 Welcome back to meds smarter where we take a smarter approach to preparing future physicians Before we begin go ahead and hit that subscribe button. It helps us out a lot. Let's get started talking about the bacterial structures So we're going to compare and contrast gram positive and gram negative bacteria on the surface gram positive Have a very very large peptidoglycan layer Which this is like a net like structure if you saw this in a 3d model it would Almost have some cross linkings. That's like a net, okay? Gram positives have this peptidoglycan layer. That's very thick and Comparing that to a gram negative gram negatives do have a peptidoglycan layer as you can see in the middle of This figure. However, it also has an outer membrane on top of that peptidoglycan layer Which makes it more difficult to stain with certain stains and we'll talk about that in just a little while So let's look at the structure function and composition of each individual part of a bacterial cell so the cell wall of bacteria Gives it that rigid support and it helps protect it against water and osmotic pressure pressure damage as it goes throughout its environment It's made up of a peptidoglycan sugar backbone with a Sidechain peptide that cross links that which gives us that net like structure as I talked about earlier the periplasm also known as the periplasmic space is where we have accumulation of Components of cells that will exit the gram negative Cells such as hydrolytic enzymes and like beta-lactamases this area is not made up of anything It's just space it is a space between the outer membrane and the peptidoglycan layer as you can see in the blue On the bottom of the gram negative and it's also between the peptidoglycan layer and the plasma membrane below that the cytoplasmic membrane is a Location where we see oxidative and transport enzymes like lipotycoic acid only in gram positives and these oxidative and transport Enzymes extend from the membrane to the exterior only this is actually a phospholipid bilayer that has those embedded proteins in it Some more structures to talk about spores. What is a spore spores are found only in gram positive organisms? That's very important to remember What does the spore do well the spore basically is a keratin like coat a dipolyclonic acid As well as a peptidoglycan and DNA and it basically comes in and protects that Gram positive bacteria from dehydration heat and chemicals Some more bacterial structures to discuss on gram negative Bacteria they have an outer membrane like we said earlier. That's what distinguishes gram negative and gram positive is that outer membrane So what does the outer membrane do in a gram negative bacteria? Well, this is where we see the endotoxin Location and then it's also where we can see major surface antigens present themselves It's made up of an inner and outer leaflet. It's a bilipid layer. So the outside Leaflet has endotoxins and the lipopolysaccharide layer and the inner leaflet is phospholipids Bacteria also have capsules on them and these are present in both the gram negative and the gram positive bacteria And what they do is they protect that capsule from phagocytosis It's made up of polysaccharides as well as some rare proteins some bacteria also have a flagellum Which is therefore motility to help the bacteria move to move around and find new places and to become more infectious It's composed of proteins in that flagellum Other bacteria don't have a flagellum they may have a pilus or a fimbria and The function of the pilus of the fimbria is for it to be able to adhere to the cell surface And then the sex pilus is used during conjugation So that the bacteria can undergo reproduction and this is all made up of glycoproteins