Monitoring the natural attenuation of a sewage sludge toxicity using the Allium cepa test

Appropriate final disposal of sewage sludge (SS) generated by wastewater treatment plants (WWTP) has been considered a serious environmental problem, but also a viable alternative to be applied in agriculture, once SS is rich in organic matter and nutrients. However, SS can be a source of contamination of several toxic agents. Therefore, its use in agriculture requires special care to avoid possible damage to the environment and exposed organisms. Detoxification of toxic wastes can be performed using the monitored natural attenuation, which involves biological, physical and chemical processes that frequently occur in the environment. This study aimed to assess the feasibility of decontaminating SS after different periods of monitored natural attenuation. To this end, samples of SS and associations of soil/SS with proportions of 10, 25 and 50% SS were buried for 0, 2, 6 and 12 months in holes prepared in a place free of contamination. Allium cepa was used as an indicator to assess the efficiency of the natural attenuation process. According to chemical analysis, the SS samples presented a high concentration of m- and p-cresol, especially for samples analyzed after 0 or 2 months of natural attenuation. The microorganisms present in the SS belonged to 17 different genera of bacteria, which varied in the microbial composition among samples. Both, raw SS and aqueous SS extracts induced DNA damage in A. cepa, even when associated with soil. However, this effect was observed to decline during the attenuation period, although significant effects were detected for the highest tested concentration (100% SS) even at the end of this process. These results thus indicated the necessity of applying a stabilization process associating SS and soil for a period of at least 12 months and showed that the studied raw SS is not a viable material for use as a soil reconditioner, even after natural attenuation. A. cepa test proved to be a useful tool to assess the efficiency of SS detoxification process. Therefore, we suggest that the application of SS in agriculture should be approached with caution and that the SS must be previously submitted to methodologies that evaluate its toxic potential.     

Screening costramid libraries for chromosomal genes: an alternative interspecific hybridization method

Abstract Broad host-range RK2-based cosmid vectors ('costramids') are increasingly used in molecular genetic studies of Gram-negative soil bacteria such as Rhizobium spp. we describe a simple modification of existing methods, whereby a genomic library constructed in a stringently replicated vector can be screened for genes which are undetectable by colony hybridization due to background cross-hybridization. This method allows the use of 'heterologous' probes (interspecies hybridization) to isolate several presumptive genes of interest from a gene bank of Rhizobium sp. NGR234 made in the costramid pRK7813. These are a gene with homology to the citrate synthase gene ( gltA ) or Escherichia coli , the gene encoding δ-aminol evulinic acid synthase ( hemA ), and a gene or genes regulating dicarboxylate transport.     

A translocation associated, loss-of-function mutation in the nitrogen metabolite repression regulatory gene of Aspergillus nidulans can revert intracistronically

Summary The areA ^r -18 mutation is a loss-of-function mutation in areA, the positive acting regulatory gene mediating nitrogen metabolite repression in Aspergillus nidulans. It results from a reciprocal translocation which splits the coding region into 5 and 3 moieties. Surprisingly, we have selected rare intracistronic revertants of areA ^r -18. From crosses heterozygous for areA ^r -18 revertant alleles, duplication-deficiency progeny containing two copies of a substantial portion of chromosome IV but lacking part of chromosome III, including the 5 moiety of areA, have been obtained. For all four revertants analysed genetically, growth properties of these duplication-deficiency strains indicate that the reversion events involve the 3 portion of areA and that the 5 portion of areA is unnecessary for the revertant phenotype. This conclusion was directly confirmed for one revertant using Southern blotting. As all four reversion events involve additional chromosomal rearrangements, they probably fuse functional promoters, ribosome binding sites and in frame initiation codons to the 3 portion of the gene. In the course of characterisation of these mutations, new mapping data for a large region of chromosome IV have been generated, and a new reciprocal translocation activating the cryptic regulatory gene areB, whose product can substitute for that of areA, has been identified.     

A locus involved in kanamycin, chloramphenicol and L-serine resistance is located in the bglY-galU region of the Escherichia coli K12 chromosome

Summary Spontaneous mutants of Escherichia coli K12 displaying an increased level of the kanamycin resistance conferred by plasmid pGR71 were selected. Several mutants obtained in this way apparently carry large chromosomal deletions extending into galU and/or bglY (27 min). This positive selection of deletions allowed detection of a new locus located between galU and bglY. Deletions of this locus are responsible for increased resistance to kanamycin (Irk), decreased resistance to l-serine in minimal medium (Drs) and decreased resistance to chloramphenicol (Drc) when a cat gene is present in the bacteria.     

Isolation of the RAD18 gene of Saccharomyces cerevisiae and construction of rad18 deletion mutants

Summary The RAD18 gene of Saccharomyces cerevisiae is involved in mutagenic DNA repair. We describe its isolation from a yeast library introduced into the centromeric YCp50 vector, a low copy number plasmid. The insert was sublconed into YCp50 and into the multicopy YRp7 plasmid. RAD18 is not toxic when present in multiple copies but the UV survival response indicates an heterogeneity in the cell population, a fraction of it being more sensitive. A DNA segment, close to RAD18, is toxic on the multicopy plasmid and may correspond to the tRAN sup61 known to be tightly linked to RAD18. Chromosomal deletions of RAD18 were constructed. The gene is not essential and the deleted strains have the properties of single site mutants. Thus, RAD18 appears to be essentially involved in DNA repair metabolism.     

