Type of Document Dissertation Author Rinzan, Fathima Faraz Author's Email Address frinzan@student.gsu.edu URN etd-04172009-223223 Title PSEUDOMONAS AERUGINOSA-CANDIDA ALBICANS INTERACTIONS FROM ECOLOGICAL AND MOLECULAR PERSPECTIVES Degree Ph.D. Department Biology Advisory Committee
Advisor Name Title Sidney A. Crow, Jr. Committee Chair George E. Pierce Committee Member Richard A. Calderone Committee Member William A. Fonzi Committee Member Keywords
- PAO1 genomic library
- Attachment
- Morphogenesis
- Adhesins
- LecB
- Carbohydrate inhibition
- Primary attachment
- Candida albicans
- Pseudomonas aeruginosa
Date of Defense 2009-04-07 Availability unrestricted Abstract Pseudomonas aeruginosa and Candida albicans have shown antagonistic relationships, both in vivo and in vitro. The interaction between P. aeruginosa and C. albicans is one of the many prokaryotic-eukaryotic interactionsexisting in nature and needs more research due to their complex pathogenicity in humans. In this
work, we have studied growth dynamics of Candida in a mixed population of
Pseudomonas and Candida, and their receptor and ligand specificities, both from
an ecological and a molecular point of view. Initially, growth, viability, and morphogenesis of
Candida were studied in the presence of Pseudomonas and the conditioned medium
of Pseudomonas using two Candida strains, namely CAF2 and tup1 mutant. The killing effect of Pseudomonas was more pronounced on the hyphal form of Candida. However, growth of Candida was inhibited by Pseudomonas irrespective of its morphological form. The conditioned medium had no effect on the growth rate of Candida. Nevertheless, it completely inhibited the germination of Candida. The attachment of Pseudomonas to Candida was studied using different strains of both, and with Pseudomonas cells harvested at different stages of its growth. The percent
attachment varied with the age of the textit Pseudomonas culture. A lecB mutant of
Pseudomonas showed a two-fold reduction in attachment compared to the wild type PAK
strain. Carbohydrate inhibition studies confirmed that LecB is not directly involved in the
attachment mechanism, but indirectly involves through regulating the expression of other proteins required for attachment.
A genomic DNA library of Pseudomonas PAO1 was screened for clones that had acquired the
ability to attach to C. albicans. A clone was isolated with a small increase in attachment
and was subjected to genetic analysis. It contained nucleotides 458565 to 475917 of the
Pseudomonas genome including some genes of the Pil-Chp gene cluster. Seven transposon
mutants that represent mutations in ChpA,B,C,D,E operon and three other ORFs were selected, and
their attachment ability was tested. All seven mutants showed a reduction in attachment indicating that this was a non specific effect, which could be attributed to the in vitro manipulation of the bacteria. We conclude that the attachment of Pseudomonas to Candida is
multi-factorial.
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