--- _id: '6291' abstract: - lang: eng text: Bacteria and their pathogens – phages – are the most abundant living entities on Earth. Throughout their coevolution, bacteria have evolved multiple immune systems to overcome the ubiquitous threat from the phages. Although the molecu- lar details of these immune systems’ functions are relatively well understood, their epidemiological consequences for the phage-bacterial communities have been largely neglected. In this thesis we employed both experimental and theoretical methods to explore whether herd and social immunity may arise in bacterial popu- lations. Using our experimental system consisting of Escherichia coli strains with a CRISPR based immunity to the T7 phage we show that herd immunity arises in phage-bacterial communities and that it is accentuated when the populations are spatially structured. By fitting a mathematical model, we inferred expressions for the herd immunity threshold and the velocity of spread of a phage epidemic in partially resistant bacterial populations, which both depend on the bacterial growth rate, phage burst size and phage latent period. We also investigated the poten- tial for social immunity in Streptococcus thermophilus and its phage 2972 using a bioinformatic analysis of potentially coding short open reading frames with a signalling signature, encoded within the CRISPR associated genes. Subsequently, we tested one identified potentially signalling peptide and found that its addition to a phage-challenged culture increases probability of survival of bacteria two fold, although the results were only marginally significant. Together, these results demonstrate that the ubiquitous arms races between bacteria and phages have further consequences at the level of the population. alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Pavel full_name: Payne, Pavel id: 35F78294-F248-11E8-B48F-1D18A9856A87 last_name: Payne orcid: 0000-0002-2711-9453 citation: ama: Payne P. Bacterial herd and social immunity to phages. 2017. apa: Payne, P. (2017). Bacterial herd and social immunity to phages. Institute of Science and Technology Austria. chicago: Payne, Pavel. “Bacterial Herd and Social Immunity to Phages.” Institute of Science and Technology Austria, 2017. ieee: P. Payne, “Bacterial herd and social immunity to phages,” Institute of Science and Technology Austria, 2017. ista: Payne P. 2017. Bacterial herd and social immunity to phages. Institute of Science and Technology Austria. mla: Payne, Pavel. Bacterial Herd and Social Immunity to Phages. Institute of Science and Technology Austria, 2017. short: P. Payne, Bacterial Herd and Social Immunity to Phages, Institute of Science and Technology Austria, 2017. date_created: 2019-04-09T15:16:45Z date_published: 2017-02-01T00:00:00Z date_updated: 2023-09-07T12:00:00Z day: '01' ddc: - '570' degree_awarded: PhD department: - _id: NiBa - _id: JoBo file: - access_level: closed checksum: a0fc5c26a89c0ea759947ffba87d0d8f content_type: application/pdf creator: dernst date_created: 2019-04-09T15:15:32Z date_updated: 2020-07-14T12:47:27Z file_id: '6292' file_name: thesis_pavel_payne_final_w_signature_page.pdf file_size: 3025175 relation: main_file - access_level: open_access checksum: af531e921a7f64a9e0af4cd8783b2226 content_type: application/pdf creator: dernst date_created: 2021-02-22T13:45:59Z date_updated: 2021-02-22T13:45:59Z file_id: '9187' file_name: 2017_Payne_Thesis.pdf file_size: 3111536 relation: main_file success: 1 file_date_updated: 2021-02-22T13:45:59Z has_accepted_license: '1' language: - iso: eng month: '02' oa: 1 oa_version: Published Version page: '83' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria status: public supervisor: - first_name: Jonathan P full_name: Bollback, Jonathan P id: 2C6FA9CC-F248-11E8-B48F-1D18A9856A87 last_name: Bollback orcid: 0000-0002-4624-4612 - first_name: Nicholas H full_name: Barton, Nicholas H id: 4880FE40-F248-11E8-B48F-1D18A9856A87 last_name: Barton orcid: 0000-0002-8548-5240 title: Bacterial herd and social immunity to phages type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2017' ... --- _id: '820' abstract: - lang: eng text: "The lac operon is a classic model system for bacterial gene regulation, and has been studied extensively in E. coli, a classic model organism. However, not much is known about E. coli’s ecology and life outside the laboratory, in particular in soil and water environments. The natural diversity of the lac operon outside the laboratory, its role in the ecology of E. coli and the selection pressures it is exposed to, are similarly unknown.