Generation, Transfer, and Loss of Alternative Oxidase Paralogues in the Aspergillaceae Family

Alternative oxidase (Aox) is a terminal oxidase operating in branched electron transport. The activity correlates positively with overflow metabolisms in certain Aspergilli, converting intracellular glucose by the shortest possible path into organic acids, like citrate or itaconate. Aox is nearly ubiquitous in fungi, but aox gene multiplicity is rare. Nevertheless, within the family of the Aspergillaceae and among its various species of industrial relevance-Aspergillus niger, A. oryzae, A. terreus, Penicillium rubens-paralogous aox genes coexist. Paralogous genes generally arise from duplication and are inherited vertically. Here, we provide evidence of four independent duplication events along the lineage that resulted in aox paralogues (aoxB) in contemporary Aspergillus and Penicillium taxa. In some species, three aox genes are co-expressed. The origin of the A. niger paralogue is different than that of the A. terreus paralogue, but all paralogous clades ultimately arise from ubiquitous aoxA parent genes. We found different patterns of uncorrelated gene losses reflected in the Aspergillus pedigree, albeit the original aoxA orthologues persist everywhere and are never replaced. The loss of acquired paralogues co-determines the contemporary aox gene content of individual species. In Aspergillus calidoustus, the two more ancient paralogues have, in effect, been replaced by two aoxB genes of distinct origins.

Are Basic Substances a Key to Sustainable Pest and Disease Management in Agriculture? An Open Field Perspective

Pathogens and pests constantly challenge food security and safety worldwide. The use of plant protection products to manage them raises concerns related to human health, the environment, and economic costs. Basic substances are active, non-toxic compounds that are not predominantly used as plant protection products but hold potential in crop protection. Basic substances' attention is rising due to their safety and cost-effectiveness. However, data on their protection levels in crop protection strategies are lacking. In this review, we critically analyzed the literature concerning the field application of known and potential basic substances for managing diseases and pests, investigating their efficacy and potential integration into plant protection programs. Case studies related to grapevine, potato, and fruit protection from pre- and post-harvest diseases and pests were considered. In specific cases, basic substances and chitosan in particular, could complement or even substitute plant protection products, either chemicals or biologicals, but their efficacy varied greatly according to various factors, including the origin of the substance, the crop, the pathogen or pest, and the timing and method of application. Therefore, a careful evaluation of the field application is needed to promote the successful use of basic substances in sustainable pest management strategies in specific contexts.

Hybrid Vitis Cultivars with American or Asian Ancestries Show Higher Tolerance towards Grapevine Trunk Diseases

Grape production worldwide is increasingly threatened by grapevine trunk diseases (GTDs). No grapevine cultivar is known to be entirely resistant to GTDs, but susceptibility varies greatly. To quantify these differences, four Hungarian grape germplasm collections containing 305 different cultivars were surveyed to determine the ratios of GTDs based on symptom expression and the proportion of plant loss within all GTD symptoms. The cultivars of monophyletic Vitis vinifera L. origin were amongst the most sensitive ones, and their sensitivity was significantly (p < 0.01) higher than that of the interspecific (hybrid) cultivars assessed, which are defined by the presence of Vitis species other than V. vinifera (e.g., V. labrusca L., V. rupestris Scheele, and V. amurensis Rupr.) in their pedigree. We conclude that the ancestral diversity of grapes confers a higher degree of resilience against GTDs.

Mutations in the Second Alternative Oxidase Gene: A New Approach to Group Aspergillus niger Strains

Alternative oxidase is a terminal oxidase in the branched mitochondrial electron transport chain of most fungi including Aspergillus niger (subgenus Circumdati, section Nigri). A second, paralogous aox gene (aoxB) is extant in some A. niger isolates but also present in two divergent species of the subgenus Nidulantes-A. calidoustus and A. implicatus-as well as in Penicillium swiecickii. Black aspergilli are cosmopolitan opportunistic fungi that can cause diverse mycoses and acute aspergillosis in immunocompromised individuals. Amongst the approximately 75 genome-sequenced A. niger strains, aoxB features considerable sequence variation. Five mutations were identified that rationally affect transcription or function or terminally modify the gene product. One mutant allele that occurs in CBS 513.88 and A. niger neotype strain CBS 554.65 involves a chromosomal deletion that removes exon 1 and intron 1 from aoxB. Another aoxB allele results from retrotransposon integration. Three other alleles result from point mutations: a missense mutation of the start codon, a frameshift, and a nonsense mutation. A. niger strain ATCC 1015 has a full-length aoxB gene. The A. niger sensu stricto complex can thus be subdivided into six taxa according to extant aoxB allele, which may facilitate rapid and accurate identification of individual species.

Bioreactor as the root cause of the “manganese effect” during Aspergillus niger citric acid fermentations

High-yield citric acid production by the filamentous Ascomycete fungus Aspergillus niger requires a combination of extreme nutritional conditions, of which maintaining a low manganese (II) ion concentration (<5 μg L⁻¹) is a key feature. Technical-scale production of citric acid predominantly uses stainless-steel tank fermenters, but glass bioreactors used for strain improvement and manufacturing process development also contain stainless steel components, in which manganese is an essential alloying element. We show here that during citric acid fermentations manganese (II) ions were leaching from the bioreactor into the growth media, resulting in altered fungal physiology and morphology, and significant reduction of citric acid yields. The leaching of manganese (II) ions was dependent on the fermentation time, the acidity of the culture broth and the sterilization protocol applied. Manganese (II) ion leaching was partially mitigated by electrochemical polishing of stainless steel components of the bioreactor. High concentrations of manganese (II) ions during early cultivation led to a reduction in citric acid yield. However, the effect of manganese (II) ions on the reduction of citric acid yield diminished towards the second half of the fermentation. Since maintaining low concentrations of manganese (II) ions is costly, the results of this study can potentially be used to modify protocols to reduce the cost of citric acid production.

