Visiting Professor, Earth System Science
Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals.
Nature ecology & evolution
2018; 2 (11): 1709–14
Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C30 sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.
View details for DOI 10.1038/s41559-018-0676-2
View details for PubMedID 30323207
Acetoclastic Methanosaeta are dominant methanogens in organic-rich Antarctic marine sediments
2018; 12 (2): 330–42
Despite accounting for the majority of sedimentary methane, the physiology and relative abundance of subsurface methanogens remain poorly understood. We combined intact polar lipid and metagenome techniques to better constrain the presence and functions of methanogens within the highly reducing, organic-rich sediments of Antarctica's Adélie Basin. The assembly of metagenomic sequence data identified phylogenic and functional marker genes of methanogens and generated the first Methanosaeta sp. genome from a deep subsurface sedimentary environment. Based on structural and isotopic measurements, glycerol dialkyl glycerol tetraethers with diglycosyl phosphatidylglycerol head groups were classified as biomarkers for active methanogens. The stable carbon isotope (δ13C) values of these biomarkers and the Methanosaeta partial genome suggest that these organisms are acetoclastic methanogens and represent a relatively small (0.2%) but active population. Metagenomic and lipid analyses suggest that Thaumarchaeota and heterotrophic bacteria co-exist with Methanosaeta and together contribute to increasing concentrations and δ13C values of dissolved inorganic carbon with depth. This study presents the first functional insights of deep subsurface Methanosaeta organisms and highlights their role in methane production and overall carbon cycling within sedimentary environments.
View details for DOI 10.1038/ismej.2017.150
View details for Web of Science ID 000422779100004
View details for PubMedID 29039843
View details for PubMedCentralID PMC5776447
Methane Oxidation and Molecular Characterization of Methanotrophs from a Former Mercury Mine Impoundment.
2015; 3 (2): 290-309
The Herman Pit, once a mercury mine, is an impoundment located in an active geothermal area. Its acidic waters are permeated by hundreds of gas seeps. One seep was sampled and found to be composed of mostly CO₂ with some CH₄ present. The δ(13)CH₄ value suggested a complex origin for the methane: i.e., a thermogenic component plus a biological methanogenic portion. The relatively (12)C-enriched CO₂ suggested a reworking of the ebullitive methane by methanotrophic bacteria. Therefore, we tested bottom sediments for their ability to consume methane by conducting aerobic incubations of slurried materials. Methane was removed from the headspace of live slurries, and subsequent additions of methane resulted in faster removal rates. This activity could be transferred to an artificial, acidic medium, indicating the presence of acidophilic or acid-tolerant methanotrophs, the latter reinforced by the observation of maximum activity at pH = 4.5 with incubated slurries. A successful extraction of sterol and hopanoid lipids characteristic of methanotrophs was achieved, and their abundances greatly increased with increased sediment methane consumption. DNA extracted from methane-oxidizing enrichment cultures was amplified and sequenced for pmoA genes that aligned with methanotrophic members of the Gammaproteobacteria. An enrichment culture was established that grew in an acidic (pH 4.5) medium via methane oxidation.
View details for DOI 10.3390/microorganisms3020290
View details for PubMedID 27682090
View details for PubMedCentralID PMC5023233
Elucidation of the Burkholderia cenocepacia hopanoid biosynthesis pathway uncovers functions for conserved proteins in hopanoid-producing bacteria
2015; 17 (3): 735-750
Hopanoids are bacterial surrogates of eukaryotic membrane sterols and among earth's most abundant natural products. Their molecular fossils remain in sediments spanning more than a billion years. However, hopanoid metabolism and function are not fully understood. Burkholderia species are environmental opportunistic pathogens that produce hopanoids and also occupy diverse ecological niches. We investigated hopanoids biosynthesis in Burkholderia cenocepacia by deletion mutagenesis and structural characterization of the hopanoids produced by the mutants. The enzymes encoded by hpnH and hpnG were essential for production of all C35 extended hopanoids, including bacteriohopanetetrol (BHT), BHT glucosamine and BHT cyclitol ether. Deletion of hpnI resulted in BHT production, while ΔhpnJ produced only BHT glucosamine. Thus, HpnI is required for BHT glucosamine production while HpnJ is responsible for its conversion to the cyclitol ether. The ΔhpnH and ΔhpnG mutants could not grow under any stress condition tested, whereas ΔhpnI, ΔhpnJ and ΔhpnK displayed wild-type growth rates when exposed to detergent, but varying levels of sensitivity to low pH and polymyxin B. This study not only elucidates the biosynthetic pathway of hopanoids in B. cenocepacia, but also uncovers a biosynthetic role for the conserved proteins HpnI, HpnJ and HpnK in other hopanoid-producing bacteria.
