Chapter_28_lecture_RAVEN_NG2009 (1)

It is a differential stain since it divided bacteria

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Unformatted text preview: s a staining method. It is a differential stain since it divided bacteria into 2 categories (aqueous pores) periplasmic space more common -Gram-positive bacteria -Gram-negative bacteria -Thick peptidoglycan wall -Thin peptidoglycan -Teichoic and lipoteichoic acids -Have an outer membrane lipids w/ polysaccharid protruding from the cell wall c -Contains lipopolysaccharhains ide -resistant to antibiotics 11 - retain a purple color when gramstained - do not retain the purple-colored dye of gram stain External Layers In some bacteria and archaea, an additional S-layer may be formed S-layer -A rigid protein or glycopoutsideithe layer found in some and outer membrane o rote n peptidoglycan of gram-positive bacteria gram-negative bacteria bacteria and most archaea - In archaea, outside pseudopeptidoglycan layer OR only rigid layer around -Aids in attachment to surface or protection cell Capsule -A gelatinous layer found in some bacteria that surrounds other wall layers -Aids in attachment to surfaces or other cells -Protects from the immune system by interfering with recognition by phagocytic cells => contributes to bacterium's ability to cause disease 12 Bacterial Appendages Pili -Short, hairlike structures -Found in some Gram-negative bacteria -Aid in attachment and conjugation (exchange of genetic information) Flagella -Long, helical structures -Composed of the protein flagellin -Involved in locomotion by rotation - Anchored in the cell wall 13 exceptions: - Vibrio cholerae have 2 circular chromosomes - Borrelia have multiple linear chromosomes Internal Structure Simple interior organization lacking compartmentalization Single, circular, DNA Nucleoid regionc:ondensed to formdouble-stranded calledmolecule is a visible region the nucleoid. -Many prokaryotic cells may have small, independently -plasmids replicating cicles of DNA called plasmids. - Yet they depend on the cell for replication . Ribosomes -Contain only a few genes. Not essential for survival -Smaller than those of eukaryotes and differ in RNA/protein content -Antibiotics can bind to prokaryotic ribosomes and block synthesis Internal membranes: comprised of invaginated regions of plasma membrane (for photosynthesis or respiration) Endospores (structures formed by some bacteria) -Highly-resistant structures (environmental stress) -thick wall around genome -Can germinate back to normal cell -Highly resistant to environmental stress, especial...
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This document was uploaded on 02/14/2014.

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