oneidensis MR-1 via the

msh gene system. The strains used in this study are summarized in Table 1. Cultures of S. oneidensis MR-1 and Escherichia coli strains were grown in Luria–Bertani (LB) medium at 30 and 37 °C, respectively. As necessary, the medium ABT-263 clinical trial was supplemented with 25 μg mL−1 kanamycin, 10 μg mL−1 gentamicin, or 5 μg mL−1 tetracyclin. Biofilm experiments were carried out in lactate medium (LM), [0.02% w/v yeast extract, 0.01% w/v peptone, 10 mM (w/v) HEPES (pH 7.4), 10 mM NaHCO3] with a lactate concentration of 0.5 mM, or minimal media (MM) [485 μM CaCl2·2H2O, 5 μM CoCl2, 0.2 μM CuSO4·5H2O, 57 μM H3BO3, 1.27 mM K2HPO4, 0.73 mM KH2PO4, 1.0 mM MgSO4·7H2O, 1.3 μM MnSO4, 67.2 μM Na2EDTA, 3.9 μM Na2MoO4·2H2O, 1.5 μM Na2SeO4, 150 mM NaCl, 2 mM NaHCO3, 5 μM NiCl2·5H2O, 1 μM ZnSO4, 9 mM (NH4)2SO4, 0.5 mM lactate, and 5 mM HEPES, pH 7.4] (Gescher et al., 2008). Flow-chamber-grown biofilms were grown as described previously (Thormann et al., 2004). All biofilm

characterizations were conducted in duplicate in at least two independent experiments. Static biofilms were grown as described earlier (O’Toole & Kolter, 1998; Pratt & Kolter, 1998). Biofilms grown on LM for 12 h were exposed to carbohydrates by replacement of the medium with LM amended with the specified carbohydrate to a final concentration of 20 μM. Confocal laser scanning microscopy (CLSM) images were taken immediately before carbohydrate Loperamide exposure and after 2 h of exposure. Twitching motility was EPZ-6438 nmr assayed either in soft agar plates (LB, LM, and MM) or by microscopic time-lapse examination

of cells growing between a glass coverslip and an LB agar plate (Semmler et al., 1999). All genetic work was carried out according to standard protocols or following the manufacturer’s instructions (Sambrook et al., 1989). Kits for the isolation and/or the purification of DNA were obtained from Qiagen (Valencia, CA), and enzymes were purchased from New England Biolabs (Beverly, MA), if not indicated otherwise. AS93, which constitutively expresses green fluorescent protein, served as the parent strain for all mutants (Thormann et al., 2004). In-frame deletion mutants were constructed as reported previously (Thormann et al., 2005). To complement the mutants, the corresponding genes were amplified from wild-type (AS93) chromosomal DNA. All genes were sequenced to verify fidelity. The fragments were introduced into either pME6041-emptyAraC (pilT) or pLacTac (pilD, pilA, and mshA) (Thormann et al., 2006) via restriction enzyme digestion and ligation. pME6041-emptyAraC was constructed from pBAD42 (J. Beckwith, unpublished data) and pME6041 by restriction enzyme digestion of pBAD42, gel purification of the fragment containing the PBAD promoter, and ligation into similarly digested pME6041.

Int GSK1120212 J Cancer 2003; 103: 142–144. 18 Mocroft A, Kirk O, Clumeck N et al. The changing pattern of Kaposi sarcoma in patients with HIV, 1994–2003: the EuroSIDA Study. Cancer 2004; 100: 2644–2654. 19 Engels EA, Pfeiffer RM, Goedert JJ et al. Trends in cancer risk among people with AIDS in the United States 1980–2002. AIDS

