Enhanced in vitro and in vivo antioxidant activity and mobilization of free phenolic compounds of soybean flour fermented with different β-glucosidase-producing fungi

Aims:  To evaluate the soybean polyphenol glucosides bioconversion to aglycone forms by different β-glucosidases-producing filamentous fungi to enhance their antioxidant activity.
Methods and Results:  Soybean defatted flour was submitted to solid-state fermentation with Aspergillus niger , Aspergillus niveus and Aspergillus awamori . The fungi studied produced approximately the same β-glucosidase activity units amount when p- nitrophenyl-β- d -glucopyranoside was used as substrate for the assay. However, electrophoretic analysis, using 4-methylumbellipheryl-β- d -glucopyranoside as substrate, showed that β-glucosidase produced by A.   niveus was more active. Fermented methanolic extracts showed an increase in polyphenol and genistein contents and antioxidant activities. The highest genistein content was found in soybean fermented by A. niveus . Methanolic extracts of the soybean fermented by the different fungi showed a similar capacity of scavenging H₂O₂ generated in vivo by the tumour promoter 12- O- tetradecanoyl phorbol-13-acetate.
Conclusions:  A.   niveus synthesized a β-glucosidase with higher specificity to hydrolyse genistin β-glycosidic bond than those produced by A .  awamori and A. niger .
Significance and Impact of the Study:  The utilization of these β-glucosidases-producing fungi in soybean fermentation processes resulted in the obtaining of methanolic extracts with different antioxidant potentials that could be used either therapeutically or as an antioxidant in nonphysiological oxidative stress conditions, as the one induced in skin by UV radiation.     

Effects of biological invasions on forest carbon sequestration

There has been a rapidly developing literature on the effects of some of the major drivers of global change on carbon (C) sequestration, particularly carbon dioxide (CO₂) enrichment, land use change, nitrogen (N) deposition and climate change. However, remarkably little attention has been given to one major global change driver, namely biological invasions. This is despite growing evidence that invasive species can dramatically alter a range of aboveground and belowground ecosystem processes, including those that affect C sequestration. In this review, we assess the evidence for the impacts of biological invaders on forest C stocks and C sequestration by biological invaders. We first present case studies that highlight a range of invader impacts on C sequestration in forest ecosystems, and draw on examples that involve invasive primary producers, decomposers, herbivores, plant pathogens, mutualists and predators. We then develop a conceptual framework for assessing the effects of invasive species on C sequestration impacts more generally, by identifying the features of biological invaders and invaded ecosystems that are thought to most strongly regulate C in forests. Finally we assess the implications of managing invasive species on C sequestration. An important principle that emerges from this review is that the direct effects of invaders on forest C are often smaller and shorter‐term than their indirect effects caused by altered nutrient availability, primary productivity or species composition, all of which regulate long‐term C pools and fluxes. This review provides a conceptual basis for improving our general understanding of biological invaders on ecosystem C, but also points to a paucity of primary data that are needed to determine the quantitative effects of invaders on ecosystem processes that drive C sequestration.     

Synchrony of spatial populations: heterogeneous population dynamics and reddened environmental noise

Many species exhibit widespread spatial synchrony in population fluctuations. This pattern is of great ecological interest and can be a source of concern when a species is rare or endangered. Moran’s theorem suggests that if two (or more) populations sharing a common linear density-dependence in the renewal process are disturbed with correlated noise, they will become synchronized with correlation matching the noise correlation. In this report, correlation of nonidentical populations that are described by linear and stationary autoregressive processes is analyzed. We show that the expected spatial synchrony between two populations can be decomposed into two multiplicative components. One is the demographic component related to the values of the autoregressive coefficients and the noise color. The other is the spatial correlation of the environmental colored noise. The main results are consistent with the predictions of previous experiments and simulations, and the importance of this report is to provide theoretical support.     

Intracellular ethanol accumulation in yeast cells during aerobic fermentation: a Raman spectroscopic exploration

Aims: To investigate the intracellular ethanol accumulation in yeast cells by using laser tweezers Raman spectroscopy (LTRS). Methods and Results: Ethanol accumulation in individual yeast cells during aerobic fermentation triggered by excess glucose was studied using LTRS. Its amount was obtained by comparing intracellular and extracellular ethanol concentrations during initial process of ethanol production. We found that (i) yeasts start to produce ethanol within 3 min after triggering aerobic fermentation, (ii) average ratio of intracellular to extracellular ethanol is 1·54 ± 0·17 during the initial 3 h after addition of 10% (w/v) excess glucose and (iii) the accumulated intracellular ethanol is released when aerobic fermentation is stimulated with decreasing glucose concentration. Conclusions: Intracellular ethanol accumulation occurs in initial stage of a rapid aerobic fermentation and high glucose concentration may attribute to this accumulation process. Significance and Impact of the Study: This work demonstrates LTRS is a real‐time, reagent‐free, in situ technique and a powerful tool to study kinetic process of ethanol fermentation. This work also provides further information on the intracellular ethanol accumulation in yeast cells.     

