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S B Primrose

Publications and source records attributed to S B Primrose.

At least 37 records · Page 2Linked to original sources
PubMed1977

The effect of nalidixic acid on the cell cycle of synchronous Rhodopseudomonas palustris cultures.

The influence of the DNA synthesis inhibitor, nalidixic acid, on the properties of synchronous cultures of selected Rhodopseudomonas palustris swarmer cells was examined. There was little alteration in the changes in morphology, extinction, volume distribution and leucine incorporation up to bud development, and photosynthetic membrane lamellae were still synthesized de novo in the bud. However, there was no subsequent division, or flagellum or holdfast synthesis. Instead cells elongated by continued outgrowth of the abortive bud. Since DNA synthesis was also inhibited, this suggested a dependence of cell division, and flagellum and holdfast synthesis, on the completion of chromosome replication. By addition or removal of nalidixic acid at various times in the cell cycle, periods were demonstrated when the organism was insensitive to the antibiotic indicating that there was a pre-synthetic and post-synthetic gap in the pattern of DNA synthesis in R. palustris swarmers.

Cell Division↗
PubMed1977

Evaluation of the role of methional, 2-keto-4-methylthiobutyric acid and peroxidase in ethylene formation by Escherichia coli.

During growth of Escherichia coli strain SPA O in the presence of methionine, an intermediate accumulates in the medium. This intermediate reacts with 2,4-dinitrophenylhydrazine, and can be degraded to ethylene either enzymically or photochemically, the latter being stimulated by the addition of a flavin. The pH optimum for the photochemical degradation of this intermediate and 2-keto-4-methylthiobutyric acid (KMBA) is pH 3 whereas the optimum for methional is pH 6. The enzyme which converts the intermediate to ethylene also converts KMBA to ethylene and has many of the properties of a peroxidase including inhibition by catalase, cyanide, azide and anaerobiosis. The enzyme which synthesizes the intermediate is not known but requires oxygen and pyridoxal phosphate. A pathway for ethylene biosynthesis is proposed in which methionine is converted to KMBA which can be degraded either by peroxidase or in a flavin-mediated photochemical reaction. Its relevance to the properties of other ethylene-producing bacteria and to the proposed pathway of ethylene release by higher plants is discussed.

Aerobiosis↗
PubMed1976

Synchronous growth of Rhodopseudomonas palustris from the swarmer phase.

Rhodopseudomonas palustris was chosen as a model organism for studying bacterial differentiation. Synchronous populations selected by sucrose gradient centrifugation yielded more than 95% swarmer cells. The appearance and disappearance of cell morphological groupings and the doubling of cell numbers in cultures of such swarmer populations were very well defined. Cells were only motile for the first half of the division cycle, but motility was regained before division. Development gave rise to a distinct and characteristic pattern of extinction increase and particle volume distribution. The development of swarmers into mother cells and the dimorphic division of R. palustris are discussed as simple examples of differentiation.

Cell Count↗
PubMed1976

Formation of ethylene by Escherichia coli.

Escherichia coli strain SPA O converts methionine to ethylene by an inducible enzyme system. L-Cysteine, L-homocysteine, methionine derivatives and the sulphur-containing analogues of L-methionine also act as precursors of ethylene. Ethylene is produced by cell suspensions only in the presence of air; cell-free preparations can produce ethylene aerobically and anaerobically, but the extent to which they do so depends on the mode of culture growth. Light stimulates ethylene production by cell suspensions and its presence is essential for production by cell-free preparations. The kinetics of ethylene biogenesis and its pH and temperature optima suggest that ethylene is a secondary metabolite.

Aerobiosis↗