Michael E. Konkel

Washington State University

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Julian M. Ketley

University of Leicester

Xiaonan Lu

McGill University

Witold Cieplak

Metis Design Corporation (United States)

Nicholas M. Negretti

Vanderbilt University Medical Center

John D. Klena

Centers for Disease Control and Prevention

L A Joens

University of Arizona

Derrick R. Samuelson

University of Nebraska Medical Center

Tyson P. Eucker

Boehringer Ingelheim (United States)

C. L. Larson

National Institute of Allergy and Infectious Diseases

Steve Garvis

École Normale Supérieure de Lyon

Cooperative Institutions

Washington State University

University of British Columbia

Pacific Northwest National Laboratory

Agricultural Research Service

National Institutes of Health

United States Department of Agriculture

National Institute of Allergy and Infectious Diseases

Battelle

University of Wisconsin–Madison

Oregon Health & Science University

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Secretion of the Virulence‐AssociatedCampylobacterInvasion Antigens fromCampylobacter jejuniRequires a Stimulatory Signal

The Journal of Infectious Diseases (2001)

Vanessa Rivera‐Amill Bong Jik Kim J. Seshu Michael E. Konkel

Campylobacter jejuni are a common cause of human diarrheal illness. Previous work has demonstrated that C. jejuni synthesize a novel set of proteins upon coculturing with epithelial cells, some of which are secreted. The secreted proteins have been collectively referred to as Campylobacter invasion antigens (Cia proteins). Metabolic labeling experiments revealed that Cia protein synthesis and secretion are separable and that secretion is the rate-limiting step of these processes. Additional work indicated that Cia protein synthesis is induced in response to bile salts and various eukaryotic host cell components. Host cell components also can induce Cia protein secretion. Culturing C. jejuni on plates supplemented with the bile salt deoxycholate retarded the inhibitory effect of chloramphenicol on C. jejuni invasion, as judged by the gentamicin-protection assay. These data suggest that the coordinate expression of the genes encoding the Cia proteins is subject to environmental regulation

Secretory protein

10.1086/320704

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Citations (158)

Characterization of the Thermal Stress Response of Campylobacter jejuni

Infection and Immunity (1998)

Michael E. Konkel Bong Jik Kim John D. Klena Colin R. Young Richard L. Ziprin

ABSTRACT Campylobacter jejuni , a microaerophilic, gram-negative bacterium, is a common cause of gastrointestinal disease in humans. Heat shock proteins are a group of highly conserved, coregulated proteins that play important roles in enabling organisms to cope with physiological stresses. The primary aim of this study was to characterize the heat shock response of C. jejuni . Twenty-four proteins were preferentially synthesized by C. jejuni immediately following heat shock. Upon immunoscreening of Escherichia coli transformants harboring a Campylobacter genomic DNA library, one recombinant plasmid that encoded a heat shock protein was isolated. The recombinant plasmid, designated pMEK20, contained an open reading frame of 1,119 bp that was capable of encoding a protein of 372 amino acids with a calculated molecular mass of 41,436 Da. The deduced amino acid sequence of the open reading frame shared similarity with that of DnaJ, which belongs to the Hsp-40 family of molecular chaperones, from a number of bacteria. An E. coli dnaJ mutant was successfully complemented with the pMEK20 recombinant plasmid, as judged by the ability of bacteriophage λ to form plaques, indicating that the C. jejuni gene encoding the 41-kDa protein is a functional homolog of the dnaJ gene from E. coli . The ability of each of two C. jejuni dnaJ mutants to form colonies at 46°C was severely retarded, indicating that DnaJ plays an important role in C. jejuni thermotolerance. Experiments revealed that a C. jejuni DnaJ mutant was unable to colonize newly hatched Leghorn chickens, suggesting that heat shock proteins play a role in vivo.

Immunoscreening

10.1128/iai.66.8.3666-3672.1998

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Citations (128)

Identification and characterization of an intervening sequence within the 23S ribosomal RNA genes of Campylobacter jejuni

Molecular Microbiology (1994)

Michael E. Konkel Richard T. Marconi David J. Mead Witold Cieplak

Summary Campylobacter jejuni is a significant cause of bacterial enteritis in humans. Three of seven C. jejuni isolates examined were found to contain fragmented 23S rRNA. The occurrence of fragmented 23S rRNA correlated with the presence of an intervening sequence (IVS) within the 23S rRNA genes. The IVS is 157 nucleotides in length and replaces an eight nucleotide sequence in the 23S rRNA genes of C. jejuni isolates that contain intact 23S rRNA. The two ends of the IVS share 31 bases of complementarity that could form a stem‐loop structure. Fragmentation of the 23S ribosomal RNA results from the excision of the IVS from the transcribed RNA; the 3’ cleavage site maps within the putative stem‐loop formed by the IVS. Southern hybridization analysis revealed that the IVS is not present in the genomes of isolates that contain intact 23S rRNA, suggesting that the IVS is not derived from Campylobacter chromosomal sequences. The C. jejuni IVS is located at a position analogous to that of the IVSs found in both Salmonella and Yersinia spp.

