Metabolic differences inBacillus stearothermophilus grown at 55°C and 37°C

Summary Bacillus stearothermophilus was adapted to grow at 55°C and 37°C in a complex medium with almost equivalent yields in cell mass. In both temperature ranges the maximum specific growth rates (μ_max) were identical. Cellular extracts of this bacterium showed remarkable differences in the activity levels of several enzymes, depending on the respective growth temperature. High activities of glyceraldehyde-3-phosphate dehydrogenase and alcohol dehydrogenase were observed in bacteria from thermophilic cultures (55°C) and the respiratory quotient exceeded 1.0. Under anaerobic conditions at 55°C μ_max was the same as in aerobic cultures. No alcohol dehydrogenase was detected in cells from mesophilic cultures (37°C), however, and the level of glyceraldehyde-3-phosphate dehydrogenase was also extremely low under mesophilic conditions. Succinate dehydrogenase and isocitrate dehydrogenase activity appeared to be higher in bacteria grown at 37°C; the resspiratory quotient was always lower than 1.0. At 37°C, acetoin formation was observed regularly, a fermentation product which was never detected in 55°C-cultures. Under anaerobic conditions at 37°C a very low growth rate was found. When adapted to grow at 37°C or 55°C,B. stearothermophilus is apparently able to use different catabolic systems.     

Phospholipid metabolism in Mycobacterium smegmatis ATCC 607 grown at 37° C and 27° C

The rate of synthesis and degradation of phospholipids in Mycobacterium smegmatis ATCC 607, grown at 27° C and 37° C was studied by incorporation of ³²P into phospholipids and chase of radioactivity of the pulse-labelled phospholipids. A relatively low rate of synthesis and degradation of phospholipids in cells growth at 27° C was observed as compared to those grown at 37° C. Phosphatidylethanolamine (PE) had the maximum turnover at 37° C. However, at 27° C, cardiolipin (CL) showed a turnover rate higher than PE. Phosphatidylinositol mannosides (PIMs) were metabolically more active at 37° C than at 27° C. The differences in metabolic activity of the phospholipids at the two temperatures have been discussed.     

Adaptation of Methanogenic Communities to the Cofermentation of Cattle Excreta and Olive Mill Wastes at 37°C and 55°C

