Abstract: Killer toxins that may have activity against organisms, such as pathogenic organisms, and organisms that express the killer toxins are disclosed herein. The organism may be a recombinant organism or it may endogenously express a killer toxin. In some embodiments, a composition comprises one or more organisms, such as one or more Saccharomyces yeasts, and/or one or more killer toxins, such as K1, K2, and/or K1L toxins. In other embodiments, compositions comprise nucleic acids, vectors, host cells, or combinations thereof, comprising one or more killer toxins. Compositions can include one or more additional components, such as, but not limited to, a buffer, carrier, adjuvant, additional therapeutic, or combinations thereof. Kits that comprise one or more organisms and/or killer toxins are described. Uses of the organisms and/or killer toxins can include administration to a subject to treat an infection by one or more yeasts, such as Candida glabrata.