[ { "id": "authors:5hcmg-zsr04", "collection": "authors", "collection_id": "5hcmg-zsr04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170518-163637436", "type": "book_section", "title": "Molecular Methods in Geomicrobiology", "book_title": "Ehrlich's Geomicrobiology, Sixth Edition", "author": [ { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "contributor": [ { "family_name": "Ehrlich", "given_name": "Henry Lutz", "clpid": "Ehrlich-H-L" }, { "family_name": "Newman", "given_name": "Dianne K.", "clpid": "Newman-D-K" }, { "family_name": "Kappler", "given_name": "Andreas", "clpid": "Kappler-A" } ], "abstract": "In addition to the techniques described in Chapter 8, molecular tools have become increasingly important in the study of the presence, activity, and mechanisms of catalysis by geomicrobial organisms. Today, various molecules (deoxyribonucleic acid [DNA], ribonucleic acid [RNA], protein, and lipids) are used to detect specific geomicrobial agents in situ and make inferences about their metabolic activity. DNA sequencing has become routine, expanding our appreciation of the genetic potential of uncultivated organisms and complex natural communities from the environment. Isotope labeling approaches allow us to measure metabolic activity more directly and to specifically link organisms with geochemical fluxes. Finally, the application of molecular genetic, cell biological, and biochemical techniques to study the genes and gene products that catalyze geochemically significant reactions is unraveling the mechanisms underlying these processes. Together, these molecular approaches provide a window into the interactions between microorganisms and their geochemical environment and enable predictions about how these geomicrobial processes may be altered in response to environmental perturbations.", "doi": "10.1201/b19121-10", "isbn": "9781466592407", "publisher": "CRC Press", "place_of_publication": "Boca Raton, FL", "publication_date": "2015-10", "pages": "187-207" }, { "id": "authors:4j2za-44r54", "collection": "authors", "collection_id": "4j2za-44r54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140407-105009295", "type": "article", "title": "Diverse capacity for 2-methylhopanoid production correlates with a specific ecological niche", "author": [ { "family_name": "Ricci", "given_name": "Jessica N.", "clpid": "Ricci-J-N" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Welander", "given_name": "Paul V.", "clpid": "Welander-P-V" }, { "family_name": "Sessions", "given_name": "Alex L.", "orcid": "0000-0001-6120-2763", "clpid": "Sessions-A-L" }, { "family_name": "Summons", "given_name": "Roger E.", "orcid": "0000-0002-7144-8537", "clpid": "Summons-R-E" }, { "family_name": "Spear", "given_name": "John R.", "orcid": "0000-0002-4664-7438", "clpid": "Spear-J-R" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "abstract": "Molecular fossils of 2-methylhopanoids are prominent biomarkers in modern and ancient sediments that have been used as proxies for cyanobacteria and their main metabolism, oxygenic photosynthesis. However, substantial culture and genomic-based evidence now indicates that organisms other than cyanobacteria can make 2-methylhopanoids. Because few data directly address which organisms produce 2-methylhopanoids in the environment, we used metagenomic and clone library methods to determine the environmental diversity of hpnP, the gene encoding the C-2 hopanoid methylase. Here we show that hpnP copies from alphaproteobacteria and as yet uncultured organisms are found in diverse modern environments, including some modern habitats representative of those preserved in the rock record. In contrast, cyanobacterial hpnP genes are rarer and tend to be localized to specific habitats. To move beyond understanding the taxonomic distribution of environmental 2-methylhopanoid producers, we asked whether hpnP presence might track with particular variables. We found hpnP to be significantly correlated with organisms, metabolisms and environments known to support plant\u2013microbe interactions (P-value<10^\u22126); in addition, we observed diverse hpnP types in closely packed microbial communities from other environments, including stromatolites, hot springs and hypersaline microbial mats. The common features of these niches indicate that 2-methylhopanoids are enriched in sessile microbial communities inhabiting environments low in oxygen and fixed nitrogen with high osmolarity. Our results support the earlier conclusion that 2-methylhopanoids are not reliable biomarkers for cyanobacteria or any other taxonomic group, and raise the new hypothesis that, instead, they are indicators of a specific environmental niche.", "doi": "10.1038/ismej.2013.191", "pmcid": "PMC3930323", "issn": "1751-7362", "publisher": "Nature Publishing Group", "publication": "ISME Journal", "publication_date": "2014-03", "series_number": "3", "volume": "8", "issue": "3", "pages": "675-684" }, { "id": "authors:vjgq9-gdr22", "collection": "authors", "collection_id": "vjgq9-gdr22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130709-082907927", "type": "article", "title": "Iron and Copper Act Synergistically To Delay Anaerobic Growth of Bacteria", "author": [ { "family_name": "Bird", "given_name": "Lina J.", "orcid": "0000-0003-4127-4756", "clpid": "Bird-L-J" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "abstract": "Transition metals are known to cause toxic effects through their interaction with oxygen, but toxicity under anoxic conditions is poorly understood. Here we investigated the effects of iron (Fe) and copper (Cu) on the anaerobic growth and gene expression of the purple phototrophic bacterium Rhodopseudomonas palustris TIE-1. We found that Fe(II) and Cu(II) act synergistically to delay anaerobic growth at environmentally relevant metal concentrations. Cu(I) and Cu(II) had similar effects both alone and in the presence of ascorbate, a Cu(II) reductant, indicating that reduction of Cu(II) to Cu(I) by Fe(II) is not sufficient to explain the growth inhibition. Addition of Cu(II) increased the toxicity of Co(II) and Ni(II); in contrast, Ni(II) toxicity was diminished in the presence of Fe(II). The synergistic anaerobic toxicity of Fe(II) and Cu(II) was also observed for Escherichia coli MG1655, Shewanella oneidensis MR-1, and Rhodobacter capsulatus SB1003. Gene expression analyses for R. palustris identified three regulatory genes that respond to Cu(II) and not to Fe(II): homologs of cueR and cusR, two known proteobacterial copper homeostasis regulators, and csoR, a copper regulator recently identified in Mycobacterium tuberculosis. Two P-type ATPase efflux pumps, along with an F_oF_1 ATP synthase, were also upregulated by Cu(II) but not by Fe(II). An Escherichia coli mutant deficient in copA, cus, and cueO showed a smaller synergistic effect, indicating that iron might interfere with one or more of the copper homeostasis systems. Our results suggest that interactive effects of transition metals on microbial physiology may be widespread under anoxic conditions, although the molecular mechanisms remain to be more fully elucidated.", "doi": "10.1128/AEM.03944-12", "pmcid": "PMC3675935", "issn": "0099-2240", "publisher": "American Society for Microbiology", "publication": "Applied and Environmental Microbiology", "publication_date": "2013-06", "series_number": "12", "volume": "79", "issue": "12", "pages": "3619-3627" }, { "id": "authors:2fyqr-g3d23", "collection": "authors", "collection_id": "2fyqr-g3d23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160301-135518164", "type": "book_section", "title": "In situ geochronology as a mission-enabling technology", "book_title": "2012 IEEE Aerospace Conference", "author": [ { "family_name": "Coleman", "given_name": "Max", "clpid": "Coleman-M-L" }, { "family_name": "Hecht", "given_name": "Michael H.", "clpid": "Hecht-M-H" }, { "family_name": "Hurowitz", "given_name": "Joel", "orcid": "0000-0002-5857-8652", "clpid": "Hurowitz-J-A" }, { "family_name": "Neidholdt", "given_name": "Evan", "clpid": "Neidholdt-E-L" }, { "family_name": "Polk", "given_name": "James