Transcript Prokaryotes
Prokaryotes Prokaryotes • The domain of Bacteria – The typical bacterium contains: cytoplasm, nuclear material, ribosomes, a cell wall, plasma membrane, pili, flagellum, and capsule. Prokaryotes • lack a cell nucleus, or any other membrane-bound organelles Prokaryotes One way to classify bacteria is by examining its shape. We will examine the three basic shapes but note that others exist. Prokaryotes • Three basic shapes of bacteria • Bacilli • Cocci are rod-shaped with noticeable breaks spherically-shaped • Spirilla spiral-shaped with smooth curves Prokaryotes • Bacterial Colony Morphology study of the form and structure • Borrelia burgdorferi • Spiral/Spirilla • Lyme disease Prokaryotes • Form - What is the basic shape of the colony? • For example, circular, filamentous, etc. • Escherichia coli – Bacillus/Rod Prokaryotes • Elevation - What is the cross sectional shape of the colony? • Staphylococcus aureus – Coccus- round Prokaryotes • In 1884 Hans Christian Gram developed a staining procedure, Gram Staining • The composition of the cell wall of bacteria vary among species. Prokaryotes Prokaryotes • Due to this difference bacteria can be divided into two groups; • Gram positive • Gram negative Prokaryotes • Gram positive – bacteria have thick peptidoglycan cell walls and retain a purple color when stained with crystal violet. – Usually less toxic Prokaryotes • Gram negative • bacteria have thin peptidoglycan cell walls these cells retain the red color when stained Prokaryotes • Gram staining involves three processes: 1.Staining with a water-soluble dye called crystal violet, 2.Decolorization, 3.Counterstaining, usually with safanin. Results • Red rods gram negative • Purple circles gram positive • Review……. Prokaryotes • Reagent: is a substance or compound consumed during a chemical reaction. • • • • • Crystal violet (primary stain) Iodine solution/Gram's Iodine ( fixes crystal violet to cell wall) Decolorizer (e.g. ethanol) Safranin (secondary stain) Water (preferably in a squirt bottle) Prokaryotes • Decolorizer (e.g. ethanol) which dehydrates the peptidoglycan layer, shrinking and tightening it.