1. The phosphate requirement, i.e. the concentration of inorganic orthophosphate that just ceases to be limiting for growth, of Escherichia coli N.C.T.C. 5928 was determined for growth in ammonium-salts media containing glucose or acetate as the carbon and energy source, and compared with that of six other strains of E. coli. 2. The phosphate requirement for E. coli N.C.T.C. 5928 growing on acetate was about ten times that for growth on glucose, but this difference was not observed with any of the other strains. 3. After about 40 generations' growth on acetate with phosphate limitation in a chemostat, the phosphate requirement of the cells gradually decreased until it was equivalent to that of the glucose-grown organism; a single passage through glucose batch culture sufficed to restore the original high phosphate requirement, indicating a permeability phenomenon. 4. The lipid content of E. coli N.C.T.C. 5928 grown on glucose or acetate was measured isotopically by fractionation of cells grown on inorganic [(32)P]orthophosphate and gravimetrically after extraction from the cells by three different methods; change of carbon source from glucose to acetate did not affect the lipid content, which remained constant at 8-9% of the bacterial dry weight.
The effect of vacuum packaging on the microbial spoilage of 'ready-to-use' carrot slices and on the effect on shelf-life of the product is reported. The microbial development on vacuum packaged carrots was slower than that of non-vacuum packaged material. The predominant organisms present were Leuconostoc spp. in the vacuum packs as opposed to Erwinia spp. in the aerobic packs. Vacuum packaging of the sliced carrots significantly extended the shelf-life of the product when stored at 4°C from 5 to 8 days.
The production of ochratoxin A by Aspergillus ochraceus and of ochratoxin A and citrinin by Penicillium viridicatum growing on previously sterilised barley for 200 days at 5,lO and 20°C and a water activity of 0.85 is reported. A . ochraceus did not grow at 5"C, multiplied slowly at 10°C but did not produce toxin. At 20°C the organism multiplied more quickly and produced ochratoxin after 19 days, which slowly disappeared over the next 150 days. P. viridicatum grew slowly at 5°C but did not produce any toxin. It multiplied at 10°C and produced ochratoxin A which was only detectable during the period from 100 to 150 days. At 20°C both ochratoxin A and citrinin were produced. Ochratoxin A was detected after 10 days and was still present after 240 days, whereas citrinin was produced in large quantities between 118 and 129 days and then rapidly disappeared.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.