scholarly journals Symbiotic Plasmid Rearrangement in Rhizobium leguminosarum bv. viciae VF39SM

2001 ◽  
Vol 183 (6) ◽  
pp. 2141-2144 ◽  
Author(s):  
Xue-Xian Zhang ◽  
Bob Kosier ◽  
Ursula B. Priefer
Keyword(s):  
Parent Strain ◽  
Rhizobium Leguminosarum ◽  
Plasmid Profile ◽  
The Other ◽  
Dna Fragments ◽  
Symbiotic Genes ◽  
Symbiotic Plasmid ◽  
Other Hand

ABSTRACT A rearrangement between the symbiotic plasmid (pRleVF39d) and a nonsymbiotic plasmid (pRleVF39b) in Rhizobium leguminosarumbv. viciae VF39 was observed. The rearranged derivative showed the same plasmid profile as its parent strain, but hybridization to nod, fix, and nif genes indicated that most of the symbiotic genes were now present on a plasmid corresponding in size to pRleVF39b instead of pRleVF39d. On the other hand, some DNA fragments originating from pRleVF39b now hybridized to the plasmid band at the position of pRleVF39d. These results suggest that a reciprocal but unequal DNA exchange between the two plasmids had occurred.

Nutritional Requirement for 4-Aminobenzoate Caused by Mutation of Dihydropteroate Synthetase

1976 ◽  
Vol 31 (5-6) ◽  
pp. 285-287 ◽  
Author(s):  
Helmut Rappold ◽  
Adelbert Bacher
Keyword(s):  
Parent Strain ◽  
The Other ◽  
Synthetase Activity ◽  
Nutritional Requirement ◽  
Wild Type ◽  
Aerobacter Aerogenes ◽  
Low Level ◽  
Other Hand ◽  
High Concentrations

Abstract Aerobacter aerogenes mutant 62-1 AC requires high concentrations of 4-aminobenzoate for growth. The mutant accumulates N-glucosyl-4-aminobenzoate and has an intact 4-aminobenzoate synthetase (Bacher, Gilch, Rappold, and Lingens, Z. Naturforsch. 28c, 614 - 617 [1973]). On the other hand the ability of the mutant to synthesize dihydropteroate is markedly reduced. The dihydropteroate synthetase level of mutant 62-1 AC is 1% as compared to the parent strain. Spontaneous revertants of mutant 62-1 AC show wild type levels of dihydropteroate synthetase. We conclude that the requirement for 4-aminobenzoate in mutant 62-1 AC is due to poor utilization of 4-aminobenzoate as a consequence of the low level of dihydropteroate synthetase activity.

scholarly journals SUPPRESSION OF THE FORMATION OF POLYGENOTYPIC RECOMBINANT COLONIES BY A maf MUTATION IN MATING WITH HfrH

Genetics ◽  
1979 ◽  
Vol 93 (2) ◽  
pp. 345-351
Author(s):  
Jonathan T Ou ◽  
Li-Mei Kuo
Keyword(s):  
Production Rate ◽  
The Other ◽  
Dna Fragments ◽  
Amber Mutation ◽  
Other Hand ◽  
High Production Rate ◽  
High Production ◽  
Spontaneous Revertant

ABSTRACT W3011, a Cavalli-type Hfr (HfrC), was mated with F-KY9474, maf-1, which cannot maintain F or F-like plasmids, and with F-OU9474, Maf+, a spontaneous revertant of KY9474. The recombinant colonies obtained were 100% monogenotypic from KY9474 and 90% monogenotypic from OU9474. On the other hand, in matings with OU11, a Hayes-type Hfr (HfrH), and these two F-strains, recombinant colonies derived from KY9474 showed only 22% polygenotypic recombinant colonies; whereas, those derived from OU9474 showed a high production rate (57%) of polygenotypic recombinant colonies. Among the polygenotypic recombinant colonies derived from KY9474 maf-1, 50% contained three or more recombinant types. These were probably derived from a small fraction of Maf+ revertants in the KY9474 population, as suggested by the results of mating this strain with M80, an F′ strain that contains an amber mutation in traH. These results support the hypothesis that the donor DNA fragments derived from an HfrH can undergo a limited replication in the recipient to produce polygenotypic recombinant colonies, whereas those derived from HfrC cannot.

