Temperature Sensitive Polymer

Bacteriophages grown on Caulobacter vibrioides strain CB15 have reduced plating efficiency on other Caulobacter strains. To determine the cause of this reduced plating efficiency, we performed a series of experiments that demonstrated that the reduced plating efficiency is due to a novel set of restriction and modification (RM) enzymes that are present in most of the Caulobacter strains that we tested. We then demonstrated that one of these RM systems recognizes the nucleotide sequence 5 ′-ATNNAT-3 ′. A careful inspection of the genome nucleotide sequences of each of the strains revealed that the genes coding for these RM enzymes have not been annotated or identified, suggesting that the proteins may differ from the common types of bacterial restriction and modification enzymes. In addition, the host strain NA1000 contains a 26 kb mobile element that provides resistance to incoming phages.

Vertical column amounts of nitrogen dioxide, C(NO2), are derived from ground‐based direct solar irradiance measurements using two new and independently developed spectrometer systems, Pandora (Goddard Space Flight Center) and MFDOAS (Washington State University). We discuss the advantages of C(NO2) retrievals based on Direct Sun ‐ Differential Optical Absorption Spectroscopy (DS‐DOAS). The C(NO2) data are presented from field campaigns using Pandora at Aristotle University (AUTH), Thessaloniki, Greece; a second field campaign involving both new instruments at Goddard Space Flight Center (GSFC), Greenbelt, Maryland; a Pandora time series from December 2006 to October 2008 at GSFC; and a MFDOAS time series for spring 2008 at Pacific Northwest National Laboratory (PNNL), Richland, Washington. Pandora and MFDOAS were compared at GFSC and found to closely agree, with both instruments having a clear‐sky precision of 0.01 DU (1 DU = 2.67 × 1016 molecules/cm2) and a nominal accuracy of 0.1 ...

The Ffh protein of Escherichia coli is a 48-kDa polypeptide that is homologous to the SRP54 subunit of the eukaryotic signal recognition particle (SRP). Efforts to understand the function of Ffh in bacteria have depended largely on the use of E. coli strains that allow depletion of the wild-type gene product. As an alternative approach to studying Ffh, a temperature-sensitive ffh mutant was isolated. The ffh-10(Ts) mutation results in two amino acid changes in conserved regions of the Ffh protein, and characterization of the mutant revealed that the cells rapidly lose viability at the nonpermissive temperature of 42°C as well as show reduced growth at the permissive temperature of 30°C. While the ffh mutant is defective in insertion of inner membrane proteins, the export of proteins with cleavable signal sequences is not impaired. The mutant also shows elevated expression of heat shock proteins and accumulates insoluble proteins, especially at 42°C. It was further observed that the temperature sensitivity of the ffh mutant was suppressed by overproduction of 4.5S RNA, the RNA component of the bacterial SRP, by stabilizing the thermolabile protein. Collectively, these results are consistent with a model in which Ffh is required only for localization of proteins integral to the cytoplasmic membrane and suggest new genetic approaches to the study of how the structure of the SRP contributes to its function.

ABSTRACTThe Ffh protein ofEscherichia coliis a 48-kDa polypeptide that is homologous to the SRP54 subunit of the eukaryotic signal recognition particle (SRP). Efforts to understand the function of Ffh in bacteria have depended largely on the use ofE. colistrains that allow depletion of the wild-type gene product. As an alternative approach to studying Ffh, a temperature-sensitiveffhmutant was isolated. Theffh-10(Ts) mutation results in two amino acid changes in conserved regions of the Ffh protein, and characterization of the mutant revealed that the cells rapidly lose viability at the nonpermissive temperature of 42°C as well as show reduced growth at the permissive temperature of 30°C. While theffhmutant is defective in insertion of inner membrane proteins, the export of proteins with cleavable signal sequences is not impaired. The mutant also shows elevated expression of heat shock proteins and accumulates insoluble proteins, especially at 42°C. It was further observed that the t...