The acclimatization of methanogens to two-phase olive mill wastes (TPOMW) was investigated in pilot fermenters started up with cattle excreta (37°C) and after changing their feed to excreta plus TPOMW (37°C or 55°C) or TPOMW alone (37°C) until a steady state was reached (28 days). Methanogenic diversity was screened using a phylogenetic microarray (AnaeroChip), and positive targets were quantified by real-time PCR. Results revealed high phylogenetic richness, with representatives of three out of the four taxonomic orders found in digesters. Methanosarcina dominated in the starting excreta (>96% of total 16S rRNA gene copies; over 45 times more abundant than any other methanogen) at high acetate (0.21 g liter⁻¹) and ammonia N concentrations (1.3 g liter⁻¹). Codigestion at 37°C induced a 6-fold increase of Methanosarcina numbers, correlated with CH₄ production (r_Pearson = 0.94; P = 0.02). At 55°C, the rise in temperature and H₂ partial pressure induced a burst of Methanobacterium, Methanoculleus, Methanothermobacter, and a group of uncultured archaea. The digestion of excreta alone resulted in low but constant biogas production despite certain oscillations in the methanogenic biomass. Unsuccessful digestion of TPOMW alone was attributed to high Cu levels inducing inhibition of methanogenic activity. In conclusion, the versatile Methanosarcina immediately adapted to the shift from excreta to excreta plus TPOMW and was responsible for the stimulated CH₄ production at 37°C. Higher temperatures (55°C) fostered methanogenic diversity by promoting some H₂ scavengers while yielding the highest CH₄ production. Further testing is needed to find out whether there is a link between increased methanogenic diversity and reactor productivity.Turning residues into energy is a societal and scientific priority due to climate change, fossil fuel exhaustion, and waste accumulation. In 2006, in Europe (EU27), less than 3% of electricity production came from biomass and wastes (11). Biogas plants, which anaerobically treat organic wastes to produce energy, are increasingly promoted in Europe, but their distribution is highly biased (35). While thousands of full- and farm-scale biogas plants are spread over central and northern Europe, anaerobic digestion technology in Mediterranean countries—Portugal, Spain, Italy, Greece, and Turkey—is in its early stages (35). These nations and other circum-Mediterranean countries lead in the production of olive oil and thus in olive mill wastes and wastewaters, which have a huge biogas production potential due to their lipid composition (1). Spain alone generates one-third of the world''s oil production and millions of tons of two-phase olive mill wastes (TPOMW) per year. TPOMW are mostly burned or composted (28), hence releasing methane into the atmosphere. This compels a change in strategy: methane production from TPOMW should be optimized in engineered environments and transformed into energy.TPOMW is a humid residue containing the olive pulp and stone. Its anaerobic digestibility is hampered by its low pH, low ammonia N, and high content in antimicrobial substances (1). However, it has been successfully fermented under laboratory conditions by supplementing it with nutrients and increasing the reactor organic loading rate stepwise (2) or by codigesting it with residues with a high buffering capacity, e.g., cattle excreta (17). These approaches seem to facilitate the adaptation of the methane-producing anaerobic community to the environmental conditions that TPOMW impose.Methanogenic archaea—microbes clustered within five orders of the Euryarchaeota—constitute the last step in the trophic chain of decomposers degrading organic matter in oxygen-free environments (36). Methanogenesis is often the rate-limiting step of anaerobic digestion of organic wastes (3) due to the fast duplication times of bacteria, which generate all substrates for the slow-growing methane-producing archaea. It is also the most sensitive step in processing imbalances (4), likely due to the lack of functional redundancy among methanogens (8). High concentrations of volatile fatty acids, salts, ammonia, and heavy metals can be inhibitory for methanogens (5, 22) and are the most common reasons for reactor failure (3). Our objective was to understand the adaptation of methanogenic communities to TPOMW. We investigated methanogenic diversity and abundance in pilot digesters fed with cattle excreta and after changing their feed to TPOMW or TPOMW plus excreta. We expected that mixing both residues would allow a faster adaptation and more efficient performance of the methanogenic communities in digesting TPOMW. The cofermentation was evaluated at 37°C and 55°C. During an acclimatization period of 28 days, we screened the methanogenic diversity using an in-house-devised phylogenetic microarray, the AnaeroChip (13), and quantified dominant genera by real-time quantitative PCR (qPCR). We have taken primers from the literature, and we present four new sets of genus-specific primers and SYBR green I-optimized assays for quantifying methanogens in anaerobic environments.     

Changes in productivity and carbon storage of grasslands in China under future global warming scenarios of 1.5°C and 2°C

Aims The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming.     

The growth of dermatophytes at 4° C and 37° C; The relation of this character to others

Summary The ability of the generaEpidermophyton, Microsporon andTrichopyton to grow on some media at 4° C and 37° C was studied. It has been shown that specific differences exist among these fungi in the capability or rapidity of the growth at extreme temperatures.There is high positive correlation among perfect state production, isolation from the soil and growth at 4° C (group of characters A) and between pathogenicity and growth at 37° C (group of characters B). Between the groups A and B of characters exists a slighter negative correlation. Some prognosis about the five characters by certain species of dermatophytes may be given.     

Microbial metabolism in ice and brine at -5°C

Metabolic activity, but not growth, has been observed in ice at temperatures from -5°C to -32°C. To improve understanding of metabolism in ice, we simultaneously examined various aspects of metabolism ((14) C-acetate utilization, macromolecule syntheses and viability via reduction of CTC) of the glacial isolates Sporosarcina sp. B5 and Chryseobacterium sp. V3519-10 during incubation in nutrient-rich ice and brine at -5°C for 50 days. Measured rates of acetate utilization and macromolecule syntheses were high in the first 20 days suggesting adjustment to the lower temperatures and higher salt concentrations of both the liquid vein network in the ice and the brine. Following this adjustment, reproductive growth of both organisms was evident in brine, and suggested for Sporosarcina sp. B5 in ice by increases in cell numbers and biomass. Chryseobacterium sp. V3519-10 cells incubated in ice remained active. These data indicate that neither low temperature nor high salt concentrations prohibit growth in ice, but some other aspect of living within ice slows growth to within the detection limits of current methodologies. These results imply that microbial growth is plausible in natural ice systems with comparable temperatures and sufficient nutrients, such as debris-rich basal ices of glaciers and ice masses.     

