Affiliation:
1. Center for Adaptation Genetics and Drug Resistance, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111
Abstract
ABSTRACT
The annotation process of a newly sequenced bacterial genome is largely based on algorithms derived from databases of previously defined RNA and protein-encoding gene structures. This process generally excludes the possibility that the two strands of a given stretch of DNA can each harbor a gene in an overlapping manner. While the presence of such structures in eukaryotic genomes is considered to be relatively common, their counterparts in prokaryotic genomes are just beginning to be recognized. Application of an in vivo expression technology has previously identified 22 discrete genetic loci in
Pseudomonas fluorescens
Pf0-1 that were specifically activated in the soil environment, of which 10 were present in an antisense orientation relative to previously annotated genes. This observation led to the hypothesis that the physiological role of overlapping genetic structures may be relevant to growth conditions outside artificial laboratory media. Here, we examined the role of one of the overlapping gene pairs,
iiv19
and
leuA2
, in soil. Although
iiv19
was previously demonstrated to be preferentially activated in the soil environment, its absence did not alter the ability of
P. fluorescens
to colonize or survive in soil. Surprisingly, the absence of the
leuA2
gene conferred a fitness advantage in the soil environment when leucine was supplied exogenously. This effect was determined to be independent of the
iiv19
gene, and further analyses revealed that amino acid antagonism was the underlying mechanism behind the observed fitness advantage of the bacterium in soil. Our findings provide a potential mechanism for the frequent occurrence of auxotrophic mutants of
Pseudomonas
spp. in the lungs of cystic fibrosis patients.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
14 articles.
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