Biodegradation of polyethylene by the marine fungus Parengyodontium album.

Plastic pollution in the marine realm is a severe environmental problem. Nevertheless, plastic may also serve as a potential carbon and energy source for microbes, yet the contribution of marine microbes, especially marine fungi to plastic degradation is not well constrained. We isolated the fungus Parengyodontium album from floating plastic debris in the North Pacific Subtropical Gyre and measured fungal-mediated mineralization rates (conversion to CO2) of polyethylene (PE) by applying stable isotope probing assays with 13C-PE over 9 days of incubation. When the PE was pretreated with UV light, the biodegradation rate of the initially added PE was 0.044 %/day. Furthermore, we traced the incorporation of PE-derived 13C carbon into P. album biomass using nanoSIMS and fatty acid analysis. Despite the high mineralization rate of the UV-treated 13C-PE, incorporation of PE-derived 13C into fungal cells was minor, and 13C incorporation was not detectable for the non-treated PE. Together, our results reveal the potential of P. album to degrade PE in the marine environment and to mineralize it to CO2. However, the initial photodegradation of PE is crucial for P. album to metabolize the PE-derived carbon.

Stable carbon isotope fractionations of the hyperthermophilic crenarchaeon Metallosphaera sedula.

The stable carbon isotopic compositions of the inorganic carbon source, bulk cell material, and isoprenoid lipids of the hyperthermophilic crenarchaeon Metallosphaera sedula, which uses a 3-hydroxypropionate-like pathway for autotrophic carbon fixation, have been measured. Bulk cell material was approximately 3 per thousand enriched in 13C relative to the dissolved inorganic carbon, and 2 per thousand depleted in 13C relative to isoprenoid membrane lipids. The isotope data suggested that M. sedula uses mainly bicarbonate rather than CO(2) as inorganic carbon source, which is in accordance with a 3-hydroxypropionate-like carbon fixation pathway. To the best of our knowledge this is the first report of 13C fractionation effects of such a hyperthermophilic crenarchaeon.

All-cis hentriaconta-9,15,22-triene in microbial mats formed by the phototrophic prokaryote Chloroflexus.

All-cis hentriaconta-9,15,22-triene (I) has been isolated from Chloroflexus mats, Yellowstone National Park (USA), and identified by GC-(HR)MS analysis of I and its hydrogenated and DMDS-derivatized products and by 1H and 13C NMR spectroscopy.

Comparison of intact polar lipid with microbial community composition of vent deposits of the Rainbow and Lucky Strike hydrothermal fields.

The intact polar lipid (IPL) composition of twelve hydrothermal vent deposits from the Rainbow (RHF) and Lucky Strike hydrothermal fields (LSHF) has been investigated in order to assess its utility as a proxy for microbial community composition associated with deep-sea hydrothermal locations. Gene-based culture-independent surveys of the microbial populations of the same vent deposits have shown that microbial populations are different in the two locations and appear to be controlled by the geochemical and geological processes that drive hydrothermal circulation. Large differences in the IPL composition between these two sites are evident. In the ultramafic-hosted RHF, mainly archaeal-IPLs were identified, including those known to be produced by hyperthermophilic Euryarchaeota. More specifically, polyglycosyl derivatives of archaeol and macrocyclic archaeol indicate the presence of hyperthermophilic methanogenic archaea in the vent deposits, which are related to members of the Methanocaldococcaceae or Methanococcaceae. In contrast, bacterial IPLs dominate IPL distributions from LSHF, suggesting that bacteria are more predominant at LSHF than at RHF. Bacterial Diacyl glycerol (DAG) IPLs containing phosphocholine, phosphoethanolamine or phosphoglycerol head groups were identified at both vent fields. In some vent deposits from LSHF ornithine lipids and IPLs containing phosphoaminopentanetetrol head groups were also observed. By comparison with previously characterized bacterial communities at the sites, it is likely the DAG-IPLs observed derive from Epsilon- and Gammaproteobacteria. Variation in the relative amounts of archaeal versus bacterial IPLs appears to indicate differences in the microbial community between vent sites. Overall, IPL distributions appear to be consistent with gene-based surveys.

Autotrophy of green non-sulphur bacteria in hot spring microbial mats: biological explanations for isotopically heavy organic carbon in the geological record.

