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The Cape Floral Kingdom is an area of unique plant biodiversity in South Africa with exceptional concentrations of rare and endemic species and experiencing drastic habitat loss. Here we present the first molecular study of the microbial diversity associated with the rhizosphere soil of endemic plants of the Proteaceae family (Leucospermum truncatulum and Leucadendron xanthoconus). Genomic DNA was extracted from L. truncatulum rhizosphere soil, L. xanthoconus rhizosphere and non-rhizosphere soil and used as a template for the polymerase chain reaction (PCR) amplification of the 16S ribosomal RNA gene (rDNA). Construction and sequencing of 16S rDNA libraries revealed a high level of biodiversity and led to the identification of several novel bacterial phylotypes. The bacterial community profiles were compared by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Cluster analysis and biodiversity indices revealed that the rhizosphere soil samples were more similar to each other than to non-rhizosphere soil and the rhizosphere soil contained a bacterial diversity that was richer and more equitable compared with non-rhizosphere soil. A Chloroflexus and an Azospirillum genospecies were restricted to the L. xanthoconus rhizosphere soil and Stenotrophomonas genospecies was identified in all rhizosphere soil samples but was not present in the non-rhizosphere soil. Taxon-specific nested PCR and DGGE-identified differences between the Proteaceae plant rhizosphere soil with a Frankia genospecies restricted the L. truncatulum rhizosphere. Archaea-specific rDNA PCR, DGGE and DNA sequencing revealed that Crenarcheote genospecies were excluded from the plant rhizosphere soil and only present in non-rhizosphere soil.

The gene encoding phosphoglycerate kinase (PGK) from the ArchaeonSulfolobus solfataricus, an organism growing optimally at 87°C, was inserted into a yeast expression vector under the control of the galactose-inducibleGAL1 yeast promoter. This vector was then transformed into apgk::TRP1 yeast mutant, a strain inhibited for growth on galactose or glucose due to its lack of PGK enzyme. Slow-growing transformants were obtained on galactose plates at 37°C, but not 28°C. These transformants contained low levels of transcripts of the heterologous gene and low amounts of thermostable PGK activity. Weak expression of the hyperthermophile gene in yeast a mesophile, therefore enabled complementation of the yeastpgk defect at 37°C but not at 28°C.

▪ Abstract The Antarctic continent harbors a range of specialized and sometimes highly localized microbial biotopes. These include biotopes associated with desiccated mineral soils, rich ornithogenic soils, glacial and sea ice, ice-covered lakes, translucent rocks, and geothermally heated soils. All are characterized by the imposition of one or more environmental extremes (including low temperature, wide temperature fluctuations, desiccation, hypersalinity, high periodic radiation fluxes, and low nutrient status). As our understanding of the true microbial diversity in these biotopes expands from the application of molecular phylogenetic methods, we come closer to the point where we can make an accurate assessment of the impacts of environmental change, human intervention, and other natural and unnatural impositions. At present, it is possible to make reasonable predictions about the physical effects of local climate change, but only general predictions on possible changes in microbial community structure. The consequences of some direct human impacts, such as physical disruption of microbial soil communities, are obvious if not yet quantitated. Others, such as the dissemination of nonindigenous microorganisms into indigenous microbial communities, are not yet understood.

It is now widely accepted that the application of standard microbiological methods for the recovery of microorganisms from the environment has had limited success in providing access to the true extent of microbial biodiversity. It follows that much of the extant microbial genetic diversity (collectively termed the metagenome) remains unexploited, an issue of considerable relevance to a wider understanding of microbial communities and of considerable importance to the biotechnology industry. The recent development of technologies designed to access this wealth of genetic information through environmental nucleic acid extraction has provided a means of avoiding the limitations of culture-dependent genetic exploitation.

