Antimicrobial Activities of Secondary Metabolites from Model Mosses.

Plants synthetize a large spectrum of secondary metabolites with substantial structural and functional diversity, making them a rich reservoir of new biologically active compounds. Among different plant lineages, the evolutionarily ancient branch of non-vascular plants (Bryophytes) is of particular interest as these organisms produce many unique biologically active compounds with highly promising antibacterial properties. Here, we characterized antibacterial activity of metabolites produced by different ecotypes (strains) of the model mosses Physcomitrium patens and Sphagnum fallax. Ethanol and hexane moss extracts harbor moderate but unstable antibacterial activity, representing polar and non-polar intracellular moss metabolites, respectively. In contrast, high antibacterial activity that was relatively stable was detected in soluble exudate fractions of P. patens moss. Antibacterial activity levels in P. patens exudates significantly increased over four weeks of moss cultivation in liquid culture. Interestingly, secreted moss metabolites are only active against a number of Gram-positive, but not Gram-negative, bacteria. Size fractionation, thermostability and sensitivity to proteinase K assays indicated that the secreted bioactive compounds are relatively small (less than <10 kDa). Further analysis and molecular identification of antibacterial exudate components, combined with bioinformatic analysis of model moss genomes, will be instrumental in the identification of specific genes involved in the bioactive metabolite biosynthesis.

Plasticity, pleiotropy and fitness trade-offs in Arabidopsis genotypes with different telomere lengths.

Telomere length has been implicated in the organismal response to stress, but the underlying mechanisms are unknown. Here we examine the impact of telomere length changes on the responses to three contrasting abiotic environments in Arabidopsis, and measure 32 fitness, developmental, physiological and leaf-level anatomical traits. We report that telomere length in wild-type and short-telomere mutants is resistant to abiotic stress, while the elongated telomeres in ku70 mutants are more plastic. We detected significant pleiotropic effects of telomere length on flowering time and key leaf physiological and anatomical traits. Furthermore, our data reveal a significant genotype by environment (G × E) interaction for reproductive fitness, with the benefits and costs to performance depending on the growth conditions. These results imply that life-history trade-offs between flowering time and reproductive fitness are impacted by telomere length variation. We postulate that telomere length in plants is subject to natural selection imposed by different environments.

In-situ extraction and impregnation of black walnut husk into polyethylene film using supercritical carbon dioxide with an ethanol modifier.

Walnuts are commonly cultivated for their kernel, which is a rich source of antioxidant phenolic compounds. The husk likewise contains antioxidant and antimicrobial compounds, but is typically discarded without further processing. Antioxidant compounds are useful in creating active packaging films, but typically decompose at melt extrusion temperatures in polymer processing. Due to carbon dioxide's low critical point and ability to swell polymer films, supercritical carbon dioxide may be used to impregnate phenolic compounds into polymers. For this study, a novel technique is used to simultaneously produce walnut husk extracts and impregnate the extract into polymer films in the same batch extractor using supercritical carbon dioxide with a 15 wt-% ethanol modifier at 60°C at 19.4 MPa. The effect of varying the loading of walnut husk in the extractor upon impregnation mass was evaluated with the impregnation mass of the film increasing with walnut husk loading. It was determined by FTIR, as well as the reduction of the protein cytochrome c, that antioxidant compounds may be extracted from walnut husks and impregnated into low-density polyethylene film (LDPE) by this technique.