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[en] The radiation resistance of 30 strains classified as Candida parapsilosis was examined. The strains originated partly from environments where ionizing radiation was used for research or routine purposes, partly from environments with no known possibility for selection of strains with unusually high radiation resistance. D-6 values between 1.5 and 2.4 Megarads were found when the cells were irradiated in the dried state, a D-6 value being the dose necessary to reduce the initial number of colony-forming units with a factor of 106. The majority of D-6 values were between 1.9 and 2.1 Megarads. D-6 values for the cells irradiated in liquid media were about 2/3 of tose in the dried state. No difference in resistance was revealed depending on the origin of the strains examined. For radiation sterilization of medical products the demonstrated resistance of Candida parapsilosis might be of importance of routine use of minimum doses below 2.5 Megarads were to be accepted. (author)
[en] Resistance to azole antifungal drugs in clinical isolates of the human fungal pathogen Candida albicans is often caused by constitutive overexpression of the CDR1 gene, which encodes a multidrug efflux pump of the ABC transporter superfamily. To understand the relevance of a recently identified negative regulatory element (NRE) in the CDR1 promoter for the control of CDR1 expression in the clinical scenario, we investigated the effect of mutation or deletion of the NRE on CDR1 expression in two matched pairs of azole-sensitive and resistant clinical isolates of C. albicans. Expression of GFP or lacZ reporter genes from the wild type CDR1 promoter was much higher in the azole-resistant C. albicans isolates than in the azole-susceptible isolates, reflecting the known differences in CDR1 expression in these strains. Deletion or mutation of the NRE resulted in enhanced reporter gene expression in azole-sensitive strains, but did not further increase the already high CDR1 promoter activity in the azole-resistant strains. In agreement with these findings, electrophoretic mobility shift assays showed a reduced binding to the NRE of nuclear extracts from the resistant C. albicans isolates as compared with extracts from the sensitive isolates. These results demonstrate that the NRE is involved in maintaining CDR1 expression at basal levels and that this repression is overcome in azole-resistant clinical C. albicans isolates, resulting in constitutive CDR1 overexpression and concomitant drug resistance
[en] This study assessed and monitored 40 consecutive reproduction tests - multigenerational (MG) - of continuous exposure to Cd (at 2 reproduction Effect Concentrations (EC): EC10 and EC50) using the standard soil invertebrate Folsomia candida, in total 3.5 years of data were collected. Endpoints included survival, reproduction, size and metallothionein (MTc) gene expression. Further, to investigate adaptation to the toxicant, additional standard toxicity experiments were performed with the MG organisms of F6, F10, F26, F34 and F40 generations of exposure. Exposure to Cd EC10 caused population extinction after one year, whereas populations survived exposure to Cd EC50. Cd induced the up-regulation of the MTc gene, this being higher for the higher Cd concentration, which may have promoted the increased tolerance at the EC50. Moreover, EC10 induced a shift towards organisms of smaller size (positive skew), whereas EC50 induced a shift towards larger size (negative skew). Size distribution shifts could be an effect predictor. Sensitivity increased up to F10, but this was reverted to values similar to F0 in the next generations. The maximum Cd tolerance limits of F. candida increased for Cd EC50 MG. The consequences for risk assessment are discussed. - Highlights: • F. candida was exposed to Cd in 40 consecutive reproduction tests (3.5 years multigenerational-MG). • EC10 (32 mg Cd/kg) caused population extinction after one year, while EC50 (60 mg Cd/kg) survived. • Size distribution shifts could explain extinction (EC10: positive skew, EC50: negative skew). • Higher metallothionein levels for EC50 exposed could be a survival strategy. • Maximum Cd tolerance limits of F. candida increased for Cd EC50 MG. - Low impact stress can cause population extinction.
