共查询到20条相似文献,搜索用时 15 毫秒
1.
Mark Achtman Sybille Schwuchow Reiner Helmuth Giovanna Morelli Paul A. Manning 《Molecular & general genetics : MGG》1978,164(2):171-183
Summary Conjugation-deficient (Con-) mutants of Escherichia coli K-12 have been previously described which were defective in recipient ability. Such Con- mutants were obtained from several laboratories and retested by a standardized set of procedures. Many of the mutants did not satisfy minimal criteria for conjugation-deficiency and were discarded. The remaining mutants included 11 ConF- mutants mutated in or near the ompA cistron, 3 ConF- mutants synthesizing a heptose-deficient lipopolysaccharide and 1 ConI- mutants synthesizing a defective lipopolysaccharide. This set of mutants was tested for resistance to a variety of bacteriophages and colicins; the only phenotype fully correlated with the ConF- phenotype was that of resistance to colicin L. No simple correlation existed between the protein profile (on SDS polyacrylamide gel electrophoresis) of cell envelope outer membrane preparations and conjugation deficiency. However, many ConF- mutants did not synthesize detectable levels of outer membrane protein II* and protein II* may have been nonfunctional in the remainder. All the ConF- mutants were conjugation-deficient when matings were conducted in liquid but (with one exception) were conjugation-proficient on the surfaces of membrane filters. None of the ConF- mutants formed stable mating aggregates in liquid with (Flac)+ donor cells although all bound purified F pili. The ConF- phenotype associated with a II*-deficient recipient could be mimicked by the addition of purified protein II* (solubilized with lipopolysaccharide). In both cases, the formation of stable mating aggregates (analyzed with an improved Coulter counter technique) was inhibited whereas unstable mating aggregates were detected by electron microscopy. F pilus and wall to wall contacts were both observed under these conditions by electron microscopy. These results were used to define a stage in F-promoted conjugation, the stabilization stage, which requires the functional interaction of protein II* and lipopolysaccharide in the outer membrane of the recipient cell. 相似文献
2.
M. Grenon J. Tillit K. Piard G. Baldacci S. Francesconi 《Molecular & general genetics : MGG》1999,260(6):522-534
We have isolated a mutant in fission yeast, in which mitosis is uncoupled from completion of DNA replication when DNA synthesis
is impaired by a thermosensitive mutation in the gene encoding the catalytic subunit of DNA polymerase δ. By functional complementation,
we cloned the wild-type gene and identified it as the recently cloned checkpoint gene crb2
+
/rhp9
+
. This gene has been implicated in the DNA damage checkpoint and acts in the Chk1 pathway. Unlike the deleted strain dcrb2,
cells bearing the crb2-1 allele were not affected in the DNA repair checkpoint after UV or MMS treatment at 30° C, but were defective in this checkpoint
function when treated with MMS at 37° C. We analysed the involvement of Crb2 in the S/M checkpoint by blocking DNA replication
with hydroxyurea, by using S phase cdc mutants, or by overexpression of the mutant PCNA L68S. Both crb2 mutants were unable to maintain the S/M checkpoint at 37° C. Furthermore, the crb2
+
gene was required, together with the cds1
+
gene, for the S/M checkpoint at 30° C. Finally, both the crb2 deletion and the crb2-1 allele induced a rapid death phenotype in the polδts3 background at both 30° C and 37° C. The rapid death phenotype was independent of the checkpoint functions.
Received: 25 May 1998 / Accepted: 21 September 1998 相似文献
3.
Brooks Low 《Molecular & general genetics : MGG》1973,122(2):119-130
Summary The recombinant forming ability of recB
– or recC
– strains of E. coli K12 is almost totally recovered in merozygotes which are heterozygous for a genetic locus denoted rac which is located five minutes clockwise from trp on the genetic map. This transient recovery phenomenon only occurs when the donor strain is rac
+ (wild type) and the recipient strain is rac
-. The recombinants derived from such crosses all have the normal phenotype characteristic of recB
– (or recC
–) strains, and they are almost always rac
-. The results imply that the rac
+ locus (or loci) is zygotically expressed and excised from the chromosome in a manner which is analogous to the zygotic induction of a prophage. 相似文献
4.
Summary pKM101, a plasmid R factor of the N compatibility group increases methylmethane sulfonate mutagenesis and diminishes UV-killing in recA
+
lex
+ and recA
+
lex
– strains, but not in recA
–
lex
+ strains. The induction of a reclex dependent colicin is not present in lex
– strains carrying the pKM101 factor. These facts indicate that pKM101 acts through an error-prone DNA repair system, which is recA
+ dependent, but not lex
+ dependent.This paper is published on the occasion of Dr. C. Callerio's seventy-fifth birthday 相似文献
5.