Common patterns of climatic variability across the Western Americas are modulated by tropical and extra-tropical oscillatory modes operating at different temporal scales. Interannual climatic variations in the tropics and subtropics of the Western Americas are largely regulated by El Niño-Southern Oscillation (ENSO), whereas decadal-scale variations are induced by long-term Pacific modes of climate variability such as the Pacific Decadal Oscillation (PDO). At higher latitudes, climate variations are dominated by oscillations in the Annular Modes (the Arctic and Antarctic Oscillations) which show both interannual and longer-scale temporal oscillations. Here we use a recently-developed network of tree-ring chronologies to document past climatic variations along the length of the Western Cordilleras. The local and regional characterization of the relationships between climate and tree-growth provide the basis to compare climatic variations in temperature-and precipitation-sensitive records in the Western Americas over the past 3-4 centuries. Upper-elevation records from tree-ring sites in the Gulf of Alaska and Patagonia reveal the occurrence of concurrent decade-scale oscillations in temperature during the last 400 years modulated by PDO. The most recent fluctuation from the cold-to the warm-phase of the PDO in the mid 1970s induced marked changes in R. Villalba

Mutants lacking pyruvate decarboxylase cannot grow on glucose. We have isolated three different complementation groups of extragenic suppressors that suppress mutations in pdc2, a regulatory locus required for the synthesis of the glycolytic enzyme pyruvate decarboxylase. The most frequent of these is a recessive mutation in the structural gene PFK1 of the soluble phosphofructokinase. The other class XSP18 (extragenic suppressor of pdc2) is a dominant temperature-sensitive suppressor that allows the cells to grow on glucose only at 30° but not at 36°. It also affects the normal induction of the glucose-inducible enolase 2, which can be rescued by providing a copy of wild-type xsp18 in trans-heterozygotes. The pyruvate decarboxylase activity in the triple mutant pdc2 pfk1 XSP18 is nearly equal to the sum of the activities in the two double mutants pdc2 pfk1 and pdc2 XSP18, respectively. This implies that the two suppressors act through independent pathways or that there is no coopera...

Research on plant responses to temperature stress is receiving increased interest due to the growing awareness about global warming. High and low temperature stresses help establish the narrow geographic distribution of some cultivated plants, the limited geographic extension of some other economically nutritionally important species, and also induce irregular bearing for some species. However, the understanding of plant responses to temperature stress lags behind other biotic and abiotic stresses probably due to the complex response at the molecular, cellular, and organismal level. Temperature stress affects, indeed, many developmental processes during the plant's life cycle. However, the reproductive stage, the outcome of which represents the economic value for many cultivated plants, is especially vulnerable. Here the effect of low and high temperature stresses during the flowering phase is reviewed in flowering plants in an attempt to unravel sensitive stages that are behind irregular cropping. The review presents detailed findings from 33 previously published reports spanning 19 different flowering plant species. Both the male and female organs of the flower are especially sensitive to temperature fluctuations both during their development before pollination and during the post-pollination stage. The effect of temperature stress is, however, obscured by the complex male-female interaction superimposed on the individual behavior of each organ. Interestingly, a review of the literature on this topic shows that genetic variation does exist in reproductive behavior under temperature fluctuations. This genetic diversity must be preserved and characterized in further detail to understand how plants naturally cope with changing environmental conditions, which will, undoubtedly, help us to design better strategies to face current and future challenging temperature fluctuations.

The paper explores to which extent narrative documentary records on wine production in Central Europe can be used as a proxy for summer temperatures. Here, we compiled 11 regional series spanning from the early 15th century to 1988. We detrended the data to adjust for long-term biases such as warfare-related population decline. The homogenised regional series were subsequently merged into three supra-regional series: (1) the Mosel series, starting in 1416 and consisting of data from the former city-republic of Metz (France) and the Grand Duchy of Luxembourg; (2) the series for Germany, starting in 1511 and mainly originating from the former city-state of Heilbronn; and (3) the third series, starting in 1529 and representing production on the Swiss Plateau. The residuals of the supra-regional yield series were averaged, divided into seven classes, and multiplied by five quality classes. Yield quality indices (YQI) varying between 35 (large and excellent) and 1 (small and undrinkable) significantly correlated with temperatures between May and July. Regression analysis of the composite series revealed that yield and quality primarily depend on the climate conditions from May to July as well as on those in June of the previous year. Crops with a YQI > 28 (rated "good" by traditional winegrowers) were related to aboveaverage May-July temperatures, early grape harvest dates and high tree-ring maximum latewood density values resulting from frequent anticyclonic weather situations. Crops with YQI > 10 could not be uncritically assigned to cold summers since severe winter conditions, and spring frosts sometimes substantially reduced yields without affecting quality, particularly during the Little Ice Age in the marginal Mosel and German areas. Extreme yield fluctuations challenged winegrowing communities. Overproduction induced wastefulness, while crop failures sometimes triggered witch hunts.

