• Question: what bacteria were around in the prehistoric times? and how would you find out?

    Asked by littlesunshine45 to Anna, Chris, Jane, Iain, Nick on 11 Mar 2014.
    • Photo: Anna Middleton

      Anna Middleton answered on 11 Mar 2014:

      Hi @littlesunshine45 I read about a virus that was 30 million years old, it came back to life. It had been conserved in a fossil underground and when it came tot he surface it woke up. That’s pretty amazing

    • Photo: Iain Moal

      Iain Moal answered on 11 Mar 2014:

      Good question. It isn’t possible to know exactly what bacteria were around in prehistoric times, although sometimes fossilied bacteria can be found in very old rock, even as old as 3.5 billion years. In fact, this is how we know there was life on earth that long ago. We can also know about ancient bacteria by studying stromatolites, which are layered rocks which are formed by films of bacteria. There are some very old ones, which tells us that ancient bacteria could form films.

      Another way of finding out about ancient bacteria is by looking at creatures living today. For instance, a friend of mine is interested in the evolution of ticks, which also have to fend off bacteria. Ticks, like most animals, have proteins called defensins, which are antibacterial. Now, he has been comparing the tick defensins to those of scorpions, and they are very similar. This way, we know that the common ancestor of ticks and scorpions, millions of years ago, also had these defensins. It also tells us that the sort of bacteria that ticks and scorpions have to deal with today are similar to the sorts of bacteria that were around back then.

    • Photo: Jane Charlesworth

      Jane Charlesworth answered on 18 Mar 2014:

      Believe it or not, we actually have fossils from ancient bacteria. There are some bacteria in Australia that form mats called stromatolites and people have found fossils of these suggesting that they are the descendants of some of the most ancient life on Earth.

      Additionally, we can look at the genes in different groups of modern bacteria and work out when they split from a common ancestor by looking at the numbers of changes in the DNA that have accumulated. Mutations in DNA accumulate at a somewhat regular interval, so we can roughly estimate the time since two species split from their ancestor. Similarly, if we know that a gene works in the human immune system to fight off bacteria and we find the same gene in the mice, we can say that probably the ancestor of mice and humans got infected by similar bacteria.

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