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This study compared the responses of Avicennia marina and Trichilia dregeana seeds, both of which are recalcitrant, to partial dehydration and storage. Seeds of A. marina exhibited a faster rate of water and viability loss (± 50% viability loss in 4 days) during partial dehydration, compared with T. dregeana (± 50% viability loss in 14 days). In A. marina embryonic axes, reactive oxygen species (ROS) production peaked on 4 days of dehydration and was accompanied by an increase in the GSH:GSSG ratio; it appears that the glutathione system alone could not overcome dehydration-induced oxidative stress in this species. In A. marina, ROS and axis water content levels increased during hydrated storage and were accompanied by a decline in the GSH:GSSG ratio and rapid viability loss. In T. dregeana embryonic axes, ROS production (particularly hydrogen peroxide) initially increased and thereafter decreased during both partial dehydration and hydrated storage. Unlike in A. marina embryonic axes, this reduced ROS production was accompanied by a decline in the GSH:GSSG ratio. While T. dregeana seeds may have incurred some oxidative stress during storage, a delay in and/or suppression of the ROS-based trigger for germination may account for their significantly longer storage longevity compared with A. marina. Mechanisms of desiccation-induced seed viability loss may differ across recalcitrant-seeded species based on the rate and extent to which they lose water during partial drying and storage. While recalcitrant seed desiccation sensitivity and, by implication, storage longevity are modulated by redox metabolism, the specific ROS and antioxidants that contribute to this control may differ across species. [ABSTRACT FROM AUTHOR]

The [3+2] cycloaddition reaction between nitroolefins and alkyl/aryl azides was studied using functionalized silver nanoparticles (FnAgNPs) of average diameter 23 ± 1 nm as catalyst produced by the plant extract Protorhus longifolia. We found FnAgNPs to catalyze the reactions efficiently yielding a series of 1,5-disubstituted-1,2,3-triazolines under mild reaction conditions with no side products. The catalytic activity of FnAgNPs was compared with naked AgNPs and FnAgNPs found to be very effective. Except solvents, the whole experiments do not require any chemical/reagent which makes the process green. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), a powerful biotyping tool for the identification of bacteria and clinical yeast isolates, was investigated as a method to rapidly identify industrial S. cerevisiae strains. In this study, an optimized sample preparation protocol was devised for the biotyping of S. cerevisiae strains. The results demonstrate that ethanol/formic acid protein extraction, of a cell density of 1 × 10 cells co-crystallized with α-cyano-4-hydroxycinnmaic acid, is required to yield mass spectral profiles that are diagnostic of each strain type. Forty-four S. cerevisiae strains commonly employed in South African fermentation-based industries were biotyped in an attempt to create a yeast reference database within a local context. The data revealed that MALDI-TOF MS can be used for the rapid and accurate identification of laboratory and industrial S. cerevisiae strains. [ABSTRACT FROM AUTHOR]

The antimicrobial activity of five novel SQ109 derivatives including SQ109 against bacteria, yeast and filamentous fungi is reported herein. Using broth microdilution techniques, compounds 2 and 3 were found to be active against most tested fungi and bacteria, with minimum inhibitory concentrations (MICs) ranging from 0.98 to 31 μg ml, except for Klebsiella pneumonia where the MIC was 250 μg ml. SQ109 and derivative 4 did not show any significant activity against most of the organisms used. However, their reduced derivatives 1 and 5 showed promising activity with MICs between 0.49 and 62.5 μg ml against most of the microorganisms used. [ABSTRACT FROM AUTHOR]

The NMR elucidation of five novel SQ109 analogues including SQ109 is reported herein. These derivatives were synthesized as potential anti-tuberculosis candidates. One-dimensional NMR (H and C) techniques show a series of overlapping signals from the methine and methylene groups of these compounds, thereby making it extremely difficult to assign all NMR signals. Two-dimensional (2D) NMR techniques were instrumental in overcoming these challenges. This paper appears to be a rare report on the complete structure elucidation of mono-substituted adamantane moieties. [ABSTRACT FROM AUTHOR]

Adhesion properties of microorganisms are crucial for many essential biological processes such as sexual reproduction, tissue or substrate invasion, biofilm formation and others. Most, if not all microbial adhesion phenotypes are controlled by factors such as nutrient availability or the presence of pheromones. One particular form of controlled cellular adhesion that occurs in liquid environments is a process of asexual aggregation of cells which is also referred to as flocculation. This process has been the subject of significant scientific and biotechnological interest because of its relevance for many industrial fermentation processes. Specifically adjusted flocculation properties of industrial microorganisms could indeed lead to significant improvements in the processing of biotechnological fermentation products such as foods, biofuels and industrially produced peptides. This review briefly summarises our current scientific knowledge on the regulation of flocculation-related phenotypes, their importance for different biotechnological industries, and possible future applications for microorganisms with improved flocculation properties. [ABSTRACT FROM AUTHOR]

Most commercial yeast strains are nonflocculent. However, controlled flocculation phenotypes could provide significant benefits to many fermentation-based industries. In nonflocculent laboratory strains, it has been demonstrated that it is possible to adjust flocculation and adhesion phenotypes to desired specifications by altering expression of the otherwise silent but dominant flocculation ( FLO) genes. However, FLO genes are characterized by high allele heterogeneity and are subjected to epigenetic regulation. Extrapolation of data obtained in laboratory strains to industrial strains may therefore not always be applicable. Here, we assess the adhesion phenotypes that are associated with the expression of a chromosomal copy of the FLO1, FLO5, or FLO11 open reading frame in two nonflocculent commercial wine yeast strains, BM45 and VIN13. The chromosomal promoters of these genes were replaced with stationary phase-inducible promoters of the HSP30 and ADH2 genes. Under standard laboratory and wine making conditions, the strategy resulted in expected and stable expression patterns of these genes in both strains. However, the specific impact of the expression of individual FLO genes showed significant differences between the two wine strains and with corresponding phenotypes in laboratory strains. The data suggest that optimization of the flocculation pattern of individual commercial strains will have to be based on a strain-by-strain approach. [ABSTRACT FROM AUTHOR]