Sex, bacteria & EU

Marie Curie ActionsHave you ever wondered why we have sex?

Suppose you ask 100 people this question. Some would say it’s fun, some would say for pleasure, some would say to have kids, some would say ‘because we want to’, others would be so surprised that they wouldn’t even know what to say. But most certainly almost all of them would not find this a particularly puzzling problem.

So let me rephrase the question. Why is it that we need men to have children? Instead, couldn’t women simply make copies (clones) or themselves? Imagine how much easier that would be. No broken hearts, no games, no time consuming dating, no conflicts of interest, no divorces etc. The world without males would be even better than a world without lawyers!

Funny thing is that many species out there actually do it this way. Some species of snakes, lizards, rotifers, fish and many others – they live in female populations giving birth to female offspring. Biologists call this parthenogenesis (it comes from Greek, parthenos – virgin, genesis – birth). Happy days! But let’s face it, this is more of an exception than a rule. Scientists estimate that 99.9% of animals reproduce sexually, as well as many plants and fungi, or even viruses. But there are other organisms out there which also have sex; organisms which we all know very well: bacteria. The sex they have is slightly different from the sex animals have though. I’ll explain in a second how.

But let me first explain what sex is. In a general sense, sex means shuffling of our genetic material. A future mom finds a future dad, they have a ‘sexy time’, and mix their genes to make little “shuffled” copies of themselves. From a genetic point of view, this is what we are: “shuffled copies” of our parents.

Bacterial sex is slightly different. Bacteria don’t need a date, a foreplay, nor a stimulating discussion to have sex. They don’t even need an intercourse (although sometimes they go for it). All they need is DNA of other bacteria. When DNA, for example from dead bacterial cells (basically, bacterial necrophilia), is around, they can “swallow” it and exchange the new DNA fragments with their own. So they also shuffle DNA – they also have sex.

There is one bacterium that is particularly fond of it. It’s called Streptococcus pneumoniae (aka. the pneumococcus), and it’s known by most mums out there who are advised to vaccinate their babies against them. The pneumococcus is often a part of the natural bacterial flora in our throat, and is usually harmless. Sometimes, however, Dr. Jekyll turns into Mr. Hyde, and infects the lungs, the brain, or other parts of the body, causing very serious illness. In fact, it’s so serious that it probably kills over 1.2 million children worldwide under the age of 5 every year, especially in Africa.

What is not entirely clear is whether Dr. Jekyll/Mr. Hyde is so dangerous because it has sex. Why would sex make it dangerous? Because it offers the bacterium a very rapid means of change. DNA encodes for proteins, and proteins are what our immune system, drugs and vaccines target to fight the pathogen. A change in the protein structure, immediately achieved by sex, can thus be good for the pneumococcus because it could make it “invisible”, and therefore a much more difficult target. Sex is a rapid way of reacting against environmental threats, and those threats are constituted by ourselves – we are the ones who make the lives of pneumococci difficult to prevent the disease they cause. But this also means we could be provoking them to have more sex and becoming even more dangerous! We need to understand this process better to protect ourselves against those pathogenic, sex-crazy bacteria.

My latest research project, where I proposed to investigate this in more detail, has just been chosen by the European Commission to be offered funding under the FP7 programme. This means that starting in 2013, should the negotiations go well, I will be a Marie Curie fellow for 2 years. I will be tackling the problem of bacterial sex by using computer simulations and analysis of bacterial DNA sequences. The project will be conducted at Imperial College London (with Prof. Christophe Fraser), in collaboration with the Wellcome Trust Sanger Institute at Cambridge, UK.

Looking forward to bring you more updates from the field as the project develops!

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