THE MUTAGENIC ACTION OF FORMALDEHYDE ON BACTERIA

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Abstract
The mutagenicity of formaldehyde in the bacteria is demonstrated by: (1) the large absolute increase in "end point" itaconate-positive mutants of Pseudomonas fluorescens and (2) the relative increase in "end point" mutants of Escherichia coli, strain B, to phage resistance (T1), under conditions in which the factors of growth and selection were excluded. Large differences in viable counts of formaldehyde-treated cells on dif-ferent media indicate that certain media reactivated formal-dehyde-inactivated cells. Mutant counts of formaldehyde-treated cells based on 10-1 dilution plates were considerably lower than counts based on 10[degree] plates in the range of low survival. As the concn. of organisms per plate increased, this discrepancy disappeared. This may be the result of the phenomic lag in the expression of formaldehyde-induced mutations or a manifestation of the reactivation phenomenon.