Two outer membrane proteins (OMPs)designated OmpH and OmpL undergo inverse regulation in abundanceas a function of hydrostatic pressure.OmpH is present in high amounts at 28 MPa while OmpL dominates at 0.1 MPa.Both OMPs appear to be nonspecific channel proteins (porins),but OmpH provides for the uptake of larger peptides,a feature which could be important under the low nutrient conditions prevalent in the deep sea.Although neither ompl/nor ompl mutants are impaired in piezophilic growth,some regulatory mutants affecting omp expression in SS9 do influence growth at high pressure. The regulation of OmpH and OmpL is controlled at the transcriptional level by amembrane-localized transcription factor possessing homology to the ToxR regulatory protein from the related species Vibrio cholerae,which functions with an associated protein designated ToxS.As in SS9,V.cholerae ToxR controls the inverse regulation of two omp genes,but unlike SS9 V.cholerae ToxR does not respond to pressure.Thus,the SS9 ToxR protein,which is 50%identical to the V.cholerae homologue,has evolved novel pressure-sensitive properties.The location and structure of ToxR would seem to make it well suited to function as a piezometer for a cell.Membrane fluidity and phase is highly pressure-sensitive and membrane fluidizing treatments can counteract SS9 ToxR high pressure signaling.Another possible site of pressure influence on ToxR is between the interface of its subunits,as well as between ToxR and ToxS.V.cholerae ToxR/S is multimeric and many protein multimers dissociate under moderately high pressure conditions. Slides associated with this lecture: 1.The tree of life has three domains.These are the Bacteria,Archaea and the Eukarya.This basic division of all of life is based on extensive analyses of genes and genomes by evolutionary biologists.In this course we will mostly focus on the members of the Bacteria and Archaea domains. 2.The high pressure portions of the biosphere includes the deep sea and the deep earth,although little is known about deep subsurface life. 3.Introductory slide for deep-sea microbiology. 4.When you examine the bathymetry of our ocean planet you can learn that the average depth of the oceans is 3.8 km.Most of the ocean is within the deep sea. 5.All kinds of interesting organisms exist within the deeper regions of our oceans,such as this blob fish. 66 Two outer membrane proteins (OMPs) designated OmpH and OmpL undergo inverse regulation in abundanceas a function of hydrostatic pressure. OmpH is present in high amounts at 28 MPa while OmpL dominates at 0.1 MPa. Both OMPs appear to be nonspecific channel proteins (porins), but OmpH provides for the uptake of larger peptides, a feature which could be important under the low nutrient conditions prevalent in the deep sea. Although neither ompH nor ompL mutants are impaired in piezophilic growth, some regulatory mutants affecting omp expression in SS9 do influence growth at high pressure. The regulation of OmpH and OmpL is controlled at the transcriptional level by amembrane-localized transcription factor possessing homology to the ToxR regulatory protein from the related species Vibrio cholerae, which functions with an associated protein designated ToxS. As in SS9, V. cholerae ToxR controls the inverse regulation of two omp genes, but unlike SS9 V. cholerae ToxR does not respond to pressure. Thus, the SS9 ToxR protein, which is 50% identical to the V. cholerae homologue, has evolved novel pressure-sensitive properties. The location and structure of ToxR would seem to make it well suited to function as a piezometer for a cell. Membrane fluidity and phase is highly pressure-sensitive and membrane fluidizing treatments can counteract SS9 ToxR high pressure signaling. Another possible site of pressure influence on ToxR is between the interface of its subunits, as well as between ToxR and ToxS. V. cholerae ToxR/S is multimeric and many protein multimers dissociate under moderately high pressure conditions. Slides associated with this lecture: 1. The tree of life has three domains. These are the Bacteria, Archaea and the Eukarya. This basic division of all of life is based on extensive analyses of genes and genomes by evolutionary biologists. In this course we will mostly focus on the members of the Bacteria and Archaea domains. 2. The high pressure portions of the biosphere includes the deep sea and the deep earth, although little is known about deep subsurface life. 3. Introductory slide for deep-sea microbiology. 4. When you examine the bathymetry of our ocean planet you can learn that the average depth of the oceans is 3.8 km. Most of the ocean is within the deep sea. 5. All kinds of interesting organisms exist within the deeper regions of our oceans, such as this blob fish