Since 1972, a has been widely quoted "fact" was that bacteria in our body outnumber our own cells by a factor of ten. The ratio is actually closer to 1:1 [nature.com]. In1972, Thomas Luckey published the estimate of 10:1, and the number has been widely cited ever since. The new paper is available online [biorxiv.org].
While this may be interesting, it's not too important. As Peer Bork of the European Molecular Biology Laboratory said, "It is good that we all now have a better estimate to quote, but I don’t think it will actually have any biological significance."