ABSTRACT

The original intent of this project was to study an extracellular amylase produced by a halophilic bacterium isolated from an inland salt spring.  One isolate, RS6, was found to produce amylase using the starch-iodine assay.  However, the amylase from this microorganism was found to be insufficient to obtain quantitative measurements using several different assays.  In an attempt to increase the amylase activity, the cultural conditions were changed and various additives were added.  The attempts were unsuccessful in elevating amylase activity for characterization.

The starch-iodine assay was further developed to quantitate amylase activity on agar plates containing soluble and insoluble forms of starch, amylose and amylopectin, respectively.  However, it was noted that growth and amylase production of RS6 was inhibited on a growth medium containing soluble starch.  Upon investigation of the phenomenon using soluble starch from a different source and various monosaccharides and disaccharides, it was discovered that it was probably glucose and maltose contaminating the original soluble starch since both glucose and maltose, subunits of starch, severely inhibited the growth of RS6.  Further experiments demonstrated that glucose specifically inhibited the growth of RS6 since two other microorganisms were not affected by glucose in the medium.  RS6 mutants were isolated that grew very well on media containing glucose, suggesting that the inhibition of growth by glucose is due to a specific gene within the original RS6 isolate.

The mechanism for this unusual growth inhibition by a universal energy source for organisms remains to be determined.