Species-specific effects of the introduction of Aspergillus nidulans gfdB in osmophilic aspergilli

Industrial fungi need a strong environmental stress tolerance to ensure acceptable efficiency and yields. Previous studies shed light on the important role that Aspergillus nidulans gfdB, putatively encoding a NAD⁺-dependent glycerol-3-phosphate dehydrogenase, plays in the oxidative and cell wall integrity stress tolerance of this filamentous fungus model organism. The insertion of A. nidulans gfdB into the genome of Aspergillus glaucus strengthened the environmental stress tolerance of this xerophilic/osmophilic fungus, which may facilitate the involvement of this fungus in various industrial and environmental biotechnological processes. On the other hand, the transfer of A. nidulans gfdB to Aspergillus wentii, another promising industrial xerophilic/osmophilic fungus, resulted only in minor and sporadic improvement in environmental stress tolerance and meanwhile partially reversed osmophily. Because A. glaucus and A. wentii are phylogenetically closely related species and both fungi lack a gfdB ortholog, these results warn us that any disturbance of the stress response system of the aspergilli may elicit rather complex and even unforeseeable, species-specific physiological changes. This should be taken into consideration in any future targeted industrial strain development projects aiming at the fortification of the general stress tolerance of these fungi. KEY POINTS: • A. wentii c' gfdB strains showed minor and sporadic stress tolerance phenotypes. • The osmophily of A. wentii significantly decreased in the c' gfdB strains. • Insertion of gfdB caused species-specific phenotypes in A. wentii and A. glaucus.

Fungal Stress Database (FSD)--a repository of fungal stress physiological data

The construction of the Fungal Stress Database (FSD) was initiated and fueled by two major goals. At first, some outstandingly important groups of filamentous fungi including the aspergilli possess remarkable capabilities to adapt to a wide spectrum of environmental stress conditions but the underlying mechanisms of this stress tolerance have remained yet to be elucidated. Furthermore, the lack of any satisfactory interlaboratory standardization of stress assays, e.g. the widely used stress agar plate experiments, often hinders the direct comparison and discussion of stress physiological data gained for various fungal species by different research groups. In order to overcome these difficulties and to promote multilevel, e.g. combined comparative physiology-based and comparative genomics-based, stress research in filamentous fungi, we constructed FSD, which currently stores 1412 photos taken on Aspergillus colonies grown under precisely defined stress conditions. This study involved altogether 18 Aspergillus strains representing 17 species with two different strains for Aspergillus niger and covered six different stress conditions. Stress treatments were selected considering the frequency of various stress tolerance studies published in the last decade in the aspergilli and included oxidative (H₂O₂, menadione sodium bisulphite), high-osmolarity (NaCl, sorbitol), cell wall integrity (Congo Red) and heavy metal (CdCl₂) stress exposures. In the future, we would like to expand this database to accommodate further fungal species and stress treatments.

URL: http://www.fung-stress.org/

Duplications and losses of genes encoding known elements of the stress defence system of the Aspergilli contribute to the evolution of these filamentous fungi but do not directly influence their environmental stress tolerance

The contribution of stress protein duplication and deletion events to the evolution of the Aspergilli was studied. We performed a large-scale homology analysis of stress proteins and generated and analysed three stress defence system models based on Saccharomyces cerevisiae, Schizosaccharomyces pombe and Aspergillus nidulans. Although both yeast-based and A. nidulans-based models were suitable to trace evolutionary changes, the A. nidulans-based model performed better in mapping stress protein radiations. The strong Mantel correlation found between the positions of species in the phylogenetic tree on the one hand and either in the A. nidulans-based or S. cerevisiae-based models on the other hand demonstrated that stress protein expansions and reductions contributed significantly to the evolution of the Aspergilli. Interestingly, stress tolerance attributes correlated well with the number of orthologs only for a few stress proteins. Notable examples are Ftr1 iron permease and Fet3 ferro-O2-oxidoreductase, elements of the reductive iron assimilation pathway, in the S. cerevisiae-based model, as well as MpkC, a HogA-like mitogen activated protein kinase in the A. nidulans-based model. In the case of the iron assimilation proteins, the number of orthologs showed a positive correlation with H2O2-induced stress tolerance while the number of MpkC orthologs correlated positively with Congo Red induced cell wall stress, sorbitol induced osmotic stress and H2O2 induced oxidative stress tolerances. For most stress proteins, changes in the number of orthologs did not correlate well with any stress tolerance attributes. As a consequence, stress tolerance patterns of the studied Aspergilli did not correlate with either the sets of stress response proteins in general or with the phylogeny of the species studied. These observations suggest that stress protein duplication and deletion events significantly contributed to the evolution of stress tolerance attributes of Aspergilli. In contrast, there are other processes, which may counterbalance the effects of stress gene duplications or deletions including (i) alterations in the structures of stress proteins leading to changes in their biological activities, (ii) varying biosynthesis of stress proteins, (iii) rewiring stress response regulatory networks or even (iv) acquiring new stress response genes by horizontal gene transfer. All these multilevel changes are indispensable for the successful adaptation of filamentous fungi to altering environmental conditions, especially when these organisms are entering new ecological niches.

