LSTM Seminar Series: Streptococcus pneumoniae - life with peroxide, sex and death

Event 11 Jan 2015

Professor Christopher Dowson
The Infectious Disease Research Group 
University of Warwick


Asymptomatic pneumococcal carriage is accompanied by the variable (strain to strain) production of between 0.2-2mM hydrogen peroxide as part of its fermentative, aerobic metabolism. The consequences  of this range from killing nasopharyngeal competitors  to  biochemical and chromosomal self harm. Without a classic SOS repair system and the need to deal with (now quite apparently common) peroxide driven chromosomal deletions, pneumococci have to rely upon  their natural transformability and ability to integrate  overarching segments of DNA to patch up these lesions by homologous recombination at the lesion junctions. The consequences of all this are interesting as recent genome analysis of globally and locally sampled pneumococcal clones has shed light on previously unmeasurable rates of self v non-self transformation, the frequency of acquiring your siblings' v more distant relatives genes to repair the deletions, and this may explain the rather bipolar nature of pneumococcal chromosomal diversity, which simultaneously displays unusually highly conserved  ‘house-keeping’ genes and regions ( most visibly those under an obvious strong selective pressure) which are  highly diverse, such as those  encoding penicillin resistance.  

An account stretching through decades with recent fact, hypotheses and speculation.