A systematic survey for thermophilic fermentative bacteria and archaea in high temperature petroleum reservoirs

Assessing Microbial Corrosion Risk on Offshore Crude Oil Production Topsides under Conditions of Nitrate and Nitrite Treatment for Souring

Oilfield souring is a detrimental effect caused by sulfate-reducing microorganisms that reduce sulfate to sulfide during their respiration process. Nitrate or nitrite can be used to mitigate souring, but may also impart a corrosion risk. Produced fluids sampled from the topside infrastructure of two floating, production, storage, and offloading (FPSO) vessels (Platform A and Platform B) were assessed for microbial corrosion under nitrate and nitrite breakthrough conditions using microcosm tests incubated at 54 °C. Microbial community compositions on each individual FPSO were similar, while those between the two FPSO vessels differed. Platform B microbial communities responded as expected to nitrate breakthrough conditions, where nitrate-reducing activity was enhanced and sulfate reduction was inhibited. In contrast, nitrate treatments of Platform A microbial communities were not as effective in preventing sulfide production. Nitrite breakthrough conditions had the strongest sulfate reduction inhibition in samples from both platforms, but exhibited the highest pitting density. Live experimental replicates with no nitrate or nitrite additive yielded the highest general corrosion rates in the study (up to 0.48 mm/year), while nitrate- or nitrite-treated fluids revealed general corrosion rates that are considered low or moderate (<0.12 mm/year). Overall, the results of this study provide a description of nitrogen- and sulfur-based microbial activities under thermophilic conditions, and their risk for MIC that can occur along fluid processing lines on FPSO topsides that process fluids during offshore oil production operations.

Genomics and simulated laboratory studies reveal Thermococcus sp. 101C5 as a novel hyperthermophilic archaeon possessing a specialized metabolic arsenal for enhanced oil recovery

Laboratory evaluation of hyperthermophiles with the potential for Enhanced Oil Recovery (EOR) is often hampered by the difficulties in replicating the in situ growth conditions in the laboratory. In the present investigation, genome analysis was used to gain insights into the metabolic potential of a hyperthermophile to mobilize the residual oil from depleting high-temperature oil reservoirs. Here, we report the 1.9 Mb draft genome sequence of a hyperthermophilic anaerobic archaeon, Thermococcus sp. 101C5, with a GC content of 44%, isolated from a high-temperature oil reservoir of Gujarat, India. 101C5 possessed the genetic arsenal required for adaptation to harsh oil reservoir conditions, such as various heat shock proteins for thermo-adaptation, Trk potassium uptake system proteins for osmo-adaptation, and superoxide reductases against oxidative stress. Microbial Enhanced Oil Recovery (MEOR) potential of the strain was established by ascertaining the presence of genes encoding enzymes involved in the production of the metabolites such as hydrogen, bio-emulsifier, acetate, exopolysaccharide, etc. Production of these metabolites which pressurize the reservoir, emulsify the crude oil, lower the viscosity and reduce the drag, thus facilitating mobilization of the residual oil was experimentally confirmed. Also, the presence of crude oil degradative genes highlighted the ability of the strain to mobilize heavy residual oil, which was confirmed under simulated conditions in sand-pack studies. The obtained results demonstrated additional oil recoveries of 42.1% and 56.5% at 96 °C and 101 °C, respectively, by the strain 101C5, illustrating its potential for application in high-temperature oil reservoirs. To our best knowledge, this is the first report of genome analysis of any microbe assessed for its suitability for MEOR from the high-temperature oil reservoir.

Bacterial and archaeal diversity in oil fields and reservoirs and their potential role in hydrocarbon recovery and bioprospecting

Hydrocarbon is a primary source of energy in the current urbanized society. Considering the increasing demand, worldwide oil productions are declining due to maturity of oil fields and because of difficulty in discovering new oil fields to substitute the exploited ones. To meet current and future energy demands, further exploitation of oil resources is highly required. Microorganisms inhabiting in these areas exhibit highly diverse catabolic activities to degrade, transform, or accumulate various hydrocarbons. Enrichment of hydrocarbon-utilizing bacteria in oil basin is caused by continuous long duration and low molecular weight hydrocarbon microseepage which plays a very important role as an indicator for petroleum prospecting. The important microbial metabolic processes in most of the oil reservoir are sulfate reduction, fermentation, acetogenesis, methanogenesis, NO3- reduction, and Fe (III) and Mn (IV) reduction. The microorganisms residing in these sites have critical control on petroleum composition, recovery, and production methods. Physical characteristics of heavy oil are altered by microbial biotransformation and biosurfactant production. Considering oil to be one of the most vital energy resources, it is important to have a comprehensive understanding of petroleum microbiology. This manuscript reviews the recent research work referring to the diversity of bacteria in oil field and reservoir sites and their applications for enhancing oil transformation in the target reservoir and geomicrobial prospecting scope for petroleum exploration.

Metagenomic Investigation of a Low Diversity, High Salinity Offshore Oil Reservoir

Oil reservoirs can represent extreme environments for microbial life due to low water availability, high salinity, high pressure and naturally occurring radionuclides. This study investigated the microbiome of saline formation water samples from a Gulf of Mexico oil reservoir. Metagenomic analysis and associated anaerobic enrichment cultures enabled investigations into metabolic potential for microbial activity and persistence in this environment given its high salinity (4.5%) and low nutrient availability. Preliminary 16S rRNA gene amplicon sequencing revealed very low microbial diversity. Accordingly, deep shotgun sequencing resulted in nine metagenome-assembled genomes (MAGs), including members of novel lineages QPJE01 (genus level) within the Halanaerobiaceae, and BM520 (family level) within the Bacteroidales. Genomes of the nine organisms included respiratory pathways such as nitrate reduction (in Arhodomonas, Flexistipes, Geotoga and Marinobacter MAGs) and thiosulfate reduction (in Arhodomonas, Flexistipes and Geotoga MAGs). Genomic evidence for adaptation to high salinity, withstanding radioactivity, and metal acquisition was also observed in different MAGs, possibly explaining their occurrence in this extreme habitat. Other metabolic features included the potential for quorum sensing and biofilm formation, and genes for forming endospores in some cases. Understanding the microbiomes of deep biosphere environments sheds light on the capabilities of uncultivated subsurface microorganisms and their potential roles in subsurface settings, including during oil recovery operations.

