No abstract

We investigated the effect of time, temperature, and the presence of sodium chloride, nitrates, and nitrites in the medium on the growth and production of enterotoxin B by Staphylococcus aureus. Assays by the double gel-diffusion method showed that m enterotoxin B production occurs at the beginning of the stationary phase of growth. Lowering the tanperature of incubation decreased the amount of toxin produced without affecting the total amount of growth. Increases in concentration of curing salts reduced toxin production more rapidly than cell growth. The relationship of these observations to food-poisoning outbreaks is briefly discussed.

Diminuition of the fat reserve and concomitant increase of carbohydrate during germination of oil seeds have been well established (3, 7, 10, 11, 12, 13,16). Few studies, however, have compared illuminated and unilluminated seedlings, or have controlled the environmental conditions to the degree necessary for calculation of a rate constant and for prediction of fat content at various stages of growth. MacLachlan (9) found a greater utilization of fat during soybean germination in the light than in the dark. He concluded that there was no preferential utilization of unsatuirated fatty acids, because no change was observed in the average unsaturation of the fatty acids in the cotyledons. But Holman (6), also using soybeans , reported a decrease in the iodine value of the fat reserve and a preferential utilization of linoleic and linolenic acid. Crombie and Comber (2) found that during the germination of seeds of the watermelon (Citruillus vulgaris) all the major fatty acids, except oleic, disappeared at rates proportional to the quantities present in the seed fat. Oleic acid was metabolized relativelv faster than the other fatty acids. A better understanding of the relations of fats to general metabolism may be expectedI to result from quantitative physiological and chemical studies of germinating fatty seeds. The extent to which reserve fats and current photosynthate contribute to the material and energy requirements for seedling growth represents one aspect of the broad problem. There is also a need for more analytical data on the changes that occur in the fatty acid composition of the glycerides as the fat reserve is utilized. The experiments reported in this paper were un-dertaken to study the rate of utilization and the composition of the fat reserve during cotton seed germination under various growth condlitions. To correlate the decrease in fat content with the growth of the seedlings, measurements were made of the development of the root, hypoeotyl, and cotyledon. MIATERIALS AND METHODS Cotton seeds of the 1953 crop (Gossypium hirsu-tum L., var. Fox, kindly supplied by the Delta and Pine Land Co. of Scott, M\iss.) were reduced in moisture to 6 % by drying with calcium oxide and then stored in sealed metal containers at 10 C (18). Small lots of seed were delinted in sulfuric acid for three minutes, rinsed thoroughly, soaked for 30 minutes in distilled water, and then allowed to germinate in the dark at 30 ± 10 C on wet filter paper. After 22 hours the seedlings with roots 7 to 12 mm long were supported on a layer of bobbinet (cloth netting with hexagonal mesh 3 by 3 mm) stretched over a glass rod frame provided with 4-cm legs. The frame was placed in a Pyrex dish which was filled to the level of the bobbinet with a culture solution having the following composition: 0.0040 M Ca (NO3)2 .4 H,0, 0.0030 M KNO3, 0.0016 M MgSO4 7 H20, 0.0012 I KH2PO4, 0.0005 M (NH4)2SO4, 0.00004 I FeCl2 4 H20, 0.00002 M K3C;H507 HaO (potas-sium citrate), and the following amounts in parts per million, of the microtrophic elements:...

SUMMARY The lipolytic activity at ‐7, ‐18, and ‐29°C of strains of Pseudomonas fragi, Staphylococcus aureus, Geotrichum candidum, Candida lipolytica, Penicillium roqueforti, and an unidentified Penicillium sp. in emulsions of corn oil, coconut oil, and lard was determined. The action was measured by titratable acidity and by quantitative determination of the fatty acids by chromatography. The lipases from these microorganisms showed considerable activity within 2‐4 days at ‐7°C and within a week at ‐18°C. Activity at ‐29°C was evident within 3 weeks by some of the cultures, particularly on corn oil. The rate of lipolysis in frozen substrates was directly related to their degree of unsaturation. However, there also were differences among genera. The lipase of G. candidum had considerably more specificity for oleic and linoleic acids than any of the others. P. fragi and C. lipolytica were least able to attack the β‐esterified palmitic acid of lard. The ability of S. aureus to attack this position readily at 35° C was nullified by lowering the temperature to –18° C. A similar effect was observed on the mold lipase.