Physiological background of the remarkably high Cd2+ tolerance of the Aspergillus fumigatus Af293 strain

The physiological background of the unusually high cadmium tolerance (MIC₅₀  > 2 mM) of Aspergillus fumigatus Af293 was investigated. The cadmium tolerance of the tested environmental and clinical A. fumigatus strains varied over a wide range (0.25 mM < MIC₅₀  < 1 mM). Only the Af293 strain showed a MIC₅₀ value of >2 mM, and this phenotype was accompanied by increased in vivo virulence in mice. A strong correlation was found between the cadmium tolerance and the transcription of the pcaA gene, which encodes a putative cadmium efflux pump. The cadmium tolerance also correlated with the iron tolerance and the extracellular siderophore production of the strains. In addition to these findings, Af293 did not show the synergism between iron toxicity and cadmium toxicity that was detected in the other strains. Based on these results, we suggest that the primary function of PcaA should be acting as a ferrous iron pump and protecting cells from iron overload. Nevertheless, the heterologous expression of pcaA may represent an attractive strain improvement strategy to construct fungal strains for use in biosorption or biomining processes or to prevent accumulation of this toxic metal in crops.

Study on the glutathione metabolism of the filamentous fungus Aspergillus nidulans

Yeast protein sequence-based homology search for glutathione (GSH) metabolic enzymes and GSH transporters demonstrated that Aspergillus nidulans has a robust GSH uptake and metabolic system with several paralogous genes. In wet laboratory experiments, two key genes of GSH metabolism, gcsA, and glrA, encoding γ-l-glutamyl-l-cysteine synthetase and glutathione reductase, respectively, were deleted. The gene gcsA was essential, and the ΔgcsA mutant required GSH supplementation at considerably higher concentration than the Saccharomyces cerevisiae gsh1 mutant (8-10 mmol l^-1 vs. 0.5 μmol l^-1). In addition to some functions known previously, both genes were important in the germination of conidiospores, and both gene deletion strains required the addition of extra GSH to reach wild-type germination rates in liquid cultures. Nevertheless, the supplementation of cultures with 10 mmol l^-1 GSH was toxic for the control and ΔglrA strains especially during vegetative growth, which should be considered in future development of high GSH-producer fungal strains. Importantly, the ΔglrA strain was characterized by increased sensitivity toward a wide spectrum of osmotic, cell wall integrity and antimycotic stress conditions in addition to previously reported temperature and oxidative stress sensitivities. These novel phenotypes underline the distinguished functions of GSH and GSH metabolic enzymes in the stress responses of fungi.

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.

Core oxidative stress response in Aspergillus nidulans

BACKGROUND

The b-Zip transcription factor AtfA plays a key role in regulating stress responses in the filamentous fungus Aspergillus nidulans. To identify the core regulons of AtfA, we examined genome-wide expression changes caused by various stresses in the presence/absence of AtfA using A. nidulans microarrays. We also intended to address the intriguing question regarding the existence of core environmental stress response in this important model eukaryote.

RESULTS

Examination of the genome wide expression changes caused by five different oxidative stress conditions in wild type and the atfA null mutant has identified a significant number of stereotypically regulated genes (Core Oxidative Stress Response genes). The deletion of atfA increased the oxidative stress sensitivity of A. nidulans and affected mRNA accumulation of several genes under both unstressed and stressed conditions. The numbers of genes under the AtfA control appear to be specific to a stress-type. We also found that both oxidative and salt stresses induced expression of some secondary metabolite gene clusters and the deletion of atfA enhanced the stress responsiveness of additional clusters. Moreover, certain clusters were down-regulated by the stresses tested.