E.", "clpid": "Polk-J-E" }, { "family_name": "Sinha", "given_name": "Mahadeva P.", "clpid": "Sinha-M-P" }, { "family_name": "Sturhahn", "given_name": "Wolfgang", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Zimmermann", "given_name": "Wayne", "clpid": "Zimmermann-W-Jr" } ], "abstract": "Although there are excellent estimates of ages of terrains on Mars from crater counting, even a few absolute ages would serve to validate the calibration. Results with uncertainties, although much larger than those that could be achieved in labs on Earth, would be extremely valuable. While there are other possibilities for in situ geochronology instruments, we describe here two alternative technologies, being developed in JPL. There are two common features of both. The first is analysis by means of miniature mass spectrometer. The second is use of laser sampling to reduce or avoid sample handling, preparation and pre-treatment and equally importantly, to allow analysis of individual, texturally resolved minerals in coarse-grained rocks. This textural resolution will aid in selection of grains more or less enriched in the relevant elements and allow construction of isochrons for more precise dating. Either of these instruments could enable missions to Mars and other planetary bodies.", "doi": "10.1109/AERO.2012.6187053", "isbn": "978-1-4577-0556-4", "publisher": "IEEE", "place_of_publication": "Piscataway, NJ", "publication_date": "2012-03", "pages": "1-8" }, { "id": "authors:ftpg0-0v412", "collection": "authors", "collection_id": "ftpg0-0v412", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120323-082322420", "type": "article", "title": "BqsR/BqsS Constitute a Two-Component System That Senses Extracellular Fe(II) in Pseudomonas aeruginosa", "author": [ { "family_name": "Kreamer", "given_name": "Naomi N. K.", "clpid": "Kreamer-N-N-K" }, { "family_name": "Wilks", "given_name": "Jessica C.", "clpid": "Wilks-J-C" }, { "family_name": "Marlow", "given_name": "Jeffrey J.", "clpid": "Marlow-J-J" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "abstract": "Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium best known as the predominant opportunistic pathogen infecting the lungs of cystic fibrosis patients. In this context, it is thought to form biofilms, within which locally reducing and acidic conditions can develop that favor the stability of ferrous iron [Fe(II)]. Because iron is a signal that stimulates biofilm formation, we performed a microarray study to determine whether P. aeruginosa strain PA14 exhibits a specific transcriptional response to extracellular Fe(II). Among the genes that were most upregulated in response to Fe(II) were those encoding the two-component system BqsR/BqsS, previously identified for its role in P. aeruginosa strain PAO1 biofilm decay (13); here, we demonstrate its role in extracellular Fe(II) sensing. bqsS and bqsR form an operon together with two small upstream genes, bqsP and bqsQ, and one downstream gene, bqsT. BqsR/BqsS sense extracellular Fe(II) at physiologically relevant concentrations (>10 \u03bcM) and elicit a specific transcriptional response, including its autoregulation. The sensor distinguishes between Fe(II), Fe(III), and other dipositive cations [Ca(II), Cu(II), Mg(II), Mn(II), Zn(II)] under aerobic or anaerobic conditions. The gene that is most upregulated by BqsR/BqsS, as measured by quantitative reverse transcription-PCR (qRT-PCR), is PA14_04180, which is predicted to encode a periplasmic oligonucleotide/oligosaccharide-binding domain (OB-fold) protein. Coincident with phenazine production during batch culture growth, Fe(II) becomes the majority of the total iron pool and bqsS is upregulated. The existence of a two-component system that senses Fe(II) indicates that extracellular Fe(II) is an important environmental signal for P. aeruginosa.", "doi": "10.1128/JB.05634-11", "pmcid": "PMC3294787", "issn": "0021-9193", "publisher": "American Society for Microbiology", "publication": "Journal of