhi.

Salmonella enterica serovar Typhi (S. Typhi) encodes 14 fimbrial gene clusters, including the mannose-binding type 1 fimbriae known as Fim. Type 1 fimbriae have been implicated in biofilm formation and adhesion to host cells in Salmonella. However, their regulation in S. Typhi remains largely unknown. To identify genes affecting the regulation of fim in S. Typhi, we employed both a targeted and a genome-wide transposon-based screening approach. Overall, we identified 18 potential regulators of fim expression: 10 activators and 8 repressors. Two genes involved in the electron transport chain, yqiC and ndh, which encode the type II NADH dehydrogenase NDH-2, were identified. Both YqiC and NDH-2 contribute to the production of reactive oxygen species, prompting an investigation into the roles of oxidative stress response regulators OxyR and SoxR. We found that only OxyR regulates fim expression, which was specific to S. Typhi. OxyR acts by directly binding to the fimA promoter region. This study paves the way for future development of anti-adhesion strategies through the identification of 14 novel regulators for the most prominent fimbriae of S. Typhi.IMPORTANCEAdhesion mediated by fimbriae is one of the critical steps in the infection process. Therefore, it is essential to better understand the regulation of type 1 fimbriae (fim) in the human-specific pathogen Salmonella enterica serovar Typhi, the etiologic agent of typhoid fever. In this study, we identified 18 distinct mutants with altered regulation of fim. Furthermore, we confirmed that the DNA-binding protein OxyR directly regulates fim expression. Importantly, we also demonstrated regulatory differences in fim expression between S. Typhi and S. Typhimurium, as six of the genes identified altering fim expression in S. Typhi either did not affect fim expression in S. Typhimurium or had the contrary effect. This highlights fundamental differences between these serovars and emphasizes the need to investigate and compare aspects of gene regulation in S. Typhi.

Salmonella typhi↗
PubMed2026

A two-factor authentication mechanism licenses pilins for pilus assembly in gram-positive bacteria.

Gram-positive bacteria display virulence-associated pili that facilitate adhesion and biofilm formation. These pili are covalently polymerized by class C sortase enzymes, which selectively recognize their cognate pilin substrates amid numerous cell wall sorting signal (CWSS)-bearing proteins. The molecular basis for this stringent substrate specificity has remained unclear. Here, we develop a rapid, quantitative fluorescence-activated cell sorting assay to monitor pilus assembly in Corynebacterium diphtheriae, enabling high-throughput analysis of SpaA pilin and SrtA sortase variants. Using this platform, together with molecular modeling and dynamics simulations, we show that SrtA engages nearly the entire SpaA CWSS to form a membrane-embedded complex that incorporates not only the LPXTG motif but also its connector and transmembrane helix elements. Formation of this interface displaces an inhibitory active-site lid and activates the enzyme to load the pilin substrate. Systematic CWSS swapping experiments and deep mutational scanning further support this model, demonstrating that noncognate pilins are excluded because they fail to form the required interface. Conversely, SrtA variants with an artificially unlatched lid bypass the need for this interface, indicating that membrane-driven complex formation is important for substrate licensing. Together, these findings define a "two-factor authentication" mechanism for pilus assembly in gram-positive bacteria: class C sortases first verify pilin identity by forming a membrane-embedded interface that activates the enzyme, then they recognize the LPXTG motif to initiate loading and crosslinking. This work provides a unified molecular framework for selective pilin incorporation in gram-positive bacteria and identifies potential vulnerabilities in the licensing machinery that may be exploited therapeutically.

Fimbriae, Bacterial↗
PubMed1979

Effect of colony type and pH on surface charge and hydrophobicity of Neisseria gonorrhoeae.

The effect of colonial variation and growth at pH 7.2 or pH 6.0 on the surface properties of Neisseria gonorrhoeae was assessed by the use of two-phase partitioning and hydrophobic interaction chromatography. Cells grown at pH 7.2 tended to be both hydrophobic and to possess a slight negative charge. Growth at pH 6.0 appeared to decrease hydrophobicity and to increase the negative surface charge. Possession of a series of outer membrane proteins, termed the colony opacity-associated proteins, did not appear to significantly affect charge or hydrophobicity. Piliated cells tended to have a higher negative charge than nonpiliated variants. They also tended to be less hydrophobic at pH 7.2, but became more hydrophobic at pH 6.0. The implications of these findings are discussed.

