Bacterial Cell Morphology & Arrangements: Study with Video Lessons, Practice Problems & Examples

Bacterial cell morphology refers to the shape of individual cells, primarily categorized into three types: coccus (spherical), bacillus (rod-shaped), and spirillum (spiral). Cell arrangements, such as diplococci (pairs), streptococci (chains), and staphylococci (clusters), describe how these cells organize after division. Bacilli can form arrangements like single bacilli, diplobacilli (pairs), and streptobacilli (chains). Spiral bacteria include vibrio (curved), spirillum (corkscrew), and spirochete (flexible). Understanding these classifications is essential for identifying bacterial species and their behaviors in various environments.

Bacterial Cell Morphology & Arrangements

In this video, we're going to begin our lesson on bacterial cell morphology and arrangements. And so first, we need to distinguish between the two terms, morphology and arrangement, which are two terms that we're going to be using a lot over the next few videos. And so cell morphology is referring to the overall shape of individual cells. And so really the term morphology is just a fancy term that means shape. Now cell arrangement is a little bit different because cell arrangement does not refer to the shape. Instead, cell arrangement refers to the organization or the alignment of groups of multiple cells. And so what we'll see moving forward is that there are 3 main types of morphologies or 3 main types of shapes. But there are many different types of arrangements. And so we'll go through some of those as we move forward in our course. And so I'll see you on our next video.

Types of Bacterial Cell Morphology

This video, we're going to begin our lesson on the types of bacterial cell morphology. Bacterial cells typically range between 0.2 to 2.0 micrometers in diameter and about 2 to 8 micrometers in length. Bacteria are very small. Now, there are three main bacterial cell morphologies that we have numbered down below: 1, 2, and 3 over here.

The first bacterial cell morphology is coccus, and coccus is circular shaped. As you can see down below, the shapes of some bacteria are circular, as shown here. Staphylococcus aureus is an example of a bacterium that has circular morphology, coccus morphology. The next one that we have here is bacillus. Bacillus is a rod-shaped morphology. You can see here that it creates these elongated rods, as shown here. An example of this is actually Escherichia coli, or E. coli, which creates these rod shapes or this bacillus morphology.

Last but not least, the third main type of morphology that bacteria can take is spirillum. Spirillum is a corkscrew shape. You can see it has this spiral or corkscrew shape, as shown here in this image. An example of this is Spirillum minus, a specific bacterium that has this corkscrew shape or the spirillum morphology. You can see that we have the little corkscrew over here just to remind you of spirillum being a corkscrew shape or this spiral shape, as you see like that.

This here concludes our brief introduction to the types of cell morphologies or the types of shapes that bacteria mainly take on. As we move forward in our course, we'll start to talk more about the arrangements that the bacteria take. Do not confuse morphology with arrangement. Morphology refers to the shape either coccus, bacillus, or spirillum, and arrangement refers to the organization or the alignment of multiple cells, which we'll talk about later. So, I'll see you in our next video.

Cocci Bacterial Cell Arrangements

In this video, we're going to focus on cocci bacterial cell arrangements. Cocci is the plural form of coccus, which, recall from our previous lesson video, is one of the 3 main types of bacterial cell morphologies. Cocci refers to a circular shaped morphology. The cocci are circular shaped bacterial cells that can be either round, spherical or flattened like a hockey puck. The cocci can have many different arrangements. These cocci cells can be arranged or organized in many different ways after cell division. It's important once again not to confuse morphology with arrangements. Recall that morphology refers to the shape. Notice that all of these cells down here all have the same cocci or coccus shape, which is circular. The shape here, or the morphology, is not to be confused with the arrangement, and the arrangement is how these cells are arranged or organized. Notice that all of these are different arrangements even though they all have the same morphology, the same shape. The first arrangement that we have up here at the top left is diplococci. Notice that the cocci root here is referring to the morphology, the circular shape. The di here is a root that means 2. Diplococci refers to 2 cells that remain attached after cell division. When a cell divides, it divides into 2 cells as you see here, but they remain attached to create this diplococci formation. Neisseria gonorrhoea is an example of a bacteria that takes on this diplococci arrangement. The next arrangement that we have over here is streptococci. Once again, the cocci root here is referring to the morphology, the circular shape. The root strepto is really important here. Strepto is a root that refers to a chain. Streptococci are going to have a chain-like pattern of multiple cells. You can see that they are cocci shaped, they are circular, but they create this chain, this long chain of cells. That is what makes them have that strepto arrangement. Notice that Streptococcus pyogenes is an example of a bacteria that creates this chain-like arrangement, the streptococcus arrangement. The next arrangement that we have here is the tetrad. Tetra is a root that means 4. This is going to be a cluster of 4 cells that are arranged on the same plane. You can see these four cells are all coccus. They're all circular shaped, but they are arranged in a tetrad where there are 4 cells in the same plane. You can see that Micrococcus luteus is an example of an organism that creates this tetrad arrangement. You can see there's a tetrad that's right here which is kind of overlapping with this other tetrad that you see here. The tetrad can be somewhat off a little bit. For the most part, you can see that they can create this tetrad arrangement. The next arrangement that we have here is sarcina. Sarcina is a cluster of 8 cells arranged into a cube. You can see here that there is this cube-like arrangement and there are 8 cells that participate in this cube-like arrangement. Sarcina ventriculi is an example of a bacteria that has this sarcina arrangement. The last arrangement that we have here is staphylococci, which once again you can see the cocci root here is referring to the coccus or circular shaped morphology. But then the staphylo root, which is really important here, is not to be confused with strepto. Recall strepto is a chain-like arrangement. Whereas staphylo refers to a cluster. This refers to a cluster of many cells in an irregular pattern. They don't really make a specific pattern that's recognizable. You can see here we have this big cluster of these circular shaped bacteria. The cluster here is what makes this arrangement staphylo. You can see that Staphylococcus aureus is an example of a bacteria that has this particular arrangement. This here concludes our brief lesson on cocci bacterial cell arrangements. We'll be able to get some practice applying this as we move forward in our course, and we'll also get to learn a lot more about different types of arrangements as well. I'll see you all in our next video.

