The class-specific pH optima for serine (vertical axis) and metalloproteinases (horizontal axis) for the fungus gardens in Table 1 for which both pH optima could be measured from the same samples. The vertical axis is interrupted to allow the pH-optimum to be plotted for metalloproteinase activity in gardens where serine proteinase activity could not be measured. The overall pattern indicates that pH optima for metalloproteinases are always between ca. 5 and 6, whereas serine proteinase pH optima tend to fall between 7 and 8. All values are means ± SEMs. Dotted lines connect observations for the same species. See Table 1 for details.