Hypocrea jecorina (anamorph Trichoderma reesei) is a fungus of noteworthy industrial importance, mainly because of its employment in both fermentative production of native extracellular enzymes and heterologous protein production. Hydrolases secreted by this fungus have achieved broad areas of applications, e.g., in pulp and paper (4, 35, 50), food and feed (9, 27, 49), and textile (23,26,36) industries. The set of hydrolytic enzymes produced by H. jecorina comprises two main cellobiohydrolases, CBHI and CBHII (EC 3.2.1.91) (43); endo-␤-1,4-glucanases EGI to EGV (EC 3.2

SummaryThe bacterioplankton diversity in large rivers has thus far been under-sampled despite the importance of streams and rivers as components of continental landscapes. Here, we present a comprehensive dataset detailing the bacterioplankton diversity along the midstream of the Danube River and its tributaries. Using 16S rRNA-gene amplicon sequencing, our analysis revealed that bacterial richness and evenness gradually declined downriver in both the free-living and particle-associated bacterial communities. These shifts were also supported by beta diversity analysis, where the effects of tributaries were negligible in regards to the overall variation. In addition, the river was largely dominated by bacteria that are commonly observed in freshwaters. Dominated by the acI lineage, the freshwater SAR11 (LD12) and the Polynucleobacter group, typical freshwater taxa increased in proportion downriver and were accompanied by a decrease in soil and groundwater-affiliated bacteria. Based on views of the metacommunity and River Continuum Concept, we interpret the observed taxonomic patterns and accompanying changes in alpha and beta diversity with the intention of laying the foundation for a unified concept for river bacterioplankton diversity.

In Hypocrea jecorina, Xyr1 (xylanase regulator 1) is the main transcription activator of hydrolase-encoding genes, such as xyn1, xyn2, bxl1, cbh1, cbh2, egl1, and bgl1. Even though Xyr1 mediates the induction signal for all these genes derived from various inducing carbon sources and compounds, xyr1 transcription itself is not inducible by any of these substances. However, cultivation on glucose as the carbon source provokes carbon catabolite repression of xyr1 transcription mediated by Cre1. In addition, xyr1 transcription is repressed by the specific transcription factor Ace1. Moreover, Xyr1 is permanently available in the cell, and no de novo synthesis of this factor is needed for a first induction of xyn1 transcription. The constitutive expression of xyr1 leads to a significant elevation/deregulation of the xyn1, xyn2, and bxl1 transcription compared to what is seen for the parental strain. Overall, the corresponding xylanolytic enzyme activities are clearly elevated in a constitutively xyr1-expressing strain, emphasizing this factor as an auspicious target for genetically engineered strain improvement.