Streptococcus bacteria have what shape?

• A. Single thin cells that are bulbous at one end.
• B. Chain of spiral cells.
• C. Cluster of rod-shaped cells.
• D. Cluster of spherical cells.
• E. Chain of spherical cells.

Bacilli Bacterial Cell Arrangements

In this video, we're going to focus on the bacilli bacterial cell arrangements. Bacilli is the plural form of bacillus, which, recall from some of our previous lesson videos, is one of the 3 main types of bacterial cell morphologies where bacteria take on a rod shape. Bacilli, recall, are rod-shaped bacterial cells. They can only divide across their short axis; they cannot divide along their long axis. For example, if we're looking at a bacilli cell like what you see down here, it can only divide along its short axis. So it can only divide this way; it cannot divide along the long axis. Because bacilli can only divide in one plane, they have fewer possible arrangements than the cocci, which can divide in many different planes. Let's take a look at some of these arrangements for the bacilli.

First, we have a single bacillus, which is actually a single cell, and this is the most common arrangement for bacilli bacteria. You can see that here we have a single cell that has this rod shape, this bacillus morphology. An example of this is E. coli or Escherichia coli. The next arrangement that we have over here is diplobacilli. The root di means 2, and so this arrangement occurs when there are 2 cells that remain attached after division. Notice that this cell divided along its short axis to create 2 cells here, resulting in a chain of 2; that's why it's called diplobacilli. An example of this is Bacillus megaterium, which you can see has a chain of 2 cells in that arrangement.

The next arrangement that we have is streptobacilli. The root strepto refers to a chain, and so this involves bacilli in a chain-like pattern of multiple cells. You can see here there's a chain of multiple bacilli all linked up in a long chain here, and that's why it is streptobacilli. An example of this is Anthracis. You can see the images here, and it has all of these bacterial cells linked in a chain.

Last but not least, what we have over here on the far right is coccobacilli, which is really just a mixture of coccus and bacillus in a diplo format. These are going to be short rod-shaped ovals, or short ovals, that can appear as diplococci. They look a lot like diplococci, and it's very difficult to tell the difference between them unless you're an expert. However, they are slightly different, and they have somewhat of a merge between the coccus and the bacillus. An example of this is Coxiella burnetii, whose arrangement is somewhat of a diplo, but the morphology is a mixture between coccus and bacillus. We refer to these as coccobacilli.

This here concludes our brief introduction to bacilli cell arrangements. We'll be able to get some practice and learn more about arrangements as we move forward in our course. See you all in our next video.

What is the morphology of the cells in the image below?

• A. Diplobacilli
• B. Streptobacilli
• C. Cocobacilli
• D. Streptococci

Spiral-shaped Bacterial Cells

In this video, we're going to focus on spiral-shaped bacterial cells. Spiral-shaped cells can actually have a few varied morphologies or shapes that are never completely straight. Down below in this image, we're showing you 3 different morphologies of spiral-shaped cells. The first one on the far left is Vibrio, which is really a bent-shaped short curved rod. You can see that it has this bent shape here. It's not completely straight, and it's barely a spiral, but it is going to create this curve here that is the beginning of a spiral. Vibrio cholerae is an example of a bacterium that takes on this vibrio shape. These bacteria are curved as you can see here in this image.

