The formation of Hfr strains inEscherichia coliK12

The isolation and characterization of an isogenic series of twelve Hfr strains is described. From their points of origin it was concluded that the sex factor integrates at a limited number of sites on the bacterial chromosome. Although the nutritional requirements of these Hfr strains were similar to those of the parent F+strain, it was observed that one group had a markedly slower growth rate. The relevance of these observations to theories on the nature of F+fertility and on the formation of Hfr strains is discussed.

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SELECTION AND ENDPOINT DISTRIBUTION OF BACTERIAL INVERSION MUTATIONS

Genetics ◽

10.1093/genetics/105.3.539 ◽

1983 ◽

Vol 105 (3) ◽

pp. 539-557

Author(s):

Molly B Schmid ◽

John R Roth

Keyword(s):

Dna Replication ◽

Salmonella Typhimurium ◽

Chromosome Rearrangements ◽

Bacterial Chromosome ◽

Inverted Region ◽

Isolation And Characterization

ABSTRACT This paper describes the isolation and characterization of spontaneous inversion mutants of Salmonella typhimurium. The mutants are selected by demanding that an unexpressed hisD gene acquire a new promoter. Chromosome rearrangements that juxtapose the hisD gene and a foreign promoter are obtained by this selection. Although a number of inversions are found, the frequency was lower than expected. The breakpoints of these inversions are not distributed randomly either in the his operon or on the chromosome. The his breakpoint lies in the hisG-hisD intercistronic region, a sequence known to occur at several places on the bacterial chromosome. In most of the inversions, the "non-his" breakpoint lies across the chromosome, so that the inverted region includes the origin or terminus of DNA replication. The significance of these results is discussed.

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Isolation and Characterization of a New Arthrospira Strain

Zeitschrift für Naturforschung C ◽

10.1515/znc-2008-1-226 ◽

2008 ◽

Vol 63 (1-2) ◽

pp. 144-150 ◽

Cited By ~ 52

Author(s):

Michele Greque de Morais ◽

Carolina da Cruz Reichert ◽

Francieli Dalcanton ◽

Andrei José Durante ◽

Luís Fernando Marins ◽

...

Keyword(s):

Growth Rate ◽

Specific Growth Rate ◽

Specific Growth ◽

Rapd Analysis ◽

Random Amplified Polymorphic Dna ◽

Arthrospira Platensis ◽

Central Point ◽

Filamentous Microorganism ◽

Isolation And Characterization

A filamentous microorganism, morphologically similar to the cyanobacterium Arthrospira, was isolated from Mangueira Lagoon in Brazil, from which Arthrospira has not previously been isolated. Random amplified polymorphic DNA (RAPD) comparison with the standard Arthrospira platensis strains LEB 52 and Paracas indicated that the organism isolated was an Arthrospira isolate, which we denominated strain LEB 18. The RAPD analysis showed conserved sequences which indicated that the three strains belonged to the same genus, and were all Arthrospira species, but there were sufficient differences between them suggesting that they were separate strains. The strain LEB 18 was cultivated in undiluted Zarrouk medium and in 60% and 20% (v/v) Zarrouk medium diluted with sterilized Mangueira Lagoon water (MLW) using illuminance rates of 32.5, 45.5 and 58.5 μmol m−2 s−1 according to a complete 32 factorial design with a triplicate central point. The strains LEB 52 and Paracas were cultived in the conditions central point. Our new isolate produced the highest specific growth rate (μmax = 0.22 d−1) in 60% Zarrouk medium diluted with MLW and illuminated with 58.5 μmol m−2 s−1 and the highest protein content (86.0% w/w).

