A strain of Clostridium bifermentans individualized as serovar malaysia (C.b.m.) according to its specific H antigen is toxic to mosquito and blackfly larvae when given orally. The toxicity occurs in sporulated cells which contain, in addition to spores, proteinic parasporal inclusion bodies and feather-like appendages; the amino acid content of the inclusion bodies is similar to that of Bacillus thuringiensis serovar israelensis (B.t.i.) and B. sphaericus crystals. The toxicity to Anopheles stephensi is as high as that of B.t.i. and the best strains of B. sphaericus. Culex pipiens is somewhat less susceptible, and Aedes aegypti much less. Pure parasporal inclusion bodies, isolated by ultracentrifugation on sucrose gradients, are highly toxic to mosquito larvae. The larvicidal power is destroyed by heating at 80 degrees C or by treatment with 50 mM NaOH. It is preserved by freeze-drying. The innocuity to mice of the sporulated cells is shown by different routes of administration: force-feeding, percutaneous, subcutaneous, intraperitoneal or intravenous injections. The potential for the biological control of mosquito and blackfly larvae is suggested.
Although the microbiome of blood-feeding insects serves an integral role in host physiology, both beneficial and pathogenic, little is known of the microbial community of black flies. An investigation, therefore, was undertaken to identify culturable bacteria from one of Malaysia's most common black flies, Simulium tani Takaoka and Davies, using 16S rDNA sequencing, and then evaluate the isolates for antibiotic resistance and virulence genes. A total of 20 isolates representing 11 bacterial species in four genera were found. Five isolates showed β-hemolysis on Columbia agar, and virulence genes were found in three of these isolates. Some degree of resistance to six of the 12 tested antibiotics was found among the isolates. The baseline data from this study suggest rich opportunities for comparative studies exploring the diversity and roles of the microbiome of S. tani and other Southeast Asian black flies.