Changes in the Microbial Community Diversity of Oil Exploitation

To systematically evaluate the ecological changes of an active offshore petroleum production system, the variation of microbial communities at several sites (virgin field, wellhead, storage tank) of an oil production facility in east China was investigated by sequencing the V3 to V4 regions of 16S ribosomal ribonucleic acid (rRNA) of microorganisms. In general, a decrease of microbial community richness and diversity in petroleum mining was observed, as measured by operational taxonomic unit (OTU) numbers, α (Chao1 and Shannon indices), and β (principal coordinate analysis) diversity. Microbial community structure was strongly affected by environmental factors at the phylum and genus levels. At the phylum level, virgin field and wellhead were dominated by Proteobacteria, while the storage tank had higher presence of Firmicutes (29.3-66.9%). Specifically, the wellhead displayed a lower presentence of Proteobacteria (48.6-53.4.0%) and a higher presence of Firmicutes (24.4-29.6%) than the virgin field. At the genus level, the predominant genera were Ochrobactrum and Acinetobacter in the virgin field, Lactococcus and Pseudomonas in the wellhead, and Prauseria and Bacillus in the storage tank. Our study revealed that the microbial community structure was strongly affected by the surrounding environmental factors, such as temperature, oxygen content, salinity, and pH, which could be altered because of the oil production. It was observed that the various microbiomes produced surfactants, transforming the biohazard and degrading hydro-carbon. Altering the microbiome growth condition by appropriate human intervention and taking advantage of natural microbial resources can further enhance oil recovery technology.

An appeal to magic? The discovery of a non-enzymatic metabolism and its role in the origins of life

Until recently, prebiotic precursors to metabolic pathways were not known. In parallel, chemistry achieved the synthesis of amino acids and nucleotides only in reaction sequences that do not resemble metabolic pathways, and by using condition step changes, incompatible with enzyme evolution. As a consequence, it was frequently assumed that the topological organisation of the metabolic pathway has formed in a Darwinian process. The situation changed with the discovery of a non-enzymatic glycolysis and pentose phosphate pathway. The suite of metabolism-like reactions is promoted by a metal cation, (Fe(II)), abundant in Archean sediment, and requires no condition step changes. Knowledge about metabolism-like reaction topologies has accumulated since, and supports non-enzymatic origins of gluconeogenesis, the S-adenosylmethionine pathway, the Krebs cycle, as well as CO2 fixation. It now feels that it is only a question of time until essential parts of metabolism can be replicated non-enzymatically. Here, I review the 'accidents' that led to the discovery of the non-enzymatic glycolysis, and on the example of a chemical network based on hydrogen cyanide, I provide reasoning why metabolism-like non-enzymatic reaction topologies may have been missed for a long time. Finally, I discuss that, on the basis of non-enzymatic metabolism-like networks, one can elaborate stepwise scenarios for the origin of metabolic pathways, a situation that increasingly renders the origins of metabolism a tangible problem.

Microbial dynamics in petroleum oilfields and their relationship with physiological properties of petroleum oil reservoirs

Petroleum is produced by thermal decay of buried organic material over millions of years. Petroleum oilfield ecosystems represent resource of reduced carbon which favours microbial growth. Therefore, it is obvious that many microorganisms have adapted to harsh environmental conditions of these ecosystems specifically temperature, oxygen availability and pressure. Knowledge of microorganisms present in ecosystems of petroleum oil reservoirs; their physiological and biological properties help in successful exploration of petroleum. Understanding microbiology of petroleum oilfield(s) can be used to enhance oil recovery, as microorganisms in oil reservoirs produce various metabolites viz. gases, acids, solvents, biopolymers and biosurfactants. The aim of this review is to discuss characteristics of petroleum oil reservoirs. This review also provides an updated literature on microbial ecology of these extreme ecosystems including microbial origin as well as various types of microorganisms such as methanogens; iron, nitrate and sulphate reducing bacteria, and fermentative microbes present in petroleum oilfield ecosystems.

Characterization of the microbial community structure and the physicochemical properties of produced water and seawater from the Hibernia oil production platform

Hibernia is Canada's largest offshore oil platform. Produced water is the major waste byproduct discharged into the ocean. In order to evaluate different potential disposal methods, a comprehensive study was performed to determine the impact from the discharge. Microorganisms are typically the first organisms to respond to changes in their environment. The objectives were to characterize the microbial communities and the chemical composition in the produced water and to characterize changes in the seawater bacterial community around the platform. The results from chemical, physicochemical, and microbial analyses revealed that the discharge did not have a detectable effect on the surrounding seawater. The seawater bacterial community was relatively stable, spatially. Unique microorganisms like Thermoanaerobacter were found in the produced water. Thermoanaerobacter-specific q-PCR and nested-PCR primers were designed, and both methods demonstrated that Thermoanaerobacter was present in seawater up to 1000 m from the platform. These methods could be used to track the dispersion of produced water into the surrounding ocean.

Bacteria in the injection water differently impacts the bacterial communities of production wells in high-temperature petroleum reservoirs

Water flooding is widely used for oil recovery. However, how the introduction of bacteria via water flooding affects the subsurface ecosystem remains unknown. In the present study, the distinct bacterial communities of an injection well and six adjacent production wells were revealed using denaturing gradient gel electrophoresis (DGGE) and pyrosequencing. All sequences of the variable region 3 of the 16S rRNA gene retrieved from pyrosequencing were divided into 543 operational taxonomic units (OTUs) based on 97% similarity. Approximately 13.5% of the total sequences could not be assigned to any recognized phylum. The Unifrac distance analysis showed significant differences in the bacterial community structures between the production well and injection water samples. However, highly similar bacterial structures were shown for samples obtained from the same oil-bearing strata. More than 69% of the OTUs detected in the injection water sample were absent or detected in low abundance in the production wells. However, the abundance of two OTUs reached as high as 17.5 and 26.9% in two samples of production water, although the OTUs greatly varied among all samples. Combined with the differentiated water flow rate measured through ion tracing, we speculated that the transportation of injected bacteria was impacted through the varied permeability from the injection well to each of the production wells. Whether the injected bacteria predominate the production well bacterial community might depend both on the permeability of the strata and the reservoir conditions.