Temperature-sensitive (ts) mutant viruses have been useful for the study of replication processes in many viral systems. To determine how our panel of MHV-JHM-derived RNA Ϫ ts mutants (Robb et al., 1979) is genetically related to other panels of MHV RNA Ϫ ts mutants, we tested our mutants for complementation with representatives from two different sets of MHV-A59 ts mutants . These three ts mutant panels together comprise eight genetically distinct complementation groups. Considerable genetic similarity was observed among the three mutant panels. Only three complementation classes are unique to their particular mutant panel, and genetically equivalent mutants were not observed within the other two mutant panels. There are two overlapping complementation groups between the mutant sets derived from MHV-A59 and four overlapping complementation classes between the MHV-JHM panel and the MHV-A59 panels. Two complementation groups had representative mutants in all three mutant panels. One of these latter complementation classes demonstrated nonreciprocal complementation patterns consistent with intragenic complementation.

Sr/Ca ratios were measured on eight species of planktonic foraminifera from a core top transect of the North Atlantic. Five of the species (Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina pachyderma, Globigerinoides sacculifer, Globigerinella siphonifera) show remarkably little within-species variability in Sr/Ca (1.2 ± 0.1%). Three globorotaliid species (Globorotalia hirsuta, Globorotalia inflata, Globorotalia truncatulinoides) show somewhat greater variability (3-7%). Interspecies variations are of 10%. The variability in globorotaliid Sr/Ca is explained either by a greater temperature sensitivity than for other species or by depth-dependent dissolution. Other than this effect, the overwhelming control on foraminiferal Sr/Ca appears to be seawater Sr/Ca. In contrast, time series Sr/Ca records of four species from a North Atlantic sediment core over a glacial-interglacial cycle show very significant differences. N. pachyderma shows large-amplitude changes in Sr/Ca (9.7%), in phase with d 18 O, whereas G. ruber shows the smallest amplitude changes (2.6%) out of phase with d 18 O and most similar to model predictions for temporal changes in seawater Sr/Ca. Records of G. inflata and G. bulloides are intermediate (amplitude changes of 3.3-4.7%) and out of phase with d 18 O. The lack of coherence in the time series records between the species shows that factors in additional to changing seawater Sr/Ca must affect planktonic foraminiferal Sr/Ca.

Poly(N-isopropylacrylamide) i.e. PNIPAAm is a temperature sensitive smart material which displays a lower critical solution temperature (LCST) at 33-35 o C. At the lower critical solution temperature, the gel changes from hydrophilic to hydrophobic which has significant consequences in cell culturing. The first known measurements of the optical properties i.e. absorption (µ a ) and reduced scattering (µ' s ) coefficients, as a function of temperature, of a series of crosslinked PNIPAAm gels, using an Integrating Sphere setup, is presented at a wavelength of 632.8 nm. These properties showed a direct correlation between the scattering coefficient and the crosslinker density for the gels. The absorption properties correlated well with the known absorption characteristics of these gels.

This study describes the discovery of a new inherited disorder of glycosylation named "CDG-Ik." CDG-Ik (congenital disorder of glycoslyation type Ik) is based on a defect of human mannosyltransferase I (MT-I [MIM 605907]), an enzyme necessary for the elongation of dolichol-linked chitobiose during N-glycan biosynthesis. Mutations in semiconserved regions in the corresponding gene, HMT-1 (yeast homologue, Alg1), in two patients caused drastically reduced enzyme activity, leading to a severe disease with death in early infancy. One patient had a homozygous point mutation (c.773CrT, S258L), whereas the other patient was compound heterozygous for the mutations c.773CrT and c.1025ArC (E342P). Glycosylation and growth of Alg1-deficient PRY56 yeast cells, showing a temperature-sensitive phenotype, could be restored by the human wild-type allele, whereas only slight restoration was observed after transformation with the patients' alleles.