GALl, GAL4 and GALIO transcription [5,6]. The sequence 5'-SYGGRG-Y been proposed as a consensus for CreA-binding [7]. Unlike MIG1, however, CreA contains an additional domain downstream of the zinc-finger, which has been reported to bear high similarity to S. cerevisiae RGR1 [8,9], and whose function is unknown. Since its cloning and sequencing, molecular evidence has been presented for an involvement of CreA in the catabolite repression of transcription of genes involved in proline utilization [7], ethanol metabolism [10,11] and polysaccharide hydrolysis [12] in A. nidulans.Nothing is known as yet on the mechanism of carbon catabolite repression in other fungi. The filamentous fungus Trichoderma reesei is an industrially important producer of several extracellular enzymes, including a highly active cellulase [13] and hemicellulase enzyme system [14]. The formation of some of these enzymes (e.g. cellobiohydrolase I; endo-fl-l,4-xylanase I) is repressed by glucose [15,16]. It has been reported that the 5'-upstream nt-sequence of the T. reesei gene encoding cellobiohydrolase I (cbhl) shows consensus sequences for binding of a potential CreA-homologue [17]. Deletion of these sequences resulted in glucose derepressed transcription of cbhl [17]. It is therefore possible that carbon catabolite repression in T. reesei occurs by a mechanism similar to that existant in Aspergillus. However, the presence of a DNA-binding protein in T. reesei similar to CreA has not yet been published. As a first step towards understanding the mechanisms and cloning of the genes involved in carbon catabolite repression in T. reesei, we demonstrate here the presence of a creA homologue in T. reesei Crel --and provide evidence that the native gene product is a DNA-binding protein, thereby showing that the mechanisms of carbon catabolite repression have been basically conserved in the ascomycetous classes of Pyrenomycetes and Plectomycetes.Carbon catabolite repression in microorganisms is a means I~) control the synthesis of a range of enzymes required for the t~tilization of less favoured carbon sources when more readily t~tilized carbon sources are present in the medium. Several genes participating in this process have been identified in Sactzaromyces cerevisiae [1,2]. In the multicellular fungi, the creA gene cloned from Aspergillus nidulans [3] and A. niger [4] is the ~nly hitherto regulatory gene known to mediate carbon cat~l bolite repression. It encodes a DNA-binding protein containi Mlg a two-zinc-finger domain of the C2H2 class, which mediates ,~4% similarity to MIG1 from S. cerevisiae, which is also *Corresponding author. Fax: (43)(1) 581-6266. l-mail: jos@eichow.tuwien.ac.at Experimental Strain, cloning vector and plasmidTrichoderma reesei strain QM 9414 (ATCC 26921 ) was used throughout this study and maintained on malt agar. Bluescript II/SK+ (Stratagene, La Jolla, CA) and E. coli LC 137 (Pharmacia-LKB, Uppsala, Sweden) were used as cloning and plasmid vectors, respectively. Cloning of the T. reesei crel geneFungal genomic DNA...

The filamentous fungi Aspergillus niger and

Two major xylanases (XYN I and XYN II) of the filamentous fungus

A quantitative TaqMan minor-groove binder real-time PCR assay was developed for the sensitive detection of a ruminant-specific genetic marker in fecal members of the phylum Bacteroidetes. The qualitative and quantitative detection limits determined were 6 and 20 marker copies per PCR, respectively. Tested ruminant feces contained an average of 4.1 ؋ 10 9 marker equivalents per g, allowing the detection of 1.7 ng of feces per filter in fecal suspensions. The marker was detected in water samples from a karstic catchment area at levels matching a gradient from negligible to considerable ruminant fecal influence (from not detectable to 10 5

The filamentous fungus Trichoderma reesei forms two specific, xylan-inducible xylanases encoded by xyn1 and xyn2 to degrade the beta-1,4-D-xylan backbone of hemicelluloses. This enzyme system is formed in the presence of xylan, but not glucose. The molecular basis of the absence of xylanase I formation on glucose was the purpose of this study. Northern blotting of the xyn1 transcript as well as the use of the Escherichia coli hygromycin B phosphotransferase-encoding gene (hph) as a reporter consistently showed that the basal expression of xyn1 was affected by glucose, whereas its induction by xylan remained uninfluenced. The repression of basal xyn1 transcription is mediated by the carbon catabolite repressor protein Cre1, which in vivo binds to two of four consensus sites (5'-SYG-GRG-3') in the xyn1 promoter, which occurred in the form of an inverted repeat. T. reesei strains, bearing a xyn1::hph reporter construct, in which four nucleotides from the middle of the inverted repeat had been removed, expressed hph on glucose at a level comparable to that observed during growth on a carbon catabolite derepressing carbon source. Northern analysis of xyn1 expression in a T. reesei mutant strain (RUT C-30), which contains a truncated, non-functional cre1 gene, also confirmed basal transcription of xyn1. In this strain, xyn1 transcription was still inducible by xylose or xylan to an even higher degree than in the wild-type strain, suggesting that induction overcomes glucose repression at the level of xyn1 expression. Based on these data, we postulate that basal transcription of xyn1 is repressed by glucose and mediated by an inverted repeat of the consensus motif for Cre1-mediated carbon catabolite repression.