Evidence for extensive gene flow and Thermotoga subpopulations in subsurface and marine environments

Oil reservoirs represent a nutrient-rich ecological niche of the deep biosphere. Although most oil reservoirs are occupied by microbial populations, when and how the microbes colonized these environments remains unanswered. To address this question, we compared 11 genomes of Thermotoga maritima-like hyperthermophilic bacteria from two environment types: subsurface oil reservoirs in the North Sea and Japan, and marine sites located in the Kuril Islands, Italy and the Azores. We complemented our genomes with Thermotoga DNA from publicly available subsurface metagenomes from North America and Australia. Our analysis revealed complex non-bifurcating evolutionary history of the isolates' genomes, suggesting high amounts of gene flow across all sampled locations, a conjecture supported by numerous recombination events. Genomes from the same type of environment tend to be more similar, and have exchanged more genes with each other than with geographically close isolates from different types of environments. Hence, Thermotoga populations of oil reservoirs do not appear isolated, a requirement of the 'burial and isolation' hypothesis, under which reservoir bacteria are descendants of the isolated communities buried with sediments that over time became oil reservoirs. Instead, our analysis supports a more complex view, where bacteria from subsurface and marine populations have been continuously migrating into the oil reservoirs and influencing their genetic composition. The Thermotoga spp. in the oil reservoirs in the North Sea and Japan probably entered the reservoirs shortly after they were formed. An Australian oil reservoir, on the other hand, was likely colonized very recently, perhaps during human reservoir development.

Life in the slow lane; biogeochemistry of biodegraded petroleum containing reservoirs and implications for energy recovery and carbon management

Our understanding of the processes underlying the formation of heavy oil has been transformed in the last decade. The process was once thought to be driven by oxygen delivered to deep petroleum reservoirs by meteoric water. This paradigm has been replaced by a view that the process is anaerobic and frequently associated with methanogenic hydrocarbon degradation. The thermal history of a reservoir exerts a fundamental control on the occurrence of biodegraded petroleum, and microbial activity is focused at the base of the oil column in the oil water transition zone, that represents a hotspot in the petroleum reservoir biome. Here we present a synthesis of new and existing microbiological, geochemical, and biogeochemical data that expands our view of the processes that regulate deep life in petroleum reservoir ecosystems and highlights interactions of a range of biotic and abiotic factors that determine whether petroleum is likely to be biodegraded in situ, with important consequences for oil exploration and production. Specifically we propose that the salinity of reservoir formation waters exerts a key control on the occurrence of biodegraded heavy oil reservoirs and introduce the concept of palaeopickling. We also evaluate the interaction between temperature and salinity to explain the occurrence of non-degraded oil in reservoirs where the temperature has not reached the 80-90°C required for palaeopasteurization. In addition we evaluate several hypotheses that might explain the occurrence of organisms conventionally considered to be aerobic, in nominally anoxic petroleum reservoir habitats. Finally we discuss the role of microbial processes for energy recovery as we make the transition from fossil fuel reliance, and how these fit within the broader socioeconomic landscape of energy futures.

Petrotoga japonica sp. nov., a thermophilic, fermentative bacterium isolated from Yabase Oilfield in Japan

A gram-negative, motile, fermentative, thermophilic bacterium, designated AR80(T), was isolated from a high-temperature oil reservoir in Yabase Oilfield in Akita, Japan. Cells were rod-shaped, motile by means of polar flagella, and formed circular, convex, white colonies. The strain grew at 40-65 °C (optimum 60 °C), 0.5-9 % (w/v) NaCl (optimum 0.5-1 %), pH 6-9 (optimum pH 7.5), and elemental sulfur or thiosulfate serves as terminal electron acceptor. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain AR80(T) belonged to the genus Petrotoga and shared approximately 94.5 % sequence similarity with the type species of this genus. The G + C content of genomic DNA was 32.4 mol% while the value of DNA-DNA hybridization between the closest relative species Petrotoga miotherma and AR80(T) was 58.1 %. The major cellular fatty acids of strain AR80(T) consisted of 18:1 w9c, 16:0, and 16:1 w9c. Based on genetic and phenotypic properties, strain AR80(T) was different with other identified Petrotoga species and represents as a novel species, for which the name Petrotoga japonica sp. nov. is proposed. The type strain is AR80(T) (=NBRC 108752(T) = KCTC 15103(T) = HUT 8122(T)).

Diversity of Microbial Communities in Production and Injection Waters of Algerian Oilfields Revealed by 16S rRNA Gene Amplicon 454 Pyrosequencing

The microorganisms inhabiting many petroleum reservoirs are multi-extremophiles capable of surviving in environments with high temperature, pressure and salinity. Their activity influences oil quality and they are an important reservoir of enzymes of industrial interest. To study these microbial assemblages and to assess any modifications that may be caused by industrial practices, the bacterial and archaeal communities in waters from four Algerian oilfields were described and compared. Three different types of samples were analyzed: production waters from flooded wells, production waters from non-flooded wells and injection waters used for flooding (water-bearing formations). Microbial communities of production and injection waters appeared to be significantly different. From a quantitative point of view, injection waters harbored roughly ten times more microbial cells than production waters. Bacteria dominated in injection waters, while Archaea dominated in production waters. Statistical analysis based on the relative abundance and bacterial community composition (BCC) revealed significant differences between production and injection waters at both OTUs0.03 and phylum level. However, no significant difference was found between production waters from flooded and non-flooded wells, suggesting that most of the microorganisms introduced by the injection waters were unable to survive in the production waters. Furthermore, a Venn diagram generated to compare the BCC of production and injection waters of one flooded well revealed only 4% of shared bacterial OTUs. Phylogenetic analysis of bacterial sequences indicated that Alpha-, Beta- and Gammaproteobacteria were the main classes in most of the water samples. Archaeal sequences were only obtained from production wells and each well had a unique archaeal community composition, mainly belonging to Methanobacteria, Methanomicrobia, Thermoprotei and Halobacteria classes. Many of the bacterial genera retrieved had already been reported as degraders of complex organic molecules and pollutants. Nevertheless, a large number of unclassified bacterial and archaeal sequences were found in the analyzed samples, indicating that subsurface waters in oilfields could harbor new and still-non-described microbial species.

Diversity of anaerobic heterotrophic thermophiles isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge

Abstract During the 'MARVEL' oceanographical cruise performed in September 1997, samples were collected from the deep-sea vents of hydrothermal sites on the Mid-Atlantic Ridge. Eighty-four thermophilic and hyperthermophilic heterotrophic microorganisms were isolated using different culture media containing cellobiose, xylan, starch, lipidic or proteic substrates. These isolates were obtained in anaerobic conditions, at 65 degrees C, 85 degrees C and 95 degrees C. Fifty of them were classified using amplified ribosomal DNA restriction analysis, random amplified polymorphic DNA and 16S rDNA sequencing. The strains classified have been assigned to the archaeal order Thermococcales and to the bacterial orders Thermotogales and Clostridiales. Variations in growth temperature and carbon sources were efficient enough to generate taxonomic diversity within enrichment cultures. Presumptive new genera and new species were isolated. Two isolates were confirmed as type strains of new species of new genera recently described: Marinitoga camini and Caloranaerobacter azorensis.

