Carbon and Nitrogen Mineralization of Lead Treated Soils in the Eastern Mediterranean Region,Turkey

The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg^?1 by treatment with Pb(NO ₃ ) ₂ , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO ₂ respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg^?1 treatments in the aspect of the C(CO ₂ ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg^?1 treatments was not significant. NH ₄ -N and NO ₃ -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg^?1 provided a toxic effect threshold for the microbial activity into 30 days.     

Incidence of mycoflora and mycotoxins in some edible fruits and seeds of forest origin

Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B₁ was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus.     

Microdissection and sequence analysis of pericentric heterochromatin from the Drosophila melanogastermutant Suppressor of Underreplication

In the Suppressor of Underreplication( SuUR) mutant strain of Drosophila melanogaster, the heterochromatin of polytene chromosomes is not underreplicated and, as a consequence, a number of beta-heterochromatic regions acquire a banded structure. The chromocenter does not form in these polytene chromosomes, and heterochromatic regions, normally part of the chromocenter, become accessible to cytological analysis. We generated four genomic DNA libraries from specific heterochromatic regions by microdissection of polytene chromosomes. In situ hybridization of individual libraries onto SuUR polytene chromosomes shows that repetitive DNA sequences spread into the neighboring euchromatic regions. This observation allows the localization of eu-heterochromatin transition zones on polytene chromosomes. We find that genomic scaffolds from the eu-heterochromatin transition zones are enriched in repetitive DNA sequences homologous to those flanking the suppressor of forked gene [ su(f) repeat]. We isolated and sequenced about 300 clones from the heterochromatic DNA libraries obtained. Most of the clones contain repetitive DNA sequences; however, some of the clones have unique DNA sequences shared with parts of unmapped genomic scaffolds. Hybridization of these clones onto SuUR polytene chromosomes allowed us to assign the cytological localizations of the corresponding genomic scaffolds within heterochromatin. Our results demonstrate that the SuUR mutant renders possible the mapping of heterochromatic scaffolds on polytene chromosomes.