\r\nIn Chapter Two of this thesis, I explore the genetic diversity, phylogenetic history and signatures of selection of the lac operon across 20 natural isolates of E. coli and divergent clades of Escherichia. I found that complete lac operons were present in all isolates examined, which in all but one case were functional. The lac operon phylogeny conformed to the whole-genome phylogeny of the divergent Escherichia clades, which excludes horizontal gene transfer as an explanation for the presence of functional lac operons in these clades. All lac operon genes showed a signature of purifying selection; this signature was strongest for the lacY gene. Lac operon genes of human and environmental isolates showed similar signatures of selection, except the lacZ gene, which showed a stronger signature of selection in environmental isolates.\r\nIn Chapter Three, I try to identify the natural genetic variation relevant for phenotype and fitness in the lac operon, comparing growth rate on lactose and LacZ activity of the lac operons of these wild isolates in a common genetic background. Sequence variation in the lac promoter region, upstream of the -10 and -35 RNA polymerase binding motif, predicted variation in LacZ activity at full induction, using a thermodynamic model of polymerase binding (Tugrul, 2016). However, neither variation in LacZ activity, nor RNA polymerase binding predicted by the model correlated with variation in growth rate. Lac operons of human and environmental isolates did not differ systematically in either growth rate on lactose or LacZ protein activity, suggesting that these lac operons have been exposed to similar selection pressures. We thus have no evidence that the phenotypic variation we measured is relevant for fitness.\r\nTo start assessing the effect of genomic background on the growth phenotype conferred by the lac operon, I compared growth on minimal medium with lactose between lac operon constructs and the corresponding original isolates, I found that maximal growth rate was determined by genomic background, with almost all backgrounds conferring higher growth rates than lab strain K12 MG1655. However, I found no evidence that the lactose concentration at which growth was half maximal depended on genomic background." acknowledgement: "ERC H2020 programme (grant agreement no. 648440)\r\nThanks to Jon Bollback for giving me the chance to do this work, for sharing the ideas that lay at the basis of this work, for his honesty and openness, showing himself to me as a person and not just as a boss. Thanks to Nick Barton for his guidance at the last stage, reading and commenting extensively on several versions of this manuscript, and for his encouragement; thanks to both Jon and Nick for their kindness and patience. Thanks to Erik van Nimwegen and Calin Guet for their time and willingness to be in my thesis committee, and to Erik van Nimwegen especially for agreeing to enter my thesis committee at the last moment, and for his very sharp, helpful and relevant comments during and after the defense. Thanks to my collaborators and discussion partners: Anne Kupczok, for her guidance, ideas and discussions during the construction of the manuscript of Chapter Two, and her comments on the manuscript; Georg Rieckh for making me aware of the issue of parameter identifiability, suggesting how to solve it, and for his unfortunate idea to start the plasmid enterprise in the first place; Murat Tugrul for sharing his model, for his enthusiasm, and his comments on Chapter Three; Srdjan Sarikas for his collaboration on the Monod model fitting, fast forwarding the analysis to turbo speed and making beautiful figures, and making the discussion fun on top of it all; Vanessa Barone for her last minute comments, especially on Chapter Three, providing a sharp and very helpful experimentalist perspective at the last moment; Maros Pleska and Marjon de Vos for their comments on the manuscript of Chapter Two; Gasper Tkacik for his crucial input on the relation between growth rate and lactose concentration; Bor Kavcic for his input on growth rate modeling and error propagation. Thanks to the Bollback, Bollenbach, Barton, Guet and Tkacik group members for both pro- viding an inspiring and supportive scientific environment to work in, as well as a lot of warmth and colour to everyday life. And thanks to the friends I found here, to the people who were there for me and to the people who changed my life, making it stranger and more beautiful than I could have imagined, Maros, Vanessa, Tade, Suzi, Andrej, Peter, Tiago, Kristof, Karin, Irene, Misha, Mato, Guillaume and Zanin. " alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Fabienne full_name: Jesse, Fabienne id: 4C8C26A4-F248-11E8-B48F-1D18A9856A87 last_name: Jesse citation: ama: Jesse F. The lac operon in the wild. 2017. doi:10.15479/AT:ISTA:th_857 apa: Jesse, F. (2017). The lac operon in the wild. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:th_857 chicago: Jesse, Fabienne. “The Lac Operon in the Wild.” Institute of Science and Technology Austria, 2017. https://doi.org/10.15479/AT:ISTA:th_857. ieee: F. Jesse, “The lac operon in the wild,” Institute of Science and Technology Austria, 2017. ista: Jesse F. 2017. The lac operon in the wild. Institute of Science and Technology Austria. mla: Jesse, Fabienne. The Lac Operon in the Wild. Institute of Science and Technology Austria, 2017, doi:10.15479/AT:ISTA:th_857. short: F. Jesse, The Lac Operon in the Wild, Institute of Science and Technology Austria, 2017. date_created: 2018-12-11T11:48:41Z date_published: 2017-08-25T00:00:00Z date_updated: 2023-09-07T12:01:21Z day: '25' ddc: - '576' - '577' - '579' degree_awarded: PhD department: - _id: JoBo doi: 10.15479/AT:ISTA:th_857 ec_funded: 1 file: - access_level: open_access checksum: c62257a7bff0c5f39e1abffc6bfcca5c content_type: application/pdf creator: system date_created: 2018-12-12T10:17:00Z date_updated: 2020-07-14T12:48:10Z file_id: '5252' file_name: IST-2017-857-v1+1_thesis_fabienne.pdf file_size: 3417773 relation: main_file - access_level: closed checksum: fc87d7d72fce52824a3ae7dcad0413a8 content_type: application/x-tex creator: dernst date_created: 2019-04-05T08:51:59Z date_updated: 2020-07-14T12:48:10Z file_id: '6212' file_name: 2017_thesis_Jesse_source.tex file_size: 215899 relation: source_file file_date_updated: 2020-07-14T12:48:10Z has_accepted_license: '1' language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '08' oa: 1 oa_version: Published Version page: '87' project: - _id: 2578D616-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '648440' name: Selective Barriers to Horizontal Gene Transfer publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria publist_id: '6829' pubrep_id: '857' status: public supervisor: - first_name: Jonathan P full_name: Bollback, Jonathan P id: 2C6FA9CC-F248-11E8-B48F-1D18A9856A87 last_name: Bollback orcid: 0000-0002-4624-4612 title: The lac operon in the wild tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2017' ... --- _id: '1121' abstract: - lang: eng text: "Horizontal gene transfer (HGT), the lateral acquisition of genes across existing species\r\nboundaries, is a major evolutionary force shaping microbial genomes that facilitates\r\nadaptation to new environments as well as resistance to antimicrobial drugs. As such,\r\nunderstanding the mechanisms and constraints that determine the outcomes of HGT\r\nevents is crucial to understand the dynamics of HGT and to design better strategies to\r\novercome the challenges that originate from it.\r\nFollowing the insertion and expression of a newly transferred gene, the success of an\r\nHGT event will depend on the fitness effect it has on the recipient (host) cell. Therefore,\r\npredicting the impact of HGT on the genetic composition of a population critically\r\ndepends on the distribution of fitness effects (DFE) of horizontally transferred genes.\r\nHowever, to date, we have little knowledge of the DFE of newly transferred genes, and\r\nhence little is known about the shape and scale of this distribution.\r\nIt is particularly important to better understand the selective barriers that determine\r\nthe fitness effects of newly transferred genes. In spite of substantial bioinformatics\r\nefforts to identify horizontally transferred genes and selective barriers, a systematic\r\nexperimental approach to elucidate the roles of different selective barriers in defining\r\nthe fate of a transfer event has largely been absent. Similarly, although the fact that\r\nenvironment might alter the fitness effect of a horizontally transferred gene may seem\r\nobvious, little attention has been given to it in a systematic experimental manner.\r\nIn this study, we developed a systematic experimental approach that consists of\r\ntransferring 44 arbitrarily selected Salmonella typhimurium orthologous genes into an\r\nEscherichia coli host, and estimating the fitness effects of these transferred genes at a\r\nconstant expression level by performing competition assays against the wild type.\r\nIn chapter 2, we performed one-to-one competition assays between a mutant strain\r\ncarrying a transferred gene and the wild type strain. By using flow cytometry we\r\nestimated selection coefficients for the transferred genes with a precision level of 10-3,and obtained the DFE of horizontally transferred genes. We then investigated if these\r\nfitness effects could be predicted by any of the intrinsic properties of the genes, namely,\r\nfunctional category, degree of complexity (protein-protein interactions), GC content,\r\ncodon usage and length. Our analyses revealed that the functional category and length\r\nof the genes act as potential selective barriers. Finally, using the same procedure with\r\nthe endogenous E. coli orthologs of these 44 genes, we demonstrated that gene dosage is\r\nthe most prominent selective barrier to HGT.