More than half your body is not human

More than half of your body is not human, say scientists.

Human cells make up only 43% of the body’s total cell count. The rest are microscopic colonists.

Understanding this hidden half of ourselves – our microbiome – is rapidly transforming understanding of diseases from allergy to Parkinson’s.

The field is even asking questions of what it means to be “human” and is leading to new innovative treatments as a result.

“They are essential to your health,” says Prof Ruth Ley, the director of the department of microbiome science at the Max Planck Institute, “your body isn’t just you”.

No matter how well you wash, nearly every nook and cranny of your body is covered in microscopic creatures.

This includes bacteria, viruses, fungi and archaea (organisms originally misclassified as bacteria). The greatest concentration of this microscopic life is in the dark murky depths of our oxygen-deprived bowels.

Prof Rob Knight, from University of California San Diego, told the BBC: “You’re more microbe than you are human.”

Originally it was thought our cells were outnumbered 10 to one.

“That’s been refined much closer to one-to-one, so the current estimate is you’re about 43% human if you’re counting up all the cells,” he says.

But genetically we’re even more outgunned.

The human genome – the full set of genetic instructions for a human being – is made up of 20,000 instructions called genes.

But add all the genes in our microbiome together and the figure comes out between two and 20 million microbial genes.

Prof Sarkis Mazmanian, a microbiologist from Caltech, argues: “We don’t have just one genome, the genes of our microbiome present essentially a second genome which augment the activity of our own.

“What makes us human is, in my opinion, the combination of our own DNA, plus the DNA of our gut microbes.”

Listen to The Second Genome on BBC Radio 4.

Airs 11:00 BST Tuesday April 10, repeated 21:00 BST Monday April 16 and on the BBC iPlayer

It would be naive to think we carry around so much microbial material without it interacting or having any effect on our bodies at all.

Science is rapidly uncovering the role the microbiome plays in digestion, regulating the immune system, protecting against disease and manufacturing vital vitamins.

Prof Knight said: “We’re finding ways that these tiny creatures totally transform our health in ways we never imagined until recently.”

It is a new way of thinking about the microbial world. To date, our relationship with microbes has largely been one of warfare.

Microbial battleground

Antibiotics and vaccines have been the weapons unleashed against the likes of smallpox, Mycobacterium tuberculosis or MRSA.

That’s been a good thing and has saved large numbers of lives.

But some researchers are concerned that our assault on the bad guys has done untold damage to our “good bacteria”.

Prof Ley told me: “We have over the past 50 years done a terrific job of eliminating infectious disease.

“But we have seen an enormous and terrifying increase in autoimmune disease and in allergy.

“Where work on the microbiome comes in is seeing how changes in the microbiome, that happened as a result of the success we’ve had fighting pathogens, have now contributed to a whole new set of diseases that we have to deal with.”

The microbiome is also being linked to diseases including inflammatory bowel disease, Parkinson’s, whether cancer drugs work and even depression and autism.

Obesity is another example. Family history and lifestyle choices clearly play a role, but what about your gut microbes?

This is where it might get confusing.

A diet of burgers and chocolate will affect both your risk of obesity and the type of microbes that grow in your digestive tract.

So how do you know if it is a bad mix of bacteria metabolising your food in such a way, that contributes to obesity?

Prof Knight has performed experiments on mice that were born in the most sanitised world imaginable.

Their entire existence is completely free of microbes.

He says: “We were able to show that if you take lean and obese humans and take their faeces and transplant the bacteria into mice you can make the mouse thinner or fatter depending on whose microbiome it got.”

Topping up obese with lean bacteria also helped the mice lose weight.

“This is pretty amazing right, but the question now is will this be translatable to humans”

This is the big hope for the field, that microbes could be a new form of medicine. It is known as using “bugs as drugs”.

Goldmine of information

I met Dr Trevor Lawley at the Wellcome Trust Sanger Institute, where he is trying to grow the whole microbiome from healthy patients and those who are ill.

“In a diseased state there could be bugs missing, for example, the concept is to reintroduce those.”

Dr Lawley says there’s growing evidence that repairing someone’s microbiome “can actually lead to remission” in diseases such as ulcerative colitis, a type of inflammatory bowel disease.

And he added: “I think for a lot of diseases we study it’s going to be defined mixtures of bugs, maybe 10 or 15 that are going into a patient.”

Microbial medicine is in its early stages, but some researchers think that monitoring our microbiome will soon become a daily event that provides a brown goldmine of information about our health.

Prof Knight said: “It’s incredible to think each teaspoon of your stool contains more data in the DNA of those microbes than it would take literally a tonne of DVDs to store.

“At the moment every time you’re taking one of those data dumps as it were, you’re just flushing that information away.

“Part of our vision is, in the not too distant future, where as soon as you flush it’ll do some kind of instant read-out and tells you are you going in a good direction or a bad direction.

“That I think is going to be really transformative.”