2006; 20: 1645–1654. 20 Franceschi S, Maso LD, Rickenbach M et al. Kaposi sarcoma incidence in the Swiss HIV Cohort Study before and after highly active antiretroviral therapy. Br J Cancer 2008; 99: 800–804. 21 Guiguet M, Boué F, Cadranel J et al. Effect of immunodeficiency, HIV viral load, and antiretroviral therapy on the risk of individual malignancies (FHDH-ANRS CO4): a prospective cohort study. Lancet Oncol 2009; 10: 1152–1159. 22 Selik RM, Byers RH Jr, Dworkin MS. Trends in diseases reported on U.S. death certificates that mentioned HIV infection, 1987–1999. J Acquir Immune Defic Syndr 2002; 29: 378–387. 23 Simard EP, Pfeiffer RM, Engels EA. Cumulative incidence of cancer among individuals with acquired immunodeficiency syndrome in the United States. Cancer 2011; 117: 1089–1096. 24 Lodi S, Guiguet M, Costagliola D et al. Kaposi sarcoma incidence find more and survival among HIV-infected homosexual men

after HIV seroconversion. J Natl Cancer Inst 2010; 102: 784–792. 25 Pipkin S, Scheer S, Okeigwe I et al. The effect of HAART and calendar period on Kaposi’s sarcoma and non-Hodgkin lymphoma: results of a match between an AIDS and cancer registry. AIDS 2011; 25: 463–471. 26 Shiels MS, Pfeiffer RM, Gail MH et al. Cancer burden in the HIV-infected population in the United States. J Natl Cancer Inst 2011; 103: 753–762. 27 Sitas F, Carrara H, Beral V et al. Antibodies

against human herpesvirus 8 in black South African patients with cancer. N Engl J Med 1999; 340: 1863–1871. 28 Bassett MT, Chokunonga E, Mauchaza B et al. Cancer in the African population of Harare, Zimbabwe, 1990–1992. Int J Cancer 1995; 63: 29–36. 29 Wabinga HR, Parkin DM, Wabwire-Mangen F, Nambooze S. Trends in cancer incidence in Kyadondo County, Uganda, 1960–1997. Br J Cancer 2000; 82: 1585–1592. 30 Parkin DM, Sitas F, Chirenje M et al. Part I: Cancer Depsipeptide cost in indigenous Africans–burden, distribution, and trends. Lancet Oncol 2008; 9: 683–692. 31 Mosam A, Carrara H, Shaik F et al. Increasing incidence of Kaposi’s sarcoma in black South Africans in KwaZulu-Natal, South Africa (1983–2006). Int J STD AIDS 2009; 20: 553–556. 32 Chokunonga E, Borok MZ, Chirenje ZM et al. Trends in the incidence of cancer in the black population of Harare, Zimbabwe 1991–2010. Int J Cancer 2013; 133: 721–729. 33 Mosam A, Uldrick TS, Shaik F et al. An evaluation of the early effects of a combination antiretroviral therapy programme on the management of AIDS-associated Kaposi’s sarcoma in KwaZulu-Natal, South Africa. Int J STD AIDS 2011; 22: 671–673. 34 Casper C.

, 1988). In any case, it remains unclear whether the exposure

to IS only inhibited the expression of DPAG-evoked defensive behaviors or attenuated the aversive emotion as well. The dissociation of motor and emotional effects is not unprecedented. Indeed, Maier et al. (1986) showed that uncontrollable stress affects behavioral and hormonal responses differently. If so, the selective inhibition of behavioral responses could explain the paucity of overt flight behaviors in clinical panic. After all, a spontaneous panic attack is conspicuously an uncontrollable stress. In any event, the present study suggests that IS inhibits a DPAG Ulixertinib price in-built motivational system that may be involved in behavioral resilience to stress. This study was part of the Doctorate Thesis of J.W.Q.S. Authors were recipients of postgraduate (C.A.R., C.J.T.M.) and senior

