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1.
Mutants resistant to phenylalanine analogs (L-tyrosine, p-fluoro-D, L-phenylalanine (PFP) and trans-cinnamic acid) were isolated from a wild type strain of Rhodotorula glutinis A-97 by mutagenic treatment with gamma radiation and screened for phenylalanine ammonia lyase (PAL) production. One such mutant, gammaT11 (resistant to L-tyrosine), exhibited four times the PAL activity of the parent wild strain A-97. Mutant isolate gammaTFP5.6 which was selected as L-tyrosine and PFP resistant isolate, produced inducible PAL activity at levels 5.94-fold higher than the wild-type A-97 and 2.66-fold higher than its parent mutant isolate gammaT5 which was resistant to L-tyrosine. The mutant isolate gammaTC5d which was resistant to L-tyrosine and trans-cinnamic acid, exhibited 3.48 and 1.56-fold increase in PAL activity compared to the parent wild strain A-97 and its parent mutant isolate gammaT5, respectively. Different media have been examined for the induction of PAL. 相似文献
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3.
Gene mutation eliminating antimycin A-tolerant electron transport in Ustilago maydis 总被引:2,自引:1,他引:1
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A class of mutants of Ustilago maydis selected on a fungitoxic oxathiin lack of antimycin A-tolerant respiratory system which is present in wild-type cells. This system provides, directly or indirectly, for considerable resistance to antimycin A because growth of mutant cells lacking the system is much more sensitive to the antibiotic than that of the wild type. Antimycin A-sensitive O(2) uptake and growth is found in half of the progeny from crosses of mutant to wild type. All antimycin A-sensitive segregants are somewhat more resistant to oxathiins than the antimycin A-resistant segregants. The respiration of the mutant is strongly inhibited by cyanide and azide at concentrations which stimulate respiration of the wild type. Respiration of both mutant and wild type is about equally inhibited by rotenone. It appears that the mutation alters some component of the respiratory system located between the rotenone inhibition site and the antimycin A inhibition site that permits shift of electron transport to an alternate terminal oxidase when the normal electron transport pathway is blocked. 相似文献
4.
With the use of 32P-labeled phosphate and 42K2CO3 the effect of diphenyl on permeability and uptake properties of the cytoplasmic membrane in wild type and diphenyl-tolerant mutant conidia of Fusarium solani f. cucurbitae was studied. No general damage to the membrane with unspecific leakage of cell constituents was demonstrated under conditions in which diphenyl prevents germination of wild type conidia. The fresh conidia do not require exogenous supply of energy for the uptake of phosphate or of potassium. In the wild type the entry of 32P is inhibited but that of 42K strikingly stimulated by diphenyl. Independently of the tolerant mutant gene present, the mutant conidia are significantly less sensitive to the phosphate uptake inhibition and not affected at all by diphenyl with respect to the uptake of potassium. The latter difference from the wild type seems to indicate genetic control of some property of the potassium transport system in this fungus. 相似文献
5.
Nitrogen metabolite repression of fluoropyrimidine resistance and pyrimidine uptake in Neurospora crassa 总被引:2,自引:0,他引:2
Summary Wild type Neurospora crassa was shown to be more resistant to 5-fluoro-uracil, 5-fluoro-uridine and 5-fluoro-2-deoxyuridine in the presence of ammonia than in its absence. This differential resistance may in part be accounted for by the observation that both uracil and uridine uptake in germinating conidia is under nitrogen metabolite regulation. The uptake of uracil and uridine is increased on poor nitrogen sources in wild type, is unaffected by nitrogen source in a nit-2 mutant strain while a gln-1 mutant strain showed intermediate behaviour.Wild type also showed increased resistance to all three fluoropyrimidines with increased temperature and both uracil and uridine uptake in the wild type increased with temperature.Supported by S.R.C. grant GR/A/64655F.P. Buxton was supported during the period of this work by an S.R.C. Research Studentship 相似文献
6.