The next one that we have here is spirillum, which we already talked about in some of our previous lesson videos. These are curved rods that actually form a full spiral. This right here resembles a corkscrew and is forming a spiral shape. Once again, Spirillum minus is an example of a bacterium that has that corkscrew or spirillum shape.

The third one that we have over here is very similar to the spirillum. The difference is, the spirochete, which is this last one here, is going to be much longer than spirillum. Not only is it much longer, but it's also going to have more flexible cells. The spiral will not be as tight since it is more elongated. You could see here it does have this curved spiral shape, but it is much more elongated, and it is going to be much more flexible. Borrelia burgdorferi is an example of a bacterium that takes on the spirochete morphology.

This here concludes our brief lesson on spiral-shaped bacterial cells. Once again, we'll be able to get some practice as we move forward. So I'll see you all in our next video.

Vibrio cholerae causes the disease cholera. Based on the name of the bacterium, what is its shape?

• A. Spherical.
• B. Straight cylinder.
• C. Curved rod
• D. Chains of cocci.
• E. Chains of rods.

Which of the following is mismatched:

• A. Vibrio - comma-shape.
• B. Coccobacilli - intermediate between round and rod.
• C. Coccus – round.
• D. Bacillus - flexible and wavy.
• E. Spirillum - corkscrew-shape.

A chain of rods is referred to as ______________, whereas a curve shaped rod is termed _______________.

• A. Coccobacilli; bacilli.
• B. Streptobacilli; vibrio.
• C. Streptococcus; comma.
• D. Bacilli; spirochete.
• E. Diplobacilli; vibrio.

What type of cell is shown in the image below?

• A. Staphylobacilli.
• B. Streptococci.
• C. Staphylococci.
• D. Streptobacilli.

What type of cell arrangement is shown in the image below?

• A. Streptococci
• B. Vibrio
• C. Sacrinae
• D. Tetrad
• E. Single bacillus

Match the following cell morphologies with the correct description:

1) ______:Diplobacilli                     A. Long spiral with flexible cells.

2) ______:Streptococci                  B. Single rod-shaped cell.

3) ______:Vibrio                             C. 2 rod-shaped cells that remain attached.

4) ______:Diplococci                     D. Cluster of 4 spherical cells arranged on one plane.

5) ______:Spirochete                    E. 2 spherical cells that remain attached.

6) ______:Tetrad                            F. Comma-shaped, short & bent cells.

7) ______:Single Bacillus              G. 2 short rod-shaped (or oval) cells that remain attached.

8) ______:Coccobacilli                  H. Chain-like pattern of spherical cells.

9) ______:Staphylococci               I. Cluster of 8 spherical cells arranged like a cube.

10) ______:Spirillium                      J. Curved rod that forms a spiral.

11) ______:Sarcinae                        K. Chain-like pattern of rod-shaped cells.

12) ______:Streptobacilli                L. Cluster of many spherical cells in a randomized pattern.