Bacteriology", "publication_date": "2012-03", "series_number": "5", "volume": "194", "issue": "5", "pages": "1195-1204" }, { "id": "authors:prr8s-y3373", "collection": "authors", "collection_id": "prr8s-y3373", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111128-101611198", "type": "article", "title": "The RND-family transporter, HpnN, is required for hopanoid localization to the outer membrane of Rhodopseudomonas palustris TIE-1", "author": [ { "family_name": "Doughty", "given_name": "David M.", "clpid": "Doughty-D-M" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Hunter", "given_name": "Ryan C.", "orcid": "0000-0003-3841-1676", "clpid": "Hunter-Ryan-C" }, { "family_name": "Sessions", "given_name": "Alex L.", "orcid": "0000-0001-6120-2763", "clpid": "Sessions-A-L" }, { "family_name": "Summons", "given_name": "Roger E.", "orcid": "0000-0002-7144-8537", "clpid": "Summons-R-E" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "abstract": "Rhodopseudomonas palustris TIE-1 is a Gram-negative bacterium that produces structurally diverse hopanoid lipids that are similar to eukaryotic steroids. Its genome encodes several homologues to proteins involved in eukaryotic steroid trafficking. In this study, we explored the possibility that two of these proteins are involved\nin intracellular hopanoid transport. R. palustris has a sophisticated membrane system comprising outer, cytoplasmic, and inner cytoplasmic membranes. It also divides asymmetrically, producing a mother and swarmer cell. We deleted genes encoding two putative hopanoid transporters that belong to the resistance\u2013nodulation\u2013\ncell division superfamily. Phenotypic analyses revealed that\none of these putative transporters (HpnN) is essential for the movement of hopanoids from the cytoplasmic to the outer membrane, whereas the other (Rpal_4267) plays a minor role. C30 hopanoids, such as diploptene, are evenly distributed between mother and swarmer cells, whereas hpnN is required for the C35 hopanoid, bacteriohopanetetrol, to remain localized to the mother cell type. Mutant cells lacking HpnN grow like the WT at 30 \u00b0C but slower at 38 \u00b0C. Following cell division at 38 \u00b0C, the \u0394hpnN cells remain\nconnected by their cell wall, forming long filaments. This phenotype may be attributed to hopanoid mislocalization because a double mutant deficient in both hopanoid biosynthesis and transport does not form filaments. However, the lack of hopanoids severely compromises cell growth at higher temperatures more generally. Because hopanoid mutants only manifest a strong phenotype under\ncertain conditions, R. palustris is an attractive model organism in which to study their transport and function.", "doi": "10.1073/pnas.1104209108", "pmcid": "PMC3215060", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2011-11-08", "series_number": "45", "volume": "108", "issue": "45", "pages": "E1045-E1051" }, { "id": "authors:6g7nc-6bv19", "collection": "authors", "collection_id": "6g7nc-6bv19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160301-141416249", "type": "conference_item", "title": "In-Situ K-Ar Geochronology: Age Dating for Solar System Sample Return Selection", "author": [ { "family_name": "Hurowitz", "given_name": "J.", "orcid": "0000-0002-5857-8652", "clpid": "Hurowitz-J-A" }, { "family_name": "Aharonson", "given_name": "O.", "orcid": "0000-0001-9930-2495", "clpid": "Aharonson-O" }, { "family_name": "Channon", "given_name": "M.", "clpid": "Channon-M-B" }, { "family_name": "Chemtob", "given_name": "S.", "clpid": "Chemtob-S-M" }, { "family_name": "Coleman", "given_name": "M.", "clpid": "Coleman-M-L" }, { "family_name": "Eiler", "given_name": "J.", "clpid": "Eiler-J-M" }, { "family_name": "Farley", "given_name": "K. A.", "orcid": "0000-0002-7846-7546", "clpid": "Farley-K-A" }, { "family_name": "Grotzinger", "given_name": "J. P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" }, { "family_name": "Hecht", "given_name": "M.", "clpid": "Hecht-M-H" }, { "family_name": "Kirschvink", "given_name": "J. L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "McLeese", "given_name": "D.", "clpid": "McLeese-D" }, { "family_name": "Neidholdt", "given_name": "E.", "clpid": "Neidholdt-E-L" }, { "family_name": "Rossman", "given_name": "G. R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Sinha", "given_name": "M.", "clpid": "Sinha-M-P" }, { "family_name": "Sturhahn", "given_name": "W.", "orcid": "0000-0002-9606-4740", "clpid": "Sturhahn-W" }, { "family_name": "Waltenberg", "given_name": "K.", "clpid": "Waltenberg-K" }, { "family_name": "Vasconcelos", "given_name": "P.", "clpid": "Vasconcelos-P-M" }, { "family_name": "Zimmermann", "given_name": "W.", "clpid": "Zimmermann-W-Jr" }, { "family_name": "Beard", "given_name": "B.", "clpid": "Beard-B-L" }, { "family_name": "Johnson", "given_name": "C.", "clpid": "Johnson-C" } ], "abstract": "The development of an in-situ\ngeochronology capability for Mars and other planetary\nsurfaces has the potential to fundamentally change our\nunderstanding of the evolution of terrestrial bodies in\nthe Solar System. For Mars specifically, many of our\nmost basic scientific questions about the geologic history\nof the planet require accurate knowledge of the\nabsolute time at which an event or process took place.\nFor instance, what was the age and rate of early Martian\nclimate change faithfully recorded in the mineralogy\nand morphology of surface lithologies (e.g., [1])?\nCurrently, our only means of assessing the absolute\nage of a surface on a planetary body is through the use\nof crater counting statistics. This technique is fraught\nwith uncertainty for planets with active geologic surfaces,\non the order of billions of years in some cases\n(e.g., [2]). Accordingly, there is much room for improvement\nin our understanding of the absolute chronology\nof the surfaces of rocky planetary bodies.", "publisher": "Caltech Library", "publication_date": "2011-03" }, { "id": "authors:db2va-gec91", "collection": "authors", "collection_id": "db2va-gec91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110307-110335931", "type": "article", "title": "Where reductionism meets complexity: a call for growth in the study of non-growth", "author": [ { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" } ], "abstract": "With the advent of metagenomics, we have unprecedented\naccess to the genetic blueprint of the microbial\nworld. Yet as metagenomic databases keep growing, our\nability to interpret the information contained within\nthem has not kept up. This conundrum arises from the\nfact that we cannot assign functions to the vast majority\nof their genes. As Jo Handelsman pointed out in a\nCrystal Ball piece two years ago, 'the glory of the last 50\nyears of microbiology is founded, in large part, on\ngenetic analysis' (Handelsman, 2009). Amen. Yet as\nenticing as the prospect of environmental genetics or\n'metagenetics' seems, how can we hope to interpret the\nunchartered world of environmental metagenomes when\nafter more than a half-century of rigorous genetic and\nbiochemical analyses, the functions of roughly a quarter\nof the genes in Escherichia coli \u2013 arguably the most\nwell-studied organism on the planet \u2013 are still unknown\n(Karp et al., 2007)? Where have we gone wrong?\nPerhaps it is time to re-examine our assumptions about\nhow to assign gene functions in light of lessons from the\nfield.", "doi": "10.1111/j.1758-2229.2010.00236.x", "issn": "1758-2229", "publisher": "Wiley-Blackwell", "publication": "Environmental Microbiology Reports", "publication_date": "2011-02", "series_number": "1", "volume": "3", "issue": "1", "pages": "14-15" }, { "id": "authors:n0ee3-8ax91", "collection": "authors", "collection_id": "n0ee3-8ax91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100601-111422016", "type": "article", "title": "Identification of a methylase required for 2-methylhopanoid production and implications for the interpretation of sedimentary hopanes", "author": [ { "family_name": "Welander", "given_name": "Paula V.", "clpid": "Welander-P-V" }, { "family_name": "Coleman", "given_name": "Maureen L.", "clpid": "Coleman-M-L" }, { "family_name": "Sessions", "given_name": "Alex