S. Nakamura S. Asakawa N. Ohmido K. Fukui N. Shimizu S. Kawasaki 《Molecular & general genetics : MGG》1997,254(6):611-620
We constructed a rice Bacterial Artificial Chromosome (BAC) library from green leaf protoplasts of the cultivar Shimokita
harboring the rice blast resistance gene Pi-ta. The average insert size of 155 kb and the library size of seven genome equivalents make it one of the most comprehensive
BAC libraries available, and larger than many plant YAC libraries. The library clones were plated on seven high density membranes
of microplate size, enabling efficient colony identification in colony hybridization experiments. Seven percent of clones
carried chloroplast DNA. By probing with markers close to the blast resistance genes Pi-ta
2
(closely linked to Pi-ta) and Pi-b, respectively located in the centromeric region of chromosome 12 and near the telomeric end of chromosome 2, on average 2.2 ± 1.3
and 8.0 ± 2.6 BAC clones/marker were isolated. Differences in chromosomal structures may contribute to this wide variation
in yield. A contig of about 800 kb, consisting of 19 clones, was constructed in the Pi-ta
2
region. This region had a high frequency of repetitive sequences. To circumvent this difficulty, we devised a “two-step walking”
method. The contig spanned a 300 kb region between markers located at 0 cM and 0.3 cM from Pi-ta
2
. The ratio of physical to genetic distances (> 1,000 kb/cM) was more than three times larger than the average of rice (300
kb/cM). The low recombination rate and high frequency of repetitive sequences may also be related to the near centromeric
character of this region. Fluorescent in situ hybridization (FISH) with a BAC clone from the Pi-b region yielded very clear signals on the long arm of chromosome 2, while a clone from the Pi-ta
2
region showed various cross-hybridizing signals near the centromeric regions of all chromosomes.
Received: 14 August 1996 / Accepted: 2 December 1996 相似文献
6.
M. Ficker H.-H. Kirch R. Eijlander E. Jacobsen R. D. Thompson 《Molecular & general genetics : MGG》1998,257(2):132-142
A functional analysis of the promoter of the S
2
-RNase gene from potato was performed in transgenic potato and tobacco plants, using a deletion series of S
2
-RNase promoter GUS fusions. A detailed histochemical and quantitative analysis of the transgenic tobacco plants revealed that S
2
promoter fragments ranging in size from 5.6 kb in length down to 0.2 kb mediate a weak developmentally regulated expression
in the pistil, and strong ectopic expression in pollen. In the pistil, different expression patterns were seen depending on
the transformant, the predominant one being characterised by expression in the stigma and the transmitting tract of the style,
whereas a few plants showed expression exclusively either in the stigma or in the stylar transmitting tissue. All transformants
also showed GUS expression in the placental epidermis of the ovary. Two sequences that are conserved between the potato S
1
-RNase and S
2
-RNase promoters, termed motif I and motif III, are located in a fragment of the S
2
promoter extending from position −200 to bp −100, and motif II, located between bp −498 and −480, was identified on the basis
of sequence comparisons between pistil-specific promoters. Motif II was found to be dispensible for pistil-specific and for
pollen-specific expression. Two submotifs, A and B, were identified within motif I. Both were essential for expression in
the pistil but only B was necessary for expression in pollen. Although motif III has a similar bipartite structure and sequence
to motif I, it was not sufficient to confer either pollen- or pistil-specific expression. However, deletion of motif III abolished
pollen-specific expression in transient expression experiments, suggesting that an interaction between the two sequence motifs
may be needed to specify cell type-specific expression. In transgenic potato the S
2
-RNase promoter also mediates expression in pollen and in the pistil; however, significantly fewer plants showed expression than
in tobacco, with most plants also exhibiting GUS expression in other tissues.
Received: 7 August 1997 / Accepted: 8 September 1997 相似文献
7.
K. Kofler S. K?chl W. Parson M. Erdel G. Utermann G. Baier 《Molecular & general genetics : MGG》1998,259(4):398-403
Members of the protein kinase C (PKC) family of serine/threonine kinases, in particular PKCθ, play critical roles in the regulation
of differentiation and proliferation of T lymphocytes. In this study the genomic structure of the human PRKCQ gene that encodes
PKCθ was determined. Two genomic P1 clones were isolated from human P1 libraries using the PKCθ cDNA as a probe and have been
used to confirm the assignment of the single PRKCQ locus to chromosome 10p15 by FISH analysis. The PRKCQ locus, the first
mammalian PKC gene locus characterized so far, spans approximately 62 kb and is composed of 15 coding exons and 14 introns,
varying in size between 98 and 16 000 bp. All exon-intron boundaries have been determined by long-range PCR and subsequent
DNA sequence analysis. Comparison with other known genomic PKC genes reveals a high degree of homology to the genomic organization
of the Drosophila melanogaster dPRKC gene. Alignment of the intron positions in the PRKCQ gene with the intron locations in the dPRKC gene indicates that
the sites of seven of the 14 PRKCQ introns are exactly conserved. Exons 5 (32 bp), 11 (174 bp) and 12 (92 bp) share highest
similarity in size, organization and primary structure with their counterparts in the Drosophila gene. On the basis of this
knowledge of the genomic PRKCQ locus, a directed search for potential genetic polymorphisms and/or genetic abnormalities involved
in human genetic disease(s) can now be initiated.
