Thermal adaptation analyzed by comparison of protein sequences from mesophilic and extremely thermophilic Methanococcus species

The genome sequence of the extremely thermophilic archaeon Methanococcus jannaschii provides a wealth of data on proteins from a thermophile. In this paper, sequences of 115 proteins from M. jannaschii are compared with their homologs from mesophilic Methanococcus species. Although the growth temperatures of the mesophiles are about 50°C below that of M. jannaschii, their genomic G+C contents are nearly identical. The properties most correlated with the proteins of the thermophile include higher residue volume, higher residue hydrophobicity, more charged amino acids (especially Glu, Arg, and Lys), and fewer uncharged polar residues (Ser, Thr, Asn, and Gln). These are recurring themes, with all trends applying to 83–92% of the proteins for which complete sequences were available. Nearly all of the amino acid replacements most significantly correlated with the temperature change are the same relatively conservative changes observed in all proteins, but in the case of the mesophile/thermophile comparison there is a directional bias. We identify 26 specific pairs of amino acids with a statistically significant (P < 0.01) preferred direction of replacement.

Thermus thermophilus: A link in evolution of the tRNA-dependent amino acid amidation pathways

Thermus thermophilus possesses an aspartyl-tRNA synthetase (AspRS2) able to aspartylate efficiently tRNAAsp and tRNAAsn. Aspartate mischarged on tRNAAsn then is converted into asparagine by an ω amidase that differs structurally from all known asparagine synthetases. However, aspartate is not misincorporated into proteins because the binding capacity of aminoacylated tRNAAsn to elongation factor Tu is only conferred by conversion of aspartate into asparagine. T. thermophilus additionally contains a second aspartyl-tRNA synthetase (AspRS1) able to aspartylate tRNAAsp and an asparaginyl-tRNA synthetase able to charge tRNAAsn with free asparagine, although the organism does not contain a tRNA-independent asparagine synthetase. In contrast to the duplicated pathway of tRNA asparaginylation, tRNA glutaminylation occurs in the thermophile via the usual pathway by using glutaminyl-tRNA synthetase and free glutamine synthesized by glutamine synthetase that is unique. T. thermophilus is able to ensure tRNA aminoacylation by alternative routes involving either the direct pathway or by conversion of amino acid mischarged on tRNA. These findings shed light on the interrelation between the tRNA-dependent and tRNA-independent pathways of amino acid amidation and on the processes involved in fidelity of the aminoacylation systems.

Initiation of clement surface conditions on the earliest Earth

In the beginning the surface of the Earth was extremely hot, because the Earth as we know it is the product of a collision between two planets, a collision that also created the Moon. Most of the heat within the very young Earth was lost quickly to space while the surface was still quite hot. As it cooled, the Earth's surface passed monotonically through every temperature regime between silicate vapor to liquid water and perhaps even to ice, eventually reaching an equilibrium with sunlight. Inevitably the surface passed through a time when the temperature was around 100°C at which modern thermophile organisms live. How long this warm epoch lasted depends on how long a thick greenhouse atmosphere can be maintained by heat flow from the Earth's interior, either directly as a supplement to insolation, or indirectly through its influence on the nascent carbonate cycle. In both cases, the duration of the warm epoch would have been controlled by processes within the Earth's interior where buffering by surface conditions played little part. A potentially evolutionarily significant warm period of between 105 and 107 years seems likely, which nonetheless was brief compared to the vast expanse of geological time.

Breakdown of plant cell biomass by filamentous fungi

Three species of filamentous fungi, Botrytis cinerea, Sporotrichum thermophile and Trichoderma viride, have been selected to assess the potential of utilizing filamentous fungi to degrade plant cell biomass produced by mass cell culture techniques. All three fungal species grew comparatively well on plant cell biomass with no requirement for supplementary nutrients. Of the three species assessed B. cinerea demonstrated the most growth. This species also produced the greatest yield of D-glucose. However, when culture conditions were modified, yields of D-glucose were markedly reduced indicating that the combination of species and culture conditions must be thoroughly investigated to ensure maximum product yield. The growth of filamentous fungi on plant cells also markedly affected the nature of the resulting fungal-plant cell residue, increasing the levels of soluble carbohydrates and essential amino acids with the largest increase in these materials being promoted by B. cinerea.

The breakdown of plant cell biomass by fungi

Three species of fungi Sporotrichum thermophile, Botrytis cinerea and Trichoderma viride were assessed for their ability to utilize a variety of plant cell substrates (methanol extracted), Catharanthus roseus, Daucus carota, re-autoclaved C. roseus, re-autoclaved D. carota) which preliminary studies had indicated contained the necessary nutrients for fungal growth. Incubated in a suitable manner all three fungal species were able to grow on C. roseus and D. carota plant cell biomass in addition to material which had undergone methanol extraction or a re-autoclaving process to remove soluble components. Fungal biomass yields were markedly influenced by substrate, with each fungal species demonstrating a preference for particular plant cell material. Incubation conditions i.e. static or shaken and temperature also proved important. Release of glucose (i.e. values higher than Day 0) promoted by fungal breakdown of plant cell biomass was only noted with methanol extracted, re-autoclaved C. roseus and re-autoclaved D. carota material. A re-autoclaved substrate was also generally associated with high fungal C1, Cx, B-glucosidase and endo-polygalacturonase activity. In addition for each enzyme highest values were usually obtained from a particular fungal species. Buffering cultures at pH 3 or 5 further influenced enzyme activity, however in a majority of cases when flasks were unbuffered and the pH rose naturally to alkaline values higher enzyme activity was recorded. Likewise Tween 80 addition had only a limited beneficial effect. Finally filtrates containing glucose produced both from the re-autoclaving process and through fungal activity on plant cell biomass were utilized for Fusarium oxysporum, Saccharomyces cerevisiae and C. roseus plant cell culture. Although reasonable fungal biomass was obtained the use of such filtrates proved unsuitable for plant cell growth.

An 8x8 thermopile based uncooled infrared sensor

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Toxin and Growth Responses of the Neurotoxic Dinoflagellate Vulcanodinium rugosum to Varying Temperature and Salinity

Vulcanodinium rugosum, a recently described species, produces pinnatoxins. The IFR-VRU-01 strain, isolated from a French Mediterranean lagoon in 2010 and identified as the causative dinoflagellate contaminating mussels in the Ingril Lagoon (French Mediterranean) with pinnatoxin-G, was grown in an enriched natural seawater medium. We tested the effect of temperature and salinity on growth, pinnatoxin-G production and chlorophyll a levels of this dinoflagellate. These factors were tested in combinations of five temperatures (15, 20, 25, 30 and 35 °C) and five salinities (20, 25, 30, 35 and 40) at an irradiance of 100 µmol photon m−2 s−1. V. rugosum can grow at temperatures and salinities ranging from 20 °C to 30 °C and 20 to 40, respectively. The optimal combination for growth (0.39 ± 0.11 d−1) was a temperature of 25 °C and a salinity of 40. Results suggest that V. rugosum is euryhaline and thermophile which could explain why this dinoflagellate develops in situ only from June to September. V. rugosum growth rate and pinnatoxin-G production were highest at temperatures ranging between 25 and 30 °C. This suggests that the dinoflagellate may give rise to extensive blooms in the coming decades caused by the climate change-related increases in temperature expected in the Mediterranean coasts.