L.", "orcid": "0000-0001-6120-2763", "clpid": "Sessions-A-L" }, { "family_name": "Summons", "given_name": "Roger E.", "orcid": "0000-0002-7144-8537", "clpid": "Summons-R-E" }, { "family_name": "Newman", "given_name": "Dianne K.", "orcid": "0000-0003-1647-1918", "clpid": "Newman-D-K" } ], "abstract": "The rise of atmospheric oxygen has driven environmental change and biological evolution throughout much of Earth's history and was enabled by the evolution of oxygenic photosynthesis in the cyanobacteria. Dating this metabolic innovation using inorganic proxies from sedimentary rocks has been difficult and one important approach has been to study the distributions of fossil lipids, such as steranes and 2-methylhopanes, as biomarkers for this process. 2-methylhopanes arise from degradation of 2-methylbacteriohopanepolyols (2-MeBHPs), lipids thought to be synthesized primarily by cyanobacteria. The discovery that 2-MeBHPs are produced by an anoxygenic phototroph, however, challenged both their taxonomic link with cyanobacteria and their functional link with oxygenic photosynthesis. Here, we identify a radical SAM methylase encoded by the hpnP gene that is required for methylation at the C-2 position in hopanoids. This gene is found in several, but not all, cyanobacteria and also in \u03b1 -proteobacteria and acidobacteria. Thus, one cannot extrapolate from the presence of 2-methylhopanes alone, in modern environments or ancient sedimentary rocks, to a particular taxonomic group or metabolism. To understand the origin of this gene, we reconstructed the evolutionary history of HpnP. HpnP proteins from cyanobacteria, Methylobacterium species, and other \u03b1-proteobacteria form distinct phylogenetic clusters, but the branching order of these clades could not be confidently resolved. Hence,it is unclear whether HpnP, and 2-methylhopanoids, originated first in the cyanobacteria. In summary, existing evidence does not support the use of 2-methylhopanes as biomarkers for oxygenic photosynthesis.", "doi": "10.1073/pnas.0912949107", "pmcid": "PMC2889317", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2010-05-11", "series_number": "19", "volume": "107", "issue": "19", "pages": "8537-8542" }, { "id": "authors:d0rn7-w1f68", "collection": "authors", "collection_id": "d0rn7-w1f68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090731-114526170", "type": "article", "title": "Controls on development and diversity of Early Archean stromatolites", "author": [ { "family_name": "Allwood", "given_name": "Abigail C.", "clpid": "Allwood-A-C" }, { "family_name": "Grotzinger", "given_name": "John P.", "orcid": "0000-0001-9324-1257", "clpid": "Grotzinger-J-P" }, { "family_name": "Knoll", "given_name": "Andrew H.", "orcid": "0000-0003-1308-8585", "clpid": "Knoll-A-H" }, { "family_name": "Burch", "given_name": "Ian W.", "clpid": "Burch-I-W" }, { "family_name": "Anderson", "given_name": "Mark S.", "clpid": "Anderson-M-S" }, { "family_name": "Coleman", "given_name": "Max L.", "clpid": "Coleman-M-L" }, { "family_name": "Kanik", "given_name": "Isik", "orcid": "0000-0002-7912-2865", "clpid": "Kanik-Isik" } ], "abstract": "The \u22483,450-million-year-old Strelley Pool Formation in Western Australia contains a reef-like assembly of laminated sedimentary accretion structures (stromatolites) that have macroscale characteristics suggestive of biological influence. However, direct microscale evidence of biology\u2014namely, organic microbial remains or biosedimentary fabrics\u2014has to date eluded discovery in the extensively-recrystallized rocks. Recently-identified outcrops with relatively good textural preservation record microscale evidence of primary sedimentary processes, including some that indicate probable microbial mat formation. Furthermore, we find relict fabrics and organic layers that covary with stromatolite morphology, linking morphologic diversity to changes in sedimentation, seafloor mineral precipitation, and inferred microbial mat development. Thus, the most direct and compelling