Comparison of microbial community compositions of injection and production well samples in a long-term water-flooded petroleum reservoir

Water flooding plays an important role in recovering oil from depleted petroleum reservoirs. Exactly how the microbial communities of production wells are affected by microorganisms introduced with injected water has previously not been adequately studied. Using denaturing gradient gel electrophoresis (DGGE) approach and 16S rRNA gene clone library analysis, the comparison of microbial communities is carried out between one injection water and two production waters collected from a working block of the water-flooded Gudao petroleum reservoir located in the Yellow River Delta. DGGE fingerprints showed that the similarities of the bacterial communities between the injection water and production waters were lower than between the two production waters. It was also observed that the archaeal composition among these three samples showed no significant difference. Analysis of the 16S rRNA gene clone libraries showed that the dominant groups within the injection water were Betaproteobacteria, Gammaproteobacteria and Methanomicrobia, while the dominant groups in the production waters were Gammaproteobacteria and Methanobacteria. Only 2 out of 54 bacterial operational taxonomic units (OTUs) and 5 out of 17 archaeal OTUs in the injection water were detected in the production waters, indicating that most of the microorganisms introduced by the injection water may not survive to be detected in the production waters. Additionally, there were 55.6% and 82.6% unique OTUs in the two production waters respectively, suggesting that each production well has its specific microbial composition, despite both wells being flooded with the same injection water.

Coupling hydrocarbon degradation to anaerobic respiration and mineral diagenesis: theoretical constraints

The diagenetic mineral assemblages in petroleum reservoirs control the formation fluid pH and pCO(2). Anaerobic biodegradation of petroleum is controlled by the transfer of electrons from reduced organic species to inorganic, redox sensitive, aqueous and mineral species in many cases through intermediates such as H(2) and CH(3)COO(-). The terminal electron accepting reactions induce the dissolution or precipitation of the same minerals that control the ambient pH and pCO(2) in petroleum reservoirs. In this study, we develop a model for anaerobic biodegradation of petroleum that couples the production of acetate and H(2) to 'late stage' diagenetic reactions. The model reveals that the principal terminal electron accepting process and electron donor control the type of diagenetic reaction, and that the petroleum biodegradation rate is controlled through thermodynamic restriction by the minimum DeltaG required to support a specific microbial metabolism, the fluid flux and the mineral assemblage. These relationships are illustrated by modeling coupled microbial diagenesis and biodegradation of the Gullfaks oil reservoir. The results indicate that the complete dissolution of albite by acids generated during oil biodegradation and the corresponding elevated pCO(2) seen in the Gullfaks field are best explained by methanogenic respiration coupled to hydrocarbon degradation and that the biodegradation rate is likely controlled by the pCH(4). Biodegradation of Gullfaks oil by a consortium that includes either Fe(3+)-reducing or -reducing bacteria cannot explain the observed diagenetic mineral assemblage or pCO(2). For octane, biodegradation, not water washing, was the principal agent for removal at fluid velocities <20 m Myr(-1).

Kosmotoga olearia gen. nov., sp. nov., a thermophilic, anaerobic heterotroph isolated from an oil production fluid

A novel thermophilic, heterotrophic bacterium, strain TBF 19.5.1(T), was isolated from oil production fluid at the Troll B oil platform in the North Sea. Cells of strain TBF 19.5.1(T) were non-motile rods with a sheath-like structure, or toga. The strain was Gram-negative and grew at 20-80 degrees C (optimum 65 degrees C), pH 5.5-8.0 (optimum pH 6.8) and NaCl concentrations of 10-60 g l(-1) (optimum 25-30 g l(-1)). For a member of the order Thermotogales, the novel isolate is capable of unprecedented growth at low temperatures, with an optimal doubling time of 175 min (specific growth rate 0.24 h(-1)) and a final optical density of >1.4 when grown on pyruvate at 37 degrees C. Various carbohydrates, proteinaceous compounds and pyruvate served as growth substrates. Thiosulfate, but not elemental sulfur, enhanced growth of the isolate. Sulfate also enhanced growth, but sulfide was not produced. The strain grew in the presence of up to approximately 15 % oxygen, but only if cysteine was included in the medium. Growth of the isolate was inhibited by acetate, lactate and propionate, while butanol and malate prevented growth. The major fermentation products formed on maltose were hydrogen, carbon dioxide and acetic acid, with traces of ethanol and propionic acid. The G+C content of the genomic DNA was 42.5 mol%. Phylogenetic analyses of the 16S and 23S rRNA gene sequences as well as 29 protein-coding ORFs placed the strain within the bacterial order Thermotogales. Based on the phylogenetic analyses and the possession of a variety of physiological characteristics not previously found in any species of this order, it is proposed that the strain represents a novel species of a new genus within the family Thermotogaceae, order Thermotogales. The name Kosmotoga olearia gen. nov., sp. nov. is proposed. The type strain of Kosmotoga olearia is TBF 19.5.1(T) (=DSM 21960(T) =ATCC BAA-1733(T)).

Characterisation of culture-independent and -dependent microbial communities in a high-temperature offshore chalk petroleum reservoir

Recent studies have indicated that oil reservoirs harbour diverse microbial communities. Culture-dependent and culture-independent methods were used to evaluate the microbial diversity in produced water samples of the Ekofisk oil field, a high temperature, and fractured chalk reservoir in the North Sea. DGGE analyses of 16S rRNA gene fragments were used to assess the microbial diversity of both archaeal and bacterial communities in produced water samples and enrichment cultures from 4 different wells (B-08, X-08, X-18 and X-25). Low diversity communities were found when 16S rDNA libraries of bacterial and archaeal assemblages were generated from total community DNA obtained from produced water samples and enrichment cultures. Sequence analysis of the clones indicated close matches to microbes associated with high-temperature oil reservoirs or other similar environments. Sequences were found to be similar to members of the genera Thermotoga, Caminicella, Thermoanaerobacter, Archaeoglobus, Thermococcus, and Methanobulbus. Enrichment cultures obtained from the produced water samples were dominated by sheathed rods. Sequence analyses of the cultures indicated predominance of the genera Petrotoga, Arcobacter, Archaeoglobus and Thermococcus. The communities of both produced water and enrichment cultures appeared to be dominated by thermophilic fermenters capable of reducing sulphur compounds. These results suggest that the biochemical processes in the Ekofisk chalk reservoir are similar to those observed in high-temperature sandstone reservoirs.

