Plasmid-associated aggregation in Thermus thermophilus HB8

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Thermus thermophilus HB8, a moderate thermophile, displays visible cell aggregation in rich broth.
• This strain harbors two cryptic plasmids, whose functions are largely unknown.
• Plasmid-associated phenotypes are not well-documented in Thermus species.

Purpose of the Study:

• To investigate the genetic basis of cell aggregation in Thermus thermophilus HB8.
• To determine the role of plasmids in the aggregation phenotype.
• To characterize the stability and inheritance of the aggregation phenotype.

Main Methods:

• Isolation of plasmid-cured strains from Thermus thermophilus HB8.
• Development of an enrichment procedure for aggregating cells.
• Transformation of cured strains with plasmid DNA.
• Plasmid DNA hybridization experiments.

Main Results:

• Loss of the 47-MDa plasmid correlated with the loss of cell aggregation.
• Aggregation was restored in cured strains upon transformation with plasmid DNA.
• The aggregation phenotype and plasmid were not stably maintained during prolonged growth.
• Hybridization suggested a repeated DNA sequence on the plasmid and chromosome.

Conclusions:

• The 47-MDa plasmid is responsible for the aggregation phenotype in Thermus thermophilus HB8.
• This is the first reported instance of a plasmid-linked phenotype in a Thermus strain.
• Further research is needed to understand the stability and genetic basis of this plasmid-mediated aggregation.