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Isolation and characterization of a starchless mutant of Chlorella pyrenoidosa STL-PI with a high growth rate, and high protein and polyunsaturated fatty acid content

Phycological Research ◽

10.1111/j.1440-1835.2006.00416.x ◽

2006 ◽

Vol 54 (4) ◽

pp. 255-259 ◽

Cited By ~ 75

Author(s):

Arthur Ramazanov ◽

Zakir Ramazanov

Keyword(s):

Growth Rate ◽

Fatty Acid ◽

Fatty Acid Content ◽

High Growth ◽

Chlorella Pyrenoidosa ◽

High Growth Rate ◽

Polyunsaturated Fatty Acid Content ◽

Isolation And Characterization ◽

Starchless Mutant

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Isolation and characterization of IS elements repeated in the bacterial chromosome

Journal of Molecular Biology ◽

10.1016/0022-2836(87)90023-4 ◽

1987 ◽

Vol 196 (3) ◽

pp. 445-455 ◽

Cited By ~ 55

Author(s):

Sachiko Matsutani ◽

Hisako Ohtsubo ◽

Yoshimi Maeda ◽

Eiichi Ohtsubo

Keyword(s):

Bacterial Chromosome ◽

Is Elements ◽

Isolation And Characterization

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Isolation and characterization of highly thermophilic xylanolyticThermus thermophilusstrains from hot composts

Canadian Journal of Microbiology ◽

10.1139/w00-075 ◽

2000 ◽

Vol 46 (11) ◽

pp. 1029-1035 ◽

Cited By ~ 11

Author(s):

Pierre-François Lyon ◽

Trello Beffa ◽

Michel Blanc ◽

Georg Auling ◽

Michel Aragno

Keyword(s):

Growth Rate ◽

Culture Medium ◽

Xylanase Activity ◽

Thermostable Enzyme ◽

Aerobic Bacteria ◽

Maximal Growth ◽

Detailed Report ◽

Xylanolytic Activity ◽

Isolation And Characterization

This is the first detailed report of xylanolytic activity in Thermus strains. Two highly thermophilic xylanolytic bacteria, very closely related to non-xylanolytic T. thermophilus strains, have been isolated from the hottest zones of compost piles. Strain X6 was investigated in more detail. The growth rate (optical density monitoring) on xylan was 0.404·h-1at 75°C. Maximal growth temperature was 81°C. Xylanase activity was mainly cell-bound, but was solubilized into the medium by sonication. It was induced by xylan or xylose in the culture medium. The temperature and pH optima of the xylanases were determined to be around 100°C and pH 6, respectively. Xylanase activity was fairly thermostable; only 39% of activity was lost after an incubation period of 48 h at 90°C in the absence of substrate. Xylanolytic T. thermophilus strains could contribute to the degradation of hemicellulose during the thermogenic phase of industrial composting.Key words: Thermus, thermophilic aerobic bacteria, xylanase, thermostable enzyme, compost.

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ISOLATION AND CHARACTERIZATION OF PERITHECIAL DEVELOPMENT MUTANTS IN NEUROSPORA

Genetics ◽

10.1093/genetics/88.1.27 ◽

1978 ◽

Vol 88 (1) ◽

pp. 27-47

Author(s):

Thomas E Johnson

Keyword(s):

Growth Rate ◽

Mating Type ◽

Temperature Sensitive ◽

Uv Mutagenesis ◽

Lower Growth ◽

Type Locus ◽

Isolation And Characterization ◽

Lower Growth Rate ◽

Complementation Groups

ABSTRACT The isolation and characterization of mutants that block perithecial development in Neurospora crassa are described. Several classes of mutants have been isolated after UV mutagenesis, and those that block perithecial development when used as the female (protoperithecial) component of a cross have been further characterized. These mutants fall into 29 complementation groups. Twelve of the 33 mutants block development at the protoperithecial stage; no other clustering of block points is observed. Many of the mutants show an altered vegetative growth rate as well; in several mutants this lower growth rate cosegregates with the female sterile phenotype. Only one mutant also blocks development of the perithecium when used as the conidial parent. None of the mutants are temperature sensitive; two can be suppressed by growth on a complete crossing medium. There is no indication that the mutants are at or in the mating-type locus, nor are any of the mutants mating-type specific. Genetic mosaics have been formed using mixtures of mutant and marked wild-type nuclei; no mutants are cell autonomous by this criterion. The significance of these results in terms of "developmental" mutants isolated in other organisms and in relation to models of eukaryotic development is discussed.

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