Microbiology exam 2

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  1. How long does it take an E.coli cell to multiply
    it can divide every 20-30 minutes
  2. essential nutrients
    nutrients a microbe needs and cannot make itself so its environment supplies them
  3. 6 microorganisms needed macronutrients
  4. macronutrients are needed and in large amounts while micro nutrients are needed but in very small amounts
  5. 6 micronutrients all cells need
    Co, Cu, Mn, molybdenum, Ni, Zn
  6. why are the micronutrients needed
    the elements are essential components of enzymes and aid in the catalytic processes
  7. breaking down molecules for energy
  8. using E to rebuild cell components, reduces entropy
  9. central biochemical pathways used for the balance between catabolism and anabolism
  10. 3 examples of metabolism
    TCA cycle, Glycolysis, pentase phosphate shunt
  11. all life requires are these 3
    • electron flow to drive all life processes
    • energy to move molecules
    • materials to make cell parts
  12. drives ins into/out of cells and is used to create ATP
    electron flow
  13. materials to make cell parts example is nutrients
  14. predominant E source in microbial metabolism is
  15. How is the E source of microbial metabolism electricity
    electrons get passes from A to B via oxidation and reduction. the E of the electron flow powers the cell
  16. electron flow requires these 2
    • source of electrons
    • ultimate electron acceptor
  17. 2 sources of electrons for electron flow needs
    • lithotrophs
    • organotrophs
  18. inorganic molecules are electron donors for this source of electrons
  19. organic molecules are electron donors for this source of electrons
  20. inorganic molecules that act as ultimate electron acceptors are these 2
    • aerobic (oxygen)
    • anaerobic (nitrate)
  21. organic molecules that act as ultimate electron acceptors is
    fermentation (pyruvate to lactic acid, ethanol)
  22. ultimate electron acceptors are these 2 kinds of molecules
    • inorganic
    • organic
  23. 2 sources of E for microbial metabolism
    • light
    • chemicals
  24. excited molecules are electron donors in this source of energy obtaining microbes
  25. chemicals are electron donors in this source of E obtaining microbes
  26. carbon source for biomass
    major material
  27. CO2 assemble into organic molecules
  28. acquired organic molecules as carbon source
  29. a chemotroph that obtains its electrons and carbon from organic molecules (organotroph)
  30. a chemotroph that obtains its electrons from inorganic molecules and its carbon from CO2 (lithotroph)
  31. a phototroph that obtains electrons from water (oxygenic) and carbon from organic molecules
  32. a phototroph that obtains electrons from sulfuric acid (anoxygenic) and its carbon from CO2
  33. most organotrophs are also heterotrophs
    many microbial organisms can use a combo of metabolic pathways
  34. must be supplied from the environment
  35. 4 ions necessary for protein function
    Mg, Ca, Fe, K
  36. different microbes require different additional nutrients
    amino acids, N from air/soil, electron acceptors, energy source
  37. contains only the compounds needed for an organism to grow
    minimal medium
  38. N2 makes up 79% of earth's atmosphere but is unavailable for use by most organisms
  39. oxidize ammonia to nitrate
  40. convert nitrate to N2
  41. N2>nitrogen fixers>NH4>nitrifiers>NO3>denitrifiers>N2
  42. nitrogen fixing bacteria may b free living in soil or water, or they form symbiotic association with plants
  43. 3 functions of symport and antiport active transports
    • gradient of one molecule transports another
    • transports material against its concentration gradient
    • can us Na gradient to import amino acid
  44. electron transport creates PMF which transports other molecules
  45. ATP binding cassette (ABC transporters) are the superfamily of transporters
  46. ABC transport functions
    use ATP E to pass material in/out of cell against gradient
  47. 3 functions of siderophores (nutrient uptake)
    • molecules secreted t scavenge iron
    • imported via ABC transporters
    • can bind to other metals
  48. active transport of nutrient uptake
    phosphotransferase system PTS
  49. 3 characteristics to PTS
    • group translocation system
    • uses E to pass material into cell
    • modifies material as it enters the cell
  50. PTS explained: glucose enters cell and s phosphorylated. As a result, gradient of G pushes more G inside while the phosphorylated ones cannot leave
  51. has all materials necessary for growth
    culture media
  52. what are the 4 components of a culture media
    • electron source
    • energy source
    • carbon source
    • nitrogen source
  53. the culturing media varies for different bacterial species.