Application of diazotrophic cyanobacteria, Anabaena variabilis, as biofertilizer for rice cultivation has a beneficial effect on crop productivity and maintenance of soil fertility. However,
periodic applications of herbicides used to obtain high crop productivity are not only detrimental to weeds but to biofertilizer
strains of cyanobacteria also. Therefore, research was undertaken to isolate four herbicide resistant strains (Arozin-R, Alachlor-R,
Butachlor-R and 2,4-D-R) and a multiple herbicide resistant strain (MHR) of natural isolates of A. variabilis exhibiting resistance against these common rice field herbicides. The outdoor survivability of mutant strains and the productivity
of rice crop (IR-36) were evaluated by inoculating the wild type and herbicide resistant mutant strains of A. variabilis in the presence and absence of recommended field dosages of test herbicides. No difference in survival and biofertilizer
potentials of the herbicide resistant strains was observed in herbicide treated or in untreated conditions. Highest survivability
(87%) was exhibited by MHR relative to other mutants. Highest growth and grain yield (76%) were recorded in plants treated
with MHR as compared to uninoculated control rice plants. In conclusion, the mutant strains of A. variabilis had stable resistance to herbicides under outdoor conditions in flooded soils. Not only did the herbicide resistance strains
increase growth of rice relative to the uninoculated pots, they were more beneficial for rice growth than the wild type strain.
Responsible Editor: Richard W. Bell. 相似文献
7.
Albesa I Becerra MC Battán PC Páez PL 《Biochemical and biophysical research communications》2004,317(2):605-609
Staphylococcus aureus and Escherichia coli sensitive to chloramphenicol incubated with this antibiotic suffered oxidative stress with increase of anion superoxide (O2-). This reactive species of oxygen was detected by chemiluminescence with lucigenin. S. aureus, E. coli, and Enterococcus faecalis sensitive to ciprofloxacin exhibited oxidative stress when they were incubated with this antibiotic while resistant strains did not show stimuli of O2-. Other bacteria investigated was Pseudomonas aeruginosa, strains sensitive to ceftazidime and piperacillin presented oxidative stress in presence of these antibiotics while resistant strains were not stressed. Higher antibiotic concentration was necessary to augment O2- in P. aeruginosa biofilm than in suspension, moreover old biofilms were resistant to oxidative stress caused by antibiotics. A ceftazidime-sensitive mutant of P. aeruginosa, coming from a resistant strain, exhibited higher production of O2- than wild type in presence of this antibiotic. There was relation between antibiotic susceptibility and production of oxidative stress. 相似文献
8.
Carl H. J. Berry Mohammed A. K. Ibrahim Alan Coddington 《Molecular & general genetics : MGG》1978,167(2):217-225
Summary Mutants of Schizosaccharomyces pombe were isolated as resistant either to trichodermin or to anisomycin. Growth tests showed that the majority of mutants isolated were cross resistant to both drugs and also to cycloheximide. A limited genetic analysis showed that mutants at least four loci, tri3, tri4, ani1 and ani2, had this phenotype as was also the case for mutants at three cycloheximide resistant loci, cyh2, cyh3 and cyh4 reported previously (Ibrahim and Coddington, 1976). Allelism tests showed that the tri3, ani2 and cyh4 strains were allelic. A mutant at another trichodermin resistant locus, tri5, was cross resistant to anisomycin but sensitive to cycloheximide.Ribosomes from wild type and selected strains were analysed in a poly U directed cell free protein synthesising system. Three strains, cyh1-C7, ani1-F1 and tri-N15 (probably a tri5 allele) possessed ribosomes which were more resistant than the wild type to the drugs used in their isolation. In each case the site of the resistance was in the 60S subunit. Ribosomes from the cyh2, cyh3 and cyh4 strains were as sensitive to cycloheximide as those from wild type. 相似文献
9.
