A quantitative study on the survival of bacteria following exposure to the CO2 laser was determined at the skin surface and in the plume. Known quantities of bacteria were inoculated onto the surface of fresh pig skin and exposed to timed bursts of the radiation. Results indicate that the bacterial population at the skin surface was reduced by several orders of magnitude while the potential for spread of bacteria by the plume of smoke was negligible.
Bacteriophage SP-15, a large generalized transducing phage of Bacillus, was compared with phages PBS-1 and SP-10 for the ability to cotransduce pairs of genetic markers exhibiting different degrees of linkage. When auxotrophs of B. subtilis W-23 were used as recipients, SP-15 and PBS-1 effected a much higher frequency of cotransduction than did SP-10 with markers that were not closely linked. With more closely linked loci, the differences were not as great. SP-15 cotransduced linked markers at a higher mean frequency than PBS-1, suggesting that SP-15 is able to transfer a larger fragment of the Bacillus genome than any phage heretofore described. The frequency of the joint transfer of genetic markers in B. licheniformis was lower via transforming deoxyribonucleic acid than by transduction with phage SP-10. The availability of three procedures for genetic exchange-transduction by SP-15 and SP-10 as well as transformation-each of which reveals a different degree of linkage, makes B. licheniformis 9945A especially amenable to genetic analysis. Recently, Tyeryar et al. (28) demonstrated in Bacillus licheniformis that for a given pair of genetic markers the frequency of cotransduction by phage SP-15 was higher than the frequency (23,24). Peptone diluent contained 10 g of Difco 1027on July 4, 2020 by guest
for very similar, and possibly identical, phages. Similar particles were described by F. A. Eiserling and W. R. Romig (Bacteriol. Proc., p. 118, 1964). We shall refer to these particles as PBSX-like or simply as defective phages. An examination of Table 1 reveals a strong correlation between inducibility for PBSX-like phages and susceptibility to SP-10(C). The first column represents a compilation of the published data on the inducibility of the strains listed plus our own data for B. subtilis strains 168 ind and W-23-Sr. It should be noted that W-23_Sr is inducible for another type of defective phage that is active on the Marburg strain (13; Eiserling and Romig, Bacteriol. Proc., p. 118, 1964), which we are not concerned with here. In general, those strains that harbor the defective prophage, as revealed by their inducibility for and resistance to PBSXlike particles, are insensitive to SP-10(C), even though the phage adsorbs well to them (Table 1, column 4). On the other hand, strains that are free from the defective prophage are sensitive to SP-10(C). Strain A-resistant 32 was isolated as a mutant of W-23, to which the defective phage was unable to adsorb (L. Glaser, personal communication). The sensitivity of this mutant to SP-10(C) suggests that different receptor sites are involved in the adsorption of SP-10(C) and the defective phage. These results implicate prophage-determined immunity as a factor in the resistance of B. subtilis 168 ind7 to SP-10(C). Sensitization of B. subtilis 168 ind to SP-10(C) after induction with UV light or MC. If prophage-determined immunity were responsible for insensitivity to SP-10(C), one should be able to lift the immunity via induction, thereby sensitizing the cells to the phage. Preliminary attempts to demonstrate an increase in phage yield over
Transfer of chromosomal markers between cells of Neisseria gonorrhoeae does not require the presence of a 24.5-megadalton conjgal plasmid in the donor. Apparent conjugal transfer of chromosomal markers may be the result of leakage of deoxyribonucleic acid by some cells in the mating mixture and subsequent uptake of this deoxyribonucleic acid by others.
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