BIO 326R 1st Edition Lecture 3Outline of Last Lecture I. Phylogenetic Treea. Bacteriab. Archaeac. EukaryeaII. Bacteria traitsa. Sizei. Shapeii. Surface areaiii. Doubling timeb. Volumec. ProteinIII. Bacterial Cell Structurea. Cytoplasmi. Cytosol1. Ribosomes2. Nucleoid3. Ionsii. Viscosityb. Cell membranei. Phospholipid membrane1. Phospholipid structure2. Function of membranea. Permeability3. Sterol-lite moleculesa. Fluidityii. Protection1. Gram negative2. Gram positiveOutline of Current Lecture I. Gram positive and Gram Negative OverviewII. Gram positiveThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Peptidoglycani. NAG and NAMb. Techoic acidsIII. Gram Negativea. Peptidoglycani. Inner leaflet and outerleaflet1. LPSa. Lipd A, core, o-antigenCurrent LectureI. Gram Positive and Gram Negative Overview- Based on the ability of a bacterium to retain crystal violet (purple dye)/iodineo Experiment done by Hans Christian Gram (more details on Info Sheet on Bb)o Gram positives retain color and remain purple (e.g. Staphylococcus aureus) o Gram negative are decolorized and become red (e.g. Escherichia coli) - Osmotic pressure pushes against interior of cell membraneo Cell is still stable because the cell membranes of other cells (also with osmotic pressure pushing against interior) are against each other, thus stabilizing each other- Since bacteria stand alone so they need a cell wall, but some bacteria do not have a cell wall= Eubacteriao Mycoplasma= no cell wall, just plasma membrane, lives in humans, causes walking pneumoniao Eubacteria protect their cell membrane in other ways Gram positive Gram negativeII. Gram Positive- Produce a cell well that is composed of peptidoglycan= proteins/peptides and sugars (15-80 nm thick, normally ~60 nm)o Ex: Staphylococcus aureus or MRSA (methicillin resistant staph), Bacillus anthracis, Streptococcus pyogenes- Peptidoglycan is unique to bacteria good biomarkero 2 sugars composing peptidoglycan (which are bound to eachother) N-acetyl glucosamine (NAG)- Prevalent in other organisms bad biomarker N-acetylmuramic acid (NAM)- Specific to bacteria good biomarkero Peptides composing peptidoglycan Tetrapeptide= four peptides attached to NAM (and NAM is attached to NAG), containing D and L amino acids Covalent peptide bond between the third peptide of one peptidoglycan and the fourth peptide of another- Normally forming a chain of ~50 peptidoglycanso Lysosome cleaves the beta 1-4 linkage between NAG and NAMo Is peptidoglycan a good antibiotic target?-- YES It functions outside the cell, so antibiotics do not need to cross the membrane in order to target Humans don’t make it/have it so antibiotic won’t impact our other cells Our bodies have evolved to cleave with lysosomeo Penicillin (PCN)= antibiotic generally used to work against gram positive bacteria Blocks formation of (inhibits) PCN binding proteins (PBP)- PBP’s catalyze formation of tetrapeptide bondso Peptidoglycan diversity Different bacteria use different amino acids- This provides good way to identify different bacteria Bridges (peptides) link the tetrapeptides- Not always a direct linkage between the 3 and 4 peptide, sometimes a peptide between to link the two (like in staph)o Peptidoglycan is porous 2 nm wide pores—think of a chain-linked fence Lets through proteins (~25 kDa, or ~250 amino acids)- Teichoic acids and lipoteichoic acidso Teichoic= chains of sugars covalently linked to peptidoglycano Lipoteichoic= membrane associatedo Teichoic and lipoteichoic acids make the bacteria very hydrophilic Sugars are charged and keep out hydrophobesIII. Gram Negative- Examples: E. Coli, P. aeruginosa, Yersina pestis (plague)- Peptidoglycano Very thin layer (2-6 nm thick)o Peptidoglycan chain is 1-2 units thick- Outer membraneo Outer leaflet-- composition like plasma membraneo Outer leaflet-- composed of lipopolysaccharide (LPS) See picture on Bb slides Lipid A unit of LPS- Two sugars and two acyl chainso Two sugars are glucosamine derivatives- Very versatile, can change the structureo When in conformation of four fatty acid groups, two fatty acid groups, and two phosphates—toxic shocko This conformation is extremely rare and exists in a different conformation in humans Core unit of LPS- About 10 sugars—anionic O-antigen unit of LPS- Sugars, variable, hydrophilic, longer than the
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