  54. A culturing media needs an energy source if its
    not phototrophic
  55. A culturing media needs a carbon source if its
    not autotrophic
  56. A culturing media needs a nitrogen source if its
    not N2 fixer
  57. 6 different types of culture media
    • liquid vs solid
    • minimal vs complex
    • enriched with blood
    • selective
    • differential
    • MacConkey medium
  58. 2 functions of MacConkey medium
    • selects against gram+
    • differentiates lac metabolism
  59. are nutrient rich and poorly defined
    complex media
  60. are precisely defined
    synthetic media
  61. are complex media to which specific blood components are added
    enriched media
  62. favor the growth of one organism over another
    selective media
  63. exploit differences between two species that grow equally well
    differential media
  64. all cells in a colony derive from a single cell
  65. the single cell makes a colony that contains cells that are genetically identical (clone of that original cell)
  66. 2 dilution streaking characters
    • streak cells on plate
    • agar inhibits spread of microbes on plate
  67. dilution in liquid culture does what when it comes to obtaining pure cultures
    reduces number of cells in each tube
  68. what does dilution in liquid culture determine
    colony forming units
  69. in dilution in liquid culture you spread liquid on plate to see single colonies
  70. disadvantage of petroff hausser chamber when looking at cells
    can't tell if cells are alive or dead (stain to distinguish living cells)
  71. counts cells directly using microscope and gives accurate numbers
    petroff hausser chamber
  72. in the petroff hausser chamber directly in the middle, there are 25 groups of 16 small squares
  73. measures optical density and gives rapid measurement
    spectrophotometer (uses light scattering)
  74. disadvantage of spectrophotometer
    cant tell if cells are dead or alive
  75. in spectrophotometer the solution must be 10^7-10^10 cells/ml
  76. 3 viable counts characteristics
    • counts only cells able to reproduce
    • requires time to form colonies
    • viable counts usually lower than direct counts
  77. cells are synthesizing materials and are not dividing
    lag phase
  78. exponential growth, doubling of growth
    log phase
  79. log phase increases linearly
  80. cells are no longer growing
    stationary phase
  81. 4 phases of the growth cycle in a liquid batch culture
    • lag phase
    • log phase
    • stationary phase
    • death phase
  82. g=t/n generation time
    k=n/t mean growth rate constant
  83. cells secrete material to hold to a surface
  84. 4 characteristics of biofilms
    • cells act together
    • cells signal each other
    • protects against dispersion
    • prevent antibiotics from infiltrating
  85. when cells act together in biofilms they could be from multiple or single species
  86. when cells signal to each other in biofilms
    quorum sensing
  87. when bacteria are faced with environmental stress, they undergo molecular reprogramming such as changes in cell structure
  88. these two spores can produce dormant spores that are heat resistant
    • clostridium
    • bacillus
  89. when starvation initiates, an 8 hour genetic program occurs that involves
    an asymmetrical cell division process that produces a forespore and ultimately an endospore
  90. sporulation can be divided into discrete stages based primarily on morphological appearance
  91. 2 ways cells respond to a changing environment
    • heterocysts
    • myxospores
  92. in heterocysts, the different cells produce different nutrients
  93. What heterocyst cells produce energy
    vegetative cells
  94. what heterocyst cells fix nitrogen
  95. in response to the environment, these kind of cells form inside fruiting bodies
  96. the fruiting body formed by myxospores is a multicellular structure
  97. actinomycetes respond to the changing environments by
    forming spores
  98. when do actinomycetes form spores
    when food runs out
  99. 3 functions of the spores created by actinomycetes
    • produce aerial hyphae
    • protect
    • distributes cells
  100. micronutrients are required by cells because they are components of cofactors, what are cofactors
    small molecules that fit into specific enzymes and aid as catalysts
  101. how were microbes found
    DNA amplifying procedure called PCR can be used to screen for the presence of genes in soil and water samples and is compared to the DNA of similar genes from different organisms
  102. the critical process of the carbon cycle involves these 2 metabolic groups of organisms
    • heterotroph
    • autotroph
  103. is a cell molecule critical to energy metabolism
  104. build biomass by fixing CO2 into complex organic molecules
  105. autotrophs gain energy through 2 metabolic routes
    • photoautotrophy
    • chemoautotrophy
  106. produces E from oxidizing inorganic molecules such as iron. E is used to fix CO2 into biomass
  107. a type of photosynthetic microorganism produced most of the oxygen we breathe and form the base of the food chain
  108. nitrifying bacteria gain E by oxidizing ammonia to produce nitrate
  109. E stored by an electrical potential across the membrane is known as
    membrane potential
  110. chemical energy in a cell
  111. 2 types of E useful to the cell
    • chemical
    • electrochemical
  112. how is membrane potential generated?
    when chem E is used to pump protons outside of the cell so the proton conc is greater outside, an electrical gradient across the cell membrane is generated
  113. capable of utilizing photosynthesis or heterotrophic respiration depending on environmental conditions
  114. 3 ways selective permeability is achieved
    • use of substrate specific carrier proteins in mem
    • aid of nutrient binding proteins that patrol the periplasmic space
    • action of mem spanning pro channels or pores
  115. nutrients that aren't permeable to the mem, microbes secrete digestive enzymes that breakdown the molecule into smaller compounds
  116. facilitated transport cannot move a molecule against its gradient
  117. most important facilitated diffusion transporters are those of the aquaporin family that transport water and glucose
  118. most common chemical gradient used are those of ions, specifically +
  119. electron neutral coupled transport in which there is no transfer of charge antiporter
    Na/H antiporter
  120. a healthy cell maintains proper charge balance using the electron transport chain to move protons in and out of cell, nonbalanced mem, it cannot carry out simple transport that it needs to sustain life
  121. major function of proton transport is to create the PMF that powers ATP synthesis
  122. ABC transporters are used as multidrug efflux pumps that allow microbes to survive exposures to hazardous chemicals
  123. microbes have the fastest and slowest growth rates of known organisms
  124. the environmental habitat that a species inhabits is based on one main criterion
    the tolerance of that organisms proteins and other macromolecular structures to the physical conditions within that niche
  125. 4 environmental limits of microbial growth
    • temp
    • ph
    • osmolarity
    • oxy
    • pressure
  126. growth rates increase with temp but if too high proteins denature
  127. type of microbe that can withstand 0-20 C
  128. type of microbe that can withstand 12-45 C
  129. type of microbe that can withstand 40-80 C
  130. type of microbe that can withstand 65-113 C
    extreme thermophiles
  131. what is a microbes response to high temp
    heat shock response
  132. 2 occurrences to heat shock response
    • emergency proteins produced
    • keep proteins from denaturing
  133. 2 kinds of emergency proteins produced in heat shock response
    • chaperones
    • proteases
  134. what 3 cause heat shock response
    • heat
    • high salt conc
    • arid conditions
  135. are adapted to high pressures
  136. they can grow at high but not too high of pressure
    barotolerant organisms
  137. they die at high pressure
    barosensitive organisms
  138. measure of how much water is available for use
    water activity
  139. the measure of the # of solute moleules in a solution
  140. this is inversely related to water activity
  141. these help protect the cell from osmotic stress
  142. solutes raise osmolarity
    high osmolarity reduces available water
  143. these organisms require high conc of NaCl and live in salt seas
  144. ph levels alter the conc of protons
  145. bacteria regulate internal ph
  146. these organisms grow at a pH of 5-8 and have bacteria in their gut
  147. these organisms grow at pH of 0-5
  148. grow at a pH of 9-11
  149. can only grow in O2
    strict microbes
  150. grow only at lower O2 levels
  151. die in the presence of O2
    strict anaerobes
  152. grow in oxygen while retaining a fermentation based metabolism
    aerotolerant anaerobes
  153. anaerobes pass electrons to different ultimate electron acceptors
  154. have inorganic electron acceptors
    anaerobic respiration
  155. have substrate level phosphorylation as electron acceptors
  156. two enzymes exist to neutralize the toxic forms of oxy formed as byproducts of reduction of oxygen
    • catalase
    • superoxide dismutase
  157. 4 types of toxic oxygen
    • superoxide O2-
    • hydrogen peroxide
    • hydroxyl radical OH.
