Week 4 Continued: Ex. 18, 21, 22

Question 1

Autotroph

Answer 1

(“feed-self”)

• utilizes inorganic carbon (CO2) as its source of carbon
  ex: Cyanobacteria
• use CO2 in the process of photosynthesis to synthesize their own carbohydrates

Question 2

Heterotroph

Answer 2

• organisms cannot synthesize organic molecules from CO2
• They must use preformed organic molecules in their environment as carbon sources
• most members of Domain bacteria are heterotrophs

Question 3

Fastidious

Answer 3

organisms that require unusual or complex nutrient mixtures to grow

ex: Neisseria
- these organisms required a nutrient-rich medium high in amino acids and iron
- Growth is enhanced by a high carbon-dioxide environment

Question 4

Complex Medium

Answer 4

• uses preparations of extracts from other organisms; extracts are not chemically definable (exact amount of each component in an extract is not known).
• extracts are obtained from animals, plants, or yeast
  ex: yeast extract agar and brain-heart infusion agar are examples

Question 5

Media is either classified as

Answer 5

• Complex medium
• Chemically defined medium
• Enriched medium

Question 6

Chemically defined medium

Answer 6

contains pure organic or inorganic compounds added in exact, finite amounts
-used for a narrow range of bacteria that are less fastidious

Question 7

Enriched medium

Answer 7

media to which specific nutrients are added to support growth of fastidious organisms;-like blood agar
-blood agar contains blood which provides necessary nutrients like iron and protein to support growth of very fastidious Streptococci

Question 8

Spectrophotometric measurements reflect either the ____

Answer 8

light absorbed (absorbance, turbidity) by the sample or the light transmitted (transmittance) through a culture

• both measurements are proportional to the number of bacteria in a solution
• The more Turbid the culture, the more bacteria are present
• The more cells that are present in the sample, the higher the absorbance
• High transmittance values indicate that more light is passing through the sample, which means there are fewer cells in the sample

Question 9

Anaerobic Respiration: Alternatives to O2

Answer 9

• alternatives to O2 are utilized as final electron acceptor in the electron transport chain. These alternatives include:
• Nitrate (NO3)
• Sulfate (SO)
• Sulfur (S)
• Carbonate (CO)

Question 10

Aerobic Cellular Respiration

Answer 10

• O2 acts as final electron acceptor in the electron transport chain located in the plasma membrane of bacteria
• The shuttling of electrons through the electron transport chain to O2 allows for the establishment of an electrochemcial gradient- differences in hydrogen ions (H+) and charge across the plasma membrane, which eventually results in the production of adenosine triphosphate (ATP): membrane-bound enzyme ATP synthase

Question 11

Fermentation

Answer 11

organic molecules like pyruvate and pyruvate derivatives act as the final electron acceptors, allowing glycolysis to continue in the absence of O2
-each round of glycolysis results in the net production of 2 ATPs per glucose

Question 12

Gas gangrene

Answer 12

(clostridial myonecrosis)

• caused by anaerobe Clostridium perfringens
• tissue death and swelling caused by gas in the tissues are often seen in this deadly infection

Question 13

Brain-heart infusion agar (BHI)

Answer 13

BHI medium is an enriched medium for the cultivation of fastidious microorganisms
-agar is heated immediately before use to drive off soluble oxygen in the medium —> then cooled in an ice bath–> agar solidifies–> oxygen diffusion into medium is limited–> creates a gradient from high O2 levels at the surface of BHI deep tube to low O2 levels at bottom of tube

Question 14

Growth patterns of different organisms in BHI agar based on O2 metabolism are:

Answer 14

• Obligate aerobes= growth only at the top surface of agar
• Facultative anaerobes= growth throughout the agar and on the top
• Obligate anaerobe= growth only at the bottom of the tube
• Aerotolerant anaerobes= growth below the surface of the agar but not on it
• Microaerophiles= heaviest growth in a band just below the surface of the agar where oxygen concentration is optimal

Question 15

Hydrogen peroxide (H2O2) is considered a?

Answer 15

reactive oxygen species (ROS)

-and can cause significant damage to important molecules of bacterium like DNA, RNA, and proteins

Question 16

Reactive oxygen species (ROS)

Answer 16

• hydrogen peroxide is considered this

- to detoxify ROS many bacteria produce the enzyme catalase

Question 17

Function of catalase

Answer 17

to convert H2O2 (hydrogen peroxide) into water (H2O) and O2 gas, which are harmless to the cell

    catalase 2H2O2---> 2H20 + O2

-to detoxify ROS hydrogen peroxide

Question 18

To determine if an organism produces catalase

Answer 18

• an inoculum is placed on a glass slide
• a few drops of H2O2 (hydrogen peroxide) is dispensed onto the cell
• If the organisms produces a catalase, bubbling will appear due to production of O2 gas from the breakdown of H2O2 and the organisms is considered a catalase positive