Dark-recovery of Gamma- and UV-irradiated Saccharomyces carlsbergensis at 4° C

Experiments were carried out to find the effect of dark-holding in distilled water at 4° C on recovery of Gamma- and UV-irradiated cells of a haploid strain ofSaccharomyces carlsbergensis. It was found that there was an appreciable increase in survival of the irradiated cells following 4 to 24 hours' holding while no increase in the number of control cells was observed following similar treatment. It is suggested that some common type of damage induced by both Gamma- and UV-radiations inS. carlsbergensis may be repaired efficiently under metabolic conditions associated with growth at 4° C in distilled water.     

Thyroliberin is rapidly transferred to the nucleus of GH3 pituitary cells at both 4°C and 37°C

The time-course of thyroliberin transfer to the nucleus of GH3/B6 rat pituitary prolactin cells was studied by both autoradiography and cell fractionation of intact cells exposed to [³H]thyroliberin at 4°C or 37°C. It was previously shown that thyroliberin is not degraded in these conditions. It is found by autoradiography that [³H]-thyroliberin is transferred to the nucleus of GH3/B6 cells within 5 min at least at both 37° C and 4°C. Consistent results are obtained by fractionation of cells exposed to [³H]thyroliberin at 37°C. However after binding at 4°C 50% of the cell radioactivity is extractible by glutaraldehyde and after fractionation the isolated nuclei retain only 1–1.5% of the cell radioactivity. This suggests the existence of both tightly bound and loosely bound internalized thyroliberin molecules.     

Comparative proteomic analysis reveals differentially expressed proteins in Caenorhabditis elegans pgl-1 mutants grown at 20°C and 25°C

PGL-1 is an RNA-binding protein component of germ granules and essential for fertility in Caenorhabditis elegans. To clarify the molecular function of PGL-1, we performed comparative proteomic analysis using 2-D DIGE and LC-MS/MS. Five groups of synchronized adult hermaphrodites were analyzed: (1) wild-type N2 grown at 20°C, (2) pgl-1(bn101) mutants grown at 20°C, (3) pgl-1(bn101) mutants grown at 20°C then upshifted to 25°C after the L1 stage, (4) pgl-1(ct131) mutants grown at 20°C, and (5) pgl-1(ct131) mutants grown at 20°C then upshifted to 25°C after the L1 stage. The five groups were divided into two experimental sets for 2-D DIGE: set A included N2 and pgl-1(bn101) mutants, and set B included N2 and pgl-1(ct131) mutants. Dunnett's test indicated 90 and 100 specific spots, respectively, with significantly different expression levels from the rest of the experimental set (q≤0.1). Among them, 69 and 58 spots, respectively, were analyzed by LC-MS/MS. Finally, we identified 19 proteins from 24 specific spots common to both the experimental sets. RNAi analysis indicated that decreased eef-1G expression is strongly associated with the temperature-sensitive sterile phenotype of pgl-1. Our results suggest that PGL-1 is closely involved in translational processes during C. elegans germline development.     

Sarcoplasmic reticulum and excitation-contraction coupling at 20 and 10 °C in rainbow trout myocardium

Summary Isometric force and series membrane potential were recorded in isolated ventricular strips from rainbow trout at 20 and 10 °C. Preparations were electrically stimulated to contract at either 0.5 or 0.2 Hz. Single extrastimulations elicited a twitch force which diminished when the preceding diastole was shortened below the regular value. The stimulation following this extra stimulation evoked no potentiation of force. Apart from a marginal effect on the post extrasystolic force at 20 °C, ryanodine did not affect either of these responses or the steady-state force at 0.5 Hz. At 0.2 Hz the steady-state force was somewhat depressed by ryanodine at 20 but not at 10 °C. In contrast, extrastimulations preceded by diastoles of up to 1 h more than doubled extrasystolic force at 20 °C. This effect was removed by ryanodine. Both the potentiations and the effect of ryanodine were strongly reduced at 10 °C. Apparently, temperature acts on the release of Ca²⁺ from the sarcoplasmic reticulum, since Ca²⁺ seems to be taken up at both temperatures. Hence, at both 20 and 10 °C, the contractures evoked in a solution inhibiting sarcolemmal Ca²⁺ transfer and releasing Ca²⁺ from the sarcoplasmic reticulum were diminished by pretreatment with 15 mM caffeine. Action potential duration at 20 °C was less than half of that at 10 °C. At both temperatures it tended to be prolonged by periods of prolonged rest. No effect of ryanodine on action potential configuration was detected. The results suggest that trout myocardial sarcoplasmic reticulum, although powerful at unphysiologically low stimulation rates, does not partake in the beat-to-beat regulation of force at heart rates encountered in vivo.Abbreviations ESF extrasystolic force - SR sarcoplasmic reticulum - v _F maximal rate of force development - v _R maximal rate of relaxation - TPF time to peak force - TR _0.5 time for half relaxation - TTF duration of force development     

