Micro Chapter 6 – Flashcards
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A chemoheterotroph obtains its energy from __________ and its carbon from __________ sources
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redox reactions; organic
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Which of the following represent the majority of pathogenic bacteria?
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mesophiles
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The most commonly used isolation technique in microbiology laboratories is the __________.
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streak-plate method
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Blood agar is an example of which of the following?
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a differential medium and a complex medium
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A colony-forming unit is a __________.
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single cell or group of related cells that gives rise to a colony
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Microbes in the __________ phase of the microbial growth curve are most susceptible to antimicrobial drugs
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stationary
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What results when a single bacterium reproduces?
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Two genetically identical daughter cells
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If you begin with six cells, how many cells would you have after three rounds of division?
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48
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Which of the following is NOT a step in bacterial cell division?
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Disappearance of nuclear envelope
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Which step of binary fission is the reason for genetically identical daughter cells?
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Replication of the bacterial chromosome
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You open a jar that has been in the refrigerator for a couple of weeks and find the contents do not look or smell right. What type of microbe has been growing in your refrigerator?
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psychrophile
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Which of the following is NOT a step in bacterial cell division?
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Disappearance of nuclear envelope
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colony
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literally a colony of cells arising from a parent cell
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biofilm
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collection of microbes living on a surface in a complex community
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microbial growth
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increase in microbial population by reproduction producing colonies or biofilm
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growth requirements
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carbon, oxygen, nitrogen, hydrogen
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Organisms may be organized depending upon their source of nutrients/energy/electrons
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true
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Autotrophs
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obtain nutrients from CO2
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heterotrophs
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obtain nutrients from organic molecules
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chemotrophs
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obtain energy from chemicals
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Phototrophs
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obtain energy from sunlight/ photosynthesis
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organotrophs
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heterotrophs acquire electrons from organic molecules
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lithotrophs
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autotrophs get electrons from inorganic chemicals
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obligate aerobes
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oxygen is ESSENTIAL for growth
grow @ top
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singlet oxygen
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(O2) molecular oxygen with electrons in higher energy state
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superoxide radicals
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(O2-) form from the incomplete reduction of O2
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peroxide anion
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(O_2^2-) formed during reactions catalyzed by superoxide dismutase
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hydroxyl radical
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(OH) result from ionizing radiation and incomplete reduction of hydrogen peroxide
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obligate anaerobes
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grow best w/o oxygen
grow @ bottom
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facultative anaerobes
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grow better with oxygen but will also grow w/o
grow from top sprinkled to bottom
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aerotolerant anaerobes
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grows the same with or without oxygen
grow same throughout media
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microaerophiles
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grow with small amounts of oxygen
grow in the middle
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cell growth: temperature
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temp. effects the structure and the structure effects the proteins and if the proteins are messed up the function changes and if the functions change the cell will most likely die.
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psychrophiles
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grow best below 15C & die above 20C
snowfields ice and cold water
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mesophiles
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15C-45C
human pathogens
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thermophiles
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45C- 80C
compost and hot springs
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hyperthermophiles
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65C- 105C
in water above 80C
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Heat loving organisms (thermo and hyperthermophiles)
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don't cause disease bc they "freeze" at body temperature (37C)
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Neutrophiles
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grow at neutral pH (7)
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Acidophiles
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grow in acidic enviroments (1-6.5)
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Alkalinophiles
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grow in alkaline soils and water (7.5-14)
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Hydrostatic pressure
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water exerts pressure in proportion to its depth
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barophiles
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thousands of meters below the surface (in the ocean)
depend on pressure to maintain their shape
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Water and microbial growth
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needed to dissolve enzymes and nutrients
metabolic rxn's
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osmotic pressure
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hypotonic solutions have lower solute concentrations
cells in hypotonic solutions swell
cells in hypertonic solutions shrivel
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antagonist relationship
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microbe harms another organism
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synergist relationship
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organisms living together are better off together than they would be apart
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symbiotic relationship
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organisms become interdependent and don't live outside the relationship
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plaque is a biofilm that leaves cavities
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true
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defined media
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defined by the EXACT chemical composition good for fastidious organisms that need a lot of extra nutrients to grow
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complex media
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chemical comp unknown grows wide variety of microbes
(nutrient agar)
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enrichment media
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enriches particular microbes to observable levels
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anaerobic media
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generally used for obligate anaerobes
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transport media
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used to transport clinical samples without spreading infection
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animal and cell culture
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used to grow viruses and intracellular parasites for observation
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preserving cultures
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refrigeration, deep freeze, lyophilization (freeze dried)
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why do clinical lab scientists keep many different kinds of culture media on hand?
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there's no universal medium and you never know what microbes you'll be working with
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generation time
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time required for bacterial cell to grow and divide
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Log Phase
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cells grow logarithmically bc they have to adjust to the media (active growth)
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chemostat
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maintains microbe population at a particular growth stage (log, stationary, death)
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Open System
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continuous addition and removal of media
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membrane filtration
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when you have more liquid than microbes
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measuring microbial growth
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metabolic activity
weight
turbidity/ absorbance
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Students transfer some gunk from a two week old bacterial culture into new media. Why shouldn't they be surprised when this death stage sample grows?
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bc they put it in new media with new nutrients
