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Microbiology · Chapter 1

Where Your Microbes Live

You carry about as many microbial cells as human ones, and every body site holds a different crowd. Tap a site to meet its normal flora. Then pick an event and run the clock. Watch what an antibiotic course does, and what one hand scrub does.

Your body, site by site dot size tracks the live count

Human microbiome map

You carry roughly 38 trillion microbial cells. That is about one microbe for every human cell you own. Most of them sit in your gut. Very few of them ever do you harm. The dot for a site shrinks when that crowd is knocked back.

What happens over three weeks pick a site

Population over 21 days
Resident flora Opportunists Transient flora

Each band is one part of the crowd. The purple band is the flora that live here. The red band is the trouble waiting for a gap. The gold band is what you picked up by touch. Drag the day slider and the bands move.

The human microbiomepick a body site to begin

What happens to the body

Day 0

Readings

—resident flora left waiting
Normal load here —
Different kinds living here —
Opportunists —
Transient flora —
Mostly on your sideNearly all of your normal flora are harmless or helpful. They make vitamins, crowd out invaders, and train your immune system. Tap a site on the body to see who lives there.
Worth holding on to: most infections that start in a care setting come from a person's own flora moved to the wrong place. Gut E. coli reaching the bladder is the classic case.