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Skip to 0 minutes and 11 seconds In this step, I’m back in the microbiology teaching lab with Dr. Sheila MacIntyre, a medical microbiologist, to discuss her research on bacterial pathogens. So I know that some of your research is working on a very notorious pathogen. Could you tell me some more about that? So yes, I work on a bacteria called yersinia pestis. It’s the cause of plague, bubonic plague that most people have heard about and associate with plague in the Middle Ages. It did kill about 30% to 40% of the European population within five, six years in the Middle Ages. And people think of it as a bacteria in the past, but actually, it’s very much still with us today.

Skip to 0 minutes and 53 seconds So it’s in California, Brazil, Asia, and in India in the 1990s it caused havoc because there was quite a serious outbreak then. And then most recently, there was one last year in Madagascar, where over 1,000 people were identified as having plague. Wow, that’s incredible that it’s still with us today. I always thought that it had been eradicated in the Middle Ages. But is it still associated, then, with rats? Rats and rodents. So it lives in prairie dogs, it lives in rodents in the wild, and it transfers from rodents to us via fleas. And that’s one aspect that’s really interesting about this bacteria, actually, because it evolved from a bacteria that’s transmitted by the faecal-oral route. Causes gastroenteritis.

Skip to 1 minute and 41 seconds So there’s a close relative that makes us sick, and thousands of years ago, the ancestor of yersinia pestis picked up some genes that let it survive in the flea. Then once it can survive in the flea, it then bypasses a lot of our immune system, because as the flea tries to eat, it injects the bacteria directly into our body. So bypasses the skin, bypasses the mucosal surfaces. So now there’s a very efficient way of transmission. The bacteria’s got two different lifestyles it’s got one lifestyle in the flea, and it’s got another lifestyle in the mammal.

Skip to 2 minutes and 18 seconds So in the flea it switches off all the genes it requires to live there at 26 degrees, and then the mammal, whether it’s a rodent or whether it’s us, is now living at 37. And it switches on the genes that are required for survival there. So once it’s done that, and it’s been injected and lived inside us, it can spread around the body. It starts off in the buboes, bubonic Plague. So very enlarged lymph nodes around here, here. The bacteria loves living there, multiplies there. It can then spread in our bodies and go to the lungs. And then it’s primed and it can be transmitted person to person. And that form’s really dangerous.

Skip to 2 minutes and 59 seconds That’s 100% fatality if you’re not treated very quickly with antibiotics. So there’s different sets of genes which are regulated by temperature within the bacterium? Yeah. Temperature’s one of the key regulators, because it’s going between the different lifestyles, and that’s one thing we’re interested in. So we work on this coat that surrounds the bacterium. It’s like fibres called F1. It forms a dense coat around the bacterium, and it’s unique to yersinia pestis. It protects the bacteria, helps protect it from the immune system. How do you actually study this in the lab? Well, we don’t work with yersinia pestis. We work with the whole system cloned in E. coli. So it’s safe.

Skip to 3 minutes and 48 seconds If you wanted to work with yersinia pestis, it’s level three. It’s very dangerous. So we work with the whole system and all functions in E. coli and we work with it in E. coli. Well, thank you, Sheila. It’s been really great talking to you about yersinia pestis, and I believe I’ve learned a lot about bubonic and pneumonic plague. And I look forward to seeing any research that might come out of your lab in the near future. Good, great. Thank you.

Meet Dr Sheila MacIntrye

In this video, I meet with Dr Sheila MacIntrye to discuss her research on the bacterium Yersinia pestis, that you learnt in the previous Step has caused several plague pandemics over the past few centuries.

Many people commonly assume plague has been eradicated. Were you as surprised as I was to hear that plague still exists today?

It would be interesting to hear if you’ve watched a period drama or film that has dramatised the effects of plague or other infectious diseases. Share your thoughts in the comments area below.

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Small and Mighty: Introduction to Microbiology

University of Reading

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