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51.
52.
Explanations for the acclimation period preceding the mineralization of organic chemicals in aquatic environments 总被引:4,自引:0,他引:4
A study was conducted of possible reasons for acclimation of microbial communities to the mineralization of organic compounds in lake water and sewage. The acclimation period for the mineralization of 2 ng of p-nitrophenol (PNP) or 2,4-dichlorophenoxyacetic acid per ml of sewage was eliminated when the sewage was incubated for 9 or 16 days, respectively, with no added substrate. The acclimation period for the mineralization of 2 ng but not 200 ng or 2 micrograms of PNP per ml was eliminated when the compound was added to lake water that had been first incubated in the laboratory. Mineralization of PNP by Flavobacterium sp. was detected within 7 h at concentrations of 20 ng/ml to 2 micrograms/ml but only after 25 h at 2 ng/ml. PNP-utilizing organisms began to multiply logarithmically after 1 day in lake water amended with 2 micrograms of PNP per ml, but substrate disappearance was only detected at 8 days, at which time the numbers were approaching 10(5) cells per ml. The addition of inorganic nutrients reduced the length of the acclimation period from 6 to 3 days in sewage and from 6 days to 1 day in lake water. The prior degradation of natural organic materials in the sewage and lake water had no effect on the acclimation period for the mineralization of PNP, and naturally occurring inhibitors that might delay the mineralization were not present. The length of the acclimation phase for the mineralization of 2 ng of PNP per ml was shortened when the protozoa in sewage were suppressed by eucaryotic inhibitors, but it was unaffected or increased if the inhibitors were added to lake water.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
53.
DNA-dependent RNA polymerase subunits encoded within the vaccinia virus genome. 总被引:12,自引:6,他引:6 下载免费PDF全文
Antiserum to a multisubunit DNA-dependent RNA polymerase from vaccinia virions was prepared to carry out genetic studies. This antiserum selectively inhibited the activity of the viral polymerase but had no effect on calf thymus RNA polymerase II. The specificity of the antiserum was further demonstrated by immunoprecipitation of RNA polymerase subunits from dissociated virus particles. The presence in vaccinia virus-infected cells of mRNA that encodes the polymerase subunits was determined by in vitro translation. Immunoprecipitable polypeptides with Mrs of about 135,000, 128,000, 36,000, 34,000, 31,000, 23,000, 21,000, 20,000, and 17,000 were made when early mRNA was added to reticulocyte extracts. The subunits were encoded within the vaccinia virus genome, as demonstrated by translation of early mRNA that hybridized to vaccinia virus DNA. The locations of the subunit genes were determined initially by hybridization of RNA to a series of overlapping 40-kilobase-pair DNA fragments that were cloned in a cosmid vector. Further mapping was achieved with cloned HindIII restriction fragments. Results of these studies indicated that RNA polymerase subunit genes are transcribed early in infection and are distributed within the highly conserved central portion of the poxvirus genome in HindIII fragments E, J, H, D, and A. 相似文献
54.
Micropuncture, microanalytical and microelectrode techniques were used to study electrochemical aspects of 7 elements and fluid in the ductuli efferents and ductus epididymidis of the tammar. Rete testis fluid was isosmotic with blood and had a lower pH. It also contained lower concentrations of bicarbonate, sodium, calcium, magnesium, phosphorus and sulphur and higher concentrations of potassium and chloride than blood. The luminal fluid was acidified further during passage through the sperm ducts and all of the elements which were studied moved in or out of the lumen, usually against an electrochemical gradient. The ductuli efferents reabsorbed 87% of the fluid leaving the testis without changing the intraluminal concentrations of sodium, potassium and calcium, but the concentrations of magnesium, phosphorus and sulphur increased. The caput epididymidis reabsorbed about half the fluid entering it: sodium concentrations decreased and those of potassium and phosphorus increased. There was also some fluid reabsorption and an increase in the values of potassium and phosphorus in the corpus epididymidis. There was little net transport of fluid in the cauda epididymidis; sodium, chloride, magnesium and phosphorus concentrations decreased and potassium values increased. Studies involving filtration through a dialysis membrane of blood and fluid from the rete testis and cauda epididymidis showed that, whilst some of the calcium, magnesium, phosphorus and sulphur was associated with high molecular weight compounds in blood, the association was not significant in the reproductive fluids. 相似文献
55.
