Cloning and characterization of a new polyketide synthase gene cluster in Streptomyces aureofaciens CCM 3239.

We cloned a new polyketide gene cluster, aur2, in Streptomyces aureofaciens CCM3239. Sequence analysis of the 9531-bp DNA fragment revealed 10 open reading frames, majority of which showed high similarity to the previously characterized type II polyketide synthase (PKS) genes. An unusual feature of the aur2 cluster is a disconnected organization of minimal PKS genes; ACP is located apart from the genes for ketosynthases KSalpha and KSbeta. The aur2 gene cluster was disrupted in S. aureofaciens CCM3239 by a homologous recombination, replacing the four genes (aur2A, E, F, G) including ketosynthase KSalpha, with antibiotic resistance marker gene. The disruption did not affect growth and differentiation, and disrupted strain produced spores with wild-type grey-pink pigmentation. The biochromatographic analysis of the culture extracts from S. aureofaciens wild type and aur2-disrupted strains did not reveal any difference in the pattern of antibacterial compounds.     

Corticotropin-Releasing Hormone Affects Short Immobilization Stress-Induced Changes in Lung Cytosolic and Membrane Glucocorticoid Binding Sites

Glucocorticoids act via glucocorticoid receptors (GR), typically localized in the cytosol (cGR). Rapid action is probably mediated via membrane receptors (mGR). In corticotropin-releasing hormone knockouts (CRH-KO), basal plasma glucocorticoid levels do differ from wild type levels (WT), but are approximately ten times lower during exposure to immobilization stress (IMMO) in comparison to WT. We tested the following hypotheses: (1) the mice lung tissue GR basal numbers would not be changed in CRH-KO (because of similar glucocorticoid levels), (2) the number of GR would be changed in WT but not in KO during short (30, 90, and 120 min) IMMO (because of higher increase of glucocorticoid levels in WT). The basal levels of cGR were not changed in CRH-KO (compared to WT), while mGR were significantly lower (62 %) in CRH-KO. In WT, there was the only decrease (to 32 %) in cGR after 120 min when we also found an increase in mGR in WT (to 201 %). In CRH-KO, IMMO caused gradual decrease in cGR (to 52 % after 30 min, to 46 % after 90 min, and to 32 % after 120 min). In CRH-KO, the only increase in mGR appeared already at 30 min of IMMO. These data suggest, on the contrary to our hypotheses, that CRH-KO are more susceptible to GR changes in early phases of stress.     

How Much Is Our Fairness Worth? The Effect of Raising Stakes on Offers by Proposers and Minimum Acceptable Offers in Dictator and Ultimatum Games

Background

The aim of this study was to determine whether people respond differently to low and high stakes in Dictator and Ultimatum Games. We assumed that if we raised the stakes high enough, we would observe more self-orientated behavior because fairness would become too costly, in spite of a possible risk of a higher punishment.

Methods

A questionnaire was completed by a sample of 524 university students of biology. A mixed linear model was used to test the relation between the amount at stake (CZK 20, 200, 2,000, 20,000 and 200,000, i.e., approximately $1–$10,000) and the shares, as well as the subjects’ gender and the design of the study (single vs. multiple games for different amounts).

Results

We have discovered a significant relationship between the amount at stake and the minimum acceptable offer in the Ultimatum Game and the proposed shares in both Ultimatum and Dictator Games (p = 0.001, p<0.001, p = 0.0034). The difference between playing a single game or more games with several amounts at stake did not influence the relation between the stakes and the offered and minimum acceptable shares. Women proved significantly more generous than men in their offers in the Dictator Game (p = 0.007).

Conclusion

Our results suggest that people’s behavior in the Dictator and Ultimatum Games depends on the amount at stake. The players tended to lower their relative proposed shares, as well as their relative minimum acceptable offers. We propose that the Responders’ sense of equity and fair play depends on the stakes because of the costs of maintaining fairness. However, our results also suggest that the price of fairness is very high and that it is very difficult, probably even impossible, to buy the transition of Homo sociologicus into Homo economicus.     

