Microbio Ch 4 – Flashcards

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Basic Shapes
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Spehrical / Cubical / Cylindrical
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Internal Content
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cytoplasm (surrounded by a membrane) , DNA chromosomes, ribosomes, metabolic capabilities
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two basic cell types
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eukaryotic and prokaryotic
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eukaryotic cells are found in
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animal cells, plant cells, fungal cells, and protista cells
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prokaryotic cells are in
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bacteria and archaea do not contain a nucleus or other membrane-bound organelles
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two major groups of appendages
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motility - flagella and aial filaments / attachment or channels - fimbriae and pili
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glycocalyx
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surface coating
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flagella has 3 parts
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Filament – long, thin, helical structure composed of protein flagellin; Hook – curved sheath ; Basal body – stack of rings firmly anchored in cell wall
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chemotaxis
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chemical stimuli ; moves towards or away from chemical stimulant
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phototaxis
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light stimuli ; moves towards or away from light stimulant
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flagella counterclockwise movement
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results in smooth linear directioin "run"
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flagella clockwise movement
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tumble
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fimbriae
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fine, proteinaceous, hair - like bristes emerging from the cell surface
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fimbriae functions
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adhesion to other cells and surfaces
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pili
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rigid tubular structure made of pillin protein ; found only in gram negative cells
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pili functions
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joins bacterial cells for partial DNA transfer (conjugation)
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two types of coatings
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slime layer - loosely organize and attached ; capsule -highly organized, tightly attached
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glycocalyx function
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protects cells from dehydration and nutrient loss ; inhibit killling by white blood cells by phagocytosis ; contributes to pathogenicity ; formation of biofilms
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cell wall
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External covering outside the cytoplasm; Maintains cell integrity
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cell wall functions
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Determines cell shape, prevents lysis due to changing osmotic pressures
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gram positive bacteria
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thick cell wall composed primarily of peptidoglycan and cell membrane
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gram negative bacteria
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: outer cell membrane, thin peptidoglycan layer, and cell membrane
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peptidoglycan
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primary component of cell wall; unique macromolecule ; a repeating framework of long glycan chains cross-linked by short peptide fragments
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gram positive cell walls
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Attach layers of peptidoglycan to each other and to cell membrane ; function in cell wall maintenance and enlargement during cell division; move cations across the cell envelope; stimulate a specific immune response
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gram negative cell walls
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Made up of three distinct levels: ; The outer membranes – LPS ; Lipid portion (endotoxin) may become toxic when released during infections ; May function as receptors and blocking immune response ; Contain porin proteins in upper layer – regulate molecules entering and leaving cell
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periplasmic space
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between the LPS and the cell membrane; a thin layer of peptidoglycan in the periplasmic space
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gram positive stain
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- retain crystal violet and stain purple
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gram negative stain
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lose crystal violet and stain red from safranin counterstain
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non-typical cell walls
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Some bacterial groups have extra ingredients in their cell wall: Mycobacterium and Nocardia ; G +ve cell wall structure with lipid mycolic acid (cord factor) ; Pathogenicity and high degree of resistance to certain chemicals and dyes; Basis for acid-fast stain used for diagnosis of infections caused by these microorganisms ; Some have no cell wall, i.e., Mycoplasma ;Cell wall is stabilized by sterols; “Pleomorphic”
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cell membrane structure
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Phospholipid bilayer w/proteins – fluid mosaic model
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cell membrane structure functions
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Providing site for ETC, nutrient processing, and synthesis ; Passage of nutrients into the cell and discharge of wastes ; Cell membrane is selectively permeable
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cytoplasm
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Dense gelatinous solution of sugars, amino acids, and salts ; 70-80% water ; Serves as solvent for materials used in all cell functions
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chromosome
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Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell
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plasmids
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Free small circular, double-stranded DNA ; Not essential to bacterial growth and metabolism ; Used in genetic engineering - readily manipulated and transferred from cell to cell
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ribosomes
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made of 60% ribosomal RNA and 40 protein ; consists of two subunits ; prokaryotic differ from eukaryotice ribosomes in size and number of proteins ; site of protein synthesis ; found in all cells
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cytoskeleton
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Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall
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endospores
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Inert, resting, cells produced by some G+ genera: Clostridium, Bacillus, and Sporosarcina; Have a 2-phase life cycle: ; Vegetative cell – metabolically active and growing; Endospore – when exposed to adverse environmental conditions; capable of high resistance and very long-term survival
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sporulation
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formation of endospores ; Hardiest of all life forms; Withstands extremes in heat, drying, freezing, radiation, and chemicals ; Not a means of reproduction
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germination
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return to vegetative growth
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endospores
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Dehydrated, metabolically inactive ;Thick coat; Longevity verges on immortality, 250 million years; Resistant to ordinary cleaning methods and boiling ; Pressurized steam at 120oC for 20-30 minutes will destroy – autoclave!
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pleomorphism
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Variation in cell shape and size within a single species ;Some species are noted for their pleomorphism
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classification system for prokaryotes based on
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microscopic morphology / macroscopic morphology / baterial physiology / serological analysis / genetic and molecular analysis
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phylum proteobacteria
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gram negative cell walls
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phylum firmicutes
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mainly gram positive with low G + C content
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phylum actinobacteria
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gram positive with high G + C content
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species
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a collection of bacterial cells which share an overall similar pattern of traits in contrast to other bacteria whose pattern differs significantly
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strain or variety
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a culture derived from a single parent that differs in structure or metabolism from other cultures of that species (biovars, morphovars)
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type
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a subspecies that can show differences in antigenic makeup (serotype or serovar), susceptibility to bacterial viruses (phage type) and in pathogenicity (pathotype
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photosynthetic bacteria
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use photosynthesis, can synthesize required nutrients from inorganic compounds; Cyanobacteria (blue-green algae) ; Green and purple sulfur bacteria ; Gliding, fruiting bacteria
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cyanobacteria
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Gram-negative cell walls ;Extensive thylakoids with photosynthetic chlorophyll pigments and gas inclusions
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green and purple sulfur bacteria
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Photosynthetic ; Contain photosynthetic pigment bacteriochlorophyll ; Do not give off oxygen as a product of photosynthesis
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gliding and fruiting bacteria
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gram negative and glide over moist surfaces
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archaea ; the other prokaryote
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Constitute third Domain Archaea ; More closely related to Eukarya than to Bacteria ; Contain unique genetic sequences in their rRNA ; Have unique membrane lipids and cell walls
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archaea
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Live in the most extreme habitats in nature, extremophiles ; Adapted to heat, salt, acid pH, pressure, and atmosphere ; Includes: methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers
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