CONCLUSION

Our data suggest that the observed co-regulations were most likely consequences of the overlapping physiological effects of the stressors and not of the existence of a general environmental stress response. The function of AtfA in governing various stress responses is much smaller than anticipated and/or other regulators may play a redundant or overlapping role with AtfA. Both stress inducible and stress repressive regulations of secondary metabolism seem to be frequent features in A. nidulans.

Evolution of a regional health-care information system--the design phase

In 1996 a program of the Soros Foundation was launched to study a regional health care inodel Main stake holders of health care financing and providing in three counties in South-Western Hungary found the idea appealing and the Soros Model Region Program was started. This paper outlines the activity of the second sub-project of the model region program: the development of a regional health care information system. The build-up of a data and knowledge base serving the differing needs of mentioned goals is based on international standards. Availability and user involvement is based on different media for presenting the information as printed publications, CD-ROM data bases and World Wide Web availability. A congruency and coherency principle is maintained by a unified data model used for different purposes and a planned unified communication protocol among all participants in the model region program. Studies regarding health care status, economics and financing on regional level show that a better fitting health care services profile and a more flexible resource management might be achieved based on the mentioned regionality principle.

The impact of social science research on health policy

The relationship between research and health policy is discussed from a policy process perspective, describing communication problems in the course of policy formulation, implementation and evaluation. Policy process is often expected by researchers to be rational, having logical sequence of steps and the objective evaluation of alternatives based on scientific knowledge. In fact, policies are often formulated without clear problem identification or based on wrong assumption. The timing of research and policy-making differs. Policy-makers need to respond quickly. Evaluations may be regarded by politicians as embarrassing if they point to a need for significant change. It is not satisfactory to consider only research and policy-making: their relationship is influenced by the media, different interest groups and by the general public. Health policy formulation is embedded in the general policy environment of particular societies. Some countries have a long tradition of consensus-building, while in others health reforms have been formulated and introduced in a centralized way. Traditional bio-medical thinking influences health policy-makers. The importance of social and political acceptability tends to be overlooked. The paper emphasizes that we are experiencing an era of scarcity of resources and growing tension concerning allocation decisions. Existing institutions provide insufficient incentives for policy-makers and researchers to promote public dialogue about such issues. The paper concludes that there is a need for new approaches to policy development and implementation, new structures in policy-making, changes in research financing and co-operation between disciplines and new structures for public participation in policy-making. Research should facilitate more open and democratic dialogue about policy options and the consequences of alternative choices.

Characterization of aarA, a pleiotrophic negative regulator of the 2'-N-acetyltransferase in Providencia stuartii

We have utilized transposon mutagenesis to obtain insertional mutations in Providencia stuartii that activate the chromosomal aac(2')-la gene. Two closely linked mini-Tn5Cm insertions were obtained in a locus designated aarA, and a single insertion was obtained in a separate locus, aarC. Nucleotide sequence analysis, complementation studies, and localization of the sites of mini-Tn5Cm insertion have allowed the identification of the aarA coding region. The deduced AarA protein had a molecular mass of 31,086 kDa and displayed characteristics of an integral membrane protein. A strain deleted for the aarA gene by allelic exchange showed at least a fourfold increase in the accumulation of aac(2')-la mRNA and an eightfold increase in aminoglycoside resistance. Mutations in aarA were pleiotrophic and also resulted in loss of pigmentation and a deficiency in cell separation during division.

[Non-traumatic intrahepatic bile-duct perforation in an adult]

Authors report a case of a patient suffered from intrahepatic bile duct perforation caused by stenosis of the papilla of Vater. With the help of data of medical literature there are analysed the etiological factors of bile duct perforations and the pathological process that leads to perforation. There is emphasized that the only way to avoid the sepsis and other postoperative complications on operation carried out in an early time and the supplemented intensive care. Authors call attention for the importance of carefully carried out intraoperative revision of bile system in cases of biliary peritonitis.

