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 adding sulphate to 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.
Whether this actually is a cause of autism is, as yet, unproven. But it is telling that many autistic people have a genetic defect which interferes with their sulphur metabolism. The Clostridia in their guts could thus be pushing them over the edge.
Wednesday, August 22, 2012
Speculation About Causation
An article in The Economist (h/t Ward Elliott) has some speculation about the causes of autism: