How many "Good" Microbes in humans?

[SysBio]

Hi all,

 

I think I have heard that the number of microbial cells (from other species) in humans actually outnumbers human cells....is this true?

 

To elaborate, can someone say what type of organisms these mainly are, and total number of cells and/or percentage of the human body they make up?

 

thanks for any information!

[CharonY]

Of course no one ever directly counted the cells. However adult humans consist of roughly 10 e12 cells. In the intestinal tract alone (where the highest amount of bacteria are found) there are around 10e14 bacteria.

The composition of bacteria varies greatly according the given habitat, of course.

[SysBio]

Thanks for those numbers....

 

however they dont make sense to me. How can the lining of the intestinal track have more cells than the entire body.....

 

Would it have to do with the idea that major portions of the intestinal track have folds in order to maximize surface area?....still its pretty mindboggling

[Mr Skeptic]

Bacterial cells are many many times smaller than human cells.

[SysBio]

oh yeah....very true

 

I still dont see how it adds up though, because I think bacterial cells are 10x smaller. But the remaining human body is surely more than 10x greater than the intestinal track.

 

I think the only way this can make sense is if the large surface area of the intestinal track is considered.

[DrDNA]

Paris Hilton or a regular person?

[Mr Skeptic]

oh yeah....very true

 

I still dont see how it adds up though, because I think bacterial cells are 10x smaller. But the remaining human body is surely more than 10x greater than the intestinal track.

 

I think the only way this can make sense is if the large surface area of the intestinal track is considered.

 

10X smaller in how many dimensions? If you consider an object that is 10X smaller than another in length, width, and height, you end up with something with 1000X less volume. So if you measure that the diameter of a bacteria is 10X smaller than that of a human cell, you end up with something 1000X smaller in volume.

[Psycho]

10X smaller in how many dimensions? If you consider an object that is 10X smaller than another in length, width, and height, you end up with something with 1000X less volume. So if you measure that the diameter of a bacteria is 10X smaller than that of a human cell, you end up with something 1000X smaller in volume.

 

The average bacteria is about 2x1x1 micrometers where as the average animal cell is about 20 micrometers in diameter.

 

So they are that much bigger.

[CharonY]

Also consider that the lumen of your gut is just a hole sometimes stuffed to the brink with bacterial cells (bacteria are the largest proportion of feces), whereas the rest of your body has a lot of cavities mostly filled with liquid (and relatively few cells).