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Escherichia coli cells, infected with bacteriophage M-13 am-5, when plasmolysed by treatment with 2 M sucrose incorporate radioactivity from deoxyribonucleoside triphosphates into phagespecific DNA synthesis by treatment with mitomycin C prior to infection, more that 80% of the incorporated label is found in superhelical replicative form I molecules. If the incorporation is carried out in the presence of bromodeoxyuridine triphosphate, the radioactive label is found in equal amounts in two classes of hybrid replicative form molecules in which either the viral or the complementary strand is labeled. DNA synthesis depends on a functional gene-2 product and shows a specific requirement for ATP and magnesium as divalent cation. Incorporation is inhibited by mitomycin C, nalidixic acid, phenyl ethanol, and sulfhydryl-blocking agents. It is concluded that the observed DNA synthesis occurs by a semi-conservative replication process resembling replicative form replication in vivo. [ABSTRACT FROM AUTHOR]

A 20 fold purification of the gramicidin S synthesizing activity in a 11,000 × g supernatant from Bacillus brevis has been achieved. The purification procedure involves precipitation of undesired material with streptomycin sulphate, followed by precipitation of gramicidin S synthesizing activity at 40% (NH4)2SO4 saturation and fractionation on DEAE-Sephadex. All gramicidin S synthesizing activity appeared in one peak. It incorporated labelled phenylalanine, proline, valine, ornithine and tcucine to the same extent into gramicidin S. The gramicidin S synthesizing activity was found to be stable in a 0.05 M potassium phosphate buffer (pH 7.1) containing glutathione (0.01 M) and glycerol (20%, v/v) for at least 3 days at + 4° and four weeks at -20°. [ABSTRACT FROM AUTHOR]

Various treatments were tested for their capacity to abolish the preferential accumulation of ribonucleic acid in the pelletable-membrane fraction of rel- cells of Escherichia coli starved for amino acids. DNAase in the cold increased the extraction of RNA both in exponentially-growing and in starved cells. The most pronounced increase in DNAase-dependent RNA extraction was observed with ret- cells starved for short periods. Incubation at 37 °C, or a high concentration of ammonium or potassium, abolished completely the preferential accumulation of RNA in the pelletable-membrane fraction of rel- cells starved for 15 min, but left undisturbed considerable amounts of RNA in the membranes of rel- cells which had undergone prolonged starvation (60 min). No preferential accumulation of ribonucleic acid in the membrane fraction of amino acid-deprived cells could be detected when extracts were prepared in the presence of 5 mM magnesium. The sedimentation pattern of the RNA released by several methods was studied. The RNA formed during amino acid starvation of rel- cells was found mainly in polysomes. [ABSTRACT FROM AUTHOR]

1. Crude preparations of nitrogenase (AS1) from Azotobacter chroococcum which were normally oxygen-tolerant, became oxygen-sensitive in the presence of either ATP, GTP, ITP, UTP, CTP or sodium pyrophosphate. MgCl2 antagonised this effect of ATP. 2. ATP-induced oxygen damage was faster at 4 °C than at 30 Deg;C. 3. ATP-induced oxygen damage to prepn AS1 affected fraction 2 (Ac2) of the nitrogenase; fraction 1 (Ac1) was unaffected. Purified fraction Ac2 became hypersensitive to oxygen in the presence of ATP. 4. Pre-treatment of prepn AS1 with "Chelex 100" or EDTA under anaerobic conditions made the nitrogenase oxygen-sensitive. Oxygen-tolerance was partly restored by metal ions. Similar anaerobic pre-treatment of prepn AS1 with ATP followed by removing the ATP by dialysis did not induce oxygen-sensitivity. 5. Pure fraction Ac2 bound significantly more [14C]ATP in the presence of MgCl2 than did EDTA-treated fraction Ac2 in the absence of MgCl2. 6. Hill plots of the ATP requirement for acetylene reduction, for ATP-induced oxygen damage, for the MgCl2 requirement for acetylene reduction and for the MgCl2 requirement for protection against oxygen damage to EDTA-treated prepn AS1 all yielded n values between 1 and 2. 7. These results are discussed in terms of a role for ATP in nitrogen fixation. [ABSTRACT FROM AUTHOR]

A covalent bond between 4-thiouridine in position 8 and cytidine in position 13 can be quantitatively introduced in Escherichia coli tRNAfMet by irradiation at 335 nm. The cross-linked tRNAfMet can be acylated and formylated like the unmodified molecule though the rate of acylation is lower. It is bound normally to 70-S ribosomes by crude initiation factors in the presences of pAUG or T4 mRNA, and can transfer N-formyl-methionine to puromycin. Thus, the initiation process does not require any separation of the 4-thiouridine and cytidine residues. [ABSTRACT FROM AUTHOR]

