Genetic Diversity as Consequence of a Microaerobic and Neutrophilic Lifestyle

Autor: Anna Zawilak-Pawlik, Bernd Appel, N.-J. Krüger, Marie-Theres Knüver, Kerstin Stingl
Jazyk: angličtina
Rok vydání: 2016
Předmět:
0301 basic medicine
Urease
Mutant
Pathology and Laboratory Medicine
Biochemistry
chemistry.chemical_compound
Helicobacter
Nucleic Acids
Medicine and Health Sciences
Pathogen
lcsh:QH301-705.5
Nucleotides
Organic Compounds
Microbial Genetics
Adaptation
Physiological
Bacterial Pathogens
Chemistry
Bioassays and Physiological Analysis
Medical Microbiology
Physical Sciences
Pathogens
Research Article
Chemical Elements
lcsh:Immunologic diseases. Allergy
DNA
Bacterial
030106 microbiology
Immunology
Biology
Research and Analysis Methods
Microbiology
Superoxide dismutase
03 medical and health sciences
Virology
Genetics
Bacterial Genetics
Humans
Molecular Biology
Microbial Pathogens
Bacteria
Helicobacter pylori
Adenine
Fluorescence Competition
Organic Chemistry
Wild type
Organisms
Chemical Compounds
Biology and Life Sciences
Genetic Variation
Bacteriology
Cell Biology
DNA
biology.organism_classification
Oxygen
Transformation (genetics)
Oxidative Stress
030104 developmental biology
chemistry
lcsh:Biology (General)
Purines
Gastric Mucosa
biology.protein
Parasitology
lcsh:RC581-607
Zdroj: PLoS Pathogens
PLoS Pathogens, Vol 12, Iss 5, p e1005626 (2016)
ISSN: 1553-7374
1553-7366
Popis: As a neutrophilic bacterium, Helicobacter pylori is growth deficient under extreme acidic conditions. The gastric pathogen is equipped with an acid survival kit, regulating urease activity by a pH-gated urea channel, opening below pH 6.5. After overcoming acid stress, the bacterium’s multiplication site is situated at the gastric mucosa with near neutral pH. The pathogen exhibits exceptional genetic variability, mainly due to its capability of natural transformation, termed competence. Using single cell analysis, we show here that competence is highly regulated in H. pylori. DNA uptake complex activity was reversibly shut down below pH 6.5. pH values above 6.5 opened a competence window, in which competence development was triggered by the combination of pH increase and oxidative stress. In contrast, addition of sublethal concentrations of the DNA-damaging agents ciprofloxacin or mitomycin C did not trigger competence development under our conditions. An oxygen-sensitive mutant lacking superoxide dismutase (sodB) displayed a higher competent fraction of cells than the wild type under comparable conditions. In addition, the sodB mutant was dependent on adenine for growth in broth and turned into non-cultivable coccoid forms in its absence, indicating that adenine had radical quenching capacity. Quantification of periplasmically located DNA in competent wild type cells revealed outstanding median imported DNA amounts of around 350 kb per cell within 10 min of import, with maximally a chromosomal equivalent (1.6 Mb) in individual cells, far exceeding previous amounts detected in other Gram-negative bacteria. We conclude that the pathogen’s high genetic diversity is a consequence of its enormous DNA uptake capacity, triggered by intrinsic and extrinsic oxidative stress once a neutral pH at the site of chronic host colonization allows competence development.
Author Summary Natural transformation, i.e. the capacity to take up DNA from the environment, is one of the crucial means for horizontal gene transfer and genetic diversity in bacteria. The human gastric pathogen Helicobacter pylori is confronted with acid stress before entering its multiplication site, the gastric mucosa. The bacterium causes lifelong chronic gastritis and is perfectly adapted to the human host, crucially by displaying unusual genetic diversity. Using a single cell approach and well-controlled conditions, we show here that the amount of imported DNA in competent H. pylori is outstanding, far exceeding previous measurement with other Gram-negative bacteria. Furthermore, DNA uptake activity was tightly regulated and limited to pH above 6.5, conditions thought to be met in close contact with the gastric mucosa. In addition, we show that within this pH competence window, competence development was triggered by an increase in pH in combination with the level of oxidative stress. Our data provide explanations for the extraordinary high genetic diversity, often referred to as genome plasticity of this unusual microaerobic pathogen.
Databáze: OpenAIRE
Externí odkaz: