Extracellular enzymes of some additional fungi associated with mushroom culture

Twenty-four fungus isolates from the compost utilized in commercially growing Agaricus brunnescens were tested for their ability to produce extracellular enzymes involved in the degradation of cellulose, lignin and xylan, the major components of the straw of the compost. All 24 isolates were able to degrade carboxymethyl cellulose. Most were classified as weak or moderate producers of exo--glucanase. Twenty of the 24 were also able to hydrolyze filter paper, a crystalline cellulose. Nineteen of the 24 were able to hydrolyze xylan, a hemicellulose. The production of extracellular polyphenol oxidases was detected utilizing two tests; the blueing of alcoholic gum guaiacol, which indicates tyrosinase production, and the browning of malt extract-gallic acid agar, which indicates laccase production. Twenty produced tyrosinase, but only eight produced laccase. Agaricus brunnescens was also included in all of the tests. It produced exo--glucanase, hemicellulase, tyrosinase and lactase.     

Species diversity reduces invasion success in pathogen‐regulated communities

The loss of natural enemies is thought to explain why certain invasive species are so spectacularly successful in their introduced range. However, if losing natural enemies leads to unregulated population growth, this implies that native species are themselves normally subject to natural enemy regulation. One possible widespread mechanism of natural enemy regulation is negative soil feedbacks, in which resident species growing on home soils are disadvantaged because of a build‐up of species‐specific soil pathogens. Here we construct simple models in which pathogens cause resident species to suffer reduced competitive ability on home soils and consider the consequences of such pathogen regulation for potential invading species. We show that the probability of successful invasion and its timescale depend strongly on the competitive ability of the invader on resident soils, but are unaffected by whether or not the invader also suffers reduced competitive ability on home soils (i.e. pathogen regulation). This is because, at the start of an invasion, the invader is rare and hence mostly encounters resident soils. However, the lack of pathogen regulation does allow the invader to achieve an unusually high population density. We also show that increasing resident species diversity in a pathogen‐regulated community increases invasion resistance by reducing the frequency of home‐site encounters. Diverse communities are more resistant to invasion than monocultures of the component species: they preclude a greater range of potential invaders, slow the timescale of invasion and reduce invader population size. Thus, widespread pathogen regulation of resident species is a potential explanation for the empirical observation that diverse communities are more invasion resistant.     

Population structure and evolution of the Bacillus cereus group

Representative strains of the Bacillus cereus group of bacteria, including Bacillus anthracis (11 isolates), B. cereus (38 isolates), Bacillus mycoides (1 isolate), Bacillus thuringiensis (53 isolates from 17 serovars), and Bacillus weihenstephanensis (2 isolates) were assigned to 59 sequence types (STs) derived from the nucleotide sequences of seven alleles, glpF, gmk, ilvD, pta, pur, pycA, and tpi. Comparisons of the maximum likelihood (ML) tree of the concatenated sequences with individual gene trees showed more congruence than expected by chance, indicating a generally clonal structure to the population. The STs followed two major lines of descent. Clade 1 comprised B. anthracis strains, numerous B. cereus strains, and rare B. thuringiensis strains, while clade 2 included the majority of the B. thuringiensis strains together with some B. cereus strains. Other species were allocated to a third, heterogeneous clade. The ML trees and split decomposition analysis were used to assign STs to eight lineages within clades 1 and 2. These lineages were defined by bootstrap analysis and by a preponderance of fixed differences over shared polymorphisms among the STs. Lineages were named with reference to existing designations: Anthracis, Cereus I, Cereus II, Cereus III, Kurstaki, Sotto, Thuringiensis, and Tolworthi. Strains from some B. thuringiensis serovars were wholly or largely assigned to a single ST, for example, serovar aizawai isolates were assigned to ST-15, serovar kenyae isolates were assigned to ST-13, and serovar tolworthi isolates were assigned to ST-23, while other serovars, such as serovar canadensis, were genetically heterogeneous. We suggest a revision of the nomenclature in which the lineage and clone are recognized through name and ST designations in accordance with the clonal structure of the population.     

A comparison of the strength of biodiversity effects across multiple functions

In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.     

Habitat characteristics of breeding Eurasian Whimbrel Numenius phaeopus on Mainland Shetland,Scotland, UK

Capsule: Habitats used by Whimbrel Numenius phaeopus chicks for feeding are significantly different to those used by adults for feeding and nesting.