Our understanding of thermophile diversity is based predominantly on PCR studies of community DNA. ‘Universal’ and domain-specific rRNA gene PCR primers have historically been used for the assessment of microbial diversity without adequate regard to the degree of specificity of primer pairs to different prokaryotic groups. In a reassessment of the published primers commonly used for ‘universal’ and archaeal 16 S rDNA sequence amplification we note that substantial variations in specificity exist. An unconsidered choice of primers may therefore lead to significant bias in determination of microbial community composition. In particular, Archaea-specific primer sequences typically lack specificity for the Korarchaeota and Nanoarchaea and are often biased towards certain clades. New primer pairs specifically designed for ‘universal’ archaeal 16 S rDNA sequence amplification, with homology to all four archaeal groups, have been designed. Here we present the application of these new primers for preparation of 16 S libraries from thermophile communities.

A new archaeal isolate has been reported that is capable of growing at up to 121 degrees C. The hyperthermophile, dubbed strain 121, grows chemoautotrophically using formate as an electron donor and FeIII as an electron acceptor and is closely related to members of the archaeal genera Pyrodictium and Pyrobaculum. Although the reported maximum growth temperature of strain 121 is 8 degrees C higher than the previous record holder (Pyrolobus fumarii; Tmax = 113 degrees C), the two organisms have virtually the same optimal growth temperatures.

The Polymerase Chain Reaction (PCR) has facilitated the detection of unculturable microorganisms in virtually any environmental source and has thus been used extensively in the assessment of environmental microbial diversity. This technique relies on the assumption that the gene sequences present in the environment are complementary to the "universal" primers used in their amplification. The recent discovery of new taxa with 16S rDNA sequences not complementary to standard universal primers suggests that current 16S rDNA libraries are not representative of true prokaryotic biodiversity. Here we re-assess the specificity of commonly used 16S rRNA gene primers and present these data in tabular form designed as a tool to aid simple analysis, selection and implementation. In addition, we present two new primer pairs specifically designed for effective "universal" Archaeal 16S rDNA sequence amplification. These primers are found to amplify sequences from Crenarchaeote and Euryarchaeote type strains and environmental DNA.

Archaeal Phylogenetics Archaeal Diversity Uncultured Archaea Accessing Uncultured Genomes Archaeal Genome Sequences Fermentation and Production Products of Archaea Archaeal Processes Keywords: archaea; biomining using archaea; biotechnology; enzymes, archaeal; lipids, archaeal; phylogenetics, archaea; S-layer, archaeal

Publisher Summary There are two distinct pathways for the conversion of nitriles to carboxylic acids in nature. The nitrilase (NTase) pathway catalyzes the direct conversion of a nitrile to its corresponding carboxylic acid, whereas the nitrile hydratase (NHase) pathway catalyzes the conversion of a nitrile to its corresponding amide, which is then converted to carboxylic acid by an amidase. A large number of NHases have been detected in a variety of microorganisms. The genus Rhodococcus dominates the collective of known mesophilic NHase-producing microorganisms, and only five thermophilic NHase-producing organisms have thus far been described. Despite significant differences in origin, stability, cofactor requirements, and catalytic characteristics between the various NHase subgroups, there is a high degree of similarity between these enzymes in terms of size and protein sequence. The chapter discusses the reaction mechanism of NHase. Three reaction models involving the metal ion as a Lewis acid have been proposed. These are direct association of nitrile to metal cofactor, nucleophilic attack by a metal-bound hydroxide ion, and nucleophilic attack by an activated water molecule.