    • water
  158. 4 ways to control measures of microbes
    • sterilization
    • disinfection
    • antisepsis
    • sanitation
  159. killing of all living organism
  160. killing or removal of pathogens from inanimate objects
  161. killing/removal of pathogens from the surface of living tissues
  162. reducing the microbial pop to safe levels
  163. D-value
    decimal reduction time (time to kill 90%)
  164. 2D-values
    time to kill 99% of cells
  165. antimicrobial agents decrease D-value
  166. moist heat is more effective than dry heat
  167. boiling water kills most cells
  168. killing spores and thermophiles usually requires a combo of high pressure and temp (autoclave)
  169. steam autoclave
    high heat and pressure for 20 min
  170. diff time and temp combos can be used for this
  171. in pasteurization low temp=long time high temp=short time
  172. this slows growth and does not kill all bacteria
    cold temp (refrigeration)
  173. viruses are not removed in this method of physical agents
  174. 2 functions of disinfectants
    • kills disease causing organisms
    • destroys eukaryotic cells
  175. this chemical agent is benchmark comparison to phenol and examples of it are chlorine and iodine
  176. this chemical agent is less toxic for living tissues and has conc
  177. 3 chemicals that damage proteins, lipids, and DNA
    • ethanol
    • iodine
    • chlorine
  178. commercial disinfectants and antiseptics are used to reduce or eliminate microbial content from objects
  179. this chemical agent selectively kills microbes and may not work on all species
  180. 3 characteristics of antibiotics
    • kills selective microbes
    • has minimal effect on eukaryotic cells
    • interferes with bacterial specific enzymes
  181. slow growing bacteria take longer to die
  182. this blocks cell wall synthesis
  183. good bacteria that displace disease organisms from tissues
  184. bacteria can undergo cell diff in response to environmental stress
  185. a medium containing bile salts and crystal violet selects for growth against
    gram positive
  186. if 1 ml of a 10^-4 dilution of a cell culture yields 98 colonies on an agar plate, how many colony forming units/ml are there in the original culture?
  187. endospores are resistant to many stresses that would kill vegetative cells
  188. endospores are durable and can remain viable for years
  189. if an enzyme of the PTS system was nonfunctional, the import of all substrates dependent on the PTS system would eventually stop
  190. these help move iron into bacteria
  191. if a bacterium can divide once an hour, after 5 hours, 1 bacterium will yield
    32 bacteria
  192. how is a continuous culture different from a batch culture
    new media is added and old media is removed
  193. biofilms may cause health problems for humans
  194. complex media are easier to prepare than synthetic media and bacteria grow faster on complex
  195. cyanobacteria is an example of
  196. cells are more negative inside, so when couple transport moves nutrients into the cell against their conc gradient is most likely to occur along
    with the electrical gradient of + ions into the cell
  197. these kind of transporters bind ATP on the intracellular side of the cell mem
    ABC transporters
  198. a permease that moves an uncharged sugar into the cell along with a protein, this is classified as
    electrogenic symporter
  199. these organisms need to ingest reduced carbon
  200. autotrophs are self feeding
    lithotrophs generate ATP from reduced inorganic compounds
    phototrophs generate ATP through light E
  201. of cells in batch culture, they will not remain at a constant mass
  202. a bacterial pathogen that can cause an infection in the blood is most likely a
  203. barophiles are also psychrophilic because that are usually found in cold ocean depths
  204. organisms with high rate of growth at low nutrient conc
  205. organisms that must use O2 as a final electron acceptor in ETC are
    strict aerobes
  206. piezophiles are also known as
  207. aerobes may tolerate the presence of O2 because they have the enzyme
    superoxide dismutase
  208. is the addition of nutrients to an ecosystem
  209. eutrophication may lead to decreased microbial diversity
  210. many alkalphiles have a sodium motive force because it will be hard to maintain a PMF in an alkaline environment
  211. phage therapy refers to
    the idea that phages could be used to treat bacterial diseases
  212. bacteria cannot regulate their temp
  213. chemotrophs whether they be auto or hetero oxidize and reduce compounds to get E
  214. in chemotrophy, the amnt of E gained from Ox a compound if related to the compounds red state. The more red the compound is, the more e- it has to give up and the high the PE yield.
