Characterization of a Paenibacillus cell-associated xylanase with high activity on aryl-xylosides: a new subclass of family 10 xylanases

The sequence of gene xynB encoding xylanase B from Paenibacillus sp. BP-23 was determined. It revealed an open reading frame of 999 nucleotides encoding a protein of 38,561 Da. The deduced amino acid sequence of xylanase B shows that the N-terminal region of the enzyme lacks the features of a signal peptide. When the xylan-degrading system of Paenibacillus sp. BP-23 was analysed in zymograms, it revealed that xylanase B was not secreted to the extracellular medium but instead remained cell-associated, even in late stationary-phase cultures. When xynB was expressed in a Bacillus subtilis secreting host, it also remained associated with the cells. Sequence homology analysis showed that xylanase B from Paenibacillus sp. BP-23 belongs to family 10 glycosyl hydrolases, exhibiting a distinctive high homology to six xylanases of this family. The homologous enzymes were also found to be devoid of a signal peptide and seem to constitute, together with xylanase B, a separate group of enzymes. They all have two conserved amino acid regions not found in the other family 10 xylanases, and cluster in a separate group after dendrogram analysis. We propose that these enzymes constitute a new subclass of family 10 xylanases, that are cell-associated, and that hydrolyse the xylooligosaccharides resulting from extracellular xylan hydrolysis. Xylanase B shows similar specific activity on aryl-xylosides and xylans. This can be correlated to some, not yet identified, trait of catalytic activity of the enzyme on plant xylan.     

Analysis of the growth of Chlorella cultures using electronically measured cell-volume distribution data

Cell-number density and cell-volume distribution data were obtained from cultures of Chlorella fusca var. vacuolata Shihira & Krauss growing under both continuous and periodic illumination. Mean, median and modal cell-volumes were calculated from the cell-volume distributions and a high correlation shown between mean and median values, whilst mean and modal values did not correlate well. It was concluded that where the computation necessary for deriving mean cell-volumes was not practicable, the median cell-volume was the next most useful statistic.

Synchrony indices of discontinuously illuminated cultures gave similar values when based on change in cell-number and change in mean cell-volume. Cultures under continuous illumination showed synchronous divisions at the beginning of growth. These divisions gave high values of a synchrony index based on change in cell-number, but low values of an index based on change in mean cell-volume. It was concluded that mean cell-volume data are more sensitive to the occurrence of unbalanced growth than analysis of cell-number data.     

The Importance of the Human Footprint in Shaping the Global Distribution of Terrestrial,Freshwater and Marine Invaders

Human activities such as transport, trade and tourism are likely to influence the spatial distribution of non-native species and yet, Species Distribution Models (SDMs) that aim to predict the future broad scale distribution of invaders often rely on environmental (e.g. climatic) information only. This study investigates if and to what extent do human activities that directly or indirectly influence nature (hereafter the human footprint) affect the global distribution of invasive species in terrestrial, freshwater and marine ecosystems. We selected 72 species including terrestrial plants, terrestrial animals, freshwater and marine invasive species of concern in a focus area located in NW Europe (encompassing Great Britain, France, The Netherlands and Belgium). Species Distribution Models were calibrated with the global occurrence of species and a set of high-resolution (9×9 km) environmental (e.g. topography, climate, geology) layers and human footprint proxies (e.g. the human influence index, population density, road proximity). Our analyses suggest that the global occurrence of a wide range of invaders is primarily limited by climate. Temperature tolerance was the most important factor and explained on average 42% of species distribution. Nevertheless, factors related to the human footprint explained a substantial amount (23% on average) of species distributions. When global models were projected into the focus area, spatial predictions integrating the human footprint featured the highest cumulative risk scores close to transport networks (proxy for invasion pathways) and in habitats with a high human influence index (proxy for propagule pressure). We conclude that human related information–currently available in the form of easily accessible maps and databases—should be routinely implemented into predictive frameworks to inform upon policies to prevent and manage invasions. Otherwise we might be seriously underestimating the species and areas under highest risk of future invasions.     

CRISPR RNA-Dependent Binding and Cleavage of Endogenous RNAs by the Campylobacter jejuni Cas9

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T cells are crucial for the anti-metastatic effect of anti-epidermal growth factor receptor antibodies

Experimental evidences supporting the epidermal growth factor receptor (EGFR) as an important molecule for tumor metastasis had been accumulated. Currently, anti-EGFR monoclonal antibodies (mAbs) constitute a promising approach for the treatment of patients with metastatic tumors. However, the mechanisms associated with the potent anti-metastatic effect of these mAbs have not been completely elucidated due to the lack of appropriate syngeneic preclinical models. In this paper, we have investigated the effects of 7A7, an antibody specific to murine EGFR, on the metastatic properties of D122 murine lung carcinoma. 7A7 mAb significantly impaired metastatic spread of D122 cells in C57BL/6 mice by direct anti-proliferative and pro-apoptotic effects on tumor metastasis. 7A7 mAb capacity to inhibit EGFR activation on D122 cells could contribute to its anti-metastatic effect. In addition, 7A7 mAb was able to induce in vitro antibody-dependent cell-mediated cytotoxicity on D122 cells. Interestingly, 7A7 mAb treatment increased the number of natural killer cells, T lymphocytes and dendritic cells infiltrating the metastatic sites. More strikingly, depletion of CD8⁺ and CD4⁺ T cells in vivo completely abrogated the 7A7 mAb anti-metastatic activity whereas function of natural killer cells was irrelevant. This study supports an in vivo role for T cell response in the mechanism of action of anti-EGFR mAbs, suggesting the induction of an adjuvant effect. This work was supported by the Cuban Government.     

Effects of chemical and botanical insecticides used for locust control on Metarhizium anisopliae var. acridum conidia after short- to medium-term storage at 30°C

The short- to medium-term viability and growth of Metarhizium anisopliae var. acridum conidia were investigated when combined with six insecticides, at three different concentrations. All of the insecticides used in this study were suitable for immediate spraying with M. anisopliae var. acridum conidia except for fenitrothion. Fipronil, teflubenzuron, and fenitrothion formulations significantly reduced conidial viability over time. The 10% teflubenzuron treatment caused loss of viability relatively quickly with 9.9% germination after 28 days. Mycelial growth was affected by all the treatments except fenitrothion.     

The N2A region of titin has a unique structural configuration

The N2A segment of titin is a main signaling hub in the sarcomeric I-band that recruits various signaling factors and processing enzymes. It has also been proposed to play a role in force production through its Ca²⁺-regulated association with actin. However, the molecular basis by which N2A performs these functions selectively within the repetitive and extensive titin chain remains poorly understood. Here, we analyze the structure of N2A components and their association with F-actin. Specifically, we characterized the structure of its Ig domains by elucidating the atomic structure of the I81-I83 tandem using x-ray crystallography and computing a homology model for I80. Structural data revealed these domains to present heterogeneous and divergent Ig folds, where I81 and I83 have unique loop structures. Notably, the I81-I83 tandem has a distinct rotational chain arrangement that confers it a unique multi-domain topography. However, we could not identify specific Ca²⁺-binding sites in these Ig domains, nor evidence of the association of titin N2A components with F-actin in transfected C2C12 myoblasts or C2C12-derived myotubes. In addition, F-actin cosedimentation assays failed to reveal binding to N2A. We conclude that N2A has a unique architecture that predictably supports its selective recruitment of binding partners in signaling, but that its mechanical role through interaction with F-actin awaits validation.