View details for DOI 10.1111/1462-2920.12509
View details for Web of Science ID 000351435600019
View details for PubMedID 24888970
- Molecular biosignatures SPACE SCIENCE REVIEWS 2008; 135 (1-4): 133-159
EXTENDED 3-BETA-ALKYL STERANES AND 3-ALKYL TRIAROMATIC STEROIDS IN CRUDE OILS AND ROCK EXTRACTS
GEOCHIMICA ET COSMOCHIMICA ACTA
1995; 59 (18): 3717-3729
View details for Web of Science ID A1995RX60700005
STABLE ISOTOPE MASS FRAGMENTOGRAPHY - IDENTIFICATION AND HYDROGEN-DEUTERIUM EXCHANGE STUDIES OF 8 MURCHISON METEORITE AMINO-ACIDS
GEOCHIMICA ET COSMOCHIMICA ACTA
1975; 39 (2): 163-172
View details for Web of Science ID A1975V103600005
METABOLIC STUDIES OF TRANSIENT TYROSINEMIA IN PREMATURE-INFANTS
1975; 9 (4): 172-176
The recently developed technique of gas chromatography-mass spectrometry supported by computer has considerably improved the analysis of physiologic fluids. This study attempted to demonstrate the value of this system in the investigation of metabolite patterns in urine in two metabolic problems of prematurity, transient tyrosinemia and late metabolic acidosis. Serial 24-hr urine specimens were analyzed in 9 infants. Transient tyrosinemia, characterized by 5-10-fold increases over basal excretion of tyrosine, p-hydroxyphenyllactate, and p-hydroxyphenylpyruvate in urine, was noted in five of the infants. Several infants had fluctuating levels of tyrosine metabolites in urine although dietary protein intake remained constant at 3-4 g/kg/24 hr and ascorbic acid at 50 mg/24 hr. Late metabolic acidosis was seen in four infants, but bore no relation to transient tyrosinemia. The ratio of net acid to urea excretion in urine increased with increasing base deficit, implying a nonprotein origin of the metabolic acid. No unique metabolic patterns were characteristic of late metabolic acidosis.
View details for Web of Science ID A1975V958900006
View details for PubMedID 1143952
PSYCHOTRIDINE, A C55H62N10 ALKALOID FROM PSYCHOTRIA-BECCARIOIDES (RUBIACEAE)
AUSTRALIAN JOURNAL OF CHEMISTRY
1974; 27 (3): 639-646
View details for Web of Science ID A1974S620900013
DICARBOXYLIC-ACIDS IN MURCHISON METEORITE
1974; 251 (5470): 41-42
View details for Web of Science ID A1974T986100028
- ANALYSIS OF 12 AMINO-ACIDS IN BIOLOGICAL-FLUIDS BY MASS FRAGMENTOGRAPHY ANALYTICAL CHEMISTRY 1974; 46 (4): 582-587
STUDY OF ELECTRON-IMPACT PROMOTED FRAGMENTATION OF PROMAZINE SULFOXIDE AND PROMAZINE USING SPECIFICALLY DEUTERATED ANALOGS
AUSTRALIAN JOURNAL OF CHEMISTRY
1973; 26 (2): 325-332
View details for Web of Science ID A1973O703000011
- QUANTITATION OF BETA-AMINOISOBUTYRIC ACID IN URINE BY MASS FRAGMENTOGRAPHY CLINICA CHIMICA ACTA 1973; 49 (3): 401-406
- SIMULTANEOUS QUANTITATION OF 10 AMINO-ACIDS IN SOIL EXTRACTS BY MASS FRAGMENTOGRAPHY ANALYTICAL BIOCHEMISTRY 1973; 55 (1): 236-244
- DETERMINATION OF PHENYLALANINE IN SERUM BY MASS FRAGMENTOGRAPHY CLINICAL BIOCHEMISTRY 1973; 6 (4): 300-306
- CHLORINATION STUDIES .2. REACTION OF AQUEOUS HYPOCHLOROUS ACID WITH ALPHA AMINO-ACIDS AND DIPEPTIDES BIOCHIMICA ET BIOPHYSICA ACTA 1973; 313 (1): 170-180
- CHLORINATION STUDIES .4. REACTION OF AQUEOUS HYPOCHLOROUS ACID WITH PYRIMIDINE AND PURINE BASES BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS 1973; 53 (4): 1195-1199