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Biomedical subjects

R N Doetsch

Publications and source records attributed to R N Doetsch.

7 recordsLinked to original sources
PubMed1978

'Viscotaxis', a new behavioural response of Leptospira interrogans (biflexa) strain B16.

When in a non-viscous environment and confronted with a viscous one, Leptospira interrogans (biflexa) strain B16 preferentially selected the latter. We have designated this positive response to a viscosity gradient as 'viscotaxis'. Using an originally designed experimental chamber, a pool of leptospires were faced with capillary tubes containing either polyvinylpyrrolidone (PVP) or N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES). Leptospires suspended in HEPES responded positively to 2% (w/v) PVP in capillaries, and migrated into them in large numbers in 1 h. No response was observed when the chamber and capillary tubes contained solutions of the same viscosity. As the viscosity of PVP was increased, a proportionally larger number of leptospires migrated into it. This newly observed aspect of leptospiral behaviour may have ecological significance.

Culture Media↗
PubMed1977

Temperature effects on bacterial movement.

Details are presented for the construction of a simple precision temperature-controlled chamber for investigating bacterial motile behavior. Independent of original incubation temperature, all species of motile bacteria observed showed a five- to sevenfold increase in average translational velocity (micrometers per second) as the environment temperature was incremented over the range from 10 to 50 degrees C. Temperature jumps downward produced transient tumbling or reciprocal behavior responses, depending on the mode of flagellar distribution, in all species examined. Upward temperature jumps induced accelerated velocities without tumbling or reversal. A partial capacity adaptation to temperature was noted, in that the greatest average translational velocity at any given observation temperature occurred when the organisms were grown at temperatures less than the optimum.

Adaptation, Biological↗
PubMed1976

The effects of alkalinity and hypertonicity on the morphology and motility of Leptospira interrogans (biflexa) strain B16.

Effects of alkalinity and hypertonicity on the motile behaviour of Leptospira interrogans (biflexa) B16 were observed, quantified, and compared with effects previously shown by similar factors on the motility of eubacteria. Leptospira interrogans tolerated relatively high concentrations of hydroxide ions. Motility similar to that in controls was observed at pH values up to 9-8; but at pH 10-0 motility declined sharply with time of exposure, and there was structural alteration, visible as a blebbing of the cell envelope. Unlike the behaviour of eubacteria, immobilization of L. interrogans induced by hydroxide ions could not be reversed by lowering the pH. It is suggested that by restricting entry of hydroxide ions, the cell envelope protects its motility apparatus from adverse effects. Leptospira interrogans was completely immobilized in 0-5 M and 1-0 M-sucrose solutions. Unlike the eubacteria, leptospires were incapable of spontaneous reversion to motile forms and resumption of motility was dependent on both concentration and time of exposure to sucrose. Deuterium oxide did not affect movement, suggesting that even though leptospire endoflagella and the exoflagella of eubacteria are analogous, the motile behaviour of L. interrogans is significantly different from that of eubacteria.

Culture Media↗