The microbial diversity in maritime meltwater pond sediments from Bratina Island, Ross Sea, Antarctica was investigated by 16S rDNA-dependent molecular phylogeny. Investigations of the vertical distribution, phylogenetic composition, and spatial variability of Bacteria and Archaea in the sediment were carried out. Results revealed the presence of a highly diverse bacterial population and a significantly depth-related composition. Assessment of 173 partial 16S rDNA clones analyzed by amplified rDNA restriction analysis (ARDRA) using tetrameric restriction enzymes (HinP1I 5'G/CGC3'and Msp I. 5'C/CGG3', BioLabs) revealed 153 different bacterial OTUs (operational taxonomic units). However, only seven archaeal OTUs were detected, indicating low archaeal diversity. Based on ARDRA results, 30 bacterial clones were selected for sequencing and the sequenced clones fell into seven major lineages of the domain Bacteria; the alpha, gamma, and delta subdivisions of Proteobacteria, the Cytophaga-Flavobacterium-Bacteroides, the Spirochaetaceae, and the Actinobacteria. All of the archaeal clones sequenced belonged to the group Crenarchaeota and phylogenetic analysis revealed close relationships with members of the deep-branching Group 1 Marine Archaea.

We have applied bioluminescent ATP detection methods to microbial enumeration in Antarctic Dry Valley mineral soils, and validated our ATP data by two independent methods. We have demonstrated that ATP measurement is a valid means of determining microbial biomass in such sites, and that the desiccated surface mineral soils of the Antarctic Dry Valleys contain cell numbers over four orders of magnitude higher than previously suggested.

In March 1996, a survey of hydrothermal sites on the island of Montserrat was carried out. Six sites (Galway's Soufriere. Gages Upper and Lower Soufrieres, Hot Water Pond, Hot River, and Tar River Soufriere) were mapped and sampled for chemical, ATP, and microbial analyses. The hydrothermal Soufriere sites on the slopes of the active Chances Peak volcano exhibited temperatures up to almost 100 degrees C and were generally either mildly acidic at pH 5-7 or strongly acidic at pH 1.5-3, but with some hot streams and pools of low redox potential at pH 7-8. Hot Water Pond sites, comprising a series of heated pools near the western shoreline of the island. were neutral and saline, consistent with subsurface heating of entrained seawater. Biological activity shown by ATP analyses was greatest in near-neutral pH samples and generally decreased as acidity increased. A variety of heterotrophic and chemolithotrophic thermophilic organisms were isolated or observed in enrichment cultures. Most of the bacteria that were obtained in pure culture were familiar acidophiles and neutrophiles, but novel, iron-oxidizing species of Sulfobacillus were revealed. These species included the first mesophilic iron-oxidizing Sulfobacillus strains to be isolated and a strain with a higher maximum growth temperature (65 degrees C) than the previously described moderately thermophilic Sulfobacillus species.

Thermophilic catechol 2,3-dioxygenase (EC 1.13.11.2) from Bacillus stearothermophilus has been immobilized on highly activated glyoxyl agarose beads. The enzyme could be fully immobilized at 4 degrees C and pH 10.05 with a high retention of activity (around 80%). Enzyme immobilized under these conditions showed little increase in thermostability compared with the soluble enzyme, but further incubation of immobilized enzyme at 25 degrees C and pH 10.05 for 3 h before borohydride reduction resulted in conjugates exhibiting a 100-fold increase in stability (c.f. the free enzyme). The stability of catechol 2,3-dioxygenase immobilized under these conditions was essentially independent of protein concentration whereas free enzyme was rapidly inactivated at low protein concentrations. An apparent stabilization factor of over 700-fold was recorded in the comparison of free and immobilized catechol 2,3-dioxygenases at protein concentrations of 10 µg/ml. Immobilization increased the 'optimum temperature' for activity by 20 degrees C, retained activity at substrate concentrations where the soluble enzyme was fully inactivated and enhanced the resistance to inactivation during catalysis. These results suggest that the immobilization of the enzyme under controlled conditions with the generation of multiple covalent links between the enzyme and matrix both stabilized the quaternary structure of the protein and increased the rigidity of the subunit structures.

