R Factor Proteins Synthesized in Escherichia coli Minicells: Incorporation Studies with Different R Factors and Detection of Deoxyribonucleic Acid-Binding Proteins

Analysis of the protein synthesized by Escherichia coli minicells containing R factors demonstrated a variety of low- and high-molecular-weight polypeptides in sodium dodecyl sulfate (SDS)-polyacrylamide gels. Only half of this protein was released into a soluble fraction on lysis of these minicells. The other half remained associated with the minicell envelope. The efficiency of precursor incorporation into protein and the kinds of proteins synthesized changed with the age of the minicells at the time of harvest. About 1 to 2% of the soluble R factor-coded protein bound to calf thymus, E. coli, or R factor DNA-cellulose. Although most of these proteins were excluded from Sephadex G-100 columns, they migrated chiefly as low-molecular-weight-polypeptides (13,000 to 15,000) in SDS-polyacrylamide gels. Additional DNA-binding proteins that appeared to be higher-molecular-weight peptides were noted in extracts from younger minicells. At least one protein, identified as an SDS band, appeared to bind selectively to R factor DNA-cellulose. Minicells with R factors also contained DNA-binding proteins of cell origin, including the core RNA polymerase. No such binding proteins were found in R(-) minicells. These studies suggest that: (i) R factors code for proteins that may be involved in their own DNA metabolism; (ii) R factor DNA-binding proteins may be associated with larger host cell DNA-binding proteins or subunits of larger R factor proteins; and (iii) the age of the minicell influences the extent of protein synthesis and the kinds of proteins synthesized by R factors in minicells.     

Studies of Raman Spectra of Water Solutions of Adenosine Tri-, Di-, and Monophosphate and Some Related Compounds

Using a He-Ne CW laser source together with a digital photon counting system, we have obtained well resolved Raman spectra for adenosine mono-, di-, and triphosphate (AMP, ADP, ATP) in aqueous solution. Spectra of these compounds were studied as a function of pH from pH = 0.5 to 13.5 and between 550 and 1700 cm(-1). It was found possible to distinguish spectroscopically between the three phosphates over the pH range studied. A qualitative analysis of vibrational modes responsible for various spectral lines is given. Lines at about 960 and 1100 cm(-1) were found to be good indications of the degree of ionization of the terminal phosphate group.     

Light-dependent hydrogen evolution by Scenedesmus

Summary The effect of glucose and the uncoupler Cl-CCP upon hydrogen production was studied in adapted cells of Scenedesmus obliquus D₃. Cl-CCP at 10^-5M concentration completely inhibited the evolution of H₂ in the dark and increased the apparent rate of H₂ evolution in the light. At 10^-5M Cl-CCP, photosynthesis and photoreduction by anaerobically adapted algae were only temporarily inhibited; O₂ evolution reappeared after approximately 1 hr of illumination if CO₂ was present. Increasing the Cl-CCP concentration to 5 x 10^-5M led to a maximum rate of photohydrogen production and fully inhibited H₂ evolution, photoreduction and dark H₂ evolution. H₂ evolution was accompanied by a release of varying amounts of CO₂ in the light, as well as in the dark. Dark CO₂ production was stimulated by Cl-CCP. H₂ evolution in the light was stimulated by adding glucose to autotrophically grown cells or by growing the cells heterotrophically with glucose; starvation had an opposite effect. Adapted cells released ¹⁴CO₂ from the 3 and/or 4 position of specifically labeled glucose, indicating that degradation occurred via the Embden-Meyerhof pathway. The amount of H₂ released by autotrophically grown cells was the same either with continuous illumination or with short periods of light, followed by darkness. Scenedesmus mutant No. 11, which is unable to evolve O₂ was not inhibited in its capacity to evolve H₂ in the light. These data indicate that the evolution of H₂ in the light by adapted Scenedesmus depends upon the degradation of organic material and does not require the production of free O₂ by photosystem II.The following abbreviations are used: Cl-CCP = carbonyl cyanide m-chlorophenylhydrazone; DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea, DNP = 2,4-dinitrophenol.This work was supported by contract AT-(40-1)-2687 from the U.S. Atomic Energy Commission.     

Sick Absence Certification. Analysis of one Group Practice in 1967

Certificates of inability or fitness to work were issued on 6,161 occasions in one year in one group practice. Half the episodes of illness lasted for seven days or less, and two thirds of the episodes ended on a Sunday. Clearly in most cases the doctor does no more than countersign the patient''s declaration of his fitness or not to work. Abolition of short-term medical certification would probably have little effect on absenteeism or the sums paid out as sick benefit.     

Survival of Shigella in Sewage: II. Effect of Glycerol on Shigella flexneri and Shigella Bacteriophage1

Glycerol (30%) inhibited or delayed the adsorption of Shigella bacteriophage on its host organism, S. flexneri II; glycerol also inhibited or delayed the burst of phage, whether or not adsorption was carried out in the presence of glycerol. Studies of the mechanisms of these effects showed that viscosity and osmotic shock probably were not responsible for either phenomenon. The inhibition of adsorption, however, was proportional to the concentration of glycerol, and appeared to be a function of the hydroxyl groups on the glycerol molecule. The inhibition of burst seemed to be related to the osmotic pressure outside the bacterial cells.     

A diallel cross for mating speeds inDrosophila melanogaster

A diallel cross inDrosophila melanogaster for the mating speeds of previously unmated pairs aged 6 days was carried out for 6 inbred lines and their hybrids. Pairs were observed for 40 minutes.There was extreme hybrid vigour especially in mating frequency for 10 minutes but the degree of hybrid vigour was relatively smaller for 40 minutes.Considerable variability occurred between the inbred lines indicating the genotypic control of mating speed.An analysis of variance on the hybrids revealed significant general and specific combining abilities, and reciprocal effects. The mating frequency for 10 minutes gave heritability in the narrow sense, h²=0.605, 20 minutes gave h²=0.510 and 40 minutes gave h²=0.342.The progressive reduction in h² is due to a decrease in additive genetic variance and an increase in dominance variance with time. Thus either the dominance relations of genes controlling mating speeds change with time. or different loci control this character at different times.