Mitochondrial tRNAs as light strand replication origins: Similarity between anticodon loops and the loop of the light strand replication origin predicts initiation of DNA replication

Stem-loop hairpins formed by mitochondrial light strand replication origins (OL) and by heavy strand DNA coding for tRNAs that form OL-like structures initiate mitochondrial replication. The loops are recognized by one of the two active sites of the vertebrate mitochondrial gamma polymerase, which are homologuous to the active sites of class II amino-acyl tRNA synthetases. Therefore, the polymerase site recognizing the OL loop could recognize tRNA anticodon loops and sequence similarity between anticodon and OL loops should predict initiation of DNA replication at tRNAs. Strengths of genome-wide deamination gradients starting at tRNA genes estimate extents by which replication starts at that tRNA. Deaminations (A→G and C→T) occur proportionally to time spent single stranded by heavy strand DNA during mitochondrial light strand replication. Results show that deamination gradients starting at tRNAs are proportional to sequence similarity between OL and tRNA loops: most for anticodon-, least D-, intermediate for TψC-loops, paralleling tRNA synthetase recognition interactions with these tRNA loops. Structural and sequence similarities with regular OLs predict OL function, loop similarity is dominant in most tRNAs. Analyses of sequence similarity and structure independently substantiate that DNA sequences coding for mitochondrial tRNAs sometimes function as alternative OLs. Pathogenic mutations in anticodon loops increase similarity with the human OL loop, non-pathogenic polymorphisms do not. Similarity/homology alignment hypotheses are experimentally testable in this system.     

The Physiological,Biochemical and Molecular Roles of Brassinosteroids and Salicylic Acid in Plant Processes and Salt Tolerance

Plant hormones regulate plant growth and development by affecting an array of cellular, physiological, and developmental processes, including, but not limited to, cell division and elongation, stomatal regulation, photosynthesis, transpiration, ion uptake and transport, initiation of leaf, flower and fruit development, and senescence. Environmental factors such as salinity, drought, and extreme temperatures may cause a reduction in plant growth and productivity by altering the endogenous levels of plant hormones, sensitivity to plant hormones, and/or signaling pathways. Molecular and physiological studies have determined that plant hormones and abiotic stresses have interactive effects on a number of basic biochemical and physiological processes, leading to reduced plant growth and development. Various strategies have been considered or employed to maximize plant growth and productivity under environmental stresses such as salt-stress. A fundamental approach is to develop salt-tolerant plants through genetic means. Breeding for salt tolerance, however, is a long-term endeavor with its own complexities and inherent difficulties. The success of this approach depends, among others, on the availability of genetic sources of tolerance and reliable screening techniques, identification and successful transfer of genetic components of tolerance to desired genetic backgrounds, and development of elite breeding lines and cultivars with salt tolerance and other desirable agricultural characteristics. Such extensive processes have delayed development of successful salt-tolerant cultivars in most crop species. An alternative and technically simpler approach is to induce salt tolerance through exogenous application of certain plant growth–regulating compounds. This approach has gained significant interest during the past decade, when a wealth of new knowledge has become available on the beneficial roles of the six classes of plant hormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene, and brassinosteroids) as well as several other plant growth–regulating substances (jasmonates, salicylates, polyamines, triacontanol, ascorbic acid, and tocopherols) on plant stress tolerance. Among these, brassinosteroids (BRs) and salicylic acid (SA) have been studied most extensively. Both BRs and SA are ubiquitous in the plant kingdom, affecting plant growth and development in many different ways, and are known to improve plant stress tolerance. In this article, we review and discuss the current knowledge and possible applications of BRs and SA that could be used to mitigate the harmful effects of salt-stress in plants. We also discuss the roles of exogenous applications of BRs and SA in the regulation of various biochemical and physiological processes leading to improved salt tolerance in plants.     

Mechanism of killing of spores of Bacillus cereus and Bacillus megaterium by wet heat

Aims: To determine the mechanism of wet heat killing of spores of Bacillus cereus and Bacillus megaterium. Methods and Results: Bacillus cereus and B. megaterium spores wet heat‐killed 82–99% gave two bands on equilibrium density gradient centrifugation. The lighter band was absent from spores that were not heat‐treated and increased in intensity upon increased heating times. These spores lacked dipicolinic acid (DPA) were not viable, germinated minimally and had much denatured protein. The spores in the denser band had viabilities as low as 2% of starting spores but retained normal DPA levels and most germinated, albeit slowly. However, these largely dead spores outgrew poorly if at all and synthesized little or no ATP following germination. Conclusions: Wet heat treatment appears to kill spores of B. cereus and B. megaterium by denaturing one or more key proteins, as has been suggested for wet heat killing of Bacillus subtilis spores. Significance and Impact of the Study: This work provides further information on the mechanisms of killing of spores of Bacillus species by wet heat, the most common method for spore inactivation.     

An evaluation of the influence of environment and biogeography on community structure: the case of Holarctic mammals

Aim To evaluate the influence of environment and biogeographical region, as a proxy for historical influence, on the ecological structure of Holarctic communities from similar environments. It is assumed that similarities among communities from similar environments in different realms are the result of convergence, whereas their differences are interpreted as being due to different historical processes. Location Holarctic realm, North America and Eurasia above 25° N. Methods Checklists of mammalian species occurring in 96 Holarctic localities were collected from published sources. Species were assigned to one of 20 functional groups defined by diet, body size and three‐dimensional use of space. The matrix composed of the frequencies of functional groups in the 96 localities is used as input data in a correspondence analysis (CA). The localities are classified into nine groups according to Bailey's ecoregions (used as a surrogate of regional climate), and the positions of the communities in the dimensions of the CA are compared in relation to ecoregion and realm. Partial regression was used to test for the relative influence of ecoregion and realm over each dimension and to evaluate the effect of biogeographical realm on the variation in the factor scores of the communities of the same ecoregion. Results In some cases, mammalian communities from areas with similar regional climates exhibit convergence in community structure, irrespective of the biogeographical realm where they are located. However, all of them are clearly subdivided into Nearctic and Palearctic subsets. Differences in the composition of the regional pools only partially explain differences in local communities between realms. Main conclusions Holarctic mammalian communities from regions with widely different climates differ in ecological structure irrespective of their biogeographical location. On the other hand, the structures of Nearctic and Palearctic communities from regions of similar climate radically differ in some features. Thus, although present climatic conditions influence community structure, contingent historic processes associated with each region also play a major role in determining community structure.