Aerobic Growth of Anaerobic Pathogens

厌氧病原体的需氧生长

基本信息

批准号：
8416323
负责人：
MICHAEL H MALAMY
金额：
$ 20.63万
依托单位：
TUFTS UNIVERSITY BOSTON
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-02-01 至 2014-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8416323
关键词：
Abscess Acute Address Aerobic Air Alleles Anaerobic Bacteria Anaerobiosis Animal Disease Models Animal Model Animals Antibiotic Therapy Antibiotics Bacteria Bacteroides fragilis Biochemical Biological Biological Assay Cells Characteristics Clinical Clostridium difficile Colon Coupled DNA Resequencing Diarrhea Disadvantaged Disease Environment Enzymes Epidemic Exposure to Extravasation Gene Expression Profile Genes Genome Gram-Negative Bacteria Gram-Positive Bacteria Greater sac of peritoneum Growth Habitats Hamsters Hydrogen Peroxide In Vitro Infection Intestines Large Intestine Maps Modeling Mus Mutagenesis Mutate Mutation NADH NADP Oxidants Oxygen Parents Pathogenesis Pathway interactions Peritoneal Peroxidases Phenotype Physiological Population Proteins Protocols documentation Pseudomembranous Colitis Reactive Oxygen Species Role Site Stress Sulfhydryl Compounds Testing Textbooks Thioredoxin Virulence Work base cell type electron donor ena protein genome sequencing member mutant novel null mutation pathogen pathogenic bacteria planetary Atmosphere prevent protein function transmission process

项目摘要

DESCRIPTION (provided by applicant): Two very different bacterial pathogens, the Gram-negative Bacteroides fragilis and the Gram-positive Clostridium difficile, have been considered as textbook examples of strict anaerobes that inhabit the large intestine. B. fragilis is a normal inhabitant of the colon, but C. difficile is usually found in people whose normal microbiota has been compromised by antibiotic treatment. B. fragilis is an opportunistic pathogen mainly associated with escape from the intestine due to leakage into and formation of abscesses in the peritoneal cavity. C. difficile, on the other hand, is the primary cause of antibiotic-associated diarrhea and pseudomembranous colitis. Given that the normal habitat for these bacteria is the anaerobic environment of the large intestine, it is remarkable that our preliminary results have shown that mutants of B. fragilis and C. difficile arise that can grow in the presence of oxygen (up to 2%) and can survive exposure to even higher oxygen levels. Many of these mutants have oxe (oxygen-enabling) null mutations that lie in a gene called oxeA that is conserved in the two otherwise very dissimilar species. Moreover, many clinical isolates of B. fragilis derived from abscesses can grow in 1.5% oxygen and have oxeA mutations as well. This application seeks to explain these unexpected findings by addressing a fundamental biological question: Why do anaerobic pathogens normally express genes whose products prevent them from growing aerobically? Our working hypothesis is that the wild-type product(s) of the oxe genes promote growth or survival in the anaerobic colon whereas the oxe mutations enhance some aspects of pathogenesis in animal hosts. To test this hypothesis we will compare the colonization, virulence and transmission of B. fragilis and C. difficile wild-type and oxe mutant strains in animal models of disease. In addition, we will seek to uncover the biochemical mechanisms by which the oxe gene products prevent survival and growth in low levels of oxygen. The results are expected to reveal a novel and surprising aspect of anaerobic growth.

描述（由申请人提供）：两种截然不同的细菌病原体，革兰氏阴性菌化菌Fragilis和革兰氏阳性艰难梭菌，被认为是严格吞咽的教科书示例，居住在大肠中。 B. fragilis是结肠的正常居民，但艰难梭菌通常在抗生素治疗损害的正常微生物群中发现。 B. fragilis是一种机会性病原体，主要与腹膜腔中脓肿的渗漏和形成，主要与逃离肠道逃脱有关。另一方面，艰难梭菌是抗生素相关腹泻和假膜结肠炎的主要原因。鉴于这些细菌的正常栖息地是大肠的厌氧环境，值得注意的是，我们的初步结果表明，在氧气（最高2％）的情况下会出现脆弱的和艰难梭菌的突变体，并且可以在暴露于更高氧气水平的情况下生存。这些突变体中的许多具有牛（增强氧）的无效突变，该突变位于一个称为Oxea的基因中，该基因在两个原本不同的物种中是保守的。此外，源自脓肿的脆弱芽孢杆菌的许多临床分离株也可以在1.5％的氧气中生长，并且也具有氧气突变。该应用程序试图通过解决一个基本的生物学问题来解释这些意外的发现：为什么厌氧病原体通常表达其产物阻止其有氧生长的基因？我们的工作假设是OXE基因的野生型产物促进了厌氧结肠中的生长或存活，而OXE突变则增强了动物宿主发病机理的某些方面。为了检验这一假设，我们将比较疾病动物模型中Fragilis和艰难梭菌野生型和Oxe突变体菌株的定殖，毒力和传播。此外，我们将寻求揭示OXE基因产物阻止氧气生存和生长的生化机制。结果预计将揭示出厌氧生长的新颖而令人惊讶的方面。