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Phylogenetic analysis of HpnP reveals the origin of 2-methylhopanoid production in Alphaproteobacteria

Ricci, J. N. and Michel, A. J. and Newman, D. K. (2015) Phylogenetic analysis of HpnP reveals the origin of 2-methylhopanoid production in Alphaproteobacteria. Geobiology, 13 (3). pp. 267-277. ISSN 1472-4677. http://resolver.caltech.edu/CaltechAUTHORS:20150202-095339879

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Abstract

Hopanoids are bacterial steroid-like lipids that can be preserved in the rock record on billion-year timescales. 2-Methylhopanoids are of particular interest to geobiologists because methylation is one of the few chemical modifications that remain after diagenesis and catagenesis. 2-Methylhopanes, the molecular fossils of 2-methylhopanoids, are episodically enriched in the rock record, but we do not have a robust interpretation for their abundance patterns. Here, we exploit the evolutionary record found in molecular sequences from extant organisms to reconstruct the biosynthetic history of 2-methylhopanoids using the C-2 hopanoid methylase, HpnP. Based on HpnP phylogenetic analysis, we find that 2-methylhopanoids originated in a subset of the Alphaproteobacteria. This conclusion is statistically robust and reproducible in multiple trials varying the outgroup, trimming stringency, and ingroup dataset used to infer the evolution of this protein family. The capacity for 2-methylhopanoid production was likely horizontally transferred from the Alphaproteobacteria into the Cyanobacteria after the Cyanobacteria's major divergences. Together, these results suggest that the ancestral function of 2-methylhopanoids was not related to oxygenic photosynthesis but instead to a trait already present in the Alphaproteobacteria. Moreover, given that early 2-methylhopane deposits could have been made solely by Alphaproteobacteria before the acquisition of hpnP by Cyanobacteria, and that the Alphaproteobacteria are thought to be ancestrally aerobic, we infer that 2-methylhopanoids likely arose after the oxygenation of the atmosphere. This finding is consistent with the geologic record—the oldest syngenetic 2-methylhopanes occur after the rise of oxygen, in middle Proterozoic strata of the Barney Creek Formation.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1111/gbi.12129DOIArticle
http://onlinelibrary.wiley.com/doi/10.1111/gbi.12129/abstractPublisherArticle
http://onlinelibrary.wiley.com/doi/10.1111/gbi.12129/suppinfoPublisherSupporting Information
Additional Information:© 2015 John Wiley & Sons Ltd. Received 2 December 2014; accepted 10 January 2015. Article first published online: 29 January 2015. We would like to thank Woodward Fischer, James Hemp, Jena Johnson, and members of the Newman Lab for their helpful suggestions. We are grateful to John Spear for providing samples from Yellowstone National Park through the Yellowstone Center for Resources (permit #5664). This work was supported by grants from NASA (NNX12AD93G), the National Science Foundation (1224158), and the Howard Hughes Medical Institute (HHMI) to DKN. JNR is supported by an NSF graduate fellowship. DKN is an Investigator of the Howard Hughes Medical Institute.
Funders:
Funding AgencyGrant Number
NASANNX12AD93G
NSF1224158
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
NSF Graduate FellowshipUNSPECIFIED
Record Number:CaltechAUTHORS:20150202-095339879
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150202-095339879
Official Citation:Ricci, J. N., Michel, A. J. and Newman, D. K. (2015), Phylogenetic analysis of HpnP reveals the origin of 2-methylhopanoid production in Alphaproteobacteria. Geobiology, 13: 267–277. doi: 10.1111/gbi.12129
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54286
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:04 Feb 2015 23:09
Last Modified:08 May 2015 16:39

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