Aerotaxis in HALOBACTERIUM HALOBIUM

<p>Aerotaxis, previously studied in eubacteria was investigated in the archaebacterium <em>Halobacterium halobium.</em> A quantitative temporal assay for aerotaxis of <em>H. halobium</em> was developed using computer assisted motion analysis. Aerotaxis was most pronounced in early log phase cultures. Peak aerotaxis was found to coincide with peak respiration consistent with a model in which respiration is required for aerotaxis. In a spatial assay a mutant strain lacking the proton motive force (pmf)-generating pigments, bacteriorhodopsin (bR) and halorhodopsin (hR), exhibited enhanced aerotaxis bands relative to the bR⁺hR⁺ parent. The enhanced aerotaxis in the mutant cells was not due solely to an enhanced respiration rate. Aerotaxis in the bR⁺hR⁺ strain was stronger when cells were incubated in the dark than in illuminated cells in which proton motive force was enhanced by the light-activated pigments. These results suggest that in <em>H. halobium</em>, as in eubacteria, aerotaxis is mediated by oxygen-dependent changes in proton motive force. In<em> H. halobium</em> S9P, methionine starvation depleted S-adenosylmethionine (as shown by high performance liquid chromatography) thereby inhibiting protein methylation. Unexpectedly, aerotaxis was abolished by methionine starvation even though unstimulated behavior was unchanged. Using a modified flow assay to measure protein methylesterase activity <em>in vivo</em>, peaks of esterase activity were observed following positive and negative oxygen stimuli and these changes were absent in a protein methyltransferase mutant. The pattern of altered methylesterase activity in <em>H. halobium</em> was most similar to chemostimulus related changes seen in <em>Bacillus </em><em>subtilis. H. halobium</em> thus appears to be the first bacterium in which aerotaxis has been shown to be dependent on receptor methylation.</p>

Name thesis:degree_name

Doctor of Philosophy (Medical Science)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Year

1991

Author dc:creator

• Lindbeck, Jemima Clara

Contributors dc:contributor

• Barry L. Taylor
• Eric A. Goulbourne, Jr.
• Mark S. Johnson
• W. Barton Rippon
• R. Bruce Wilcox

• Biochemistry
• Microbiology
• Halobacterium; Methylation; Transducers; Chemotaxis; Ethionine; Methionine

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/1436

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-2208