Geoalkalibacter subterraneus sp. nov., an anaerobic Fe(III)- and Mn(IV)-reducing bacterium from a petroleum reservoir, and emended descriptions of the family Desulfuromonadaceae and the genus Geoalkalibacter

A strictly anaerobic Fe(III)-reducing bacterium, designated strain Red1(T), was isolated from the production water of the Redwash oilfield, USA. The cells were motile rods (1-5x0.5-0.6 microm) that stained Gram-negative and possessed polar flagella. Strain Red1(T) obtained energy from the reduction of Fe(III), Mn(IV), nitrate, elemental sulfur and trimethylamine N-oxide in the presence of a wide range of electron donors, including a variety of organic acids, alcohols, biological extracts and hydrogen. Strain Red1(T) was incapable of fermentative growth. The novel isolate grew optimally at 40 degrees C (temperature range for growth, 30-50 degrees C) and at pH 7 (pH range, 6-9) with 2 % (w/v) NaCl (NaCl range, 0.1-10 %, w/v). The DNA G+C content was 52.5 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Red1(T) was a member of the order Desulfuromonadales within the class Deltaproteobacteria and most closely related to Geoalkalibacter ferrihydriticus Z-0531(T) (95.8 %), Desulfuromonas palmitatis SDBY1(T) (92.5 %) and 'Desulfuromonas michiganensis' BB1 (92.4 %). On the basis of phenotypic and phylogenetic differences, the novel strain is proposed to represent a novel species, Geoalkalibacter subterraneus sp. nov. (type strain Red1(T)=JCM 15104(T)=KCTC 5626(T)).

Microbial response to reinjection of produced water in an oil reservoir

The microbial response to produced water reinjection (PWRI) in a North Sea oil field was investigated by a combination of cultivation and culture-independent molecular phylogenetic techniques. Special emphasise was put on the relationship between sulphate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB), and results were used to evaluate the possibility of nitrate treatment as a souring management tool during PWRI. Samples were collected by reversing the flow of the injection water, which provided samples from around the injection area. The backflowed samples were compared to produced water from the same platform and to backflowed samples from a biocide-treated seawater injector, which was the previous injection water treatment of the PWRI well. Results showed that reinjection of produced water promoted growth of thermophilic SRB. Thermophilic fatty acid oxidising NRB and potential nitrate-reducing sulphide-oxidising bacteria were also found. The finding of thermophilic NRB makes nitrate treatment during PWRI possible, although higher nitrate concentration will be necessary to compensate for the increased SRB activity.

Molecular phylogenetic diversity of the microbial community associated with a high-temperature petroleum reservoir at an offshore oilfield

The microbial community and its diversity in production water from a high-temperature, water-flooded petroleum reservoir of an offshore oilfield in China were characterized by 16S rRNA gene sequence analysis. The bacterial and archaeal 16S rRNA gene clone libraries were constructed from the community DNA and, using sequence analysis, 388 bacterial and 220 archaeal randomly selected clones were clustered with 60 and 28 phylotypes, respectively. The results showed that the 16S rRNA genes of bacterial clones belonged to the divisions Firmicutes, Thermotogae, Nitrospirae and Proteobacteria, whereas the archaeal library was dominated by methanogen-like rRNA genes (Methanothermobacter, Methanobacter, Methanobrevibacter and Methanococcus), with a lower percentage of clones belonging to Thermoprotei. Thermophilic microorganisms were found in the production water, as well as mesophilic microorganisms such as Pseudomonas and Acinetobacter-like clones. The thermophilic microorganisms may be common inhabitants of geothermally heated specialized subsurface environments, which have been isolated previously from a number of high-temperature petroleum reservoirs worldwide. The mesophilic microorganisms were probably introduced into the reservoir as it was being exploited. The results of this work provide further insight into the composition of microbial communities of high-temperature petroleum reservoirs at offshore oilfields.

Molecular analysis of the bacterial community in a continental high-temperature and water-flooded petroleum reservoir

Water from a continental high-temperature, long-term water-flooded petroleum reservoir in Huabei Oilfield in China was analysed for its bacterial community and diversity. The bacteria were characterized by their 16S rRNA genes. A 16S rRNA gene clone library was constructed from the community DNA, and using restriction fragment length polymorphism analysis, 337 randomly selected clones were clustered with 74 operational taxonomic units. Sequencing and phylogenetic analyses showed that the screened clones were affiliated with Gammaproteobacteria (85.7%), Thermotogales (6.8%), Epsilonproteobacteria (2.4%), low-G+C Gram-positive (2.1%), high-G+C Gram-positive, Betaproteobacteria and Nitrospira (each <1.0%). Thermopilic bacteria were found in the high-temperature water from the flooded petroleum reservoir, as well as mesophilic bacteria such as Pseudomonas-like clones. The mesophilic bacteria were probably introduced into the reservoir as it was being exploited. This work provides significant information on the structure of bacterial communities in high-temperature, long-term water-flooded petroleum reservoirs.

Effects of nitrate treatment on a mixed species, oil field microbial biofilm

Biofilms of bacteria, indigenous to oil field produced water, were grown in square section, glass capillary flow cells at 45 degrees C. Initially, in situ image analysis microscopy revealed predominantly coccoid bacteria (length-to-width ratio measurements (l (c):w (c)) of bacterial cells gave a mean value of 1.1), while chemical measurements confirmed sulphate reduction and sulphide production. After nitrate ion addition at 100 and 80 mg/l, in the two repeat experiments respectively, the dominance of rod-shaped bacteria (mean l (c):w (c) = 2.8) was observed. This coincided with the occurrence of nitrate reduction in the treated flow cells. Beneficially, no significant increase in biofilm cover was observed after the addition of nitrate. The dominant culturable nitrate-reducing bacterium was Marinobacter aquaeolei. The l (c):w (c) ratio measured here concurs with previously reported cell dimensions for this organism. Several Marinobacter strains were also isolated from different oil fields in the North Sea where nitrate treatment has been applied to successfully treat reservoir souring, implying that this genus may play an important role in nitrate treatment.