Unusual localization of nod and nif genes in Rhizobium leguminosarum bv. viciae

1997 ◽  
Vol 43 (4) ◽  
pp. 399-402 ◽  
Author(s):  
Sylvie-Isabelle Mazurier ◽  
Gisele Laguerre
Keyword(s):  
Plasmid Dna ◽  
Genomic Dna ◽  
Rhizobium Leguminosarum ◽  
Large Plasmid ◽  
Nif Genes ◽  
Symbiotic Genes ◽  
Nod Genes ◽  
Symbiotic Plasmid ◽  
Wild Strains ◽  
Sym Plasmid

Genomic DNA from seven strains of Rhizobium leguminosarum bv. viciae isolated from nodules of field-grown lentils showed homology to nod and nif gene probes, whereas plasmid DNA did not hybridize with these probes. The results suggest that symbiotic genes could be located on the chromosome or perhaps on a very large plasmid that could not be resolved in Eckhardt gels. Each strain contained one plasmid that hybridized with a pSym isolated from a R. leguminosarum strain of the same field population. This finding led us to hypothesize that the nod and nif genes of the seven strains might have originated from a Sym plasmid and have been integrated into another replicon. The ability to nodulate vetch was confirmed for all of the seven strains. Thus, wild strains of R. leguminosarum bv. viciae that nodulate vetch carry nod and nif genes either on the chromosome or on an extrachromosomal replicon of size much larger than the pSyms hitherto described.Key words: Rhizobium leguminosarum, nod genes, nif genes, chromosome, symbiotic plasmid, megaplasmid.

Expression of the symbiotic plasmid from Rhizobium leguminosarum biovar trifolii in Sphingobacterium multivorum

1994 ◽  
Vol 40 (10) ◽  
pp. 873-879 ◽  
Author(s):  
M. Fenton ◽  
B. D. W. Jarvis
Keyword(s):  
Gene Transfer ◽  
White Clover ◽  
Microscopic Examination ◽  
Rhizobium Leguminosarum ◽  
Atmospheric Nitrogen ◽  
Symbiotic Genes ◽  
Symbiotic Plasmid ◽  
Spontaneous Transfer ◽  
Inoculant Strain ◽  
Rhizobium Leguminosarum Biovar Trifolii

An inoculant strain of Rhizobium leguminosarum biovar trifolii containing a Tn5 marked symbiotic plasmid transferred this plasmid by conjugation to Sphingobacterium multivorum, an organism that can be found in soil. The transconjugant bacteria nodulated the roots of white clover (Trifolium repens) seedlings but did not fix atmospheric nitrogen. Microscopic examination revealed abnormal nodule structures. Bacteria isolated from the nodules were shown to be closely related to the recipient S. multivorum and Southern blots of genomic digests probed with nodA DNA confirmed that the transconjugants contained symbiotic genes. This is the first report of the spontaneous transfer, by conjugation, of a symbiotic plasmid from R. leguminosarum biovar trifolii to S. multivorum.Key words: Rhizobium, Sphingobacterium, nodulation, nod gene transfer.

scholarly journals Homology of genes for exopolysaccharide synthesis in Rhizobium leguminosarum and effect of cloned exo genes on nodule formation.

1993 ◽  
Vol 40 (4) ◽  
pp. 477-482
Author(s):  
A Skorupska ◽  
M Deryło
Keyword(s):  
Rhizobium Leguminosarum ◽  
The Other ◽  
Nodule Formation ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Bamhi Fragment ◽  
Other Hand ◽  
Indeterminate Nodules ◽  
Total Dna ◽  
Rhizobium Sp

A 5.4 kb BamHI fragment of R. leguminosarum bv. trifolii TA1 was found to carry genes involved in exopolysaccharide synthesis (exo genes). This fragment was strongly hybridized to the total DNA from R. l. bv. viciae and bv. phaseoli digested with EcoRI. No homology was found with total DNA of R. meliloti and Rhizobium sp. NGR 234. The exo genes from R. l. bv. trifolii TA1 conjugally introduced into R. l. bv. viciae 1302 considerably affected the symbiosis: the nodules induced on vetch were abortive and did not fix nitrogen. On the other hand, Phaseolus beans infected with R. l. bv. phaseoli harbouring R. l. bv. trifolii exo genes formed the nitrogen-fixing nodules. It can be concluded that additional copies of exo genes introduced into wild type Rhizobium leguminosarum strains can disturb the synthesis of acidic exopolysaccharides and affect symbiosis of the plants forming indeterminate nodules, but do not affect symbiosis of the plants forming the determinate nodules.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

Sign in / Sign up

Export Citation Format

Share Document