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antibiotic discovery

mold contaminated plates of bacteria. the clear areas present was penicillin

shape and arrangement ( monomorphic pleomorphic )decided by

heredity

glycocalyx

coat/layer surrounding the bacterial cell ( capsule slime layer)

what is glycocalyx made up of

polysaccharide, polypeptide, or both

virulence

degree to which a pathogen causes disease

virulence factor

component of organism that determines its capacity to cause disease

flagella

long appendages for motility

flagella function

taxis: movement of bacteria in response to stimuli (attractant or repellent

chemotaxis:

chemical stimuli

phototaxis

light stimuli

receptors on surfacer sense

chemicals and or light leading to flageller motility

axial filaments

internal filaments

• spiral shaped bacteria onlu (spirochaets)

• aloows spirochaetes to move through host tissue like a drill

carl woese 1978

sequenced the 16 portion of the ribosomal RNA to show evoultionary relatedness

ribosome

site of protein synthesis and is composed of RNA and protein

ribosomes pros

• all organisms have ribosomes, low mutation rate, high number of organisms not required to get a sequence

gram postive cells

envelope composed of inner membrane surrounded by a thick layer of cell wall

gram postive lipid composition

30% phosphatidylethanolamine and 70% phosphatidylglycerol

gram posoitive cell wall composition

peptidoglycan and teichoic acids

wall teichoic acid

anchored to the peptidoglycan layer

Membrane teichoic acid (lipoteichoic acids)

anchored to the outer leaflet of the inner membrane

what are Teichoic acids and lipoteichoic acids

Glycopolymers

Glycopolymers ( Teichoic acids and lipoteichoic acids) functions

binding mg2+ and ca2+ cations in the cell wall which promotes membrane stability and source of metals

• influences cell permeability

gram negative inner membrane composition

75% phosphatidylethanolamine, 20% phosphatidylglycerol, and 5% cardiolipin*.

what is in between the inner and outer membrane in hram negative bacteria

Periplasmic space is densely packed with proteins and contains the cell wall peptidglycan)

outer membrane is

stucturally asymmetrical

gram negative inner side

contains phospholipids

gram negative outer side

lipopolysaccharide and phospholipids and 60% of surface is protein

what makes up a major portion of the proteins in the outer membrane

porens

Lipopolysaccharide 3 segments o- side chain

serves as a major antigen

middle part of Lipopolysaccharide

Core oligosaccharide (varies)

Lipopolysaccharide segments: lipid A

tethers lipopolysaccharide into the hydrophobic region of the outer membrane

cross bridges provide

structural stability

gram negative cross bridge

only 5% of possible cross-links are used

gram positive cross bridge

more than 60% of possible bonds formed

penicillin has poor activity against

gram negative

penicillin has good activity

against gram +

penicillin mechanism of action

prevents crosslinking of strands of cell wall (loses stability) causing weak points to be created in cell envelope

penicilling is destroyed by most

acids

how does penicillin mechanism cause weak points

penicillin prevents peptide linkages by binding to penicillin binding proteins