Mahella australiensis gen. nov., sp. nov., a moderately thermophilic anaerobic bacterium isolated from an Australian oil well

A novel Gram-positive, anaerobic and moderately thermophilic bacterium, strain 50-1 BON(T), was isolated from an Australian terrestrial oil reservoir. Cells were spore-forming straight rods, motile by peritrichous flagella. The optimum growth conditions were 50 degrees C, pH 7.5 and 0.1 % NaCl. Strain 50-1 BON(T) fermented arabinose, cellobiose, fructose, galactose, glucose, mannose, sucrose, xylose and yeast extract. Glucose was fermented mainly into lactate, formate, hydrogen and CO(2). The major end product of pyruvate fermentation was acetate together with H(2) and CO(2). Thiosulfate, sulfate, elemental sulfur and nitrate were not used as terminal electron acceptors. The DNA G+C content was 55.5 mol%. The closest phylogenetic relative of strain 50-1 BON(T) was Thermoanaerobacterium thermosulfurigenes (16S rRNA gene sequence similarity of 85.7 %). As strain 50-1 BON(T) was physiologically and phylogenetically different from members of the order 'Thermoanaerobacteriales', it is proposed that strain 50-1 BON(T) (=DSM 15567(T)=CIP 107919(T)) be classified as the type strain of a novel species of a new genus, Mahella australiensis gen. nov., sp. nov.

Isolation from oil reservoirs of novel thermophilic anaerobes phylogenetically related to Thermoanaerobacter subterraneus: reassignment of T. subterraneus, Thermoanaerobacter yonseiensis, Thermoanaerobacter tengcongensis and Carboxydibrachium pacificum to Caldanaerobacter subterraneus gen. nov., sp. nov., comb. nov. as four novel subspecies

Novel thermophilic, anaerobic, Gram-positive, rod-shaped bacteria, strains SL9 and OCA1, were isolated from oilfields in France and Australia, respectively. Both strains, together with Thermoanaerobacter yonseiensis KB-1(T) (=DSM 13777(T)), Thermoanaerobacter tengcongensis MB4(T) (=DSM 15242(T)) and Carboxydibrachium pacificum JM(T) (=DSM 12653(T)), possessed genomic (DNA-DNA hybridization studies) and phylogenetic similarities with Thermoanaerobacter subterraneus SEBR 7858(T) (=DSM 13054(T)), which was isolated recently from an oilfield reservoir in south-west France. Marked phenotypic differences exist between the three oilfield isolates (T. subterraneus, strain OCA1 and strain SL9): they include temperature range for growth and substrates used. Differences were also observed in the DNA G+C contents of all organisms. Similarly to T. subterraneus, strains SL9 and OCA1, and also T. yonseiensis, T. tengcongensis and Carboxydibrachium pacificum, produced acetate and L-alanine as major end products of glucose metabolism [0.8-1.0 mol L-alanine produced (mol glucose consumed)(-1)] and reduced thiosulfate, but not sulfate, to sulfide. Because of these significant metabolic and phylogenetic differences between the oilfield isolates (T. subterraneus, strain OCA1 and strain SL9), T. yonseiensis, T. tengcongensis and Carboxydibrachium pacificum and other Thermoanaerobacter species, it is proposed to reassign them as a novel genus and species, Caldanaerobacter subterraneus gen. nov., sp. nov., comb. nov., with the creation of four novel subspecies, Caldanaerobacter subterraneus subsp. subterraneus subsp. nov., comb. nov., Caldanaerobacter subterraneus subsp. yonseiensis subsp. nov., comb. nov., Caldanaerobacter subterraneus subsp. tengcongensis subsp. nov., comb. nov. and Caldanaerobacter subterraneus subsp. pacificus subsp. nov., comb. nov.

Petrobacter succinatimandens gen. nov., sp. nov., a moderately thermophilic, nitrate-reducing bacterium isolated from an Australian oil well

A novel Gram-negative, aerobic and moderately thermophilic bacterium, strain 4BONT, was isolated from a non-water-flooded Australian terrestrial oil reservoir. Cells were non-spore-forming straight rods, which were motile by means of a polar flagellum. The optimum growth conditions were 55 °C, pH 6·9 and 0·5 % NaCl. Strain 4BONT was oxidase- and catalase-positive; it grew on fumarate, pyruvate, succinate, formate, ethanol and yeast extract in the presence of oxygen or nitrate as terminal electron acceptor. Nitrate was reduced to nitrous oxide. The DNA G+C content of the strain was 58·6 mol%. The closest phylogenetic relative of strain 4BONT was Hydrogenophilus thermoluteolus (similarity of 91·8 %), of the β-Proteobacteria. As strain 4BONT is physiologically and phylogenetically different from H. thermoluteolus, it is proposed that it be assigned to a novel species of a novel genus, Petrobacter succinatimandens gen. nov., sp. nov. The type strain is 4BONT (=DSM 15512T=CIP 107790T).

Crude-oil-degrading thermophilic bacterium isolated from an oil field

Thermophilic bacterium strain C2, which has the ability to transform crude oils, was isolated from the reservoir of the Shengli oil field in East China. The Gram-negative, rod-shaped, nonmotile cells were grown at a high temperature, up to 83 °C, in the neutral to alkaline pH range. Depending on the culture conditions, the organism occurred as single rods or as filamentous aggregates. Strain C2 was grown chemoorganotrophically and produced metabolites, such as volatile fatty acids, 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl)ester, dibutyl phthalate, and di-n-octyl phthalate. It could metabolize different organic substrates (acetate, D-glucose, fructose, glycerol, maltose, pyruvate, starch, sucrose, xylose, hexadecane). The G+C content (68 mol%) and the 16S rRNA sequence of strain C2 indicated that the isolate belonged to the genus Thermus. The strain affected different crude oils and changed their physical and chemical properties. The biochemical interactions between crude oils and strain C2 follow distinct trends characterized by a group of chemical markers (saturates, aromatics, resins, asphaltenes). Those trends show an increase in saturates and a decrease in aromatics, resins, and asphaltenes. The bioconversion of crude oils leads to an enrichment in lighter hydrocarbons and an overall redistribution of these hydrocarbons.Key words: thermophile, metabolite, crude oil, degradation, conversion.

Petrotoga mexicana sp. nov., a novel thermophilic, anaerobic and xylanolytic bacterium isolated from an oil-producing well in the Gulf of Mexico

A novel anaerobic, thermophilic, xylanolytic, motile rod-shaped bacterium with a sheath-like outer structure (toga) was isolated from a Mexican oil well in the Gulf of Mexico. Strain MET12T was a Gram-negative bacterium, reducing elemental sulfur, thiosulfate and sulfite to hydrogen sulfide. Its optimum growth conditions were 55 °C, pH 6·6, 3 % NaCl and 0·15 % MgCl2.6H2O. The DNA G+C content was 36·1 mol%. Phylogenetically, strain MET12T was related to members of genus Petrotoga, with similarities to Petrotoga mobilis, Petrotoga sibirica, Petrotoga miotherma and Petrotoga olearia varying from 97·6 to 98·8 %. However DNA–DNA relatedness values between these species and strain MET12T were lower than 70 %. As strain MET12T (=DSM 14811T=CIP 107371T) was genomically and phenotypically different from existing Petrotoga species, it is proposed as the type strain of a novel species, Petrotoga mexicana sp. nov.

