Microbiology Exam 2 (Microbial Growth)
Identify/define: psychrophiles
-"cold loving organisms" >Psychrophiles are extremophilic organisms that are capable of growth and reproduction in cold temperatures, ranging from −20 °C to +10 °C. >Psychrophilic ("cold loving") microorganisms , particularly bacteria , have a preferential temperature for growth at less than 59° Fahrenheit (15° Celsius).
Identify/define: mesophiles
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 20 and 45 °C (68 and 113 °F).
Spectrophotometer-How (in general terms) does this work?
A spectrophotometer is an instrument that measures the amount of photons (the intensity of light) absorbed after it passes through sample solution. determine the concentration of a compound or particles in a solution or suspension. Light of a pre-selected wavelength is shone through a chamber that houses the sample. The sample particles, bacteria for example, will absorb some of the light.
Identify/define: thermophiles
A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between 41 and 122 °C (106 and 252 °F). Many thermophiles are archaea.
Identify/define: selective medium
Allows some microbes to grow, not others. >Selective and differential media are used to isolate or identify particular organisms. Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms.
Candle jar-How (in general terms) does this work?
An alternative to the anaerobic jar is a candle jar in which a candle is placed in the jar and the lid closed to enable the flame to use the available oxygen. typically, this system not all of the oxygen is used.
Compare and contrast plate counts and direct cell counts of bacteria as to the advantages and disadvantages of each.
Direct cell counts- (direct measurement): counting the microbes. 2 ways this can be done: Petroff-Hauser: holds liquid+has grid+counts how many cells. OR Coulter counter: light beam/laser-material is counted each time beam is broken. CON- You can count/include dead bacteria. Plate counts-You have to dilute and wait overnight, less chance of counting dead cells. > The plate count method or spread plate relies on bacteria growing a colony on a nutrient medium. The colony becomes visible to the naked eye and the number of colonies on a plate can be counted.
Identify/define: complex medium
Doesn't have precise measured nutrients and has extracts (like yeast) etc. >Complex Media- non-synthetic, non-defined and quite rich. Nutrient Agar (NA)is a complex media.Trypticase Soy Agar is another example of a complex media
Identify/define: aerotolerant anaerobe
Doesn't use O2 (oxygen), but isn't harmed by it >Aerotolerant organisms, which cannot use oxygen for growth, but tolerate its presence
Identify/define: obligate aerobe
If something HAS to have O2 (oxygen) >Obligate aerobes need oxygen because they cannot ferment or respire anaerobically
Identify/define: obligate anaerobe
Killed by O2 (oxygen) >Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
Identify/define: microaerophile
Little O2 (oxygen) loving. >A microaerophile is a microorganism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere
Anaerobic jar-How (in general terms) does this work?
Makes anaerobic environment >This method of anaerobiosis as others is used to culture bacteria which die or fail to grow in presence of oxygen When water is added to the pouch, the sodium borohydride, sodium bicarbonate, and citric acid react to form hydrogen and carbon dioxide. The palladium catalyzes a reaction between the hydrogen and the oxygen within the jar; this reaction creates water, which forms as condensation on the inside of the jar.
Identify/define: chemically defined medium
Precise measured nutrients in medium. >Microbiological Cultures. Culture medium or growth medium is a liquid or gel designed to support the growth of microorganisms. There are different types of media suitable for growing different types of cells
How does salting preserve food?
Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. (removes water)
Identify/define: differential medium
Something in it that causes different microbes to have different colony morphologies. >Organisms with differing growth characteristics typically show visible differences in growth when placed on differential media.
Chemostat-How (in general terms) does this work?
Used for bacteria growing in liquid medium. Liquid has food, buffer, takes out waste, and dead cells. Stops it(organism/bacteria) from dying off, or going into decline phase. Subculturing does the same thing. >A chemostat (from chemical environment is static) is a bioreactor to which fresh medium is continuously added, while culture liquid containing left over nutrients, metabolic end products and microorganisms are continuously removed at the same rate to keep the culture volume constant.
Describe the four (or five) phases of bacterial population growth and what is happening in each.
(1st)Lag phase- Growth isn't increasing too much. (2nd)Log exponential- growing very fast(bacteria). Antibiotics attack in this stage usually. (3rd)Stationary(equilibrium)- number of new cells is equal to number of dying cells (4th)Death(log decline)- Dying off (5th)Prolonged decline- Completely cells died off, dying.
