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211.
Christopher N. Topp José Ruiz-Herrera Alfredo D. Martínez-Espinoza Scott E. Gold 《Current microbiology》2002,44(1):67-70
A previous report indicated that insertion of the carboxin resistance (cbx
R
) gene into the Ustilago maydis genome impaired the pathogenic ability of the fungus towards Zea mays, the corn host. Because we had anecdotal evidence from work in our laboratory that this was not necessarily the case we decided
to determine how general was the observation of reduced pathogenicity associated with cbx
R
. To accomplish this we tested the pathogenicity of several strains that had been transformed with the cbx
R
gene and compared them with non-transformed strains or strains transformed with the gene conferring hygromycin resistance
which is a commonly used selectable marker in this fungus. Our results indicate that carboxin resistance does not significantly
alter pathogenicity and is therefore a suitable marker for use in genetic analysis of U. maydis.
Received: 29 May 2001 / Accepted: 30 July 2001 相似文献
212.
Graham Wilkes Julie Brassard Thomas A. Edge Victor Gannon Natalie Gottschall Cassandra C. Jokinen Tineke H. Jones Izhar U. H. Khan Romain Marti Mark D. Sunohara Edward Topp David R. Lapen 《Applied and environmental microbiology》2014,80(12):3708-3720
Surface waters from paired agricultural watersheds under controlled tile drainage (CTD) and uncontrolled tile drainage (UCTD) were monitored over 7 years in order to determine if there was an effect of CTD (imposed during the growing season) on occurrences and loadings of bacterial and viral pathogens, coliphages, and microbial source tracking markers. There were significantly lower occurrences of human, ruminant, and livestock (ruminant plus pig) Bacteroidales markers in the CTD watershed in relation to the UCTD watershed. As for pathogens, there were significantly lower occurrences of Salmonella spp. and Arcobacter spp. in the CTD watershed. There were no instances where there were significantly higher quantitative loadings of any microbial target in the CTD watershed, except for F-specific DNA (F-DNA) and F-RNA coliphages, perhaps as a result of fecal inputs from a hobby farm independent of the drainage practice treatments. There was lower loading of the ruminant marker in the CTD watershed in relation to the UCTD system, and results were significant at the level P = 0.06. The odds of Salmonella spp. occurring increased when a ruminant marker was present relative to when the ruminant marker was absent, yet for Arcobacter spp., the odds of this pathogen occurring significantly decreased when a ruminant marker was present relative to when the ruminant marker was absent (but increased when a wildlife marker was present relative to when the wildlife marker was absent). Interestingly, the odds of norovirus GII (associated with human and swine) occurring in water increased significantly when a ruminant marker was present relative to when a ruminant marker was absent. Overall, this study suggests that fecal pollution from tile-drained fields to stream could be reduced by CTD utilization. 相似文献
213.
C E Stotz R T Borchardt C R Middaugh T J Siahaan D Vander Velde E M Topp 《The journal of peptide research》2004,63(4):371-382
A spontaneously folding beta-hairpin peptide (Lys-Lys-Tyr-Thr-Val-Ser-Ile-Asn-Gly-Lys-Lys-Ile-Thr-Val-Ser-Ile) and related cyclic (cyclo-Gly-Lys-Tyr-Ile-Asn-Gly-Lys-Ile-Ile-Asn) and linear (Ser-Ile-Asn-Gly-Lys) controls were studied to determine the effects of various factors on secondary structure. Secondary structure was evaluated using circular dichroism (CD) and 1D and 2D (1)H nuclear magnetic resonance (NMR). The effects of chemical modifications in the peptide and various solution conditions were investigated to determine their impact on peptide structure. The beta-hairpin peptide displayed a CD minimum at 216 nm and a TOCSY i + 1 - i + 2 and i + 2 -i + 3 interaction, confirming the expected structure. Using NMR alpha-proton (H(alpha)) chemical shifts, the extents of folding of the beta-hairpin and linear control were estimated to be 51 and 25% of the cyclic control (pH 4, 37 degrees C), which was taken to be maximally folded. Substitution of iso-aspartic acid for Asn reduced the secondary structure dramatically; substitution of aspartic acid for Asn also disrupted the structure. This result suggests that deamidation in unconstrained beta-turns may have adverse effects on secondary structure. N-terminal acetylation and extreme pH conditions also reduced structure, while the addition of methanol increased structure. 相似文献
214.