Tolerance of cold-acclimated and unacclimated rats to hypoxia at 1.7°C

Cold-acclimated and unacclimated rats were exposed for 4 hours to 6.6 or 4.9% O₂ in N₂ at 1.7°C. Unacclimated rats tolerated both degrees of hypoxia better than cold-acclimated rats. Cold-acclimated rats showed relatively greater increases in serum concentrations of GOT and GPT, aldolase and LDH immediately after exposure to 4.9% O₂ and a greater concentration of GPT at 6.6% O₂ than unacclimated rats. In both groups serum urea nitrogen and plasma corticosterone were elevated. Serum glucose was increased above air flow controls (20.9% O₂) in both groups by 50% at 6.6% O₂ and 100% at 4.9% O₂. Blood lactic acid levels were elevated by about 130%. The cold-acclimated rats had a higher incidence of renal tubular dilatation, fatty changes in striated muscles, and severe hepatic glycogen depletion. All rats in both groups showed myocardial inflammatory foci one day after exposure which persisted for 4 days. Cold-acclimated rats maintained higher body temperatures. The reduced tolerance of the cold-acclimated rats is attributed to an increased metabolism which increased tissue hypoxia.

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Zusammenfassung Kälteakklimatisierte und nicht akklimatisierte Ratten wurden 4 Stunden in 6.6 und 4.9% O₂ im N₂ bei 1, 7°C exponiert. Kälteakklimatisierte Tiere waren gegen beide Hypoxiegrade weniger resistent als nicht akklimatisierte. Sie zeigten einen relativ höheren Anstieg der Serumaktivität von GOT und GPT, Aldolase und LDH unmittelbar nach Uebergang in 4, 9% O₂ und eine höhere Aktivität von GPT bei 6, 6% O₂ als unakklimatisierte Ratten. In beiden Gruppen waren der Serum Harnstoff-N und Plasmakortikosteron erhöht. Serumglukose war über normoxische Kontrollen in beiden Gruppen bei 6, 6% O₂ auf 50% und bei 4, 9% O₂ auf ungefähr 100% erhöht. Die kälteakklimatisierten Ratten wiesen in höherem Masse Dilatationen der Nierentubuli auf, fettige Veränderungen in den gestreiften Muskeln und starke Depletierung des Leberglukogens. Entzündungsherde im Myokard traten nach einem Tag Exponierung auf, die 4 Tage lang bestanden. Kälteakklimatisierte Tiere behielten höhere Körpertemperaturen. Die verminderte Toleranz der kälteakklimatisierten Tiere ist Folge des erhöhten Stoffwechsels, der die Gewebshypoxie verstärkt.

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Resume On a exposé des rats acclimatés et non acclimatés durant quatre heures à des concentrations de 6, 6 et 4, 9% de O₂ dans de l'azote à 1, 7°C. Des bêtes acclimatées au froid se sont avérées moins résistantes aux deux taux d'hypoxie que leurs congénères non acclimatés. Ils présentaient une hausse relativement plus accentuée de l'activité du sérum (GOT, GPT, aldolase et LDH) immédiatement après leur séjour à 4, 9% de O₂ et une activité accrue de GPT à 6, 6% de O₂ par rapport à leurs congénères non acclimatés. De même, l'urée azotée du sérum et la corticostérone du plasma étaient plus élevées chez les deux groupes. Le glucose du sérum, déterminé par rapport à des bêtes de contrôle (20, 9% de O₂), était plus élevé dans les deux groupes de 50% à 6, 6% de O₂ et de 100% pour 4, 9% de O₂. Le taux d'acide lactique du sang a atteint alors 130%. Les rats acclimatés au froid présentaient une plus grande dilatation des tubes rénaux, des modifications lipoidiques dans les muscles striés et un épuisement rapide du glucogène du foie. Après une exposition d'un jour, on a constaté dans le myocarde des foyers d'inflammation qui se sont maintenus durant 4 jours. Les animaux acclimatés au froid présentaient des températures du corps plus élevées. La tolérance réduite des animaux acclimatés au froid est la conséquence d'un métabolisme accentué qui renforce l'hypoxie des tissus.

