Welcome to Biology 134/135 Microbiology
Question: (past exam) You discover that a bacterium infecting a patient contains lipopolysaccharides (G-). From this you could conclude that the bacterium A) does not use ATP as an energy carrier. B) has a cell wall with a thick layer of peptidoglycan. C) has both an inner and outer membrane. D) can form endospores. E) is a eukaryote.
Announcements • The internet report is due online on February 10 th . Assignment details are on Canvas. • The first in-class clicker quiz is next Wednesday, February 8 th . It will cover all material from the start of class through Monday, February 6 th .
bacterium Prokaryotic Cells: plasma membrane phospholipid bilayer
Phospholipid bilayer hydrophobic tails hydrophilic head hydrophilic head Hydrophobic molecules will push out hydrophilic molecules, and vice-versa: - Think about mixing oil (hydrophobic) and water (hydrophilic) hydrophilic = water "loving" hydrophobic = water "fearing" water
cell wall bacterium Prokaryotic Cells: plasma membrane
teichoic acid Gram positive cell wall bacterium thick peptidoglycan cell wall plasma membrane peptidoglycan
Gram positive cell wall • A single thick layer of crosslinked peptidoglycan and teichoic acid molecules • Thick, rigid structure • Porous , will allow many types of small molecules to pass through Peptidoglycan Cell membrane Gram (+) Cell membrane Cell wall (peptidoglycan) © S.C Holt/Biological Photo Service
Gram negative cell wall bacterium peptidoglycan cell wall (single layer) plasma membrane outer membrane periplasm porin lipopolysaccharide (LPS)
Gram negative cell wall LPS structure O antigen O polysaccharide Lipid A endotoxin E. coli O157
Gram negative cell wall Cell membrane Peptidoglycan Outer membrane Cell membrane Cell wall Periplasmic space Peptidoglycan Gram (–) Outer membrane © T. J. Beveridge/Biological Photo Service • A single thin layer of peptidoglycan • Surrounded by an outer membrane of phospholipids and lipopolysaccharides . • Thin, flexible structure. • Less penetrable by small molecules thanks to alternating hydrophobic and hydrophilic barriers.
Gram positive vs. Gram negative • Thick , heavily crosslinked peptidoglycan cell wall • Teichoic acid • Thin peptidoglycan cell wall • Outer membrane • Lipopolysaccharides (LPS)
Gram positive vs. Gram negative Peptidoglycan Teichoic acid Phospholipid Membrane proteins Lipopolysaccharide Porin Lipoprotein Membrane proteins Periplasmic space Lipoproteins Cell membrane Periplasmic space Peptidoglycan Outer membrane layer Lipoteichoic acid Wall Teichoic acid Envelope Lipopolysaccharides Porin proteins Phospholipids Membrane protein
Why does the stain work?
Why does the stain work?
- Spring '14
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