Microbiology Editor’s Choice: defence and counter-defence evolution in E. coli and phage Lambda

Posted on June 25, 2021   by Microbiology Society

Each month, a manuscript published in our flagship journal Microbiology  is chosen by a member of the Editorial Board. This month, the paper is titled ‘Sustained coevolution of phage Lambda and Escherichia coli involves inner- as well as outer-membrane defences and counter-defences’ and was chosen by Professor Steve Diggle.

Bacteria and phage are often locked in an evolutionary arms race. In Escherichia coli, resistance against phage can involve mutations in mannose permease-encoding genes that lower the ability of the phage to eject its DNA into the cytoplasm. However, this does not always result in a lost cause for the virus. In this paper, Burmeister and colleagues performed experimental evolution to test the hypothesis that phage evolve a counter-defence strategy. Mutations arose in the E. coli manY and manZ genes, which severely impaired the ability of the ancestral phage to infect cells. However, some evolved phage grew well on the deletion mutants, indicating that they regained infectivity by evolving the ability to infect hosts independently of the mannose permease. This important finding demonstrates that coevolutionary arms races can be complex and should lead to new discoveries on the mechanisms underpinning bacteria: phage interactions. 

Sustained coevolution of phage Lambda and Escherichia coli involves inner- as well as outer-membrane defences and counter-defences

Evolutionary arms races are thought to occur throughout nature, including between hosts and their viruses. In this study, we investigated an evolutionary arms race between bacteria (E. coli, which is cell-based) and one of its viruses (called “Lambda”). E. coli is interesting with respect to viral defense: the cells have a two-layered defense system, with both an outer membrane and an inner membrane that protect against virus entry into the cell. Here, we show that both of those membranes – not just the outer one as previously thought – are important to the arms race between E. coli and Lambda.   

We spoke with author Dr Alita Burmeister to find out more: 

What is your institution and how long have you been there? 

Yale University, Department of Ecology & Evolutionary Biology. I have been here since 2017. 

What is your research area?  

Host-phage interactions, evolutionary trade-offs and trade-ups.

What inspired you to research this topic? 

After my undergraduate degree, I worked as a cheese microbiologist in the dairy industry. My job was to find phage-resistant strains of bacteria that still retained rapid fermentation phenotypes. As part of that work, I generated DNA fingerprints of many, many strains of cheese-making bacteria. I became interested in how all those diverse strains were related to one another and their environments. To answer those fundamental questions, I made my way back to academia and found an experimental system where I could experimentally answer that question by evolving bacteria and phages in the lab. That study system ended up being E. coli and phage Lambda. 

What is the most rewarding part of your research?

Generating new knowledge for the world while working with all my awesome undergraduate research mentees! 

Follow Alita and co-authors Richard Lenski and Jenna Gallie on Twitter and find out more about the research in our recent blog.