Paradoxical Inhibition among Bacteria. Characterization of the Phenomenon and Nature of the Genetic Process

Abstract

(pi.) manifests itself as well-defined growth of a sensitive bacterium in the centre of the zone of inhibition overlying an area of growth of the inhibitory bacterium. Bacteriocin typing medium (BTM) for Vibrio cholerae elicited p.i. for this group only. A medium for paradoxical inhibition (MPI) was devised which supported the development of p i among members of Enterobacteriaceae, Vibrio and Alcaligenes spp. at high frequency. The reacting pair of strains could belong either to the same or to different genera. Colonies of non-bacteriocinogenic strains derived from the central area of p i showed acquisition of bacteriocinogeny at high frequency. Acquisition was rapid in the beginning (up to 4 h) followed by a decline and virtual disappearance of bacteriocinogeny by I 8 h on MPI, but was substantially retained on BTM. The overall frequency of acquisition among cell populations of different strains varied between 10-1 and IO-*, and the acquired characters were stable. Acquisition did not require either cell contact or participation of phages, but depended upon extracellular diffusable agents that were DNase sensitive and RNase resistant. A mutational basis for such acquisition could be ruled out, and the process of gene transfer was considered to be transformation. The extra-chromosomal nature of the determinants of bacteriocinogeny in the bacteria studied was suggested by effective elimination of these markers by sodium dodecyl sulphate and acridine orange.

Antibacterial Activity of Ambodryl and Benadryl

“…Escherichia coli Row (K-12), Shigella flexneri 3 189, Salmonella typhi 59, Vibrio cholerae 547, Staphylococcus aureus NCTC 8532 and Bacillus pumilus NCTC 8241 (Chakrabarty & Dastidar 1974) were used initially for screening the antibacterial activity of the antihistamines. In subsequent studies, 298 strains belonging to 14 different [209l Six and two strains each of V .…”

Transformation with Bacteriocin Factors in Staphylococci

“…and transformation on BTM. The role of SDS in such processes, and in the mechanism of release of transforming DNA, had been discussed under similar situations (Chakrabarty & Dastidar, 1974). SDS at the concentration (0.008 %) used in MPI is unlikely to release DNA by lysing primary bacteria, but it could probably do so (i) by increasing the spontaneous breakdown of bacteria (Elek, 1959) and (ii) by releasing intracellular macromolecules as a result of its selective action on the cell membrane (Sonstein & Baldwin, 1972; Woldringh & van Iterson, 1972).…”

“…(Chakrabarty & Dastidar, 1974). However, the acquisition process among the former appears to be more stable on MPI in comparison with that for other bacteria studied (Chakrabarty & Dastidar, 1974) because the acquired bacteriocin factors were substantially retained for 18 h or more. The causes for such a difference are not understood.…”

Incidence and Elimination of R Plasmids in Vibrio cholerae

“…that of bacteriocinogeny (1,4), and that independent elimination of each plasmid for antibiotic resistance and bacteriocinogeny occurs; this is most readily interpreted on the basis that each of these is determined by an independent plasmid.…”