Two closely related bacteriophage, $Cr30 and GCr35, are the first bacteriophage shown to mediate generalized transductim in Caulobacter crescentus. Unlike most other transducing phage, they are virulent and do not form any sort of lysogenic relationship with their host. Howevcr, they are rather inefficient at adsorption, so that transductants have a good chance of survival. The phage particles have a head 80 nm in diamctcr and a cmtmctile tail 140 nm in length. Procedures for growth and transduction with CCr30 are relatively simple; thus, it will be of great value for the genetic analysis of C. crescentus. Tmodel system for the study of differentiation ( SHAPIRO, AGABIAN-KESHI-SHIAN and BENDIS 1971). Unlike the differentiation occurring in other bacteria, Caulobacter differentiates during its normal logarithmic growth cycle. One round of differentiation occurs with the synthesis of a flagellum, pili, and a specific membrane phage receptor just prior to cell division. This cell division. is asymmetric and results in the formation of stalked and swarmer cell types. The stalk cell initiates a second cell cycle immediately, while the swarmer cell must go through a second differentiation before becoming a stalked cell and replicating its DNA. These cell cycle events can be easily observed, and thus Caulobacter is ideal for studies of the regulation of cell morphogenesis. Analysis of the genetic regulation of morphogenesis in Caulobactor will require the development of techniques for the isolation of mutants and for the promotion of genetic exchange between mutants. Procedures for the isolation of nutritional and regulatory mutants of C. crescentus have been developed, and characterization of a number of these mutants is under way (JOHNSON and ELY 1977). Genetic exchange has been shown to occur via conjugation with specific donor strains . We report here a second system of genetic exchange, which is mediated by generalized transducing phage. These bacteriophage are capable of transferring small regions of DNA from one phage-sensitive strain to any other. Thus, they will be quite useful for the genetic analysis of small regions of the C. crescentus chromosome.

Caulobacter crescentus has a penicillinase which precludes the use of penicillin for mutant enrichment. However, two other antibiotics, fosfomycin and D-cycloserine, can be used to enrich for C. crescentus mutants. In enrichment procedures for C . crescentus auxotrophs, spontaneously derived mutants occur at a frequency of 5-10% among the survivors of an enrichment procedure. Consequently, large numbers of mutants are readily obtained without any need for mutagenesis. These mutants are heterogeneous both with regard to the type of mutation and to the nutritional requirement. A similar procedure has been used to isolate temperature-sensitive mutants.

Despite their ubiquity, relatively few bacteriophages have been characterized. Here, we set out to explore Caulobacter bacteriophages (caulophages) in the rhizosphere and characterized Kronos, the first caulophage isolated from the rhizosphere. Kronos is a member of the Siphoviridae family since it has a long flexible tail. In addition, an analysis of the Kronos genome indicated that many of the predicted proteins were distantly-related to those of bacteriophages in the lambdoid family. Consistent with this observation, we were able to demonstrate the presence of cos sites that are similar to those found at ends of lambdoid phage genomes. Moreover, Kronos displayed a relatively rare head and tail morphology compared to other caulophages but was similar to that of the lambdoid phages. Taken together, these data indicate that Kronos is distantly related to lambdoid phages and may represent a new Siphoviridae genus.

Caulobacter crescentus has a penicillinase which precludes the use of penicillin for mutant enrichment. However, two other antibiotics, fosfomycin and D-cycloserine, can be used to enrich for C. crescentus mutants. In enrichment procedures for C . crescentus auxotrophs, spontaneously derived mutants occur at a frequency of 5-10% among the survivors of an enrichment procedure. Consequently, large numbers of mutants are readily obtained without any need for mutagenesis. These mutants are heterogeneous both with regard to the type of mutation and to the nutritional requirement. A similar procedure has been used to isolate temperature-sensitive mutants.