The Biocontrol Potential of Endophytic Trichoderma Fungi Isolated from Hungarian Grapevines. Part I. Isolation, Identification and In Vitro Studies

This paper reports on the identification and in vitro characterization of several Trichoderma strains isolated from the Tokaj Wine Region in North-East Hungary. Ten isolates were analyzed and found to consist of six individual species—T. gamsii, T. orientale, T. simmonsii, T. afroharzianum, T. atrobrunneum and T. harzianum sensu stricto. The growth potential of the strains was assessed at a range of temperatures. We also report here on the in vitro biocontrol properties and fungicide tolerance of the most promising strains.

Carbon-Source Dependent Interplay of Copper and Manganese Ions Modulates the Morphology and Itaconic Acid Production in Aspergillus terreus

The effects of the interplay of copper(II) and manganese(II) ions on growth, morphology and itaconic acid formation was investigated in a high-producing strain of Aspergillus terreus (NRRL1960), using carbon sources metabolized either mainly via glycolysis (D-glucose, D-fructose) or primarily via the pentose phosphate shunt (D-xylose, L-arabinose). Limiting Mn²⁺ concentration in the culture broth is indispensable to obtain high itaconic acid yields, while in the presence of higher Mn²⁺ concentrations yield decreases and biomass formation is favored. However, this low yield in the presence of high Mn²⁺ ion concentrations can be mitigated by increasing the Cu²⁺ concentration in the medium when D-glucose or D-fructose is the growth substrate, whereas this effect was at best modest during growth on D-xylose or L-arabinose. A. terreus displays a high tolerance to Cu²⁺ which decreased when Mn²⁺ availability became increasingly limiting. Under such conditions biomass formation on D-glucose or D-fructose could be sustained at concentrations up to 250 mg L^–1 Cu²⁺, while on D-xylose- or L-arabinose biomass formation was completely inhibited at 100 mg L^–1. High (>75%) specific molar itaconic acid yields always coincided with an “overflow-associated” morphology, characterized by small compact pellets (<250 μm diameter) and short chains of “yeast-like” cells that exhibit increased diameters relative to the elongated cells in growing filamentous hyphae. At low concentrations (≤1 mg L^–1) of Cu²⁺ ions, manganese deficiency did not prevent filamentous growth. Mycelial- and cellular morphology progressively transformed into the typical overflow-associated one when external Cu²⁺ concentrations increased, irrespective of the available Mn²⁺. Our results indicate that copper ions are relevant for overflow metabolism and should be considered when optimizing itaconic acid fermentation in A. terreus.

The effects of external Mn2+ concentration on hyphal morphology and citric acid production are mediated primarily by the NRAMP-family transporter DmtA in Aspergillus niger

Background

Citric acid, a commodity product of industrial biotechnology, is produced by fermentation of the filamentous fungus Aspergillus niger. A requirement for high-yield citric acid production is keeping the concentration of Mn²⁺ ions in the medium at or below 5 µg L⁻¹. Understanding manganese metabolism in A. niger is therefore of critical importance to citric acid production. To this end, we investigated transport of Mn²⁺ ions in A. niger NRRL2270.

Results

we identified an A. niger gene (dmtA; NRRL3_07789), predicted to encode a transmembrane protein, with high sequence identity to the yeast manganese transporters Smf1p and Smf2p. Deletion of dmtA in A. niger eliminated the intake of Mn²⁺ at low (5 µg L⁻¹) external Mn²⁺ concentration, and reduced the intake of Mn²⁺ at high (> 100 µg L⁻¹) external Mn²⁺ concentration. Compared to the parent strain, overexpression of dmtA increased Mn²⁺ intake at both low and high external Mn²⁺ concentrations. Cultivation of the parent strain under Mn²⁺ ions limitation conditions (5 µg L⁻¹) reduced germination and led to the formation of stubby, swollen hyphae that formed compact pellets. Deletion of dmtA caused defects in germination and hyphal morphology even in the presence of 100 µg L⁻¹ Mn²⁺, while overexpression of dmtA led to enhanced germination and normal hyphal morphology at limiting Mn²⁺ concentration. Growth of both the parent and the deletion strains under citric acid producing conditions resulted in molar yields (Y_p/s) of citric acid of > 0.8, although the deletion strain produced ~ 30% less biomass. This yield was reduced only by 20% in the presence of 100 µg L⁻¹ Mn²⁺, whereas production by the parent strain was reduced by 60%. The Y_p/s of the overexpressing strain was 17% of that of the parent strain, irrespective of the concentrations of external Mn²⁺.

Conclusions

Our results demonstrate that dmtA is physiologically important in the transport of Mn²⁺ ions in A. niger, and manipulation of its expression modulates citric acid overflow.