signatures of life in the Strelley Pool Formation are those observed at the microscopic scale. By examining spatiotemporal changes in microscale characteristics it is possible not only to recognize the presence of probable microbial mats during stromatolite development, but also to infer aspects of the biological inputs to stromatolite morphogenesis. The persistence of an inferred biological signal through changing environmental circumstances and stromatolite types indicates that benthic microbial populations adapted to shifting environmental conditions in early oceans.", "doi": "10.1073/pnas.0903323106", "pmcid": "PMC2700989", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2009-06-16", "series_number": "24", "volume": "106", "issue": "24", "pages": "9548-9555" }, { "id": "authors:z7jkd-zp261", "collection": "authors", "collection_id": "z7jkd-zp261", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170412-071903575", "type": "article", "title": "Pyrohydrolysis-IRMS determination of silicate chlorine stable isotope compositions. Application to oceanic crust and meteorite samples", "author": [ { "family_name": "Bonifacie", "given_name": "Magali", "clpid": "Bonifacie-M" }, { "family_name": "Jendrzejewski", "given_name": "Nathalie", "clpid": "Jendrzejewski-N" }, { "family_name": "Agrinier", "given_name": "Pierre", "clpid": "Agrinier-P" }, { "family_name": "Coleman", "given_name": "Max", "clpid": "Coleman-M-L" }, { "family_name": "Pineau", "given_name": "Fran\u00e7oise", "clpid": "Pineau-F" }, { "family_name": "Javoy", "given_name": "Marc", "clpid": "Javoy-M" } ], "abstract": "This contribution describes the optimization of chlorine extraction from silicate samples by pyrohydrolysis prior to the precise determination of Cl stable-isotope compositions (\u03b4^(37)Cl) by gas source, dual inlet Isotope Ratio Mass Spectrometry (IRMS) on CH_3Clg. The complete method was checked on three international reference materials for Cl-content and two laboratory glass standards.\n\nWhole procedure blanks are lower than 0.5 \u03bcmol, corresponding to less than 10 wt.% of most of the sample chloride analysed. In the absence of international chlorine isotope rock, we report here Cl extracted compared to accepted Cl contents and reproducibilities on Cl and \u03b4^(37)Cl measurements for the standard rocks. After extraction, the Cl contents of the three international references compared within error with the accepted values (mean yield = 94 \u00b1 10%) with reproducibilities better than 12% (1\u03c3). The laboratory glass standards \u2013 andesite SO100DS92 and phonolite S9(2) \u2013 were used specifically to test the effect of chloride amount on the measurements. They gave Cl extraction yields of 100 \u00b1 6% (1\u03c3; n = 15) and 105 \u00b1 8% (1\u03c3; n = 7), respectively, with \u03b4^(37)Cl values of \u2212 0.51 \u00b1 0.14\u2030 and \u2212 0.39 \u00b1 0.17\u2030 (1\u03c3). In summary, for silicate samples with Cl contents between 39 and 9042 ppm, the Pyrohydrolysis/HPLC method leads to overall Cl extraction yields of 100 \u00b1 8%, reproducibilities on Cl contents of 7% and on \u03b4^(37)Cl measurements of \u00b1 0.12\u2030 (all 1\u03c3).\n\nThe method was further applied to ten silicate rocks of various mineralogy and chemistry (meteorite, fresh MORB glasses, altered basalts and serpentinized peridotites) chosen for their large range of Cl contents (70\u20132156 ppm) and their geological significance. \u03b4^(37)Cl values range between \u2212 2.33 and \u2212 0.50\u2030. These strictly negative values contrast with the large range and mainly positive values previously reported for comparable silicate samples and shown here to be affected by analytical problems. Thus we propose a preliminary, revised terrestrial Cl cycle, mainly dominated by negative and zero \u03b4^(37)Cl values.", "doi": "10.1016/j.chemgeo.2007.03.012", "issn": "0009-2541", "publisher": "Elsevier", "publication": "Chemical Geology", "publication_date": "2007-07-30", "series_number": "1-2", "volume": "242", "issue": "1-2", "pages": "187-201" } ]