Bacterial meningitis and pneumonia are responsible for a large worldwide disease burden, greater than other better-funded pathogenic diseases like HIV/AIDS and malaria. One of these pathogens, Haemophilus influenzae, inhabits the upper respiratory tract of most people, usually with no negative effect, but can cause several diseases-including meningitis, pneumonia, and ear infections-in infants, the elderly, and immune- compromised individuals. Like many other bacterial pathogens, H. influenzae can consume DNA by transporting it into their cells, breaking it down and reusing the subunits. But some of this DNA can recombine with a cell's own chromosome, interchanging versions of genes and adding or deleting genes. This natural competence mechanism allows related bacteria living in the same host to share genes, hastening their adaptation to host defenses and therapeutic interventions. The proposed research will link molecular studies of transformation with epidemiological studies of natural genetic diversity by experimentally measuring the chromosome-wide consequences of natural transformation. I will use the genomic DNA of clinical isolates to transform the chromosomes of competent recipient cells, and I will then apply massively parallel DNA sequencing to measure the extent and limits of natural transformation. I will use two complementary approaches: (1) measure the extent of transformation in a set of individual recombinant clones, and (2) measure the frequency of transformation across the chromosome from cultures of transformed cells. This research will be the first comprehensive experimental evaluation of genetic exchange in a human pathogenic bacterium (or any bacteria).

Public Health Relevance

Understanding the limits of natural transformation has important public health value. Genetically heterogeneous bacteria in the same environment can share genes using the natural competence mechanism, offering a route for pathogens to exchange antibiotic resistance genes, virulence factors, and variants of antigenic surface markers. The explosion of genome sequences of naturally competent bacteria reveals extensive evidence of pervasive recombination between different pathogenic bacterial isolates, but the role of intrinsic biases in the natural transformation pathway for different DNA sequences has not been systematically addressed.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
1F32AI084427-01A2
Application #
8060086
Study Section
Special Emphasis Panel (ZRG1-F08-E (20))
Program Officer
Khambaty, Farukh M
Project Start
2011-03-01
Project End
2014-02-28
Budget Start
2011-03-01
Budget End
2012-02-29
Support Year
1
Fiscal Year
2011
Total Cost
$45,192
Indirect Cost
Name
University of British Columbia
Department
Type
DUNS #
251949962
City
Vancouver
State
BC
Country
Canada
Zip Code
V6 1-Z3