215.
Widespread distribution of deletions of the bgl operon in natural isolates of Escherichia coli 总被引:2,自引:0,他引:2
A deletion that includes the bgl (beta-glucoside utilization) operon of
Escherichia coli was originally detected in several rarely occurring
natural isolates that utilize cellobiose. Here I show that bgl deletions
are present in 95% of the Cel+ isolates obtained from diverse sources. They
are also present in 29% of the Cel- strains in two different collections of
natural isolates of E. coli. At least three versions of bgl deletions are
present in E. coli populations. In the most common version approximately 8
kb of DNA around the bgl region of E. coli K12 is replaced by a specific
6.5-kb DNA fragment. In another version a deletion of similar length is not
replaced by the same sequence. A third version involves deletion of
approximately 14 kb without the replacement fragment being present. The
distribution of these deletions suggests that the version 1 deletion
occurred very early in the history of E coli. It also appears likely that
there is selection for bgl deletions in Cel+ strains of E. coli. The
presence of the version 1 deletion within distantly related phylogenetic
groups of E. coli provides evidence for recombination within natural
populations of E coli.
相似文献
216.
Sine Hovbye Topp Søren K. Rasmussen Lilli Sander 《Plant Cell, Tissue and Organ Culture》2008,93(3):241-248
Reduction in the amounts of active gibberellic acids (GA) in elongating cuttings from the ornamental crop Kalanchoe blossfeldiana were pursued by genetic manipulation as an alternative to synthetic growth regulators. An alcohol inducible promoter system
was used to control silencing of GA activating enzymes. Apart from affecting the stem length, abnormal levels of GA can lead
to altered flowering time, lacking seed maturation and changes in morphology. The effects of down regulating a group of GA
20-oxidases were investigated in fast growing cuttings of K.
blossfeldiana Poelln. cv. Molly. The transgenic plants were phenotypically indistinguishable from wild type plants until silencing was
induced by low concentrations of ethanol. Treated plants were reduced in height but otherwise appeared normal; flowering was
delayed but with large variations in time between the transgenic lines. These data indicate that optimisation of the ethanol
treatments can enable us to produce more compact growing plants still maintaining normal flowering. 相似文献
217.
Romain Marti Yuan-Ching Tien Roger Murray Andrew Scott Lyne Sabourin Edward Topp 《Applied and environmental microbiology》2014,80(10):3258-3265
Animal manures recycled onto crop production land carry antibiotic-resistant bacteria. The present study evaluated the fate in soil of selected genes associated with antibiotic resistance or genetic mobility in field plots cropped to vegetables and managed according to normal farming practice. Referenced to unmanured soil, fertilization with swine or dairy manure increased the relative abundance of the gene targets sul1, erm(B), str(B), int1, and IncW repA. Following manure application in the spring of 2012, gene copy number decayed exponentially, reaching background levels by the fall of 2012. In contrast, gene copy number following manure application in the fall of 2012 or spring of 2013 increased significantly in the weeks following application and then declined. In both cases, the relative abundance of gene copy numbers had not returned to background levels by the fall of 2013. Overall, these results suggest that under conditions characteristic of agriculture in a humid continental climate, a 1-year period following a commercial application of raw manure is sufficient to ensure that an additional soil burden of antibiotic resistance genes approaches background. The relative abundance of several gene targets exceeded background during the growing season following a spring application or an application done the previous fall. Results from the present study reinforce the advisability of treating manure prior to use in crop production systems. 相似文献
218.
Retransformation of a simian virus 40 revertant cell line, which is resistant to viral and DNA infections, by microinjection of viral DNA. 总被引:5,自引:0,他引:5
We have isolated morphological transformants of cultured cells as dense foci on a monolayer of normal cells appproximately 4 weeks after microinjection of purified simian virus 40 DNA (200 to 400 molecules per cell) directly into the nucleus. Both Rat 1 (an established contact-inhibited rat embryo fibroblast line) and F1' 1--4 (a 5-fluorodeoxyuridine-selected flat revertant from the simian virus 40-transformed 14B cell line) were transformed with an efficiency of 5 to 10% of the cells injected. F1' 1--4 is not susceptible to retransformation by either viral or DNA infection (by calcium phosphate-facilitated cellular uptake), and as a result it had previously been thought to possess a host mutation preventing expression of the simian virus 40 genome. 相似文献
219.