Manganese Deficiency Is Required for High Itaconic Acid Production From D-Xylose in Aspergillus terreus

Itaconic acid is used as a bio-based, renewable building block in the polymer industry. It is produced by submerged fermentations of the filamentous fungus Aspergillus terreus from molasses or starch, but research over the efficient utilization of non-food, lignocellulosic plant biomass is soaring. The objective of this study was to test whether the application of two key cultivation parameters for obtaining itaconic acid from D-glucose in high yields - Mn2+ ion deficiency and high concentration of the carbon source - would also occur on D-xylose, the principal monomer of lignocellulose. To this end, a carbon and energy balance for itaconic acid formation was established, which is 0.83 moles/mole D-xylose. The effect of Mn2+ ions on itaconic acid formation was indeed similar to that on D-glucose and maximal yields were obtained below 3 μg L-1 Mn2+ ions, which were, however, only 0.63 moles of itaconic acid per mole D-xylose. In contrast to the case on D-glucose, increasing D-xylose concentration over 50 g L-1 did not change the above yield. By-products such as xylitol and α-ketoglutarate were found, but in total they remained below 2% of the concentration of D-xylose. Mass balance of the fermentation with 110 g L-1 D-xylose revealed that >95% of the carbon from D-xylose was accounted as biomass, itaconic acid, and the carbon dioxide released in the last step of itaconic acid biosynthesis. Our data show that the efficiency of biomass formation is the critical parameter for itaconic acid yield from D-xylose under otherwise optimal conditions.

Identification of a mutarotase gene involved in D-galactose utilization in Aspergillus nidulans

Aldose 1-epimerases or mutarotases (EC 5.1.3.3) are catalyzing the interconversion of α- and β-anomers of hemiacetals of aldose sugars such as D-glucose and D-galactose, and are presumed to play an auxiliary role in carbohydrate metabolism as mutarotation occurs spontaneously in watery solutions. The first step in the Leloir pathway of D-galactose breakdown is preceded by accelerated conversion of β-D-galactopyranose into the α-anomer, the substrate of the anomer-specific D-galactose 1-kinase. Here, we identified two putative aldose-1-epimerase genes (galmA and galmB) in the model organism Aspergillus nidulans, and characterized them upon generation of single- and double deletion mutant strains, as well as overexpressing mutants carrying multiple copies of either. Assaying cell-free extracts from the galmB single- and galm double mutants, we observed that the mutarotation hardly exceeded spontaneous anomer conversion, while galmB multicopy strains displayed higher activities than the wild type, increasing with the copy number. When grown on D-galactose in submerged cultures, biomass formation and D-galactose uptake rates in mutants lacking galmB were considerably reduced. None such effects were observed studying galmA deletion mutants, which consistently behave like the wild type. We conclude that GalmB is the physiologically relevant mutarotase for the utilization of D-galactose in A. nidulans.

Comparative genomics reveals high biological diversity and specific adaptations in the industrially and medically important fungal genus Aspergillus

BACKGROUND

The fungal genus Aspergillus is of critical importance to humankind. Species include those with industrial applications, important pathogens of humans, animals and crops, a source of potent carcinogenic contaminants of food, and an important genetic model. The genome sequences of eight aspergilli have already been explored to investigate aspects of fungal biology, raising questions about evolution and specialization within this genus.

RESULTS

We have generated genome sequences for ten novel, highly diverse Aspergillus species and compared these in detail to sister and more distant genera. Comparative studies of key aspects of fungal biology, including primary and secondary metabolism, stress response, biomass degradation, and signal transduction, revealed both conservation and diversity among the species. Observed genomic differences were validated with experimental studies. This revealed several highlights, such as the potential for sex in asexual species, organic acid production genes being a key feature of black aspergilli, alternative approaches for degrading plant biomass, and indications for the genetic basis of stress response. A genome-wide phylogenetic analysis demonstrated in detail the relationship of the newly genome sequenced species with other aspergilli.

CONCLUSIONS

Many aspects of biological differences between fungal species cannot be explained by current knowledge obtained from genome sequences. The comparative genomics and experimental study, presented here, allows for the first time a genus-wide view of the biological diversity of the aspergilli and in many, but not all, cases linked genome differences to phenotype. Insights gained could be exploited for biotechnological and medical applications of fungi.

Diversity of Cryphonectria parasitica populations from the Carpathian Basin

The ascomycetous fungus Cryphonectria parasitica (Murr.) is one of the most important fungal pathogens of chestnut (Castanea sativa Mill.), causing chestnut blight. It is originated from Eastern Asia and was introduced into North America, and later into Europe. Almost 100 C. parasitica isolates were collected mainly from the Carpathian Basin to study their diversity and phylogenetic relationships. Three nuclear molecular markers were tested: (i) internal transcribed spacers (ITS), (ii) translation elongation factor 1 subunit alpha (tef1), and (iii) six microsatellite loci. The ITS region proved to be highly polymorphic but this kind of variability did not reflect the geographical regions of the isolates, while the tef1 sequences were identical in all isolates. Microsatellite haplotype diversity was relatively high (0.923-0.984) calculated for the fungal populations of the Carpathian Basin. This may have resulted from the multiple introductions from diverse origins of the populations, close to the first site of observation in Northern Italy. The BAPS analysis of the microsatellite markers occasionally grouped together samples from remote geographical origin, suggesting human assistance in the introduction of new C. parasitica haplotypes from distinct areas.