Two closely related bacteriophage, $Cr30 and GCr35, are the first bacteriophage shown to mediate generalized transductim in Caulobacter crescentus. Unlike most other transducing phage, they are virulent and do not form any sort of lysogenic relationship with their host. Howevcr, they are rather inefficient at adsorption, so that transductants have a good chance of survival. The phage particles have a head 80 nm in diamctcr and a cmtmctile tail 140 nm in length. Procedures for growth and transduction with CCr30 are relatively simple; thus, it will be of great value for the genetic analysis of C. crescentus. Tmodel system for the study of differentiation ( SHAPIRO, AGABIAN-KESHI-SHIAN and BENDIS 1971). Unlike the differentiation occurring in other bacteria, Caulobacter differentiates during its normal logarithmic growth cycle. One round of differentiation occurs with the synthesis of a flagellum, pili, and a specific membrane phage receptor just prior to cell division. This cell division. is asymmetric and results in the formation of stalked and swarmer cell types. The stalk cell initiates a second cell cycle immediately, while the swarmer cell must go through a second differentiation before becoming a stalked cell and replicating its DNA. These cell cycle events can be easily observed, and thus Caulobacter is ideal for studies of the regulation of cell morphogenesis. Analysis of the genetic regulation of morphogenesis in Caulobactor will require the development of techniques for the isolation of mutants and for the promotion of genetic exchange between mutants. Procedures for the isolation of nutritional and regulatory mutants of C. crescentus have been developed, and characterization of a number of these mutants is under way (JOHNSON and ELY 1977). Genetic exchange has been shown to occur via conjugation with specific donor strains . We report here a second system of genetic exchange, which is mediated by generalized transducing phage. These bacteriophage are capable of transferring small regions of DNA from one phage-sensitive strain to any other. Thus, they will be quite useful for the genetic analysis of small regions of the C. crescentus chromosome.

Two closely related bacteriophage, varphiCr30 and varphiCr35, are the first bacteriophage shown to mediate generalized transduction in Caulobacter crescentus. Unlike most other transducing phage, they are virulent and do not form any sort of lysogenic relationship with their host. However, they are rather inefficient at adsorption, so that transductants have a good chance of survival. The phage particles have a head 80 nm in diameter and a contractile tail 140 nm in length. Procedures for growth and transduction with varphiCr30 are relatively simple; thus, it will be of great value for the genetic analysis of C. crescentus.

Caulobacter crescentus has a penicillinase which precludes the use of penicillin for mutant enrichment. However, two other antibiotics, fosfomycin and D-cycloserine, can be enrich for C. crescentus mutants. In enrichment procedures for C. crescentus auxotrophs, spontaneously derived mutants occur at a frequency of 5-10% among the survivors of an enrichment procedure. Consequently, large numbers of mutants are readily obtained without any need for mutagenesis. These mutants are heterogeneous both with regard to the type of mutation and to the nutritional requirement. A similar procedure has been used to isolate temperature-sensitive mutants.

Mutations in more than 30 genes affect motility in Caulobacter crescentus. We have determined the chromosomal map locations for 27 genes involved in flagellar morphogenesis (fla), three genes involved in flagellar function (mot), and three genes that have a pleiotropic effect on both motility and bacteriophage resistance (ple). Three multigene clusters have been detected at widely separated chromosomal locations, but in addition, there are 12 fla and mot genes that are found at eight additional sites scattered around the C. crescentus chromosome. Thus, there is more scatter of genes involved in flagellar structure and function than has been observed in other bacterial systems.

Global temperature has been increased by 0.6 °C over the past century and is predicted to increase by 1.4-5.8 °C by the end of this century. It is unclear what impacts global warming will have on tallgrass species. In the present study, we examined leaf net photosynthetic rate (P n ) and leaf respiration rate in darkness (R d ) of Aster ericoides (L.) Nesom, Ambrosia psilostachya DC., Helianthus mollis Lam., and Sorghastrum nutans (L.) Nash in response to experimental warming in a tallgrass prairie ecosystem of the Great Plains, USA, in the autumn (fall) of 2000 and through 2001. Warming has been implemented with infrared heaters since 21 November 1999. The P n increased significantly in spring, decreased in early fall, and did not change in summer and late fall in the four species under warming compared with control. The R d of the four species increased significantly until mid-summer and then did not change under warming. Measured temperature-response curves of P n showed that warming increased the optimum temperature of P n (T opt ) by 2.32 and 4.59 °C for H. mollis and S. nutans, respectively, in August, whereas there were no changes in May and September, and A. ericoides and A. psilostachya also showed no changes in any of the 3 months. However, P n at optimum temperature (P opt ) showed downregulation in September and no regulation in May and August for all four species. The temperature-response curves of R d illustrate that the temperature sensitivity of R d , Q 10 , was lower in the warmed plots compared with the control plots, except for A. ericoides in August, whereas there were no changes in May and September for all four species. The results of the present study indicate that photosynthetic and respiratory acclimation varies with species and among seasons, occurring in the mid-growing season and not in the early and late growing seasons.

