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1.
A strain of Methylomonas albus BG8WM, a type 1 obligate methanotroph, which had been maintained for 2 ycars by serial passage on solid medium containing methanol as a carbon source was found to mutate at a frequency of 10-5-10-6 to resistance to dichloromethane (DCMR), the parental strain BG8 did not give rise to DCMR colonies. DCMR strains were no longer capable of growth on methane as a carbon cource and exhibited greatly reduced or undetectable methane mono-oxygenase activity. The mutants fell into three groups on the basis of SDS-PAGE analysis of the polypeptide profiles of the particulate fraction of cell extracts. One or more of four polypeptides of Mr 70,000, 50,000, 25,000 and 23,000 were implicated as being components of the methane mono-oxygenase. Spontaneous reversion to growth on methane and sensitivity to dichloromethane occurred at a frequency of about 10-8. The loss of methane mono-oxygenase activity was not associated with loss of the resident 55 kb plasmid.Abbreviations DCMR
dichloromethane-resistant
- SDS-PAGE
sodium dodecyl sulphate polyacrylamide gel electrophoresis
- NMS
nitrate minimal salts medium 相似文献
2.
Schistosoma mansoni polypeptides immunogenic in mice vaccinated with radiation-attenuated cercariae 总被引:2,自引:0,他引:2
We compared the humoral immune response of mice protected against Schistosoma mansoni by vaccination with radiation-attenuated cercariae to that of patently infected mice, and we identified antigens that elicit a greater, or unique, immune response in the vaccinated mice. These comparisons were based upon radioimmunoprecipitations and immunodepletion of [35S]methionine-labeled schistosomular and adult worm polypeptides, followed by one- and two-dimensional polyacrylamide gel analyses. The humoral responses of patently infected mice and of mice vaccinated once were remarkably similar and were directed against schistosome glycoproteins ranging in molecular size from greater than 300 to less than 10 kDa. Exposing mice to a second vaccination resulted in a marked change in the immune response, to one predominantly directed toward high molecular size glycoproteins. Sequential immunodepletion techniques identified five schistosomular and seven adult worm antigens that showed a greater or unique immunogenicity in vaccinated mice as compared with patently infected mice. These adult worm antigens were purified by preparative sequential immunoaffinity chromatography and used to prepare a polyclonal antiserum, anti-irradiated vaccine. This antiserum bound to the surface of live newly transformed and lung-stage schistosomula, as assessed by immunofluorescence assays, and was reactive with a number of 125I-labeled schistosomular surface polypeptides, including a doublet of 150 kDa that was also recognized by sera of vaccinated mice but not by sera of patently infected mice. 相似文献
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Summary Cucumber seedlings were grown in a Portsmouth soil-sand system to study how varying soil clay and organic matter content might
modify cucumber seedling response to ferulic acid, a reported allelopathic agent. Leaf area expansion of cucumber seedlings,
soil respiration, and soil solution concentrations of ferulic acid were monitored. Leaf area, mean absolute rates of leaf
expansion, and shoot dry weight of cucumber seedlings were significantly reduced by ferulic acid concentrations ranging from
10 to 70 μg/g dry soil. Ferulic acid was applied every other day, since it rapidly disappeared from soil solution as a result
of retention by soil particles, utilization by microbes and/or uptake by roots. The amount of ferulic acid retained (i.e., adsorbed, polymerized,etc.) by soil particles appeared to be secondary to microbial utilization and/or uptake by roots. Varying clay (5.3 to 9.8 g/cup)
and organic matter (2.0 to 0.04g/cup) contents of the soil appeared to have little impact on the disappearance of ferulic
acid from soil solution under “ideal” growth conditions for cucumber seedlings unless larger amounts of ferulic acid were
added to the soil; in this case 200 μg/g. The addition of ferulic acid to the soil materials substantially increased the activity
of the soil microbes. This latter conclusion is based on recovery of ferulic acid from soil solution and soil respiration
measurements.
Paper No. 10347 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, N C 27695-7601. The use
of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the product
named, nor criticism of similar ones not mentioned. 相似文献
6.
The production of carbohydrates by cell suspension cultures of Phleum pratense (timothy grass) is described. Extracellular polysaccharides similar in monosaccharide composition to native cell wall polymers were accumulated, together with polymers of fructose (fructans). The fructans had similar properties to the intracellular reserve polymers found in intact plants, and were found in both cells and media of young, slow-growing cultures.Production of extracellular polysaccharides differed in cultures grown on sucrose or equimolar glucose/fructose as carbon source. These differences were observed only when autoclaved media were used, and were not related to changes in either pH or osmolarity. Autoclaving medium containing radioactive glucose and fructose produced a novel, unidentified labelled compound which was absent in medium containing labelled sucrose. 相似文献
7.