High cell density cultivation of the chemolithoautotrophic bacterium Nitrosomonas europaea

Nitrosomonas europaea is a chemolithoautotrophic nitrifier, a gram-negative bacterium that can obtain all energy required for growth from the oxidation of ammonia to nitrite, and this may be beneficial for various biotechnological and environmental applications. However, compared to other bacteria, growth of ammonia oxidizing bacteria is very slow. A prerequisite to produce high cell density N. europaea cultures is to minimize the concentrations of inhibitory metabolic by-products. During growth on ammonia nitrite accumulates, as a consequence, N. europaea cannot grow to high cell concentrations under conventional batch conditions. Here, we show that single-vessel dialysis membrane bioreactors can be used to obtain substantially increased N. europaea biomasses and substantially reduced nitrite levels in media initially containing high amounts of the substrate. Dialysis membrane bioreactor fermentations were run in batch as well as in continuous mode. Growth was monitored with cell concentration determinations, by assessing dry cell mass and by monitoring ammonium consumption as well as nitrite formation. In addition, metabolic activity was probed with in vivo acridine orange staining. Under continuous substrate feed, the maximal cell concentration (2.79 × 10(12)/L) and maximal dry cell mass (0.895 g/L) achieved more than doubled the highest values reported for N. europaea cultivations to date.

The VELVET A orthologue VEL1 of Trichoderma reesei regulates fungal development and is essential for cellulase gene expression

Trichoderma reesei is the industrial producer of cellulases and hemicellulases for biorefinery processes. Their expression is obligatorily dependent on the function of the protein methyltransferase LAE1. The Aspergillus nidulans orthologue of LAE1 - LaeA - is part of the VELVET protein complex consisting of LaeA, VeA and VelB that regulates secondary metabolism and sexual as well as asexual reproduction. Here we have therefore investigated the function of VEL1, the T. reesei orthologue of A. nidulans VeA. Deletion of the T. reesei vel1 locus causes a complete and light-independent loss of conidiation, and impairs formation of perithecia. Deletion of vel1 also alters hyphal morphology towards hyperbranching and formation of thicker filaments, and with consequently reduced growth rates. Growth on lactose as a sole carbon source, however, is even more strongly reduced and growth on cellulose as a sole carbon source eliminated. Consistent with these findings, deletion of vel1 completely impaired the expression of cellulases, xylanases and the cellulase regulator XYR1 on lactose as a cellulase inducing carbon source, but also in resting mycelia with sophorose as inducer. Our data show that in T. reesei VEL1 controls sexual and asexual development, and this effect is independent of light. VEL1 is also essential for cellulase gene expression, which is consistent with the assumption that their regulation by LAE1 occurs by the VELVET complex.

Extra- and intracellular lactose catabolism in Penicillium chrysogenum: phylogenetic and expression analysis of the putative permease and hydrolase genes

Penicillium chrysogenum is used as an industrial producer of penicillin. We investigated its catabolism of lactose, an abundant component of whey used in penicillin fermentation, comparing the type strain NRRL 1951 with the high producing strain AS-P-78. Both strains grew similarly on lactose as the sole carbon source under batch conditions, exhibiting almost identical time profiles of sugar depletion. In silico analysis of the genome sequences revealed that P. chrysogenum features at least five putative β-galactosidase (bGal)-encoding genes at the annotated loci Pc22g14540, Pc12g11750, Pc16g12750, Pc14g01510 and Pc06g00600. The first two proteins appear to be orthologs of two Aspergillus nidulans family 2 intracellular glycosyl hydrolases expressed on lactose. The latter three P. chrysogenum proteins appear to be distinct paralogs of the extracellular bGal from A. niger, LacA, a family 35 glycosyl hydrolase. The P. chrysogenum genome also specifies two putative lactose transporter genes at the annotated loci Pc16g06850 and Pc13g08630. These are orthologs of paralogs of the gene encoding the high-affinity lactose permease (lacpA) in A. nidulans for which P. chrysogenum appears to lack the ortholog. Transcript analysis of Pc22g14540 showed that it was expressed exclusively on lactose, whereas Pc12g11750 was weakly expressed on all carbon sources tested, including D-glucose. Pc16g12750 was co-expressed with the two putative intracellular bGal genes on lactose and also responded on L-arabinose. The Pc13g08630 transcript was formed exclusively on lactose. The data strongly suggest that P. chrysogenum exhibits a dual assimilation strategy for lactose, simultaneously employing extracellular and intracellular hydrolysis, without any correlation to the penicillin-producing potential of the studied strains.

Phoma-like fungi on soybeans

Numerous coelomycetous fungi classified in Ascochyta, Phoma and Phyllosticta, and lately established and/or re-classified genera and species, namely Boeremia and Peyronellaea have been recorded from spots on leaves and pods of soybeans. These rarely observed pathogens are cosmopolitan, ubiquitous species on diseased and dead plant materials, and define frequently as weak or opportunistic parasites. Based on the Genealogical Concordance Phylogenetic Species Recognition, the authors summarize the re-evaluation of the taxonomic status of Phoma sojicola (syn. Ascochyta sojicola) and Phyllosticta sojicola. Inspite of the former delimitation of Ph. sojicola based on small differences in morphological features, it has proved to be identical to Peyronellaea pinodella (syn. Phoma pinodella). Similarly, it was also confirmed that Ph. sojicola was identical to Boeremia exigua var. exigua (syn. Phoma exigua var. exigua). The authors and co-workers contributed to the identification of Phoma-like fungi by combined conventional and molecular methods. Protein-encoding genes (TEF1 and β-tubulin) were successfully applied within the Phoma genus to infer phylogenetic relationships.