Received: 6 February 1998 / Accepted: 25 May 1998 相似文献
8.
Chaoqiang Jiang Qingsong Zheng Zhaopu Liu Wenjun Xu Ling Liu Gengmao Zhao Xiaohua Long 《Trees - Structure and Function》2012,26(3):685-694
Salinity is a major abiotic stress factor limiting plant growth and productivity. One possible method to enhance plant salt-resistance
is to compartmentalize sodium ions away from the cytosol. In the present work, a vacuolar Na+/H+ antiporter gene AtNHX1 from Arabidopsis thaliana, was transferred into Populus × euramericana ‘Neva’ by Agrobacterium tumefaciens in order to enhance poplar salt-resistance. The results showed that the transgenic poplar were more resistant to NaCl than
the wild-type (WT) in greenhouse condition. Compared with the WT, plant growth and photosynthetic capacity of the transgenic
plants were enhanced, and the transgenic plants accumulated more Na+ and K+ in roots and leaves under the same NaCl condition, whereas malondialdehyde and relative electrical conductivity were lower.
All of these properties of the transgenic poplar were likely to be a consequence of the overexpression of AtNHX1 caused Na+ sequestration in the vacuoles and improved K+ absorption, thus reducing their toxic effects. These results indicated overexpression of the AtNHX1 enhanced salt-resistance of poplar, and AtNHX1 played an important role in the compartmentation of Na+ into the vacuoles. Therefore, this study provides an effective way for improving salt resistance in trees. 相似文献
9.
Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc
– mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc
– mutants were tested for their ethanol sensitivity; among them, cdc1–7 and cdc13–117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc
– phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1
+ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent. 相似文献
10.
Halocins: are they involved in the competition between halobacteria in saltern ponds? 总被引:1,自引:0,他引:1
Many representatives of the family Halobacteriaceae ("halobacteria") excrete halophilic bacteriocins (halocins) that inhibit the growth of other halobacteria. In spite of the
fact that halocin production is widespread among the Halobacteriaceae, no information is available on their ecological significance. To test whether halocins may play a role in the interspecies
competition between dif-ferent types of halobacteria in saltern crystallizer ponds inhabited by dense communities of these
red halophiles, we assayed for halocins active against a variety of halobacteria in salterns from different locations worldwide.
Detection of halocin activity was based on the inhibition of growth of indicator organisms on agar plates, the decreased incorporation
of radiolabeled substrates, and microscopic examinations. No halocin activity was detected in any of the brines examined,
in spite of the fact that halocin production was demonstrated in cultures of most microorganisms isolated from these brines.
Thus, the contribution of halocins in the competition between different halobacteria in hypersaline aquatic environments is
probably negligible.
Received: July 29, 1999 / Accepted: October 18, 1999 相似文献
11.
A method for measuring the gas temperature in an oxygen plasma by spectroscopy of the electronic transition from the O2(b
1Σ
g
+
, v = 0) metastable state of molecular oxygen into the O2(X
3Σ
g
−
, v = 0) ground state is considered in detail. The method is verified experimentally for the plasma of dc glow discharge in pure
oxygen. It is shown that the gas temperature can be determined by analyzing high-resolution spectra of the P branch of this transition, no matter whether its fine structure (P
P and P
Q branches) is resolved or masked, provided that the rotational structure of the spectrum is resolved. The feasibility of the
method proposed in 1999 by P. Maco and P. Veis for determining the gas temperature from the ratio between the intensity maxima
of the R and P branches of the O2(b
1Σ
g
+
, v = 0) → O2(X
3Σ
g
−
, v = 0) transition in a poorly resolved spectrum was studied experimentally. It is shown that, in order to use this method,
it is necessary to know the spectrograph instrumental function. The effect of the spatial inhomogeneity of the temperature
and concentration of O2(b
1Σ
g
+
) molecules on the accuracy of integral (over the plasma volume) measurements of the gas temperature is investigated using
spatially resolved spectroscopy of the O2(b
1Σ
g
+
, v = 0) → O2(X
3Σ
g
−
, v = 0) transition. It is shown that precise measurements of the temperature require that the optical measurement system be
thoroughly adjusted in order for the temperature and concentration of the emitting particles to vary insignificantly over
the optically selected volume.
