Understanding Bacterial Coexistence Under Antibiotic Stress
Similä, Milla (2023-10-16)
Understanding Bacterial Coexistence Under Antibiotic Stress
(16.10.2023)
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
suljettu
Julkaisun pysyvä osoite on:
https://urn.fi/URN:NBN:fi-fe20231025141394
https://urn.fi/URN:NBN:fi-fe20231025141394
Tiivistelmä
Resolving the antibiotic resistance problem requires deep understanding of how microbial communities function. Bacteria typically occur in complex communities where multiple species coexist and interact with one another. Community composition and interactions influence how bacteria respond to antibiotic treatment. Competition for resources both within and between species regulates the fitness of both antibiotic-resistant and sensitive bacteria, which can coexist in the same environment. Ecological theory and antibiotic resistance research have largely been separated, which has slowed the process of understanding antibiotic resistance from the perspective of bacterial coexistence. Modern coexistence theory has provided a useful way to quantify the importance of competitive interactions and niche differentiation that can be applied to study the coexistence of antibiotic-resistant and sensitive bacteria.
The aim of this thesis was to understand how bacterial species coexist in complex communities using a synthetic 23-species bacterial community, and how the coexistence landscape is altered by the effect of antibiotic stress. By focusing on the two most abundant species in the community, the aim was to also quantitatively partition population dynamics of these species into competitive and niche differences and investigate how potential fitness costs incurred by antibiotic resistance relate to competitive hierarchies between the species. This was done by performing pairwise competition experiments based on the sensitivity method, which quantifies how the growth rate of a focal bacterial species changes when invading a steady state population of its competitor. Based on the outcome of the invasion, coexistence of the competing species could be predicted. Overall, limited coexistence was observed with most species pairs exhibiting priority effects, implying that the arrival order was the most important factor in terms of the competitive outcome. Antibiotic stress did not significantly contribute to the results. This highlights the need for further research since ecological theory can be a valuable tool when studying antibiotic resistance.
The aim of this thesis was to understand how bacterial species coexist in complex communities using a synthetic 23-species bacterial community, and how the coexistence landscape is altered by the effect of antibiotic stress. By focusing on the two most abundant species in the community, the aim was to also quantitatively partition population dynamics of these species into competitive and niche differences and investigate how potential fitness costs incurred by antibiotic resistance relate to competitive hierarchies between the species. This was done by performing pairwise competition experiments based on the sensitivity method, which quantifies how the growth rate of a focal bacterial species changes when invading a steady state population of its competitor. Based on the outcome of the invasion, coexistence of the competing species could be predicted. Overall, limited coexistence was observed with most species pairs exhibiting priority effects, implying that the arrival order was the most important factor in terms of the competitive outcome. Antibiotic stress did not significantly contribute to the results. This highlights the need for further research since ecological theory can be a valuable tool when studying antibiotic resistance.