In this article, Dr Anna Dewar (Career Development Fellow in Biology) discusses her research on the evolution of bacterial genomes.

Before the mid-seventeenth century, humans had virtually no knowledge of bacteria. This is despite the fact that bacteria are found in virtually every habitat on Earth, from the bottom of the ocean to the bodies of humans and other animals. For millennia, devastating plagues and other outbreaks of disease were blamed on ‘foul air’ or divine acts, while the real culprits went undiscovered. The invention of microscopes changed this. Since the discovery of bacteria over 300 years ago, we now know that our health, the growth of our crops, and even the stability of the climate, are all dependent upon bacteria.

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In addition to their interactions with animals, plants, and the climate, we now know that bacteria also interact with each other. Rather than acting in isolation, bacteria have remarkably active ‘social lives’. Bacteria frequently exchange their genes with one another, which can allow harmful traits such as antibiotic resistance to spread between different strains or species. Bacteria also release molecules which can break down food sources or allow them entry to animal or plant hosts. These molecules act similarly to the concept of ‘public goods’ in economics: all bacteria in the surrounding area benefit from them, and so this production of the molecules is considered a form of cooperation.

If you're interested in discovering more about cooperation and gene transfer in bacteria, here are links to two of my recent papers: https://doi.org/10.1098/rspb.2023.2549 and https://doi.org/10.1038/s41559-021-01573-2

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An ancestor of bacteria also technically lives inside all of our cells. The mitochondria, often called the powerhouse of the cell, is thought to have evolved more than a billion years ago from a cell similar to a bacterium. It was likely engulfed by a larger cell, which remarkably is the ancestor of all complex life on Earth. The bacterium became the energy-producing mitochondria found in the cells of complex life, including animals, plants and fungi.

While I have hopefully convinced you that bacteria are extremely important, they are also extremely small – which can make studying them quite difficult. Thankfully, recent advances in technology mean we can now learn a lot about bacteria by examining their DNA: the universal language of life. Our ability to read and record this language has advanced enormously; for thousands of species, we now have records of full sets of genes, called ‘genomes’. By comparing genomes, we can understand which genes control particular traits and how those traits evolve.

genomes_time_plot

In my research, I use computer programs to extract information from large datasets of genomes, and then use statistics to analyse how this information varies across different species. This approach allows me to tackle broad questions. For example, how does the lifestyle of bacteria, such as where they live or who they interact with, impact how they evolve? I also use the data to investigate how the structure and content of a bacterial genome itself, such as how many genes it contains and how variable those genes are, varies depending on the lifestyle of the bacteria. Additionally, I am interested in understanding how the genomes of bacteria change in response to living very closely with another organism, such as inside another cell. And if there are changes in their genomes, are such changes specific to individual bacterial species, or are there broad patterns which emerge across species?

Biology as a whole is experiencing a huge revolution in the kind of methods and data available to researchers. More and more genomic data is being made publicly available every day, with many of the insights possible from this data likely still to be discovered.

If you'd like to learn more about Dr Dewar's research, a full list of her publications is available here.

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