microbial growth and nutrition Flashcards
5 phases of microbial growth curve in a closed system
- lag phase
- exponential phase
- stationary phase
- death phase
- long-term stationary phase
microbial growth curve
1. lag phase
cells dont reproduce immediately
-need enzymes and transport proteins to be made first
microbial growth curve
2. exponential phase
cells grow at their maximum rate and there are no limitations to nutrients
microbial growth curve
3. stationary phase
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
microbial growth curve
4. death phase
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
microbial growth curve
5. long-term stationary phase
dying cells release nutrients and the remaining cells feed off these nutrients
binary fission
bacterial growth, 1 parent cell divides into 2 identical daughter cells- exponential growth
generation time
time required for a population of cells to double in number
environmental factors affecting growth
- solute concentration/osmosis
- pH
- temperature (too hot = permanently denature protein)
- oxygen concentration
- solute concentration/osmosis
halophiles- like salt
oenophiles- like high osmotic pressure
compatible solutes
pH affect growth
acidophiles like ph of 0-5.5
neutrophiles ph of 5.5-8
alkalophiles ph of 8-11.5
temperature affect growth
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
oxygen concentration affect growth
-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
aerobe vs anaerobe
aerobes- can only survive in oxygen
anaerobes- no oxygen
what harmful thing doe aerobes produce when catabolizing oxygen and how do they detox
make peroxides, detox with enzymes: catalase or peroxidase or superoxide dismutase
catalase test
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)
obligate aerobes
obligate anaerobes
facultative anaerobes
aerotolerant anaerobes
microaerophiles
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)
how can you test to see what oxygen requirements are?
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
biofilms
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
culturing microorganisms:
innoculum
medium
broth
colonies
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
agar- the basis of all solid media
-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)
defined (synthetic) media vs complex media vs selective media vs differential media vs anaerobic media
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
macconkey agar- what 2 medias are used?
selective and differential
-enhance the growth of certain species that can then be distinguished from other species by variations in appearance
what are the characteristics used to describe a microorganism culture on solid
shape
margin
elevation
size
texture
appearance
pigmentation
optical property
clinical sampling
- skin, accessible membrane, wound
- blood
- cerebrospinal fluid
- lungs
- other; catheter, intubation, biopsy
pure cultures
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
streak plate
-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
measure a small vs large population size
serial dilutions for large population
–> also turbidity
membrane filtration for small population
membrane filtration for small population measurement
use filter to trap bacteria and use grid to count
serial dilutions for large population
measurement
keep diluting
turbidity for indirect and large population measurement
cloudy/turbid = more bacteria
use light source, less light gets through more bacteria
use spectrophotometer to measure
transmission is inversely proportional to population size
