Microbio Lab 5 Flashcards
Obligate (Strict) Aerobes
Bacteria must grow in oxgen because their metabolism requires oxygen. Oxygen is utilized as the electron acceptor in the electron transport chain.
Ex. Pseudomonas, Micrococcus, Bacillus
Microaerophiles
Aerobic bacteria prefer to grow in oxygen concentrations of 2-10% rather than the 20% found in the atmosphere.
Ex. Helicobacter pylori in stomach
Facultative Anaerobes
Bacteria that grow well aerobically but can also grow in the absence of oxygen by switching to fermentation for energy production.
Ex. Escherichia coli
Aerotolerant Anaerobes (Obligate Fermenters)
Bacteria can tolerate oxygen and grown in its presence but they do not require oxygen for energy production. They produce their energy strictly by fermentation.
Ex. Enterococcus faecalis, Streptococcus pyogenes
Obligate (Strict) Anaerobes
Bacteria that cannot tolerate oxygen and must be cultured under conditions in which oxygen is eliminated. They carry out anaerobic respiration in which inorganic compounds replace oxygen as terminal electron acceptors in the electron transport chain, or fermentation.
Ex. Clostridium, Methanococcus, Bacteroides
catalase
degrades hydrogen peroxide into oxygen and water
peroxidase
degrades hydrogen peroxide
Superoxide dismutase
will act on the superoxide anion and convert it to oxygen and hydrogen peroxide
FTM (fluid thioglycollate medium)
rich, liquid medium that supports the growth of both aerobic and anaerobic bacteria. Thioglycollate and cystine reduce oxygen to water. The dye resazurin turns pink in presence of oxygen (usually at top of agar).
GasPak anaerobic jar
Hydrogen is generated in jar which removes oxygen by forming water. Palladium pellets catalyze the reaction at room temp. In anaerobic conditions, the indicator strips turns blue.
psychrophiles
optimal growth between -5ºC and 15ºC; these bacteria can be found in the supercooled water of the Arctic and Antarctic.
mesophiles
optimal growth between 25ºC and 45ºC; most bacteria fall into this class.
thermophiles
optimal growth between 45ºC and 70ºC; bacteria occur in soils where midday temperatures can reach greater than 50ºC or in compost files where fermentation activity can cause temperatures to exceed 60-65ºC
hyperthermophiles
growth optimum above 75ºC; many of the Archaea occupy environments that are heated by volcanic activity where water is superheated to 100ºC. Bacteria have been isolated from thermal vents deep within the ocean floor and from volcanic heated hot springs.
psychrotrophs
capable of growth at low temperatures
neutrophiles
bacteria that grow at or near neutral pH
acidophiles
bacteria that grow at an acidic pH
alkaliphiles
bacteria that grow at an alkaline pH
osmosis
water diffuses from areas of low solute concentration where water is more plentiful to areas of high solute concentration where water is less available; water naturally diffuses into a cell because their are more nutrients in the cytoplasm
hypotonic
a medium where solute concentrations on the outside of the cell are lower than the cytoplasm
isotonic
environments where the solute concentration is the same inside and outside the cell
hypertonic
environments where the solute concentration is greater on the outside of the cell relative to the cytoplasm, and causes the water to diffuse out of the cytoplasm
plasmolysis
when water diffuses out of the cytoplasm; loss of water, dehydration of the cytoplasm, and shrinkage of the cell membrane away from the cell wall; considerable and irreversible damage can occur in the metabolic machinery
obligate halophiles
bacteria that require high concentrations of sodium chloride to grow
halotolerant
organisms that do not require salt but are capable of growth in moderate concentrations
osmophiles
organisms able to grow in environments where sugar concentrations are excessive
complex medium
medium where the exact amounts of the individual amino acids, vitamins, growth factors, and other components that make up the medium are not exactly known
defined medium
medium where the specific chemical composition is known and the individual components are weighed out exactly to make up the medium
heterotrophs
organisms that obtain their carbon from organic compounds such as polysaccharides, carbohydrates, amino acids, peptides, and proteins
autotrophs
organisms that derive
chemoorganotrophs
organisms that derive their energy from the breakdown of organic molecules by fermentation or respiration
Chemolithotrophs
organisms that oxidize inorganic ions such as nitrate or iron to obtain energy to fix carbon dioxide
photoautotrophs
organisms that contain photosynthetic pigments such as chlorophyll that convert solar energy into chemical energy by the process of photosynthesis
photoheterotrophs
organisms that derive energy from photosynthesis but their carbon needs come from growth on organic molecules such as succinate or glutamate
differential medium
contains substances that cause some bacteria to take on an appearance that distinguishes them from other bacteria
selective medium
media made with components that will allow certain bacteria to grow but will inhibit others from growing
nutrients in media
carbon source energy source nitrogen minerals vitamins and growth factors water
agar
a complex polysaccharide isolated from seaweed; added in a concentration of 1.5% to solidify liquid media
nitrogen in media
essential element in biological molecules such as amino acids, nucleotide bases, and vitamins.
minerals in media
essential in bacterial metabolism because they are cofactors in enzymatic reactions and are integral parts of molecules such as cytochromes, bacteriochlorophyll, and vitamins; most are required in small or catalytic amounts
vitamins and growth factors in medium
serve as coenzymes in metabolismh
TGYA shake
solid medium that is inoculated in a liquified state, shaken to mix the organisms throughout and allowed to solidify; after
incubation
one determines the oxygen requirements on the basis of where growth occurs in the shake tube; top, middle, or bottom.