Comparison of Botrytis cinerea populations isolated from two open-field cultivated host plants

The necrotrophic fungus Botrytis cinerea is reported to infect more than 220 host plants worldwide. In phylogenetical-taxonomical terms, the pathogen is considered a complex of two cryptic species, group I and group II. We sampled populations of B. cinerea on sympatric strawberry and raspberry cultivars in the North-East of Hungary for three years during flowering and the harvest period. Four hundred and ninety group II B. cinerea isolates were analyzed for the current study. Three different data sets were generated: (i) PCR-RFLP patterns of the ADP-ATP translocase and nitrate reductase genes, (ii) MSB1 minisatellite sequence data, and (iii) the fragment sizes of five microsatellite loci. The structures of the different populations were similar as indicated by Nei's gene diversity and haplotype diversity. The F statistics (Fst, Gst), and the gene flow indicated ongoing differentiation within sympatric populations. The population genetic parameters were influenced by polymorphisms within the three data sets as assessed using Bayesian algorithms. Data Mining analysis pointed towards the five microsatellite loci as the most defining markers to study differentiation in the 490 isolates. The results suggest the occurrence of host-specific, sympatric divergence of generalist phytoparasites in perennial hosts.

D-Galactose uptake is nonfunctional in the conidiospores of Aspergillus niger

The majority of black Aspergilli (Aspergillus section Nigri), including Aspergillus niger, as well as many other Ascomycetes fail to germinate on d-galactose as a sole carbon source. Here, we provide evidence that the ability of A. niger to transport D-galactose is growth stage dependent, being absent in the conidiospores but present in the mycelia. Despite earlier claims, we could identify galactokinase activity in growing cells and all genes of the Leloir pathway (responsible for channelling D-galactose into the EMP pathway) are well induced on D-galactose (and also on lactose, D-xylose and L-arabinose) in the mycelial stage. Expression of all Leloir pathway genes was also detectable in conidiospores, although galE (encoding a galactokinase) and galD (encoding a galactose-1-phosphate uridylyl transferase) were expressed poorly. These results suggest that the D-galactose-negative phenotype of A. niger conidiospores may be due to the lack of inducer uptake.

The CRE1 carbon catabolite repressor of the fungus Trichoderma reesei: a master regulator of carbon assimilation

BACKGROUND

The identification and characterization of the transcriptional regulatory networks governing the physiology and adaptation of microbial cells is a key step in understanding their behaviour. One such wide-domain regulatory circuit, essential to all cells, is carbon catabolite repression (CCR): it allows the cell to prefer some carbon sources, whose assimilation is of high nutritional value, over less profitable ones. In lower multicellular fungi, the C2H2 zinc finger CreA/CRE1 protein has been shown to act as the transcriptional repressor in this process. However, the complete list of its gene targets is not known.

RESULTS

Here, we deciphered the CRE1 regulatory range in the model cellulose and hemicellulose-degrading fungus Trichoderma reesei (anamorph of Hypocrea jecorina) by profiling transcription in a wild-type and a delta-cre1 mutant strain on glucose at constant growth rates known to repress and de-repress CCR-affected genes. Analysis of genome-wide microarrays reveals 2.8% of transcripts whose expression was regulated in at least one of the four experimental conditions: 47.3% of which were repressed by CRE1, whereas 29.0% were actually induced by CRE1, and 17.2% only affected by the growth rate but CRE1 independent. Among CRE1 repressed transcripts, genes encoding unknown proteins and transport proteins were overrepresented. In addition, we found CRE1-repression of nitrogenous substances uptake, components of chromatin remodeling and the transcriptional mediator complex, as well as developmental processes.

CONCLUSIONS

Our study provides the first global insight into the molecular physiological response of a multicellular fungus to carbon catabolite regulation and identifies several not yet known targets in a growth-controlled environment.

Taxonomical re-evaluation of Phoma-like soybean pathogenic fungi

Coelomycetous fungi classified in Ascochyta, Phoma, and Phyllosticta have been recorded from spots on leaves and pods of soybeans. Based on the Genealogical Concordance Phylogenetic Species Concept, the authors suggest the re-evaluation of the taxonomic status of Phoma sojicola (syn.=Ascochyta sojicola) and Phyllosticta sojicola. In spite of the former delimitation of Phoma sojicola based on small differences in morphological features, it has proved to be identical to Phoma pinodella. Similarly, it was also confirmed that Phyllosticta sojicola was identical to Phoma exigua var. exigua. The authors supply tools for identification of Phoma-like fungi by combined conventional and molecular methods. Protein-encoding genes (tef1 and beta-tubulin) were successfully applied within the Phoma genus to infer phylogenetic relationships.

Sexual recombination in the Botrytis cinerea populations in Hungarian vineyards

Botrytis cinerea (anamorph of Botryotinia fuckeliana) causes gray mold on a high number of crop plants including grapes. In this study, we investigated the genetic properties of a grape pathogenic population of B. cinerea in the area of Eger, Hungary. A total of 109 isolates from 12 areas were sampled. Based on the sequence of the beta-tubulin (tub1) locus, they all belong to group II, a phylogenetic species within B. cinerea. Seventy-four isolates were classified as transposa, with both the Flipper and Boty transposons, and 10 were classified as vacuma, lacking both transposons. The remaining isolates contained either only Flipper (13) or Boty (12). Multilocus analysis of sequences from tub1 and two other loci (elongation factor 1-alpha, tef1, and a minisatellite from the intron of an ATPase, MSB1) led to poor phylogenetic resolution of strains in individual clades. Analysis of five microsatellites (Bc2, Bc3, Bc5, Bc6, and Bc10) resulted in 55 microsatellite haplotypes within the 109 strains. No correlation was detected among individual haplotypes and the presence/absence of Flipper and/or Boty, the geographic origin, or the year of isolation. Application of the index of association, the chi-square test, and the phi test consistently indicated that the population of Hungarian isolates of B. cinerea undergoes sexual reproduction. However, the index of association test suggested the presence of some clonality, and the fixation index showed a low or occasionally moderate level of fixation in the Flipper populations. We conclude that the B. cinerea populations in Hungary consist of a strongly recombining group II phylogenetic species.