Aim: To identify habitats used by breeding Whimbrel on Mainland Shetland.

Methods: Fourteen study sites were used to identify three main components of Whimbrel breeding habitats: (i) adult territorial and foraging habitats; (ii) nest site habitats; (iii) chick feeding habitats. The relationship between these components was investigated using principal components analysis.

Results: Habitats used by adults comprised blanket bog dominated by ling heather, cross-leaved heath, common cottongrass, hare’s-tail cottongrass, deergrass and purple moor-grass. There was a thick layer of bryophytes but few forbs. Habitat used for nesting was similar to the general habitat used by adults. The habitats in which Whimbrel chicks foraged were significantly different in structure from the habitats used by adults. The chick feeding areas were characterized by small, wet and often linear features.

Conclusion: Habitat requirements by Whimbrel chicks for foraging differed from those of adult Whimbrel for nesting. Habitat structure is important for chicks and the presence of small, wet linear features may be a limiting component on otherwise apparently suitable adult Whimbrel habitats.     

p53 mediates repression of the BRCA2 promoter and down-regulation of BRCA2 mRNA and protein levels in response to DNA damage

Adriamycin and other DNA-damaging agents have been shown to reduce BRCA2 mRNA levels in breast cancer cell lines, but the mechanism by which this occurs is unknown. In this study, we show that adriamycin and mitomycin C, but not other DNA-damaging agents, repress BRCA2 promoter activity in a dose- and time-dependent manner. We demonstrate that the effect is dependent on wild type p53 and that adriamycin and p53 mediate repression of the BRCA2 promoter by inhibiting binding of an upstream stimulatory factor protein complex to the promoter. In addition, we present evidence indicating that adriamycin and other DNA-damaging agents reduce BRCA2 mRNA and protein levels by altering both BRCA2 mRNA stability and protein stability. Thus, BRCA2 levels in the cell are regulated by three independent mechanisms in a p53-dependent manner.     

Cellular remodeling in heart failure disrupts K(ATP) channel-dependent stress tolerance

ATP-sensitive potassium (K(ATP)) channels are required for maintenance of homeostasis during the metabolically demanding adaptive response to stress. However, in disease, the effect of cellular remodeling on K(ATP) channel behavior and associated tolerance to metabolic insult is unknown. Here, transgenic expression of tumor necrosis factor alpha induced heart failure with typical cardiac structural and energetic alterations. In this paradigm of disease remodeling, K(ATP) channels responded aberrantly to metabolic signals despite intact intrinsic channel properties, implicating defects proximal to the channel. Indeed, cardiomyocytes from failing hearts exhibited mitochondrial and creatine kinase deficits, and thus a reduced potential for metabolic signal generation and transmission. Consequently, K(ATP) channels failed to properly translate cellular distress under metabolic challenge into a protective membrane response. Failing hearts were excessively vulnerable to metabolic insult, demonstrating cardiomyocyte calcium loading and myofibrillar contraction banding, with tolerance improved by K(ATP) channel openers. Thus, disease-induced K(ATP) channel metabolic dysregulation is a contributor to the pathobiology of heart failure, illustrating a mechanism for acquired channelopathy.     

Improved tests for heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence

The neutral theory of molecular evolution predicts that the ratio of polymorphisms to fixed differences should be fairly uniform across a region of DNA sequence. Significant heterogeneity in this ratio can indicate the effects of balancing selection, selective sweeps, mildly deleterious mutations, or background selection. Comparing an observed heterogeneity statistic with simulations of the heterogeneity resulting from random phylogenetic and sampling variation provides a test of the statistical significance of the observed pattern. When simulated data sets containing heterogeneity in the polymorphism-to-divergence ratio are examined, different statistics are most powerful for detecting different patterns of heterogeneity. The number of runs is most powerful for detecting patterns containing several peaks of polymorphism; the Kolmogorov-Smirnov statistic is most powerful for detecting patterns in which one end of the gene has high polymorphism and the other end has low polymorphism; and a newly developed statistic, the mean sliding G statistic, is most powerful for detecting patterns containing one or two peaks of polymorphism with reduced polymorphism on either side. Nine out of 27 genes from the Drosophila melanogaster subgroup exhibit heterogeneity that is significant under at least one of these three tests, with five of the nine remaining significant after a correction for multiple comparisons, suggesting that detectable evidence for the effects of some kind of selection is fairly common.