  215. chemoautotrophy is the same as
  216. fungi require complex organic molecules for their growth; some of their lifestyles involve these 3
    • predation
    • parasitism
    • scavenging the dead
  217. obligate intracellular bacteria lose metabolic pathways provided by their host and develop requirements for growth factors supplied by their host
  218. autotrophs male complex organic molecules that are consumed by
  219. eukaryotes carry out only a limited range of heterotrophic and photo rxns
  220. how do symports and antiports function
    by alternatively opening one end or the other of the channel that spans the membrane
  221. the inside of the cell has to be kept negative while the outside is to remain positive
  222. ABC transporter consists of 2 hydrophobic proteins, that form a membrane channel and two peripheral cytoplasmic proteins that contain a highly conserved amino acid motif involved with binding ATP
  223. amino acid sequence found in a family of proteins
  224. the uptake systems of ABC transporters possess an additional extracytoplasmic protein called
    substrate binding protein
  225. SBP have a high affinity for their matched solutes, their use increases the efficiency of transport when conc of solutes are low
  226. SBP binds to the face of the protein to open the channel after a structural change is made to open
  227. once the signal is received from the opened channel with the SBP, the nucleotide binding proteins start to hydrolize ATP and signal the channel to open the cytoplasmic side to allow the entrance of solutes
  228. Fe scavenger molecules secreted from siderophores occurs when intracellular iron conc is low
  229. PTS is a well characterized group trabslocation system present in many bacteria
  230. eukaryotes undergo exocytosis to and endocytosis to bring in and take things across the cell membrane, they also have pumps as well
  231. lysosomes bind with phagosomes to creat phaglysosomes which help the digestive enzymes breakdown the endocytosed material
  232. this medium is useful when
    studying the growth characteristics of a single strain of species
  233. this kind of media is useful when trying to separate mixtures of diff organisms as they are found in the natural environment
    solid media
  234. spread plate starts from a liquid batch of bacteria, a series of tenfold dilutions is made and a small amount od each dilution is placed directly on the surface of the agar plates
  235. an organism that successfully replicates to form a colony
    viable organism
  236. CFU are chains of cells that have not split and look like a group of cells
  237. straightforward approach to monitoring pop growth is the measure the dry weight of a culture from cells collected by centrifuge, washed and dried in an oven then weighed.
  238. optical density of light scattered by bacteria is a very useful tool for estimating pop size
    however, the cell # is based on optical density, the cells volume can vary. It wont get an accurate measure of the number of cells
  239. if a cell produces 2 cells per generation then it will be 2^n
    n= the number of generations
  240. bacteria divide at a constant interval called
    gen time
  241. generation time varies with respect to the species, type of medium, temp, and ph
  242. no fresh media is added during the incubation of this kind of culture
    batch culture
  243. simplest way to model the effects of changing conditions is to culture the bacteria in a liquid medium within a closed system called
    batch culture
  244. batch media illustrate the remarkable ability of a bacteria to adapt to their environment
  245. a chemostat in which a photoelectric cell constantly monitors the optical densityof the culture
  246. biofilms can be cued by different environmental signals such as ph, Fe conc, temp, etc.
