Effect of environmental conditions on the production of two extracellular proteolytic enzymes by Vibrio SA1.

The production of two extracellular proteases, an endopeptidase and an aminopeptidase, by the marine bacterium Vibrio SA1 was studied in batch cultures. The production of the proteases was induced during growth of the organism in peptone media and by several amino acids during growth in minimal media. It was repressed by easily metabolisable carbon compounds such as glucose, lactate and succinate during growth in peptone media. During growth in a lactate basal medium, phenylalanine was one of the best inducers and this amino acid was therefore used in further experiments. That lactate did not repress the synthesis of the proteases during growth in the lactate basal medium supplement with 2mM phenylalanine as an inducer, appeared to be a consequence of the low iron content of this medium. Growth curves of Vibrio SA1 on such media showed a period of linear growth during which protease production was observed. When the iron concentration was made sufficiently high to prevent linear growth, the synthesis of the proteases remained repressed. Apparently by imposing an iron limitation on the organism, catabolite repression by lactate was relieved. Similarly, when growth was limited by very low values of the dissolved oxygen tension in the medium, a high rate of protease synthesis was found which was immediately repressed when the oxygen limitation was released. The results indicate that the growth rate and/or a factor associated with the energy metabolism play a role in the regulation of the synthesis of the enzymes.