Chapter 4

Question 1

essential nutrients of microbe

Answer 1

compounds that a microbe must have but cannot make

• Supplied by environment

Question 2

macronutrients

Answer 2

nutrients needed in large quantities
• Six major elements: C, O, H, N, P, S
• Cations that serve as cofactors for specific enzymes:
Mg2+, Fe2+, K+, Ca2+

Question 3

micronutrients

Answer 3

• Co, Cu, Mn, Zn, Mo, Ni

Question 4

•Energy must be stored

Answer 4

• Chemical energy (ATP)

Question 5

membrane potential

Answer 5

when chemical energy pumps protons outside of the cell

Question 6

nitrogen gas

Answer 6

its 79% of earths atm, but most organisms can’t use gas form (N2)

Question 7

the nitrogen cycle requires

Answer 7

nitrogenfixing bacteria to convert N2 to NH4+(ammonium) using nitrogenase enzyme

Question 8

Selective permeability is achieved in three ways

Answer 8

• Substrate-specific carrier proteins (permeases) in the
membrane
• Nutrient-binding proteins that patrol periplasmic space
• Membrane-spanning protein channels (pores) that
discriminate b/w substrates

Question 9

passive diffusion

Answer 9

• uncharged molecules, like 02 and co2, cross membrane

* Follows concentration gradient

Question 10

facilitated diffusion

Answer 10

• Transporters pass material into/out of cell

* Follows concentration gradient

Question 11

coupled transport

Answer 11

Uses energy released from one molecule transported down gradient to transport a second molecule against its gradient

Question 12

symport

Answer 12

molecules move in the same direction

Question 13

antiport

Answer 13

molecules move in the opposite direction

Question 14

example of group translocation

Answer 14

• phosphotransferase system (PTS)
• Uses (PEP) to attach phosphate to sugars
• Glucose becomes glucose-6-phosphate

Question 15

Selective media

Answer 15

favor growth of one organism over another

Question 16

differential media

Answer 16

expose biochemical differences b/w species

Question 17

Example of medium that is both selective and

differential

Answer 17

• MacConkey lactose medium
-Only gram-negative bacteria grow (selective)
-Only species capable of fermenting lactose produce
pink colonies (differential)

Question 18

How do we know unculturable microbes exist?

Answer 18

• All known microorganisms have rRNA
• rRNA is highly conserved across the phylogenetic tree
• PCR/sequencing of soil and water compared to known culturable organisms shows undiscovered microbes

Question 19

growth rate

Answer 19

increase of cell numbers, exponential

• If a cell divides by binary fission, the # of cells = 2^n

Question 20

generation time

Answer 20

*FOR GROWTH IN PURE CULTURE
Nt = N0 x 2^n (NO original cell #)
• Generation time, g = t/n

Question 21

growth rate constant

Answer 21

number of generations per unit time (usually per hour)

k = n/t

Question 22

• Remember generation time g = t/n

Answer 22

• So, k = 1/g

Question 23

batch culture

Answer 23

• A liquid medium within a closed system. The simplest way to show effects of a changing environment is to culture bacteria

Question 24

Distinct stages in biofilm development

Answer 24

Initiation, Maturation, Maintenance, Dissolution
• Form thick extracellular matrix (e.g. EPS) – increase
antibiotic resistance of residents within biofilm

Question 25

spores

Answer 25

• Certain gram-positive bacteria (Clostridium, Bacillus)
can form spores
• Don’t grow and don’t need nutrients until they germinate

Question 26

heterocysts

Answer 26

Anabaena. fix nitrogen anaerobically while maintaining oxygenic photosynthesis

Question 27

gliding motility

Answer 27

Myxococcus xanthus uses this – uses pilus to travel

Question 28

fruiting body

Answer 28

Starvation starts cycle where 100,000+ cells clump to form this.

Question 29

Myxococci within the fruiting body differentiate into

Answer 29

thick walled spores and are released into surroundings (to find nutrients)

Question 30

cell cycle

Answer 30

lag log stationary death