Hi, in the last lecture the characteristics of cells and viruses, we have discussed that all living organisms are made up of cells. Now, we will see that there are two basic cell types in nature, the prokaryotic and the eukaryotic cells. prokaryotes are organisms that have prokaryotic cell, and eukaryotes are organisms that have eukaryotic cell structure. The study of prokaryotes has been divided into two parts. This lecture will focus on prokaryotes in part one. Here is an overview of the study of prokaryotes part one and two.

We will first go over the characteristics of prokaryotes the taxon and examples of programs Riyadh's then we will look in detail the structure of prokaryotes going from the outermost parts to the innermost parts of the prokaryotic cell, we will study the external structures, the cytoplasmic membrane, the cytoplasm and the internal structures. In part one, we will first go over the characteristics of prokaryotes, taxon and examples of prokaryotes. Then, we will look in detail the external structures of the prokaryotes which are the capsule shown here in orange the Pillai and the FIM ri are shown as blue lines. over the surface of the bacteria the flagella shown in dark orange, and the cell wall shown in yellow. we're choosing the bacteria as the main representative of the prokaryotic cell. But first let us look at the characteristics of prokaryotes.

By definition the word pro means before and carry out means nucleus. prokaryotes are microorganisms that existed before there was a nucleus in terms of evolution. prokaryotes therefore do not have a nuclear membrane surrounding their genetic material that is the DNA. The region where the DNA is found is called the nucleoid. prokaryotes also have no membrane bound organelles in their cytoplasm such as the mitochondria. Or in other words, they lack a number of internal structures that are bound with the phospholipid membrane.

The DNA are the chromosome of the prokaryotes is small and circular, double stranded. Some prokaryotes also have plasmids, which are separate from the chromosomal DNA and replicate independently from the chromosome. Overall, prokaryotes are relatively small, around one micro meter are smaller in diameter and simple micro organisms compared to eukaryotes. Now that we have studied the characteristics, let us move on to the taxon texts. sodomy is the science of classification of organisms and attacks on is a category or a group of organisms that have shared characteristics. So, in the classification of organisms prokaryotes are found in two main groups or domains, the domain bacteria and the domain archaea.

Archaea are known to predate bacteria in terms of evolution. The main difference between these two domains are that in the type of lipids in the cytoplasmic membrane, that are found in each of these domains, and in the chemistry of the cell walls, which we will look into detail later on. Shown here are a few examples of bacteria and archaea. The first one is streptococcus pneumoniae and the second Escherichia coli. The third Staphylococcus aureus are examples of bacteria. For archaea we have sulfur Lobos, which is a hyper thermal file meaning it survives in extremely high temperatures and a methanol Gen which is a methane producing archaea.

Let us start with the capsule or the glycol calyx as the external structure, other external structures that we will focus on are the pillar and embryo, the flagella and the cell wall. In each of these, I'll be showing images of the structures and going over The function and the types if needed, and also the differences between bacteria and archaea and between Gram negative and gram positive bacteria. Let us start with the capsule or glyco calyx. glyco means sugar and calyx means cup glyco calyx is composed of polysaccharides polypeptides are both the glyco calyx is produced inside the cell and then extruded onto the surface of the cell. If the glyco calyx is firmly attached, it is called a capsule if it is loosely attached, and if it tends to be water soluble, it is called a slime layer. glycolic stands to be found in pathogenic bacteria meaning bacteria capable of causing disease.

Slime layers help with attachment to surfaces. An example of this is a bacteria That colonizes the oral cavity. capsules, on the other hand help prevent desiccation and help the bacteria and resisting and Gulf meant by defensive cells, also known as the process of phagocytosis. Examples are streptococcus pneumoniae, and klebsiella pneumoniae. Panel a shown here is a scanning electron microscopy of three kinds of bacteria, namely, streptococcus pneumoniae, klebsiella pneumoniae, and bacteroides fragilis. Panel B is a negative stain for capsules of streptococcus pneumoniae, and klebsiella pneumoniae.

So, what you see in dark blue is the bacteria itself Inside the capsule, and so everything which is white and surrounding the bacteria is the capsule shown by these blue arrows. The capsule is wide because the dye cannot penetrate the thick polysaccharide layer of the capsule because of the looseness of the slime layer. The slime layer is easily washed off and thus cannot be stained in the case of Bacteroidetes plage fragilis. Finally shown in the bottom panel, the panel see are the transmission electron microscopy images for both the capsules of streptococcus pneumonia and klebsiella pneumoniae and the slime layer of bacteroides fragilis fame Ria and Philae shown here. As an example, our external rod like projections made up of protein, they extend several micro meters from the cell surface. The main functions are adherence conjugation and biofilms.

