1
|
The Helicobacter pylori UvrC Nuclease Is Essential for Chromosomal Microimports after Natural Transformation. mBio 2022; 13:e0181122. [PMID: 35876509 PMCID: PMC9426483 DOI: 10.1128/mbio.01811-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Helicobacter pylori is a Gram-negative bacterial carcinogenic pathogen that infects the stomachs of half of the human population. It is a natural mutator due to a deficient DNA mismatch repair pathway and is naturally competent for transformation. As a result, it is one of the most genetically diverse human bacterial pathogens. The length of chromosomal imports in H. pylori follows an unusual bimodal distribution consisting of macroimports with a mean length of 1,645 bp and microimports with a mean length of 28 bp. The mechanisms responsible for this import pattern were unknown. Here, we used a high-throughput whole-genome transformation assay to elucidate the role of nucleotide excision repair pathway (NER) components on import length distribution. The data show that the integration of microimports depended on the activity of the UvrC endonuclease, while none of the other components of the NER pathway was required. Using H. pylori site-directed mutants, we showed that the widely conserved UvrC nuclease active sites, while essential for protection from UV light, one of the canonical NER functions, are not required for generation of microimports. A quantitative analysis of recombination patterns based on over 1,000 imports from over 200 sequenced recombinant genomes showed that microimports occur frequently within clusters of multiple imports, strongly suggesting they derive from a single strand invasion event. We propose a hypothetical model of homologous recombination in H. pylori, involving a novel function of UvrC, that reconciles the available experimental data about recombination patterns in H. pylori. IMPORTANCE Helicobacter pylori is one of the most common and genetically diverse human bacterial pathogens. It is responsible for chronic gastritis and represents the main risk factor for gastric cancer. In H. pylori, DNA fragments can be imported by recombination during natural transformation. The length of those fragments determines how many potentially beneficial or deleterious alleles are acquired and thus influences adaptation to the gastric niche. Here, we used a transformation assay to examine imported fragments across the chromosome. We show that UvrC, an endonuclease involved in DNA repair, is responsible for the specific integration of short DNA fragments. This suggests that short and long fragments are imported through distinct recombination pathways. We also show that short fragments are frequently clustered with longer fragments, suggesting that both pathways may be mechanistically linked. These findings provide a novel basis to explain how H. pylori can fine-tune the genetic diversity acquired by transformation.
Collapse
|
3
|
Moulton KD, Adewale AP, Carol HA, Mikami SA, Dube DH. Metabolic Glycan Labeling-Based Screen to Identify Bacterial Glycosylation Genes. ACS Infect Dis 2020; 6:3247-3259. [PMID: 33186014 PMCID: PMC7808405 DOI: 10.1021/acsinfecdis.0c00612] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacterial cell surface glycans are quintessential drug targets due to their critical role in colonization of the host, pathogen survival, and immune evasion. The dense cell envelope glycocalyx contains distinctive monosaccharides that are stitched together into higher order glycans to yield exclusively bacterial structures that are critical for strain fitness and pathogenesis. However, the systematic study and inhibition of bacterial glycosylation enzymes remains challenging. Bacteria produce glycans containing rare sugars refractory to traditional glycan analysis, complicating the study of bacterial glycans and the identification of their biosynthesis machinery. To ease the study of bacterial glycans in the absence of detailed structural information, we used metabolic glycan labeling to detect changes in glycan biosynthesis. Here, we screened wild-type versus mutant strains of the gastric pathogen Helicobacter pylori, ultimately permitting the identification of genes involved in glycoprotein and lipopolysaccharide biosynthesis. Our findings provide the first evidence that H. pylori protein glycosylation proceeds via a lipid carrier-mediated pathway that overlaps with lipopolysaccharide biosynthesis. Protein glycosylation mutants displayed fitness defects consistent with those induced by small molecule glycosylation inhibitors. Broadly, our results suggest a facile approach to screen for bacterial glycosylation genes and gain insight into their biosynthesis and functional importance, even in the absence of glycan structural information.
