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

Abstract

SUMMARY Bacteriological agar has been shown to be toxic towards Escherichia coli and Staphylococcus aureus. The effect was observed when nutrient agar was treated with Norit or ferric chloride and when the agar component alone was treated similarly. With both agents, larger colonies from untreated suspensions of Staph. aureus and higher counts from phenol treated suspensions of both species, were produced. Aluminium and chromium gave effects similar to those of iron, but iron gave the largest colonies of Staph. aureus. Magnesium also was especially successful in inducing high counts of damaged cells. A batch of Japanese agar, although apparently of poor quality, was superior by both the above criteria to two batches of New Zealand agar; but all three batches of agar were toxic to some degree.

The Influence of the Recovery Medium and the Incubation Temperature on the Survival of Damaged Bacteria

“…Alper & Gillies (19583) attributed the relatively poor performance of Oxoid Blood Agar Base for such organisms to ionizable chloride, which nevertheless gave more rapid growth of undamaged cells. With phenol treated cells, supplementation of nutrient agar with iron, chromium, aluminium and especially magnesium, gave improved revival (Jacobs & Harris, 1961), and the beneficial effect of ferric chloride has been reported also by Harris, Richards & Whitefield (1961). Similar effects with liquid media and phenol treated cells have been reported by Flett, Haring, Guiteras & Shapiro (1945) and Jacobs & Harris (1960), and very marked responses were observed by when cation supplemented media were used with membrane filters.…”

A comparison of solid and liquid media for resuscitation of starvation- and low-temperature-induced nonculturable cells of Aeromonas hydrophila

“…Lower recoveries in agar media than in liquid have been attributed to impurities in the agar (Jacobs and Harris 1961;Pellon and Gomez 1979), cell density effects (Payne 1978) or limited diffusion of nutrients to cells and of toxic products away from cells (Miller and Davey 1965). In our case, it is possible that a toxic product, e.g.…”

Metabolic Injury in Frozen Bacteria

“…Enrichment of mutants. Attempts to enrich the proportion of mutants in populations were made using the penicillin procedure of Lederberg (1950).…”

“…The fact that metabolic injury could be observed by MPN determination suggested that toxic materials in agar (Jacobs & Harris, 1961) were not contributing to the phenomenon. Some data were obtained using minimaJ medium supplemented with 0.1% of Norit or 0.03% of ferric chloride as recommended by Jacobs & Harris (1960 to remove toxic materials from rich media.…”