Genetics of pressure-sensing and
adaptation in a deep-sea bacterium
Doug Bartlett, Ph.D.
Scripps Institution of Oceanography
University of California, San Diego
Friday, October 16, 1998
12:00 NoonPacific Forum
Piezophiles (also referred to as barophiles) are micro-organisms whose optimal pressure
for growth and reproduction are above one atmosphere. Unlike many
cultured piezophiles are closely related to well studied marine bacteria, a fact which has
helped make it possible to apply genetic tools to the study of one of their members.
The psychrotolerant, moderately piezophilic deep-sea bacterium Photobacterium
profundum SS9 has been the subject of genetic manipulation of processes associated
with both pressure-sensing and high-pressure and/or low-temperature adaptation. SS9
responds to changes in pressure by a) inversely altering the expression of two outer
membrane protein encoding genes and b) by changing its fatty acid composition.
Piezoregulation of the omp gene depends on the activity of a membrane localized protein
bearing homology to the ToxR family of transcription factors. Pressure/temperature effects
on SS9 ToxR abundance and activity help explain the function of this protein in
piezoregulation. The results of experiments using membrane-perturbing local anesthetics
are consistent with a role for changes in membrane structure (fluidity) in
ToxR-dependent piezosignaling. Membrane structure is also critical to
characteristics of piezosensitive mutants impaired in mono- or poly-unsaturated fatty acid
synthesis will be described.
Finally, additional genetic experiments which have led to the identification of a DNA
recombination protein which also greatly influences cell growth at high pressure will be
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Last updated: December 19, 2000