It’s time to rethink how we identify disease-causing microbes

At the turn of the last century, German physician Robert Koch identified four critical criteria for determining whether or not a particular microbe causes a disease. The ideas behind them were crucial for advancing medicine and formalizing the germ theory of disease. Over the last century, these postulates have been updated as medicine has advanced.

In what may end up being the most recent of these updates, biologists Allyson Byrd and Julia Segre propose some adjustments to these classic medical postulates intended to bring them in line with analytic techniques based on DNA sequencing and the most current understanding of bacterial communities. Just as the previous updates to Koch’s postulates did, these proposed amendments incorporate cutting-edge scientific knowledge and add nuance to our understanding of the causes of disease.

Koch’s original postulates are that, if a microorganism causes a disease, then: