Related Experiment Video
Updated: Aug 14, 2026
Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43
Published on: September 11, 2020
Construction of Streptococcus lactis subsp. lactis Strains with a Single Plasmid Associated with Mucoid Phenotype
1Research and Development Department, Valio Finnish Co-operative Dairies' Association, SF-00181 Helsinki 18, Finland.
Abstract:
Lactose-fermenting mucoid (Lac Muc) variants of plasmid-free Streptococcus lactis subsp. lactis MG1614 were obtained by protoplast transformation with total plasmid DNA from MucS. lactis subsp. cremoris ARH87. By using plasmid DNA from these variants for further transformations followed by novobiocininduced plasmid curing, Lac Muc MG1614 strains containing only a single 30-megadalton plasmid could be constructed. This plasmid, designated pVS5, appeared to be associated with the Muc phenotype.
Insights
Researchers created lactose-fermenting mucoid (Lac Muc) Streptococcus lactis strains. A single 30-megadalton plasmid, pVS5, was identified and associated with the mucoid phenotype in these novel bacterial strains.
Area of Science:
- Microbiology
- Bacteriology
- Molecular Biology
Background:
- Streptococcus lactis subsp. cremoris ARH87 exhibits a mucoid (Muc) phenotype.
- Plasmid DNA is known to influence bacterial characteristics.
- Plasmid-free Streptococcus lactis subsp. lactis MG1614 serves as a model for genetic modification.
Purpose of the Study:
- To investigate the genetic basis of the mucoid phenotype in Streptococcus lactis.
- To construct and characterize novel lactose-fermenting mucoid (Lac Muc) variants of Streptococcus lactis subsp. lactis MG1614.
- To identify specific plasmids associated with the mucoid trait.
Main Methods:
- Protoplast transformation using total plasmid DNA from MucS. lactis subsp. cremoris ARH87.
- Subsequent transformations with plasmid DNA from engineered variants.
- Novobiocin-induced plasmid curing to isolate single-plasmid strains.
Main Results:
- Successfully generated lactose-fermenting mucoid (Lac Muc) variants of Streptococcus lactis subsp. lactis MG1614.
- Constructed strains harboring a single 30-megadalton plasmid through serial transformations and plasmid curing.
- Identified this 30-megadalton plasmid, designated pVS5, as being associated with the mucoid phenotype.
Conclusions:
- The mucoid (Muc) phenotype in Streptococcus lactis is plasmid-associated.
- A specific 30-megadalton plasmid, pVS5, is linked to the mucoid characteristic.
- This study provides a method for isolating and characterizing plasmids responsible for specific bacterial traits.
