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Effects of DNase production, plasmid size, and restriction barriers on transformation of Vibrio cholerae by electroporation and osmotic shock 总被引:14,自引:0,他引:14
Hilda Marcus Julian M. Ketley James B. Kaper Randall K. Holmes 《FEMS microbiology letters》1990,68(1-2):149-154
Attempts to transform wild type strains of V. cholerae with plasmid DNA by traditional osmotic shock methods were not successful. A mutant of V. cholerae that was deficient in extracellular DNase was transformed with plasmid DNA by osmotic shock, demonstrating directly that extracellular DNase is a major barrier to transformation of V. cholerae. Transformation of wild type and DNase-negative strains of V. cholerae was accomplished by electroporation. Efficiency of transformation by electroporation increased with field strength, decreased with plasmid size, and was relatively insensitive to changes in the electrolyte composition of the buffer as long as isotonic sucrose was present. Host-controlled modification/restriction systems also affected transformation efficiency in V. cholerae. 相似文献
3.
Summary Establishment of Plantago lanceolata and P. major ssp major among grass was studied in a field experiment in which survival and selection on date of seedling emergence and plant size was investigated in relation to the vegetation structure. P. major — in contrast to P. lanceolata — was not able to establish itself in grass because of its lower competitive ability caused by later germination, smaller seedling size, and shorter leaves. In both species there was selection for early germination. For P. lanceolata a significant correlation was found between the strength of selection and the light climate, determined by the structure of the grass sward. Plants that germinated early were at an advantage because they were larger, especially the leaves, when compared with plants that germinated late. It seems likely that selection was mainly by competition for light. Contrary to expectation P. major-seedlings had a higher shade tolerance than those of P. lanceolata. The performance of both species is discussed in relation to their different life strategies.Grassland species research group publication no 142 相似文献
4.
Cloning and expression of the Vibrio cholerae neuraminidase gene nanH in Escherichia coli 总被引:9,自引:2,他引:7
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A cosmid gene bank of Vibrio cholerae 395, classical Ogawa, was screened in Escherichia coli HB101 for expression of the vibrio neuraminidase (NANase) gene nanH (N-acylneuraminate glycohydrolase). Positive clones were identified by their ability to cleave the fluorogenic NANase substrate 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid. Seven NANase-positive clones were detected after screening 683 cosmid isolates with a rapid, qualitative plate assay method. The nanH gene was subcloned from one of the cosmids and was located within a 4.8-kilobase-pair BglII restriction endonuclease fragment. Evidence that nanH was the NANase structural gene was obtained by transposon mutagenesis and by purification and comparison of the cloned gene product with the secreted NANase purified from the parent V. cholerae strain. The sequence of the first 20 amino-terminal amino acids of the secreted NANase purified from V. cholerae was determined by automated Edman degradation and matched perfectly with the amino acid sequence predicted from nucleotide sequencing of nanH. The sequence data also revealed the existence of a potential signal peptide that was apparently processed from NANase in both V. cholerae and E. coli. In contrast to V. cholerae, E. coli nanH+ clones did not secrete NANase into the growth medium, retaining most of the enzyme in the periplasmic compartment. Kinetic studies in V. cholerae showed that nanH expression and NANase secretion were temporally correlated as cells in batch culture entered late-exponential-phase growth. Similar kinetics were observed in at least one of the E. coli nanH+ clones, suggesting that nanH expression in E. coli might be controlled by some of the same signals as in the parent V. cholerae strain. 相似文献
5.
The stability properties of cucumber mosaic virus were investigated in relation to those of two other, well-described, icosahedral RNA viruses of similar geometry; the cowpea chlorotic mottle virus and the turnip yellow mosaic virus. High concentrations of neutral salts caused the dissociation of cucumber mosaic virus into its constituent RNA and protein subunits irrespective of the pH of the solution. At low ionic strength the effect of pH on the infectivity and the sedimentation behavior of the virus was tested between pH 4.0 and 8.5. No effect was noticed in this range, but significant change became evident at pH 9.8 and was complete at pH 10.45. The products of this alkaline treatment were a mixture of slower sedimenting nucleoproteins. The RNA inside cucumber mosaic virus was accessible to pancreatic ribonuclease. There was little or no pH-dependence of the ribonuclease susceptibility. Under no circumstances were protein capsids of cucumber mosaic virus ever obtained, neither by degradation of the virion, reassembly of the protein subunits, nor directly from the infected plant. These stability properties of cucumber mosaic virus are strikingly different from those of cowpea chlorotic mottle virus and turnip yellow mosaic virus, as reported in the literature, and indicate the possession of only weak inter-protein subunit linkages, or their total absence. 相似文献
6.
Hans Thijs Julie Garde Theo Goosen Brian Tomsett Klaas Swart Christa Heyting Henk W. J. Broek 《Molecular & general genetics : MGG》1995,247(3):343-350
We have examined polarity of meiotic gene conversion in the niiA-niaD gene cluster of Aspergillus nidulans in two-point crosses. The type and position of the mutations represented by the niaD alleles and the correlation between the relative frequency of gene conversion and the physical position of these mutations were determined. We show that polarity of meiotic gene conversion is 5 to 3 (transcribed strand) within the niaD gene. Additional crosses involving a niiA allele and a niaD allele show little polarity of gene conversion, which suggests that the recombination events leading to restoration of the niaD gene are initiated upstream of the coding region of the niaD gene but within the niiA-niaD gene cluster, possibly within the intergenic promoter region. 相似文献
7.
8.
From data obtained by differential scanning calorimetry phase diagrams were constructed, using a thermodynamically based fitting method. The following binary mixtures of phosphatidylcholines in water were studied: 14:0/14:0-glycerophosphocholine/16:0/16:0-glucerophosphocholine, 14:0/14:0-glycerophosphocholine/18:0/18:0-glycerophosphocholine, 12:0/12:0-glycerophosphocholine/16:0/16:0-glycerophosphocholine, 18:1t/18:1t-glycerophosphocholine/14:0/14:0-glycerophosphocholine and 18:1t/18:1t-glycerophosphocholine/16:0/16:0-glycerophosphocholine. A comparison is made of the present results with those obtained using probe techniques and the differences are discussed. 相似文献
9.
From data obtained by differential scanning calorimetry phase diagrams were constructed, using a thermodynamically based fitting method. The following binary mixtures of phosphatidylcholines in water were studied: 14:0/ 14:0-glycerophosphocholine/16:0/16:0-glycerophosphocholine, 14:0/14:0-glycerophosphocholine /18:0/18:0-glycerophosphocholine, 12:0/12:0-glycerophosphocholine /16:0/16:0-glycerophosphocholine, 18:1t/18:1t-glycerophosphocholine /14:0/14:0-glycerophosphocholine and 18:1t/18:1t-glycerophosphocholine /16:0/16:0-glycerophosphocholine.A comparison is made of the present results with those obtained using probe techniques and the differences are discussed. 相似文献
10.
Occurrence of Vibrio cholerae serotype O1 in Maryland and Louisiana estuaries. 总被引:36,自引:27,他引:9
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R R Colwell R J Seidler J Kaper S W Joseph S Garges H Lockman D Maneval H Bradford N Roberts E Remmers I Huq A Huq 《Applied microbiology》1981,41(2):555-558
Vibrio cholerae serotype O1 has been isolated from Chesapeake Bay in Maryland and estuaries and sewers in Louisiana. The occurrence of V. cholerae O1 in the aquatic environment in the absence of human disease suggests that this organism survives and multiples in the natural environment. 相似文献