Microbiology: Chapter 3 - Prokaryotes
Microbiology: Chapter 3 - Prokaryotes Bio 221
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This 5 page Class Notes was uploaded by Savannah Carter on Wednesday September 7, 2016. The Class Notes belongs to Bio 221 at College of Western Idaho taught by Teresa Rich in Fall 2016. Since its upload, it has received 7 views. For similar materials see Microbiology in Biology at College of Western Idaho.
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Date Created: 09/07/16
Microbiology: Chapter 3 – Bacteria and Archaea Prokaryotes Form and Function o Distinguishing Characteristics The way DNA is packaged No nucleus No histones Make-up of the Cell Wall Bacteria have peptidoglycan Archaea have Internal Structures No membrane-bound organelles o Cell Structure All prokaryotes Cytoplasm Ribosomes Plasma membrane Nucleoid containing DNA Some prokaryotes (but not all) Flagella Fimbriae Inclusion Pilus Capsule Cell wall Plasmid o Shapes Cocci round balls Bacilli rods Vibrio comma shape Spirilium rigid corkscrew with flagella Spirochete flexible corkscrew o Arrangements Cocci each one is separate Diplococci pair of two Streptococci string Tetrad square of four Sarcinae cube of eight Staphylococci grape-like group Bacilli each one is separate Diplobaccili pair of two Streptobacilli string Coccobacillus short, fat rods (looks like a cocci) External Structures o Appendages: Cell Extension Accessory structures Not all species have them Extend outside of the cell Two main functions Motility Attachment o Glycocaylx “sugar cup” Composed of carbohydrates Two functions Preventing the cell from being phagocytized Helps the cell stick to things Two forms Capsule protection Slime layer attachment o Forms biofilms o Flagella Allow for motility Embedded in the cell wall Monotrichus – just one Lophotricus – many out of one end Amphitricus - many out of both ends Peritricus - all over the cell Endoflagella Wrapped around the cell Seen only in spirochetes When it spins, it spins the entire cell Chemotaxis “chemical movement” Positive: the bacteria is moving toward something it wants Negative: the bacteria is moving away from something bad Run: movement in one straight line direction Tumble: random spinning and rolling, trying to change directions o Fimbriae: Used to attach to other cells and surfaces o Pili: Grab other bacteria to exchange genetic material Cell Envelope o Complex external covering of the cell o Composed of cell membrane, cell wall, and outer membrane o Gram Stain Different groups of bacteria stain different colors Steps 1. Apply Crystal Violet (purple) stains both + and – 2. Apply Iodine trapped in + 3. Apply Alcohol breaks outer membrane of – (purple leaves - ) 4. Apply Safranin stains – o The Cell Wall Composed of carbohydrates and peptidoglycan (amino acids) Gram Positive Lipotochoric acid Thick peptidoglycan wall Contains mycholic acid o A wax that doesn’t stain easily o Pathogenic to humans o Must use acid-fast stain Gram Negative Thin peptidoglycan wall between cell membrane and outer membrane Outer Membrane o Similar to cellular membrane o Contains Lipopolysaccharides (LPS) Endotoxin (inside the cell) Stimulates fever and shock o Only allows very small molecules through Naturally resistant to some antibiotics o Cell Membrane Phospholipid Bilayer Hydrophilic heads on the outside Hydrophobic tails inside Function Provides a place for some processes to take place Regulates what goes in and out of the cell Internal Structures o Contents of Cytoplasm Cytoplasm Jelly, mainly water Chromosomes and Plasmids Contain DNA Found in nucleoids Plasmids contain “superhero genes” o Resistance to antibiotics, toxins o Make the cell stronger Ribosomes Make proteins using DNA Composed of protein and RNA Sizes o Large subunit = 50 S o Small subunit = 30 S o Ribosome = 70 S o A eukaryotic ribosome = 80 S Inclusions and Granules Stores of extra food, gas, or waste Cytoskeleton Some bacteria have them Actin filaments and microtubules o Bacterial Endospores Function Help bacteria survive heat, radiation, drying, and lack of food One of the most resistant forms of life Are not reproductive Formation Vegetative Stage: growing, eating, reproducing o One vegetative cell forms one endospore Endospore Stage: resting and surviving o One endospore forms one vegetative cell Germination Caused by water, the presence of food, boiling One endospore forms one vegetative spore After endospore formation is complete, the vegetative cell’s DNA is degraded The endospore is wrapped in protective layers Archaea o Closely related to eukaryotes o Single, circular chromosomes o 70 S ribosomes o Cell membrane is a lipid monolayer One long chain with a hydrophobic tail on the end o Do not contain peptidoglycan o Found in the same places as bacteria Classification Systems o Bergey’s Manual Systematic Bacteriology Combines phenotype with ribosomal RNA sequencing Determinative Bacteriology Based only on phenotype o Taxonomic Schemes Gracilicutes “delicate or thin” Gram negative Firmicutes “firm or thick” Gram positive Tenericutes Do not have a cell wall Mendosicutes Archaea Unusual cell walls o Species and Subspecies Species: a collection of cells that share an overall pattern of traits Share 70-80% of their genes
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