The action of arsenic on Bacillus cereus

Abstract

Sodium arsenite (0–4 mm) inhibited the growth of exponentially growing Bacillus cereus, whereas sodium arsenate was growth‐inhibitory only at 10 mm concentration. When the phosphate concentration was reduced sharply, 3.3 mm sodium arsenate inhibited growth, whereas the inhibitory effect of arsenite was independent of phosphate concentration. Neither arsenite nor arsenate produced any specific effects on the incorporation of precursors into ribonucleic and deoxyribonucleic acids, protein or cell wall, in support of the concept that their actions were at stages of energy utilisation rather than biosynthesis of macromolecules. Although some 74arsenate may have been bound by cells during inhibition of growth, 74arsenite was selectively and potently concentrated in micro‐organisms. There was no evidence for the formation of arsenic‐containing nucleic acids nor were labelled organic intermediates found. No instance of interconversion between pentavalent and trivalent states of arsenic could be established, and it was concluded that both compounds inhibited the growth of B. cereus by separate mechanisms.

Specificity of Phenotypic Adaptation of Bacillus Cereus to Tetracycline

“…In both cases, the resistant bacteria contained less drug than did the sensitive ones (Connamacher et al 1967;Mandel et al 1965). In the author's experience, the recovery from both compounds must occur within 3 hr or not at all.…”

“…Because both tetracycline (Jones & Morrison, 1962) and arsenite (Mandel et al 1965) have been shown to interrupt the energy production of the cell, other energy inhibitors and active transport inhibitors were tested for reversible bacteriostatic action. Ouabain (IO-~ M) did not inhibit Bacillus cereus, nor was bacterial inhibition observed with up to I O -~ M-phloridzin, 2,4-dinitrophenol, ethionine, potassium fluoride, amobarbital, or malonic acid.…”

“…In each case, recovery has been due to a decreased intracellular concentration of the inhibitory agent with very little chemical change of the drug. And yet each agent is believed to act by a different mechanism: tetracycline by binding to the 30s ribosomes at the point reserved for tRNA (Connamacher & Mandel, 1968) and arsenite by competition with phosphate in energyproducing mechanisms (Mandel et al 1965). Because of the similarity in the way the bacteria adapt to the two very different substances, it seemed possible that we were working with a general adaptive mechanism to any toxic agent.…”

Toxicity of Arsenite and Arsenate to the Marine Macroalga Champia Parvula (Rhodophyta)

“…Only a few reports are available on the effect of phosphate on both As(II1) and As(V) toxicity, and the relationship of phosphate concentration to the toxicities is confused because different taxa respond differently. As with C. parvula, the toxicity of As(II1) to the bacterium Bacillus cereus was independent of phosphate concentration, but the toxicity of As(V) could be increased by lowering the phosphate concentration [7]. However, in some fungi, phosphate concentration affects the toxicity of both As(II1) and As(V) [8].…”