My journalism career began in Walkerton, Ontario. I worked as a reporter there between 1989 and 1991. I can hardly imagine how stressful my job would be if I worked there now. That quiet rural community on the winding Saugeen River recently drew international attention because of a toxic outbreak of Escherichia coli infection. At least seven people, and possibly as many as 21, died of illness from a virulent strain of this common bacterium that invaded the town's drinking water.
In the most tragic way possible, this outbreak draws attention to the invisible but critical place microbes play in our lives. E. coli is a normal inhabitant of the digestive systems of humans and cattle. The infection likely originated in waste from farmland; Walkerton lies in the heart of cattle country.
The offending organism, E. coli O157:H7 is a rare mutation which may have originated in a dysentery epidemic in Mexico in the 1970s. Scientists speculate that a virus transferred a toxin-producing gene from a Shigella bacterium into a normal E. coli cell, which subsequently reproduced and spread into North American cattle.
An unseen world
What bewilders most of us is that all this witchery occurs at a level invisible to us. Single-cell organisms are usually invisible to the unaided eye. We live our lives oblivious to microbiology, but its impact is deeply felt. Not only did all life evolve from micro-organisms, but our lives are still totally dependent on them.
You may have heard that beetles are the most diverse of all living creatures. According to The Nature of North America by David Rockwell (Berkley Books, 1998):
Biologists have described about three-quarters of a million insects, an average of 3,500 a year since 1758, the year Linnaeus originated our modern system of nomenclature. Two of every five living organisms so far described are insects; about 40 percent of those are beetles.Estimates put the number of insect species in the tens of millions. But this number is dwarfed by the diversity of microbial species. "Every insect probably has at least one or two parasitic nematodes, protozoans, bacteria and viruses specialized to its type," Rockwell says. Scientists have described 4,200 species of bacteria alone and estimate this represents less than one per cent of their actual biodiversity. There are probably well over one million species of bacteria.
Survivors of extremity
Microbial ecologists say a gram of soil contains an average of one billion individual microbes representing several thousand species. They inhabit the deep
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