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The subcellular distribution of enzymes involved in lipid biosynthesis in E. coli K 1 2 has been studied following various modes of cell disruption and fractionation of the subcellular components. Though most biosynthetic enzymes were found associated with the cytoplasmic membrane fraction regardless of the prockdures of disruption or fractionation employed, the enzymes responsible for the synthesis of the major lipid of E. coli (phosphatidylethanolamine) and of its precursor (phosphatidylserine) had no distinct localization in extracts, These findings are discussed in the context of current models for the assembly of bacterial membranes.Interest in the intracellular localization of phospholipid biosynthetic enzymes in gram negative bacteria has been stimulated by two general observations: 1. The cell envelopes of these organisms are composed of two distinct membranous layers, an inner (cytoplasmic) membrane and an outer membrane which is rich in lipopolysaccharide and localized external t o the cell wall (1 -5). 2. Interrelationships between lipid and membra'ne protein synthesis have been demonstrated for a number of membrane-associated enzyme systems (6-1 7). With respect to the first stated observation, Kennedy, Vagelos, and their associates had shown that most phospholipid biosynthetic activities co-sediment with the cell envelope (1 8-24). This raised the question as to whether the lipids in the inner and outer membranes are synthesized in one or both of these membranes. The solution t o this question became approachable only recently with the advent of techniques for separating the various fractions of the cell envelope. The second stated observation suggests a mechanism which makes newly synthesized lipids accessible t o newly synthesized proteins for their coordinated insertion into membrane. in gram negative bacteria were published during the course of our investigation. Though the three studies are in agreement on most points, the localization of phosphatidylserine synthetase was left unresolved in two of them (25,26), whereas this enzyme was reported to be localized in the ribosomal fraction in the third (27). Our data, however, did not indicate a ribosomal localization for this enzyme, nor were they in total agreement on the localization of yet another enzyme. Since different strains and/or cell disruptionThe results of three studies on the localization of phospholipid biosynthetic enzymes *The preceding paper in this series is Ref. 16. A preliminary report of this work was presented at the 72nd annual meeting of the

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The nutritional requirements of Arizona, Citrobacter, and Providencia are compared, and chemically defined media in which these organisms may be grown are reported. Although certain enteric bacteria, such as Escherichia coli and various species of Salmonella, have been the subjects of countless investigations, little is known about the chemical composition or physiology of other members of the Enterobacteriaceae. In the course of studies on the chemical composition of the paracolons Arizona, Citrobacter, and Providencia, we wished to grow these organisms on defined media. This led us to study the nutritional requirements of Arizona, Citrobacter, and Providencia. The organisms we have studied have been the subjects of a number of investigations by others (4, 5, 8, 10), but in most of these studies bacteria have been grown on semidefined or complex media. Only in the case of the work by Jarvis et al. with Citrobacter (5) were cells grown on a chemically defined medium. Since we wished to standardize growth conditions as much as possible, we investigated the nutritional requirements of Arizona, Citrobacter, and Providencia. Cultures of Arizona, Citrobacter, P. alcalifaciens, and P. stuartil were acquired from a

A collaborative study was conducted to test a method developed to distinguish between adequately and inadequately preserved cosmetic formulations. Nineteen laboratories participated in the study. Samples tested included shampoos, hair conditioners, oil-in-water emulsions, and water-in-oil-emulsions. Triplicate samples of 4 adequately preserved and 4 inadequately preserved cosmetic products were tested by each collaborative laboratory. Results showed that all inadequately preserved shampoo and conditioner samples failed to meet the acceptance criteria for adequately preserved formulations. Of the 51 preserved samples, 49 shampoos and 48 conditioners met the criteria for adequate preservation. All samples of inadequately preserved water-in-oil emulsions and oil-in-water emulsions failed to meet the acceptance criteria, whereas all adequately preserved emulsion formulations met the acceptance criteria.