It is not clear what the upper temperature limit for life is, or what specific factors will set this limit, but it is generally assumed that the limit will be dictated by molecular instability. In this review, we examine the thermal stability of two key groups of biological molecules: the intracellular small molecules/metabolites and the major classes of macromolecules. Certain small molecules/metabolites are unstable in vitro at the growth temperatures of the hyperthermophiles in which they are found. This instability appears to be dealt with in vivo by a range of mechanisms including rapid turnover, metabolic channelling and local stabilisation. Evidence to date suggests that proteins have the potential to be stable at substantially higher temperatures than those known to support life, but evidence concerning degradative reactions above 100 degrees C is slight. DNA duplex stability is apparently achieved at high temperature by elevated salt concentrations, polyamines, cationic proteins, and supercoiling rather than manipulation of C-G ratios. RNA stability seems dependent upon covalent modification, although secondary structure is probably also critical. The diether-linked lipids, which make up the monolayer membrane of most organisms growing above 85 degrees C are chemically very stable and seem potentially capable of maintaining membrane integrity at much higher temperatures. However, the in vivo implications of the in vitro instability of biomolecules are difficult to assess, and in vivo data are rare.

Metabolite arrays sample the metabolic state of bacteria and complex microbial communities while aiding enzyme discovery.

The Antarctic Dry Valleys, situated in the Ross Sea region of Eastern Antarctica, are often referred to as one of the most extreme environments on Earth. Although this statement is subject to some argument, largely surrounding the issue of what “extreme” actually means, there is no arguing that the combination of macroenvironmental and microenvironmental conditions to which organisms living in the Antarctic Dry Valleys are exposed represent a severe threat to organismal survival. The combination of extreme cold and desiccation, high soil salinity, low nutrient levels, high summer UV radiation levels, and physical instability caused by strong katabatic winds all contribute to the visual appearance of a sterile environment (1–3).

The crystal structures of the wild-type, Co(III) containing, nitrile hydratase and the mutant (βF36L / βL103S / βY127N / αD4G) enzyme from have been solved at resolutions of 1.4A and 1.15A respectively. Nitrile hydratases are noted for having an unusual cysteine claw structure at the active site. An important observation made in this paper is that cysteines α119 and α121 were both modified to cysteine sulfinic acid instead of the α121 cysteine sulfenic and α119 cysteine sulfinic acid reported previously. This was confirmed by MALDI-TOF mass spectroscopy.The nitrile hydratases catalyse the conversion of nitriles to the corresponding amides. These enzymes underlie the industrial production ofacrylamide. In the cysteine claw structure an Fe(III) or Co(III) ion is octahedrally co-ordinated to three cysteines, two of which are oxidized, and two peptide backbone amide groups. The sixth ligand, trans to the unmodified cysteine is a water molecule or a hydroxide ion. The cysteine claw has the sequence CTLCSC in the iron case and CSLCSC in the cobalt case. The enzyme itself is a α2β2 tetramer with the cysteine claw located in the α subunit and much of the active site contributed by the β subunit.Our crystal structures are almost certainly an inactive form of the enzyme, being crystallized in 100 mM MES (2[N-Morpholino]ethanesulfonic acid) which was found to be an inhibitor of the enzyme subsequent to the crystallization. However at present no evidence suggests that the inactivation is due to the oxidation of the active site cysteine sulfenic acid.The structures give insight into the determinants of the specificity of the enzyme, suggesting that βphe55 and βphe55 obstruct access to the cysteine claw complex for larger substrates allowing the hydration of only smaller aliphatic nitriles.

Methods are evaluated for the preservation of the hyperthermophile Pyrococcus furiosus. The use of glass capillary tubes stores over liquid nitrogen with dimethyl sulphoxide appears to be the preferred method of preservation. Lyophilization resulted in loss of viability and storage at room temperature and +4 o C resulted in considerable loss of viability within 4 weeks

