---
OA_place: publisher
_id: '23220'
abstract:
- lang: eng
  text: "Bacterial adaptation depends not only on the selective environment but also
    on the genetic background that determines which variants can arise and how they
    affect fitness. This thesis investigates how genetic background affects bacterial
    adaptive capacity by experimentally examining the effect of insertion sequence
    (IS) activity and establishing a strain system for future experiments to reveal
    the role of natural competence.\r\n\r\nThe main experimental study compared Escherichia
    coli MG1655 with a derivative lacking all 45 chromosomal IS elements, together
    with additional strains designed to separate the effects of IS removal from restoration
    of the IS-disrupted gene wbbL. Replicate populations were adapted to increasing
    concentrations of a five-antibiotic mixture and to each antibiotic individually,
    and their adaptive responses and evolutionary routes were compared. Under mixture
    selection, IS-containing and IS-free populations reached similar endpoint resistance
    and acquired similar numbers of mutations, although their mutation spectra differed
    significantly. IS-driven mutations were rare, indicating that IS activity contributed
    little to adaptation under this condition. Adaptation to individual antibiotics
    produced larger treatment-specific resistance gains and more recurrent mutations
    in the same loci across independently evolved populations than adaptation to the
    antibiotic mixture. The contribution of IS-driven mutations varied among antibiotics
    and was highest under tetracycline selection. Under tetracycline treatment, IS-containing
    populations adapted faster and reached higher selection concentrations than IS-free
    populations. Inactivation of wbbL partially restored the adaptive capacity of
    the IS-free strain but did not fully eliminate the difference, while IS-containing
    populations repeatedly accessed IS-mediated mutations unavailable to the IS-free
    strains.\r\n\r\nEarlier experiments examining adaptation to ethanol, sodium chloride,
    and butanol did not provide reliable evidence for differences between the IS backgrounds.
    Growth observed at high sodium chloride and butanol concentrations during selection
    was not retained after stress-free recovery, whereas turbidostat-based ethanol
    experiments revealed technical limitations of using the device for parallel long-term
    evolution. These results motivated the more robust antibiotic-selection design.
    Finally, an experimental framework was developed to test whether natural competence
    contributes to the adaptive capacity of Bacillus subtilis. As a first step toward
    the proposed experiments, a genotypically verified ΔcomEC strain and characterized
    fluorescent strains were constructed, but the evolution experiments remain to
    be initiated.\r\n\r\nTogether, these results show that IS elements can expand
    the repertoire of accessible mutations without conferring a universal adaptive
    advantage. Whether IS activity improves adaptation depends on the selective environment,
    the wider genetic background, and whether IS-mediated mutations provide particularly
    beneficial adaptive routes."
acknowledged_ssus:
- _id: LifeSc
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Stepan
  full_name: Ovchinnikov, Stepan
  id: f0890ac0-dc8d-11ea-abe3-91bc19153eb6
  last_name: Ovchinnikov
citation:
  ama: Ovchinnikov S. The role of genetic background in bacterial adaptation. 2026.
    doi:<a href="https://doi.org/10.15479/AT-ISTA-23220">10.15479/AT-ISTA-23220</a>
  apa: Ovchinnikov, S. (2026). <i>The role of genetic background in bacterial adaptation</i>.
    Institute of Science and Technology Austria. <a href="https://doi.org/10.15479/AT-ISTA-23220">https://doi.org/10.15479/AT-ISTA-23220</a>
  chicago: Ovchinnikov, Stepan. “The Role of Genetic Background in Bacterial Adaptation.”
    Institute of Science and Technology Austria, 2026. <a href="https://doi.org/10.15479/AT-ISTA-23220">https://doi.org/10.15479/AT-ISTA-23220</a>.
  ieee: S. Ovchinnikov, “The role of genetic background in bacterial adaptation,”
    Institute of Science and Technology Austria, 2026.
  ista: Ovchinnikov S. 2026. The role of genetic background in bacterial adaptation.
    Institute of Science and Technology Austria.
  mla: Ovchinnikov, Stepan. <i>The Role of Genetic Background in Bacterial Adaptation</i>.
    Institute of Science and Technology Austria, 2026, doi:<a href="https://doi.org/10.15479/AT-ISTA-23220">10.15479/AT-ISTA-23220</a>.
  short: S. Ovchinnikov, The Role of Genetic Background in Bacterial Adaptation, Institute
    of Science and Technology Austria, 2026.
corr_author: '1'
date_created: 2026-11-04T16:56:52Z
date_published: 2026-11-01T00:00:00Z
date_updated: 2026-11-13T14:14:35Z
day: '01'
ddc:
- '576'
degree_awarded: PhD
department:
- _id: GradSch
- _id: CaGu
- _id: NiBa
doi: 10.15479/AT-ISTA-23220
doi_confirm: '1'
file:
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  creator: sovchinn
  date_created: 2026-11-04T16:41:28Z
  date_updated: 2026-11-09T11:40:38Z
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fulldoi: https://doi.org/10.15479/AT-ISTA-23220
has_accepted_license: '1'
language:
- iso: eng
license: https://creativecommons.org/licenses/by-nc-sa/4.0/
month: '11'
oa: 1
oa_version: Published Version
page: '63'
publication_identifier:
  issn:
  - 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
status: public
supervisor:
- first_name: Calin C
  full_name: Guet, Calin C
  id: 47F8433E-F248-11E8-B48F-1D18A9856A87
  last_name: Guet
  orcid: 0000-0001-6220-2052
- first_name: Nicholas H
  full_name: Barton, Nicholas H
  id: 4880FE40-F248-11E8-B48F-1D18A9856A87
  last_name: Barton
  orcid: 0000-0002-8548-5240
title: The role of genetic background in bacterial adaptation
tmp:
  image: /images/cc_by_nc_sa.png
  legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode
  name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC
    BY-NC-SA 4.0)
  short: CC BY-NC-SA (4.0)
type: dissertation
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2026'
...