Maculosin

Maculosin is a diketopiperazine metabolite produced by A. alternata, L. capsici, Streptomyces, and the Gram-negative, nonobligate predator bacterial strain 679-2. It acts as a host-specific phytotoxin, inducing formation of weeping necrotic lesions in leaves of spotted knapweed (C. maculosa) when used at a concentration of 10 μM. Maculosin reduces the growth of the plant pathogenic bacteria X. axonopodis and R. solanacearum (MICs = 31.25 μg/ml) as well as the pathogenic oomycetes P. cactorum, P. capsici, P. cinnamomi, P. infestans, and P. ultimum when used at concentrations ranging from 10 to 100 mg/ml. Maculosin also inhibits the growth of M. luteus, M. smegmatis, S. cerevisiae, C. albicans, C. neoformans, and A. niger when used in combination with pyrrolnitrin or banegasin.