Mutagenicity of ptaquiloside, the carcinogen in bracken, and its related illudane-type sesquiterpenes II. Chromosomal aberration tests with cultured mammalian cells

The chromosomal aberration test using a Chinese hamster lung cell line (CHL) was carried out on ptaquiloside and its related compounds, hypoloside B, hypoloside C, illudin M and illudin S. Ptaquiloside induced chromosomal aberrations at doses as low as 4.5 μg/ml (0.0113 mM). The clastogenic effect was ph-dependent. The same activity was observed at a 90-fold higher dose at pH 5.3 in the culture medium compared with the activity at pH 74. or pH 8.0. Both hypoloside B and hypoloside C were also clastogenic at almost the same dose levels as that of ptaquiloside. Illudin M and illudin S were also potet clastogens and induced aberrations at much lower doses than ptaquiloside. These results suggest that the clastogenic effect is involved in the mechanism of carcinogenic potency of ptaquiloside in animals.     

Isolation and characterization of high-mobility-group proteins from maize

Chromosomal nonhistone high-mobility-group (HMG) proteins were purified from nuclei of maize (Zea mays L. cv. A619) endosperm and leaf tissue. Tissuespecific differences were observed in their polypeptide patterns, in in-vitro phosphorylation experiments with a casein-kinase type II, and by Western blot analysis with antisera against different HMG proteins. Gelfiltration chromatography demonstrated that maize HMG proteins occur as monomers. By measuring the capacity of the HMG proteins to bind to the 5 flanking region of a zein gene, the sensitivity of the proteins to different temperatures, salt concentrations and pH values was determined.Abbreviations EMSA electrophoretic-mobility-shift assay - FPLC fast protein liquid chromatography - HMG high-mobility group - kDa kilodaltons - PVDF polyvinylidenedifluoride - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis We would like to thank Mrs. E. Brutzer for excellent technical assistance. We are indebted to Mrs. M. Strecker and Dr. W. Bessler of the Institut für Immunbiologie, Freiburg, FRG, for the preparation of antisera and we gratefully acknowledge helpful discussions with Drs. T. Quayle, R. Grimm and U. Müller of this institute. This work was supported by grants from the Deutsche Forschungsgemeinschaft and the Fond der Chemischen Industrie.     

蟾蜍红细胞与网织红细胞染色质蛋白的比较研究Ⅲ·HMG蛋白质

从亚洲蟾蜍(Bufo bufo asiaticus)与鸡红细胞核内分离纯化了HMG蛋白(Highmobility group proteins),经聚丙烯酰胺凝胶电泳鉴定,证明两者的电泳图谱不完全相同,在蟾蜍的红细胞内也能观察到与鸡HMG_(17)相对应位置上的蛋白质区带,但在鸡HMG_(14)相对应的位置上,却能观察到两条显著的蛋白质区带(A及B带)。此外,我们已把蟾蜍成熟红细胞与苯肼诱发后的网织红细胞内的HMG蛋白进行比较,证明两者有显著的差异。网织红细胞内HMG_A和HMG_B蛋白在含量上起了变化,却与成熟的红细胞相反。另外还出现了二条新的蛋白区带(C与D带)。初步的结果暗示了,HMG蛋白类似于非组蛋白、染色质蛋白,在量上的变化将会引起功能上的变化。     

Proximal and distal transformation during intercalary regeneration in the planarianDugesia(S)mediterranea

Summary Studies on intercalary regeneration in several organisms have shown that a regenerate is formed when surfaces of different positional value along the proximo-distal axis are opposed. One of the main problems posed by this phenomenon is to know which piece contributes to the building of the regenerate. In the present work we have studied this problem in planarians using chimaeras made between pieces of different body levels, irradiated or not, of the sexual and asexual races ofDugesia(S)mediterranea that differ in a chromosomal marker.The results found show very clearly that intercalary regenerates in planarians are formed by cells coming from both pieces (stumps), and that irradiated pieces keep the positional values and interact with non-irradiated pieces to restore the missing parts. This means that distal and proximal transformation do actually occur at the same time during intercalary regeneration in planarians. The implications of these results as regards to the origin of cells in the regenerate and to present models of intercalary regeneration are discussed.     

Conservatism of sites of tRNA loci among the linkage groups of severalDrosophila species

Summary The sites of seven tRNA genes (Arg-2, Lys-2, Ser-2b, Ser-7, Thr-3, Thr-4, Val-3b) were studied by in situ hybridization.¹²⁵I-labeled tRNA probes fromDrosophila melanogaster were hybridized to spreads of polytene chromosomes prepared from fourDrosophila species representing different evolutionary lineages (D. melanogaster, Drosophila hydei, Drosophila pseudoobscura, andDrosophila virilis). Most tRNA loci occurred on homologous chromosomal elements of all four species. In some cases the number of hybridization sites within an element varied and sites on nonhomologous elements were found. It was observed that both tRNA ₂ ^Arg and tRNA ₂ ^Lys hybridized to the same site on homologous elements in several species. These data suggest a limited amount of exchange among different linkage groups during the evolution ofDrosophila species.