Radioisotopic, culture-based, and oligonucleotide microchip analyses of thermophilic microbial communities in a continental high-temperature petroleum reservoir

Activity measurements by radioisotopic methods and cultural and molecular approaches were used in parallel to investigate the microbial biodiversity and its physiological potential in formation waters of the Samotlor high-temperature oil reservoir (Western Siberia, Russia). Sulfate reduction with rates not exceeding 20 nmol of H(2)S liter(-1) day(-1) occurred at 60 and 80 degrees C. In upper horizons (AB, A, and B), methanogenesis (lithotrophic and/or acetoclastic) was detected only in wells in which sulfate reduction did not occur. In some of the wells from deeper (J) horizons, high-temperature sulfate reduction and methanogenesis occurred simultaneously, the rate of lithotrophic methanogenesis exceeding 80 nmol of CH(4) liter(-1) day(-1). Enrichment cultures indicated the presence of diverse physiological groups representing aerobic and anaerobic thermophiles and hyperthermophiles; fermentative organotrophs were predominant. Phylogenetic analyses of 15 isolates identified representatives of the genera Thermotoga, Thermoanaerobacter, Geobacillus, Petrotoga, Thermosipho, and Thermococcus, the latter four being represented by new species. Except for Thermosipho, the isolates were members of genera recovered earlier from similar habitats. DNA obtained from three samples was hybridized with a set of oligonucleotide probes targeting selected microbial groups encompassing key genera of thermophilic bacteria and archaea. Oligonucleotide microchip analyses confirmed the cultural data but also revealed the presence of several groups of microorganisms that escaped cultivation, among them representatives of the Aquificales/Desulfurobacterium-Thermovibrio cluster and of the genera Desulfurococcus and Thermus, up to now unknown in this habitat. The unexpected presence of these organisms suggests that their distribution may be much wider than suspected.

The microbiology of hydrocarbon degradation in subsurface petroleum reservoirs: perspectives and prospects

The majority of the Earth's petroleum resource is partly biodegraded. This is of considerable practical significance and can limit economic exploitation of petroleum reserves and lead to problems during petroleum production. Knowledge of the microorganisms present in petroleum reservoirs, their physiological properties and the biochemical potential for hydrocarbon degradation benefits successful petroleum exploration. Anaerobic conditions prevail in petroleum reservoirs and biological hydrocarbon degradation is apparently inhibited at temperatures above 80-90 degrees C. We summarise available knowledge and conjecture on the dominant biological processes active during subsurface petroleum biodegradation.

Biodegradation of oil in uplifted basins prevented by deep-burial sterilization

Biodegradation of crude oil by bacterial activity--which has occurred in the majority of the Earth's oil reserves--is known to reduce greatly the quality of petroleum in reservoirs. For economically successful prospecting for oil, it is therefore important to understand the processes and conditions in geological formations that lead to oil biodegradation. Although recent studies speculate that bacterial activity can potentially occur up to temperatures as high as 150 degrees C (refs 3, 4), it is generally accepted that effective petroleum biodegradation over geological timescales generally occurs in reservoirs with temperatures below 80 degrees C (ref. 2). This appears, however, to be at odds with the observation that non-degraded oils can still be found in reservoirs below this temperature. Here we compile data regarding the extent of oil biodegradation in several oil reservoirs, and find that the extensive occurrence of non-biodegraded oil in shallow, cool basins is restricted to those that have been uplifted from deeper, hotter regions of the Earth. We suggest that these petroleum reservoirs were sterilized by heating to a temperature around 80-90 degrees C during deep burial, inactivating hydrocarbon-degrading organisms that occur in the deep biosphere. Even when such reservoirs are subsequently uplifted to much cooler regions and filled with oil, degradation does not occur, implying that the sterilized sediments are not recolonized by hydrocarbon-degrading bacteria.

Diversity among three novel groups of hyperthermophilic deep-sea Thermococcus species from three sites in the northeastern Pacific Ocean

Eight new strains of deep-sea hyperthermophilic sulfur reducers were isolated from hydrothermal vent fields at 9 degrees 50'N East Pacific Rise (EPR) and at the Cleft and CoAxial segments along the Juan de Fuca Ridge (JdFR). 16S rRNA gene sequence analysis showed that each strain belongs to the genus Thermococcus. Restriction fragment length polymorphism patterns of the 16S/23S rRNA intergenic spacer region revealed that these isolates fell into three groups: those from the EPR, those from fluid and rock sources on the JdFR, and those isolated from Paralvinella spp. polychaete vent worms from the JdFR. The optimum-temperature specific growth rates and the temperature ranges for growth were significantly higher and broader for those strains isolated from worms relative to those isolated from low-temperature diffuse hydrothermal fluids. Furthermore, the worm-derived isolates generally produced a larger array of proteases and amylases based on zymogram analyses. The zymogram patterns also changed with growth temperature suggesting that these organisms alter their lytic protein suites in response to changes in temperature. This study suggests that there is significant phenotypic diversity in Thermococcus that is not apparent from their highly conserved 16S rRNA nucleotide sequences.

Culture-dependent and culture-independent characterization of microbial assemblages associated with high-temperature petroleum reservoirs

Recent investigations of oil reservoirs in a variety of locales have indicated that these habitats may harbor active thermophilic prokaryotic assemblages. In this study, we used both molecular and culture-based methods to characterize prokaryotic consortia associated with high-temperature, sulfur-rich oil reservoirs in California. Enrichment cultures designed for anaerobic thermophiles, both autotrophic and heterotrophic, were successful at temperatures ranging from 60 to 90 degrees C. Heterotrophic enrichments from all sites yielded sheathed rods (Thermotogales), pleomorphic rods resembling Thermoanaerobacter, and Thermococcus-like isolates. The predominant autotrophic microorganisms recovered from inorganic enrichments using H(2), acetate, and CO(2) as energy and carbon sources were methanogens, including isolates closely related to Methanobacterium, Methanococcus, and Methanoculleus species. Two 16S rRNA gene (rDNA) libraries were generated from total community DNA collected from production wellheads, using either archaeal or universal oligonucleotide primer sets. Sequence analysis of the universal library indicated that a large percentage of clones were highly similar to known bacterial and archaeal isolates recovered from similar habitats. Represented genera in rDNA clone libraries included Thermoanaerobacter, Thermococcus, Desulfothiovibrio, Aminobacterium, Acidaminococcus, Pseudomonas, Halomonas, Acinetobacter, Sphingomonas, Methylobacterium, and Desulfomicrobium. The archaeal library was dominated by methanogen-like rDNAs, with a lower percentage of clones belonging to the Thermococcales. Our results strongly support the hypothesis that sulfur-utilizing and methane-producing thermophilic microorganisms have a widespread distribution in oil reservoirs and the potential to actively participate in the biogeochemical transformation of carbon, hydrogen, and sulfur in situ.

