You can read about the guy here: http://www.livescience.com/52719-do-we-need-showers.html He uses soil bacteria from the Nitrosomonas genus, which can break down ammonia and product nitric oxide (NO). According to him horses have these bacteria on their skin. Using soap can destroy these bacteria on our skin and the proper recolonization can take months. So these are really sensitive microbes.
He claims that these bacteria were once part of the human skin microbiome, but was removed when people started to use soap.
I found some circumstantial evidence only:
The groups that'd had more contact with the modern world tended to
have less microbial diversity, the researchers found. The Yanomami in
the study had almost double the amount of bacterial diversity as the
people in the U.S., and about 30 to 40 percent more diversity than the
Guahibo Amerindians and Malawian participants, said study researcher
Jose Clemente, an assistant professor of genetic and genomic sciences
and medicine at the Icahn School of Medicine at Mount Sinai in New
This just shows that the biodiversity is much greater on the skin and in the gut of tribe people living in isolation from modern society.
I read a few years ago that tribe people have even soil bacteria on their skin, so it might be true, but I did not find more information about the concrete species living on the skin of these people, so it is inconclusive whether he is right or not. Taking shower is not necessary btw. if you can bear with the odor...