Bacterial Proteins↗
PubMed2026

Illicium verum polysaccharide targets fimbriae and flagella to disrupt biofilm and inhibit multidrug-resistant Escherichia coli proliferation.

The widespread dissemination of multidrug-resistant (MDR) E. coli has led to a decrease in the efficacy of antibiotics, posing severe challenges to clinical anti-infective therapy. Owing to their safety, multitarget activities, and low risk of inducing drug resistance, plant polysaccharides represent a promising alternative strategy. In this study, an acidic polysaccharide (IVP-3) was isolated and purified from the medicinal and edible plant Illicium verum, and it was found to inhibit MDR E. coli colonization by disrupting its biofilm. The Mw of IVP-3 was determined to be 35.566 kDa. Its backbone consists of →4)-α-D-GalpA-6-OMe-(1→, →4)-α-D-GalpA-(1→, →4)-β-D-Galp-(1→, and →3,4)-α-D-GalpA-(1 → residues, whereas the branched chain is composed of α-L-Araf-(1 → 5)-α-L-Araf-(1 → attached to the O-5 position of →2,5)-α-L-Araf-(1→, which is further linked to the O-3 position of the backbone. Mechanistically, IVP-3 disrupts the structure of fimbriae and flagella, inhibits bacterial motility, effectively prevents initial biofilm adhesion, and eradicates preformed mature biofilms. Additionally, IVP-3 damages cell membrane integrity, disrupts the proton motive force, and induces energy metabolism disorder, efflux pump inhibition, and oxidative stress, ultimately leading to bacterial lysis. This study provides a theoretical basis for the development of natural antibacterial agents targeting MDR E. coli biofilms and for the high-value utilization of Illicium verum.

Biofilms↗
PubMed1979

Biochemical studies on pili isolated from Pseudomonas aeruginosa strain PAO.

Pseudomonas aeruginosa strains PAO and PAK bear polar pili which are flexible filaments having a diameter of 6 nm and an average length of 2500 nm. Both types of pili are retractile and promote infection by a number of bacteriophages. The present communication describes the partial biochemical characterization of PAO pili isolated from a multipiliated nonretractile mutant of PAO. The observed properties are compared to those of PAK pili which were characterized previously. PAO pili were found to contain a single polypeptide subunit of 18 700 daltons. This is similar to PAK pili which contain a single polypeptide of 18 100 daltons. The amino acid composition of PAO pilin was also similar to that of PAK pilin. Neither protein contained phosphate or carbohydrate residues and both were found to contain N-methylphenylalanine at the amino terminus. Sequencing of 20 amino acid residues at the amino terminal end of PAO pilin revealed the sequence to be identical with that of PAK pilin, while tryptic peptide analyses of PAO and PAK pilin indicated that the two proteins probably contain a number of homologous regions within the polypeptide. It was concluded that PAO and PAK pili were closely related structures.

Amino Acid Sequence↗
PubMed1979

Effect of iron on surface charge and hydrophobicity of Neisseria gonorrhoeae.

The effect of iron concentration during growth on the physicochemical surface properties of the colonial variants of Neisseria gonorrhoeae has been assessed by aqueous two-phase partitioning in a dextran-polyethyleneglycol system containing positively charged trimethylamino-polyethyleneglycol or hydrophobic polyethyleneglycol-palmitate. The complex effects of iron, in combination with other variables known to affect surface charge and hydrophobicity, have provided some clues as to the properties of the gonococcal surface that are important in promoting virulence.

Bacterial Proteins↗
PubMed1975

Fungal fimbriae. I. Structure, origin, and synthesis.