The thermophilic soil isolate, Bacillus pallidus Dac521, expresses a constitutive nitrile hydratase. The purified enzyme was found to be a 110 kDa tetramer composed of two alpha and two beta subunits with molecular masses of 27 kDa and 29 kDa, respectively. The enzyme electrophoresed as a single protein band on native PAGE but two protein bands with isoelectric points of 4.7 and 5.5 on isoelectric focusing suggested the presence of isozymes. The purified enzyme was moderately thermostable up to 55 degrees C and the enzyme activity was stable over a broad pH range. Comparisons of the N-terminal amino acid sequences of the nitrile hydratase subunits with those of other nitrile hydratases showed up to 90% identity for the beta subunit sequence but no significant identity for the alpha subunit. The enzyme hydrolysed a narrow range of aliphatic substrates and did not hydrolyse any of the cyclic, hydroxy-, di- or aromatic nitriles tested. The activity was irreversibly inhibited by the aromatic nitrile, benzonitrile. The kinetic constants for acetonitrile, acrylonitrile and propionitrile compared favourably with those of mesophilic nitrile hydratases.

A novel, nitrile-degrading, thermophilic microorganism belonging to the genus Bacillus and most closely related to strain DSM 2349 has been isolated. The strain grew optimally at 65°C with the constitutive expression of a thermostable intracellular nitrile hydratase. No aromatic-specific "benzonitrilase" activity was detected under any conditions. The enzyme, an α2β2 heterotetramer with a native molecular weight of 110 kDa, was purified to homogeneity. N-terminal sequence data showed no homology to known bacterial α subunit sequences but had a high level of identity with other bacterial N-terminal β subunit sequences. The purified enzyme had a broad pH-activity range (50% activity limits were pH 5.1 and 8.7) and was stable in aqueous solution up to 60°C in the absence of either substrates or substrate analogues. Substrate specificity was restricted to aliphatic nitriles, but an unusual preference for branched and cyclic aliphatic nitriles was noted. Turnover rates under optimum reaction conditions were 746 and 4580 sec−1 for acetonitrile and valeronitrile, respectively.

Recombinant Sulfolobus solfataricus glyceraldehyde-3-phosphate dehydrogenase has been purified and found to be a tetramer of 148 kDa. The enzyme shows dual cofactor specificity and uses NADP+ in preference to NAD+. The sequence has been compared with other GAPDH proteins including those from other archaeal sources. The purified protein has been crystallized from ammonium sulfate to produce crystals that diffract to 2.4 A with a space group of P43212 or P41212. A native data set has been collected to 2.4 A using synchrotron radiation and cryocooling.

South Africa has a long track record in Southern Ocean and Antarctic research and has recently invested considerable funds in acquiring new infrastructure for ongoing support of this research. This infrastructure includes a new base at Marion Island and a purpose-built ice capable research vessel, which greatly expand research opportunities. Despite this investment, South Africa’s standing as a participant in this critical field is threatened by confusion, lack of funding, lack of consultation and lack of transparency. The research endeavour is presently bedevilled by political manoeuvring among groups with divergent interests that too often have little to do with science, while past and present contributors of research are excluded from discussions that aim to formulate research strategy. This state of affairs is detrimental to the country’s aims of developing a leadership role in climate change and Antarctic research and squanders both financial and human capital.

The overlapping genes encoding phosphoglycerate kinase (PGK) and glyceraldehyde-3-phosphate dehydrogenase (GraP-DH) from the hyperthermophilic archaeon Sulfolobus solfataricus have been cloned and sequenced. PCR primers based on highly conserved regions of different PGK sequences were used to isolate an internal region of the pgk gene. This was then used to screen a genomic library to isolate the full length pgk gene. A 2.5-kb BglII fragment of S. solfataricus DNA contained both the pgk gene and the gap gene immediately downstream. Unexpectedly, the pgk and gap genes were found to overlap by 8 bp, with the initiation codon of the gap gene preceding the termination codon of the pgk gene. Evidence that the two genes are co-transcribed was obtained by Northern-blot analysis. The S. solfataricus PGK amino acid sequence shows 43% and 45% identity to the PGK sequences of the Archaea Methanobacterium bryantii and Methanothermus fervidus, respectively. High level expression of the S. solfataricus PGK and GraP-DH in Escherichia coli was achieved, with heat treatment at 80 degrees C proving an effective first step in the purification of these recombinant enzymes from extracts of the E. coli host. Purified recombinant S. solfataricus PGK and GraP-DH showed half lives of 39 min and 17 h, respectively, at 80 degrees C. Unlike bacterial GraP-DH enzymes, S. solfataricus GraP-DH was able to use both NAD+ and NADP+ as cofactors, but exhibited a marked preference for NADP+.