1] Changes in soil respiration, one of the major fluxes of global carbon cycling, could significantly slow down or accelerate the increase in atmospheric CO 2 , with consequent feedbacks to climate change. It is critical to understand how substrate availability regulates soil respiration in projecting the response of carbon cycling to changed climate. We conducted a clipping and shading experiment for 1 year in a tallgrass prairie of the Great Plains, United States, to manipulate substrate supply to soil respiration. Our results showed that reduced substrate supply under clipping and/or shading significantly decreased soil respiration at all the timescales (diurnal, transient, and annual) irrespective of the minor concurrent changes in soil temperature and moisture. Annual mean soil respiration decreased significantly by 33, 23, and 43% for the clipping, shading, and clipping plus shading treatments, respectively. Temperature sensitivity of soil respiration decreased from 1.93 in the control plots to 1.88, 1.75, and 1.83 in the clipped, shaded, and clipped plus shaded plots, respectively. Rhizosphere respiration, respiration from decomposition of aboveground litter, and respiration from oxidation of soil organic matter and dead roots accounted for 30, 14, and 56% of annual mean soil respiration, respectively. Rhizosphere respiration was more sensitive to temperature than the other two components. Our results suggest a critical role of substrate supply in regulating soil respiration and its temperature sensitivity.

The tumor suppressor protein BRCA1 has been shown to enhance p53 transcription, whereas activated p53 represses BRCA1 transcription. To further understand the functional interaction of these proteins, we investigated the role of BRCA1 in p53-induced phenotypes. We found that BRCA1 when subjected to forced expression acts synergistically with wild-type p53, resulting in irreversible growth arrest, as shown by VhD mouse fibroblast cells expressing a temperature-sensitive mutant of p53. Furthermore, reintroduction of both BRCA1 and p53 into BRCA1(À/À)/p53(À/À) mouse embryonic fibroblasts markedly increased the senescence phenotype compared to that induced by p53 alone. In particular, we found that BRCA1 expression attenuated p53-mediated cell death in response to c-irradiation. Moreover, microarray screening of 11 000 murine genes demonstrated that a set of genes upregulated by p53 is enhanced by coexpression of BRCA1 and p53, suggesting that BRCA1 and p53 exert a promoter selectivity leading to a specific phenotype. Taken together, our results provide evidence that BRCA1 is involved in p53-mediated growth suppression rather than apoptosis.

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A persistently-infected neuroblastoma culture [Neuro-2A(JHMV)] was established with the murine hepatitis virus JHM [MHV-JHM]. After t00 days of passage, the endogenous virus [Neuro-2A(JHMV)end] released by this culture was unable to induce the syncytia typical of MHV-JHM and the endogenous virus was not temperature-sensitive. The Neuro-2A (JHMV) culture was cured of virus production by passage under neutralizing antibody [Neuro-2A (JHMV)Ab]. The Neuro-2A (JHMV) and the Neuro-2A (JHMV)Ab cultures were as susceptible to heterologous infection with mengovirus and vesicular stomatitis virus as the uninfected Neuro-2A culture. However, the Neuro-2A(JHMV) and Neuro-2A(JHMV)Ab cultures were partiMly resistant to homologous superinfection by MHV-JHM and the closely related MHV-A59. Virus related to MHV-JHM was rescued from the antibody-cured cells by cell fusion. The synthesis of MHV-JHM specific antigens by Neuro-2A (JHMV) cells, Neuro-2A (JHMV)Ab cells and 17C1-1 cells infected by Neuro-2A(JHMV)end was studied by SDS-PAGE. The genomic RNAs of MHV-JHM and Neuro-2A(JHMV) end were compared by o]igonucleotide mapping. The results of the protein and RNA studies indicated that the genome of Neuro-2A(JHMV)end was substantially modified from the genome of MHV-JHM, but the modifications did not significantly alter the molecular size of the virM-specific proteins. 22*