\r\nIn chapter 3, using the same set of genes we investigated the role of environment on the\r\nsuccess of HGT events. Under six different environments with different levels of stress\r\nwe performed more complex competition assays, where we mixed all 44 mutant strains\r\ncarrying transferred genes with the wild type strain. To estimate the fitness effects of\r\ngenes relative to wild type we used next generation sequencing. We found that the DFEs\r\nof horizontally transferred genes are highly dependent on the environment, with\r\nabundant gene–by-environment interactions. Furthermore, we demonstrated a\r\nrelationship between average fitness effect of a gene across all environments and its\r\nenvironmental variance, and thus its predictability. Finally, in spite of the fitness effects\r\nof genes being highly environment-dependent, we still observed a common shape of\r\nDFEs across all tested environments." acknowledgement: "This study was supported by European Research Council ERC CoG 2014 – EVOLHGT,\r\nunder the grant number 648440.\r\n\r\nIt is a pleasure to thank the many people who made this thesis possible.\r\nI would like to first thank my advisor, Jonathan Paul Bollback for providing guidance in\r\nall aspects of my life, encouragement, sound advice, and good teaching over the last six\r\nyears.\r\nI would also like to thank the members of my dissertation committee – Călin C. Guet\r\nand John F. Baines – not only for their time and guidance, but for their intellectual\r\ncontributions to my development as a scientist.\r\nI would like to thank Flavia Gama and Rodrigo Redondo who have taught me all the\r\nskills in the laboratory with their graciousness and friendship. Also special thanks to\r\nBollback group for their support and for providing a stimulating and fun environment:\r\nIsabella Tomanek, Fabienne Jesse, Claudia Igler, and Pavel Payne.\r\nJerneja Beslagic is not only an amazing assistant, she also has a smile brighter and\r\nwarmer than the sunshine, bringing happiness to every moment. Always keep your light\r\nNeja, I will miss our invaluable chatters a lot." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Hande full_name: Acar, Hande id: 2DDF136A-F248-11E8-B48F-1D18A9856A87 last_name: Acar orcid: 0000-0003-1986-9753 citation: ama: Acar H. Selective barriers to horizontal gene transfer. 2016. apa: Acar, H. (2016). Selective barriers to horizontal gene transfer. Institute of Science and Technology Austria. chicago: Acar, Hande. “Selective Barriers to Horizontal Gene Transfer.” Institute of Science and Technology Austria, 2016. ieee: H. Acar, “Selective barriers to horizontal gene transfer,” Institute of Science and Technology Austria, 2016. ista: Acar H. 2016. Selective barriers to horizontal gene transfer. Institute of Science and Technology Austria. mla: Acar, Hande. Selective Barriers to Horizontal Gene Transfer. Institute of Science and Technology Austria, 2016. short: H. Acar, Selective Barriers to Horizontal Gene Transfer, Institute of Science and Technology Austria, 2016. date_created: 2018-12-11T11:50:16Z date_published: 2016-12-01T00:00:00Z date_updated: 2023-09-07T11:42:26Z day: '01' ddc: - '570' degree_awarded: PhD department: - _id: JoBo ec_funded: 1 file: - access_level: closed checksum: 94bbbc754c36115bf37f8fc11fad43c4 content_type: application/pdf creator: dernst date_created: 2019-08-13T11:17:50Z date_updated: 2019-08-13T11:17:50Z file_id: '6814' file_name: PhDThesis_HandeAcar_1230.pdf file_size: 3682711 relation: main_file - access_level: open_access checksum: 94bbbc754c36115bf37f8fc11fad43c4 content_type: application/pdf creator: dernst date_created: 2021-02-22T11:51:13Z date_updated: 2021-02-22T11:51:13Z file_id: '9184' file_name: 2016_Thesis_HandeAcar.pdf file_size: 3682711 relation: main_file success: 1 file_date_updated: 2021-02-22T11:51:13Z has_accepted_license: '1' language: - iso: eng month: '12' oa: 1 oa_version: Published Version page: '75' project: - _id: 2578D616-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '648440' name: Selective Barriers to Horizontal Gene Transfer publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria publist_id: '6239' status: public supervisor: - first_name: Jonathan P full_name: Bollback, Jonathan P id: 2C6FA9CC-F248-11E8-B48F-1D18A9856A87 last_name: Bollback orcid: 0000-0002-4624-4612 title: Selective barriers to horizontal gene transfer type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2016' ...