microbial growth and nutrition

Question 1

5 phases of microbial growth curve in a closed system

Answer 1

1. lag phase
2. exponential phase
3. stationary phase
4. death phase
5. long-term stationary phase

Question 2

microbial growth curve
1. lag phase

Answer 2

cells dont reproduce immediately
-need enzymes and transport proteins to be made first

Question 3

microbial growth curve
2. exponential phase

Answer 3

cells grow at their maximum rate and there are no limitations to nutrients

Question 4

microbial growth curve
3. stationary phase

Answer 4

as nutrients are depleted and waste accumulate and we run out of space, the rate of reproduction decreases. eventually, # of dying cells equals # of cells being produced, and the size od the population remains constant

Question 5

microbial growth curve
4. death phase

Answer 5

if nutrients are not added and wastes are not removed, a population reaches a point at which cells die at a faster rate than they are produced

Question 6

microbial growth curve
5. long-term stationary phase

Answer 6

dying cells release nutrients and the remaining cells feed off these nutrients

Question 7

binary fission

Answer 7

bacterial growth, 1 parent cell divides into 2 identical daughter cells- exponential growth

Question 8

generation time

Answer 8

time required for a population of cells to double in number

Question 9

environmental factors affecting growth

Answer 9

1. solute concentration/osmosis
2. pH
3. temperature (too hot = permanently denature protein)
4. oxygen concentration

Question 10

1. solute concentration/osmosis

Answer 10

halophiles- like salt
oenophiles- like high osmotic pressure
compatible solutes

Question 11

pH affect growth

Answer 11

acidophiles like ph of 0-5.5

neutrophiles ph of 5.5-8

alkalophiles ph of 8-11.5

Question 12

temperature affect growth

Answer 12

can live in a range- optimum has highest growth rate but has a min and max

psychrophiles –> psycrotolerants –> mesophiles –> thermophiles –> hyperthermophiles

PPMTH

in order of like cold to hot
-10 to 110 degrees

Question 13

oxygen concentration affect growth

Answer 13

-aerobes- can only survive in oxygen
-oxygen is the final electron acceptor at the end of their catabolism
-problem: produces peroxides as a result
-solution: either the enzyme catalase or peroxidase or superoxide dismutase

Question 14

aerobe vs anaerobe

Answer 14

aerobes- can only survive in oxygen

anaerobes- no oxygen

Question 15

what harmful thing doe aerobes produce when catabolizing oxygen and how do they detox

Answer 15

make peroxides, detox with enzymes: catalase or peroxidase or superoxide dismutase

Question 16

catalase test

Answer 16

distinguish aerobic bacteria

if catalase positive- turns hydrogen peroxide into water and oxygen then will see bubbles and know its aerobic
(made peroxide not toxic)

Question 17

obligate aerobes

obligate anaerobes

facultative anaerobes

aerotolerant anaerobes

microaerophiles

Answer 17

obligate aerobes (peroxides)- have catalase and peroxides

obligate anaerobes (i.e. clostridia)- do not have catalase and peroxides

facultative anaerobes (i.e. E. coli)- aerobes that maintain life via fermentation or anaerobic respiration

aerotolerant anaerobes (i.e. lactobacilli) do not use aerobic metabolism, but they tolerate oxygen

microaerophiles (i.e. h. pylori) - requie oxygen levels of 2% to 10% (very specific)

Question 18

how can you test to see what oxygen requirements are?

Answer 18

liquid thioglycollate: allows for oxygen gradient

high O2 at top allows obligate aerobes and microaerophiles to grow

low O2 at bottoms allows strict anaerobes to grow

gradient of facultative anaerobes and aerotolerate anaerobes which can survive in both

Question 19

biofilms

Answer 19

microbial communities- have synergistic relationships among numerous microorganisms, attached to surfaces such as teeth, rocks in streams, shower curtains, implanted medical devices

70% of bacterial diseases in industrialized nations are caused by biofilms

Question 20

culturing microorganisms:

innoculum

medium

broth

colonies

Answer 20

innoculum- the sample you are trying to grow
culture= microorganisms that can grow from an innoculum

medium- collection of nutrients innoculum can grown on

broth- liquid media

colonies- cultures visible on solid media

Question 21

agar- the basis of all solid media

Answer 21

-a complex polysaccharide derived from the cell walls of red algae
-dissolved in water at 100 degrees celsius, which does not kill most nutrients
-solidifies at temperatures below 40 degrees celsius (so can add more temperature sensitive nutrients before solidifying)

Question 22

defined (synthetic) media vs complex media vs selective media vs differential media vs anaerobic media

Answer 22

defined (synthetic) media: exact chemical composition is known, difficult to prepare

complex media: often contain nutrients released from partial digestion of beef, yeast, soy, or proteins like casein from milk, often supplemented with blood, good for growing fastidious microorganisms

selective media: contain substances that either favour the growth of particular microorganisms or inhibit the growth of unwanted ones
-i..e Dif pH
-increase NaCl to ensure only halophiles grow
-methylene blue, bile salts to kill gram positive bacteria

differential media: either the presence of visible changes in the medium or differences in the appearance of colonies help us differentiate among the kinds of bacteria growing on the medium (beta-hemolysis, alpha-hemolysis, no hemolysis (gamma)
-i.e. carbohydrate utilization tubes each tube contains a single kind of simple carbohydrate was a carbon source and the dye phenol red as a pH indicator (acid fermentation with gas and colour change)

anaerobic media: stab culture puncture needle and bacteria grow on it, or anaerobic culture system (air tight with palladium and methylene blue

Question 23

macconkey agar- what 2 medias are used?

Answer 23

selective and differential

-enhance the growth of certain species that can then be distinguished from other species by variations in appearance

Question 24

what are the characteristics used to describe a microorganism culture on solid

Answer 24

shape
margin
elevation
size
texture
appearance
pigmentation
optical property

Question 25

clinical sampling

Answer 25

1. skin, accessible membrane, wound
2. blood
3. cerebrospinal fluid
4. lungs
5. other; catheter, intubation, biopsy

Question 26

pure cultures

Answer 26

pure culture; a culture in which all microbes come from a single progenitor cell or isolated colony
-the key; all cells in pure culture are genetically identical
-requires high degrees of aseptic technique and sterilized equipment

Question 27

streak plate

Answer 27

-used to isolate the organisms from a mixed population into a pure culture
-inoculum is diluted by streaking it across the surface of the agar plate
-while streaking in successive areas of the plate, the inoculum is diluted to the point where only one bacterial cell is deposited every few millimetres on the surface of the agar plate

Question 28

measure a small vs large population size

Answer 28

serial dilutions for large population
–> also turbidity

membrane filtration for small population

Question 29

membrane filtration for small population measurement

Answer 29

use filter to trap bacteria and use grid to count

Question 30

serial dilutions for large population
measurement

Answer 30

keep diluting

Question 31

turbidity for indirect and large population measurement

Answer 31

cloudy/turbid = more bacteria

use light source, less light gets through more bacteria

use spectrophotometer to measure

transmission is inversely proportional to population size