23S ribosomal RNA

10.1111/j.1365-2958.1994.tb01284.x

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Characterization of Genetically Matched Isolates of Campylobacter jejuni Reveals that Mutations in Genes Involved in Flagellar Biosynthesis Alter the Organism's Virulence Potential

Applied and Environmental Microbiology (2007)

Preeti Malik-Kale Brian H. Raphael Craig T. Parker L A Joens John D. Klena

Phenotypic and genotypic evidence suggests that not all Campylobacter jejuni isolates are pathogenic for humans. We hypothesized that differences in gene content or gene expression alter the degree of pathogenicity of C. jejuni isolates. A C. jejuni isolate (Turkey) recovered from a turkey and a second C. jejuni isolate (CS) recovered from a chicken differed in their degrees of in vitro and in vivo virulence. The C. jejuni Turkey isolate invaded INT 407 human epithelial cells and secreted the Cia (Campylobacter invasion antigen) proteins, while the C. jejuni CS isolate was noninvasive for human epithelial cells and did not secrete the Cia proteins. Newborn piglets inoculated with the C. jejuni Turkey isolate developed more severe clinical signs of campylobacteriosis than piglets inoculated with the C. jejuni CS isolate. Additional work revealed that flagellin was not expressed in the C. jejuni CS isolate. Microarray and real-time reverse transcription-PCR analyses revealed that all flagellar class II genes were significantly downregulated in the C. jejuni CS isolate compared to the C. jejuni Turkey isolate. Finally, nucleotide sequencing of the flgR gene revealed the presence of a single residue that was different in the FlgR proteins of the C. jejuni Turkey and CS isolates. Complementation of the C. jejuni CS isolate with a wild-type copy of the flgR gene restored the isolate's motility. Collectively, these findings support the hypothesis that critical differences in gene content or gene expression can alter the pathogenic potential of C. jejuni isolates.

Flagellin

10.1128/aem.01399-06

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Citations (61)

Interactions of Campylobacter jejuni with non-professional phagocytic cells.

Brian H. Raphael M. R. Monteville John D. Klena L A Joens Michael E. Konkel

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Role of flagella in adherence, internalization, and translocation of Campylobacter jejuni in nonpolarized and polarized epithelial cell cultures

Infection and Immunity (1993)

Cameron Grant Michael E. Konkel Witold Cieplak Lucy S. Tompkins

Previous studies of Campylobacter jejuni have suggested that flagellin is an adhesin for epithelial cells and that motility is a virulence factor of this bacterium. The role of flagella in the interactions of C. jejuni with nonpolarized and polarized epithelial cells was examined with flagellar mutants. Flagellated, nonmotile (flaA flaB+ Mot-) and nonflagellated, nonmotile (flaA flaB Mot-) mutants of C. jejuni were constructed by in vivo homologous recombination and gene replacement techniques. Both classes of mutants were found to adhere to cells of human epithelial origin (INT 407) equally well; however, on the basis of the percentage of the inoculum internalized, internalization of the flaA flaB Mot- mutants was decreased by factors ranging from approximately 30 to 40 compared with the parent. The flaA flaB+ Mot- mutant was internalized by the INT 407 cells at levels six- to sevenfold higher than the flaA flaB Mot- mutants. Both classes of mutants, unlike the parent, were unable to translocate across polarized Caco-2 monolayers. These results indicate that flagella are not involved in C. jejuni adherence to epithelial cells but that they do play a role in internalization. Furthermore, the results suggest that either the motility of C. jejuni or the product of flaA is essential for the bacterium to cross polarized epithelial cell monolayers.

Flagellin

Internalization

10.1128/iai.61.5.1764-1771.1993

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Citations (281)

Identification of a Campylobacter jejuni‐secreted protein required for maximal invasion of host cells

Molecular Microbiology (2009)

Jeffrey E. Christensen Sophia A. Pacheco Michael E. Konkel

The food-borne pathogen Campylobacter jejuni is dependent on a functional flagellum for motility and the export of virulence proteins that promote maximal host cell invasion. Both the flagellar and non-flagellar proteins exported via the flagellar type III secretion system contain a sequence within the amino-terminus that directs their export from the bacterial cell. Accordingly, we developed a genetic screen to identify C. jejuni genes that encode a type III secretion amino-terminal sequence that utilizes the flagellar type III secretion system of Yersinia enterocolitica and a phospholipase reporter (yplA). We screened a library of 321 C. jejuni genes and identified proteins with putative type III secretion amino-terminal sequences. One gene identified by the screen was Cj1242. We generated a mutation in Cj1242, and performed growth rate, motility, secretion and INT 407 cell adherence and internalization assays. The C. jejuni Cj1242 mutant was not altered in growth rate or motility when compared with the wild-type strain, but displayed an altered secretion profile and a reduction in host cell internalization. Based on the phenotype of the C. jejuni Cj1242 mutant, we designated the protein Campylobacter invasion antigen C (CiaC). Collectively, our findings indicate that CiaC is a potentially important virulence factor.