It is now noteworthy to mention that Pillai and FIM re are used interchangeably by some scientists but not by others. For ambria help with adherence to the environment, some scientists name The FIM Ria that helped with adherence to another bacteria for the purpose of transfer of genetic material as conjugation Pillai or sex belie. Therefore, Pillai are also known as conjugation Pillai. The words therefore Pillai and fibia can be used interchangeably. However, Phil I tend to be longer then for embryo shorter than flagella and tend to transfer the DNA from cell to cell. Example of a bacteria that has been really is nice area gonorrhea, the bacteria has several fingers that enable it to colonize the reproductive tract by attachment.

Here finger is a representation of inria finger bees and electron micro graph of equalize showing FIM Ria see, is showing sex belie as these long allegations. The other name for the conjugation Pillai in contrast to the smaller FIM Ria that are found all over the surface of the bacteria and which are much more in number than the sex we live in D. You can see both FIM Ria and the conjugation Pillai. Again, the conjugation pillars literally pulls the bacteria close. Similar to pulling something with a rope in order to have the transfer of genetic material flagella are long structures that extend beyond the surface of a cell including the glyco calyx. And they propel the cell through its environment, the singular flagella is flagellum. In terms of structure, flagella are made up of flagellum, which is a protein, the hook shown here, and the basal body in terms of its location, flagella can be found outside the cell which in which case it's an EXO flagella.

In its main part, or the main part may be inside the cell and of flagella as in the case of sprockets in the PERI plasmic membrane, which gives the spiral key bits curved shape The function of the flagella is locomotion. It allows the bacteria to rotate 360 degrees. The movement is mainly by runs that are punctuated by tumbles. The runs occur when the rotation is counterclockwise whereas the tumbles happen when the rotation is clockwise. based on the type of flagella, bacteria can be classified as very trickiest those that have the flagella uniformly distributed all around the body. monitory cares only on one side on one location.

Lawford requires several Polar meaning several on one side or the same pole and alpha Creek Yes, meaning a single flagellum located on each side of the pole. Therefore, this is infratry kiss and polar in terms of its structure at the level of the shaft prokaryotic flagella has nine triplets of microtubules and no microtubules in the center, as shown in this electron microscopic picture at the bottom and in the representation on the top three microtubules triplets, nine sets with none in the middle Shown here are Gram negative bacteria and the grandpa's two bacteria. I will explain the difference between these two types of bacteria in the next few slides. For now, the main difference between the gram negative and gram positive flagella is that the gram negative flagella is more complex in that the basal body is more complex and is located across the inner membrane and the outer membrane of the gram negative bacteria, whereas the basal body of the gram positive bacteria is much simpler located On the cell membrane.

Bacterial cell walls are composed of peptidoglycan, also known as murine moraine consists of an asset tailed Glucosamine, also known as energy and and I said del meramec acid also known as na m in terms of function, some wall helps in giving structure and shape to the bacteria or the prokaryote. It also helps protect from asthmatic forces and AIDS in attachment. The cell wall also helps in resistance against anti microbial agents. Now, let us look at the gram positive and Gram negative cell walls these bacterias named as such grandpa's do Gram negative according to a differential staining technique known as gram staining about which we will study at a later time. When comparing and contrasting the two, both gram positive and Gram negative are that cell walls are similar in that they both contain the cytoplasm and the both have the cell membrane. Now, while the gram positive bacteria has a thick peptidoglycan layer, the gram negative bacteria has a very thin peptidoglycan layer and the gram negative bacteria has an outer membrane of lipopolysaccharides while the gram positive bacteria does not.

Therefore, the gram negative bacteria is Double membrane whereas the gram positive bacteria is single membrane. Now, the archaea cell walls differ from bacterial cell walls in that they do not contain peptidoglycan, some archaeal cells may have what is known as the pseudo moraine, which literally means false smearing. DeSoto murine is made up of an acetyl glucosamine and then I said to last, so, me Nurik acid. Other archaeal cells may have polysaccharides proteins are both some archaeal cells consists contain the S layer which is a hexagonal pattern of protein and glycoprotein. The function of archaeal cell walls is mainly mechanical support and prevention of osmotic license. So in summary, prokaryotes have no nucleus because they lack a nuclear membrane.

They have no compartmentalization of function because they lack membranous organelles and they have a circular DNA. The two main domains are bacteria and archaea. The external structures we went over the capsule which is found mainly in pathogenic bacteria, the FIM Ria which allows for attachment and the Pillai which allows for conjugation of flagella, which helps with locomotion and the cell wall which is medical important you To the resistance against anti microbials This concludes part one