(L.C.S., S.T.) CNPq research fellowships. Research was funded by FAPES (38.413.280/2007), CNPq/FAPES (55203345/11) and UFES/AFIP (23068020409/2010-43) grants. Histology was performed at the Laboratory of Molecular Histology and Immunohistochemistry of the Health Sciences Centre of the Federal University of Espirito Santo. This study was granted the Merit Award at the CH5424802 cell line XXVI Annual Meeting of the Brazilian Federation of Societies of Experimental Biology (FESBE). Authors declare no conflict of interest, financial interest or otherwise, that could have influenced the objectivity of observations herein reported. Abbreviations %OAE percentage of open-arm entries of elevated plus-maze %OAT percentage of open time of elevated plus-maze d.f. degree of freedom DLPAG dorsolateral periaqueductal gray DMPAG dorsomedial periaqueductal gray DPAG dorsal periaqueductal gray EAE enclosed arm entries of elevated plus-maze EPM elevated plus-maze ES escapable shock FS fictive shocks FST forced-swimming test FST-1 forced-swimming training session FST-2 forced-swimming test session I50 median effective intensity IS Decitabine research buy inescapable shock LPAG lateral periaqueductal gray PAG periaqueductal gray matter PD panic disorder TCP time in central

platform of elevated plus-maze VLPAG ventrolateral periaqueductal gray “
“Electrical synapses formed by neuronal gap junctions composed of connexin36 (Cx36) are a common feature in mammalian brain circuitry, but less is known about their deployment in spinal cord. It has been reported based on connexin mRNA and/or protein detection that developing and/or mature motoneurons express a variety of connexins, including Cx26, Cx32, Cx36 and Cx43 in trigeminal motoneurons, Cx36, Cx37, Cx40, Cx43 and Cx45 in spinal motoneurons, and Cx32 in sexually dimorphic motoneurons. We re-examined the localization of these connexins during postnatal development and in adult rat and mouse using immunofluorescence labeling for each connexin.

, 1988). In any case, it remains unclear whether the exposure

to IS only inhibited the expression of DPAG-evoked defensive behaviors or attenuated the aversive emotion as well. The dissociation of motor and emotional effects is not unprecedented. Indeed, Maier et al. (1986) showed that uncontrollable stress affects behavioral and hormonal responses differently. If so, the selective inhibition of behavioral responses could explain the paucity of overt flight behaviors in clinical panic. After all, a spontaneous panic attack is conspicuously an uncontrollable stress. In any event, the present study suggests that IS inhibits a DPAG Galunisertib in-built motivational system that may be involved in behavioral resilience to stress. This study was part of the Doctorate Thesis of J.W.Q.S. Authors were recipients of postgraduate (C.A.R., C.J.T.M.) and senior

(L.C.S., S.T.) CNPq research fellowships. Research was funded by FAPES (38.413.280/2007), CNPq/FAPES (55203345/11) and UFES/AFIP (23068020409/2010-43) grants. Histology was performed at the Laboratory of Molecular Histology and Immunohistochemistry of the Health Sciences Centre of the Federal University of Espirito Santo. This study was granted the Merit Award at the AZD9291 concentration XXVI Annual Meeting of the Brazilian Federation of Societies of Experimental Biology (FESBE). Authors declare no conflict of interest, financial interest or otherwise, that could have influenced the objectivity of observations herein reported. Abbreviations %OAE percentage of open-arm entries of elevated plus-maze %OAT percentage of open time of elevated plus-maze d.f. degree of freedom DLPAG dorsolateral periaqueductal gray DMPAG dorsomedial periaqueductal gray DPAG dorsal periaqueductal gray EAE enclosed arm entries of elevated plus-maze EPM elevated plus-maze ES escapable shock FS fictive shocks FST forced-swimming test FST-1 forced-swimming training session FST-2 forced-swimming test session I50 median effective intensity IS Demeclocycline inescapable shock LPAG lateral periaqueductal gray PAG periaqueductal gray matter PD panic disorder TCP time in central

