Dawn of a new scientific discipline: Microbial endocrinology

Posted by mjs76 at Nov 15, 2010 12:10 PM |
New book shows that bacteria can tell when you’re stressed – and take advantage of it.

Inside your body are trillions of micro-organisms. In fact, since microbes outnumber your cells by more than 10 to 1, you are a walking ecosystem. Some of these microscopic lodgers - which together account for about a kilogram of your overall bodyweight - are good to have, helping you with things like digestion. On the other hand, some can be trouble, seeking to lay you low with a sore throat, runny nose or worse.

Now, it has long been known that stress increases our susceptibility to infections. Anyone who has ever sat in an exam hall full of coughing, sniffing medical students taking their finals can confirm this. But why – and how – does stress affect us in this way?

The accepted view for nearly a century was always that the hormones released when we are stressed, such as adrenaline and noradrenaline, impair our immune system. This reduction in the strength of our defences then allows bacteria to wreak their havoc on our bodies. But science isn’t about accepting the accepted view, it’s about challenging the accepted view. It’s about suggesting new ideas and seeing whether they are robust enough to stand up to scrutiny.

Back in 1992, American endocrinologist Mark Lyte, a professor at Texas Tech University in Lubbock, proposed a new theory: that the bacteria inside our bodies actively respond to the production of these stress hormones. In other words, rather than these hormones simply weakening the immune defence, they actually act as a trigger to strengthen the attack of the infectious challenger. It wasn’t the most notable conference presentation; the entire audience, apart from two duty-bound conference organisers, consisted of one person. And she was Mark Lyte’s lab assistant. But it was a start, and the science of ‘microbial endocrinology’ was born.

Shortly afterwards, Professor Lyte teamed up with Dr Primrose Freestone from our Department of Infection, Immunity and Inflammation, who was a post doc at the time. Together they have nurtured this nascent field of scientific research for over a decade. Papers have been published, the first international meeting on microbial endocrinology, organised by Mark and Primrose, was held in Canada in 2007. And, now comes the world’s first book on Microbial Endocrinology, edited by Lyte and Freestone.

Microbial endocrinology as a research discipline is the point where microbiology (the study of microbes) meets endocrinology (the study of hormones) with a nod towards neurophysiology (the study of the nervous system – did you know that your gut contains as many nerve cells as your spinal column?). Historically, endocrinologists have considered the human/mammalian body as the subject under investigation and the bacteria present as simply factors to be taken into consideration. On the other side of the coin, microbiologists have concentrated (understandably) on the bacteria without giving a great deal of thought to the nature of the host’s body.

E. coli (image: Wikipedia)

The new science of microbial endocrinology considers the bacteria and the host as a whole system and looks in detail at how each affects the other, and what they are saying to one another. The bacteria considered include some that will be familiar to everyone such as Escherichia coli, which can give you food poisoning, and Staphylococcus aureus which, in its MRSA form, can be deadly. And it’s not just about intestinal bacteria: there are hundreds of different bacteria in your saliva, in the fluid around your eyes, on your skin, pretty much everywhere. Primrose, Mark and their colleagues have yet to identify a human-hosted bacterium which doesn’t respond to at least one human hormone.

And this isn’t just about humans, or even mammals. Bacteria existed long before any multicellular lifeforms and have evolved alongside the entire animal and plant kingdoms. Almost every living thing produces hormones and almost every living cell-based life form has bacteria in or on it, potentially responding to those hormones. So this doesn’t just have implications for human health but also for animal health, food production, agriculture and other related areas.

It is the nature of a new field that discoveries come in rapid succession, that new information and ideas are profuse and that pretty much every experiment or study opens up a whole new area. This is virgin territory, the biological equivalent of the exploration of Antarctica in the early 20th century. Microbial Endocrinology: Interkingdom Signaling in Infectious Disease and Health is the first step on a massively exciting new scientific journey.

The book is published by Springer in hardback at a wallet-busting £135* (but that’s how much these things cost…). As well as Primrose, other Leicester researchers contributing to the book include Dr Noura al-Dayan, Dr Sara Sandrini and Dr Cordula Stover from our Department of Infection, Immunity and Inflammation and Dr Richard Haigh from our Department of Genetics.

*Students - Primrose has kindly donated a copy of the book to the Clinical Sciences Library. You can also read the text online via SpringerLink. Primrose is happy to answer any questions on the subject and can be contacted at ppef1@le.ac.uk.