Flagellin

Internalization

10.1111/j.1365-2958.2009.06797.x

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Citations (104)

Editorial: Campylobacter-associated food safety

Frontiers in Microbiology (2022)

Jingbin Zhang Michael E. Konkel Greta Gölz Xiaonan Lu

Campylobacter is one of the leading bacterial causes of gastroenteritis worldwide. As the commensal in the gastrointestinal tract of warm-blooded animals, especially food-producing animals, Campylobacter can be transmitted to humans through the food supply chain and cause human campylobacteriosis. Although Campylobacter typically causes self-limiting gastroenteritis, it can also lead to prolonged postinfectious complications, such as Guillain-Barré syndrome, reactive arthritis, and/or post infectious-irritable bowel syndrome, posing a great threat to public health. To address the potential risks associated with this disease, numerous studies have been conducted to improve our understanding of this microbe and its interaction with the agri-food system. This mini-review acts as the editorial summary of the published articles in this special issue collected in Frontiers in Microbiology and provides a brief overview of 1) improved detection methods; 2) prevalence and characterization; 3) novel intervention strategies of Campylobacter in the agri-food settings. This special issue is timely due to the increased recognition of Campylobacter organisms as a serious health threat by the World Health Organization, Centers for Disease Control and Prevention, Health Canada, and European Union.

Campylobacteriosis

10.3389/fmicb.2022.1038128

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Environmental Stress-Induced Bacterial Lysis and Extracellular DNA Release Contribute to Campylobacter jejuni Biofilm Formation

Applied and Environmental Microbiology (2017)

Jinsong Feng Lina Ma Jiatong Nie Michael E. Konkel Xiaonan Lu

Campylobacter jejuni is a microaerophilic bacterium and is believed to persist in a biofilm to antagonize environmental stress. This study investigated the influence of environmental conditions on the formation of C. jejuni biofilm. We report an extracellular DNA (eDNA)-mediated mechanism of biofilm formation in response to aerobic and starvation stress. The eDNA was determined to represent a major form of constitutional material of C. jejuni biofilms and to be closely associated with bacterial lysis. Deletion mutation of the stress response genes spoT and recA enhanced the aerobic influence by stimulating lysis and increasing eDNA release. Flagella were also involved in biofilm formation but mainly contributed to attachment rather than induction of lysis. The addition of genomic DNA from either Campylobacter or Salmonella resulted in a concentration-dependent stimulation effect on biofilm formation, but the effect was not due to forming a precoating DNA layer. Enzymatic degradation of DNA by DNase I disrupted C. jejuni biofilm. In a dual-species biofilm, eDNA allocated Campylobacter and Salmonella at distinct spatial locations that protect Campylobacter from oxygen stress. Our findings demonstrated an essential role and multiple functions of eDNA in biofilm formation of C. jejuni, including facilitating initial attachment, establishing and maintaining biofilm, and allocating bacterial cells.IMPORTANCECampylobacter jejuni is a major cause of foodborne illness worldwide. In the natural environment, the growth of C. jejuni is greatly inhibited by various forms of environmental stress, such as aerobic stress and starvation stress. Biofilm formation can facilitate the distribution of C. jejuni by enabling the survival of this fragile microorganism under unfavorable conditions. However, the mechanism of C. jejuni biofilm formation in response to environmental stress has been investigated only partially. The significance of our research is in identifying extracellular DNA released by bacterial lysis as a major form of constitution material that mediates the formation of C. jejuni biofilm in response to environmental stress, which enhances our understanding of the formation mechanism of C. jejuni biofilm. This knowledge can aid the development of intervention strategies to limit the distribution of C. jejuni.

Environmental stress

10.1128/aem.02068-17

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Whole Transcriptome Sequencing Analysis of the Synergistic Antimicrobial Effect of Metal Oxide Nanoparticles and Ajoene on Campylobacter jejuni

Frontiers in Microbiology (2018)

Xue Rui Jinsong Feng Lina Ma Chunrong Liu Ming Xian

Two metal oxide (i.e., Al2O3 and TiO2) nanoparticles and ajoene, a garlic-derived organosulfur compound, were identified to be effective antimicrobials against Campylobacter jejuni, a leading cause of human gastrointestinal diseases worldwide. A significant synergistic antimicrobial effect was observed using ajoene and Al2O3/TiO2 nanoparticles in a combined manner to cause at least 8 log10 CFU/mL reduction of C. jejuni cells. Whole transcriptome sequencing (RNA-seq) and confocal micro-Raman spectroscopic analyses revealed the antimicrobial mechanism and identified the roles of ajoene and metal oxide nanoparticles in the synergistic treatment. Ajoene and metal oxide nanoparticles mediated a two-phase antimicrobial mechanism. Ajoene served as the inducing factor at the first phase that caused injury of cell membranes and increased the susceptibility of C. jejuni to stress. Metal oxide nanoparticles served as the active factor at the second phase that targeted sensitive cells and physically disrupted cell structure. This synergistic antimicrobial treatment demonstrates a potential to reduce the prevalence of C. jejuni and other pathogens on food contact surfaces and in the food chain.

10.3389/fmicb.2018.02074

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Citations (14)