Zwittermicin A is a novel antibiotic produced by Bacillus cereus UW85,
which suppresses certain plant diseases in the laboratory and in the
field. We developed a rapid method for large-scale purification of zwi
ttermicin A and then studied the in vitro activity of zwittermicin A a
gainst bacteria, fungi, and protists. Zwittermicin A was highly active
against the Oomycetes and their relatives, the algal protists, and ha
d moderate activity against diverse Gram-negative bacteria and certain
Gram-positive bacteria as well as against a wide range of plant patho
genic fungi. Zwittermicin A was more active against bacteria and fungi
at pH 7-8 than at pH 5-6. When zwittermicin A was combined with kanos
amine, another antibiotic produced by B. cereus, the two acted synergi
stically against Escherichia coli and additively against Phytophthora
medicaginis, an Oomycete. The results indicate that there are diverse
potential applications of this new class of antibiotic.