Effect of seawater on Escherichia coli β‐galactosidase activity

• Published in: Journal of Applied Bacteriology 1996-08, Vol.81 (2), p.174-180
• Main Authors: Pommepuy, M., Fiksdal, L., Gourmelon, M., Melikechi, H., Caprais, M.P., Cormier, M., Colwell, R.R.
• Format: Article
• Language: English
• Subjects: Bacteriological methods and techniques used in bacteriology; Bacteriology; beta-Galactosidase - biosynthesis; beta-Galactosidase - metabolism; Biological and medical sciences; Brackish; Chloramphenicol - pharmacology; Enzyme Induction; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - radiation effects; Fresh Water; Freshwater; Fundamental and applied biological sciences. Psychology; Light; Marine; Microbiology; Osmotic Pressure; Protein Synthesis Inhibitors - pharmacology; Seawater; Sewage - microbiology
• ISSN: 0021-8847; 2056-5232
• DOI: 10.1111/j.1365-2672.1996.tb04496.x

An investigation of β‐galactosidase activity of Escherichia coli strain H10407, under different physiological and environmental conditions, e.g. induced and uninduced osmotic stress, light, etc., was undertaken. In this study E. coli was employed as a model for faecal coliforms in waste water. β‐Galactosidase activity was induced by isopropyl‐β‐D‐thiogalactoside (IPTG). Enzyme activity (U cell‐1)/cell for sewage bacteria and for induced E. coli was similar, i.e. log U cell‐1= ‐8.5 whereas uninduced E. coli yielded log U cell‐1= ‐12.1. Initial enzyme activity was not dependent on phase of growth of the cell (exponential vs stationary phase) or whether marine or fresh water at the time of initial dilution. However, osmotic change resulted in a decrease in culturable cells, even though enzyme activity remained constant. A significant decrease in the number of culturable bacteria, followed by a decrease in β‐galactosidase activity, was observed after exposure of cells to visible light radiation. It is concluded that β‐galactosidase enzyme is retained in viable but non‐culturable E. coli. Furthermore, β‐galactosidase appears to offer a useful and rapid (25 min) measure of the viability of faecal coliforms, and therefore, of the water quality of bathing and shellfishing areas.