An esterase activity obtained from a strain of Bacillus stearothermophilus was purified 5,133-fold to electrophoretic homogeneity with 26% recovery. The purified esterase had a specific activity of 2,032 mumol min-1 mg-1 based on the hydrolysis of p-nitrophenyl caproate at pH 7.0 and 30 degrees C. The apparent molecular mass was 50,000 +/- 2,000 daltons from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 45,000 +/- 3,000 daltons from gel filtration. Native polyacrylamide gels stained for esterase activity showed three bands. The isoelectric points were estimated to be 5.7, 5.8, and 6.0. Forty amino acid residues were sequenced at the N-terminus. The sequence showed no degeneracy, suggesting that the three esterases are functionally identical carboxylesterases differing by a limited number of amino acids. The enzyme showed maximum activity at pH 7.0 and was very stable at pH 6.0-8.9 with optimum stability at pH 6.0. At this pH and 60 degrees C the half-life was 170 h. Esterase activity was totally inhibited by phenylmethanesulfonyl fluoride, parahydroxymercuribenzoate, eserine, and tosyl-L-phenylalanine, but not by ethylendiaminetetra acetic acid. The esterase obeyed Michaelis-Menten kinetics in the hydrolysis of p-nitrophenyl esters, but both Vmax and KM were protein concentration-dependent. The esterase was able to hydrolyse a number of p-nitrophenyl derivatives (amino acid derivatives and aliphatic acids with different chain lengths).

A gene from the hyperthermophilic archaeon Pyrococcus furiosus , strain Vcl (DSM 3638), contains an 817-amino-acid open reading frame which shows 42% identity to the phosphoenolpyruvate (PEP) synthetase of Escherichia coli . This putative P. furiosus PEP synthetase is slightly larger than the E. coli enzyme, the region between residues 58 and 89 being absent from the latter.

We have investigated the resistance to organic solvent induced inactivation of soluble intracellular enzymes derived from a wide range of thermal environments (i.e., mesophilic to hyperthermophilic). This data is related to the cell type in an attempt to implicate the role of the bacterial membrane in interactions between the external organic phase and the cell-encapsulated enzyme. The T m (using activity loss as the criterion of protein stability) of esterases from 5 different organisms was investigated both in aqueous and in an organic-aqueous biphasic solvent systems. The stabilities of cell-free extracts and whole cell preparations were compared. The T m values support existing data on the relationship between thermophilicity and organic solvent stability. In some but not all instances, the presence of the cell structure enhanced the organic solvent inactivation of the intracellular enzyme model.

The genome of the acid- and heat-loving microorganismThermoplasma acidophilum has been sequenced. The sequence reveals the remarkable ability of this organism to pick up genes from other species, and suggests — contrary to expectations — that T. acidophilumis not the ancestor of eukaryotic cells.

Background We are profoundly ignorant about the diversity of viruses that infect the domain Archaea. Less than 100 have been identified and described and very few of these have had their genomic sequences determined. Here we report the genomic sequence of a previously undescribed archaeal virus. Results Haloarchaeal strains with 16S rRNA gene sequences 98% identical to Halorubrum saccharovorum were isolated from a hypersaline lake in Inner Mongolia. Two lytic viruses infecting these were isolated from the lake water. The BJ1 virus is described in this paper. It has an icosahedral head and tail morphology and most likely a linear double stranded DNA genome exhibiting terminal redundancy. Its genome sequence has 42,271 base pairs with a GC content of ~65 mol%. The genome of BJ1 is predicted to encode 70 ORFs, including one for a tRNA. Fifty of the seventy ORFs had no identity to data base entries; twenty showed sequence identity matches to archaeal viruses and to haloarchaea. ORFs possibly coding for an origin of replication complex, integrase, helicase and structural capsid proteins were identified. Evidence for viral integration was obtained. Conclusion The virus described here has a very low sequence identity to any previously described virus. Fifty of the seventy ORFs could not be annotated in any way based on amino acid identities with sequences already present in the databases. Determining functions for ORFs such as these is probably easier using a simple virus as a model system.

