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Microbiology > Ch. 6 microbial nutrition and growth > Flashcards

Ch. 6 microbial nutrition and growth Flashcards

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Biology 101 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
Q

What are the characteristics of facultative anaerobes?

A

do not require oxygen for metabolism but use it when present
- many gram-negative intestinal bacteria, staphylococci

26
Q

What are the characteristics of anaerobes?

A

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
Q

What are the characteristics of Aerotolerant anaerobes?

A

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
Q

What is the pH required for most organisms?

A
  • 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
Q

What are osmophiles?

A

Live in environments with high solute concentration

30
Q

What are the characteristics of halophiles?

A
  • 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
Q

What is symbiosis?

A

General term to denote a situation in which two organisms live together in a close relationship
- symbiotes = members of a symbiosis

32
Q

What are the 3 types of symbiosis?

A
  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
Q

What is antagonism?

A

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
Q

What is synergism?

A

an interrelationship between two organisms that benefits them but is not necessary for survival

35
Q

What are biofilms?

A

mixed communities of bacteria and other microbes that are attached to a conditioned surface and each other

36
Q

What are the steps in biofilm formation?

A
  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
Q

What is the process of binary fission?

A
  • 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
Q

What is generation time?

A

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
Q

What is a growth curve?

A

a predictable pattern of bacterial population growth in a closed system

40
Q

What are the 4 stages of the population growth curve?

A
  • lag phase
  • exponential (log) phase
  • stationary phase
  • Death phase
41
Q

What is the lag phase?

A
  • 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
Q

What is the exponential growth (log) phase?

A
  • growth curve increases geometrically
  • will continue as long as cells have adequate nutrients and environment is favorable
43
Q

What is the stationary phase?

A
  • 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
Q

What is the death phase?

A
  • 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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