Oh Dear. Never let microbiologists name stuff. We can’t even classify Strep properly so when a new virus is discovered that lives up half the human race’s Chocolate Starfishes you just know it’s not going to end well.

Newly-discovered crAssphage (seriously!) doesn’t infect us: it attacks some of the resident bacteria among the thousands of species that make up our gut microbiota. Which is unsurprising; the bacteria that live on and in us (and outnumber human cells 10-100 –fold) all are just as susceptible to viral marauders as we are. Just different ones.

Viruses that attack bacteria are called bacteriophages or just ‘phage’ for short – and there are lots of them. (Also it rhymes with page or rage, not barge or décolletage. Unless you’re French. Lots of great microbiology has come from the truffle-chomping wine sucking anarchists but only they are allowed to pronounce it that way. For those of us who aren’t snail slurping surrender monkeys pronouncing it faaaaaaaaaaaaahge is pure affectation).

Anyway, the principal reason a virus apparently soooo ubiquitous has remained undiscovered for soooo long (aside from it not being a human pathogen so no one was looking) is the ease that with which one can now sequence and analyse the genetic footprints of all sorts of things lurking in – for example – a simple, honest turd. By means of illustration, more than 80% of the resident bacteria in your gut can’t be grown in a lab, let alone their viral predators. In this case they haven’t isolated the virus yet, they just know it’s there because its genetic footprints can be detected.

Sleuthing genes becomes ever more prevalent but this technique is different. The key point here is we have been able to isolate a genetic needle in a haystack for a while because we were looking for a specific needle and we knew what it looked like. The difference here is we’re analysing a bunch of whole haystacks to see if there are any other interesting needles we weren’t aware of or even looking for. As if that’s not interesting enough…

The really interesting thing about crAssphage is it looks like it is involved in controlling the number of Bacteroidetes in the gut.

Bacter-what? OK. The phyla Bacteroidetes and Firmicutes are the Montagues and Capulets of the human gut. Fat people have more firmicutes and fewer bacteroidetes than thin ones. And if dieting makes a fat person thin, the bacterial flora changes to match. So could adjusting the composition of our internal microbiological ecosystem alter our weight? Could you take a crAssphage suppository to lose a few pounds? Who knows. (Hint: rhetorical question – no one knows yet so don’t believe any hype from people selling probiotics!)

This new window on the germ warfare that constantly goes on within us is yet another of the many fascinating aspects of the microbiota we’ve co-evolved with for millions of years. And I use the plural as those of Our Microbial Overlords who choose to cohabit with us are similar but slightly different in each and every one of us.

But our microbiomes do lots of cool and vital stuff: they digest many foodstuffs we can’t unlocking the nutritional potential in many foods we cannot fully digest. The microbiome also manufactures vitamins, notably B2, B12, K and folic acid. It can adjust its output to its host’s needs and diet: the microbiomes of babies make more folic acid than do those of adults. And microbiomes in vitamin-hungry places like Malawi and Venezuela turn out more of these chemicals than do those in the guts of North Americans.

One of the more striking claims for links between our microbiome and our health has to do with the brain. It has been known for a long time that people with autism generally have intestinal problems as well, and that these are often coupled with ‘abnormal’ microbiota.

Even a well-functioning microbiome is not one without internal conflicts – there is competition in every ecosystem – even stable, productive ones. Clostridia kill bacteria competing for their niches with chemicals called phenols (carbolic acid, the first antiseptic, is one such). But phenols are poisonous to human cells too, and thus have to be neutralised. This is done by whacking some sulphate up them. So having too many clostridia, producing too many phenols, will deplete the body’s reserves of sulphur. And sulphur is needed for other things — including brain development. If an unusual microbiome leads to the gut needing extra sulphur the brain may pay the price by developing abnormally.

But there is a real danger of placing the effectual cart before the causal horse here – we just don’t know which way around it is or even if there is any causal link. Correlation is not necessarily causation, remember?

This reminds me of the nonsense claims by none other than Andrew Jeremy Wakefield who is now running an outfit claiming you can ‘cure’ autism with diet. This is the same Andrew Jeremy Wakefield who still claims he ‘will be vindicated’ when interviewed by credulous and ignorant hackettes in the Daily Fail. But until he publishes (don’t hold your breath) he will forever be known as the researcher who was struck off the medical register in the UK for abusing autistic children (this is the GMC’s term, not mine) in the service of ‘science’ (so he claimed) – and when the data from his research (funded by sources he failed to disclose) didn’t stack up he invented new ones.

Add to this Utter, Utter Bollocks (µ²B) like ‘leaky gut syndrome’ and all manner of other woo and I foresee crAssphage assuming a life of its own way beyond the science once the Warriors of Woo get hold of it.

Remember you heard it here first…

[Pedants’ Post Script: ‘microbiota’ refers to those of Our Microbial Overlords we provide social care and transport for. The ‘microbiome’ also includes the genetic wild cards we lack which they bring to the party. The terms are – to all intents and purposes – interchangeable depending on the audience!]