Mixed colonies of Aspergillus niger and Aspergillus oryzae cooperatively degrading wheat bran.

In both natural and man-made environments, microorganisms live in mixed populations, while in laboratory conditions monocultures are mainly used. Microbial interactions are often described as antagonistic, but can also be neutral or cooperative, and are generally associated with a metabolic change of each partner and cause a change in the pattern of produced bioactive molecules. A. niger and A. oryzae are two filamentous fungi widely used in industry to produce various enzymes (e.g. pectinases, amylases) and metabolites (e.g. citric acid). The co-cultivation of these two fungi in wheat bran showed an equal distribution of the two strains forming mixed colonies with a broad range of carbohydrate active enzymes produced. This stable mixed microbial system seems suitable for subsequent commercial processes such as enzyme production. XlnR knock-out strains for both aspergilli were used to study the influence of plant cell wall degrading enzyme production on the fitness of the mixed culture. Microscopic observation correlated with quantitative PCR and proteomic data suggest that the XlnR Knock-out strain benefit from the release of sugars by the wild type strain to support its growth.

Quercetin decreases high-fat diet induced body weight gain and accumulation of hepatic and circulating lipids in mice.

Dietary flavonoids may protect against cardiovascular diseases (CVD). Increased circulating lipid levels and hepatic lipid accumulation are known risk factors for CVD. The aim of this study was to investigate the effects and underlying molecular mechanisms of the flavonoid quercetin on hepatic lipid metabolism in mice with high-fat diet induced body weight gain and hepatic lipid accumulation. Adult male mice received a 40 energy% high-fat diet without or with supplementation of 0.33 % (w/w) quercetin for 12 weeks. Body weight gain was 29 % lower in quercetin fed mice (p < 0.01), while the energy intake was not significantly different. Quercetin supplementation lowered hepatic lipid accumulation to 29 % of the amount present in the control mice (p < 0.01). (1)H nuclear magnetic resonance serum lipid profiling revealed that the supplementation significantly lowered serum lipid levels. Global gene expression profiling of liver showed that cytochrome P450 2b (Cyp2b) genes, key target genes of the transcription factor constitutive androstane receptor (Car; official symbol Nr1i3), were downregulated. Quercetin decreased high-fat diet induced body weight gain, hepatic lipid accumulation and serum lipid levels. This was accompanied by regulation of cytochrome P450 2b genes in liver, which are possibly under transcriptional control of CAR. The quercetin effects are likely dependent on the fat content of the diet.

The molecular basis of co-evolution between Cladosporium fulvum and tomato.

Cladosporiumfulvum is a semi-biotrophic pathogen, which causes leaf mold of tomato (Lycopersicon spp.). In our laboratory this pathosystem serves as a model to study gene-for-gene interactions between plants and pathogenic fungi (Joosten & De Wit 1999). Many avirulence (Avr) genes and matching resistance (CQ) genes have been cloned and we are now beginning to understand how their products can induce an array of plant defense responses, including the classic hypersensitive response (HR). Here, we will discuss the latest results of our molecular studies on this interaction. These include the isolation of: (i) two new Avr genes, Avr2 and Avr4E, (ii) the determination of the specificity determinants within the Cf-4 and Cf-9 genes by artificial domain swaps and introduction of point mutations, (iii) the analysis of polymorphism occurring in AVR9-responsive Cf genes occurring in natural populations of L. pimpinellifolium, and finally (iv) the description of an efficient method to identify early HR-related genes.