Mossbauer spectroscopic study of functional thermal destruction of iron--sulfur proteins in membranes of thermophilic cyanobacteria synechococcus elongatus

A mathematical model of the Mossbauer spectrum (80K) of native membranes of Synechococcus elongatus was constructed on the basis of values of the quadruple splitting (Delta) and the isomeric shift (delta) of the iron-containing components of the photosynthetic apparatus obtained from the literature. Thermally induced changes in the intensity of the spectral components of membranes and isolated preparations of photosystem (PS) I were studied using this model. It was shown that exposure of membranes to 70-80 degrees C causes a decrease in the intensity of the components related to the FX, FA, and FB centers and surface-located ferredoxins of PS I, an increase in the intensity of the doublets of oxidized iron clusters that are nonspecifically absorbed by the membranes, and formation of a new doublet. Spectral parameters of this doublet (Delta = 3.10 mm/sec and delta = 1.40 mm/sec) are typical of inorganic hydrated forms of reduced iron. Heating of PS I preparations also causes a decrease in the intensity of doublets of the FX, FA, and FB centers and an increase in the intensity of doublets of nonspecifically bound oxidized iron. However, this does not cause formation of inorganic reduced iron. Comparison between the intensities of the Mossbauer spectral components in intact and heated samples suggests that the main source of reduced iron in membranes is surface-located ferredoxins. Nonspecifically bound oxidized iron is formed at the expense of the FX, FA, and FB centers. Disappearance of spectral components associated with ferredoxins and accumulation of reduced iron in membranes occur within the temperature range critical for inhibition of electron transport through PS I to oxygen. These findings suggest that the thermally induced processes of accumulation of reduced iron and inhibition of electron transport in PS I in membranes of thermophilic cyanobacteria are interrelated and caused mainly by degradation of the Fe--S centers of ferredoxins. The possible role of reduced iron accumulation in the degradation of the photosynthetic apparatus induced by heat and other extreme physical and chemical factors is discussed.     

Accumulation of the proteolytic marker peptide ubiquitin in the trophoblast of mammalian blastocysts

Ubiquitination is a universal protein degradation pathway in which the molecules of 8.5-kDa proteolytic peptide ubiquitin are covalently attached to the epsilon-amino group of the substrate's lysine residues. Little is known about the importance of this highly conserved mechanism for protein recycling in mammalian gametogenesis and fertilization. The data obtained by the students and faculty of the international training course Window to the Zygote 2000 demonstrate the accumulation of ubiquitin-cross-reactive structures in the trophoblast, but not in the inner cell mass of the expanding bovine and mouse blastocysts. This observation suggests that a major burst of ubiquitin-dependent proteolysis occurs in the trophoblast of mammalian peri-implantation embryos. This event may be important for the success of blastocyst hatching, differentiation of embryonic stem cells into soma and germ line, and/or implantation in both naturally conceived and reconstructed mammalian embryos.     

In vitro genotoxicity of PAH mixtures and organic extract from urban air particles part I: acellular assay

Acellular assay of calf thymus DNA ± rat liver microsomal S9 fraction coupled with ³²P-postlabelling was used to study the genotoxic potential of organic compounds bound onto PM10 particles collected in three European cities—Prague (CZ), Kosice (SK) and Sofia (BG) during summer and winter periods. B[a]P alone induced DNA adduct levels ranging from 4.8 to 768 adducts/10⁸ nucleotides in the concentration dependent manner. However, a mixture of 8 c-PAHs with equimolar doses of B[a]P induced 3.7–757 adducts/10⁸ nucleotides, thus suggesting the inhibition of DNA adduct forming activity by interaction among various PAHs. Comparison of DNA adduct levels induced by various EOMs indicates higher variability among seasons than among localities. DNA adduct levels for Prague collection site varied from 19 to 166 adducts/10⁸ nucleotides, for Kosice from 22 to 85 and for Sofia from 6 to 144 adducts/10⁸ nucleotides. Bioactivation with S9 microsomal fraction caused 2- to 7-fold increase in DNA adduct levels compared to −S9 samples, suggesting a crucial role of indirectly acting genotoxic EOM components, such as PAHs. We have demonstrated for the first time a significant positive correlation between B[a]P content in EOMs and total DNA adduct levels detected in the EOM treated samples (R = 0.83; p = 0.04). These results suggest that B[a]P content in EOM is an important factor for the total genotoxic potential of EOM and/or B[a]P is a good indicator of the presence of other genotoxic compounds causing DNA adducts. Even stronger correlation between the content of genotoxic compounds in EOMs and total DNA adduct levels detected (R = 0.94; p = 0.005) was found when eight c-PAHs were taken into the consideration. Our findings support a hypothesis that a relatively limited number of EOM components is responsible for a major part of its genotoxicity detectable as DNA adducts by ³²P-postlabelling.