Phenotypic variation in exopolysaccharide production in the marine, aerobic nitrogen-fixing unicellular cyanobacterium Cyanothece sp

The aerobic nitrogen-fixing cyanobacterium, Cyanothece sp. BH68K produces non-mucoid variants defective in exopolysaccharide (EPS) production at a high frequency. The EPS-producing wild-type colonies (EPS(+)) have a characteristic smooth and shiny appearance which allows them to be easily distinguis...

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Published inWorld journal of microbiology & biotechnology Vol. 12; no. 4; pp. 311 - 318
Main Authors REDDY, K. J, SOPER, B. W, TANG, J, BRADLEY, R. L
Format Journal Article
LanguageEnglish
Published Dordrecht Springer 01.07.1996
Subjects
Biological and medical sciences
Biology of microorganisms of confirmed or potential industrial interest
Biotechnology
Cyanophyta
Cyanothece
Freshwater
Fundamental and applied biological sciences. Psychology
Miscellaneous
Mission oriented research
Variant
Microorganism growth
Phenotype
Aerobiosis
Ultrastructure
Cyanobacteria
Production
Nitrogen fixation
Bacteria
Extracellular
Polysaccharide
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Summary:The aerobic nitrogen-fixing cyanobacterium, Cyanothece sp. BH68K produces non-mucoid variants defective in exopolysaccharide (EPS) production at a high frequency. The EPS-producing wild-type colonies (EPS(+)) have a characteristic smooth and shiny appearance which allows them to be easily distinguished from the EPS(-) variants. When grown on agar plates lacking a source of combined nitrogen, the EPS(-) variants exhibited a yellow phenotype typical of nitrogen starvation. These EPS(-) variants showed varying degrees of reversion back to the EPS(+) phenotype. After reversion, they exhibited normal diazotrophic growth on agar plates. Alcian blue and ruthenium red staining indicated that the EPS is an acidic polysaccharide, which is present as a loose network around the cell, and which can be completely removed by low speed centrifugation. The accumulation of EPS takes place mainly during the stationary phase. All EPS(-) variants failed to produce any EPS. Analysis of growth of wild-type and EPS(-) variants revealed that EPS production is beneficial for diazotrophic growth on solid medium, but not in liquid medium. In addition, EPS phenotypic alteration may have some advantage in the dispersal of cells from one place to another in the natural environment.
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ISSN:0959-3993
1573-0972
DOI:10.1007/bf00340206