Ch. 6 Microbial Growth

Question 1

growth

Answer 1

increase in the number of cells

Question 2

physical requirements for growth

Answer 2

1) temp
2) pH
3) osmotic psi

Question 3

temperature requirements different species

Answer 3

different species have different temp ranges. each has a minimum (slow growth) and optimal temp (short range) and maximum (do not grow above it)

Question 4

psychrophiles

Answer 4

• cold loving
• optimal temp 12-13 C
• can grow below freezing
• can’t grow much above - room temp (18-20C)
• extreme environments

Question 5

psychrotrophs

Answer 5

room temp optimal. Can grow inside of fridge. tend not to grow below freezing

Question 6

mesophiles

Answer 6

• middle loving
• optimal temp approx 37 C
• can grow as cold as 10 C
• don’t survive much above 50 C

Question 7

thermophiles

Answer 7

• heat loving
• optimal temp above 60 C
• can’t grow below 40 C

Question 8

hyperthermophiles/extreme thermophiles

Answer 8

• mostly archaea
• optimal temp 90-100 C
• can’t grow below

Question 9

danger zone of temp

Answer 9

12-50 C (rapid range of growth for pathogenic organisms)

Question 10

neutrophiles optimal pH

Answer 10

6.5-7.5

many pathogens and normal microbiota

Question 11

acidophiles

Answer 11

pathogens do not like acidic enviro (hostile)

Lactobacillus

Question 12

alkalophiles

Answer 12

alkaline

Question 13

molds and yeasts pH

Answer 13

5-6

Question 14

isotonic solution

Answer 14

equal osmotic psi in and out of cell

Question 15

hypertonic solution leads to

Answer 15

plasmolysis

plasma membrane shrinks away from cell wall and cell growth is inhibited

Question 16

hypotonic solution leads to

Answer 16

nothing if intact cell wall

Question 17

halophiles

Answer 17

love salt

Question 18

obligate halophiles

Answer 18

require high salt concentrations

Question 19

facultative halophiles

Answer 19

can survive higher salt but don’t have to
Staphylococcus
(2% or even up to 15%)

Question 20

elements required for growth

Answer 20

• carbon
• nitrogen
• sulphur
• potassium
• magnesium
• calcium
• phosphorus
• iron
• trace elements
• some require organic growth factors (called fastidious)

Question 21

nitrogen sources

Answer 21

NH4+ or NO3- (inorganic ammonium or nitrogen)

N2 (gas, nitrogen fixation)

Question 22

nitrogen fixing bacteria genuses

Answer 22

Rhizobium

Bradyrhizobium

Question 23

Obligate aerobe

Answer 23

• requires oxygen; aerobic resp only
• catalase and superoxide dismutase (SOD) allows oxygen free rads to be neutralised
• Mycobacterium tuberculosis

Question 24

facultative anaerobes

Answer 24

• both aerobic and anaerobic; greater growth in presence of O2
• catalase and SOD
• E. coli and yeasts

Question 25

obligate anaerobes

Answer 25

- only anaerobic growth; growth ceases in O2 | - lacks enzymes to neutralize oxygen radicals

Question 26

aerotolerant anaerobes

Answer 26

- SOD allows harmful forms of O2 to be partially neutralized

Question 27

microaerophiles

Answer 27

- only aerobic; O2 in low concentration | - agrobacterium

Question 28

biofilms

Answer 28

a collective of one or more types of microorganisms that can grow on many different surfaces e.g. plaque on teeth

Question 29

how do bacteria communicate to each other to clump together and create biofilms?

Answer 29

quorum sensing

Question 30

how do bacteria actually clump together in biofilms?

Answer 30

Sticky glycocalyx; has channels so that nutrients etc can pass

Question 31

culture medium

Answer 31

any material prepped for growth of bacteria in a lab. Some specialized; must initially be sterile

Question 32

culture

Answer 32

microbes growing on the medium (inoculum, solid, or liquid)

Question 33

agar

Answer 33

solidifying agent; not broken down by bacteria (not nutrient source)

Question 34

chemically defined media

Answer 34

knowing how nutrients affect bacteria (T 6.2 - 6.4)

Question 35

Anaerobic culture techniques

Answer 35

contained in bottle or air-lock; reducing media eliminates oxygen. oxyplate lid on a small plate.

Question 36

CO2 incubator

Answer 36

can set CO2 %.

Question 37

capnophiles

Answer 37

need more CO2 than in normal air.

Question 38

candle jar

Answer 38

jar with candle in it. Candle + samples in a jar; CO2 produced from candle in closed jar (for shorter time amount)

Question 39

selective media

Answer 39

suppress the growth of unwanted microorganisms

Question 40

differential media

Answer 40

everything grows, but distinguishes between species

Question 41

blood agar (sheep blood) and beta hemolysis

Answer 41

RBCs destroyed by only certain microorganisms. | S. pyogenes.

Question 42

blood agar and alpha hemolysis

Answer 42

S. pneumoniae

Question 43

alpha or beta can indicate whether a sample is:

Answer 43

pathogenic. clear spots = pathogens.

Question 44

mannitol salt agar

Answer 44

7.5% Na concentration (selective for halophiles) | colour indicates pH; some ferment manitol and some do not (yellow vs red)

Question 45

enrichment medium

Answer 45

increase small numbers of bacteria to detectable levels (e.g. soil or fecal samples)

Question 46

two methods of preserving bacterial cultures

Answer 46

``` deep freezing (-80 degrees) lyophiliation (dry freeze) ```

Question 47

Four steps of binary fission (review in textbook!)

Answer 47

1) Cell elongates, need more cell wall. Penicillin inhibits this 2) Cell wall and membrane pinch inward 3) Cross wall forms with new DNA 4) May or may not separate

Question 48

mycelium formation (Review in textbook)

Answer 48

Conidiospores | Filamentous

Question 49

generation time

Answer 49

time it takes a bacterial cell to divide or population to double; different bacteria have different generation time.

Question 50

growth of bacterial cells is...

Answer 50

exponential.

Question 51

logarithmic scale

Answer 51

growth in straight line

Question 52

phases of growth

Answer 52

1) lag phase 2) log phase 3) stationary phase 4) death phase

Question 53

Lag phase

Answer 53

bacteria are very metabolically active, but you won't see a lot of activity. DNA replication and protein synthesis take place, but there is no population increase.

Question 54

Log phase

Answer 54

fastest growth - still plenty of nutrients and room for growth - healthiest cells; transfer cultures at this point (usually ~24 hrs) - some cell death, but binary fission far outnumbers it.

Question 55

stationary phase

Answer 55

equilibrium of microbial deaths and new cells; running out of space and nutrients.

Question 56

death phase

Answer 56

population decreasing at a logarithmic rate; cell death greatly outnumbers binary fission

Question 57

carrying capacity

Answer 57

how many cells an environment can support

Question 58

measurement of bacterial growth

Answer 58

measure growth in small samples, then multiply to get total number in a culture e.g. measure 1 mL of a 10 mL sample, count culture amount, multiply by ten.