The Effect of Oxidative Rancidity in Unsaturated Fatty Acids on the Germination of Bacterial Spores

Abstract

It has been reported that some lots of commercial media contain substances that inhibit germination of anaerobic spores which can be overcome by adding starch (Foster and Wynne, 1948a). Foster and Wynne ascribed this activity to the unsaturated C18 fatty acids. Halvorson (1950) suggested that this effect may be due to the formation of peroxides from the fatty acids. This investigation was undertaken to test the latter hypothesis. MATERIALS AND METHODS Organisms used. The routine test organism was a putrefactive anaerobe, strain P.A. 3679. Later tests were also run on Clostridium botulinum, strain 7948, Clostridium pasteurianum, strain 7040, Bacillus subtilis, strain of Upjohn Company, and Bacilus stearothermophilus, strain NCA 1518. Preparation of spore suspensions. Anaerobic spores were collected after inoculating Blake bottles containing Yesair's pork infusion agar (Wynne and Foster, 1948) with a suspension of cells containing both spores and vegetative cells. The inoculum for each bottle consisted of 1.5 ml of a 72 hour egg-meat culture (Difco). The bottles were incubated for one week at 37 C in a desiccator which had been evacuated and the air replaced with natural gas. Cells were harvested by washing off the agar surface with sterile distilled water.

Relation of Fatty Acids to the Inhibition of Clostridium botulinum in Aged Surface Ripened Cheese12

“…The effectiveness of fatty acids varied in suppressing germination of C. botulinum spores in two different lots of the same medium. In contrast to the above findings, Roth and Halvorson (1952) reported that as much as 1.0 per cent of nonrancid methyl esters of oleic, linoleic, and linolenic acids were noninhibitory to spores of C. botulinum, whereas oxidized samples of all 3 acids caused significant inhibition at 0.01 per cent concentrations.…”

“…This fact suggested that the observed inhibition of C. botulinum may be due to an accumulation of free fatty acids in the cheese during prolonged storage. Fatty acids were reported to inhibit germination of spores of C. botulinum (Humfeld, 1947;Foster and Wynne, 1948); subsequently other authors stated that oxidative rancidity of the fatty acids was the cause of the observed inhibition (Roth and Halvorson, 1952). The amount of free fatty acids formed during aging of cheese varies (Van Slyke and Price, 1952), and factors affecting the rate of fatty acid formation are little known (Babel and Hammer, 1945).…”

A SIMPLIFIED MEDIUM FOR COUNTING CLOSTRIDIUM SPORESab

“…I n a comparative study of media for counting Clostridiuln spores, it was reported by Wynne and Foster ( 5 ) that a modified Yesair's pork infusion agar with added soluble starch yielded the highest counts. Although this medium has been used routinely in our laboratory and elsewhere (2, 4 ) , it is expensive and difficult to prepare. The present investigation concerns a yeast extract medium offered as a possible replacement for the pork infusion and other complex media currently used for counting spores.…”

Observations on the Sporicidal Action of Vegetable Oils Used in Fish Canning

“…Foster & Wynne (1948) reported that some batches of media contain substances that inhibit the germination of anaerobic spores and ascribed it to the presence of unsaturated C,, fatty acids. Halvorson (1950) and Roth & Halvorson (1952) ascribed the inhibitory effects to organic peroxides, the latter authors suggesting that hydrogen peroxide produced temporarily might be the factor involved.…”