Brewer’s anaerobic jar
solid medium for culturing anaerobic bacteria in agar plates; it contains thioglycollate for reducing oxygen and resazurin for indicating the presence of oxygen; essential that plates be incubated in an oxygen free-environment
What is the role of oxygen in aerobic respiration?
Oxygen in the final electron acceptor
What types of metabolism can occur in the absence of oxygen?
fermentation and anaerobic respiration
Name two enzymes that are present in obligate aerobes but lacking in obligate anaerobes.
superoxide dismutase- acts on superoxide anion and converts it to oxygen and hydrogen peroxide
catalase- degrades hydrogen peroxide into oxygen and water
Differentiate between a microaerophile and an aerotolerant organism?
Microaerophiles need a small amount of oxygen and aerotolerants do not need oxygen but can survive in its presence
Why is resazurin a useful media additive for the study of anaerobes?
It is an indicator for the presence of oxygen by changing colors
Why is a GasPak anaerobic jar necessary for the culture of anaerobes on Brewer’s anaerobic agar plates but not in tubes of fluid thioglycollate medium (FTM)?
The surface of the agar is oxygen rich so the GasPak is necessary to remove oxygen. In the depths of the tube of FTM, conditions are already anaerobic so the GasPak in unnecessary
Where in the human body would you expect to find an obligate aerobe or an obligate anaerobe?
obligate aerobe- lungs, heart, blood vessels
obligate anaerobe- intestines
Maximal enzyme activity will..
occur at an optimum temperature
In what environment might the following organisms be found?
a. hyperthermophile
b. thermophile
c. mesophile
d. psychrophile
a. hyperthermophile - above 75 º C (volcanic thermal vents, hot springs)
b. thermophile - 45 to 70 º C (compost piles, soil)
c. mesophile - 25 to 45 ºC (humans, lakes)
d. psychrophile - (-5) to 15 ºC (supercooled waters of Arctic and Antarctic)
Differentiate between psychrophile and psychrotroph.
Psychrophiles grow best at low temperatures and psychrotrophs can grow at low temperatures but it is not their optimal growth temperature
Why are psychrotropic bacteria of concern to those in the food industry?
They can spoil food even at low temperatures.
What is the optimum growth temperature for most human pathogens?
37 ºC (temp of the human body)
Name three cellular components involved in metabolism that are influenced by temperature changes, and explain the changes that occur to those components.
cell membranes - fluidity changes as temperature is lowered and transport of nutrients is decreased; if temperature becomes too high, membrane lipids can be destroyed resulting in serious damage to the membrane and cell death
enzymes - at high temperatures enzymes will begin to denature and lose activity; below the minimum temperature chemical activity slows and denaturation can also occur
ribosomes - at extreme temperatures they cease to function
Which has a greater impact on the survival of an organism, temperatures above its maximum temperature or temperatures below its minimum temperature?
Temperatures above the maximum temperature because they are more likely to denature proteins and cease activity.
How does pH negatively affect the metabolism of microorganisms?
It affects the solubility of molecules and causes proteins to denature and lose enzymatic activity
How would the pH of the culture medium be influenced by sugar fermentation? By urea hydrolysis?
sugar fermentation would lower the pH
urea hydrolysis would raise the pH
Helicobacter pylori survives in the acidic environment of the human stomach, but this organism is actually a neutrophile. How is this possible?
It produces urease, which catalyzes urea hydrolysis and raises the pH in the area around it
water activity
the availability of water; determined by measuring the ratio of the water vapor pressure of a solution to the water vapor pressure of pure wate
Why are bacteria generally resistant to hypotonic environments, whereas animal cells are not?
Bacteria have cell walls and animal cells do not.
For each salt concentration used in this exercise, indicate whether it represents an isotonic, hypotonic, or hypertonic environment for the bacterial cells.
a) 0.5%
b) 5%
c) 10%
d) 15&
a) isotonic
b) hypertonic
c) hypertonic
d) hypertonic
How do hypertonic environments negatively affect most bacterial cells?
The water leaves the cell causing the membrane to pull away from the cell wall and disrupting the membrane.
Why are staphylococci will suited for the colonization of skin?
They are halotolerant and do not need salt but they are capable of growth in moderate concentrations (11%)
Differentiate between halophiles and osmophiles. Which type would more likely cause spoilage of jams and jellies?
Halophiles prefer to grow in high salt and osmophiles prefer high sugar concentrations. Osmophiles are more likely to cause spoilage of jams and jellies.
thermoduric
survive but do not grow at high temperatures