platform of elevated plus-maze VLPAG ventrolateral periaqueductal gray “
“Electrical synapses formed by neuronal gap junctions composed of connexin36 (Cx36) are a common feature in mammalian brain circuitry, but less is known about their deployment in spinal cord. It has been reported based on connexin mRNA and/or protein detection that developing and/or mature motoneurons express a variety of connexins, including Cx26, Cx32, Cx36 and Cx43 in trigeminal motoneurons, Cx36, Cx37, Cx40, Cx43 and Cx45 in spinal motoneurons, and Cx32 in sexually dimorphic motoneurons. We re-examined the localization of these connexins during postnatal development and in adult rat and mouse using immunofluorescence labeling for each connexin.

, 2008). In this scenario, the subsequent enhancement in aquatic viral numbers is not caused by lytic success from the inoculation of allochtonous viruses, but rather from the massive activation of prophages from local populations. We thus need more

data to disentangle the complex host specificity paradigm of phage–prokaryotes interactions in aquatic habitats, especially by preventing prokaryotes from being subjected to perceptible changes in environmental conditions. In this study, cross-inoculation assays were conducted between phages and prokaryotes from three aquatic sites of contrasting salinity (freshwater, seawater and hypersaline water). Before incubation, viral concentrates (VC) were resuspended and reconcentrated into ultrafiltered water of the targeted prokaryotes selleck chemicals llc to avoid potential bias from induction of lysogenic Roxadustat in vitro phages. Water samples were collected in Senegal (West Africa), on March 5 and 6, 2007 in three ecosystems with contrasting salinity, including (1) a freshwater station (F): Dakar Bango Reservoir, which is the main drinking water supply of St. Louis city, (2) a near-shore seawater station (S) of the Atlantic Ocean located c. 100 m from the Senegalese coast, near the city of St. Louis and (3) a hypersaline (salinity, 310‰) water station (H) located at the center of Lake Retba [more details in Bettarel et al. (2006)] (Table 1). Triplicate

20 L volumes of subsurface water (<0.5 m) were collected at each sampling station and transferred into polycarbonate Nalgene bottles before immediate transfer to the laboratory for processing as follows: Fifteen liters of water from the freshwater and marine site and 4 L from the Retba site were sequentially filtered

onto 3- and 0.2-μm pore-size polycarbonate membranes (Isopore, Millipore, Molsheim, France) to remove larger particles and organisms. The viral filtrates (<0.2 μm) were then ultrafiltered using a Pellicon system (30 kDa) to obtain a solution of concentrated viruses in a final volume of c. 300 mL. This volume was then divided into three replicate VC of 100 mL. To avoid potential bias from nutrient or salinity shifts during the cross inoculations, all the different VCs generated at each site were resuspended in 4 L of ultrafiltered Hydroxychloroquine manufacturer water (<30 kDa) and reconcentrated by ultrafiltration to a final volume of 100 mL. Nine triplicate ‘neoconcentrates’ were thus generated for the cross-inoculation assays, with respect to the different transplantation possibilities (see Fig. 1). The 100 mL neoconcentrates were added to an equivalent volume of 3 μm filtered water from the three different sites in 250-mL polyethylene UV-permeable sterile Whirl-Pack® bags, and incubated for 24 h, at ambient temperature (26 °C) in a large bath (74 × 32 × 18 cm) filled with water corresponding to the incubation type.

In that report, Lee et al. (2003) found no differences between C57BL/6J and two other inbred strains, namely 129/S1 and BALB/c mice at 8 weeks of age. However, using the counting parameters we have established in this study, we found differences between these three strains at 2 months of age with 129/S1 producing the highest number of RMS proliferating cells, followed by BALB/c and then C57BL/6J (unpublished data). These discordant results are probably due to the region that was quantified. In the Lee et al. study, the authors quantified the total numbers of BrdU-positive neuroblasts in four zones along the SVZ–RMS axis and one of the zones included the anterior SVZ caudal

to the tip of the lateral ventricle, which was excluded from our work. We purposely