Inferences about the evidence of life recorded in organic compounds within the Earth's ancient rocks have depended on 13C contents low enough to be characteristic of biological debris produced by the well-known CO2 fixation pathway, the Calvin cycle. 'Atypically' high values have been attributed to isotopic alteration of sedimentary organic carbon by thermal metamorphism. We examined the possibility that organic carbon characterized by a relatively high 13C content could have arisen biologically from recently discovered autotrophic pathways. We focused on the green non-sulphur bacterium Chloroflexus aurantiacus that uses the 3-hydroxypropionate pathway for inorganic carbon fixation and is geologically significant as it forms modern mat communities analogous to stromatolites. Organic matter in mats constructed by Chloroflexus spp. alone had relatively high 13C contents (-14.9%) and lipids diagnostic of Chloroflexus that were also isotopically heavy (-8.9% to -18.5%). Organic matter in mats constructed by Chloroflexus in conjunction with cyanobacteria had a more typical Calvin cycle signature (-23.5%). However, lipids diagnostic of Chloroflexus were isotopically enriched (-15.1% to -24.1%) relative to lipids typical of cyanobacteria (-33.9% to -36.3%). This suggests that, in mats formed by both cyanobacteria and Chloroflexus, autotrophy must have a greater effect on Chloroflexus carbon metabolism than the photoheterotrophic consumption of cyanobacterial photosynthate. Chloroflexus cell components were also selectively preserved. Hence, Chloroflexus autotrophy and selective preservation of its products constitute one purely biological mechanism by which isotopically heavy organic carbon could have been introduced into important Precambrian geological features.

Analysis of intact tetraether lipids in archaeal cell material and sediments by high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

A method combining normal phase high performance liquid chromatography (HPLC) with positive ion atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was developed for the analysis of intact glycerol dialkyl glycerol tetraethers (GDGTs) in archaeal cell material and sediments. All GDGTs previously reported to occur in the thermophilic archaeon Sulfolobus solfataricus could be identified based on their mass spectra and retention time. Positive ion mass spectra consisted of abundant protonated molecules and fragment ions corresponding to loss of water and the glycerol moiety. In addition, two novel GDGTs representing alternative combinations of biphytanyl moieties were observed. Using this method, the tetraethers present in the thermophilic archaeon Metallosphaera sedula and two sediment samples were characterized. This rapid method will greatly contribute to the establishment of the sedimentary record of these compounds and increase our understanding of archaea and their occurrence in widely different environments.

Biosynthetic controls on the 13C contents of organic components in the photoautotrophic bacterium Chloroflexus aurantiacus.

To assess the effects related to known and proposed biosynthetic pathways on the (13)C content of lipids and storage products of the photoautotrophic bacterium Chloroflexus aurantiacus, the isotopic compositions of bulk cell material, alkyl and isoprenoid lipids, and storage products such as glycogen and polyhydroxyalkanoic acids have been investigated. The bulk cell material was 13 per thousand depleted in (13)C relative to the dissolved inorganic carbon. Evidently, inorganic carbon fixation by the main carboxylating enzymes used by C. aurantiacus, which are assumed to use bicarbonate rather than CO(2), results in a relatively small carbon isotopic fractionation compared with CO(2) fixation by the Calvin cycle. Even carbon numbered fatty acids, odd carbon numbered fatty acids, and isoprenoid lipids were 14, 15, and 17-18 per thousand depleted in (13)C relative to the carbon source, respectively. Based on the (13)C contents of alkyl and isoprenoid lipids, a 40 per thousand difference in (13)C content between the carboxyl and methyl carbon from acetyl-coenzyme A has been calculated. Both sugars and polyhydroxyalkanoic acid were enriched in (13)C relative to the alkyl and isoprenoid lipids. To the best of our knowledge this is the first report in which the stable carbon isotopic composition of a large range of biosynthetic products in a photoautotrophic organism has been investigated and interpreted based on previously proposed inorganic carbon fixation and biosynthetic pathways. Our results indicate that compound-specific stable carbon isotope analysis may provide a rapid screening tool for carbon fixation pathways.

Biosynthetic controls on the 13C contents of organic components in the photoautotrophic bacterium Chloroflexus aurantiacus.

To assess the effects related to known and proposed biosynthetic pathways on the (13)C content of lipids and storage products of the photoautotrophic bacterium Chloroflexus aurantiacus, the isotopic compositions of bulk cell material, alkyl and isoprenoid lipids, and storage products such as glycogen and polyhydroxyalkanoic acids have been investigated. The bulk cell material was 13 per thousand depleted in (13)C relative to the dissolved inorganic carbon. Evidently, inorganic carbon fixation by the main carboxylating enzymes used by C. aurantiacus, which are assumed to use bicarbonate rather than CO(2), results in a relatively small carbon isotopic fractionation compared with CO(2) fixation by the Calvin cycle. Even carbon numbered fatty acids, odd carbon numbered fatty acids, and isoprenoid lipids were 14, 15, and 17-18 per thousand depleted in (13)C relative to the carbon source, respectively. Based on the (13)C contents of alkyl and isoprenoid lipids, a 40 per thousand difference in (13)C content between the carboxyl and methyl carbon from acetyl-coenzyme A has been calculated. Both sugars and polyhydroxyalkanoic acid were enriched in (13)C relative to the alkyl and isoprenoid lipids. To the best of our knowledge this is the first report in which the stable carbon isotopic composition of a large range of biosynthetic products in a photoautotrophic organism has been investigated and interpreted based on previously proposed inorganic carbon fixation and biosynthetic pathways. Our results indicate that compound-specific stable carbon isotope analysis may provide a rapid screening tool for carbon fixation pathways.