What Are The Different Shapes Of Bacteria?

If you were to look at a whole range of different bacteria under a microscope, you may notice that several different strains of bacteria actually have something in common.

That is of course the shape that they appear in! Some types of bacteria appear very similarly to one another, and it’s all down to the shape that makes up their overall structure.

But why are there different shapes of bacteria? And what are the different shapes of bacteria, anyway?

What Are The Different Shapes Of Bacteria?

Today, we’re going to take a closer look at the different shapes of bacteria to help you learn a little more about each different one.

Even though there are lots of different factors that come into play here, pretty much all of the bacteria that exist in the world can be sorted into 5 distinct categories based entirely on their shape.

Let’s take a look at the different shapes of bacteria and see how we can tell them all apart!

What Are The Most Common Shapes Of Bacteria?

While some scientists will argue that there are actually 3 most common shapes of bacteria, we’re going to cover the 5 different common shapes of bacteria.

The last 3 of these tend to be lumped in a category together, but we shall cover each of them in more detail so you can see how they differ from one another.

Bacillus (Rod-Shaped)

One of the main shapes of bacteria is the rod shaped form, or bacillus if you wanted to use its scientific name. The bacillus shape is in the form of a rod, and it can differ in terms of size.

The rod shaped bacteria tends to be between 0.5 micrometers and 1 micrometers in width, and then between 1 micrometers up to 4 micrometers in length.

Some of the most common types of bacteria that have the bacillus shape are E.coli and Bacillus anthracis, which is the bacteria that is known to cause anthrax.

If you were to look at this rod shaped bacteria under the microscope, you would notice that it is able to form a chain of different bacteria.

The rod shapes will join up together from end to end to form these chains, which are referred to as streptobacillus. 

If there were only two cells of bacteria joined end to end, this is called diplobacilli.

And if the bacteria has joined together via the longer sides, so that they all sit parallel to each other, these are called palisades.

Bacillus can of course occur as a single celled organism, too.

A different type of bacillus exists which is a kind of cross between bacillus and coccus bacteria, known as coccobacillus.

These appear as an oval shape when compared to the standard rod shapes and spherical shapes of the other two shapes of bacteria.

What’s really fascinating about bacillus bacteria is that they are very heat resistant, and can survive in temperatures up to a whopping 788 degrees Fahrenheit!

Alongside being extremely heat resistant, these types of bacteria can spend years living dormant, and are resistant to disinfectants and radiation.

Coccus (Spherical-Shaped)

The second most common shape of bacteria is the coccus bacteria, also known as the spherical shaped bacteria. This is because the bacteria appears as a circle.

It can exist as a single celled organism, or it can form groupings with other coccus bacteria cells.

There are different names for these forms of bacteria depending on where exactly the coccus bacteria have joined together, and what shape they have.

A single cell is of course called monococcus. Where 2 of these coccus cells have joined together, this is referred to as diplococci.

If 4 cells were to join together in a square shape, it would be called a tetrad. If another of these tetrad cells were to join together – with 8 coccus cells in total – forming a cube shape, this is called a sarcina.

The coccus cells can of course also form a long line, which would be called streptococci.

And the last form that is given its own special name is if the coccus cells were to form a triangle shape, which is then called staphylococci.

Spirillum (Spiral-Shaped)

Spirillum (Spiral-Shaped)

The spirillum bacteria is typically recognizable as a spiral shape.

Even though it tends to be lumped in with the vibrios and spirochaetes shapes, it has its own distinct shape that is recognizable when looked at under the microscope.

To differentiate itself from the other two spiral shapes, the spirillum bacteria tends to be formed using a stiff, thick spiral.

It also tends to have flagella at the end of it, which gives it the appearance of having multiple tails.

When there is only one cell of the spirillum bacteria, this is typically called a spirilla.

This type of bacteria is normally found in aquatic environments, where they can use their flagella to help them swim at a rapid pace.

These bacteria tend to differ in sizes from a diameter of 0.4 micrometers up to 1.4 micrometers, and then between 1.2 micrometers and 75 micrometers in length.

What makes them so easy to confuse for the other types of spiral shaped bacteria is that the shape can differ depending on the bacteria in question.

The spiral can appear as a single turn, or even as a more detailed helical shape which will have several complete turns.

Vibrios (Comma-Shaped)

One of the other most common shapes of bacteria is the vibrios bacteria, which is also known by its comma shape. The bacteria cell also has between 1 to 3 flagella on the end of it, appearing almost like a tail.

Even though the main body may appear as a rod shape, it is typically curved into the shape of a comma.

They use their flagella to move around the place, which helps to give them a competitive edge in their natural environment.

There are several diseases which are harmful to humans and animals which use the vibrios bacteria shape, including cholera.

Spirochaetes (Corkscrew-Shaped)

So if the spiral shape can also be a corkscrew shape, how does that make the spirillum different from the spirochaetes corkscrew shape?

Well the main difference is that even though the spirillum bacteria is recognizable from its spiral shape, this spiral shape is rigid, and doesn’t really change or move all that much.

However, a spirochaetes corkscrew shape is much more pliable, and tends to be very flexible and thin when compared to the spirillum bacteria. 

What really makes it stand out compared to the spirillum bacteria is that it has endocellular flagella, which basically means the flagella of the cells are inside it, rather than on the outside.

There tends to be between 2 to 100 endocellular flagella depending on the spirochaetes bacteria.

Similar to spirillum, the spirochaetes bacteria tends to be found in aquatic environments, as well as in blood, or other types of liquid environment.

Two of the most common diseases that are caused by the spirochaetes bacteria include syphilis and Lyme disease.

Why Are There Different Shapes Of Bacteria?

So now that we know a little bit more about the different shapes of bacteria, you will of course be wondering why there are so many different shapes!

This is of course because different physical features of all the different types of bacteria can help the individual bacteria to cope with certain environments and conditions.

Let’s take a look at the spiral shaped bacteria for example. These typically have flagella – whiplike tails – on them, or are more flexible.

These flagella of this flexibility can be used to help the spiral bacteria move through their native liquid environments.

If they weren’t as flexible or didn’t have the flagella on them, this would make it harder for the bacteria to move around and go about its business.

This theory can also be applied to the other shapes of bacteria that we have covered in more detail above.

These certain details and physical attributes give the different bacteria more of an advantage in their natural environment.

In Summary

So there you have it! You now know that there are at least 5 different shapes of bacteria.

These are the rod shaped bacteria bacillus, the spiral shaped bacteria spirillum, the spherical shaped bacteria coccus, the comma shaped bacteria vibrios, and the corkscrew shaped bacteria spirochaetes.

They each have their own unique properties which then relate to the different types of bacteria.

If you wanted to be really pedantic about it, you could even narrow the most common shapes of bacteria down to 3 shapes: bacillus, coccus, and spirillum.

Some scientists include the vibrios, spirochaetes, and the spirillum shapes as a single shape.

There are so many different types of bacteria throughout the world, but all of them can be categorized into at least one of the shapes that we have covered in more detail above.

Jennifer Dawkins

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