Provided is a bacterial strain which produces a family of mosquitocidal toxins, Xenorhabdus MT, on deposit with the American Type Culture Collection, PTA-6826, insecticidal compositions comprising the mosquitocidal toxin(s) produced by Xenorhabdus MT, a mosquitocidal toxin preparation prepared from spent culture medium, whole culture or cells or a mixture thereof, of Xenorhabdus MT and method of insect control, especially mosquito control. Also provided are microbial compounds (same as mosquitocidal toxins) compositions comprising them and use in formulating therapeutic and other antimicrobial compositions, and methods of use for inhibiting microbial growth and for treating infection.