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A preliminary report presented to the Sixth International Biometeorological Congress, Noordwijk, The Netherlands, 3–9 September 1972.     

Bioaccumulation of Gold by Filamentous Cyanobacteria Between 25 and 200°C

Plectonema boryanum UTEX 485 was reacted with aqueous AuCl ₄ ^? solutions ( ～ 2 mM Au) at 25 to 100°C for 1 month, and 200°C for one day. Addition of AuCl₄ ^? to cyanobacteria killed the cultures instantly, and Au was precipitated throughout the cells as nanoparticles. Precipitation of octahedral crystal platelets of Au occurred in the aqueous fluid, with particle size increasing with increase in temperature from about 1.5 μ m at 25°C to 10 μ m at 100°C. Addition of AuCl₄ ^? to suspensions of the dead, autoclaved cyanobacteria also precipitated Au from solution, suggesting that the presence of cell degradation products caused instability of AuCl₄ ^? .     

Ribonucleic acid synthesis and transport in animal cells at 27°C

The failure to induce glutamine synthetase in retinal cells with hydrocortisone at 27 degrees C (37 degrees C is the normal temperature for induction) led to a study of some aspects of RNA synthesis at 27 degrees C by using the method of selective labelling with radioactive precursors, sucrose-density-gradient centrifugation and radioautography. The low-temperature treatment not only decreases the rate of RNA synthesis but also interferes with the general pattern of RNA maturation and distribution. It has been found that nuclear-cytoplasmic exchange is severely altered at low temperature and may be an explanation of the failure to induce the enzyme. When the temperature is raised from 27 degrees C to 37 degrees C, the incorporation of exogenous radioactive uridine into the RNA is distorted by a pool-dilution effect that results in an ;over-shoot' phenomenon. The kinetics of labelled uridine equilibration into the UMP pool accounts for the difficulty encountered by many investigators in ;chase' efforts with unlabelled nucleosides.     

Comparative antigenic proteins and proteomics of pathogenic Yersinia enterocolitica bio-serotypes 1B/O: 8 and 2/O: 9 cultured at 25°C and 37°C

Yersinia enterocolitica is a Gram-negative enteric pathogen responsible for a number of gastrointestinal disorders; the most pathogenic bio-serotype is 1B/O: 8. In this study, we compared the antigenicity of the outer membrane proteins and proteomics of the whole-cell proteins of a pathogenic bio-serotype 2/O: 9 isolated in China and a bio-serotype 1B/O: 8 strain isolated in Japan. Using two-dimensional gel electrophoresis, we showed that the outer membrane proteins A (OmpA), C (OmpC) and F (OmpF) were the major antigens for both strains, although proteins located on the bacterial cell membrane and enzymes involved in energy metabolism were also identified as antigenic. We compared the whole-cell proteins of the two strains cultured at 25°C and 37°C and found portions of the outer membrane proteins (OmpX, OmpF and OmpA) were downregulated when the bacteria were cultured at 37°C, whereas urease subunit gamma (UreA), urease subunit alpha (UreC) and urease accessory protein (UreE), which are involved in urease synthesis, were upregulated when the bacteria were grown at 37°C. These observations will lay a foundation to selection of diagnostic markers for pathogenic Yersinia enterocolitica, and maybe contribute to choose the vaccine targets.     