The determination of the 2-keto-3-deoxyoctonic acid (KDO) content of a lipopolysaccharide obtained from Escherichia coli ATCC 12408 using the thiobarbituric acid and semicarbazide methods for its estimation points to the presence of a KDO trisaccharide unit in the structure. On partial hydrolysis of the lipopolysaccharide by the method of Painter, using polystyrene sulphonic acid, up to 60% of the KDO was lost. A core oligosaccharide, with a molecular weight in the region of 3500 to 5000 and containing heptose, glucose, galactose, KDO and phosphorus in the molar ratio of 2:1.44:0.6:0.3:1.3, was isolated on fractionation of the dialysate on Sephadex G-15. Sodium borohydride reduction of the oligosaccharide results in the loss of both reducing power and KDO, indicating a linear-type structure with KDO only at the reducing end. Removal of phosphate from the oligosaccharide had no significant effect on its molecular weight. Periodate oxidation, followed by borohydride reduction, and methylation studies showed the presence of certain structural features similar to those already found for the core region of lipopolysaccharides from other gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Initiation factor activities for natural messenger RNA translation are markedly reduced in extracts from stationary phase Escherichia coli. as compared to growing cells. Immunological techniques demonstrate that the amount of initiation protein IF3 is actually decreased in nongrowing cells. These changes result in a modified mRNA specificity in the stationary celt extracts. [ABSTRACT FROM AUTHOR]

1. The effects of cycloheximide and chloramphenicol on the development of complex oxidase systems and of several parts of the respiratory chain of yeast mitochondria have been investigated. 2. In repressed cells addition of cycloheximide has a stronger effect on the development of several mitochondrial activities than has the addition of chloramphenicol. Probably in this phase the derepression is primarily dependent on the synthesis of enzymic proteins on the cytoplasmic ribosomes. 3. Incubation of partially derepressed cultures with chloramphenicol results in an inactivation of cytochrome oxidase and of the succinate and NADH oxidase systems and in a decrease in the respiratory control. After a lag the development of succinate and NADH dehydrogenase and of NADH-cytochrome c oxidoreductase is severely inhibited. 4. There are some remarkable parallels between the effects of incubation of the cells with chloramphenicol and treatment of the mitochondrial fractions with digitonin. This suggests that chloramphenicol may indirectly interfere with the structure or composition of mitochondrial membranes. 5. The inhibition of the mitochondrial protein synthesis may affect mitochondrial membranes and interfere with some of the functions of the integrated oxidase systems. The inactivation of these systems suggests that their development and stability is dependent on a continual supply of some products of the mitochondrial protein-synthesizing system. [ABSTRACT FROM AUTHOR]

Two strains of hydrogen-oxidizing bacteria were used: Hydrogenomonas eutropha strain H16 and strain 11/x. The former is a gram-negative flagellated rod and has been relatively well known with respect to its morphological, physiological, and biochemical properties. The latter is a gram positive, non spore-forming, motile small rod the definite classification of which is unknown as yet. Both strains were grown chemolithotrophically in submerged culture with a limited nitrogen source and supplied with a gas mixture of H2 02, and CO2. The lipid composition of the bacteria was determined at the end of the exponential phase (I), at the storage phase (II), and after reutilization of storage material (III). Along with the accumulation of poly(3-hydroxybutyric acid) as the major storage material in strain H16 the amount of other lipids was shown to increase 1.8-fold at phase II and to decrease at phase III. There is little or no change in the lipid pattern in various growth phases. It is suggested that the 1.8.fold increase of the latter lipids during phase II is due to the synthesis of membrane lipids that are required for the formation of membranes surrounding the intra cellular granules of accumulating poly(3-hydroxybutyric acid). In strain II/x the amount of lipids increases 7 times along with an equal increase of carbohydrates at phase II. The majority of accumulated lipids consists of triglycerides free of significant amounts of unusual acyl group. It is suggested that there is a true storage of triglycerides that are reutilized during phase III. The lipid pattern of strain H16 is characterized by a high proportion of "strongly bound lipids" that consist predominantly of phospholipids. Characteristic lipid components are phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol, while coenzyme Q8 (0.41 μmol/g bacterial dry weight) has been found among the neutral lipids. A C17 cyclopropane acid (probably cis-9,10-methylene hexadecanoic acid) is present in all saponifiable lipids. The lipid pattern of strain 11/x is characterized by a high proportion of "loosely bound lipids" that consist predominantly of neutral lipids, particularly of triglycerides. Among the polar lipids, diphosphatidylglycerol and phosphoinositides are most abundant, and several unknown phospholipids are also present. No cyclopropane fatty acid has been found. The possible use of strain 11/x as a source of nutritional fat is discussed. [ABSTRACT FROM AUTHOR]

A covalent bond between 4-thiouridine in position 8 and cytidine in position 13 can be quantitatively introduced in Escherichia coli tRNAfMet by irradiation at 335 nm. The cross-linked tRNAfMet can be acylated and formylated like the unmodified molecule though the rate of acylation is lower. It is bound normally to 70-S ribosomes by crude initiation factors in the presences of pAUG or T4 mRNA, and can transfer N-formyl-methionine to puromycin. Thus, the initiation process does not require any separation of the 4-thiouridine and cytidine residues. [ABSTRACT FROM AUTHOR]

The article focuses on the issues concerning the application of molecular phenotypes to the evaluation of taxonomic affinities. It states that modern taxonomic evaluations are based on a priori premise that the length of active migration of protein molecules is more valuable in assessing taxonomic affinities than the length of nasal bones. In connection, the author notes that the extent of interindividual and geographic variation of phenotypes should be assessed before intertaxa evaluations can be significant.