The Effect of Environmental Conditions on the Viability and Growth of Bacteria Damaged by Phenols

Abstract

SUMMARY The effects of various environmental conditions on the viability and growth of normal Escherichia coli and Staphylococcus aureus cells, and of cells of these species which had been damaged by exposure to phenol, o‐cresol and p‐chloro‐m‐cresol, have been examined. With normal cells none of the conditions tried had any effect on the initial counts, but sometimes, more often with Staph. aureus, the bulk of growth eventually obtained in broth media was larger, especially when the medium had been made with pyridine extracted peptone, or when it had been treated with 0·1% of Norit charcoal or 0·02% of FeCl3. In contrast, damaged cells of both species were very sensitive to their environment. At room temperature, 0·1% of Norit added to tap water adsorbed more than 80% of the cells and the initial count was increased. Nevertheless the cells died thereafter. Damaged cells inoculated into broth also died, but when Norit was present both the rate and the extent of death were markedly reduced, though few cells were adsorbed. The addition of FeCl3 (0·02 or 0·03%) had no effect. At 37° damaged cells died faster than at room temperature, but the protective effect of Norit was still evident. In nephelometric studies of cultures growing in Norit treated broth the times to turbidity were shorter than those of control cultures in untreated broth, but broth treated with FeCl3 often gave longer times than the controls. In a comparison of broths prepared with peptone and/or Lab‐Lemco which had been extracted with pyridine to remove suspected toxic substances, the initial counts of treated cells were highest when only the peptone had been extracted. With media containing extracted Lab‐Lemco, or with both ingredients extracted, the counts were smaller but were still generally higher than in normal broth. The results of nephelometric studies were consonant with these findings: broths prepared with extracted ingredients generally gave shorter turbidity times than normal broth, especially with E. coli. The addition to broth of cations, especially Mg2+ (10–3 M), favoured the survival of damaged E. coli but did not influence that of Staph. aureus. But with both species, five times that concentration of Mg2+ was as effective as 0·1% of Norit, which was shown to adsorb lead, tin, copper, zinc, silver and cobalt from broth. Temperatures above 37° were unfavourable to the survival of damaged cells of both species, 44° often being completely inhibitory for Staph. aureus, but this effect was not due to traces of phenol in the inoculum. At 25° damaged E. coli recovered less well than at 30° and 37°, but damaged Staph. aureus did better at 25° and 30° than at 37°.

The Effect of Modifications in the Counting Medium on the Viability and Growth of Bacteria Damaged by Phenols

“…It is well known that in disinfection experiments considerable variations occur in the results, and in this work there is an indication that the magnitude of the response in a particular experiment was greater when the control count was smaller, an effect already commented upon briefly in a previous paper (Jacobs & Harris, 1960). Because of this, and despite the occurrence of large effects, formal statistical proof of the significance of differences due to treatment was difficult to obtain.…”

“…The fact that treatment of the agar component of nutrient agar with Norit or ferric chloride-broth precipitate resulted in increased counts of bactericide treated bacteria, and larger colonies, is evidence of the presence in agar of substances toxic especially to damaged cclls, such as have already been demonstrated in broth constituents (Jacobs & Harris, 1960). Further evidence that broth constituents are toxic is also afforded by the present work, since a medium prepared from treated broth and treated agar, or which contained Norit or ferric chloride, gave higher counts than one in which only the agar component had been treated.…”

“…This response to the presence of Norit seemed larger than was probable from previous experiences with liquid media (Jacobs & Harris, 1953, 1960, so it was decided to determine whether the adsorbents affected the broth, the agar or both.…”

“…to phenols of the inclusion of Norit or ferric chloride in nutrient media (Jacobs & Harris, 1953, 1954, 1960, it was concluded that any favourable effect, that these adjuvants might have on the viability and growth of phenol treated cells was due to their action on the medium, rather than on the organisms. Thus it became of interest to see what effects these substances had when added to solid media.…”

Radiosensitization of Streptococcus faecalis and Escherichia colia

“…The most toxic classes of compounds Elimination of the bactericidal action may not, of were those having amino or hydroxyl groups in course, prevent partial damage to a cell. This the 1 and 2 positions of the naphthalene ring problem has been recognized and discussed by Jacobs and Harris (1960) in their study of disinfectants. Exposure of cells to heat or chemicals, such as phenolic.…”