# How Many *E. coli* Cells Will It Take to Celebrate Our 100th Weekly Edition?

### We’re telling you now, it’s a lot.

Please permit us the smallest amount of navel-gazing this week as we write this, our 100th, weekly newsletter.

Yup, it was exactly 100 editions ago that we started pounding the keys to bring you what turned out to be a long and winding road through the world of microbiomes, microbiology, and – frankly – an awful lot of movements of the bowel (the entire focus of our inaugural newsletter, and a subject to which we frequently and happily return).

So, today, we thought it would be appropriate to adopt a theme of 100s.

We’ll also revisit a common bacterium that has made regular appearances over the past 100 weeks.

*E. coli* – or *Escherichia coli*, its full name – is a species of bacteria found in the environment, foods, and intestines of people and animals.

And, as it’s frequently used in experiments, it’s also found in one heck of a lot of microbiology labs.

Some strains of *E. coli* can make people sick, but most are harmless.

Right now, however, we’re more interested in an *E. coli* cell’s physical attributes.

So, we’ll begin by looking at how many *E. coli* cells it would take to form a line one hundred centimeters long, should they be positioned nose-to-tail.

Bacterial cells are pretty tiny, and a single cell of *E. coli* has a length of around two microns.

So, a sizable half million of them (approximately the population of Sacramento) would be needed to make a line one hundred centimeters long – for the non-metric, that’s about 39 inches.

Interestingly, like you probably knew we would, we crunched the numbers to find out how long a line the entire human population of Sacramento would actually make.

Standing rather snugly, one behind the other, this line would stretch from Fort Lauderdale to Key West – around 189 miles.

Like us, perhaps you’ve been in post office lines that felt a bit like this.

What about mass, though?

How many *E. coli* cells would make up a weight of one hundred grams?

Scientists, perhaps with extremely tiny sets of scales, tell us that a single *E. coli* cell has a mass of around 1 picogram, a picogram being one trillionth of a gram.

Doing the math, therefore, one hundred grams would contain 100 trillion bacterial cells.

Now, one hundred grams is about three and a half ounces. Approximately the weight of a deck of playing cards.

As for 100 trillion, well this is waaay more than the number of humans who have ever lived.

Almost 1,000 times more, in fact.

Sticking with our theme of 100s, and moving on to speed, we next wondered how long it might take an *E. coli* cell to travel 100 centimeters.

Not all bacteria are motive, but many are, and some remarkably so.

*E. coli’s* performance in this respect isn’t too shabby, as it can travel at the rate of 15 body lengths per second.

Now, Jamaica’s Usain Bolt currently holds the men’s world record for the 100 meters, which is 9.58 seconds.

However, an *E. coli* cell’s 15 body lengths per second is the equivalent of a six-foot human running 100 meters in a crazy 3.6 seconds.

So, relative-size for relative-size, Bolt is a mere idler compared to an *E. coli* cell.

However, size does indeed matter when it comes to actual, rather than relative, speed, of course.

And it would take an *E. coli* bacterium a theoretical nine hours to travel one hundred centimeters (just one meter).

We say “theoretical” because we conveniently ignore the fact that during those nine hours, these *E. coli* cells would be reproducing around 270 times (they do this approximately every 20 minutes).

And even if you’re a mere microorganism, the jury is out on whether you can reproduce while also running three times faster than Usain Bolt.

Finally, speaking of reproduction, how many offspring could a single *E. coli* cell have in, let’s say, one hundred hours?

After 20 minutes, one would become two, after 40 minutes two would become four, etc.

We start with one small cell, but after 100 hours, we’d have an extraordinary 2 to the power of 299 bacterial cells.

Thankfully, this kind of extreme growth would require perfect conditions and an unlimited supply of nutrients.

Fortunate, indeed, for after 100 hours of continuous reproduction, we’d be confronting a mass of *E. coli* weighing substantially more than our entire planet.

This is rather more than would fit in even the biggest, filthiest fridge.

Thank goodness for bacterial family planning, eh?

We sincerely hope you’ve enjoyed this week’s microbial meandering as much as we’ve enjoyed compiling it.

In the past hundred weeks we’ve covered subjects as diverse as **forensics and the microbiome**, **fecal transplants**, and, uh, f**latulence**.

And that’s just the Fs.

Many tell us they enjoy their weekly dose of good-humored microbiological illumination, so as long as we carry on getting positive feedback, we’ll carry on investigating and writing.

Ready for another 100 issues?

### More reading

How big is an *E. coli* cell and what is its mass?

Survival of Escherichia coli in the environment: fundamental and public health aspects