Effect of culture conditions on L-histidine decarboxylation activity of halophilic histamine-forming bacteria [Photobacterium phosphoreum and P. histaminum isolated from saltwaterfishes]

The effect of culture conditions on L-histidine decarboxylation activity of halophilic hista-mine-forming bacteria (Photobacterium histaminum (C-8) and P. phosphoreum (N-14)) were studied, and the results obtained with both strains were shown as follows. The decarboxylation activity of the cells of both strains was in general the highest at the beginning of the stationary phase of the growth and decreased gradually during the stationary phase. The culture conditions of both strains for temperature and initial pH value which showed the highest decarboxylation activity were 15 ?? 20°C and 4.5, the lowest pH value for supporting growth, respectively. The development of activity in bacterial cells of both strains was shown in the presence of more than 10-3 M of L-histidine. The decarboxylation activity decreased in the presence of histamine in the culture medium.