  247. starvation triggers a developmental cycle in which 100,000 of more individuals aggregate rising into a mound called a fruiting body
  248. are bacteria that form mycelia and sporangi analogous to a filamentous structures of eukaryotic fungi
  249. this allows us to study the biology of organisms that we cannot culture
    bioinformatics analysis
  250. this reveals whether or organism under study may possess specific metabolic pathways and regulatory responses
    genomic comparison
  251. every organism has an optimal that in which they perform their best at, while they also have a minimal and a maximum which limits them to what they can handle
  252. log k=C/T
  253. 2 reason as to why psychrophiles like cold
    • their proteins are less flexible and require less E to function
    • mem are more fluid at low temp
  254. psychrophile enzymes are of commercial interest because of their ability to carry out reactions at low temps, this could help with food processing
  255. thermophiles proteins do not unfold as easily so they can hold their shape at higher temps
  256. like all microbes thermophiles have chaperone proteins that help refold other proteins as they undergo thermal denaturation. Their genomes are packed with DNA binding proteins hat stabilize DNA and make it less likely to denature
  257. the membranes of the thermophiles glue together parts of the 2 hydrocarbon layers making them more stables
  258. chaperones function in heat shock response
    maintain protein shape and enzymes that change membrane lipid composition
  259. increased hydrostatic pressure and cold temps similarly reduce membrane fluidity
  260. most bacteria require how much water activity in order for them to grow
    greater than .91
  261. 2 other mechanisms microbes have to help minimize osmotic stress across membranes
    • protect their internal water by synthesizing or importing compatible solutes that increase intracellular osmolarity
    • have pressure sensitive channels that can be use to leak solutes out of the cell
  262. are small molecules hat do no disrupt normal cell metabolism even when present at high intracellular concentrations
    compatible solutes (these are used in microbes for minimizing osmotic stress)
  263. function of pressure sensitive channels in microbes as a minimizer to osmotic stress
    the channels are activated by rising internal pressure in cells immersed in a hypotonic medium, when activated the channels allow solutes to escape which lowers internal osmolarity
  264. % and M of NaCl do halophiles need in order to grow
    % and M of NaCl do most bacteria need to grow
    • 10-20% 2-4M
    • .2-5% .1-1M
  265. how can halophiles live in high salt conc environments?
    they use special pumps to secrete the Na+ and replace it with other cations such as potassium
  266. high conc of hydronium or hydroxyl ions in a solution will limit the growth of microbes
  267. Altering the PH can alter changes of various amino or carboxyl groups within a protein which can change the proteins structure and activity
  268. the Ph and the osmolarity of a microbe is not dictated by its outside environment
  269. the cell can become acidic when weak uncharged permeable acids can cross the cell and then dissociate which releases a proton that acidifies the internal pH
  270. these organisms can oxidize reduced metals and generate strong acids such as sulfuric acid. They are also known as chemoautotrophs
  271. these organisms are commonly found in saline soda lakes which have high salt conc and pH values
  272. most alkaliphiles use a Na motive force in addition to PMF because external protons are in such short supply at the alkaline pH
  273. when cells are placed in pH conditions below their optimum, protons can enter the cell and lower the internal pH to lethal levels.
  274. Microbes can prevent the unwanted influx of protons by exchanging extracellular potassium for intracellular protons when internal pH gets too low
  275. Under extreme alkaline conditions, the cells can use the Na/H antiporters to recruit protons into the cell in exchange for expelling Na
  276. bacterial physiology undergoes a major molecular reprogramming in response to hydrogen ion stress. some of the physiological responses are these 2
    • modifications in mem lipid composition
    • enhanced pH homeostasis
  277. acid and alkaline stress responses occur when
    • placing given species under pH conditions that slow its growth.