CHIR99021 left out the SVZ in this study because Z-VAD-FMK purchase the cellular composition of the SVZ is far more complex than that of the RMS (Alvarez-Buylla & Garcia-Verdugo, 2002; Merkle et al., 2007). For example, some of the cell types that are present in the SVZ but absent in the RMS include oligodentrocyte progenitors and transit amplifying precursors that are also actively dividing like the neuroblasts (Doetsch et al., 1997), thus making the comparison between SVZ and RMS counts tenuous. Interestingly, a re-examination of just the RMS in the Lee et al. study showed inter-strain variation in the total numbers of BrdU-positive neuroblasts that were very much in line with the strain differences observed in our unpublished study. The wide range of natural variation in the RMS proliferative Tangeritin capacity in the AXB/BXA RI lines made it possible for us to explore the genetic underpinning of cell proliferation in the adult RMS using QTL analysis. The strain distribution pattern was

suggestive of the inheritance of the trait through a major gene locus on distal Chr 11 and the mapping of this 1.5-Mb-wide QTL was not confounded by age, sex and body weight. The identification of a narrow QTL is usually achieved by phenotyping a large genetic reference panel of RI strains, yet we were able to achieve this level of precision by ‘subphenotyping’ the regions involved in olfactory bulb neurogenesis and by refining our quantitative analysis to only the RMS. Basic Mendelian inheritance patterns would suggest that RI strains with more BrdU-positive cells would inherit cell proliferation alleles from the A/J parent, while strains with fewer BrdU-positive cells would inherit fewer cell proliferation alleles from the C57BL/6J genome. A close examination of the allelic alignments of the genetic markers located in the Rmspq1 QTL interval shows an unexpected pattern. A single B allele in this interval had an additive effect on the proliferation of the RMS which was opposite to our phenotype observation that A/J had more proliferating cells in the RMS. QTLs showing the unexpected allelic contribution as observed here are known as ‘cryptic QTLs’.

, 2005a). Mass spectrometry analyses provided the molecular basis of these peculiar resistance

phenotypes: Erm(38) is a reluctant dimethyltransferase that leaves most of the rRNA molecules either monomethylated or unmethylated (Madsen et al., 2005b), and Erm(37) further methylates nucleotides A2057 and A2059 after monomethylation of A2058 (Madsen et al., 2005a). These phenotypic diversities of the Erm methylases suggest that frequent gene duplications and resultant paralog segregations eventually caused phylogenetic anomalies in the Erm clade of the Actinobacteria. The tree-constructing algorithms failed to Selisistat molecular weight separate Erm proteins into either monomethylases (type I) or dimethylases (type II). Separate analysis of the Erm N-terminal and C-terminal domains or subdomains also could not distinguish monomethylase from dimethylase activities in the phylogenetic trees (data not shown). This research was supported by the Research Program for New Drug Target Discovery (2008-2005325) and the Basic Science Research Program (2010-0011442) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (to H.J.J.). Fig. S1. Sequence alignments of representative amino acid sequences of Erm methylases and KsgA/Dim1 proteins. MG-132 mw Table S1. List of sequences of KsgA/Dim1 used in phylogenetic

analyses. Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. “
“In the absence of added DNA, thermophilic DNA polymerases synthesize double-stranded DNA from free dNTPs, which consist of numerous repetitive units (ab initio DNA synthesis). The addition of thermophilic restriction endonuclease (REase), or nicking endonuclease (NEase), effectively stimulates ab initio DNA synthesis

and determines the nucleotide sequence of reaction products. We have found that NEases Nt.AlwI, Nb.BbvCI, and Nb.BsmI with non-palindromic recognition sites stimulate the synthesis of sequences organized mainly as palindromes. Moreover, the nucleotide sequence of the palindromes appeared to be dependent on NEase recognition/cleavage modes. Thus, the heterodimeric Nb.BbvCI stimulated Resminostat the synthesis of palindromes composed of two recognition sites of this NEase, which were separated by AT-reach sequences or (A)n(T)m spacers. Palindromic DNA sequences obtained in the ab initio DNA synthesis with the monomeric NEases Nb.BsmI and Nt.AlwI contained, along with the sites of these NEases, randomly synthesized sequences consisted of blocks of short repeats. These findings could help investigation of the potential abilities of highly productive ab initio DNA synthesis for the creation of DNA molecules with desirable sequence.