A comparison of extracellular proteases from New Zealand isolates of the genus Thermus demonstrated a number of minor but significant structural and functional differences. The comparison, based on molecular weights, isoelectric points, inhibitor responses, substrate specificity, pH optima and thermostability suggested that the four proteases were a closely related family.

The loss of activity due to proteolysis of purified L-asparaginase and beta-galactosidase from different sources correlates with the thermal instability of the enzymes. A similar correlation is found when populations of soluble proteins from micro-organisms grown at different temperatures are compared for proteolytic susceptibility and thermal stability. It is proposed that there is a general correlation between the thermostability of proteins and their resistance to proteolysis.

The thermostability of cell-free protein extracts (from 10 microorganisms grown at 37–84°C) and of 10 fully or partially purified neutral proteases was determined in aqueous solution (Tris-HCl buffer 0.1 m. pH 7.0) using protein solubility and enzyme activity loss, respectively, as the criteria of denaturation. The stability of the protein extracts and purified proteins was also determined in an aqueous-water immiscible organic solvent two-phase system using the same criteria. There was a strong positive correlation between microorganism growth temperature and the thermostability of protein extracts in both aqueous and aqueous:organic two-phase systems. A correlation also existed between protease thermostability and the stability in the aqueous:organic two-phase system. Protein stability was higher in those aqueous:organic two-phase systems with a more hydrophobic organic phase. However, for pairs of organic solvents of similar hydrophobicity, the aqueous:organic two-phase system with the higher rated interfacial tension was more denaturing. Protein extract stability was sensitive to both aqueous:gas and aqueous:organic interface size depending on the nature of the organic phase.

An extracellular metal-chelator-sensitive lytic protease (assigned the trivial name caldolysin) was isolated from a Thermus-like organism, Thermus T-351. Caldolysin was purified by affinity chromatography on Cbz-D-phenylalanine-TETA-Sepharose 4B and by gel filtration. It contained 13% carbohydrate, a single zinc atom, had a molecular weight of approx. 21,000, a pH optimum of 8 (azocasein substrate), and an isoelectric point of about 8.5. It was capable of hydrolysing many soluble and insoluble protein substrates, including collagen and elastin. No esterase activity was detected, and small peptides (less than four amino acids) and low molecular weight chromogenic substrates were not hydrolysed. A specificity for small aliphatic amino acids on either side of the splitting point was indicated. Caldolysin lysed heat-killed Gram-negative bacterial cells, but had little effect on Gram-positive organisms. Caldolysin exhibited a very high degree of thermostability (t 1/2(80 degrees C) approximately 30 h, t 1/2(90 degrees C) = 1 h). The stability (but not activity) was shown to be dependent on the presence of Ca2+ (t 1/2(75 degrees C, 10 mM calcium) greater than 193 h; t 1/2(75 degrees C, no calcium) = 4.8 min). None of the other metal ions tested (Co, Zn, Sr, Mg, Ba and Cu) was as effective as calcium in conferring thermostability of EDTA-treated caldolysin. Caldolysin was stable at room temperature in moderately acid and alkaline (pH 5 to 11) buffers for periods of greater than 90 days. Little loss of enzyme activity was detected after the incubation of caldolysin at 18 degrees C in the presence of 8 M urea, 6 M guanidine hydrochloride or 1% sodium dodecyl sulphate for 24 h. At 75 degrees C, the activity half-life of caldolysin in these denaturing agents was reduced to approx. 1 h, 1 h and more than 5 h, respectively.