Survival of mouse oocytes after being cooled in a vitrification solution to -196°C at 95° to 70,000°C/min and warmed at 610° to 118,000°C/min: A new paradigm for cryopreservation by vitrification

There is great interest in achieving reproducibly high survivals of mammalian oocytes (especially human) after cryopreservation, but the results to date have not matched the interest. A prime cause of cell death is the formation of more than trace amounts of intracellular ice, and one strategy to avoid it is vitrification. In vitrification procedures, cells are loaded with high concentrations of glass-inducing solutes and cooled to −196 °C at rates high enough to presumably induce the glassy state. In the last decade, several devices have been developed to achieve very high cooling rates. Nearly all in the field have assumed that the cooling rate is the critical factor. The purpose of our study was to test that assumption by examining the consequences of cooling mouse oocytes in a vitrification solution at four rates ranging from 95 to 69,250 °C/min to −196 °C and for each cooling rate, subjecting them to five warming rates back above 0 °C at rates ranging from 610 to 118,000 °C/min. In samples warmed at the highest rate (118,000 °C/min), survivals were 70% to 85% regardless of the prior cooling rate. In samples warmed at the lowest rate (610 °C/min), survivals were low regardless of the prior cooling rate, but decreased from 25% to 0% as the cooling rate was increased from 95 to 69,000 °C/min. Intermediate cooling and warming rates gave intermediate survivals. The especially high sensitivity of survival to warming rate suggests that either the crystallization of intracellular glass during warming or the growth by recrystallization of small intracellular ice crystals formed during cooling are responsible for the lethality of slow warming.     

Kinetics and characteristics of 70 °C, VFA-grown, UASB granular sludge

We studied in batch reactors the kinetics and characterization of 70 °C, volatile fatty acids (VFAs)-grown, upflow anaerobic sludge blanket granular sludge with 55 and 35 °C sludge as reference. The half-saturation constant (K _s), the inhibition constant (K _i), the maximum specific methane production rate (μ_CH4max), and the inhibition response coefficient (n) of the 70 °C sludge were 6.15 mM, 48.2 mM, 0.132 h⁻¹, and 2.48, respectively, while no inhibition occurred at 55 and 35 °C, where the K _s was 3.67 and 3.82 mM, respectively. At 70 °C, the highest initial specific methanogenic activity (ISMA, 0.311 gCH₄-COD per gram volatile solids per day) on VFAs was about 12–15% lower than that on acetate and three to four times less than the ISMA for the 55 and 35 °C sludge. In the acetate conversion study, residual acetate (79 mg l⁻¹) at 70 °C was three to five times higher than that at 55 and 35 °C. Further, the methane produced as percentage of the acetate consumed at 70 °C (89%) was lower than that at 55 (95%) and 35 °C (97%). At 70 °C, 10% of the ISMA remained after 15 days of starvation as compared to 26% (55 °C) and 92% (35 °C) after 30 days of starvation. Thus, the kinetics of the 70 °C granular sludge seem to differ from those at 55 and 35 °C. Received: 1 February 1999 / Accepted: 20 March 1999     

The biochemical diversity of life near and above 100°C in marine environments

Hyperthermophilic micro-organisms grow at temperatures above 90 °C with a current upper limit of 113 °C. They are a recent discovery in the microbial world and have been isolated mainly from marine geothermal environments, which include both shallow and deep sea hydrothermal vents. By 16S rRNA analyses they are the most slowly evolving of all extant life forms, and all but two of the nearly 20 known genera are classified as Archaea (formerly Archaebacteria). Almost all hyperthermophiles are strict anaerobes. They include species of methanogens, iron-oxidizers and sulphate reducers, but the majority are obligate heterotrophs that depend upon the reduction of elemental sulphur (S°) to hydrogen sulphide for significant growth. The heterotrophs utilize proteinaceous materials as carbon and energy sources, although a few species are also saccharolytic. A scheme for electron flow during the oxidation of carbohydrates and peptides and the reduction of S° has been proposed. Two S°-reducing enzymes have been purified from the cytoplasm of one hyperthermophile (T(opt) 100 °C) that is able to grow either with and without S°. However, the mechanisms by which S° reduction is coupled to energy conservation in this organism and in obligate S°-reducing hyperthermophiles is not known. In the heterotrophs, sugar fermentation is achieved by a novel glycolytic pathway involving unusual ADP-dependent kinases and ATP synthetases, and novel oxidoreductases that are ferredoxin- rather than NAD(P)-linked. Similarly, peptide fermentation involves several unusual ferredoxin-linked oxidoreductases not found in mesophilic organisms. Several of these oxido-reductases contain tungsten, an element that is rarely used in biological systems. Tungsten is present in exceedingly low concentrations in normal sea water, but hydrothermal systems contain much higher tungsten concentrations, more than sufficient to support hyperthermophilic life.