The V79-4 Chinese hamster line was mutagenized and surviving clones screened for X-ray sensitivity using a replica microwell technique. One slightly sensitive clone and 3 clearly sensitive clones were isolated from approximately 5000 screened, and designated irs 1 to irs 4. The 3 more sensitive clones showed different responses to the genotoxic agents mitomycin C (MMC), ethyl methanesulphonate (EMS) and ultraviolet light (UV). irs 1 showed considerable sensitivity to all the agents tested, in the order MMC much greater than EMS greater than UV. irs 2 and irs 3 had similar sensitivities to EMS and to UV (EMS greater than UV) but irs 3 was more sensitive than irs 2 to MMC. None of these mutants is identical in phenotype to previously published mutants. 相似文献
56.
Janet L. Taylor Jonathan D. G. Jones Steve Sandler Gunhild M. Mueller John Bedbrook Pamela Dunsmuir 《Molecular & general genetics : MGG》1987,210(3):572-577
Summary The Serratia marcescens chiA gene encodes a secreted chitinase activity which contributes to the fungal growth inhibition exhibited by this bacterium. The coding region from the chiA gene was fused to the promoter and 3 polyadenylation region of the Agrobacterium nopaline synthase gene. Site-directed mutagenesis of specific nucleotides surrounding the initiating AUG of the coding sequence of this chimeric gene resulted in up to an eight-fold increase in the amount of chitinase protein detected in transformed plant tissue. Analysis of the chiA mRNA indicated that these nucleotides also affected mRNA levels. At least 50% of the chitinase protein produced in transformed tobacco cells was the same molecular weight as the S. marcescen secreted protein. 相似文献
57.
Different subfamilies of alphoid repetitive DNA are present on the human and chimpanzee homologous chromosomes 21 and 22. 总被引:5,自引:1,他引:4 下载免费PDF全文
The alphoid repeat DNA on chimpanzee chromosome 22 was compared with alphoid repeat DNA on its human homologue, chromosome 21. Hybridization of different alphoid probes under various conditions of stringency show that the alphoid repeats of chimpanzee chromosome 22 are not closely related to those of human chromosome 21. Sequence analysis of cloned dimer and tetramer EcoRI fragments from chimpanzee chromosome 22 confirm the low overall level of homology, but reveal the presence of several nucleotide changes which are exclusive to the chromosome 21 subfamily of human alphoid DNA. Southern blot analysis of alphoid repeat DNA on the chimpanzee X chromosome suggests this subfamily has been strongly conserved during and since the separation of chimpanzee and man although the two subfamilies can be distinguished on the basis of Taq I restriction fragments. 相似文献
58.
Streptococcus pyogenes type 12 M protein gene regulation by upstream sequences. 总被引:33,自引:7,他引:26 下载免费PDF全文
J C Robbins J G Spanier S J Jones W J Simpson P P Cleary 《Journal of bacteriology》1987,169(12):5633-5640
59.
Two mutant strains of Escherichia coli K 12 Doc-S resistant to the uncoupling agents 4,5,6,7-tetrachloro-2-trifluoromethyl benzimidazole and carbonyl cyanide m-chlorophenylhydrazone were isolated. These strains, designated TUV and CUV, were capable of (a) growth, (b) the transport of succinate and L-proline and (c) electron-transport-linked oxidative synthesis of ATP in the presence of titres of uncoupler which inhibited these processes in strain Doc-S. The inhibition of transport of L-proline by a fixed titre of uncoupler was sharply pH dependent in strain Doc-S: uptake was unaffected at pH 7.6 but completely inhibited at pH 5.6. This pH dependence was not shown by the resistant strains. We believe that uncouplers were equally accessible to their site(s) of action in the energy-conserving membrane of the sensitive and resistant strains. We conclude that uncoupler resistance in these strains of E. coli has arisen as a consequence of mutations which directly affect a specific site of uncoupler action within the cytoplasmic membrane, rather than as a consequence of a decrease in the permeability of cells to uncoupler. 相似文献
60.
2-Phenylethylamine catabolism by Escherichia coli K12 总被引:1,自引:0,他引:1
Escherichia coli K12 grows on 2-phenylethylamine as sole carbon and energy source by converting it, via phenylacetaldehyde, to phenylacetic acid. Phenylacetaldehyde was formed by the action of an inducible amine oxidase and catalase activity was increased sixfold, presumably to ensure removal of the H2O2 that was expected to be a product of the amine oxidation. The phenylacetaldehyde was oxidized to phenylacetic acid by an inducible NAD+-dependent dehydrogenase. Mutants defective in phenylacetaldehyde dehydrogenase cannot grow on 2-phenylethylamine as carbon and energy source but can still use it as a nitrogen source. 相似文献