Award Date

5-2009

Degree Type

Thesis

Degree Name

Master of Science in Biological Sciences

Department

Life Sciences

First Committee Member

Eduardo Robleto, Chair

Second Committee Member

Ronald Yasbin

Third Committee Member

Helen Wing

Graduate Faculty Representative

Ronald Gary

Number of Pages

84

Abstract

This thesis contains three major sections: introduction, literature review and the project entitled: 'Identification of Arid Soil Inducible Genes in Pseudomonas fluorescens Strain Pf0-1'. The introduction section describes a general background, the current and potential applications of P. fluorescens and the main goal of this dissertation. The literature review chapter discusses two main areas. The first area offers insights about different types of in vivo expression technology (IVET) as a tool in gene identification. This section also describes the limitations of IVET, as well as the benefits over other methods for gene identification. The second part of the literature review is a compendium of previously reported genetic factors involved in soil survival. Finally, the last part of this thesis documents the identification of arid soil inducible gene in P. fluorescens strain Pf0-1.

This study, identification of arid soil inducible genes in Pseudomonas fluorescens , investigated adaptation mechanisms of Pseudomonas fluorescens strain Pf0-1 in arid soil. Auxotrophy-based in vivo expression technology (IVET) was employed to identify 26 arid-soil inducible genes in P. fluorescens. Based on analysis of Clusters of Orthologous Groups of proteins (COGs), ten genes are involved in metabolism; four genes are engaged in information storage and processing; three are signaling and regulation cellular processes genes; and nine are poorly characterized or hypothetical. Four genes of different functional groups (Pfl0l_2143: glutamine synthetase; Pfl01_2660: GTPase Subunit of Restriction Endonuclease like; Pfl0l_5595: hypothetical protein; and Pfl01_3972: putative diguanylate phosphodiesterase EAL domain) were inactivated and tested for their influence in soil colonization. Only two of the four strains carrying defective alleles showed slight but significant decreases in soil colonization. The growth patterns of mutant strains carrying defective alleles on Pfl01_2143 and Pfl01_5595 showed a decline in arid soil persistence, which were partially restored in strain derivatives carrying a complementing plasmid. Overall, these results indicate that adaptation of P. fluorescens to soil requires the expression of many genes, perhaps acting cooperatively. We further surmise that nitrogen limitation and metabolism are important factors in soil colonization in arid soils.

Keywords

Gram-negative bacteria; Microbial genetics; Pseudomonas fluorescens; Rhizobacteria; Soil microbial ecology

Disciplines

Bacteriology | Ecology and Evolutionary Biology | Environmental Microbiology and Microbial Ecology | Microbiology

Language

English

Comments

Signatures have been redacted for privacy and security measures.


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