I've run dr. Mikey let's talk about the differences between gram-negative and gram-positive bacteria so as you can see I've drawn up a gram positive bacteria here a gram negative here if we start on the inside and move out we can talk about the similarities and differences so starting right in the middle right in the center of the bacteria you can see that both grandpas and gram-negative have a cell membrane just like we have a cell membrane surrounding ourselves bacteria have a cell membrane and it's the same as ours called a phospholipid bilayer now what are the differences between our phospholipid bilayer and bacterial phospholipid bilayers is that ours contains sterols which are basically cholesterol embedded in the membrane that allows it to have this fluid mosaic structure to it bacteria don't have cholesterol embedded in their membranes so it alters the rigidity of the bacteria okay next thing is that as we move out you can see with the gram positive bacteria it's got a thick cell wall now we don't have a cell wall bacteria do have a cell wall which means we can exploit these differences to kill off bacteria and when they're invading us and we do this through antibiotics so for example penicillins and cephalosporins they actually attack this cell wall busted apart what that means is if you look at a bacteria compare what's happening inside the cell to outside the cell there's so many more components and substances inside the cell that it wants to drag water towards it that's called the osmotic effect now because of the cell wall water doesn't get pulled in and it doesn't burst so the cell wall basically is there to maintain the rigidity and structure of the bacteria so it doesn't burst when water comes in but when you attack bacteria with penicillins and cephalosporins and it pulls apart this cell wall it means that when water does rush in through this osmotic effect the cell will burst and will die off so that's basically how penicillin cephalosporins work now if we have a look at the structure what it's actually made from it's made out of sugars and proteins so you can see the blue lines I've drawn here the sugars which are called glycans and in the protein they're called peptides and they've clicked them all together now there's another substance that we produce in our tears our saliva and our mucus called lysozymes and what Liza's arms do is actually stop these glycans or the sugars from holding themselves together so this is one defense that we have against bacteria more specifically gram-positive bacteria now gram positive bacteria don't have anything else really surrounding them on the outside it's basically a phospholipid bilayer on the inside and then a very thick cell wall when we look at gram-negative has the phospholipid bilayer and a very thin cell wall but then what it has is another phospholipid bilayer okay now between the cell wall the thin cell wall and the phospholipid bilayer there's another layer called Lippo protein so that's fats and proteins click together and then the phospholipid bilayer on the outside has imbedded in it these things called Lippo polysaccharides okay LPS and you can see I've drawn a red component to it and a blue component to each of them look like tiny little pineapples here okay the red component of lipid polysaccharides are lipids known as lipid a and the blue part are polysaccharides which just means many sugars click together now why have i drawn up these differences because the lipid component lipid a of LPS is actually in endotoxin and what that means is when bacteria replicate or gram-negative bacteria replicate they can release this endotoxin or when you kill off gram-negative bacteria with antibiotics the endotoxins released and that can result in endo toxic shock what that means is it tells our immune system to basically ramp up open up our blood vessels let fluid leak out of our blood vessels and our body goes into shock now it doesn't matter what type of gram-negative bacteria this lipid component is identical which means endo toxic shock is the same for everybody regardless of what gram-negative bacteria is causing it now the polysaccharides on the outside they aren't pathogenic which means they don't cause disease but they are immuno genic which means our body does reckon these polysaccharides and allows for us to have this immune response that's targeted to the gram-negative bacteria so the lipid component is not immuno genic we don't recognize it and can't have a targeted response but it is pathogenic causing disease and the polysaccharides do the opposite they are immuno genic but they're not pathogenic you can also see that gram-negative bacteria have pause which allows some substances to move through the outer cell membrane to be able to get through now this is the thing gram-negative bacteria are far more difficult to get into the ground positive because they've got two phospholipid bilayers and a phospholipid bilayer does not let anything through that's large or charged okay so these pores are there to sort of let some of these things throw but for example our very first class of penicillin called penicillin G was fat it couldn't fit through these pores and it couldn't kill off gram-negative bacteria it could easily do gram positive bacteria because it could attack that cell wall so these are the major differences between gram positive and gram negative bacteria it's called gram positive ground negative named after a Danish physician Christian gram who would stain up the cell wall of the ground positive and a wouldn't stain up the gram negative and therefore could differentiate between the two