Feb 1, 2008


Microbiology TodayThe current issue (February 2008) of Microbiology Today includes a number of articles devoted to the microorganisms that live in our body. In an introductory article (Life on us), Robin Weiss writes:

"As an ecosystem, it has become clear that we are only part human, because a significant amount of our biomass is microbial. In demographic terms, microbes outnumber our own cells. While there are 1014 human cells in the average adult, there are probably ~1015 bacteria and >1017 viruses associated with the human body. In terms of genetic diversity and complexity, the microbial metagenome of humans may be greater than the 3×109 base pairs of human DNA."

So, we are superorganisms, composed of many organisms. In fact, it seems that the collective genome of our microbial symbionts (the microbiome) may contain over 100 times as many genes as our own genome, and provides traits that humans did not need to evolve on their own (from an article in Science).

In Life on us, the author makes another thought-provoking remark:
"Thus while we share >98 % host DNA sequence similarity with the chimpanzee, the microbial and viral species that live on or on us are only ~50 % shared with the great apes."
Definitely, those tiny passengers in our bodies should have influenced our evolution. How much of our "humanity" (whatever makes us different from other apes) do we owe to our microbial cells??


A collection of related links (in chronological order, newest first):

Etymological addendum:

Anthropomicrobiology = anthropo + microbiology
Microbiology = micro + biology
Biology = bio + logy

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