Defence and response during bacterial warfare
<p>At the heart of most microbial communities lie competitive interactions. These interactions are often mediated by a wide array of dedicated weapons that bacteria use to kill and inhibit competitors. In response, bacteria have therefore had to evolve ways to cope with these attacks. However,...
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| Format: | Thesis |
| Language: | English |
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2021
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| _version_ | 1826315821331251200 |
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| author | Meiller-Legrand, TA |
| author2 | Foster, K |
| author_facet | Foster, K Meiller-Legrand, TA |
| author_sort | Meiller-Legrand, TA |
| collection | OXFORD |
| description | <p>At the heart of most microbial communities lie competitive interactions. These interactions are often mediated by a wide array of dedicated weapons that bacteria use to kill and inhibit competitors. In response, bacteria have therefore had to evolve ways to cope with these attacks. However, our understanding of how bacteria deal with such stresses is largely confined to the effects of clinical antibiotics. Here we argue that there is need for a dedicated focus on how bacteria respond and defend themselves against other bacterial competitors. In this thesis, we use lab-based experiments and agent-based modelling to investigate two different ways bacteria respond to assaults from competitors, filamentation and biofilm formation.</p>
<p>Under stress, many bacterial cells will elongate without dividing to generate long filaments. We found that DNase colicins, narrow-spectrum toxins of E. coli, trigger dramatic filamentation in susceptible conspecifics, which is associated with cells actively pushing themselves out from microcolonies. We explored whether this behaviour could be a strategy for escaping from toxins by deleting the gene reported to control filamentation. However, this locus and several others tested, failed to prevent inhibition meaning that tests of a dispersal benefit were inconclusive. However, with a second toxin that induces filamentation --- the drug mitomycin C --- I found evidence that filamentation does indeed provide a strong benefit by allowing cells to disperse better from growing colonies.</p>
<p>A second widespread response to toxins is for bacteria to increase biofilm formation. We explored the potential benefit of this response in competition with other bacteria using agent-based modelling. We found that making a thicker biofilm is a good way to compete even without the effects of toxins, because of the well-known benefits of reaching nutrients first. Moreover, when toxin competition occurs, we found that thick biofilms can serve to mop up toxins and help defend a strain against incoming attacks. Overall, the biofilm response can be clearly rationalised in the context of interbacterial warfare.</p>
<p>Finally, we present a review of the ecology and evolution of bacterial warfare, which includes an extensive survey of currently known bacterial weapons, and how and when they are used.</p>
<p>My thesis stresses the importance of toxin-mediated warfare for shaping the ecology and evolution of bacteria. But there is still much to learn about bacterial defences, and we argue that greater understanding will be needed if we are to effectively control bacterial communities for our own ends.</p> |
| first_indexed | 2024-03-07T07:40:27Z |
| format | Thesis |
| id | oxford-uuid:1c6c84c8-8bdc-40e1-812b-0cda421b3694 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:33:13Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | oxford-uuid:1c6c84c8-8bdc-40e1-812b-0cda421b36942024-12-01T16:23:48ZDefence and response during bacterial warfareThesishttp://purl.org/coar/resource_type/c_db06uuid:1c6c84c8-8bdc-40e1-812b-0cda421b3694Competition (Biology)MicrobiologyEnglishHyrax Deposit2021Meiller-Legrand, TAFoster, KSmith, W<p>At the heart of most microbial communities lie competitive interactions. These interactions are often mediated by a wide array of dedicated weapons that bacteria use to kill and inhibit competitors. In response, bacteria have therefore had to evolve ways to cope with these attacks. However, our understanding of how bacteria deal with such stresses is largely confined to the effects of clinical antibiotics. Here we argue that there is need for a dedicated focus on how bacteria respond and defend themselves against other bacterial competitors. In this thesis, we use lab-based experiments and agent-based modelling to investigate two different ways bacteria respond to assaults from competitors, filamentation and biofilm formation.</p> <p>Under stress, many bacterial cells will elongate without dividing to generate long filaments. We found that DNase colicins, narrow-spectrum toxins of E. coli, trigger dramatic filamentation in susceptible conspecifics, which is associated with cells actively pushing themselves out from microcolonies. We explored whether this behaviour could be a strategy for escaping from toxins by deleting the gene reported to control filamentation. However, this locus and several others tested, failed to prevent inhibition meaning that tests of a dispersal benefit were inconclusive. However, with a second toxin that induces filamentation --- the drug mitomycin C --- I found evidence that filamentation does indeed provide a strong benefit by allowing cells to disperse better from growing colonies.</p> <p>A second widespread response to toxins is for bacteria to increase biofilm formation. We explored the potential benefit of this response in competition with other bacteria using agent-based modelling. We found that making a thicker biofilm is a good way to compete even without the effects of toxins, because of the well-known benefits of reaching nutrients first. Moreover, when toxin competition occurs, we found that thick biofilms can serve to mop up toxins and help defend a strain against incoming attacks. Overall, the biofilm response can be clearly rationalised in the context of interbacterial warfare.</p> <p>Finally, we present a review of the ecology and evolution of bacterial warfare, which includes an extensive survey of currently known bacterial weapons, and how and when they are used.</p> <p>My thesis stresses the importance of toxin-mediated warfare for shaping the ecology and evolution of bacteria. But there is still much to learn about bacterial defences, and we argue that greater understanding will be needed if we are to effectively control bacterial communities for our own ends.</p> |
| spellingShingle | Competition (Biology) Microbiology Meiller-Legrand, TA Defence and response during bacterial warfare |
| title | Defence and response during bacterial warfare |
| title_full | Defence and response during bacterial warfare |
| title_fullStr | Defence and response during bacterial warfare |
| title_full_unstemmed | Defence and response during bacterial warfare |
| title_short | Defence and response during bacterial warfare |
| title_sort | defence and response during bacterial warfare |
| topic | Competition (Biology) Microbiology |
| work_keys_str_mv | AT meillerlegrandta defenceandresponseduringbacterialwarfare |