A gradient‐forming MipZ protein mediating the control of cell division in the magnetotactic bacterium Magnetospirillum gryphiswaldense

Cell division needs to be tightly regulated and closely coordinated with other cellular processes to ensure the generation of fully viable offspring. Here, we investigate division site placement by the cell division regulator MipZ in the alphaproteobacterium Magnetospirillum gryphiswaldense, a species that forms linear chains of magnetosomes to navigate within the geomagnetic field. We show that M. gryphiswaldense contains two MipZ homologs, termed MipZ1 and MipZ2. MipZ2 localizes to the division site, but its absence does not cause any obvious phenotype. MipZ1, by contrast, forms a dynamic bipolar gradient, and its deletion or overproduction cause cell filamentation, suggesting an important role in cell division. The monomeric form of MipZ1 interacts with the chromosome partitioning protein ParB, whereas its ATP‐dependent dimeric form shows non‐specific DNA‐binding activity. Notably, both the dimeric and, to a lesser extent, the monomeric form inhibit FtsZ polymerization in vitro. MipZ1 thus represents a canonical gradient‐forming MipZ homolog that critically contributes to the spatiotemporal control of FtsZ ring formation. Collectively, our findings add to the view that the regulatory role of MipZ proteins in cell division is conserved among many alphaproteobacteria. However, their number and biochemical properties may have adapted to the specific needs of the host organism.     

Trace Element Composition of Selected Fertilizers Used in Chile: Phosphorus Fertilizers as a Source of Long-Term Soil Contamination

Anthropogenic activities like agriculture have resulted in increased concentrations of some trace elements of toxicological and environmental concern in soils. Application of fertilizers has been one of the major inputs of these contaminants to agricultural soils in developing countries. Twenty-two fertilizers, including straight nitrogen (N), phosphorus (P), potassium (K), and NK fertilizers and micronutrient sources, were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) for arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn). As expected, the trace element content of fertilizers was highly variable and related to the origin of the material. Phosphorus fertilizers, especially triple superphosphate, presented the highest As, Cd, Cu, Cr, Ni, V, and Zn concentrations. In some of these fertilizers, the Cr, V, and Zn contents reached values greater than 3475 mg kg^?1 of P, and the Cd content (up to 288 mg kg^?1 of P) was several times higher than the regulatory limits of different countries. Some micronutrient sources presented the highest concentrations of Mn and Pb. In the cases of N, K, and NK fertilizers, the trace element concentration was very low, sometimes below the detection limits. In some agricultural systems the input of trace elements such as As and Cd to the soil through P fertilizers application may be higher than the outputs through plant uptake and leaching; therefore the long-term use of these fertilizers may cause the trace element concentration to increase in the plow layer of agricultural soils.     

Cryptophytes: An emerging algal group in the rapidly changing Antarctic Peninsula marine environments

The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11-year (2008–2018) in-situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo-physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo-regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo-regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem.     

Progression of pulmonary tuberculosis and efficiency of bacillus Calmette-Guérin vaccination are genetically controlled via a common sst1-mediated mechanism of innate immunity

Using a mouse model for genetic analysis of host resistance to virulent Mycobacterium tuberculosis, we have identified a genetic locus sst1 on mouse chromosome 1, which controls progression of pulmonary tuberculosis. In vitro, this locus had an effect on macrophage-mediated control of two intracellular bacterial pathogens, M. tuberculosis and Listeria monocytogenes. In this report, we investigated a specific function of the sst1 locus in antituberculosis immunity in vivo, especially its role in control of pulmonary tuberculosis. We found that the sst1 locus affected neither activation of Th1 cytokine-producing T lymphocytes, nor their migration to the lungs, but rather controlled an inducible NO synthase-independent mechanism of innate immunity. Although the sst1(S) macrophages responded to stimulation with IFN-gamma in vitro, their responsiveness to activation by T cells was impaired. Boosting T cell-mediated immunity by live attenuated vaccine Mycobacterium bovis bacillus Calmette-Guérin or the adoptive transfer of mycobacteria-activated CD4(+) T lymphocytes had positive systemic effect, but failed to improve control of tuberculosis infection specifically in the lungs of the sst1(S) animals. Thus, in the mouse model of tuberculosis, a common genetic mechanism of innate immunity mediated control of tuberculosis progression in the lungs and the efficiency of antituberculosis vaccine. Our data suggest that in immunocompetent humans the development of pulmonary tuberculosis and the failure of the existing vaccine to protect against it, in some cases, may be explained by a similar defect in a conserved inducible NO synthase-independent mechanism of innate immunity, either inherited or acquired.     