[en] A total of 117 acid producing baceria were isolated from grass and silage samples. Almost all isolates, 115 isolates posses homfermentative fermentation. All isolates produced lactic acid in a range of 0.36-2.05%. From their growth and their ability in producing lactic acid, two isolates, a coccus (T3-2-02) and a rod (T3-0-01) were selected for a mixed wild type strains for silage inoculant. After irradiation the wild type strains with gama ray, 51 and 58 isolates of high acid producer were selected from T3-2-02 and T3-0-01 strains, respectively. After testing the growht characteristics and the acid productivity, a coccus strain, MC08 and a rod stain, MR4 were choosen as a mixed irradiated starter culture strains for grass silage fermentation using a 50 dats old Pangola grass (Digitaria eriantha). The experiment was divided into 6 treatments. Treatmet I was the control. Treatmment 2, 4% molasses was added ro the grass. Treatment 3, a mixed wild type strains (T3-2-02+ T3-0-01) was inoculated into the grass. Treatment 4, a mixed irradiated strains (MC08+ MR04) was used. Treatment 5, A mixed wild tpye strains was used and supplemented with 4% molasses. Treatnebt 6, A mixed irradiated strain was assed and supplemented with 4% molasses. The results showed that a qualified silage can be obtained within a week from either the treatment inoculated with starter culture together with4% molasses (T5 and T6) or the treatment supplemented with 4% molasses alone (T2). further more, Silage of the treatments that using starter culture supplemented with 4% molasses gave volatile acid in a requred quantity. Silage of the treatments that inoculated either with a wild type pr a mixed irradiated starter culture posses bether quality than the control treatment. Further more silage that used irradiated starter culture showed a faster ffermentation and higher lactic acid production tha silage that uses wild type starter culture.
[en] The microflora of samples of cotton produced for medical uses, collected from three different districts of great Cairo were examined for occurance of radiation-resistant bacteria. The maximum value of the initial bacterial load was found to be 145x103 bacterial cells/gm. The identified strains were found to be the gram positive rod spore-forming bacilus firmus, B megaterium and B cereus. Different grampositive cocci were found to be allocated to each of the studied districts i.e., micrococcus luteus to Heliopolice, sarcina to Dokki and staphylococcus epidermidis to Imbaba dose response curves for the most commonly found strains in dry state ensure that a dose of 22.5 KGY is quite sufficient to inactivate the most radioresistant isolated strains by more than 9 orderds. This result was confirmed by the sterility control test using thioglycolate and sabouraud media. (author)
[en] Studies conducted in the early 1990s showed for the first time that Saccharomyces cerevisiae can undergo cell death with hallmarks of animal apoptosis. These findings came as a surprise, since suicide machinery was unexpected in unicellular organisms. Today, apoptosis in yeast is well-documented. Apoptotic death of yeast cells has been described under various conditions and S. cerevisiae homologs of human apoptotic genes have been identified and characterized. These studies also revealed fundamental differences between yeast and animal apoptosis; in S. cerevisiae apoptosis is mainly associated with aging and stress adaptation, unlike animal apoptosis, which is essential for proper development. Further, many apoptosis regulatory genes are either missing, or highly divergent in S. cerevisiae. Therefore, in this review we will use the term apoptosis-like programed cell death (PCD) instead of apoptosis. Despite these significant differences, S. cerevisiae has been instrumental in promoting the study of heterologous apoptotic proteins, particularly from human. Work in fungi other than S. cerevisiae revealed differences in the manifestation of PCD in single cell (yeasts) and multicellular (filamentous) species. Such differences may reflect the higher complexity level of filamentous species, and hence the involvement of PCD in a wider range of processes and life styles. It is also expected that differences might be found in the apoptosis apparatus of yeast and filamentous species. In this review we focus on aspects of PCD that are unique or can be better studied in filamentous species. We will highlight the similarities and differences of the PCD machinery between yeast and filamentous species and show the value of using S. cerevisiae along with filamentous species to study apoptosis.
[en] A search technique locating network modules, i.e. internally densely connected groups of nodes in directed networks is introduced by extending the clique percolation method originally proposed for undirected networks. After giving a suitable definition for directed modules we investigate their percolation transition in the Erdos-Renyi graph both analytically and numerically. We also analyse four real-world directed networks, including Google's own web-pages, an email network, a word association graph and the transcriptional regulatory network of the yeast Saccharomyces cerevisiae. The obtained directed modules are validated by additional information available for the nodes. We find that directed modules of real-world graphs inherently overlap and the investigated networks can be classified into two major groups in terms of the overlaps between the modules. Accordingly, in the word-association network and Google's web-pages, overlaps are likely to contain in-hubs, whereas the modules in the email and transcriptional regulatory network tend to overlap via out-hubs
[en] Nomenclature for various radiosensitive mutants of Saccharomyces cerevisiae is briefly discussed. Tables are presented to show results of allelism tests of most of the radiosensitive mutants isolated by various investigators together with a standardized rad locus designation and map positions of a number of rad loci in yeast
[en] Using the cloned RAD54 gene and a plasmid, the authors have fused the coding region of RAD54 to the GAL1 promoter. The resulting plasmid, pTM-X6, contains the GAL1 transcription start ligated to a site just downstream from the transcription starts of RAD54, as confirmed by SI and sequence data. They have found that rad54-3 strains transformed with pTM-6 become resistant to x rays when grown on galactose or glucose/galactose media but remain x-ray sensitive when grown on a glucose medium