The effects of certain phages of Bacillus spp. on the larvicidal potency of B. thuringiensis and B. sphaericus¹

Abstract

The pages: 0 -5 1 and CP-54 of Bacillus cereus, together with P-4 and P-14 of B. sphaericus were tested against B. thuringiensis and B. sphaericus strains. P-4 and P-14 were more different in their host range than the other two phages. Results of the bioassay against Culex pipiens larvae presented the inhibition in the larvicidal effects of phage-infected bacteria. Such inhibitory action varied according to the phage and the entomopathogenic bacterial strains. Materials and methods BacteriaBacillus thurin iensis (H-14), B. thuringiensis (Berliner), B. cereus, B. sphaen'cus (1881,2362, 1593 and 114) were useias entomo athogens. These bacterial strains were maintained on nutrient media after single colony isolation a n 1 propagation. PhagesPhage 0 -5 1 and 0 -5 4 were obtained from Dr. THORNE, Univ. Massachusetts, U.S.A., together with B. cereus 569 as their propagative host. P-4 and P-14 were kindly provided by Dr. YOUSTEN, Virginia, U.S.A., and their hosts B. sphaevicus 1593, 188, and 2362. ' This work was financially supported by WHO project TDR program. U.S. The effects of certain phages of Bacillus spp. Host range of phages 177Infectivity of the 4 phages were tested on their pro er hosts as well as 6 other Bacillus spp. Logarithmic bacterial broth culture was infected with tRe specific phage and incubated at 30 "C for 24 h. Pha e stock was obtained by centrifugation of phage, infected culture at 4000 r.p.m. for 30 min or througf Ultra membrane filtration. Phage stocks were titrated and preserved. Assay of phage titers45 55 B. sphaericus -1881 22 49 B. sphaericus -2362 21 43 B. sphaericus -1593 27 73 89 1 1 B. sphaericus -114 23 77 B. sphaericus -114 B. t urzngtenszs H-14 42 58 21 79 B. sphaericus -114 B. sphaericus -1881 58 13 B. sphaericus -2362 32 32 B. sphaericus -1593 31 69Bacteria in distilled H20