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Illustrations: Katie Horwich

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Why some cancers are ‘born to be bad’

A groundbreaking study has uncovered why some patients’ cancers are more deadly than others, despite appearing identical.

Francis Crick Institute scientists developed a way of analysing a cancer’s history to predict its future.

The study on kidney cancer patients showed some tumours were “born to be bad” while others never became aggressive and may not need treating.

Cancer Research UK says the study could help patients get the best care.

“We don’t really have tools to differentiate between those that need treatment and those that can be observed,” said researcher and cancer doctor Samra Turajlic.

One cancer could kill quickly while a patient with a seemingly identical cancer could live for decades after treatment.

It means uncertainty for both the patient and the doctor.

Kidney cancer

It is most common in people in their 60s and 70s. Symptoms include:

  • Blood in your pee
  • Persistent pain in the lower back or side
  • Sometimes a lump or swelling in your side

    The work, published in three papers in the journal Cell, analysed kidney cancers in 100 patients.

    The team at the Crick performed a sophisticated feat of genetics to work out the cancer’s history.

    It works like a paternity or ancestry test on steroids.

    As cancers grow and evolve, they become more mutated and, eventually, different parts of the tumour start to mutate in different ways.

    Researchers take dozens of samples from different parts of the same tumour and then work out how closely related they are.

    It allows scientists to piece together the evolutionary history of the whole tumour.

    “That also tells us where the tumour might be heading as well,” said Dr Turajlic.

    Chance to change care

    The researchers were able to classify kidney cancer into one of three broad categories:

    • Born to be bad
    • Benign
    • Intermediate

      The “born to be bad” tumours had rapid and extensive mutations and would grow so quickly they are likely to have spread round the body before they are even detected.

      Surgery to remove the original tumour may delay the use of drugs that can slow the disease.

      The benign tumours are at the complete opposite and are likely to grow so slowly they may never be a problem to patients and could just be monitored.

      The intermediate tumours were likely to initially spread to just one other location in the body and could be treated with surgery.

      Michael Malley, 72, from London, took part in the trial at the Royal Marsden Hospital after being diagnosed with kidney cancer.

      He said: “Clearly studies like these are really important for understanding how kidney cancer evolves over time, and I hope this one day leads to better treatments for patients like me.”

      There is still the challenge of figuring out how best to tailor treatments to each tumour type, and even how to perform such tests in a hospital rather than a research lab.

      The tools used in this study are being investigated in other cancers, including lung cancer.

      Dr Turajlic says: “We’ve no doubt they will be applicable to other types of cancer.”

      The studies also revealed that the earliest mutations that lead to kidney cancer were happening up to half a century before the cancer was detected.

      Sir Harpal Kumar, the chief executive of Cancer Research UK, said the study was “groundbreaking”.

      He added: “For years we’ve grappled with the fact that patients with seemingly very similar diagnoses nevertheless have very different outcomes.

      “We’re learning from the history of these tumours to better predict the future.

      “This is profoundly important because hopefully we can predict the path a cancer will take for each individual patient and that will drive us towards more personalised treatment.”

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Macular degeneration: ‘I’ve been given my sight back’

Doctors have taken a major step towards curing the most common form of blindness in the UK – age-related macular degeneration.

Douglas Waters, 86, could not see out of his right eye, but “I can now read the newspaper” with it, he says.

He was one of two patients given pioneering stem cell therapy at Moorfields Eye Hospital in London.

Cells from a human embryo were grown into a patch that was delicately inserted into the back of the eye.

‘Couldn’t see anything’

Douglas, who is from London, developed severe age-related macular degeneration in his right eye three years ago.

The macula is the part of the eye that allows you to see straight ahead – whether to recognise faces, watch TV or read a book.

He says: “In the months before the operation my sight was really poor and I couldn’t see anything out of my right eye.

“It’s brilliant what the team have done and I feel so lucky to have been given my sight back.”

The macula is made up of rods and cones that sense light and behind those are a layer of nourishing cells called the retinal pigment epithelium.

When this support layer fails, it causes macular degeneration and blindness.

Doctors have devised a way of building a new retinal pigment epithelium and surgically implanting it into the eye.

The technique, published in Nature Biotechnology, starts with embryonic stem cells. These are a special type of cell that can become any other in the human body.

They are converted into the type of cell that makes up the retinal pigment epithelium and embedded into a scaffold to hold them in place.

The living patch is only one layer of cells thick – about 40 microns – and 6mm long and 4mm wide.

It is then placed underneath the rods and cones in the back of the eye. The operation takes up to two hours.

‘Incredibly exciting’

Prof Lyndon da Cruz, consultant retinal surgeon at Moorfields, told the BBC: “We’ve restored vision where there was none.

“It’s incredibly exciting. As you get older, parts of you stop working and for the first time we’ve been able to take a cell and make it into a specific part of the eye that’s failing and put it back in the eye and get vision back.”