Fine hair-like appendages on the cell walls of the another smut Ustilago violacea are described. These hairs are termed fimbriae because of their close similarity to the fimbriae (pili) found on certain Gram-negative bacteria. Cells of U. violacea may carry more than 200 fimbriae varying in length from about 0.5 mum to over 10 mum, and having a diameter of about 60-70 A. Some fimbriae produce knobs similar to those found on bacterial sex fimbriae. Log-phase cells are the most densely fimbriated, while stationary phase cells are devoid of fimbriae. The cells can be defimbriated by sonication, high-speed agitation, or centrifugation through a 40% sucrose solution. The fimbriae can regenerate in these defimbriated cells in about 1 h. This regeneration is inhibited by both cycloheximide and rifampin, but not by chloramphenicol and therefore appears to depend on de novo protein synthesis on cytoplasmic ribosomes. Similar long fimbriae are found on U. maydis and Leucosporidium (Candida) scottii. Short fimbriae, about 0.5 mum long, were found on all the other species of yeast-like fungi examined (Rhodotorula, Saccharomyces, Schizosaccharomyces, Hansenula, Lipomyces, Nadsonia, and Torulopsis spp.).

Cell Wall↗
PubMed2026

Intra-strain genomic microevolution and phage resistance in Pseudomonas aeruginosa PAO1 laboratory isolates.

Pseudomonas aeruginosa is a major opportunistic pathogen, and its laboratory reference strain, PAO1, is widely used in microbiological and genetic studies. However, PAO1 often exhibits phenotypic variability that can affect experimental reproducibility. Our PAO1 stock, obtained from a public biobank, is resistant to PP7, a pilus-dependent single-stranded RNA phage known to infect PAO1. This suggests the presence of genetic variants in the stock. To check this possibility, we isolated six phenotypically distinct variants (GU1-GU6) and performed genomic and phenotypic analyses. Notable differences were observed among the isolates in terms of motility, pyocyanin production, and susceptibility to PP7. Whole-genome sequencing revealed that four of the six variants harbored mutations in pilus-associated genes. Among these, GU3 carried a mutation in pilT, which encodes a motor protein essential for type IV pilus retraction, and the loss of retraction led to the PP7 resistance. GU2, GU4, and GU6 shared a nonsense mutation in pilJ, a gene involved in chemotaxis and pilus extension, resulting in reduced twitching motility and lower PP7 infection efficiency. Additionally, we found that a mutation in lasR, a master regulator of quorum sensing, promoted the replication of prophage Pf6, which was integrated into the PAO1 genome. Pf6 replication interferes with PP7 infection, providing an alternative mechanism of resistance. These findings offer new insights into the complexity of phage-host interactions and emphasize the importance of routine verification and careful handling of P. aeruginosa sublines used in bacteriological and phage research.IMPORTANCEPhenotypic and genotypic variability in Pseudomonas aeruginosa PAO1 has been widely reported, raising concerns regarding the reproducibility of laboratory studies that rely on this reference strain. In this study, we isolated six PAO1 variants from a single laboratory stock and demonstrated that they differed markedly in motility, pyocyanin production, and susceptibility to the ssRNA phage PP7. Whole-genome sequencing has revealed that even a single mutation in a pilus-associated gene can profoundly affect bacterial motility and phage susceptibility. Furthermore, we showed that a mutation in lasR, a key regulator of the quorum-sensing system, triggered replication of the Pf6 prophage, which in turn hindered PP7 infection. These findings underscore the dynamic nature of laboratory strains and highlight the need for caution when interpreting results from phage-host interaction studies using reference strains. Our results provide a new understanding of how subtle genetic changes in model strains influence experimental outcomes in microbiology.

Pseudomonas aeruginosa↗
PubMed2025

Genomic insights into a diarrheal outbreak in Bangladesh reveal novel ETEC lineages and expansion of CS23 colonization factor.

