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Microbiology > Ch. 6 microbial nutrition and growth > Flashcards

Ch. 6 microbial nutrition and growth Flashcards

1
Q

What is an essential nutrient?

A

any substance that must be provided to an organism

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2
Q

What are macronutrients?

A

Required in relatively large quantities and plays a principal role in cell structure and metabolism
ex. Carbon, hydrogen, nitrogen, phosphorous, oxygen

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3
Q

What is a micronutrient?

A

present in much smaller amounts and are involved in enzyme function and maintenance of protein structure
- also called trace elements
ex. manganese, zinc, nickel, potassium

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4
Q

What is a heterotroph?

A

an organism that must obtain its carbon in an organic form

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5
Q

What is an autotroph?

A

an organism that uses inorganic CO2 and its carbon source
- has the capacity to convert CO2 into organic compounds
- not nutritionally dependent on other living things

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6
Q

What is a phototroph?

A

microbe that photosynthesizes

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7
Q

What is a chemotroph?

A

Microbe that gets its energy from chemical compounds

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8
Q

What is a chemoheterotroph?

A
  • derive both carbon and energy from organic compounds
  • Process these molecules through cellular respiration or fermentation
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9
Q

What are saprobes?

A
  • free-living organisms that feed on organic detritus from dead organisms
  • decomposers of plant litter, animal matter. and dead microbes
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10
Q

What are the characteristics of parasites?

A
  • Derive nutrients from the cells or tissue of a living host
  • they are pathogens = case damage to tissue or even death
  • range from viruses to helminths
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11
Q

What are the types of parasites?

A
  • ectoparasites - live on the body
  • endoparasites - live in the organs and tissues
  • intracellular parasites - live within the cells
  • obligate parasites - unable to grow outside of a living host
  • Leprosy bacillus and syphilis spirochete
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12
Q

What are cardinal temperatures?

A

the range of temperatures for the growth of a given microbial species

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13
Q

What is the minimum temperature?

A

The lowest temp that permits a microbe’s continued growth and metabolism; below this temp its activities stop

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14
Q

What is the maximum temperature?

A

the highest temp at which growth and metabolism can proceed before proteins are denatured

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15
Q

What is the optimum temperature?

A

An intermediate between the minimum and maximum that promotes the fastest rate of growth and metabolism

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16
Q

What are the characteristics of psychrophiles?

A
  • obligate with respect to cold and cannot grow above 20 C
  • grows well in refrigerators
  • Natural habitats are cold waters, polar ice, and deep ocean
  • rarely pathogenic
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17
Q

What are the characteristics of psychotrophs?

A
  • grow slowly in the cold but have an optimum temp between 15-30C
  • S. Aureus and Listeria monocytogenes can grow at refrigerator temps and cause food-borne illness
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18
Q

What are the characteristics of mesophiles?

A
  • the majority of medically significant microbes
  • inhabit animals, plants, soil, and waters
  • Human pathogens have optimum temperatures between 30-40C
19
Q

What are the characteristics of thermophiles?

A
  • grow optimally at temps greater than 45C
  • live in soil and water associated w/ volcanic activity, compost piles, and sunny habitats
  • Most eukaryotic forms can’t survive above 60C
20
Q

What gasses influence microbial growth?

A
  • O2 - has the greatest impact on microbial growth; an important respiratory gas and oxidizing agent
    -CO2
21
Q

How do microbes process oxygen?

A

as oxygen enters cellular rxns it is transformed into several toxic products:
- singlet oxygen (O)- extremely reactive molecule that can damage and destroy a cell by oxidation of membrane lipids
- superoxide ion (O2-) - highly reactive
- Hydrogen peroxide (H2O2) - toxic to cells and used as a disinfectant
- Hydroxyl radical (OH-) - highly reactive

22
Q

How do microbes protect themselves against damage from oxygen by-products?

A
  • cells develop enzymes that scavenge and neutralize reactive oxygen by-products
  • superoxide dismutase = converts superoxide ion into hydrogen peroxide
  • Catalase = converts hydrogen peroxide into water
23
Q

What are the characteristics of Aerobes?