Facts and Challenges in the Understanding of the Biosynthesis of Peptaibols byTrichoderma

Species of the mitosporic filamentous fungal genus Trichoderma are prominent producers of both short (7-11 residues) and long (18-20 residues) peptaibols and peptaibiotics, which are thought to be involved in their interaction with other living systems. Numerous reviews are available regarding biodiversity, structure, and mode of action of these peptide derivatives, but little emphasis has been paid to the physiology and genetics of their formation. In this review article, we used the recent knowledge on biosynthesis and production of these components to speculate on some of the unknown points. We also highlight areas where further research is most urgently needed.

CreA-mediated carbon catabolite repression of $beta;-galactosidase formation in Aspergillus nidulans is growth rate dependent

Carbon catabolite repression by the CreA-transcriptional repressor is widespread in filamentous fungi, but the mechanism by which glucose triggers carbon catabolite repression is still poorly understood. We investigated the hypothesis that the growth rate on glucose may control CreA-dependent carbon catabolite repression by using glucose-limited chemostat cultures and the intracellular beta-galactosidase activity of Aspergillus nidulans, which is repressed by glucose, as a model system. Chemostat cultures at four different dilution rates (D = 0.095, 0.068, 0.045 and 0.015 h-1) showed that formation of beta-galactosidase activity is repressed at the two highest Ds, but increasingly derepressed at the lower Ds, the activity at 0.015 h-1 equalling that in derepressed batch cultures. Chemostat cultures with the carbon catabolite derepressed A. nidulans mutant strain creADelta4 revealed a dilution-rate independent constant beta-galactosidase activity of the same range as that found in the wild-type strain at D = 0.015 h-1. Two other enzymes--isocitrate lyase, which is almost absent on glucose due to a CreA-independent mechanism; and galactokinase, which is formed constitutively and independent of CreA--were measured as controls. They were formed at constant activity at each dilution rate, both in the wild-type strain as well as in the carbon catabolite derepressed mutant strain. We conclude that the growth rate on glucose is a determinant of carbon catabolite repression in A. nidulans, and that below a certain growth rate carbon catabolite derepression occurs.

The alternative D-galactose degrading pathway of Aspergillus nidulans proceeds via L-sorbose

The catabolism of d-galactose in yeast depends on the enzymes of the Leloir pathway. In contrast, Aspergillus nidulans mutants in galactokinase ( galE) can still grow on d-galactose in the presence of ammonium-but not nitrate-ions as nitrogen source. A. nidulans galE mutants transiently accumulate high (400 mM) intracellular concentrations of galactitol, indicating that the alternative d-galactose degrading pathway may proceed via this intermediate. The enzyme degrading galactitol was identified as l-arabitol dehydrogenase, because an A. nidulans loss-of-function mutant in this enzyme ( araA1) did not show NAD(+)-dependent galactitol dehydrogenase activity, still accumulated galactitol but was unable to catabolize it thereafter, and a double galE/araA1 mutant was unable to grow on d-galactose or galactitol. The product of galactitol oxidation was identified as l-sorbose, which is a substrate for hexokinase, as evidenced by a loss of l-sorbose phosphorylating activity in an A. nidulans hexokinase ( frA1) mutant. l-Sorbose catabolism involves a hexokinase step, indicated by the inability of the frA1 mutant to grow on galactitol or l-sorbose, and by the fact that a galE/frA1 double mutant of A. nidulans was unable to grow on d-galactose. The results therefore provide evidence for an alternative pathway of d-galactose catabolism in A. nidulans that involves reduction of the d-galactose to galactitol and NAD(+)-dependent oxidation of galactitol by l-arabitol dehydrogenase to l-sorbose.

Glutathione metabolism of Acremonium chrysogenum in relation to cephalosporin C production: is gamma-glutamyltransferase in the center?

Methionine increased the intracellular glutathione (reduced) (GSH) pool and the specific gamma-glutamyltransferase (gamma-GT) activity in the cephalosporin C (CPC) producer Acremonium chrysogenum. The accelerated turnover of GSH might be indicative of the existence of a functioning gamma-glutamate cycle, and might supply the CPC biosynthetic machinery with L-cysteine. The gamma-GT was not subject to nitrogen metabolic repression but was more active in cells exposed to different oxidative-stress-generating agents. Exogenous cysteine hindered both the uptake of methionine and the induction of gamma-GT, and was not beneficial for CPC production. There was no causal relationship between the redox status of the cells and the observed cell morphology.

Stimulation of the cyanide-resistant alternative respiratory pathway by oxygen in Acremonium chrysogenum correlates with the size of the intracellular peroxide pool

The relationship between oxygen input and activity of the cyanide-resistant alternative respiration of submerged cultures of Acremonium crysogenum was investigated. The volumetric oxygen transfer coefficient of the respective cultures correlated positively within almost two ranges of magnitude with the size of the intracellular peroxide pool, which in turn, correlated with the activity of the cyanide-resistant alternative respiratory pathway. Increased aeration also stimulated the glucose uptake rate but had no effect on the total respiration rate or the growth rate. Addition of the lipid peroxyl radical scavenger DL-alpha-tocopherol to A. chrysogenum cultures decreased the rate of intracellular peroxide production as well as glucose uptake. An increase in the cyanide-resistant fraction of total respiration was observed, while growth and the total respiratory activity remained unchanged. We conclude that intracellular peroxides may stimulate the alternative respiration in A. chrysogenum.

