Biological amplification of low frequency mutations unravels laboratory culture history of the bio-threat agent Francisella tularensis

Challenges of investigating a suspected bio attack include establishing if microorganisms have been cultured to produce attack material and to identify their source. Key aims were to identify genetic variations that are characteristic of laboratory culturing and explore the possibility of using biological amplification to identify genetic variation present at exceedingly low frequencies in a source sample. The F. tularensis subsp. tularensis FSC237-clpB strain, deficient in expression of the heat shock protein ClpB was used for the laboratory passage experiments.