# GENETIC SYSTEMS TO STUDY VIRULENCE BACTEROIDES FRAGILES

> **NIH NIH R01** · TUFTS UNIVERSITY BOSTON · 1992 · $225,684

## Abstract

The long term objective of this proposal is to understand the factors that
contribute to the virulence and pathogenicity of B. fragilis, the most
important anaerobic pathogen in suppurative intra-abdominal and pelvic
infections in man. Since this requires a genetic and physiological analysis
ofthe virulence factors, our approach has been to develop new genetic
systems for use in B.fragilis in order to identify potential virulence
determinants. We are focussing on the aero-tolerance of B fragilis as an
important factor in the organisms' ability to survivein oxygenated tissue,
and the neuraminidase which may be important for B. fragilis to adhere to
host cells and derive essential nutrients from the environment. Since many
cell envelope proteins play a role in bacterial pathogenicity, we will use
a modified TnphoA transposon to identify new virulence factors among B.
fragilis surface or exported proteins. Mutants with alterations in
potential virulence factors will be tested for their ability to grow in two
model systems of B. fragilis infection.

The first aim is to continue to analyze factors that may play a role in the
virulence of B. fragilis: a. B. fragilis neuraminidase. We will create B.
fragilis isogenic mutants that differ only in the neuraminidase structural
gene and test their properties in the model systems. We will study the
sequences and factors that localize neuraminidase in B. fragilis and E.
coli. We will determine how neuraminidase expression is controlled in B.
fragilis. b. Aero-tolerance may be an important reason why B. fragilis is
the pre-dominant pathogen of the Bacteroides group. To test this hypothesis
we will isolate catalase deficient mutants and determine if they are
aero-sensitive. If this is so, we will study catalase deficient B. fragilis
strains in the model systems of infection. If these strains have reduced
ability to survive in the model systems, we will then identify the catalase
structural gene and study the regulation of catalase expression in B.
fragilis.

The second aim is to use TnphoA mutagenesis to identify genes that code for
B.fragilis exported proteins and test the mutants for alterations in their
ability to grow in the two model systems: a. We will modify TnphoA to
contain a marker that is selectable in B. fragilis. b. We will mutagenize a
B. fragilis chromosomal library in E. coli and transfer the mutagenized
plasmids to B. fragilis selecting for phoA+ fusions in-the chromosome.

The third aim is to test mutants in potential virulence factors in a tissue
culture and Rat Pouch model system of B. fragilis infection: a. The tissue
culture model will test for aero-tolerance and colonization factors. b. The
Rat Granuloma Pouch is a true in vivo system. In addition to testing
factors important in the tissue culture system, it also tests for the
response of the organism to the full array of host defense mechanisms
including an active immune system.

## Key facts

- **NIH application ID:** 3128856
- **Project number:** 5R01AI019497-09
- **Recipient organization:** TUFTS UNIVERSITY BOSTON
- **SAM.gov UEI:** C1F5LNUF7W86
- **Principal Investigator:** MICHAEL H MALAMY
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1992
- **Award amount:** $225,684
- **Award type:** 5
- **Project period:** 1983-01-01 → 1994-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3128856

## Citation

> US National Institutes of Health, RePORTER application 3128856, GENETIC SYSTEMS TO STUDY VIRULENCE BACTEROIDES FRAGILES (5R01AI019497-09). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3128856. Licensed CC0.

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