2008 Microbiology Lecture 1

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3 Major groups of prokaryotes

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Gram Positive- thick layer of peptidoglycan gram stain purple
Gram Negative- thin layer of peptidoglycan covered by outer membrane gram stain red
Acid Fast- Long fatty acids in their cell wall gives them waxy coat

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Murein

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AKA peptidoglycan. it is a complex polymer of sugars and amino acids that allows both gram positive and negative to maintain their shape. with out PG if cell was put into hypotonic solution, it would burst. PG is hydrophilic

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Lysozyme

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hydrolytic enzyme in animals found in tears that hydrolyzes peptidoglycan

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describe PG in gram positive bact

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it is thick enough that hydrophobic molecules can not pass through it, because PG is hydrophilic in gram positive, the PG contains teichoic acid links PG to itself

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Teichoic acid

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Polymers that are chains of ribitol and glycerol linked by phosphodiester bonds. Links PG to itself, via MurNac

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polymers chains of.......

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Lipoteichoic acid

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Teichoic acid, but links PG to the cell membrane, hence being called lipo

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Gram negative bacteria

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Has outer membrane, and inner cell membrane with thin layer of PG in between. contains LPS lipopolysacharide the endotoxin

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describe outer membrane of gram negative include its function

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it is there to exclude hydrophilic compounds. Porins create the channels to allow passage of small hydrophilic molecules by diffusion. larger molecules have specific carriers

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Periplasmic space

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Created by the dual membran system of gram negative. it is exterior to cytoplasmic membrane and contains a gel like solution that facilatates nutrition. contains degrative enzymes helps soak up nutrition.

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Beta Lactamase

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an enzyme that break down pennicilin and promotes resistance

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components of gram negative outer membrane

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outer membrane is made of lipopolysaccharide. 3 components of lipopolysaccharide. Lipid A (anchors LPS to outer membrane), Core-polysaccharide. O-side chain

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Lipid A

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anchors LPS to outer membrane of gram negatives it is a glycolipid made of disaccharides attached to short chain fatty acids and phosphate groups

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Core Polysaccharide, and the characteristic sugars

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short series of sugars same for most gram negative bacteria on the outer membrane. 2 characteristic sugars. Ketodeoxytonic acid and heptose

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O antigen

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long carbohydrate chain protrudes from the outer membrane. helps exclude hydrophobic compounds. highly immunogenic and is variable from strain to strain so can be used to ID

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Endotoxin

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another term for Lipopolysaccharide because it triggers innate immune response and can lead to septic shock. lipid A is the toxic component

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describe response to LPS

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Lipid A is the toxic component. it triggers innate immunity.
Lipid A trigers macrophages and other cells to release inflamatory cytokines(TNF alpha) with in 1-2 hrs. Then IL-1 is secreted to initiate inflammmatory response that can lead to septic shock.

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Acid fast

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has waxy coat interlaced with murein, polysaccharides, and lipids. named beacause HCl fails to remove the dye. the fatty cell wall makes acid fast organisms resistant to killing by white blood cells. but these organism grow slowly becuase nutrients penetrate slowly

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myocolic acids

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in acid fast coat, fatty acids approx 60 C in length with 22-24 C side chains makes them a barrier to most compounds

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arabanogalactan

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serves as anchors for mycolic acids to PG

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role of bacterial cytoplasmic membrane, and its components

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it assumes the roles of the eukaryotic organelles. membrane involved in mitosis, membrane contains permeases that facilitate entry of most metabolites. contains cytochromes which are the sites of oxidative metabolism serves role of mitochondria

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bacterial ribosomes

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made of 50S and 30S subunits for a 70S as opposed to eukaryotic 60 and 40 for a 80S. this difference is due to the ribosomal RNA and its associated proteins

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Protein synthesis inhibitor drugs

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Aminoglycosides
Tetracyclines
Macrolides
Clindamycin

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K antigen

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the capsule. can be used to distinguis serogroups, and serotypes of an organism. it is usually antigenic. host response is serotype specific

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Glycocalyx

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polysaccharide that is secreted and accumulates. Different from capsule becuase its is not as tight as capsule. glycocalyx promotes adhearance to weird substances and prevents host inflamatory cells and mediators. leads to formation of plaque

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flagella

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used for motility can be polar, or peritrichous(all over). Flagella is H antigen and can be used to taxonomically distinguish bacteria

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Pili

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smaller than flagella and not used for locomotion. sex pili permits exchange of DNA, common ones are used for for adhesion. can also be antiphagocytytic
under differnt conditions bact can exhibit different pili

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Fibronectin

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a protein in oral mucosa that binds gram positive bacteria. under stress, fibronectin can be depleted and then common pili of gram negative can then attach

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Spores

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made by gram positive clostridium and bacillis. Thermally stable due to little water and calcium dipicolinate. it is dormant, until conditions allow it to reproduce