Collapse
Affiliation(s)
- Karen D. Moulton
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Adedunmola P. Adewale
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Hallie A. Carol
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Sage A. Mikami
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| | - Danielle H. Dube
- Department of Chemistry & Biochemistry, Bowdoin College, 6600 College Station, Brunswick, ME 04011, USA
| |
Collapse
|
4
|
Li H, Marceau M, Yang T, Liao T, Tang X, Hu R, Xie Y, Tang H, Tay A, Shi Y, Shen Y, Yang T, Pi X, Lamichhane B, Luo Y, Debowski AW, Nilsson HO, Haslam SM, Mulloy B, Dell A, Stubbs KA, Marshall BJ, Benghezal M. East-Asian Helicobacter pylori strains synthesize heptan-deficient lipopolysaccharide. PLoS Genet 2019; 15:e1008497. [PMID: 31747390 PMCID: PMC6892558 DOI: 10.1371/journal.pgen.1008497] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 12/04/2019] [Accepted: 10/28/2019] [Indexed: 02/05/2023] Open
Abstract
The lipopolysaccharide O-antigen structure expressed by the European Helicobacter pylori model strain G27 encompasses a trisaccharide, an intervening glucan-heptan and distal Lewis antigens that promote immune escape. However, several gaps still remain in the corresponding biosynthetic pathway. Here, systematic mutagenesis of glycosyltransferase genes in G27 combined with lipopolysaccharide structural analysis, uncovered HP0102 as the trisaccharide fucosyltransferase, HP1283 as the heptan transferase, and HP1578 as the GlcNAc transferase that initiates the synthesis of Lewis antigens onto the heptan motif. Comparative genomic analysis of G27 lipopolysaccharide biosynthetic genes in strains of different ethnic origin revealed that East-Asian strains lack the HP1283/HP1578 genes but contain an additional copy of HP1105 and JHP0562. Further correlation of different lipopolysaccharide structures with corresponding gene contents led us to propose that the second copy of HP1105 and the JHP0562 may function as the GlcNAc and Gal transferase, respectively, to initiate synthesis of the Lewis antigen onto the Glc-Trio-Core in East-Asian strains lacking the HP1283/HP1578 genes. In view of the high gastric cancer rate in East Asia, the absence of the HP1283/HP1578 genes in East-Asian H. pylori strains warrants future studies addressing the role of the lipopolysaccharide heptan in pathogenesis.
Collapse
Affiliation(s)
- Hong Li
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Michael Marceau
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 8204—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Tiandi Yang
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Tingting Liao
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Xiaoqiong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Renwei Hu
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China
| | - Yan Xie
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, China
| | - Hong Tang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Alfred Tay
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Ying Shi
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Yalin Shen
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Tiankuo Yang
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
| | - Xuenan Pi
- Precision Medicine Key Laboratory of Sichuan Province & Precision Medicine Center, West China Hospital, Sichuan University, Chengdu, China
| | - Binit Lamichhane
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Yong Luo
- Key Laboratory of Geoscience Spatial Information Technology, Ministry of Land and Resources of the P.R.China, Chengdu University of Technology
| | - Aleksandra W. Debowski
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
- School of Molecular Sciences, University of Western Australia, Crawley, Australia
| | - Hans-Olof Nilsson
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| | - Stuart M. Haslam
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Barbara Mulloy
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Anne Dell
- Department of Life Sciences, Imperial College London, South Kensington Campus, London, United Kingdom
| | - Keith A. Stubbs
- School of Molecular Sciences, University of Western Australia, Crawley, Australia
| | - Barry J. Marshall
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
- Ondek Pty Ltd, Rushcutters Bay, New South Wales, Australia
| | - Mohammed Benghezal
- West China Marshall Research Center for Infectious Diseases, Center of Infectious Diseases, Division of Infectious Diseases, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China
- Helicobacter pylori Research Laboratory, School of Biomedical Sciences, Marshall Centre for Infectious Disease Research and Training, University of Western Australia, Nedlands, Australia
| |
Collapse
|
5
|
Abstract
Helicobacter pylori infection causes chronic active gastritis that after many years of infection can develop into peptic ulceration or gastric adenocarcinoma. The bacterium is highly adapted to surviving in the gastric environment and a key adaptation is the virulence factor urease. Although widely postulated, the requirement of urease expression for persistent infection has not been elucidated experimentally as conventional urease knockout mutants are incapable of colonization. To overcome this constraint, conditional H. pylori urease mutants were constructed by adapting the tetracycline inducible expression system that enabled changing the urease phenotype of the bacteria during established infection. Through tight regulation we demonstrate that urease expression is not only required for establishing initial colonization but also for maintaining chronic infection. Furthermore, successful isolation of tet-escape mutants from a late infection time point revealed the strong selective pressure on this gastric pathogen to continuously express urease in order to maintain chronic infection. In addition to mutations in the conditional gene expression system, escape mutants were found to harbor changes in other genes including the alternative RNA polymerase sigma factor, fliA, highlighting the genetic plasticity of H. pylori to adapt to a changing niche. The tet-system described here opens up opportunities to studying genes involved in the chronic stage of H. pylori infection to gain insight into bacterial mechanisms promoting immune escape and life-long infection. Furthermore, this genetic tool also allows for a new avenue of inquiry into understanding the importance of various virulence determinants in a changing biological environment when the bacterium is put under duress. Helicobacter pylori is a bacterial pathogen that chronically infects half the global population and is a major contributor to the development of peptic ulcers and stomach cancer. H. pylori has evolved to survive in the stomach and one important adaptation is the enzyme urease. The bacteria cannot establish an infection in the host without this enzyme, and although widely postulated, the requirement of urease for chronic infection of the host has not been tested experimentally as conventional urease mutants are incapable of colonization. To overcome this constraint, a genetic system was introduced that allowed for the making of H. pylori strains in which urease expression could be turned off after the bacteria have colonised the stomach. We show for the first time that this enzyme is not only important for initial colonization but that it is also very important for maintaining chronic infection. We also show that if urease is turned off, the bacterium can mutate several different genes in order to restore urease expression. The genetic approach described here opens up opportunities to studying genes involved in the chronic stage of H. pylori infection to gain insight into how the bacterium is able to avoid clearance by the immune system and how it is able to adapt to changing biological environments.
Collapse
|