The magnetococcus, a magnetotactic bacterium, has been grown in a complex simulated natural environment. Sufficiently pure samples of cells were obtained magnetically making axenic cultures unnecessary for many purposes. The magnetococcus is a Gram-negative coccus, 1.6 micron in diameter and readily distinguished by highly refractile inclusions and its magnetotactic behavior. This organism is actively motile by means of two bundles of flagella. Electron dense ferromagnetic inclusions were localized between the flagellar bundles. Collections of magnetococci were morphologically homogeneous and negligibly contaminated by extraneous bacteria. DNA extracted from pooled collections of cells was homogeneous by analytical CsC1 centrifugation. The guanine-cytosine content was 61.7%. Total iron by percent cellular dry weight was 3.8%. Comparisons with a previously described magnetotactic marine coccus were made.

Berrah, Ghoulem (Indiana University, Bloomington) and Walter A. Konetzka . Selective and reversible inhibition of the synthesis of bacterial deoxyribonucleic acid by phenethyl alcohol. J. Bacteriol. 83: 738–744. 1962.—The selective inhibitory effects of phenethyl alcohol on gram-negative bacteria were confirmed with a variety of species. At a concentration of 0.25%, phenethyl alcohol was bacteriostatic for gram-negative bacteria; gram-positive cells were unaffected. Pseudomonas fluorescens required higher concentrations of the compound for inhibition than did the other gram-negative bacteria, and the gram-positive, acid-fast mycobacteria resembled the majority of gram-negative bacteria in sensitivity. In the presence of phenethyl alcohol, gram-negative cells formed long filaments. There was no net synthesis of deoxyribonucleic acid (DNA) in such cells, whereas protein and ribonucleic acid (RNA) syntheses were unaffected. Upon removal of phenethyl alcohol, multiplication of the cells immediately ensued, with concomitant DNA synthesis. Yeast extract stimulated both RNA and protein synthesis in phenethyl alcohol-treated Escherichia coli , but no detectable stimulation of DNA synthesis occurred under these conditions.

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 chemotaxis system for Pseudomonas aeruginosa was defined by using the method of Adler. Cells were attracted to compounds in the order ammonium chloride > amino acids > organic acids. Two sugars were assayed and elicited no response. Comparisons with other model systems are discussed.

A variety of bacteria grown on a glucose and salts medium were capable of utilizing orthophosphite as a sole source of phosphorus. Two organisms, Pseudomonas fluorescens 195 and Serratia marcescens 24, were studied in detail. Growth rates and total cell yields of the bacteria grown on phosphite indicated that the bacteria utilized phosphite as efficiently as phosphate. The ability to oxidize the anion was shown to be inducible. A period of adaptation was required prior to growth on phosphite when phosphate-grown cells were transferred to a medium containing a limiting amount of phosphate and excess phosphite. No phosphite-oxidizing activity could be detected in whole cells or cell-free extracts of phosphate-grown cells. Both whole cells and cell-free extracts of phosphite-grown cells possessed phosphite-oxidizing activity.