Human blood prepared on a slideFLICKR, SMALLER.PATHOLOGICAL.CAMicrobiologist Thomas Luckey, who in 1972 estimated that the number of microbial cells in and on the human body outnumbers those carrying the human genome by 10 to 1, was wrong: people are not more microbe than human, scientists now suggest. According to new research from scientists in Israel and Canada, a 5”7’, 20-year-old man weighing 70 kilograms (154 pounds) likely harbors some 30 trillion human cells (the vast majority of which are red blood cells) and 39 trillion bacteria.
“The numbers are similar enough that each defecation event may flip the ratio to favour human cells over bacteria,” the researchers wrote in a paper posted to the preprint server bioRxiv last week (January 6).
“One-to-one is pretty impressive,” Judah Rosner, a molecular biologist at the National Institute of Diabetes and Digestive and Kidney Diseases who questioned the 10-to-1 ratio in a 2014 issue of Microbe, told Science News. “There’s as much of them as there is of us.”
Of course, the new estimate could be off by as much as 25 percent, the researchers noted, as it’s based on existing experimental data that could inform an assessment of human and microbial cell counts, such as estimates of bacteria in 1 gram of feces and ...
