Effect of Nitrofurans and Chlortetracycline on Microorganisms Associated with Shrimp

Nitrofuran AF-2 displayed greater inhibitory effect than did nitrofuran Z when a mixed bacterial culture, including several proteolytic bacteria, isolated from shrimp was subjected to these compounds in vitro. Nitrofuran Z exhibited greater bactericidal properties than did chlortetracycline in all cultures used. Only 10 mug of nitrofuran AF-2 per ml was sufficient to inhibit the growth of mixed bacteria in nutrient broth, whereas 50 mug of nitrofuran Z per ml was necessary to accomplish the same inhibition. A 50-mug amount of chlortetracycline per ml displayed about the same inhibitory effect as either 10 mug of AF-2 per ml or 20 mug of Z per ml. The isolated proteolytic bacteria showed greater suppression of growth when subjected to AF-2 than when subjected to Z; however, both nitrofurans were effective in preventing growth. The addition of either 1 mug of AF-2 per ml or 5 mug of Z per ml to nutrient broth inhibited the growth of Achromobacter aquarmarinus, whereas chlortetracycline was less effective, requiring about 20 mug to suppress growth to the same degree.     

Amino Acid Transport in Pseudomonas aeruginosa

Properties of the transport systems for amino acids in Pseudomonas aeruginosa were investigated. Exogenous (14)C-labeled amino acids were shown to equilibrate with the internal native amino acid pool prior to incorporation into protein. When added at low external concentrations, the majority of the amino acids examined entered the protein of the cell unaltered. The rates of amino acid transport, established at low concentrations with 18 commonly occurring amino acids, varied as much as 40-fold. The transport process became saturated at high external amino acid concentrations, was temperature-sensitive, and was inhibited by sodium azide and iodoacetamide. Intracellular to extracellular amino acid ratios of 100- to 300-fold were maintained during exponential growth of the population in a glucose minimal medium. When the medium became depleted of glucose, neither extracellular nor intracellular amino acids could be detected.     

Amino Acid Pool Formation in Pseudomonas aeruginosa

The accumulation and behavior of various amino acids in the pool of Pseudomonas aeruginosa (ATCC 9027) were investigated. Patterns of pool formation and maintenance varied with different amino acids tested and were dependent, to a considerable extent, upon the ability of the organism to catabolize the particular amino acid. The establishment of steady-state amino acid pool levels depended upon the activity of the amino acid permease involved and upon the rate of protein synthesis. The presence of a relatively large specific amino acid pool did not affect the formation of a pool of a structurally different amino acid, and a preformed steady-state pool was not displaced by structurally unrelated amino acids. Steady-state amino acid pools decreased rapidly in the presence of inhibitors of energy metabolism and at 0 C. Steady-state internal amino acid pools were found to be in equilibrium with the corresponding external amino acid, present at low levels. A multiplicity of proline pools was demonstrated.     

Hemagglutinating Property of Haemophilus aegyptius

Extracts possessing the capacity to hemagglutinate normal human erythrocytes were recovered from Haemophilus aegyptius by treatment with either diethylene glycol or acetone. Antisera prepared against these extracts or the unextracted bacterial cell inhibited hemagglutination by homologous and heterologous antigens. Microgel diffusions indicated the presence of identical components in each extract as expressed by lines of identity between antisera to each fraction. The hemagglutinin was identified as a lipopolysaccharide, 42% lipid and 57% carbohydrate. The determination of 6% phosphorus in the lipid fraction identified it as containing phospholipid.     

Phenylketonuria—Experience at One Center in the First Year of Screening in California

One year''s experience with phenylketonuria during the calendar year 1966, the first year for compulsory newborn screening in California, was reviewed. The over-all prevalence rate from reported cases in California during this period was one case per 19,500 persons tested. Fifty-seven persons suspected of having pku were evaluated, and 25 of them were determined to be phenylketonuric. Eleven of the 25 were infants in whom the abnormality was detected through the newborn screening program or because it was detected in a sibling through a screening program. All the newborn phenylketonuric patients were developing normally at the time of last report (although the follow-up periods were short).In nine of the other children, pku was detected because they were retarded. Five retarded children who were diagnosed as phenylketonuric at another clinic were given dietary assistance.Five additional infants had elevated serum phenylalanines but did not have the classic biochemical findings of pku and are being evaluated further. Nine infants with positive screening tests exhibited biochemical and clinical findings consistent with transient tyrosinemia. Eighteen other children were evaluated and found to have no metabolic abnormality.The newborn screening program for pku is of decided benefit in early identification of a group of infants who have a high rate of potentially serious metabolic disease. Early identification permits treatment soon enough to prevent mental retardation. Newly identified patients should be evaluated in a medical setting capable of careful pediatric, biochemical and nutritional surveillance.     

Changes in the Microflora of Irradiated Petrale Sole (Eopsetta jordani) Fillets Stored Aerobically at 0.5 C

The microfloral changes on irradiated petrale sole fillets during aerobic (packaged with oxygen-permeable film), refrigerated storage were determined by the identification of bacterial and yeast isolates to the generic level. The samples were irradiated at 0.0, 0.1, 0.15, 0.2, 0.3, and 0.4 Mrad by use of a cobalt-60 gamma source, were stored at 0.5 C, and were examined periodically for spoilage, total microbial population, and composition. The preirradiation flora of the fresh fillets consisted of coryneforms, Achromobacter, Micrococcus, Flavobacterium, Pseudomonas, and Lactobacillus. Immediately after irradiation, Micrococcus, Achromobacter, coryneforms, and Bacillus were predominant. The flora of the nonirradiated fillets at the time of spoilage consisted of Pseudomonas and Achromobacter. The flora of the irradiated fillets at the time of spoilage consisted of Achromobacter and Trichosporon.     

A Comparison of the Native and Derived 30S and 50S Ribosomes of Escherichia coli

Four types of ribosomes occurring in E. coli have been separated by sucrose gradient centrifugation. These are the 30S and 50S particles occurring in E. coli extracts (native particles), and the 30S and 50S particles which are the subunits of 70S ribosomes (derived particles). Two criteria were used in comparing these particles: (1) The type of RNA contained in each, as determined by sedimentation velocity in the analytical ultracentrifuge. (2) The ability of mixtures of 30S and 50S ribosomes (derived 30S + derived 50S, native 30S + native 50S) to undergo the reaction: [Formula: see text] Native and derived 30S particles were found to contain 16S RNA. Derived 50S particles contained 23S RNA and a small amount of 15 to 20S RNA, whereas native 50S ribosomes contained only 16S RNA. Derived 30S and 50S particles combined to form 70S particles. However, under identical conditions, native 30S and 50S particles did not form 70S ribosomes.     

THE FINE STRUCTURE OF STREPTOMYCES VIOLACEORUBER (S. COELICOLOR) : III. The Walls of the Mycelium and Spores

A study of thin sections of hyphae of Streptomyces violaceoruber in the electron microscope showed that the structure of the walls and the mode of formation of cross-walls are similar to those of Gram-positive bacteria. A beaded structure was seen in some regions of the wall, and the significance of this observation is discussed in relation to previous studies of the fine structure of bacterial cell walls. Elements of the intracytoplasmic membrane system appear to be involved in the process of cross-wall formation. The walls of the hyphae of the aerial mycelium divide into two layers before the spores are formed, and only the inner component of the wall grows inwards to form the cross-walls and so delimit the spores. The outer component remains intact for a time and acts as a sheath around the developing spores. Finally the sheath breaks and the spores are liberated. This process is contrasted with the formation of endospores in eubacteria. When the spores germinate, the walls of the germ tubes are continuous with those of the spores.