A Simple Geometrical Pattern for the Branching Distribution of the Bronchial Tree, Useful to Estimate Optimality Departures

The design of the bronchial tree has largely been proposed as a model of optimal design from a physical-functional perspective. However, the distributive function of the airway may be more related to a geometrical than a physical problem. The bronchial tree must distribute a three dimensional volume of inspired air on a two dimensional alveolar surface, included in a limited volume. It is thus valid to ask whether an optimal bronchial tree from a physical perspective is also optimum from a geometrical point of view. In this paper we generate a simple geometric model for the branching pattern of the bronchial tree, deducing relationships that permit estimation of the departures from the geometrical optimum of each bifurcation. We also, for comparative purposes, estimate the departures from the physical optimum. From the geometrical assumptions: i) a symmetrical dichotomic fractal design, ii) with minimum volume and iii) maximum dispersion of the terminal points; and several simulations we suggest that the optimality is characterized by a bifurcation angle theta approximately 60 degrees and a length reduction scale gamma = (1/2)(1/3) = 0.7937. We propose distances from the physical and geometrical optimality defined as Euclidean distances from the expected optima. We show how the advanced relationships and the distances can be used to estimate departures from the optimality in bronchographs of four species. We found lower physical and geometrical departures in the distal zone than those of the proximal zones, as well as lower physical than geometrical departures from optimality.     

A unigene catalogue of 5700 expressed genes in cassava

Two economically important characters, starch content and cassava bacterial blight resistance, were targeted to generate a large collection of cassava ESTs. Two libraries were constructed from cassava root tissues of varieties with high and low starch contents. Other libraries were constructed from plant tissues challenged by the pathogen Xanthomonas axonopodis pv.manihotis. We report here the single pass sequencing of 11 954 cDNA clones from the 5’ ends, including 111 from the 3’ ends. Cluster analysis permitted the identification of a unigene set of 5700 sequences. Sequence analyses permitted the assignment of a putative functional category for 37% of sequences whereas ~ 16% sequences did not show any significant similarity with other proteins present in the database and therefore can be considered as cassava specific genes. A group of genes belonging to a large multigene family was identified. We characterize a set of genes detected only in infected libraries putatively involved in the defense response to pathogen infection. By comparing two libraries obtained from cultivars contrasting in their starch content a group of genes associated to starch biosynthesis and differentially expressed was identified. This is the first large cassava EST resource developed today and publicly available thus making a significant contribution to genomic knowledge of cassava.     

Simulation of behavioral profiles in the plus-maze: A Classification and Regression Tree approach

This article introduces a simulation model of rat behavior in the elevated plus-maze, designed through a Decision trees approach using Classification and Regression algorithms. Starting from the analysis of the behavior performed by a sample of 18 Sprague-Dawley male rats, probabilistic rules describing behavioral patterns of the animals were extracted, and were used as the basis of the model computations. The model adequacy was tested by contrasting a simulated sample against an independent sample of real animals. Statistical tests showed that the simulated sample exhibits similar behaviors to those displayed by the real animals, both in terms of the number of entries to open and close arms as well as in terms of the time spent by the animals in those arms. However, the performance of the model in parameters related to the behavioral patterns was partially satisfactory. Given that previous attempts in the literature have neither include this kind of patterns nor the time as a crucial model parameter, the present model offers a suitable alternative for the computational simulation of this paradigm. Compared with antecedent models, the present simulation produced similar or better results in all the considered parameters. Beyond the goal of establish an appropriate simulational model, extracted rules also reveal important regularities associated to the rat behavior previously ignored by other models, i.e. that specific rat behaviors in the elevated plus-maze are time dependent. These and other important considerations to improve the model performance are discussed.