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- Zorzet, Anna, 1977-, et al.
(author)
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Compensatory evolution restores fitness to actinonin-resistant Staphylococcus aureus
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Other publication (other academic/artistic)abstract
- We have studied the emergence of actinonin-resistant mutants in S. aureus. In accordance with earlier studies we identified resistance mutations in the fmt gene that apart from conferring high-level resistance also reduced the growth rate. To study how fitness could be restored we performed compensatory evolution by serial passage of cells in liquid culture. Compensated mutants arose quickly, within 40 generations and sometimes in less than 10 generations. The mutants were fully resistant to actinonin and showed increased growth rates on plates. However, exponential growth rates in liquid media were not higher than for the parental resistant mutants. We sequenced the whole genomes of one slow-growing strain and three compensated and found alterations in three genes. These genes were SAOUHSC_01699 coding for shikimate 5-dehydrogenase, SAOUHSC_00945 coding for a magnesium transporter and SAOUHSC_02264, coding for accessory gene regulator protein C (AgrC). None of these mutants were obvious candidates for compensating lack of formylation. When sequencing these three loci in the remainder of the compensated strains, mutations in agrC were found in 11 of 16 strains. Further studies will show if these mutations are due to general environmental adaption, specific adaptation for slow growth or specific compensation for loss of formylation.
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