Colony survival and morphology of A. niger wildtype and AB4.1 assayed with PLA and BA. The graph (A) shows colony survival under acid stress, the concentration (mM) of DL-PLA or BA is given on the x-axis. For wildtype strain N402, LA was added to a total acid concentration of 150 mM, and for AB4.1, LA was added to 100 mM. The y-axis represents the average number of observed colonies (from 4 replicates, normalized to an average of 25 colonies in the controls) after 3 days (controls) and 14 days (assayed samples). Error bar show standard error of the mean. The asterisks indicate colony numbers that were significantly different to all others in the same group (p < 0.01). Morphologies of N402 colonies incubated for 14 days on 90 mm petri dishes assayed with 1 mM benzoic acid and 149 mM LA (B), the uridine auxotroph strain AB4.1 on control plate with 100 mM LA (C), and AB4.1 assayed with 10 mM DL-PLA and 90 mM LA (D).