Flocculation of Saccharomyces-cerevisiae - Inhibition By Sugars

Flocculation is governed by the competition between electrostatic repulsion (nonspecific interactions) and polysaccharide-protein bonds (specific interactions). In our study, the inhibition of flocculation by sugars for 12 strains of Saccharomyces cerevisiae leads us to extend the classification described in the literature and to define three groups of yeasts: flocculation mannose sensitive (MS), flocculation glucose-mannose sensitive (GMS), and flocculation mannose insensitive (MI). Only the first two groups showed specific interactions between proteins and mannans. In the MI group, the sugars tested did not inhibit flocculation. To characterize the particularities of the stereochemistry of the cell-wall proteic receptors of strains belonging to the MS and GMS groups, 31 sugars were used as inhibitor probes on two representative strains. The results show that the lectin specificity of strains belonging to the GMS group is less restricted regarding C-1 and C-2 hydroxyl groups than the lectin from strains belonging to the MS group, which interacts with all of the hydroxyl groups of mannopyranose. The two groups also differ with respect to inhibition by sugars: strains belonging to the MS group are partially inhibited whereas strains of the GMS group are completely inhibited. We observed that the presence of ethanol increases sugar fixation by strains from the MS group, but not from the GMS group. Moreover, both receptors interact with disaccharides, provided the two monomers are linked by an alpha(1 --> 4), alpha(1 --> 3), or alpha(1 --> 2) bond

Fluorescence study of lectinlike receptors involved in the flocculation of the yeast Saccharomyces cerevisiae.

Flocculation of some yeasts involves lectinlike receptors with two different patterns of inhibition by sugars: mannose sensitive (MS) and glucose-mannose sensitive (GMS). The visualization and quantification of these receptors were performed using neoglycoproteins fluorescent probes. Fluorescence microscopy showed a homogeneous distribution of surface receptors for the strain belonging to the MS group and a polar distribution for cells belonging to the GMS group. Affinity constants, estimated by fluorimetry, were shown to have different values (MS, 2.6 +/- 0.7 x 10(5) M-1; GMS, 2 +/- 1 x 10(6) M-1), but the number of sites was estimated to be smaller for strain NCYC 1195 which belongs to the GMS group than for strain NCYC 869 from the MS group (MS, 2.4 +/- 0.2 x 10(7) sites/cell; GMS, 3.9 +/- 0.8 x 10(6) sites/cell)

Understanding farmers’ perceptions and the effects of shea (Vitellaria paradoxa) tree distribution in agroforestry parklands of Upper West Region, Ghana

Agroforestry parklands, characterized by scattered trees growing within cultivated crop fields, are the most widespread agricultural system in semi-arid West Africa. Agroforestry trees offer many ecological and socioeconomic benefits, such as added income, food, and medicine. They are currently under threat in this region due to recent changes in agricultural and land use practices. For example, a reduction in traditional fallow rotation periods has led to decreased regeneration of a common agroforestry tree, shea (Vitellaria paradoxa), which has been an important economic resource for women. The aims of this study were to determine beneficial spatial distributions of shea to maintain high yields of staple crops and to better understand male and female farmer perceptions of shea maintenance. We compared maize (Zea mays) vegetative growth, grain yield, soil moisture, and light availability associated with individual shea trees and clumps of trees on five farms in Ghanaian agroforestry parklands. We also interviewed local farmers to better understand their management perspectives. Maize vegetative growth increased with light availability, but was not limited by soil moisture. Conversely and contrary to farmer perceptions, grain yield was not influenced by light availability, but increased with increasing soil moisture. Also contrary to common beliefs of local farmers, grain yield was greater under clumps of shea compared to scattered distributions of individual trees. We therefore recommend the maintenance of clumped distributions of shea, as they provide beneficial microclimates for staple crops, and could assist in improving the productivity of shea products that are considered the domain of women farmers

An educational framework to promote self-authorship in engineering undergraduates

In this paper, we share an educational framework built on the theories of adult development self-authorship and self-determination, as well as our curriculum which is designed to build capacity for self-authorship in our students. We will outline the innovations that this has introduced to our program including creating an honors program that does not use GPA or standardized test scores for admission or retention. We will share our rubric for assessment of self-authorship using reflection assignments and offer case studies of engineering students who reveal increasing levels of self-authorship capacity and preparation as flexible professionals, ready to enter the rapidly changing world and engineering work force

American world visions of vulnerability: The sacred, the secular, and roots of evangelical American aid

© 2019 by Emerald Publishing Limited All rights of reproduction in any form reserved. In this article, I analyze constructions of and responses to vulnerability in the US government and a now-prominent evangelical aid organization, World Vision, during the 1950s and 1960s in Korea and Vietnam. World Vision was founded as the “development discourse,” Cold War rhetoric, and the neo-evangelical movement were all rising to prominence in the United States. World Vision’s early understandings of vulnerability resonated with Cold War and modernization theory rhetoric in certain ways; however, its approaches to remake vulnerable Asians were often distinct. World Vision evangelical Christians looked to private voluntary organizations and individual conversions in a free society to remake individuals and nations, notions not so different from neoliberal development approaches today. US foreign aid approaches were rooted in nation-building for centralized, planned government institutions and economies to modernize “traditional” people. This article examines the complex relationships between missionaries, evangelists, US foreign aid experts and the military in American constructions of vulnerable traditional Asians and interventions to modernize and Christianize them. In examining roots of faith-based development models through the case of World Vision and notions of vulnerability, historical threads and lineages emerge for understanding the relationship of religion and the state in modernizing projects, and faith-based and neoliberal development models