The Hypocrea jecorina gal10 (uridine 5'-diphosphate-glucose 4-epimerase-encoding) gene differs from yeast homologues in structure, genomic organization and expression

As part of a comprehensive study on lactose metabolism in Hypocrea jecorina (anamorph: Trichoderma reesei), a genomic clone of the gal10 gene encoding H. jecorina uridine 5'-diphosphate (UDP)-glucose 4-epimerase has been cloned and sequenced. It contains an open reading frame of 1548-base pair, interrupted by three introns, and encoding a 370-amino acids protein with similarity to pro- and eukaryotic UDP-glucose-4-epimerases. H. jecorina Gal10 does not contain the C-terminal mutarotase domain which is present in yeast Gal10 proteins but is able to functionally complement a corresponding Saccharomyces cerevisiae gal10 mutant. gal10 is not clustered with other H. jecorina gal genes (gal7, gene encoding galactose-1-phosphate uridylyltransferase and gal1, gene encoding galactokinase). The genomic location of H. jecorina gal10 and gal7 was syntenic with that in Neurospora crassa and colinear over an area of 6 and 3.5-kilobase. gal10 is constitutively expressed, and--unlike H. jecorina gal7--not further stimulated by D-galactose or L-arabinose or its corresponding polyols.

Regulation of formation of the intracellular beta-galactosidase activity of Aspergillus nidulans

The regulation of formation of the single intracellular beta-galactosidase activity of Aspergillus nidulans was investigated. beta-Galactosidase was not formed during growth on glucose or glycerol, but was rapidly induced during growth on lactose or D-galactose. L-Arabinose, and -- with lower efficacy -- D-xylose also induced beta-galactosidase activity. Addition of glucose to cultures growing on lactose led to a rapid decrease in beta-galactosidase activity. In contrast, in cultures growing on D-galactose, addition of glucose decreased the activity of beta-galactosidase only slightly. Glucose inhibited the uptake of lactose, but not of D-galactose, and required the carbon catabolite repressor CreA for this. In addition, CreA also repressed the formation of basal levels of beta-galactosidase and partially interfered with the induction of beta-galactosidase by D-galactose, L-arabinose, and D-xylose. D-Galactose phosphorylation was not necessary for beta-galactosidase induction, since induction by D-galactose occurred in an A. nidulans mutant defective in galactose kinase, and by the non-metabolizable D-galactose analogue fucose in the wild-type strain. Interestingly, a mutant in galactose-1-phosphate uridylyl transferase produced beta-galactosidase at a low, constitutive level even on glucose and glycerol and was no longer inducible by D-galactose, whereas it was still inducible by L-arabinose. We conclude that biosynthesis of the intracellular beta-galactosidase of A. nidulans is regulated by CreA, partially repressed by galactose-1-phosphate uridylyl transferase, and induced by D-galactose and L-arabinose in independent ways.

The biochemistry of citric acid accumulation by Aspergillus niger

Fungi, in particular Aspergilli, are well known for their potential to overproduce a variety of organic acids. These microorganisms have an intrinsic ability to accumulate these substances and it is generally believed that this provides the fungi with an ecological advantage, since they grow rather well at pH 3 to 5, while some species even tolerate pH values as low as 1.5. Organic acid production can be stimulated and in a number of cases conditions have been found that result in almost quantitative conversion of carbon substrate into acid. This is exploited in large-scale production of a number of organic acids like citric-, gluconic- and itaconic acid. Both in production volume as well as in knowledge available, citrate is by far the major organic acid. Citric acid (2-hydroxy-propane-1,2,3-tricarboxylic acid) is a true bulk product with an estimated global production of over 900 thousand tons in the year 2000. Till the beginning of the 20th century, it was exclusively extracted from lemons. Since the global market was dominated by an Italian cartel, other means of production were sought. Chemical synthesis was possible, but not suitable due to expensive raw materials and a complicated process with low yield. The discovery of citrate accumulation by Aspergillus niger led to a rapid development of a fermentation process, which only a decade later accounted for a large part of the global production. The application of citric acid is based on three of its properties: (1) acidity and buffer capacity, (2) taste and flavour, and (3) chelation of metal ions. Because of its three acid groups with pKa values of 3.1, 4.7 and 6.4, citrate is able to produce a very low pH in solution, but is also useful as a buffer over a broad range of pH values (2 to 7). Citric acid has a pleasant acid taste which leaves little aftertaste. It sometimes enhances flavour, but is also able to mask sweetness, such as the aspartame taste in diet beverages. Chelation of metal ions is a very important property that has led to applications such as antioxidant and preservative. Moreover, it is a "natural" substance and fully biodegradable.