The HSP70 genes of eukaryotes show up to 50% nucleotide sequence homology to the dnaK gene of Escherichia coli. This extreme structure conservation implies conservation of a function that may be needed by all cells, suggesting that other bacteria may have sequences related to HSP70 and dnaK. Amongst other functions, HSP70-like proteins may act to limit thermal protein denaturation. In this study DNA isolated from thermophilic archaebacteria (from the family Desulfurococcus) and thermophilic eubacteria (from the families Bacillus and Thermus) was probed with sequences from a heat shock inducible HSP70 gene of the yeast Saccharomyces cerevisiae. Hybridization was detected under conditions of low stringency, indicating the existence of HSP70-related sequences in the thermophilic bacteria studied.

An intracellular β-galactosidase was isolated from an extremely thermophilic gram-negative anaerobe (similar to Thermoanaerobacter). This enzyme had an apparent molecular weight of 154,000 (two types of subunits were indicated) and an isoelectric point of 5.0. It was inhibited by p-chloromercuribenzoate, by alkaline earth and transition metal ions, but was activated by alkaline metal salts and by reducing reagents. The enzyme hydrolysed o-nitrophenol-β-d-galactopyranoside optimally at pH 6.0 with an apparent Km of 4.3 mm and a maximal turnover number of 431s−1 (assuming a single active site). The specific activity at 70°C was 99 μmol o-nitrophenol produced min−1 mg−1 protein. Hydrolysis of lactose demonstrated a substrate concentration-dependent Km and Vmax. The enzyme was moderately thermostable, with a half-life of 155 min at 75°C.

The hypolithic microbial community associated with quartz pavement at a high-altitude tundra location in central Tibet is described. A small-scale ecological survey indicated that 36% of quartz rocks were colonized. Community profiling using terminal restriction fragment length polymorphism revealed no significant difference in community structure among a number of colonized rocks. Real-time quantitative PCR and phylogenetic analysis of environmental phylotypes obtained from clone libraries were used to elucidate community structure across all domains. The hypolithon was dominated by cyanobacterial phylotypes (73%) with relatively low frequencies of other bacterial phylotypes, largely represented by the chloroflexi, actinobacteria, and bacteriodetes. Unidentified crenarchaeal phylotypes accounted for 4% of recoverable phylotypes, while algae, fungi, and mosses were indicated by a small fraction of recoverable phylotypes. © 2010 The Author(s)., published_or_final_version

A monitoring and indicator system can inform policy

1. 1. Most enzymes from extreme thermophiles do not possess higher specific activities than similar enzymes from mesophiles (measured at their respective growth temperatures). 2. 2. However, using protein substrates, the specific activities of thermophilic proteinases are considerably higher than those of most microbial and eukaryotic proteinases. 3. 3. This property could be attributed to purely kinetic influences on the enzyme, to some specific “design” feature of the proteinase, or to the effects of temperature on the substrate. 4. 4. Comparisons of the rates of hydrolysis of large and small substrates by both mesophilic and thermophilic proteinases suggest that temperature-induced changes in substrate susceptibility are a major factor.

Caldolysin, the extracellular thermostable metal-chelator-sensitive lytic protease from Thermus T-351 was immobilized to Sepharose 4B, CM-cellulose, and controlled pore glass (CPG). Although protein binding efficiencies were high (96, 88, and 95%), some loss of enzyme activity occurred on immobilization (26, 69, and 89%). The pH optimum of both CM-cellulose and CPG-immobilized Caldolysin was decreased by about one pH unit. The K(m) for Sepharose-Caldolysin was unchanged with respect to the free protease, while those for CM-cellulose-Caldolysin and CPG-Caldolysin were lower by approximately one order of magnitude. Immobilization to both Sepharose and CM-cellulose increased the thermostability of Caldolysin at high temperatures, while CPG-Caldolysin was less thermostable than the free protease.