Characterization and transcriptional regulation of the 2'-N-acetyltransferase gene from Providencia stuartii

We have cloned the chromosomally encoded 2'-N-acetyltransferase gene [aac(2')-Ia] from Providencia stuartii. DNA sequence analysis of the cloned insert identified a single open reading frame, which is capable of encoding a protein with a predicted molecular mass of 20,073 Da. The deduced AAC(2')-Ia protein showed no significant homology to other proteins, including all of the AAC(3) and AAC(6') proteins. Primer extension analysis was used to identify the aac(2')-Ia promoter, which contained an unusual sequence (CTTTTT) at the -35 region. Expression of the aac(2')-Ia gene occurs at low levels in wild-type P. stuartii strains; therefore, they are aminoglycoside susceptible. We have isolated mutants with high-level AAC(2')-Ia expression at a frequency of 4.8 x 10(-6). Detailed analysis of one mutant demonstrated a 12.2-fold increase in the accumulation of aac(2')-Ia mRNA. In addition, the levels of beta-galactosidase expression from a plasmid-encoded aac(2')-lacZ transcriptional fusion were increased 11.5-fold in this mutant relative to those in an isogenic wild-type strain. These results suggested that a trans-acting factor, designated aar (for aminoglycoside acetyltransferase regulator), controls AAC(2')-Ia expression in P. stuartii.

Early surgery for ruptured cerebral aneurysm

Preliminary experience with 150 consecutive cases of ruptured cerebral aneurysms operated on within 48 hours is reported. The rationale of this emergency procedure is to prevent early rerupture and also to prevent neurological ischaemic consequences of the subarachnoid haemorrhage likely to develop in the first week after a rupture. The acceptable outcome of the surgically treated cases (87% excellent and good outcome) has been favourably matched to those of a group of equal number of consecutive cases seen in suitable condition for surgery within 48 hours by medical personnel but that remained unoperated for various reasons. The incidence of delayed neurological ischaemia as the definite cause of death is lower in the group operated on in the acute stage than those with delayed surgery, although the overall incidence of clinical vasospasm does not seem significantly lower than in the delayed surgery group.

The Hungarian country profile: inequalities in health and health care in Hungary

Analysis of occupational, educational, urban/rural and regional data over several decades demonstrate large disparities in the availability of health care and in infant and adult mortality. Life expectancy increased in the immediate post-war period but in the late sixties improvement ceased and life expectancy at age 40 began to fall. Mortality has been particularly high for middle-aged males. Analysis by cause of death suggests the persistence of older poverty-type diseases co-existing with the newer lifestyle diseases. Reasons for system dysfunctioning are discussed--lack of health resources, rigid institutional structures, lack of integrated health policies, failure to adjust the distribution of resources to changing needs etc. The analysis raises the question of how to achieve a balance between equity and efficiency.

[Management of malignant pleural effusion by tetracycline pleurodesis]

Eleven patients were treated with chest tube drainage and intrapleural instillation of tetracycline for malignant pleural effusion. In ten cases this procedure for 6-10 days achieved complete resolution of pleural fluid and produced pleurodesis. Only one patient needed longer treatment, but it was also successful. Fluid recurrence was not recognised during the follow-up period. This method is very effective and simple, so the authors recommend the tetracycline pleurodesis for the palliative management of malignant pleural effusions.

The surgery of middle cerebral artery aneurysms

Aneurysms of the middle cerebral bifurcation represent an interesting entity among intracranial saccular aneurysms. Their shape, size, situation, and in particular their relation to the middle cerebral trunk and its branches show wide variations. Topographical analysis of the angiograms offers a great deal of interest in planning surgery. Our experience with 289 patients with middle cerebral artery aneurysms operated on since 1977 are presented. Factors such as number of previous haemorrhages, timing of surgery, preoperative condition, major intraoperative bleeding or brain oedema and delayed postoperative deterioration play a major role in the outcome. Others such as severity of the subarachnoid bleed, age, size of the sac seem to have much less influence.

Surgical treatment of multiple intracranial aneurysms

Patients with multiple intracranial aneurysms present a great challenge to neurosurgical practice. The presence of one or more additional aneurysms, whether recognized or unrecognized, along with the source of the haemorrhage profoundly changes the outcome. It also alters the timing and strategy of surgery. In this study the experiences gained from 138 cases with a total of 317 aneurysms are discussed. The analysis of the clinical data, our results and the factors influencing the outcome suggest that the risk of clipping all aneurysms simultaneously are less than the risk of a rebleed from an untreated, previously silent sac even in the early postoperative period.

Factors influencing the outcome of coma in severely injured patients

From this analysis we may conclude that the most important factors influencing the outcome of coma due to injury are age, vegetative state, level of coma, decerebration, and hypocapnia. In all cases where a combination of four or more of any of the above-mentioned factors was present the patient died. EEG seems less predictive in the early period, but may give some information for late prognosis.