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Chapter 6-Microbiology Questions and Answers 100% Accurate
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Chapter 6-Microbiology
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Chapter 6-MicrobiologyWhat are the physical requirements for microbial growth? - answer Temperature, pH,
and osmotic pressure
Temperature - answer Most microorganisms grow well at the temperatures that humans
favor; but there are three major ranges of temperature: psychrophile’s, mesophiles,
thermophiles
psychrophile’s - answer cold-loving microbes (-10 to 20)
Mesophiles - answer moderate-temperature loving microbes (10 to 50)
Thermophiles - answer heat loving microbes (40 to 73)
Maximum growth temperature - answer highest temperature at which growth is possible
optimum growth temperature - answer temperature at which the species grows back
minimum growth temperature - answer lowest temperature at which the species will
grow
Typically the max and min growth temperatures are only about 30 degrees Celsius
apart
psychotrophs - answerfood microbiologists favor, this group is known for spoilage of
food
Why refrigerate? - answerbased on the principle that microbial reproduction rates
decrease at low temperatures (or entirely dormant)
hyperthermophiles or extreme thermophiles - answerarcahe; have an optimum growht
temperature of 80* C or more; live in hot springs and sulfur important in their metabolic
activity
What pH do bacteria typically grow in? - answerneutrality (between 6.5 adn 7.5)
Cutlured bacteria often produce acids that eventualy interfere with their own growth;
chemical buffers must be included in growth medium
acidophiles - answerremarkably tolerant of acidity
How do most microorganisms obtain all their nutrients? - answerthrough solution from
their surrounding water; thus they require water for growth;
, How does high osmotic pressure effect bacteria? - answerWhen concentration of
solutes is higher in the cell (hypertonic)
When concentration of solutes is higher outside the cell - answerCell will shrink,
removes necessary water
Plasmolysis - answershrinkage of the cell cytoplasm
Plasma membrane pulls away from the cell wall; addition of salts to a solution will
increase osmotic pressure (can be used for food preservation)
Extreme Halophiles - answeradapted well to high salt concentrations that they actually
require them for growth
Obligate halophiles - answerrequire salt for growth
Facultative halophiles - answerdo not require high salt concentrations but are able to
grow in salt concentrations up to 2%; few can tolerate even up to 15%
Typical medium composed of? - answer1.5% agar, the rest is water!; if all water, the
enviornment is hypotonic, water will move into the cell-lyses
What are the chemical requirements of microbial growth? - answercarbon, nitrogen,
suflur, phosphorus, trace elements, oxygen, and organic growth factors
Why carbon? - answerone of the most important requirements for microbial growth;
carbon is the structural backbone of living matter; it is neeed for all organic ompounds
that make up a living cell; half of the dry weight of a living cell is carbon
Chemoheterotrophs - answerget most of their carbon from the source of their energy
Nitrogen, sulfur, phosphorus - answerDNA and RNA and ATP synthesis: require
nitrogen and phosphorous
Protein synthesis: requires considerable amounts of nitrogen and some sulfur
Nitrogen 14% of dry weight; phosphours and sulfur 4%
What is nitrogen used for? - answerprimarily to form the amino group of the amino acids
for proteins
Nitrogen fixation - answeruses gaseous nitrogen N2 directly from the atmosphere
Other ways to get nitrogen: decomposing protein-containing material or NH4+
(ammonium ions), or nitrates
Source of sulfur - answerUsed to synthesize suflur-containing amino acids and vitamins
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