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Biomedical subjects

S D Ehrlich

Publications and source records attributed to S D Ehrlich.

At least 217 records · Page 12Linked to original sources
PubMed1980

Replication of plasmids from Staphylococcus aureus in Escherichia coli.

Plasmid pBR322 derives from plasmid ColE1 and does not replicate in Escherichia coli strains lacking DNA polymerase I. Hybrids between pBR322 and a plasmid isolated from Staphylococcus aureus, pC194, replicate in such E. coli strains, provided that the pC194 replication region is intact. Inactivation of the pBR322 replication region does not interfere with the replication of hybrids in E. coli. Hybrids between pBR322 and two other plasmids from S. aureus, pT127 and pUB112, and replicate at the restrictive temperature in E. coli having thermosensitive DNA polymerase I. Similar hybrids involving pC221 and pHV400, plasmids from S. aureus and Bacillus subtilis, respectively, do not replicate under such conditions. These results show that some plasmids from a Gram-positive bacterium, S. aureus, can replicate in a Gram-negative one, E. coli.

Base Sequence↗
PubMed1978

Use of the T4 polynucleotide ligase in the joining of flush-ended DNA segments generated by restriction endonucleases.

Double-stranded DNA segments with completely base-paired ends were obtained by the action of various restriction endonucleases on phage and plasmid DNAs. These segments were joined covalently by the T4 polynucleotide ligase. The joining was monitored by the electron microscopy count of intramolecularly circularized segments. The highest extent of joining, close to 75%, was observed at 15-25 degrees C with the segments resulting from the action of the Bacillus subtilis (strain R) restriction endonuclease Bsu on the DNA of bacteriophage SPPI or of the plasmid pSC 101. The joining of double-stranded termini required about 10 times more enzyme than the short single-stranded termini produced by the Escherichia coli restriction endonuclease EcoRI. A shortened purification of the T4 ligase was found to give an enzyme devoid of interfacing nucleases.

Coliphages↗
PubMed1978

DNA cloning in Bacillus subtilis.

A plasmid pC194, encoding resistance to chloramphenicol, can serve as a cloning vector in Bacillus subtilis 168 for other HindIII-cleaved DNA segments. Replicons constructed by linking pC194 to several Escherichia coli plasmids can be used to introduce and compare the expression of the same genes in these two bacterial hosts.

Bacillus subtilis↗
PubMed1978

Functional expression of two Bacillus subtilis chromosomal genes in Escherichia coli.

EcoRI-cleaved deoxyribonucleic acid segments carrying two genes from Bacillus subtilis, pyr and leu, have been cloned in Escherichia coli by insertion into a derivative of the E. coli bacteriophage lambda. Lysogenization of pyrimidine- and leucine-requiring auxotrophs of E. coli by the hybrid phages exhibited prototrophic phenotypes, suggesting the expression of B. subtilis genes in E. coli. Upon induction, these lysogens produced lysates capable of transducing E. coli pyr and leu auxotrophs to prototrophy with high frequency. Isolated DNAs of these bacteriophages have the ability to transform B. subtilis auxotrophs to pyr and leu independence and contain EcoRI-cleaved segments which hybridize to corresponding segments of B. subtilis.

Bacillus subtilis↗
PubMed1977

Replication and expression of plasmids from Staphylococcus aureus in Bacillus subtilis.

One S. aureus plasmid coding for tetracycline resistance, pT127, and four plasmids (pC194, pC221, pC223, and pUB112) coding for chloramphenicol resistance have been introduced by transformation into B, subtilis. The plasmids replicate in--and confer antibiotic resistance upon--their new host. These experiments show that the potential for genetic exchange between diverse bacterial species is greater than has been commonly assumed.

Bacillus subtilis↗
PubMed1976

Expression of the thymidylate synthetase gene of the Bacillus subtilis bacteriophage Phi-3-T in Escherichia coli.

The thymidylate synthetase gene of B. subtilis bacteriophage Phi-3-T, when cloned in plasmids pSC101 or pMB9 is expressed in E. coli. The promoter of the cloned gene is likely to originate in Phi-3-T. Rearrangements of hybrid plasmid sequences during the cloning have been noted. B. subtilis strains can be transformed with hybrid DNAs. The transformants contain sequences of Phi-3-T, but not those of plasmid vectors.

Bacillus subtilis↗
PubMed1975

Electrophoretic separation of Bacillus subtilis genes.

The cleavage of Bacillus subtilis DNA by EcoR1 restriction endonuclease produced segments which retain various degrees of genetic transforming activity. The active segments analyzed thus far, range in size from 23 to 3 kilobases and can be partially separated by agarose gel electrophoresis. Various markers can thus be enriched from 30- to 60-fold.

Bacillus subtilis↗
PubMed1974

A new approach to the study of nucleotide sequences in DNAs.

The composition of the 3'terminal, 5'terminal and 5'penultimate nucleotides of the oligonucleotides released by spleen acid DNase and snail acid DNase from five ;repetitive' DNAs (guinea pig, mouse and crab satellite DNAs, yeast mitochondrial DNA and poly (dAT:dAT)) and four ;eukaryotic' DNAs (calf thymus, guinea pig and mouse liver DNAs, and yeast nuclear DNA) have been investigated and found to deviate in characteristic ways from those expected for bacterial DNAs having comparable base compositions. The deviation patterns obtained represent a novel way of characterizing and comparing different DNAs on the basis of the frequency of the nucleotide sequences they contain.

Animals↗