Electrotransformation of industrial strains of Streptococcus thermophilus

A standard electroporation procedure was utilized to introduce a range of Gram‐positive plasmid vectors into nine industrial strains of Streptococcus thermophilus. All the strains were transformable with at least two of the plasmids assessed, but electrotransformation frequencies depended on both th...

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Bibliographic Details
Published in:Journal of applied microbiology 1999-02, Vol.86 (2), p.275-283
Main Authors: O’sullivan, T. F., Fitzgerald, G. F.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biotechnology
Electroporation - methods
Endopeptidases - genetics
Endopeptidases - metabolism
Fundamental and applied biological sciences. Psychology
Gene transfer
Genetic engineering
Genetic technics
Methods. Procedures. Technologies
Plasmids - genetics
Polymerase Chain Reaction - methods
Streptococcus - enzymology
Streptococcus - genetics
Streptococcus - growth & development
Streptococcus thermophilus
Synthetic digonucleotides and genes. Sequencing
Transformation, Bacterial
Yogurt - microbiology
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Summary:A standard electroporation procedure was utilized to introduce a range of Gram‐positive plasmid vectors into nine industrial strains of Streptococcus thermophilus. All the strains were transformable with at least two of the plasmids assessed, but electrotransformation frequencies depended on both the strain and the nature of transforming DNA. In general, small rolling circle (RC) plasmids could be electroporated at high frequency into a wide range of strains with efficiencies of 102–105 transformants μg−1 of transforming DNA. The presence of these plasmids did not influence doubling times during growth in broth, and they were generally extremely stable in slow milk acidifying strains, with 85–100% of transformants retaining the selective markers over 105 generations. Vectors were less stable in fast‐growing cultures. Of the three theta‐type plasmids assessed, only one, pIL253, could be electroporated at low frequency into some slow growing strains. The presence of this plasmid caused a 40% increase in doubling time and it was lost from cells at a rate of 3% per generation. Attempts to alter the proteolytic status of slow acidifying strains of Strep. thermophilus by the introduction of heterologous proteinase genes are also described.
ISSN:1364-5072
1365-2672
DOI:10.1046/j.1365-2672.1999.00657.x