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

Publication date: Available online 19 December 2019Source: Forensic Science International: GeneticsAuthor(s): Chinmay Dwibedi, Pär Larsson, Jon Ahlinder, Petter Lindgren, Kerstin Myrtennäs, Malin Granberg, Eva Lundmark, Caroline Öhrman, Andreas Sjodin, Per Stenberg, Mats Forsman, Anders JohanssonAbstractChallenges of investigating a suspected bio attack include establishing if microorganisms have been cultured to produce attack material and to identify their source. Addressing both issues, we have investigated genetic variations that emerge during laboratory culturing of the bacterial pathogen Francisella tularensis. 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. We used parallel serial passage experiments and high-throughput sequencing of F. tularensis to explore the genetic variation. We found that during early laboratory culture passages of F. tularensis, gene duplications emerged in the pathogen genome followed by single-nucleotide polymorphisms in genes for bacterial capsule synthesis. Based on a biological enrichment scheme and the use of high-throughput sequencing, we identified genetic variation that likely pre-existed in a source sample. The results support that capsule synthesis gene mutations are common during laboratory culture, and that a biological amplification str...
Source: Forensic Science International: Genetics - Category: Forensic Medicine Source Type: research