Variable expression of extracellular polysaccharide in the marine bacterium Pseudomonas atlantica is controlled by
D H Bartlett1, M E Wright, M Silverman
1The Agouron Institute, 505 Coast Boulevard South, La Jolla, CA 92037.
Abstract:
Production of extracellular polysaccharide by the marine bacterium Pseudomonas atlantica is a variable trait. Strains that produce extracellular polysaccharide (EPS(+)) have a mucoid colony phenotype, but during cultivation in the laboratory nonmucoid, EPS(-) variants arise that have a crenated colony morphology. This change is reversible since crenated variants rapidly switch to the original mucoid phenotype. We have cloned the locus (eps) controlling variable expression of EPS production by screening a recombinant cosmid library for clones that restore EPS production in the crenated variant. By using eps as a probe of genomic structure in variant strains, expression of EPS production was found to be controlled by a specific DNA rearrangement. Insertion of a 1.2-kilobase-pair DNA sequence in the eps locus results in EPS(-), whereas excision of the sequence restores the EPS(+) phenotype. Properties of the rearrangement suggest the involvement of a mobile genetic element. The possible significance of this DNA rearrangement to the survival of P. atlantica in the ocean is discussed.
Related Concept Videos
Coordination of Gene Expression Processes in Bacteria
Stringent Response in E. coli
Gene Regulation in Microbial Communities: Quorum Sensing
Exon Recombination
Exon shuffling follows “splice frame rules.” Each exon has three reading...


