Physiological characteristics of strains of Group II C. botulinum. The minimum temperature and maximum NaCl concentration at which growth was observed, the minimum concentration of tellurite required to prevent growth and the ability to ferment selected carbohydrates was tested on strains representing different clades. Acid production was measured in a PY basal medium with 10 g l-1 added carbohydrate. A carbohydrate was considered to be fermented if the final pH was more than 0.5 units less than inoculated medium in the absence of carbohydrate. A pH reduction of 0.5-1.0 units was noted as acid production (+) and >1.0 was noted as strong acid production (++). For details of the hierarchical clustering dendrogram see Figure 5.