If You Had Really Good Eyesight, Could You See a Single Bacterium?

Making microscopic microbes visible.

It’s no accident that we refer to an extremely thin or fine line as a “hairline”, as it’s generally accepted that the smallest object visible to the human eye is around 50 microns in width.

And that’s about the diameter of an average human hair, which a good eye should be able to distinguish at a viewing distance of around 9 inches.

What, then, are the chances of you being able to see a single bacterium without a microscope?

Pretty impossible actually, unless you happen to be in Namibia in south-west Africa, that is.

You see, scientists working there in 1999 discovered a monster microbe called Thiomargarita nambiensis, which researchers agree is the world’s biggest bacterium.

An individual one of these can grow up to 0.75 mm wide – huge for a microbe – which it achieves by possessing a hydrogen sulfide–filled cavity that can blow up like a stinky balloon.

Thiomargarita means “sulfur pearl.”

In Latin, margarita means pearl, nothing to do with the tequila, triple sec and lime juice cocktail.

Besides the giant anomaly Thiomargarita nambiensis, which has an incredible three million times the volume of a normal bacterial specimen, you won’t be able to see most individual bacteria without a microscope that has a magnification of at least 1,000x.

Even then, bacterial cells aren’t easy to distinguish from their background without first being dyed with a stain such as crystal violet, safranin (red), or methylene blue.

How else can we see bacteria, then?

Well, rather like the way you can make out a whole head of hair at a much greater distance than you can a single strand, bacteria become considerably more visible when they’ve developed into a colony, as they do when they’re grown in a Petri dish, for example.

Petri dishes are those shallow, circular containers in which microbiologists cultivate bacteria, and they were named after their inventor Herbert Dish.

No, of course not. That would just be silly.

His name was actually Julius Richard Petri, a German researcher who worked as an assistant to Robert Koch, generally acknowledged as the father of bacteriology.

Koch may have been the most revered of the two but it was Petri, and not Koch, who was celebrated with a Google Doodle in May 2013.

Incidentally, when bacteria are grown in a Petri dish, it first needs to be partially filled with a warm liquid containing agar and a mix of specific ingredients that may include nutrients, blood, and salts.

It sets as it cools.

Agar is a jelly-like substance obtained from algae, reputedly first discovered in 17th-century Japan when an innkeeper threw out some surplus seaweed soup on a bone-chillingly cold night, then noticed in the morning that it had gelled after its thorough freezing.

Someone who makes unusual use of Petri dishes is the “bio-artist” Zachary Copfer, who has invented a process he calls bacteriography.

It enables him to produce the equivalent of a photographic print by exposing a bacteria-filled dish to radiation, through a negative.

The radiation kills the bacteria in the white spaces of an image, then those in the black spaces are “developed” via incubation.

Actually, colonies of bacteria can grow pretty enormous.

Snorkelers in the shallow seas off the Greek island of Zakynthos found what they fondly imagined were ancient archaeological remains.

Looking a little like giant donuts, with a diameter of around 3 feet, observers guessed they must be the base of building columns, possibly dating back to the Hellenistic era, a couple of hundred years BC.

The trouble was, there were no other remains – such as broken pottery – anywhere near them.

However, close analysis revealed that these artifacts turned out to be bacteria-caused.

As gas bubbled from the seabed, methane-loving bacteria consumed it, changing the chemistry of the seawater.

In turn this caused minerals to be precipitated out of the water, forming a rock known as dolomite, in a process called concretization.

In fairness, these giant donuts aren’t really made from bacteria, but it was microbes that created them, possibly during the Pliocene epoch over 2.4 million years ago.

In general, however, we should remember that bacterial cells are teeny.

A million of some species would fit on the head of a pin.

Mind you, microbes are actually ginormous when compared to the latest size of a transistor on an integrated circuit.

Although some believe transistors are unlikely to get very much smaller (sorry Mr. Moore), you could fit almost 300 of them in the length of a single E. coli cell.

Further reading


Ancient Civilization of Microbes, Not Greeks, Built ‘Lost City’

Aquaboffins sink lost Greek city theory

Are any bacteria visible to the naked eye?

Backpacking bacteria

Bacteria Glow Under UV

Celebrating Julius Richard Petri – A Man, A Dish, A Google Doodle

Exhumed hydrocarbon-seep authigenic carbonates from Zakynthos island (Greece): Concretions not archaeological remains

Julius Richard Petri

Smaller Than Microscopic

Staining Bacteria (1)

Staining Bacteria (2)

The Fascinating World of Bacteria


Zachary Copfer