The bacterial transposon Tn7 causes premature polyadenylation of mRNA in eukaryotic organisms: TAGKO mutagenesis in filamentous fungi

TAGKO is a Tn7-based transposition system for genome wide mutagenesis in filamentous fungi. The effects of transposon insertion on the expression of TAGKO alleles were examined in Magnaporthe grisea and Mycosphaerella graminicola. Northern analysis showed that stable, truncated transcripts were expressed in the TAGKO mutants. Mapping of the 3′-ends of TAGKO cDNAs revealed that they all contain Tn7 end sequences, regardless of the transposon orientation. Polyadenylation signals characteristic of eukaryotic genes, preceded by stop codons in all frames, are located in both ends of the bacterial transposon. Thus, TAGKO transcripts are prematurely polyadenylated, and truncated proteins are predicted to be translated in the fungal mutants. Depending on the extent of protein truncation, TAGKO mutations in HPD4 (encoding p-hydroxyphenylpyruvate dioxygenase) resulted in tyrosine sensitivity in the two fungi. Similarly, a particular M.grisea CBS1 (encoding cystathionine β-synthase) TAGKO cDNA failed to complement cysteine auxotrophy in a yeast CBS mutant. TAGKO, therefore, represents a useful tool for in vivo study of truncated gene products in filamentous fungi.postprin

The effect of iron-oxidising bacteria on the stability of gold (I) thiosulphate complex

An acidophilic, iron-oxidising bacterial consortium was collected from Rio Tinto near Berrocal, Spain. This primary enriched culture was used to examine the effect of acidophilic iron-oxidising bacteria on the stability of soluble gold (I) thiosulphate. Stationary phase cultures and separate components of the cultures (i.e., aqueous ferric iron, iron oxyhydroxide precipitates and non-mineralised bacterial cells) were exposed to gold (I) thiosulphate solutions forming different experimental-gold systems. These experimental systems rapidly removed gold from solutions containing 0.002 mM–20 mM gold thiosulphate. Scanning and transmission electron microscopy demonstrated that the different culture fractions immobilised gold differently: the entire bacterial culture-gold systems precipitated 100 nm-size gold colloids; aqueous ferric iron–gold systems precipitated colloidal gold sulphide that ranged in diameter from 200 nm to 2 μm; iron oxyhydroxide-gold systems precipitated 5 nm-size gold sulphide colloids; and the bacteria-gold systems precipitated gold colloids ~ 2 nm in size along the bacterial cell envelope. Aqueous and solid ferric iron was critical in the destabilisation of the gold (I) thiosulphate complex. Analysis of the entire bacterial culture-, aqueous ferric iron- and iron oxyhydroxide-gold systems exposed to 2 mM gold using X-ray absorption near edge spectroscopy demonstrated that Au+ was immobilised from solution as gold sulphide (Au2S). The reaction between iron-oxidising bacteria and their ferric iron by-products with gold (I) thiosulphate demonstrated that thiosulphate ions would be an unstable gold complexing ligand in nature. Gold (I) thiosulphate is intuitively transformed into nanometer-scale gold sulphide or elemental gold within natural, acidic weathering environments with the potential to precipitate gold in jarosite that can subsequently be preserved in gossans over geological time

Theology, News and Notes - Vol. 20, No. 02

Theology News & Notes was a theological journal published by Fuller Theological Seminary from 1954 through 2014.https://digitalcommons.fuller.edu/tnn/1046/thumbnail.jp

Westernmost Grand Canyon incision: Testing thermochronometric resolution

The timing of carving of Grand Canyon has been debated for over 100 years with competing endmember hypotheses advocating for either a 70 Ma (“old”) or <6 Ma (“young”) Grand Canyon. Several geological constraints appear to support a “young” canyon model, but thermochronometric measures of cooling history and corresponding estimates of landscape evolution have been in debate. In particular, 4He/3He thermochronometric data record the distribution of radiogenic 4He (from the 238U, 235U and 232Th decay series) within an individual apatite crystal and thus are highly sensitive to the thermal history corresponding to landscape evolution. However, there are several complicating factors that make interpreting such data challenging in geologic scenarios involving reheating. Here, we analyze new data that provide measures of the cooling of basement rocks at the base of westernmost Grand Canyon, and use these data as a testbed for exploring the resolving power and limitations of 4He/3He data in general. We explore a range of thermal histories and find that these data are most consistent with a “young” Grand Canyon. A problem with the recovered thermal history, however, is that burial temperatures are under predicted based on sedimentological evidence. A solution to this problem is to increase the resistance of alpha recoil damage to annealing, thus modifying He diffusion kinetics, allowing for higher temperatures throughout the thermal history. This limitation in quantifying radiation damage (and hence crystal retentivity) introduces non-uniqueness to interpreting time–temperature paths in rocks that resided in the apatite helium partial retention zone for long durations. Another source of non-uniqueness, is due to unknown U and Th distributions within crystals. We show that for highly zoned with a decrease in effective U of 20 ppm over the outer 80% of the radius of the crystal, the 4He/3He data could be consistent with an “old” canyon model. To reduce this non-uniqueness, we obtain U and Th zonation information for separate crystals from the same rock sample through LA-ICP-MS analysis. The observed U and Th distributions are relatively uniform and not strongly zoned, thus supporting a “young” canyon model interpretation of the 4He/3He data. Furthermore, we show that for the mapped zonation, the difference between predicted 4He/3He data for a uniform crystal and a 3D model of the crystal are minimal, highlighting that zonation is unlikely to lead us to falsely infer an “old” Grand Canyon

Particle Filtering for Sequential Spacecraft Attitude Estimation

A new spacecraft attitude estimation approach using particle filtering is derived. Based on sequential Monte Carlo simulation, the particle filter approximately represents the prob-ability distribution of the state vector with random samples. The filter formulation is based on the star camera measurements using a gyro-based or attitude dynamics-based model for attitude propagation. Modified Rodrigues parameters are used for attitude parametriza-tion when the sample mean and covariance of the attitude are computed. The ambiguity problem associated with the modified Rodrigues parameters in the mean and covariance computation is addressed as well. By using the uniform attitude probability distribution as the initial attitude distribution and using a gradually decreasing measurement variance in the computation of the importance weights, the particle filter based attitude estimator possesses global convergence properties. Simulation results indicate that the particular particle filter, known as bootstrap filter, with as many as 2000 particles is able to converge from arbitrary initial attitude error and initial gyro bias errors as large as 4500 degrees per hour per axis. I

Time-optimal synthesis of unitary transformations in coupled fast and slow qubit system

In this paper, we study time-optimal control problems related to system of two coupled qubits where the time scales involved in performing unitary transformations on each qubit are significantly different. In particular, we address the case where unitary transformations produced by evolutions of the coupling take much longer time as compared to the time required to produce unitary transformations on the first qubit but much shorter time as compared to the time to produce unitary transformations on the second qubit. We present a canonical decomposition of SU(4) in terms of the subgroup SU(2)xSU(2)xU(1), which is natural in understanding the time-optimal control problem of such a coupled qubit system with significantly different time scales. A typical setting involves dynamics of a coupled electron-nuclear spin system in pulsed electron paramagnetic resonance experiments at high fields. Using the proposed canonical decomposition, we give time-optimal control algorithms to synthesize various unitary transformations of interest in coherent spectroscopy and quantum information processing.Comment: 8 pages, 3 figure