Illness was reported by 19% of elderly travelers, compared to 34% PI3K Inhibitor Library cell line of young

travelers. In general, these numbers are lower than the 43% illness rate reported in Scottish travelers,11 the 49% illness rate in Swedes12 or Americans.3 Although some of those studies were from the eighties and one could assume a possible change in risk-prone behaviors amongst young and elderly populations alike, similar results are reported in more recent series of American and Israeli travelers (64% and 70%, respectively).2,13 A possible explanation is the relatively short duration of travel in our study, since for all destinations the risk of illness has been correlated with travel duration regardless of age.2 Diarrhea was the most common complaint in both groups and was experienced significantly less often by the elderly travelers (10% vs 25%). This percentage of travelers with diarrhea is similar to that reported in other studies which ranged from 20% to over 50%.2,9,10,13,14 Diarrhea was also found to be the predominant complaint of younger travelers after returning home (3.44% vs 0.52% amongst the elderly and the younger travelers, respectively, p = 0.04). Aging reduces stomach acidity, an important protective factor against diarrhea-causing organisms. Acidity might also be reduced by diabetes and by certain medications such as histamine receptor blockers and proton pump inhibitors. Yet,

elderly travelers DNA ligase had a lower incidence ABT-263 of diarrhea, possibly because they frequently go to better restaurants and are less adventurous eaters. As in other studies,2,13 respiratory tract symptoms were the second most common reported illness. Most febrile episodes

were associated with diarrhea and respiratory symptoms and consequently occurred significantly less often in elderly travelers. The association between old age and decreasing health risks has been reported elsewhere.2,9 However, it has consistently been explained by a shorter duration of travel, a factor that was eliminated in our study. As presented here, the lower incidence of illness during and after travel in our patients was due to adherence to health-related recommendations and travel mode. Other adverse health events occurred with less frequency, although some have important implications. Elderly travelers might be less physically fit than younger travelers and thus are more prone to injury. Two elderly travelers sustained traumatic falls, one of which necessitated orthopedic surgery after returning home. Significantly more elderly travelers reached heights above 1,500 m and used acetazoleamide for mountain sickness prophylaxis compared to the younger travelers (26% vs 12%, respectively). Even though high-altitude illness is much more likely to occur at altitudes higher than 2,500 m than at lower altitudes,15 it is being increasingly recognized at altitudes between 1,500 and 2,500 m.

Illness was reported by 19% of elderly travelers, compared to 34% Raf inhibitor of young

travelers. In general, these numbers are lower than the 43% illness rate reported in Scottish travelers,11 the 49% illness rate in Swedes12 or Americans.3 Although some of those studies were from the eighties and one could assume a possible change in risk-prone behaviors amongst young and elderly populations alike, similar results are reported in more recent series of American and Israeli travelers (64% and 70%, respectively).2,13 A possible explanation is the relatively short duration of travel in our study, since for all destinations the risk of illness has been correlated with travel duration regardless of age.2 Diarrhea was the most common complaint in both groups and was experienced significantly less often by the elderly travelers (10% vs 25%). This percentage of travelers with diarrhea is similar to that reported in other studies which ranged from 20% to over 50%.2,9,10,13,14 Diarrhea was also found to be the predominant complaint of younger travelers after returning home (3.44% vs 0.52% amongst the elderly and the younger travelers, respectively, p = 0.04). Aging reduces stomach acidity, an important protective factor against diarrhea-causing organisms. Acidity might also be reduced by diabetes and by certain medications such as histamine receptor blockers and proton pump inhibitors. Yet,