However, he does not call this a “cure” as completely normal vision is not restored.

Only one diseased eye was operated on in each patient.

So far the patients, the other is a woman in her early sixties, have maintained improved vision in the treated eye for a year.

They went from not being able to read with their affected eye at all, to reading 60 to 80 words per minute.

Eight more patients will take part in this clinical trial.

Doctors need to be sure it is safe. One concern is the transplanted cells could become cancerous, although there have been no such signs so far.

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    Prof Pete Coffey, from the UCL Institute of Ophthalmology, said: “This study represents real progress in regenerative medicine.

    “We hope this will lead to an affordable ‘off-the-shelf’ therapy that could be made available to NHS patients within the next five years.”

    More than 600,000 people have age-related macular degeneration in the UK. It’s the leading cause of blindness and the third globally.

    Both patients in the trial had “wet” age-related macular degeneration.

    This form of the disease is caused by abnormal blood vessels growing through the retinal pigment epithelium and damaging the macula.

    Dry age-related macular degeneration is more common and caused by the retinal pigment epithelium breaking down.

    It is hoped the patch will be able to treat both forms of the disease.

    Dr Carmel Toomes, from Leeds Institutes of Molecular Medicine, said: “What’s exciting about this study is that the patients recorded an increase in vision.

    “To see an improvement is a good sign that this therapy may help patients in the future, although further studies are needed before real conclusions can be drawn.”

    Follow James on Twitter.

    View comments

Macular degeneration: ‘I’ve been given my sight back’

Doctors have taken a major step towards curing the most common form of blindness in the UK – age-related macular degeneration.

Douglas Waters, 86, could not see out of his right eye, but “I can now read the newspaper” with it, he says.

He was one of two patients given pioneering stem cell therapy at Moorfields Eye Hospital in London.

Cells from a human embryo were grown into a patch that was delicately inserted into the back of the eye.

‘Couldn’t see anything’

Douglas, who is from London, developed severe age-related macular degeneration in his right eye three years ago.

The macula is the part of the eye that allows you to see straight ahead – whether to recognise faces, watch TV or read a book.

He says: “In the months before the operation my sight was really poor and I couldn’t see anything out of my right eye.

“It’s brilliant what the team have done and I feel so lucky to have been given my sight back.”

The macula is made up of rods and cones that sense light and behind those are a layer of nourishing cells called the retinal pigment epithelium.

When this support layer fails, it causes macular degeneration and blindness.

Doctors have devised a way of building a new retinal pigment epithelium and surgically implanting it into the eye.

The technique, published in Nature Biotechnology, starts with embryonic stem cells. These are a special type of cell that can become any other in the human body.

They are converted into the type of cell that makes up the retinal pigment epithelium and embedded into a scaffold to hold them in place.

The living patch is only one layer of cells thick – about 40 microns – and 6mm long and 4mm wide.

It is then placed underneath the rods and cones in the back of the eye. The operation takes up to two hours.

‘Incredibly exciting’

Prof Lyndon da Cruz, consultant retinal surgeon at Moorfields, told the BBC: “We’ve restored vision where there was none.

“It’s incredibly exciting. As you get older, parts of you stop working and for the first time we’ve been able to take a cell and make it into a specific part of the eye that’s failing and put it back in the eye and get vision back.”

However, he does not call this a “cure” as completely normal vision is not restored.

Only one diseased eye was operated on in each patient.

So far the patients, the other is a woman in her early sixties, have maintained improved vision in the treated eye for a year.

They went from not being able to read with their affected eye at all, to reading 60 to 80 words per minute.

Eight more patients will take part in this clinical trial.

Doctors need to be sure it is safe. One concern is the transplanted cells could become cancerous, although there have been no such signs so far.

You may also be interested in:

  • Mums’ Down’s syndrome video goes viral
  • Essential oils ‘make male breasts develop’
  • UK teacher wins global best teacher prize

    Prof Pete Coffey, from the UCL Institute of Ophthalmology, said: “This study represents real progress in regenerative medicine.

    “We hope this will lead to an affordable ‘off-the-shelf’ therapy that could be made available to NHS patients within the next five years.”

    More than 600,000 people have age-related macular degeneration in the UK. It’s the leading cause of blindness and the third globally.

    Both patients in the trial had “wet” age-related macular degeneration.

    This form of the disease is caused by abnormal blood vessels growing through the retinal pigment epithelium and damaging the macula.

    Dry age-related macular degeneration is more common and caused by the retinal pigment epithelium breaking down.

    It is hoped the patch will be able to treat both forms of the disease.

    Dr Carmel Toomes, from Leeds Institutes of Molecular Medicine, said: “What’s exciting about this study is that the patients recorded an increase in vision.

    “To see an improvement is a good sign that this therapy may help patients in the future, although further studies are needed before real conclusions can be drawn.”

    Follow James on Twitter.

    View comments