chapter 4: Bacterial Culture, Growth, & Development

Question 1

what are facilitated diffusion? Example

Answer 1

Facilitated diffusion uses the concentration gradient of a compound to move it across the membrane from a compartment of higher concentration to a compartment of lower concentration (energy is not used).

• can’t move a molecule against its gradient
  example: aquaporin family that transport water and small polar molecules such as glycerol.

Question 2

what are coupled transport?

Answer 2

Coupled transport systems are those in which energy is released by a ion moving down its gradient and energy is used to move ion/solute up its gradient.
Two types:
symport (same direction)
antiport (opp. direction)

Question 3

what are ABC transporters?

Answer 3

largest family of energy-driven transport systems, found in all three domains.
Two main types:
uptake ABC-critical for transporting nutrients
efflux ABC- generally used as multidrug efflux pumps
- used to transport arabinose & galactose
Note: Gram-Neg. bacteria have substrate biniding proteins that are in periplasmic space b/w membranes.

Question 4

what is group translocation?

Answer 4

a process that uses energy to chemically alter the substrate during its transport, (ex. Adding phosphate)
Ex: PTS system present in all bacteria.

Question 5

what nutrients do microbe need to grow?

Answer 5

essential nutrients -(cannot make) nutrients have to be imported from immediate environment.: Macronutrients- carbon, nitrogen, phosphorous, hydrogen…etc
micronutrients-copper, manganese, nickel, zinc,….

Question 6

why is it important to grow bacteria in pure culture?

Answer 6

so that it is assured that there is only one type of organism present.

Question 7

why use a selective medium? a differential medium?

Answer 7

selective- favors the growth of one organism over another.
differential- exposes biochemical diffs. b/w two species that grow equally well.

MacConkey Medium- both selective and differential.

Question 8

what are growth factors?

Answer 8

specific nutrients not required by other species.

Question 9

what is binary fission

Answer 9

where one parent cell splits into two equal daughter cells.

Question 10

describe the important features of biofilms

Answer 10

Bacterial biofilms form when nutrients are plentiful
The formation of biofilms can be cued by different environmental signals in different species
Chemical signals enable bacteria to communicate (quorum sensing) and in some cases to form biofilms.

Question 11

Heterophy

Answer 11

Rely on other’s to form organic compounds which can be used as carbon sources. Can be divided into 2 classes bases on whether light is involved.

Question 12

Autrotrophs

Answer 12

Assimilate CO2 as a carbon source, reducing it to generate complex cell constituents.

Question 13

Photoautrophs

Answer 13

Use light energy to fix CO2 into biomass

Question 14

Chemolithoautotrophs

Answer 14

Fix CO2 using chemical reactions without light , inorganic molecules ( iron, sulfur, nitrogen)

Question 15

Photoheterotroph

Answer 15

Obtain energy from the catabolism of organic compounds and through light absorption

Question 16

Chemoheterotroph

Answer 16

Obtain energy and carbon for biomass solely from organic compounds.

Question 17

Nitrogen cycle

Answer 17

Essential component of proteins, n.a., &other cellular constitutents.

Question 18

How do bacteria get nitrogen?

Answer 18

Nitrogen is obtain from the atmosphere by various groups of organisms ( nitrogen fixers, nitrifiers,denitrifiers) that collaborate to recycle ammonium ions & nitrate ions into N2 gas.

Question 19

selective permeability is achieved in 3 ways:

Answer 19

• substrate specific carrier proteins (permeases) in the membrane
• nutrient binding proteins that patrol periplamic space
• membrane spanning protein channels that discriminate b/w substrates

Question 20

Siderophores

Answer 20

Specialized molecules that are secreted to bind ferric iron. Can be use for microbial growth

Question 21

Coloring forming units

Answer 21

Viable cells that can be used to produce individual colonies.

Question 22

Complex media

Answer 22

Nutrient rich but poorly defined

Question 23

Minimal defined media

Answer 23

Contains only those nutrients that are essential for growth of a given microbe.

Question 24

Enriched media

Answer 24

Complex media to which specific blood components are added

Question 25

Selective media

Answer 25

Favor growth of one organism over another

Question 26

Differential media

Answer 26

Exploit differences between two species that grow equally well

Question 27

Techniques for counting bacteria

Answer 27

• direct counting of living and dead cells
  
  • petrochemical hasusser counting chamber
  • can’t determine live vs dead
• living cells maybe distinguished by fluorescence microscopy using dyes
  
  • red cells=dead
  • green cells= alive
• counting w/o microscopy
  
  • enables us to use cell size and the level of fluorescence to ID & count different cell populations.
• indirectly counted via biochemical assay of cell mass, protein content, or metabolic rate.
  
  • measures optical density

Question 28

Stages in growth of bacteria culture

Answer 28

1. Early Lag phase =time to detect environment, express genes, synthesize components needed to grow rapidly
2. Late Log phase ( logarithmic rate of growth) = longer period of growth but at faster rate
3. Stationary phase= cells stop rising due to lack of nutrients or waste build up. Rate of cellular division equals rate of cellular death.
4. Death phase= cell dies at a logarithmic rate.
   - negative exponential function.