Summary The 80S ribosome of Schizosaccharomyces pombe contains 93 proteins as determined by twodimensional electrophoresis on polyacrylamide gels. Of these, 76 are basic and 17 are acidic at pH 8.7. 38 proteins could be assigned unambiguosly to the large sub-unit and 19 to the small.67 proteins were extracted from the two-dimensional gels and their molecular weights determined by electrophoresis on calibrated SDS-gels. Values varied from 11,000 to 52,000 daltons, the number average being 25,000 daltons. Hence the total protein content of the 80S ribosome must be at least 1.67x106 daltons.Three drug resistant strains are known, cyh1, anil and tri5 (resistant to cycloheximide, anisomycin and trichodermin respectively), in which resistace is conferred by an altered ribosome, in each case by an altered 60S sub-unit. When 80S ribosomal protein patterns from these strains were compared with that of wild type, in only one case was a clear difference seen. This involved a large sub-unit, basic protein (designated number 66 on our classification) which, in the cyh1 strain, had a reduced mobility in the second dimension when compared to the wild type. The mutant form of protein 66 had a molecular weight of 25,000 daltons compared to the 22,000 of the wild type protein. Production of a larger protein by the mutant strain could either be due to a readthrough event or to an alteration in the specificity of a modifying or processing enzyme. 相似文献
10.
Biochemical and genetic characterization of dehydrobiotin resistant mutants of Escherichia coli 总被引:2,自引:0,他引:2
C. H. Pai 《Molecular & general genetics : MGG》1974,134(4):345-357
Summary Dehydrobiotin (DHB) resistant mutants were isolated from strains of Escherichia coli K-12 and were classified into two groups; dhbA and dhbB.In dhbB mutants the structural genes for enzymes of the biotin pathway are expressed constitutively at a high rate. The dhbB gene is co-transducible with argE at a frequency of about 50% by P1 transduction and maps on the chromosome between arg EC BH and rif. The dhbB
+ gene is trans-dominant over the mutant allele indicating that the dhbB
+ gene controls the production of a diffusible substance such as a repressor molecule.The dhbA mutants show biotin biosynthetic activity comparable to the wild type and are as sensitive to repression by biotin as the parent strain. The mutants appear to be deficient in DHB transport as suggested by the findings that the ability of the mutants to take up biotin is reduced significantly and that DHB, a competitive inhibitor of biotin uptake, is much less inhibitory to biotin uptake in the mutants than in the wild type. 相似文献
11.
B. L. WILD 《The Annals of applied biology》1983,103(2):237-241
In vitro dosage response data with different isolates of Penicillium digitatum and the fungicide guazatine indicated an approximate 10-fold shift in tolerance when compared with wild type strains. ED50 values for resistant strains were approximately 0.5 μg/ml compared to approximately 0.05, μg/ml for the wild type strains. Colony growth of guazatine resistant isolates on selective media containing carbendazim showed that they were also resistant to the benzimidazole group of fungicides. In vivo tests in inoculated oranges with strains previously characterised by in vitro tests confirmed resistance to guazatine and benomyl. A combined treatment of these fungicides at 400 /μ/ml and 500 μg/ml respectively, which normally gives protection against decay, also failed to provide adequate mould control. Growth and pathogenicity of the resistant strains in these tests in oranges were indistinguishable from that of wild type strains. 相似文献
12.
Kitphati W Ngok-Ngam P Suwanmaneerat S Sukchawalit R Mongkolsuk S 《Applied and environmental microbiology》2007,73(15):4760-4768
In Agrobacterium tumefaciens, the balance between acquiring enough iron and avoiding iron-induced toxicity is regulated in part by Fur (ferric uptake regulator). A fur mutant was constructed to address the physiological role of the regulator. Atypically, the mutant did not show alterations in the levels of siderophore biosynthesis and the expression of iron transport genes. However, the fur mutant was more sensitive than the wild type to an iron chelator, 2,2'-dipyridyl, and was also more resistant to an iron-activated antibiotic, streptonigrin, suggesting that Fur has a role in regulating iron concentrations. A. tumefaciens sitA, the periplasmic binding protein of a putative ABC-type iron and manganese transport system (sitABCD), was strongly repressed by Mn(2+) and, to a lesser extent, by Fe(2+), and this regulation was Fur dependent. Moreover, the fur mutant was more sensitive to manganese than the wild type. This was consistent with the fact that the fur mutant showed constitutive up-expression of the manganese uptake sit operon. Fur(At) showed a regulatory role under iron-limiting conditions. Furthermore, Fur has a role in determining oxidative resistance levels. The fur mutant was hypersensitive to hydrogen peroxide and had reduced catalase activity. The virulence assay showed that the fur mutant had a reduced ability to cause tumors on tobacco leaves compared to wild-type NTL4. 相似文献
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14.
Summary A cyanophage AS-1-resistant mutant strain of Anacystis nidulans exhibited a slow rate of nutrient uptake compared to the wild type. The increased Cu++ sensitivity of the mutant could be correlated with higher rates of Cu++ uptake. The results are discussed in the light of alterations in the proteins involved in permeability of the outer membrane. 相似文献
15.
de Weert S Dekkers LC Bitter W Tuinman S Wijfjes AH van Boxtel R Lugtenberg BJ 《FEMS microbiology ecology》2006,58(2):205-213
Pseudomonas fluorescens strain PCL1210, a competitive tomato root tip colonization mutant of the efficient root colonizing wild type strain WCS365, is impaired in the two-component sensor-response regulator system ColR/ColS. Here we show that a putative methyltransferase/wapQ operon is located downstream of colR/colS and that this operon is regulated by ColR/ColS. Since wapQ encodes a putative lipopolysaccharide (LPS) phosphatase, the possibility was studied that the integrity of the outer membrane of PCL1210 was altered. Indeed, it was shown that mutant PCL1210 is more resistant to various chemically unrelated antibiotics which have to pass the outer membrane for their action. In contrast, the mutant is more sensitive to the LPS-binding antibiotic polymyxin B. Mutant PCL1210 loses growth in competition with its wild type when grown in tomato root exudate. Mutants in the methyltransferase/wapQ operon are also altered in their outer membrane permeability and are defective in competitive tomato root tip colonization. A model for the altered outer membrane of PCL1210 is discussed. 相似文献
16.
Ruth Levitz Ilan Friedberg Ruth Brucker Asora Fux Ezra Yagil 《Molecular & general genetics : MGG》1985,200(1):118-122
Summary The periplasmic phosphate binding protein is a product of the phoS gene and is an essential component of the phosphate specific transport (PST) system, which mediates Pi uptake in Escherichia coli. The binding of Pi to periplasmic protein(s) and the kinetic parameters of Pi uptake were studied in phoT and pstB mutants of E. coli. These mutants are impaired in Pi uptake but have a periplasmic Pi-binding protein whose Pi-binding acpacity was estimated by the retention kinetics. The Pi-binding activity in two pstB mutants was found to be weaker as compared to phoT9 and the wild type. The K
D values for Pi binding to periplasmic protein were determined by equilibrium dialysis. In the pstB mutants the K
D value was found to be 9–31 times higher than the values obtained for the wild type and the phoT mutant. The apparent K
m values for Pi uptake in one pstB mutant is 14.3 times higher than in the wild type. V
max of the mutant is 8.3 times lower that of the wild type. The data indicate that pstB, an essential gene of the PST transport system, is promoting the binding capacity of the Pi-binding protein.Abbreviations AP
alkaline phosphatase
- Pi
inorganic orthophosphate
- Km
kanamycin 相似文献
17.
