Sublethal pH decrease may cause genetic damage to eukaryotic cell: A study on sea urchins andSalmonella typhimurium

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Abstract
Further evidence is reported here of genetic and developmental damage that can be induced by a sublethal pH decrease. The effects of three inorganic acids (HCl, H2SO4, and H3PO4) on embryos and sperm from the sea urchinsSphaerechinus granularisandParacentrotus lividuswere evaluated. In addition, acidification of the medium was tested for spontaneous reversion to His+prototrophy inSalmonella typhimurium(strains TA97, TA98, TA100, TA102, TA1535) up to toxic levels, by both liquid incubation and agar plate incorporation.The induction of developmental and mitotic abnormalities inS. granularisconfirmed our previous observations onP. lividus. Embryotoxicity was exerted inS. granularismore severely by H3PO4than by HCl or H2SO4(pH 7 to 6), while the induction of mitotic abnormalities appeared at a pH of ≤ 6.5 irrespective of the acids used. By suspendingS. granularisorP. lividussperm in acidified filtered seawater (fsw) and then inseminating the eggs in natural fsw (pH = 8.0), the offspring showed developmental and mitotic abnormalities. Low‐pH‐induced spermiotoxicity was ruled out in our experiments, since fertilization success of acid‐exposed sperm was actually enhanced, as compared to sperm suspended in untreated fsw.The exposure ofS. typhimuriumto different pH's (ranging from 4 to 9) invariably failed to induce any changes in reversion rates, regardless of the acids (or alkali) being used.These results suggest that extracellular acidification may cause sublethal damage that in turn leads to an impairment of mitotic activity and cell differentiation.