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Biomedical subjects

A M Albertini

Publications and source records attributed to A M Albertini.

29 records · Page 2Linked to original sources
PubMed1982

On the formation of spontaneous deletions: the importance of short sequence homologies in the generation of large deletions.

Using lacl-Z fusion strains of Escherichia coli we have devised systems that detect deletions of varying lengths. We examined deletions 700-1000 base pairs long, and genetically characterized over 250 spontaneous deletions. Of these, we analyzed 24 by direct DNA sequencing and 18 by inspection of restriction fragment patterns. Deletions of this size occur almost exclusively at short repeated sequences in both (recA+ and recA- strain backgrounds, but are detected 25-fold more frequently in a recA+ background. The frequency of deletion formation correlates with the extent of homology between the short repeated sequences, although other factors may be involved. The largest hotspot, which accounts for 60% of the deletions detected, involves the largest homology in the system (14 of 17 base pairs). Altering a single base pair within this homology reduces deletion incidence by an order of magnitude. We discuss possible mechanisms of deletion formation and consider its relationship to the excision of transposable elements.

Base Composition↗
PubMed1982

Pattern of RNA transcription during Bacillus subtilis spore outgrowth.

During the outgrowth of Bacillus subtilis spores, there is a period of RNA and protein synthesis in the absence of DNA replication. Two mutants of B. subtilis, PB2442 (gsp-4) and PB2452 (gsp-81), were used to study the pattern of RNA synthesis during this period. The two mutants are temperature-sensitive in the outgrowth phase, and show a limited amount of incorporation of (3H)uridine at 47 degrees C. The RNAs synthesized during a 2 min pulse with (3H)uridine were hybridized to EcoRI-digested DNA, after agarose gel electrophoresis and transfer to nitrocellulose paper (Southern technique). For both mutants the transcripts synthesized at 35 degrees C at different times were different. Differences were also observed in the transcripts made at 47 degrees C. For both mutants, in the presence of chloramphenicol, the same hybridization pattern was obtained for RNAs pulse-labelled at different periods during outgrowth.

Bacillus subtilis↗
PubMed1981

Integration and excision of a plasmid in Bacillus subtilis.

We have studied the behaviour in Bacillus subtilis of a plasmid (pPV21) carrying the thymidylate synthetase gene of phage phi3T (thyP3). The plasmid can transform efficiently the competent cells of all the strains tested. Polyethylene glycol (PEG)-mediated protoplast transformation is efficient only for recE, recD or recF mutants. When present in recombination proficient strains, the plasmid can be integrated into the chromosome, primarily at the thyA locus. This has been shown by genetic mapping and by blot-hybridization. A second less efficient site is at (or near to) the attachment site of phage phi3T. Excision of the plasmid restores the EcoRI restriction pattern of the parental DNA, although with the loss of the defective thyA endogenotic allele and the retention of the thyP exogenotic gene.

Bacillus subtilis↗
PubMed1979

Mutants of Bacillus subtilis affected in spore outgrowth.

Six mutants of Bacillus subtilis 168 that are temperature-sensitive in spore outgrowth were isolated. The outgrowth process proceeds normally at 35 degrees C, but at the non-permissive temperature (47 degrees C) it is arrested at a specific stage characteristic for each mutant strain. The mutants are not altered in vegetative growth whether at 35 degrees C or at 47 degrees C. They were characterized for their ability to synthesize RNA, proteins and DNA during outgrowth. A mutant defective in spore germination was also isolated; less than 5% of its spores can germinate at any of the temperatures tested. The mutations were mapped by means of transduction and transformation. The isolation of a number of outgrowth mutants which map at different loci and which affect outgrowth at different times is discussed in relation to the regulation of this process.

Bacillus subtilis↗
PubMed1977

RNA polymerase from Bacillus subtilis: isolation of core and holo enzyme by DNA-cellulose chromatography.