Original Russian Text ? S.M. Zyryanov, D.V. Lopaev, 2007, published in Fizika Plazmy, 2007, Vol. 33, No. 6, pp. 563–574. 相似文献
12.
13.
Ivor P. B. Tittawella 《Molecular & general genetics : MGG》1976,146(1):79-83
Summary In a rif
S/rifR heterodiploid strain of E. coli, a 4 minute pulse of rifampicin can induce a prolonged (>60 min) increase in the rate of synthesis of the RNA polymerase subunits, and . The application of a constraint on the fidelity of protein synthesis during, but not after, the rifampicin pulse partially arrests the development of this capacity for subunit synthesis. I discuss the implications of these findings in relation to the control of the operon in E. coli. 相似文献
14.
P. Pic 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,123(2):155-162
Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na+
and of Cl–
and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not
. InFundulus,
is also decreased. Transfer of the two species from SW to fresh water (FW) reduces
and
by 75 to 85% and leads to a large inversion of P.D. When K+ is added to FW, a gill depolarization occurs, as well as a large increase of
and
.These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na+ (
) being greater than that to Cl– (
), 2) a Cl–/Cl– exchange independent of P.D. is associated with the Cl– pump; 3) Cl– pump activity is linked to Na+/K+ exchange which in turn is associated to a Na+/Na+ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of
and
observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of
which becomes equal to
in both species.As a result of stress, the K+-activated Na+ and Cl– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil. 相似文献
15.
Sandra Díaz-Sánchez Ainhoa Mateo Moriones Fabián Casas Ursula H?fle 《European Journal of Wildlife Research》2012,58(1):99-105
For hunting purposes, several millions of red-legged partridges (Alectoris rufa) are released each year in Spain, and these releases have the potential to introduce new parasites and disease into wild
populations. We studied the prevalence of Escherichia coli, Campylobacter sp. and Salmonella sp. in the intestinal flora of red-legged partridges from three different husbandry groups: farm-reared, restocked and natural
populations. Prevalence of E. coli was significantly higher in farm-reared (45%, p = 0.01) and restocked partridges (60%, p < 0.001) than in wild ones (6%, p > 0.05). The prevalence of Campylobacter sp. (23%, 100 out of 444) did not differ significantly between these three husbandry groups, and Salmonella sp. was only detected in a group of partridge chicks on one of the farms studied (0.9%, 5 out of 544). These results suggest
that farm-reared and restocked partridges can act as carriers of these three enteropathogens and highlight a potential risk
of transmission to natural populations via the releases of farm-reared partridges. However, future investigations are needed
regarding the relation of the isolated bacteria with zoonotic strains and dissemination of antibiotic resistant microorganisms,
especially E. coli, and to better evaluate the effect that these three enteropathogens have on partridge health and on the success of restocking
with farm-reared birds. 相似文献
16.
An in vitro nucleosome assembly system has been established from cell-free extracts of the fungusUstilago maydis. The extract catalyzed DNA supercoiling in the absence of exogenously added co-factors such as ATP and MgCl2 and was inhibited by moderate concentrations (200 mM) of KCl or NaCl. DNA supercoiling occurs via the formation of nucleosomes. Similar extracts, displaying the same activity, were prepared fromSaccharomyces cerevisiae andCandida albicans, suggesting that the extract preparation protocol may be useful for many lower eukaryotic systems. An extract prepared from a strain ofU. maydis lacking topoisomerase I failed to catalyze nucleosome assembly, clearly implicating this enzyme in this process. Addition of purified topoisomerase I, and, to a lesser extent, topoisomerase II, to the top1– extract regenerated the supercoiling activity. Our results provide a method for preparing assembly extracts from organisms, that are particularly amenable to genetic manipulation. 相似文献
17.
18.
Summary This paper describes a method of screening mutagenised populations of an E. coli gal
A
–
gal
B
–
F-prime merodiploid for mutants defective in recombination. The method relies on scoring colonies on Eosin-Methylene Blue agar that have fewer than normal numbers of Gal+ papillae. With a suitable choice of gal
–mutations most of the papillae arise by recombination and some of those colonies with less than normal numbers prove to be defective in some aspect of recombination or DNA repair. In addition to strains carrying mutations that can be ascribed to known loci, several novel mutant phenotypes were identified. 相似文献
19.
20.
Sara A. Al-Jaberi Salma Ben-Salem Meriam Messedi Fatma Ayadi Lihadh Al-Gazali Bassam R. Ali 《Gene》2013