Have you ever wondered how it is that among people exposed to food poisoning - or, for that matter, a highly infectious disease - not everyone gets sick.
Have you ever noticed that those irritating and socially irresponsible co-workers who refuse to have flu vaccines are sometimes the only ones left standing when flu sweeps through the office?
Have you wondered how it is that acne is rife in young children in modern society - but not in non-westernised societies?
How is it that 35% of women with a mutated BRCA1 gene don't get breast cancer?
The answer, it turns out, could well be the opposite of dysbiosis - symbiosis which means living together in a mutually beneficial relationship.
There are approximately ten times more bacterial cells in the human body than human cells. We have traditionally thought of bacteria as dangerous invaders, to be suppressed and wiped out wherever possible, when in fact they are us. We have been waging war on ourselves, with considerable success it seems, going by the plethora of illnesses we are subject to, the marvels of modern medicine notwithstanding.
We are, it turns out, walking eco-systems, and just as we have been blindly (but determinedly) trying to wipe out the planetary eco-system, we have been doing the same to ourselves.
Bacteria are, in a sense, the intermediators between us and an increasingly hostile external (and internal) environment. The extent to which we can shrug off the soup of pollutants that our modern way of life exposes us to may well depend on how well we look after the bacterial communities that are part of us.
As Michael Pollan points out in his recent article in the New York Times - which should be required reading for all parents and prospective parents, as well as policy makers - it is now thought that our dependence on bacteria has arisen because they evolve infinitely faster than us - in some cases a new generation in 20 minutes. This enables them to help us adapt more agilely to new environmental threats, such as disease and (in the modern world) extreme chemical pollution.
It may not be too fanciful to think that one day in the not too distant future the use of broad spectrum antibiotics may be shunned - especially in babies and young children - and replaced by a more intelligent approach to diet and the use of narrow spectrum antibiotics that target solely the pathogens that are causing a problem, instead of disrupting our entire bacterial communities, sometimes on a permanent basis.
Diet may play a huge part in all of this too. This is from a University of British Columbia study published last year:
"Evidence suggests that the composition of the intestinal microbiota can influence susceptibility to chronic disease of the intestinal tract including ulcerative colitis, Crohn's disease, celiac disease and irritable bowel syndrome, as well as more systemic diseases such as obesity, type 1 diabetes and type 2 diabetes. Interestingly, a considerable shift in diet has coincided with increased incidence of many of these inflammatory diseases. It was originally believed that the composition of the intestinal microbiota was relatively stable from early childhood; however, recent evidence suggests that diet can cause dysbiosis, an alteration in the composition of the microbiota, which could lead to aberrant immune responses..."