Three types of glutamine synthetase (GS)-impaired mutants (gln) ofNostoc muscorum were isolated as ethylenediamine (EDA)-resistant phenotypes and characterized with respect to heterocyst development, nitrogen fixation, ammonium metabolism, photosynthetic characteristics, and glutamine synthetase activity. The criterion for categorizing the mutants was the extent of loss of GS activity (both in transferase and biosynthetic assays) compared with wild type; it was 70% in EDA-1, 30% in EDA-2, and more than 90% in EDA-3 strains. The level of nitrogenase activity in mutant strains was proportionate to heterocyst frequency and was found refractory to ammonium and EDA repression. In EDA-resistant strains, development of heterocysts and their spacing pattern remained unaffected and did not respond to treatment of amino acid analogues, drugs, and ammoniacal compounds which otherwise either stimulated or suppressed the number and altered the spacing pattern in wild type. A biphasic pattern of ammonium uptake indicating two transport systems was observed in all the strains except that the Km values for both high- and low-affinity systems were altered in mutant strains. In vivo treatment with MSX or EDA significantly inhibited the GS activity in wild type, whereas mutant strains did not respond to these treatments and were able to liberate NH
4
+
continuously into the medium without MSX treatment. During NH
4
+
uptake, percentage inhibition of O2 evolution and changes in increase of fluorescence intensity were low in EDA strains compared with wild type. Assessment of GS protein with antibodies against GS and quantitative polyacrylamide gel electrophoresis (PAGE) suggested that loss in specific activity of GS per milligram of extractable protein in EDA mutants was owing to low production of GS-specific protein. SDS-PAGE of purified GS enzyme from all the strains revealed only one polypeptide band of molecular weight of about 51.28 kDa. 相似文献
18.
A Le Menn J Silber J M Goux 《Biology of the cell / under the auspices of the European Cell Biology Organization》1983,49(3):213-218
Two inhibitors of nucleotide metabolism, aminopterin and FUdR, were tested on a wild type strain, on two mutant strains: vg and vgnp, and on a vg strain with the wild type genetic background. Without inhibitors, a lengthening of the developing time was observed for the mutant strains compared to the wild type. With aminopterin, larval mortality and lengthening of developing time are significantly higher in the wild type than in the mutant strains. Mutant strains seemed to be resistant to low concentrations of FUdR. The hypothesis of a perturbed pyrimidine metabolism in the mutants seems to be confirmed. 相似文献
19.
Yu. S. Kondratiev G. V. Brukhansky I. V. Andreeva A. G. Skavronskaya 《Molecular & general genetics : MGG》1977,158(2):211-214
Summary The UV-sensitivity of wild type Salmonella strains has been compared to that of wild type E. coli and its UV-sensitive mutants. Many wild type Salmonella strains are 4–5 times more sensitive than wild type E. coli and their inactivation curve is similar to that for E. coli with a mutation in the polA gene. Alkaline sucrose gradient centrifugation has shown a deficiency of these strains in normal excision repair of UV-damaged DNA. This deficiency is not a Salmonella genus feature because one strain as resistant as wild type E. coli was found. This resistant strain showed normal excision repair in alkaline sucrose gradient centrifugation experiments. The possible influence of plasmids and mutations in repair genes on the ability of Salmonella to repair UV-damaged DNA is discussed. 相似文献
20.
Boron enters plant roots as undissociated boric acid (H3BO3). Significant differences in B uptake are frequently observed even when plants are grown under identical conditions. It has
been theorized that these differences reflect species differences in permeability coefficient of H3BO3 across plasma membrane. The permeability coefficient of boric acid however, has not been experimentally determined across
any artificial or plant membrane. In the experiments described here the permeability coefficient of boric acid in liposomes
made of phosphatidylcholine was 4.9 × 10−6 cm sec−1, which is in good agreement with the theoretical value. The permeability coefficient varied from 7 × 10−6 to 9.5 × 10−9 cm sec−1 with changes in sterols (cholesterol), the type of phospholipid head group, the length of the fatty acyl chain, and the pH
of the medium. In this study we also used Arabidopsis thaliana mutants which differ in lipid composition to study the effect of lipid composition on B uptake. The chs1-1 mutant which has lower proportion of sterols shows 30% higher B uptake compared with the wild type, while the act1-1 mutant which has an increased percentage of longer fatty acids, exhibited 35% lower uptake than the wild type. Lipid composition
changes in each of the remaining mutants influenced B uptake to various extents. These data suggest that lipid composition
of the plasma membrane can affect total B uptake.
Received: 15 October 1999/Revised: 11 February 2000 相似文献