Analysis of the relationship between growth, cephalosporin C production, and fragmentation in Acremonium chrysogenum

Mycelial fragmentation in submerged cultures of the cephalosporin C (CPC) producing fungus Acremonium chrysogenum was characterized by image analysis. In both fed-batch and chemostat cultures, the proportion of mycelial clumps seemed to be the most sensitive morphological indicator of fragmentation. In a fed-batch fermentation culture, this declined from roughly 60% at inoculation to less than 10% after 43 h. Subsequent additions of glucose resulted in a sharp increase back to near the initial value, an increase that reversed itself a few hours after glucose exhaustion. Meanwhile CPC production continued to decline steadily. On the other hand, the addition of soybean oil enhanced CPC production, but had no significant effect on the morphology. Although it may sometimes appear that morphology and productivity are related in batch or fed-batch cultures, this study suggests that this is because both respond simultaneously to more fundamental physiological changes, dependent on the availability of carbon. In circumstances, such as supplementary carbon source addition, the relationship is lost. Chemostat cultures supported this belief, as CPC-production rates were hardly affected by the specific growth rate, but the morphology showed significant differences, i.e., lower dilution rates resulted in a lower proportion of clumps and in smaller clumps.

Cyanide-resistant alternative respiration is strictly correlated to intracellular peroxide levels in Acremonium chrysogenum

A strict correlation between the intensity of the cyanide-resistant alternative respiratory pathway and the intracellular peroxide levels in the cephalosporin C producer filamentous fungus Acremonium chrysogenum was demonstrated. Intracellular peroxide levels increased in a dose-dependent manner after addition of H2O2 to the culture media. A similar phenomenon was observed due to the specific inhibition of catalase by salicylic acid. In both cases, cyanide-resistant respiration was markedly stimulated. On the other hand, both cyanide-resistant respiration and intracellular peroxide levels were effectively suppressed by the lipid peroxyl radical scavenger DL-alpha-tocopherol, which breaks lipid peroxidation chains effectively. Our findings firmly supported the assumption that there is a connection between the intracellular peroxide levels and the intensity of the alternative respiratory pathway in fungi.

The role of the alternative respiratory pathway in the stimulation of cephalosporin C formation by soybean oil in Acremonium chrysogenum

Addition of soybean oil to Acremonium chrysogenum cultures growing on sugars doubled the specific production of cephalosporin C during the idiophase of growth. While the addition of soybean oil had no effect on the total rate of respiration, the respiration that proceeded via the alternative, cyanide-insensitive pathway exhibited a more than twofold increase. Addition of soybean oil also stimulated the formation of isocitrate lyase activities. Inhibition of oxidative metabolism of one of the products of isocitrate lyase (succinate) by thenoyltrifluoroacetone completely inhibited the alternative respiratory pathway. The role of soybean-oil-stimulated alternative respiration in the stimulation of cephalosporin C production and the role of isocitrate lyase are discussed.

Allosamidin inhibits the fragmentation of Acremonium chrysogenum but does not influence the cephalosporin-C production of the fungus

The pseudotrisaccharide allosamidin, a potent inhibitor of chitinases, retarded the fragmentation of hyphae but did not affect the fungal growth and cephalosporin-C production in Acremonium chrysogenum. In vitro inhibition of A. chrysogenum cell-bound chitinase(s) by allosamidin revealed that about 47% of the soluble intracellular chitinase activity was resistant to the inhibitory effect of allosamidin. On the other hand, about 76% of the total chitinase activity localised in both the soluble and insoluble enzyme fractions was effectively inhibited by allosamidin. All the chitinase activities were measured using a new procedure based on purified A. chrysogenum chitin as substrate.

Development of ELISA and enzyme-linked immunofiltration assay (ELIFA) methods for monitoring cyclodextrin glycosyltransferase (CGTase) production and bacterial growth in Bacillus macerans batch cultures

Immunochemical methods were developed for monitoring cyclodextrin (CD) glycosyltransferase (CGTase) production and growth of an industrial CD-producing Bacillus macerans strain. Extracellular concentrations of CGTase released into a non-transparent culture medium during a 44 h long fermentation were detected by an indirect antigen inhibition enzyme-linked immunosorbent assay (ELISA). The ELISA was sensitive (minimal detection level 6 ng ml-1) and highly reproducible (coefficients of variation < or = 1.2 and 5.9%, within-runs and between-runs, respectively) compared to assays of CGTase activity (coefficients of variation < or = 4.2 and 7.0%, respectively). The ELISA, in combination with enzyme activity measurements, was useful to detect the decrease in the specific CGTase activities after 36 h of incubation, which was clearly indicative of the proteolytic degradation of CGTase. B. macerans cell numbers were estimated using an enzyme-linked immunofilter assay (ELIFA). The assay took less than 1 h and the coefficients of variation within and between-runs (2.9-6.4%) were considerably less than for viable counting (10.6-15.4%). In the exponential phase of growth, ELIFA results correlated more closely with the cell counting based on total protein than with viable counts. Nevertheless, in the phase of cell lysis, the bacterial cell number was systematically underestimated by ELIFA in comparison to both viable cell number and total protein determinations. Thus cell antigens detected with immunological procedures might be lost during the transition from vegetative cells to spores. On the other hand, the ELIFA procedure was specific for B. macerans cells and was a better indicator of the onset of the different growth phases than the cell numbers calculated from the protein assay.

Dehydroepiandrosterone, dehydroepiandrosterone sulphate, and their relation to cortisol in red deer (Cervus elaphus)

Adrenal androgens, dehydroepiandrosterone, its sulphate and, in comparison, cortisol in serum were determined over two periods in red deer. The hormone levels were determined in hinds farmed from their births, captured in adulthood, and in fawns reared under farm conditions with their mothers or under artificial farm conditions without their mothers. In addition, steroid levels were studied in stags under farm conditions in and after the breeding season. Investigation of animals for their potential as farmed animals gave information on the stress susceptibility. It is suggested that the present assessment of hormonal events will provide prognostic information on their adaptation to farm conditions, reproductive performance, and possibly, their immune responses and the quality of their products.