Okay, everyone. Here we have a giant review question that goes over all of the different morphologies of bacteria that we've talked about. I recommend attempting this one on your own and seeing what you get right and what you get wrong so you know what you need to work on. Okay? So do this one on your own, then let's start this video. Okay. So let's get started. So the way I'm going to do this is I'm going to look at all the definitions first and then try to find where that definition belongs. So let's start with definition a. A long spiral cell with a long spiral morphology with flexible cells. Okay. So this is one of the spiral types of morphology. There are only 3. And the one with flexible cells is going to be a spirochete. So that means a belongs with 5. So that's done with that one. Answer or definition b says single rod-shaped bacterium. So, what is a rod-shaped cell? Remember that term is bacillus. So let's have a look. Single bacillus, number 7. So we're gonna put b there. Okay. C. 2 rod-shaped cells that remain attached. So they're rod-shaped, so it should be bacillus because it's 2. We're gonna probably have the prefix di in there, which means 2, and they're gonna remain attached. So answer choice 1 looks good. Diplodia meaning 2, bacillus meaning rod shape. So diplobacillus, answer c goes there. Okay. D, a cluster of 4 spherical cells arranged on one plane. Okay. So spherical cells have what term? Cockey or coccus. Right? Cluster, so it's a very particular arrangement, and there's gonna be 4 of them. Okay. The funny thing about the cluster of 4 spherical cells is that in the name, Coccus isn't in there. It's just called a tetrad. And tetrad means 4, and there's only one arrangement with 4 particular cells. So, hopefully, that's helpful. So that means d goes with 6. So we're done with that one. E, 2 spherical cells that remain attached. Okay. Spherical, again, we talked about this. Cockey or coccus, and 2 specific ones. So you should see the term di, meaning 2. So let's have a look and okay. 4, diplodid caucus. So 2 coccus cells that remain attached. So that's where we're gonna put e. Okay. F, comma-shaped short bent cells. Comma-shaped cells are gonna be one of the 3 different types of spiral morphologies. Remember, it has a very unique name, Vibrio, so f goes with 3. So we're done with that one. G, 2 short rod-shaped or oval cells that remain attached. Okay. So rod-shaped/oval makes me think of that morphology that has the cells that are kind of in between rod and circular shaped. Right? So this name is going to have the name for rod and spherical together. So this one goes with cocobacillus or cocobacillus because coccus means round or spherical and bacillus means rod. So this is a combination of spherical and rod-shaped cells. So g is going to go here. Alright. What about h? A chain-like pattern of spherical cells. We know spherical is going to be coccus, and we know chain-like has a very particular prefix, which is going to be strepto. So we're looking for streptococcus or streptococci, and that's going to be 2. So we're going to put h here because strepto means chain, cockey means spherical. So let's get rid of h. Okay. Onto I. A cluster of 8 spherical cells arranged in a cube. Okay. So this is going to be similar to the tetrad, but remember tetrad means 4 and this answer has 8 cells. So what is this going to look like? This also has a very unique name and I is gonna go with 11, which is Sarsinae or Sarsinae, which is basically 8 cells, spherical cells, round cells arranged in a cube-like shape, very unique shape. Okay. What about J? A curved rod that forms a spiral. Okay. So this is going to be the definition of a spiral shape and the only spiral-shaped morphology that is left is going to be spirillum. So the correct answer for this one is j goes with 10, and it is pretty much a perfect spiral. So that's where that one goes. Okay. Almost done. K, chain-like pattern of rod-shaped cells. So we already know the prefix for chain-like, that's going to be strepto. And what is rod-shaped? Bacillus. So streptobacilli is what we're looking for, which is going to be 12. So we're going to put k here because strepto means chain, bacillus means rod. Alright, the last one. A cluster of many spherical cells in a randomized pattern. So remember that spherical cells can come in 3 different types of clusters, the tetrad, the sarsenae, and a random arrangement of spherical cells, which is going to be staphylococci. So that's gonna be l here. Alright. We finished. We're done. These are all the different morphologies that we talked about. I think this is a really great practice question whenever you need to review these different types of morphologies. Okay, everyone. Let's move on to our next video.

Here’s what students ask on this topic:

What are the main types of bacterial cell morphology?

The main types of bacterial cell morphology are coccus, bacillus, and spirillum. Coccus refers to spherical or circular-shaped bacteria, such as Staphylococcus aureus. Bacillus describes rod-shaped bacteria, like Escherichia coli. Spirillum refers to spiral or corkscrew-shaped bacteria, such as Spirillum minus. These shapes are fundamental in identifying and classifying bacteria, as they often correlate with specific bacterial species and their behaviors in various environments.

How do bacterial cell arrangements differ from cell morphology?

Bacterial cell morphology refers to the shape of individual cells, such as coccus (spherical), bacillus (rod-shaped), and spirillum (spiral). In contrast, cell arrangements describe how these cells organize after division. For example, diplococci are pairs of spherical cells, streptococci form chains, and staphylococci create clusters. Bacilli can form single cells, pairs (diplobacilli), or chains (streptobacilli). Understanding both morphology and arrangement is crucial for identifying bacterial species and their potential behaviors.

What are the different arrangements of cocci bacteria?

Cocci bacteria can arrange in several ways: diplococci (pairs of cells), streptococci (chains of cells), tetrads (groups of four cells in the same plane), sarcinae (groups of eight cells in a cube), and staphylococci (irregular clusters). Each arrangement results from the way cells divide and remain attached. For instance, Neisseria gonorrhoeae forms diplococci, while Staphylococcus aureus forms staphylococci. These arrangements help in identifying and understanding the behavior of different bacterial species.

What are the characteristics of spiral-shaped bacteria?

Spiral-shaped bacteria include three main morphologies: Vibrio, Spirillum, and Spirochete. Vibrio bacteria are short, curved rods, like Vibrio cholerae. Spirillum bacteria form a full spiral or corkscrew shape, such as Spirillum minus. Spirochetes are longer, more flexible spirals with a less tight coil, exemplified by Borrelia burgdorferi. These shapes are never completely straight and are essential for identifying specific bacterial species and understanding their motility and pathogenicity.

What are the different arrangements of bacilli bacteria?

Bacilli bacteria can arrange in several ways: single bacillus (individual rod-shaped cells), diplobacilli (pairs of cells), streptobacilli (chains of cells), and coccobacilli (short rods that resemble cocci). For example, Escherichia coli typically appears as single bacilli, while Bacillus megaterium can form diplobacilli. These arrangements result from the way bacilli divide along their short axis and help in identifying and classifying bacterial species.