In classical t(9;22) translocation, as observed in chronic granulocytic leukemia (CGL), a hybrid DNA unit is produced, including a rearranged PHL gene, previously known as bcr (breakpoint cluster region) plus the translocated c-abl gene from chromosome 9: a hybrid bcr-abl protein, p210 is formed, with increased tyrosine kinase activity. Such DNA rearrangement, with a p210 protein synthesis, is also found in cases of Philadelphia-positive acute lymphoblastic leukemia (ALL), but in apparently similar cases the bcr gene is not rearranged, and a novel p190 abl-related protein can be found; c-abl rearrangement has also been observed.It is thus established that correlations between cytogenetic and molecular events can be found in CGL and ALL, as in other haemopoietic malignancies: translocation and possible rearrangement of the c-abl oncogene seem of particular importance in this case. 相似文献
8.
Toluene was oxidized by a mutant strain of Pseudomonas putida (strain NG1) to toluene Cis-Glycol (TCG). Product was accumulated in fed-batch cultures to concentrations (18-24 g/L) higher than hitherto achieved. In vitro activities of toluene dioxygenase from P. Putida NG1 were fivefold lower than that from the toluene-grown wild-type organism, whereas comparable activities of both catechol 2,3- and catechol 1,2-oxygenase were obtained; irreversible inhibition of toluene dioxygenase activity by TCG was shown in vitro. Ammonia deprivation during the production phase limited the growth of revertant organisms but had little effect on either the duration (25h) of the process or the final concentration of TCG achieved. The rate of glucose utilization decreased throughout the biotransformation and cell death accompanied the cessation of TCG accumulation in cultures. These changes were a consequence of TCG formation and a cooperative toxic effect was demonstrated for toluene and TCG. Adenylate energy charge values decreased from ca. 0.8 to 0.2 over the course of the biotransformation but were maintained above 0.5 in the absence of TCG. Similarly, cellular AMP levels increased dramatically during biotransformation, presumably as a consequence of RNA degradation, but were maintained at low levels in the absence of TCG. The results suggest that TCG is the mediate of a gradual deterioration in the state of the culture which leads to a loss of both in vivo and in vitro toluence dioxygenase activity and a marked decrease in culture viability. 相似文献
9.
Andrew C. Stainthorpe J. Colin Murrell George P. C. Salmond Howard Dalton Veronica Lees 《Archives of microbiology》1989,152(2):154-159
Methane monooxygenase (MMO) is the enzyme responsible for the conversion of methane to methanol in methanotrophic bacteria. In addition, this enzyme complex oxidizes a wide range of aliphatic and aromatic compounds in a number of potentially useful biotransformations. In this study, we have used biochemical data obtained from purification and characterization of the soluble MMO from Methylococcus capsulatus (Bath), to identify structural genes encoding this enzyme by oligonucleotide probing. The genes encoding the and subunits of MMO were found to be chromosomally located and were linked in this organism. We report here on the analysis of a recombinant plasmid containing 12 kilobases of Methylococcus DNA and provide the first evidence for the localization and linkage of genes encoding the methane monooxygenase enzyme complex. DNA sequence analysis suggests that the primary structures of the and subunit of MMO are completely novel and the complete sequence of these genes is presented. 相似文献
10.
The membrane-bound (particulate) form of methane monooxygenase from Methylococcus capsulatus (Bath) has been solubilised using the non-ionic detergent dodecyl-beta-D-maltoside. A wide variety of detergents were tested and found to solubilise membrane proteins but did not yield methane monooxygenase in a form that could be subsequently activated. After solubilisation with dodecyl-beta-D-maltoside, enzyme activity was recovered using either egg or soya-bean lipids. Attempts to further purify the solubilized methane monooxygenaser protein into its component polypeptides were unsuccessful and resulted in complete loss of enzyme activity. The major polypeptides present in the solubilised enzyme had molecular masses of 49 kDa, 23 kDa and 22 kDa which were similar to those seen in crude extracts [Prior, S. D. & Dalton H. (1985) J. Gen. Microbiol. 131, 155-163]. Studies on substrate and inhibitor specificities indicated that the membrane-associated and solubilised forms of methane monooxygenase were quite similar to each other but differed substantially from the well-characterised soluble methane monooxygenase found in cells grown in a low copper regime and synthesised independently of the particulate methane monooxygenase. 相似文献