Distribution and physiological characteristics of hyperthermophiles in the Kubiki oil reservoir in Niigata, Japan

The distribution of culturable hyperthermophiles was studied in relation to environmental conditions in the Kubiki oil reservoir in Japan, where the temperature was between 50 and 58 degrees C. Dominant hyperthermophilic cocci and rods were isolated and shown to belong to the genera Thermococcus and Thermotoga, respectively, by 16S rDNA analyses. Using the most-probable-number method, we found that hyperthermophilic cocci were widely distributed in several unconnected fault blocks in the Kubiki oil reservoir. In 1996 to 1997, their populations in the production waters from oil wells were 9.2 x 10(3) to 4.6 x 10(4) cells/ml, or 10 to 42% of total cocci. On the other hand, hyperthermophilic rods were found in only one fault block of the reservoir with populations less than 10 cells/ml. Dominant Thermococcus and Thermotoga spp. grew at reservoir temperatures and utilized amino acids and sugars, respectively, as sole carbon sources. While organic carbon was plentiful in the environment, these hyperthermophiles were unable to grow in the formation water due to lack of essential nutrients. Concentrations of some organic and inorganic substances differed among fault blocks, indicating that the movement of formation water between fault blocks was restricted. This finding suggests that the supply of nutrients via fluid current is limited in this subterranean environment and that the organisms are starved in the oil reservoir. Under starved conditions at 50 degrees C, culturable cells of Thermococcus sp. remained around the initial cell density for about 200 days, while those of Thermotoga sp. decreased exponentially to 0. 01% of the initial cell density after incubation for the same period. The difference in survivability between these two hyperthermophiles seems to reflect their populations in the fault blocks. These results indicate that hyperthermophilic cocci and rods adapt to the subterranean environment of the Kubiki oil reservoir by developing an ability to survive under starved conditions.

The evolution of aging: a new approach to an old problem of biology

Most gerontologists believe aging did not evolve, is accidental, and is unrelated to development. The opposite viewpoint is most likely correct. Genetic drift occurs in finite populations and leads to homozygosity in multiple-alleled traits. Episodic selection events will alter random drift towards homozygosity in alleles that increase fitness with respect to the selection event. Aging increases population turnover, which accelerates the benefit of genetic drift. This advantage of aging led to the evolution of aging systems (ASs). Periodic predation was the most prevalent episodic selection pressure in evolution. Effective defenses to predation that allow exceptionally long lifespans to evolve are shells, extreme intelligence, isolation, and flight. Without episodic predation, aging provides no advantage and aging systems will be deactivated to increase reproductive potential in unrestricted environments. The periodic advantage of aging led to the periodic evolution of aging systems. Newer aging systems co-opted and added to prior aging systems. Aging organisms should have one dominant, aging system that co-opts vestiges of earlier-evolved systems as well as vestiges of prior systems. In human evolution, aging systems chronologically emerged as follows: telomere shortening, mitochondrial aging, mutation accumulation, senescent gene expression (AS#4), targeted somatic tissue apoptotic-atrophy (AS#5), and female reproductive tissue apoptotic-atrophy (AS#6). During famine or drought, to avoid extinction, reproduction is curtailed and aging is slowed or somewhat reversed to postpone or reverse reproductive senescence. AS#4-AS#6 are gradual and reversible aging systems. The life-extending/rejuvenating effects of caloric restriction support the idea of aging reversibility. Development and aging are timed by the gradual loss of cytosine methylation in the genome. Methylated cytosines (5mC) inhibit gene transcription, and deoxyribonucleic acid (DNA) cleavage by restriction enzymes. Cleavage inhibition prevents apoptosis, which requires DNA fragmentation. Free radicals catalyze the demethylation of 5mC while antioxidants catalyze the remethylation of cytosine by altering the activity of DNA methyltransferases. Hormones act as either surrogate free radicals by stimulating the cyclic adenosine monophosphate (cAMP) pathway or as surrogate antioxidants through cyclic guanosine monophosphate (cGMP) pathway stimulation. Access to DNA containing 5mC inhibited developmental and aging genes and restriction sites is allowed by DNA helicase strand separation. Tightly wound DNA does not allow this access. The DNA helicase generates free radicals during strand separation; hormones either amplify or counteract this effect. Caloric restriction slows or reverses the aging process by increasing melatonin levels, which suppresses reproductive and free radical hormones, while increasing antioxidant hormone levels. Cell apoptosis during CR leads to somatic wasting and a release of DNA, which increases bioavailable cGMP. The rapid aging diseases of progeria, the three diseases: (xeroderma pigmentosum (XP), Cockayne syndrome(CS), and ataxia telangiectasia (AT)), and Werner's syndrome are related to or caused by defects in three separate DNA helicases. The rapid aging diseases caused by mitochondrial malfunctions mirror those seen in XP, CS, and AT. Comparing these diseases allows for assignment of the different symptoms of aging to their respective aging systems. Follicle-stimulating hormone (FSH) demethylates the genes of AS#4, luteinizing hormone (LH) of AS#5, and estrogen of AS#6 while cortisol may act cooperatively with FSH and LH, and 5-alpha dihydrotestosterone (DHT) with FSH in these role. The Werner's DNA helicase links timing of the age of puberty, menopause, and maximum lifespan in one mechanism. Telomerase is under hormonal control. Most cancers likely result from malfunctions in the programmed apoptosis of AS#5 and AS#6. The Hayflick limit is reached primarily through loss of cytosine methylation of genes that inhibit replication. Men suffer the diseases of AS#4 at a higher rate than women who suffer from AS#5 more often. Adult mammal cloning suggests aging-related cellular demethylation, and thus aging, is reversible. This theory suggests that the protective effect of smoking and ibuprofen for Alzheimer's disease is caused through LH suppression.