Enterotoxigenic Escherichia coli (ETEC), a leading cause of diarrhea, is defined by heat-stable (ST) and/or heat-labile (LT) toxins and associated colonization factors (CFs). However, there is still a knowledge gap in understanding ETEC's evolution, particularly in endemic regions like Bangladesh. This study investigates the genomic attributes contributing to the rise of ETEC-associated diarrhea in Bangladesh during 2022-2023. Whole genome sequencing of 325 ETEC isolates (2022-2023), compared with historical strains (1980-2021), revealed significant evolutionary changes. Our findings showed a significant shift in ETEC toxin from LT to ST over the period 2013-2023. The most frequent virulence profile during this period was CFA/I + CS21 compared with previous years (1980-2021). The emergence of CS23-positive ETEC was reported for the first time in Bangladesh, which was considered a less common CF in previous studies. Notably, we report the four novel lineages "L26-L29" in this study through phylogenetic analysis, partly encompassing emergent CS23-positive ETEC strains. Additionally, the high prevalence of multi-drug-resistant ETEC strains and the presence of ESBL-CTX-M-resistant gene during 2022-2023 are a matter of great concern, underscoring the need for preventive measures. The switch of distinct toxin and CF combinations, the rapid emergence of CS23, ESBL-CTX-M resistance, and novel lineages may be the reason behind the increased number of ETEC diarrheal cases between 2022 and 2023. These findings highlight the rapid ETEC evolution that underscores the necessity of continued genomic surveillance to track ongoing changes.IMPORTANCEThis study expands on previous evidence, demonstrating a remarkable genomic diversity in ETEC strains from 2022 to 2023, particularly in virulence factors and AMR genes. The combined findings from these studies will be important for mitigating future diarrheal outbreaks by informing preventive measures, including future vaccine targets, and implementing antibiotic stewardship programs against ETEC infection. Importantly, this research underscores the necessity of continued genomic surveillance to track ongoing changes in ETEC. Such monitoring is essential for understanding the pathogen's evolving population structure, transmission dynamics, and resistance mechanisms.

Bangladesh↗
PubMed2025

Type IV Pili-Associated Secretion of a Biofilm Matrix Protein From Clostridium perfringens That Forms Intermolecular Isopeptide Bonds.

Clostridium perfringens is a gram-positive, anaerobic, spore-forming bacterial pathogen of humans and animals. C. perfringens also produces type IV pili (T4P) and has two complete sets of T4P-associated genes, one of which has been shown to produce surface pili needed for cell adherence. One hypothesis about the second set of T4P genes is that they comprise a type II secretion system (TTSS) like those found in gram-negative bacteria, but for gram-positive bacteria, the TTSS would aid transit across the thick peptidoglycan (PG) layer. The secretome of mutants lacking type IV pilins was examined, and a single protein, BsaC (CPE0517), was identified as being dependent on pilin PilA3 for secretion. The bsaC gene is in an operon with genes encoding a SipW signal peptidase and two putative biofilm matrix proteins, BsaA and BsaB, both of which have remote homology to Bacillus subtilis biofilm protein TasA. Since BsaA forms long oligomers that are secreted, we analyzed BsaA monomer interactions with de novo modeling. These models projected that the monomers formed isopeptide bonds as part of a donor strand exchange process. Mutations in residues predicted to form the isopeptide bonds led to the loss of oligomerization, supporting an exchange and lock mechanism, and isopeptide bonds were detected by mass spectrometry methods. Phylogenetic analysis showed the BsaA family of proteins is widespread among bacteria and archaea, but only a subset is predicted to form isopeptide bonds.

Fimbriae, Bacterial↗
PubMed1979

Attachment pili from enterotoxigenic Escherichia coli pathogenic for humans.

Pili from enterotoxigenic Escherichia coli pathogenic for humans have been isolated by adsorption to the surface of erythrocytes followed by thermal elution. The pili are composed of two protein subunits with molecular weights of 13,100 and 12,500 as determined by sodium dodecyl sulfate-gel electrophoresis. These pili also bind to human buccal cells under temperature conditions (37 degrees C) which prevent the binding of these pili to the erythrocytes. Analogous temperature effects on binding have previously been observed with whole bacterial cells. This binding can be inhibited by antiserum prepared against the isolated pili.

Bacterial Proteins↗