Production by Bacillus pumilus (MSH) of an antifungal compound that is active against Mucoraceae and Aspergillus species:: preliminary report

A compound produced by Bacillus pumilus (MSH) that inhibits Mucoraceae and Aspergillus species is described. Fungicidal activity was demonstrated by lawn-spotting and by diffusion through 0.45 mum Millipore membranes placed on 5% sheep-blood agar, nutrient agar, trypticase soy agar and Mueller-Hinton agar, followed by spore inoculation of the bacterium-free underlying agar surface. With either technique, zones of fungal inhibition correlated with the zone of haemolysis produced by B. pumilus (MSH). The active compound inhibited Mucor and Aspergillus spore germination and aborted elongating hyphae, presumably by inducing a cell-wall lesion. Antifungal activity was stable in agar for a minimum of 8 days, resistant to Pronase degradation, and partially inactivated by chloroform exposure and at pH 5(.)6. Its molecular mass was determined by diffusion through dialysis membrane to be 500-3000 Da. Attempts at further isolation of the compound have proven unsuccessful to date.