Treick , R. W. (Indiana University, Bloomington), and W. A. Konetzka . Physiological state of Escherichia coli and the inhibition of deoxyribonucleic acid synthesis by phenethyl alcohol. J. Bacteriol. 88: 1580–1584. 1964.—The effects of concentration of phenethyl alcohol (PEA) and the physiological state of the cells on inhibition of macromolecular synthesis in Escherichia coli were investigated. Deoxyribonucleic acid (DNA) synthesis by cells of E. coli from the maximum stationary phase is completely inhibited by 0.32% (v/v) PEA immediately upon addition of the inhibitor, although there is a net increase in the synthesis of ribonucleic acid (RNA) and protein. However, DNA synthesis in cells from the exponential phase is inhibited only after an increase which corresponds to 1.4 to 1.6 times the amount of DNA present at the time of PEA addition. In a randomly dividing culture, this increment of DNA synthesis presumably represents completion of the DNA replication cycle initiated at the time of PEA addition. By programming the addition and removal of PEA, DNA synthesis can be made to proceed in stepwise increments corresponding to doublings of the DNA. The data indicate that the DNA being replicated at the time of PEA addition completes the replication cycle and, although there is net synthesis of RNA and protein, no initiation of a second cycle of DNA replication occurs until the removal of the inhibitor.

A detailed characterization of the lysine biosynthetic pathway in plants is yet to be completed. It is, however, assumed that the diaminopimelic acid pathway exists in the plant kingdom, as commonly described forEscherichia coli.Modification and refinement of lytic complementation, a technique previously utilized in bacterial systems, facilitated the isolation of a functional Diaminopimelate Dehydrogenase gene from aGlycine max nuclear gene library. The isolated gene codes for the enzyme meso-diaminopimelate dehydrogenase. The coding capacity for the enzyme was originally contained on a 6.6kb fragment in a Charon 4a soybean gene bank. Subcloning of the 6.6kb fragment resulted in the recombinant plasmid pMW75. Subsequent subcloning resulted in a 4.05 kb fragment contained in pLW14. One region of homology was observed upon hybridization to EcoR1 digested soybean DNA. Homologous sequences were also observed in Triticum DNA.Meso-diaminopimelate dehydrogenase activity was demonstrated inGlycine max embryos. Maximum enzymatic activity of the cloned enzyme was observed at a pH of 8.0. The enzyme encoded by the soybean gene has an apparent molecular weight of 67 000.

The earliest report of the cultivation in vitro of pathogenic leptospires is that of Inada et al. (1916). From 1916 until the present, various media, both liquid and semisolid, have been developed and used for research and diagnostic purposes. Examples of such media are those of Korthof (1932), Chang (1947), Stuart (1946), and Cox (1955). A common denominator for growth of leptospires which is present in all of the media is some type of body fluid such as serum, whole blood, or ascites fluid. The literature contains few reports on the suc

Plants of Mimulus cardinalis Douglas (Scrophulariaceae) were grown in axenic culture from seed for 28 days on a minimal salts medium supple-mented with L-lysine, L-methionine, L-threonine, L-isoleucine, DL-or L-homoserine or DL-homocysteine, alone or in combinations ranging from 5 to 1000 μM. Abnormal growth was observed at the higher concentrations of all these aminoacidsexcept homocysteine. The lysine inhibition was significantly reduced by methionine, homocysteine or isoleucine. The threonine inhibition was significantly reduced by methionine or homocysteine. A combination of lysine and threonine at 1 MM was lethal. This synergistic effect was prevented when methionine, homoserine or homocysteine were added to the lysine-threonine combination. These results can be explained in terms of end-product control of aspartokinase and homoserine dehydrogenase by lysine and threonine, respectively, in the biosynthetic pathway to these aspartic-acid-derived amino acids.

A modification of the Colowick and Womack procedure for measuring ligand binding by macromolecules is described for drug binding by bacteria. This technique is based on the determination of drug concentration in the dialysate from a bacteria-drug mixture at equilibrium. The dialysis cell of the original procedure was replaced by a Minibeaker (Bio-Rad), which has a larger membrane surface area, and the dialysate was continuously monitored with a spectrophotometer equipped with a flow cell. With this system, only 3 min was required to determine the amount of cetylpyridinium chloride bound by Escherichia coli K-12 strain P678. Possible applications of the technique are discussed.