A new procedure for the purification of B. subtilis RNA polymerase, based on mild lysis of cells, low speed centrifugation, gel filtration, DEAE-Sephadex chromatography and affinity chromatography on DNA-cellulose, yields three forms of enzyme referred here as enzyme A, B and C. As revealed by SDS gel electrophoresis, enzyme A has the subunit structure of core polymerase plus some small polypeptides. Its catalytic properties are similar to those of core polymerase. Enzyme B has the composition of core polymerase. Both enzymes A and B can be stimulated by the addition of beta factor. Enzyme C has the holo-enzyme composition. The pattern of sensitivity of the three forms of enzyme towards KCl are very different: enzymes A and B, even at low concentration of salt, are inhibited with all the DNA templates tested, whereas enzyme C shows a pattern of stimulation specific for each DNA tested. The transcripts of the three enzymes on phage SPP1 DNA template have been analyzed by hybridization to the separated strands. Only enzyme C selectively transcribed the H strands.

Bacillus subtilis↗
PubMed1976

Synthesis of RNA and protein in a mutant of Bacillus subtilis temperature sensitive during spore germination.

Bacillus subtilis strain PB 2427 temperature sensitive in the synthesis of RNA during spore germination and outgrowth has been characterized to some extent. At non permissive temperature (46 degrees C) strain PB 2427 synthesizes stable and unstable RNA for 50 min from the beginning of germination and then stops. Most of the stable RNA is degraded to shorter molecules but can be identified as ribosomal RNA by hybridization-competition experiments. At non permissive temperature, in the presence of chloramphenicol, synthesis of RNA proceeds, though at a reduced rate, for at least 90 min. By hybridization-competition experiments it can also be shown that the RNA synthesized at 46 degrees C in the presence of chloramphenicol includes transcripts that are absent, from the RNA synthesized at 46 degrees C in the absence of drug. The RNA polymerase (holo and core) purified from vegatative cells of the mutant strain does not appear to have a greater heat-lability as compared with the enzyme purified from the parental strain. At non permissive temperature only six polypeptide chains with MW ranging from 47,000 to 78,000 daltons are synthesized by the germinating spores of the mutant.

Bacillus subtilis↗
PubMed1975

Synchronous germination and outgrowth of fractionated Bacillus subtilis spores: tool for the analysis of differentiation and division of bacterial cells.

A fraction of Bacillus subtilis 168 spores, purified by Urografin isopycnic density centrifugation, heat activated, and inoculated in nutrient broth plus glucose, germinated and outgrew very synchronously. Synchrony was documented by nuclear staining and fluorescence microscopy, and by determining the variation of the buoyant density of the cells during outgrowth. Cell mass increased at constant rates and the passage from one rate to the next was dependent upon deoxyribonucleic acid (DNA) synthesis. DNA synthesis inhibitors induced the formation of anucleated sister cells in a vast majority of the population, indicating that septation was programmed and became independent from DNA synthesis very early in the cell cycle.

Azo Compounds↗
PubMed1975

Properties of Bacillus subtilis mutants temperature sensitive in germination.

A new mutant of Bacillus subtilis defective in the outgrowth phase of spore germination has been isolated. When incubated at 46 C, the spores of the mutant gave rise to abnormally large swollen cells. Genetic crosses show that the mutant is different from the three previously described. The genetic analysis indicates two regions of the B. subtilis chromosome involved in the control of the spore outgrowth.

Bacillus subtilis↗
PubMed1975

Mutant of Bacillus subtilis with a temperature-sensitive lesion in ribonucleic acid synthesis during germination.

We have isolated a mutant of Baccillus subtilis with a temperature-sensitive lesion in the process of spore germination. The temperature-sensitive mutation affects only germination and outgrowth, and the earliest defect observed is an early block of ribonucleic acid synthesis during germination at 46 C. Upon return to 35 C there is a complete repair of the impaired function, even in the absence of protein synthesis. Protein synthesis inhibition during germination of the mutant spores at 46 C has the effect of increasing the amount of ribonucleic acid made. The temperature-sensitive mutation is located near aroI.

Bacillus subtilis↗