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Studies in the Phototaxis of Rhodospirillum rubrum


Clayton, Roderick Keener (1951) Studies in the Phototaxis of Rhodospirillum rubrum. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8ESJ-0H23.


The bacterium Rhodospirillurn rubrum is capable of a photosynthetic reduction of CO2 similar to plant photo­ synthesis. A decrease in the illumination of R. rubrum induces it to reverse its direction of swimming; an investigation of the probability of this phototactic response as a function of the parameters of the stimulus, such as the intensity of illumination and its time pattern, should enhance our understanding of biological irritability.

The present investigation is preliminary to such an undertaking. It was attempted to learn more about the responding system through studies of the interaction between the pigments, phototaxis, and metabolism of R. rubrum. A determination was made of the relative spectral effectiveness of light in promoting a phototactic response; this measurement provided evidence that in addition to bacteriochlorophyll the predominant carotenoid pigment of rubrum absorbs phototactically active light. It has been suggested that the tactic response of R. rubrum is associated directly with a decrease in its metabolic rate; studies of the tactic response to oxygen yielded evidence that this hypothesis must be abandoned.

The remarkable adherence to the Weber Law reportedly displayed in the phototaxis of R. rubrum was reinvesti­gated; an adherence over a much smaller range of intensities was observed than had been reported earlier. The masking, under certain conditions of a potentially close Weber Law adherence was discussed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Physics and Biophysics)
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Minor Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Delbruck, Max
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1951
Funding AgencyGrant Number
Atomic Energy CommissionUNSPECIFIED
Record Number:CaltechTHESIS:09072017-090341123
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10417
Deposited By: Benjamin Perez
Deposited On:07 Sep 2017 19:43
Last Modified:25 Apr 2023 22:51

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