    • the cell increases the level of proteins designed to mediate pH homeostasis and protect cell constitute
  278. the use of O2 as the terminal electron acceptor is called
    aerobic respiration
  279. electrons are pulled from various E sources. They do this by extracting the E in stages and using it to move protons out of the cell. This unequal distribution of H+ across the mem produces a transmembrane electrochemical gradient called PMF
  280. this enzyme removes oxide in anaerobes
    superoxide dismutase
  281. these 2 enzymes remove hydrogen peroxide in anaerobes
    • peroxidase
    • catalase
  282. aerobes have resourceful enzyme systems that detect and repair macromolecules damaged by oxidation
  283. facultative anaerobes
  284. these can only use fermentation as E but contain superoxide dismutase and catalase to protect them from reactive oxygen species
  285. anaerobic respiration
  286. fermentation depends on these two factors
    • the availability of O2
    • the amount of carbohydrates present
  287. 3 techniques for culturing anaerobes
    • special reducing agents
    • agar plates
    • anaerobic glove box
  288. this kind of technique, enzyme systems can eliminate dissolved oxy so that it can be added to ordinary liquid media
    special reducing agents
  289. this technique has the organisms streaked and placed into a sealed jar with a foil packet that releases H2 and CO2 gases
    agar plates
  290. this technique has the atmosphere removed by a vacuum and replaced with a mix of N2 and CO2 gases
    anaerobic glove box
  291. in result of a starvation response, the metabolic slowdown generates increased conc of critically important small signal molecules such as _____ and _____ which transforms gene expression
    • cyclic AMP
    • ppGpp
  292. when the environment continues to get worse, the organism has stress survival genes that become active, these genes protect against stressors such as reactive oxy rad or temp and pH extremes
  293. what happens when eutrophication occurs amongst microbes
    lead to bloom of microbes, an unrestricted growth consuming other nutrients to a degree that threatens the existence of competing species
  294. what causes eutrophication
    human activities
  295. antimicrobials can either inhibit growth or kill the cells completely
  296. the ability of an antimicrobial agent to kill microbes influence the D-value
  297. it takes all cell in a population a while to die because not all proteins and genes in a X are damaged by an agent at the same time
  298. assume all cells in a pop are identical
  299. vegetative cells
    activity growing orgainisms
  300. boiling water at 100 C can kill most vegetative cells
  301. the bombardment of foods with high E electromagnetic radiation
  302. 3 sources of irradiation
    • gamma rays
    • electron beams
    • xrays
  303. the amount of E transferred to food, microbes, or other substance being irradiated
    gray (Gy)
  304. parasites that have a large amount of DNA are killed rapidly by
    extreme low doses of radiation, D-values less than 0.1
  305. it takes more radiation to kill bacteria because they have less DNA/cell unit
    .3-.7 kGy
  306. viral pathogens have the smallest amount of nucleic acid making them resistant to irradiation doses
  307. irradiation is effective in eliminating parasites and bacteria but not viruses or prions
  308. those that don't contain nucleic acid are only inactivated by irradiation at extremely high doses
  309. Deinococcus radiodurans  is known as conan the bacterium because
    this microbe has the greatest ability to survive radiation of any known organism
  310. a chemical on a dirty surface will bind to the inert organic matter and lower the agents effectiveness against microbes
  311. 4 factors that influence the efficiency of a given chemical agent
    • presence of an organic matter
    • the kinds of organisms present
    • corrosiveness
    • stability, odor, and surface tension
  312. the chemical agent should be effective against a broad range of pathogens
  313. the disinfectant should not corrode the surface ex skin
  314. the chemical should be stable upon storage, possess a neutral or pleasant odor or have low surface tension so it can penetrate cracks and crevices
  315. 3 reasons why phenolics are useful disinfectants
    • denature proteins
    • effective in presence of organic material
    • remain active on surfaces long after application
  316. detergents can also be antimicrobial agents, the hydrophob and phil ends of detergent molecules will emulsify fat into water
  317. + are useful as disinfectants because they contain + charges that can gain access to the negatively charged bacterial cell and disrupt membrane
  318. very effective sterilization it destroys cell proteins and penetrates packing material
    ethylene oxide gas EtO
  319. chemical disinfectants are compared to one another based on the phenol coefficient
  320. are compounds produced by one living microorganism that kill other microorganisms
  321. the measure of how much more heat is needed to reduce D-value to 1/10 its original value
Card Set:
Microbiology exam 2
2013-10-14 23:58:22
sfsu microbio

microbio exam 2 chapter 4,5
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