The effect of temperature on the self-association of S5 and on the association of S5 with S8 as determined by sedimentation equilibrium

Solutions of proteins S5 and S8 from the Escherichia coli 30 S ribosomal subunit have been examined by sedimentation equilibrium methods as a function of temperature for their behavior in solution as isolated components and in mixtures. The standard enthalpy and entropy at 4 °C for the isodesmic self-association of S5 were determined from a study over the temperature range of 3 to 33 °C to be 0.1 ± 0.9 kcal/mol and 18 ± 3 cal/(mol × deg), respectively. The protein S8 remained monomeric over the same range of temperature. The standard enthalpy and entropy at 4 °C for the association of S5 and S8 were determined on mixtures from a study over the temperature range of 3 to 27 °C to be ?0.4 ± 1.6 kcal/mol and 20 ± 6 cal/(mol × deg), respectively. Based on these values and the previously determined standard Gibbs free energies (S. H. Tindall and K. C. Aune, 1981, Biochemistry20, 4861–4866), the driving force for the self-association of S5 and the association of S5 with S8 could be interpreted as being derived from the expulsion of water upon ion pair formation at the interaction sites.     

Warming up the system: higher predator feeding rates but lower energetic efficiencies

Predictions on the consequences of the rapidly increasing atmospheric CO₂ levels and associated climate warming for population dynamics, ecological community structure and ecosystem functioning depend on mechanistic energetic models of temperature effects on populations and their interactions. However, such mechanistic approaches combining warming effects on metabolic (energy loss of organisms) and feeding rates (energy gain by organisms) remain a key, yet elusive, goal. Aiming to fill this void, we studied the metabolic rates and functional responses of three differently sized, predatory ground beetles on one mobile and one more resident prey species across a temperature gradient (5, 10, 15, 20, 25 and 30 °C). Synthesizing metabolic and functional‐response theory, we develop novel mechanistic predictions how predator–prey interaction strengths (i.e., functional responses) should respond to warming. Corroborating prior theory, warming caused strong increases in metabolism and decreases in handling time. Consistent with our novel model, we found increases in predator attack rates on a mobile prey, whereas attack rates on a mostly resident prey remained constant across the temperature gradient. Together, these results provide critically important information that environmental warming generally increases the direct short‐term per capita interaction strengths between predators and their prey as described by functional‐response models. Nevertheless, the several fold stronger increase in metabolism with warming caused decreases in energetic efficiencies (ratio of per capita feeding rate to metabolic rate) for all predator–prey interactions. This implies that warming of natural ecosystems may dampen predator–prey oscillations thus stabilizing their dynamics. The severe long‐term implications; however, include predator starvation due to energetic inefficiency despite abundant resources.     

<Emphasis Type=Italic>Bradyrhizobium japonicum</Emphasis> bacteroid appendages expressed in senescing and argon-treated soybean nodules

Bradyrhizobium japonicum bacteroids in soybean nodules expressed fibrillar appendages during senescence. In both scanning and transmission electron microscopy (SEM and TEM), these structures were observed to connect adjacent bacteroids, and bacteroids to symbiotic membranes. They were 20–25 nm in diameter, 100–2,500 nm in length and were linear, branched, or part of a web-like matrix. Bacteroids expressing appendages were not uniformly distributed, but were abundant within localized regions in the senescing nodule. The root systems of nodulated greenhouse-grown plants flushed with argon induced the appendages at earlier plant ages, and they were more prolific and wide spread than those in untreated nodules. Bradyrhizobium japonicum symbiotic appendages appear to be a response to an environmental niche within senescing nodules.     

Direct sequencing of bacteriophage T4 DNA with a thermostable DNA polymerase

We present a simple and convenient protocol for the direct sequencing of bacteriophage T4 genomic DNA. The method utilizes the thermostable DNA polymerase from Thermus aquaticus (Taq) and 32P-end-labeled oligodeoxyribonucleotide primers to produce extension products that allow the analysis of at least 200 nucleotides (nt) on a single sequencing gel. Single-nt changes in the template were easily detectable following an overnight exposure of the autoradiograms. Comparison of sequences from fully modified T4 DNA containing glucosylated hydroxymethyldeoxycytosine or from templates containing cytosine showed little difference in sequence clarity. These techniques considerably simplify the molecular analysis of T-even bacteriophages and should be compatible with automated sequencing methods which employ 5'-end-labeled primers.     

Complete genome sequence of the aerobic, heterotroph Marinithermus hydrothermalis type strain (T1(T)) from a deep-sea hydrothermal vent chimney

Marinithermus hydrothermalis Sako et al. 2003 is the type species of the monotypic genus Marinithermus. M. hydrothermalis T1(T) was the first isolate within the phylum "Thermus-Deinococcus" to exhibit optimal growth under a salinity equivalent to that of sea water and to have an absolute requirement for NaCl for growth. M. hydrothermalis T1(T) is of interest because it may provide a new insight into the ecological significance of the aerobic, thermophilic decomposers in the circulation of organic compounds in deep-sea hydrothermal vent ecosystems. This is the first completed genome sequence of a member of the genus Marinithermus and the seventh sequence from the family Thermaceae. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,269,167 bp long genome with its 2,251 protein-coding and 59 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.