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The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP... The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1 Gargi Kulkarni a , b , Chia-Hung Wu a and Dianne K. Newman a , b , c Division of Biology, California Institute of Technology, Pasadena, California, USA a Howard Hughes Medical Institute, Pasadena, California, USA b Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA c ABSTRACT Lipid molecules preserved in sedimentary rocks facilitate the reconstruction of events that have shaped the evolution of the Earth's biosphere. A key limitation for the interpretation of many of these molecular fossils is that their biological roles are still poorly understood. Here, we use Rhodopseudomonas palustris TIE-1 to identify factors that induce biosynthesis of 2-methyl hopanoids (2-MeBHPs), progenitors of 2-methyl hopanes, one of the most abundant biomarkers in the rock record. This is the first dissection of the regulation of hpnP , the gene encoding the C-2 hopanoid methylase, at the molecular level. We demonstrate that EcfG, the general stress response factor of alphaproteobacteria, regulates expression of hpnP under a variety of challenges, including high temperature, pH stress, and presence of nonionic osmolytes. Although higher hpnP transcription levels did not always result in higher amounts of total methylated hopanoids, the fraction of a particular kind of hopanoid, 2-methyl bacteriohopanetetrol, was consistently higher in the presence of most stressors in the wild type, but not in the Δ ecfG mutant, supporting a beneficial role for 2-MeBHPs in stress tolerance. The Δ hpnP mutant, however, did not exhibit a growth defect under the stress conditions tested except in acidic medium. This indicates that the inability to make 2-MeBHPs under most of these conditions can readily be compensated. Although stress is necessary to regulate 2-MeBHP production, the specific conditions under which 2-MeBHP biosynthesis is essential remain to be determined. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Bacteriology American Society For Microbiology

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1

Journal of Bacteriology , Volume 195 (11): 2490 – Jun 1, 2013

Abstract

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1 Gargi Kulkarni a , b , Chia-Hung Wu a and Dianne K. Newman a , b , c Division of Biology, California Institute of Technology, Pasadena, California, USA a Howard Hughes Medical Institute, Pasadena, California, USA b Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA c ABSTRACT Lipid molecules preserved in sedimentary rocks facilitate the reconstruction of events that have shaped the evolution of the Earth's biosphere. A key limitation for the interpretation of many of these molecular fossils is that their biological roles are still poorly understood. Here, we use Rhodopseudomonas palustris TIE-1 to identify factors that induce biosynthesis of 2-methyl hopanoids (2-MeBHPs), progenitors of 2-methyl hopanes, one of the most abundant biomarkers in the rock record. This is the first dissection of the regulation of hpnP , the gene encoding the C-2 hopanoid methylase, at the molecular level. We demonstrate that EcfG, the general stress response factor of alphaproteobacteria, regulates expression of hpnP under a variety of challenges, including high temperature, pH stress, and presence of nonionic osmolytes. Although higher hpnP transcription levels did not always result in higher amounts of total methylated hopanoids, the fraction of a particular kind of hopanoid, 2-methyl bacteriohopanetetrol, was consistently higher in the presence of most stressors in the wild type, but not in the Δ ecfG mutant, supporting a beneficial role for 2-MeBHPs in stress tolerance. The Δ hpnP mutant, however, did not exhibit a growth defect under the stress conditions tested except in acidic medium. This indicates that the inability to make 2-MeBHPs under most of these conditions can readily be compensated. Although stress is necessary to regulate 2-MeBHP production, the specific conditions under which 2-MeBHP biosynthesis is essential remain to be determined.

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Publisher
American Society For Microbiology
Copyright
Copyright © 2013 by the American society for Microbiology.
ISSN
0021-9193
eISSN
1098-5530
DOI
10.1128/JB.00186-13
pmid
23524612
Publisher site
See Article on Publisher Site

Abstract

The General Stress Response Factor EcfG Regulates Expression of the C-2 Hopanoid Methylase HpnP in Rhodopseudomonas palustris TIE-1 Gargi Kulkarni a , b , Chia-Hung Wu a and Dianne K. Newman a , b , c Division of Biology, California Institute of Technology, Pasadena, California, USA a Howard Hughes Medical Institute, Pasadena, California, USA b Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA c ABSTRACT Lipid molecules preserved in sedimentary rocks facilitate the reconstruction of events that have shaped the evolution of the Earth's biosphere. A key limitation for the interpretation of many of these molecular fossils is that their biological roles are still poorly understood. Here, we use Rhodopseudomonas palustris TIE-1 to identify factors that induce biosynthesis of 2-methyl hopanoids (2-MeBHPs), progenitors of 2-methyl hopanes, one of the most abundant biomarkers in the rock record. This is the first dissection of the regulation of hpnP , the gene encoding the C-2 hopanoid methylase, at the molecular level. We demonstrate that EcfG, the general stress response factor of alphaproteobacteria, regulates expression of hpnP under a variety of challenges, including high temperature, pH stress, and presence of nonionic osmolytes. Although higher hpnP transcription levels did not always result in higher amounts of total methylated hopanoids, the fraction of a particular kind of hopanoid, 2-methyl bacteriohopanetetrol, was consistently higher in the presence of most stressors in the wild type, but not in the Δ ecfG mutant, supporting a beneficial role for 2-MeBHPs in stress tolerance. The Δ hpnP mutant, however, did not exhibit a growth defect under the stress conditions tested except in acidic medium. This indicates that the inability to make 2-MeBHPs under most of these conditions can readily be compensated. Although stress is necessary to regulate 2-MeBHP production, the specific conditions under which 2-MeBHP biosynthesis is essential remain to be determined.

Journal

Journal of BacteriologyAmerican Society For Microbiology

Published: Jun 1, 2013

References