EFFECTS OF COPPER ON BACILLUS SUBTILIS

Abstract

Variants have been isolated from liquid cultures of Bacillus subtilis 168 after exposure to copper. The variations manifested are in terms of loss of capacity to be transformed from tryptophan auxotrophy to prototrophy as shown by variant NTCu, and in terms of colony size and altered base composition of the deoxyribonucleic acid as shown by variant SC-22. In addition to the data on altered morphology and chemical composition of the variants, detailed studies on the reversion of one of the variants to B. subtilis are presented. a "neutral form" and 67.1 % in an "alkali-producing" form. There would be important implications, including taxonomic considerations, if it could be demonstrated conclusively that large changes in the chemical composition and biological activity of the DNA of an organism can be brought about by environmental influences in the same sense that small changes in DNA have been brought about by ultraviolet irradiation and the chemical mutagens. The maximal chemical alteration in DNA consistent with survival of an organism has not yet been defined. Data will be presented on two variants which appeared in cultures of a tryptophan-requiring auxotroph of B. subtilis 168 exposed to copper. One variant (designated NTCu) is generally similar to the original strain in its morphological and colonial characteristics but differs principally in that it is no longer transformable to prototrophy by wild-type DNA. The other variant is a smallcolony form (designated SC-22). The DNA of this variant differs in both biological activity and chemical composition from the DNA of the parent organism. These variants are stable after many transfers in the absence of copper. MATERIALS AND METHODS Strains. B. subtilis 168 and 23 were first isolated by Burkholder and Giles (1947). Media. The minimal medium (Spizizen, 1958) employed contained, in addition to the salts, 0.5 % glucose, 0.02% casein hvdrolysate, and 0.005% L-tryptophan (designated as supplemented minimal medium). When agar plates containing minimal medium were made, the casein hydrolysate and tryptophan were omitted. Potato agar plates were prepared from a broth consisting of 200 g of potatoes, 1,000 ml of tap water, and 5 mg of MnSO4, all brought to a pH of 6.8. For plating, 15 g of agar were added. Tryptose Blood Agar Base (TBAB) plates were prepared from the standard Difco preparation. The medium (referred to as F.J. medium) first described by Fraser and Jerrel (1953) was modi-1003

Heterogeneity Among the Mycoplasma and Relationships to Bacteria*

“…Theoretically, it is conceivable, however, that these organisms might be mutants with altered base compositions. Mutants with altered G + C ratios have been described (Weed, 1963;Gause et al, 1964;DeLey, 1964).…”

Using the metabolic capacity of rhodobacter sphaeroides to assess heavy metal toxicity

“…Nevertheless, it is important to point out that the availability of the different metals can be influenced by chlorides or other kinds of salts present in natural environments (Babich and Stotzky, 1977). It has often been reported that the toxicity of a pollutant depends on the physicochemical characteristics of the environment into which the pollutant is deposited (Weed, 1963;Babich and Stotzky, 1977;Dean-Ross and Mills, 1989;Flemming and Trevors, 1989). In our work, we have not taken this into account because our aim was to perform a comparative and qualitative study, and not to define the exact physicochemical characteristics that determine the maximum toxicity.…”

Deoxyribonucleic Acid Base Composition in the Taxonomy of Staphylococcus

“…The GC content of encapsulated and nonencapsulated staphylococci, of strains recently DNA BASE COMPOSITION OF STAPHYLOCOCCUS isolated from clinical situations, and of the usual stock culture strains of staphylococci were in the range 33.2 to 34.9% ( 13,20). The significant differences reported by Beining and Kennedy (3) when staphylococci are grown in vivo and in vitro were not accompanied by detectable changes in the base composition.…”

“…The differential value of GC-content determinations in the Micrococcaceae is in more serious jeopardy if mutants of S. aureus with GC contents of 71% exist, as reported by Gause (8). Substantial change in base composition of an organism has also been reported in Bacillus by Weed (20) and in some very early work on Escherichia by Spirin et al (4).…”