A

can use gaseous oxygen in their metabolism and possesses the enzymes needed to process toxic oxygen products
- obligate aerobe - an organism that can’t grow without oxygen
- ex. most fungi, protozoa, and bacteria such as bacillus spp. and mycobacterium tuberculosis

24
Q

What are the characteristics of microaerophiles?

A

harmed by normal atmospheric concentrations of oxygen but require a small amount of it in metabolism
-ex. Organisms that live in the soil or water or in mammalian hosts, not directly exposed to atmosphere (helicobacter pylori, borrelia burgdorferi)

25
What are the characteristics of facultative anaerobes?
do not require oxygen for metabolism but use it when present - many gram-negative intestinal bacteria, staphylococci
26
What are the characteristics of anaerobes?
lack the metabolic enzyme systems for using oxygen in respiration - obligate anaerobes - also lack enzymes for processing toxic oxygen and die in its presence ex. many oral bacteria, intestinal bacteria
27
What are the characteristics of Aerotolerant anaerobes?
do not utilize oxygen but can survive and grow to a limited extent in its presence - not harmed by oxygen, mainly because they possess alternate mechanisms for breaking down peroxides and superoxides ex. Certain lactobacilli and strep, clostridal spp.
28
What is the pH required for most organisms?
- the majority of organisms live or grow in habitats between pH 6-8 - organism that can grow at pH extremes still maintain an internal pH near neutral
29
What are osmophiles?
Live in environments with high solute concentration
30
What are the characteristics of halophiles?
- prefer high salt concentrations - obligate halophiles - halobacterium and halococcus grow optimally at solutions of 25% NaCl but require at least 9% NaCl - Facultative halophiles - resistant to salt, even though they do not normally reside in high salt environments S. aureus can grow on NaCl media ranging from 0.1%-20%
31
What is symbiosis?
General term to denote a situation in which two organisms live together in a close relationship - symbiotes = members of a symbiosis
32
What are the 3 types of symbiosis?
1. mutualism - organisms live in an obligatory but mutually beneficial relationship ( our intestinal bacteria) 2. Commensalism - the partner called the commensal receives benefits, while its partner is neither harmed nor benefited (ex. bacteria on our skin) 3. parasitism - host organism provides the parasitic microbe with nutrients and a habitat; host suffers from relationship (ex. disease causing bacteria)
33
What is antagonism?
an association between free-living species that arises when members of a community compete - the first microbe has a competitive advantage by increasing the space and nutrients available to it
34
What is synergism?
an interrelationship between two organisms that benefits them but is not necessary for survival
35
What are biofilms?
mixed communities of bacteria and other microbes that are attached to a conditioned surface and each other
36
What are the steps in biofilm formation?
1. a "pioneer" colonizer initially attaches to a surface and becomes sessile 2. other microbes attach to those bacteria or a polymeric sugar or proteins substance secreted by the microbial colonizers (EPS) 3. attached cells are stimulated to release chemicals as the cell population grows
37
What is the process of binary fission?
- one cell becomes two - parent cell enlarges - duplicates its chromosomes - starts to pull its cell envelope together to the center of the cell - cell wall eventually forms a complete central septum - time to complete binary fission = generation/doubling time
38
What is generation time?
the length of the generation time is a measure of the growth rate of an organism - average time = 30-60 min - shortest time = 10-12 min - mycobacterium leprae generation time = 10-30 days - most pathogens have relatively short generation times
39
What is a growth curve?
a predictable pattern of bacterial population growth in a closed system
40
What are the 4 stages of the population growth curve?
- lag phase - exponential (log) phase - stationary phase - Death phase
41
What is the lag phase?
- the "flat" period of growth Do to: - newly inoculated cells that require a period of adjustment, enlargement, and synthesis - cells are not yet multiplying at their max rate - population of cells is so sparse or dilute that sampling misses them
42
What is the exponential growth (log) phase?
- growth curve increases geometrically - will continue as long as cells have adequate nutrients and environment is favorable
43
What is the stationary phase?
- cell birth and cell death rates are equal - cell division rate is slowing down - caused by depleted nutrients and oxygen, plus the excretion of organic acids and biochemical pollutants into the growth medium
44
What is the death phase?
- cells begin to die at an exponential rate due to the buildup of wastes - the speed with which death occurs depends on the resistance of the species and how toxic the conditions are - slower than the exponential growth phase

Microbiology (10 decks)

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