Tag: Pseudomonas aeruginosa

I am happy to (finally) report that the second part of Emil Burman‘s PhD thesis was published over the weekend in FEMS Microbiology Letters! This paper has spent almost a year in peer review, but that’s even more reason to celebrate that it is finally out.

In this paper, we have studied how Pseudomonas aeruginosa compete with other members in microbial communities (1). To study this, we introduced two different P. aeruginosa strains into the microbial model community THOR (2): the relatively non-virulent PAO1 and the model strain for virulent P. aeruginosa PA14. First of all, we could show that P. aeruginosa invasion significantly disrupted the biofilms formed by THOR. In addition, this disruption was greater, both in terms of reduction of biofilm biomass and changes in microbial community composition, during invasion with PA14 than for PAO1. This suggests that the virulence traits expressed by P. aeruginosa can also play a role in its ability to outcompete other microbes, i.e. that virulence and competition traits are linked.

Along these lines, we also studied the invasion ability of an O-antigen-deficient P. aeruginosa strain, which had even further reduced competitive ability. Finally, we investigated two naturally occurring P. aeruginosa isolates for their invasion ability in THOR: the clinical isolates CCUG73475 (from a patient with septic bacteremia) and CCUG71613 (from a patient with chronic pneumonia). Invasion with the pneumonia-derived isolate CCUG71613 resulted in minimal changes to the THOR community, while invasion with the sepsis-derived isolate CCUG73475 led to a reduction in the CFU counts of all THOR community members, suggesting differences in virulence and competition traits between different clinical isolates.

The paper was a collaboration with Lars Jelsbak and Mikkel Anbo at the Technical University of Denmark, and was conceived during a visit that Emil and I did there in 2022. Emil actually looked at a whole bunch of strains with their O-antigens replaced, but in the end the virulence story was the most coherent one we could tell, and the rest of the O-antigen data will likely be sitting on a shelf never to be released. Sometimes academia works like that. But I am happy about the outcome of our collaboration with Lars and Mikkel!

The study builds on our work on different disturbances to community interactions in THOR, where Emil has previous work on how temperature changes the interactions between the community members (3). We also have data on genes in P. aeruginosa that are important for community invasion in THOR which is in the pipeline to be submitted, along with a study on antibiotic exposure on P. aeruginosa. So even if Emil has defended his thesis the work on his work lives on!

References

1. Burman E, Anbo M, Jelsbak L, Bengtsson-Palme J: Virulent strains of Pseudomonas aeruginosa are more disruptive during invasion of a microbial model community. FEMS Microbiology Letters, fnag090 (Advance article) (2026). doi: 10.1093/femsle/fnag090
2. Lozano GL, Bravo JI, Garavito Diago MF, Park HB, Hurley A, Peterson SB, Stabb EV, Crawford JM, Broderick NA, Handelsman J: Introducing THOR, a Model Microbiome for Genetic Dissection of Community Behavior. mBio, 10, 2, e02846-18 (2019). doi: 10.1128/mBio.02846-18
3. Burman E, Bengtsson-Palme J: Microbial community interactions are sensitive to small differences in temperature. Frontiers in Microbiology, 12, 672910 (2021). doi: 10.3389/fmicb.2021.672910

I am happy to share the news that my first doctoral student – Emil Burman – successfully defended his thesis yesterday, and can now introduce himself as Dr. Burman.

And in what a way he defended! During the three hour defense, he was asked all the hard questions from his opponent – Akos Kovács – who did an amazing job bringing out Emil’s vast and diverse knowledge of the field. In fact, the committee noted afterwards that it took more than one and a half hours of questioning before Emil had to admit “I don’t know the answer to that”.

Emil’s thesis, titled “Genetic Contributions to Invasion and Biofilm Disruption in a Microbial Model Community“, used the microbial model community THOR (1) to investigate community responses to environmental stress and microbial invasion. The thesis (2) consists of five papers, the first dealing with how temperature affects THOR (3), the second with how pathogenicity is related to competition ability in a community setting, the third about the genetic determinants of antibiotic susceptibility in Pseudomonas aeruginosa, the fourth about invasion with P. aeruginosa into THOR, and the last one is a proteomics study about one of the strongest hits in paper IV.

Emil has used a range of techniques, including traditional microbiological assays, transposon mutagenesis (INSeq), and proteomics, to identify genetic determinants of community stability and disruption. This has allowed him to explore how cooperative traits emerge and how pathogens like Pseudomonas aeruginosa interfere with community dynamics. His thesis can be found in an online version here.

References

1. Lozano GL, Bravo JI, Garavito Diago MF, Park HB, Hurley A, Peterson SB, Stabb EV, Crawford JM, Broderick NA, Handelsman J: Introducing THOR, a Model Microbiome for Genetic Dissection of Community Behavior. mBio, 10, 2, e02846-18 (2019). doi: 10.1128/mBio.02846-18
2. Burman E: Genetic Contributions to Invasion and Biofilm Disruption in a Microbial Model Community. PhD Thesis, University of Gothenburg (2025). https://gupea.ub.gu.se/handle/2077/87262
3. Burman E, Bengtsson-Palme J: Microbial community interactions are sensitive to small differences in temperature. Frontiers in Microbiology, 12, 672910 (2021). doi: 10.3389/fmicb.2021.672910