elderly travelers else had a lower incidence learn more of diarrhea, possibly because they frequently go to better restaurants and are less adventurous eaters. As in other studies,2,13 respiratory tract symptoms were the second most common reported illness. Most febrile episodes

were associated with diarrhea and respiratory symptoms and consequently occurred significantly less often in elderly travelers. The association between old age and decreasing health risks has been reported elsewhere.2,9 However, it has consistently been explained by a shorter duration of travel, a factor that was eliminated in our study. As presented here, the lower incidence of illness during and after travel in our patients was due to adherence to health-related recommendations and travel mode. Other adverse health events occurred with less frequency, although some have important implications. Elderly travelers might be less physically fit than younger travelers and thus are more prone to injury. Two elderly travelers sustained traumatic falls, one of which necessitated orthopedic surgery after returning home. Significantly more elderly travelers reached heights above 1,500 m and used acetazoleamide for mountain sickness prophylaxis compared to the younger travelers (26% vs 12%, respectively). Even though high-altitude illness is much more likely to occur at altitudes higher than 2,500 m than at lower altitudes,15 it is being increasingly recognized at altitudes between 1,500 and 2,500 m.

Interestingly, all the hyperthermophiles and thermophiles (except three variants) always grouped together, whereas the mesophiles and the psychrophiles preferred to remain in a separate cluster. Similar results were observed even in the case of k-means clustering. To demonstrate

the effect of temperature on folding patterns, k-means clustering was also performed at 20, 37 and 70 °C, which are the representative temperatures for psychrophiles, mesophiles ABT-888 in vivo and thermophiles, respectively, using both dG and Tm values. At 20 °C, two distinct clusters were formed by the thermophiles and hyperthermophiles, whereas some of the thermophiles strayed into the groups of mesophiles and psychrophiles. At 37 °C, the thermophiles and hyperthermophiles showed a better composure and this was even strengthened further at 70 °C (Supporting selleckchem Information, Figs S1 and S2). Thus, tRNA folding patterns can, in principle, distinguish the organisms into groups based on their OGT. The present analysis indicates that adaptation of thermophiles and hyperthermophiles to elevated temperatures

imposes selective constraints on the number and distribution of tRNAs, the GC content of the tRNA genes and on their secondary structures and folding patterns. The reliability of nucleic acids is threatened at high temperatures either by strand separation or by chemical damage of the nucleotide constituents or at the extreme by breakage of backbone phosphodiester bonds (Grogan, 1998; Daniel & Cowan, 2000). Thus, a possible adaptation mechanism of nucleic Phosphoprotein phosphatase acids to thermophilic or hyperthermophilic conditions would be an increase in the GC content. Previous studies have shown, and our analysis with a bunch of thermophilic, hyperthermophilic, mesophilic and psychrophilic genomes confirm, that there is a strong positive correlation between the GC content of the tRNAs with OGT (r=0.85, P<0.00001). On the contrary, the GC content of genomic DNA far less

correlated with the growth temperature (r=0.25, P=0.05). However, a strong positive correlation has also been found between the GC content of rRNA with that of OGT for the organisms chosen for the present study (r=0.868, P<0.00001), suggesting that rRNA correlate better with tRNA than with the genomic DNA. One explanation could be that cellular DNA is in a topologically closed conformation, and denaturation will not result in two independent single-stranded molecules, but in a random-coiled structure with interwined strands (Marguet & Forterre, 2001). As a result, topologically closed DNA is much resistant to denaturation compared with open conformation. The tRNA molecules are not permanently integrated into larger macromolecular complexes. Therefore, in adapting to high temperatures, they must have developed mechanisms for intrinsic stabilization. Part of the stabilization energy may originate from an increased GC content.