microbial growth Flashcards
name the essential nutrients from microorganisms
C,H,O,N,S,Se,P
out of the essential nutrients which ones have simple metabolism
P,N,S
sources of C
CO2, org compounds
sources of N
NH3,NO3,N2, organic N compounds (AA,etc)
sources of H
H2O, organic compounds
sources of O
H2O,O2, org compounds
sources of P
PO4 (3-)
sources of S
H2S, SO4 (2-) ,org S compounds (cysteine), metal sulfide (FeS,CuS,ZnS, etc)
sources of K
K+ in solution, K+ salts
sources of Mg
Mg in solution, Mg salts
sources of Ca
in solution, salts
sources of Na
in solution, salts
Sources of Fe
Fe2+ , Fe3+
what are growth factors
vitamins, AA, purines, pyrimidines or other ORGANIC MOLECULES.
- needed for growth and NOT synthesized by the organism
some growth factors are the. —– or —- of another micro-organism
by products, waste
growth of the population = increase —- or —-
number of cells, biomass
what is a septum
the partition created that constricts the cell into 2 daughter cells
explain the process of septum formation
cell elongation –> septum formation –> completion of septum –> formation of walls –> cell separation
each daughter cell receives one copy of the —-, sufficient —, —- and etc
chromosome, ribosome, macromolecules
cell division requires —- and cell wall —– by —-
cell wall synthesis, destruction, autolysins
destroying and making — is the ket to cell division
peptidoglycan
- —- allows peptidoglycan to be exported across the cytoplasmic membrane.
- location?
bactoprenol, where the septum is being made.
- adds new peptidoglycan to initiate separation
at the division ring (FtsZ), —- create some — in the peptidoglycan. this allows:
autolysins, gaps, rearrangement of the peptidoglycan and synthesis of a new cell wall
wall bands
scar between old and new peptidoglycan
why do different bacterial cultures smell different
they have different metabolic pathways; produces different wastes.
- also depends on the characteristics of the species and the media
name different selective mediums mentioned in the class
1) bile salts
2) mannitol salt
bile salts —- gram + , —– for gram - and enteric pathogens
inhibit, permissive
bile salts is toxic for a lot of microorganisms but not for —–
enteric pathogens. like the ones in the intestine
lactose fermenters have a — color. lactose non fermenters are — . this color change is indicated by a —
pink, colourless, pH indicator
mannitol salt has a high —- concentration. —– most gram negative and many gram positive
NaCl, inhibits
mannitol salt is used for isolation and detection of —-. how does this work?
staphylococcus, some are mannitol negative (cannot ferment mannitol) and turn the media pink, but some are mannitol positive and produce acids that turn the media yellow
staphylococcus, mannitol + –>
staphylococcus, mannitol negative —>
staphylococcus aureus
staphylococcus epidermis
function of staphylococcus aureus
wound infection, has a high antibiotic resistance
what is a viable count
- measured to test microbial presence
- needs a permissive growth medium
- results are reliable when there are between 30 - 300 colonies
name the methods of viable count
1) spread plate method
2) pour plate method
to get a viable count of culture with ing populations, —- are done
serial dilutions
serial dilution counts ——-
the number of cells that are able to grow
- dead cells cannot be counted
with —– you can also count dead cells
microscopic method ** know how to calculate them
—– an be used to differential between living and non living cells
viability staining
advantages and disadvantages of microscopic method
adv: fast non need to wait until the bacteria has grown
disadvantages: small cells can be missed, motile cells are hard to count
flow cytometry is better at counting — cells. like:
big, protozoan, yeast, mammalian cells, etc
how does flow cytometry work
1) aligns all cells behind each other
2) the cells go through a detection device which is a laser
3) they pass the laser
4) the light transmitted is detected by a machine
- specifies which ones are dead or alive if you use the culture of microscopic counts that are already stained
turbidimetric method
measures the contribution of alive and dad cells to turbidity
- high optical density = high turbidity
turbidimetric method is affected by:
1) clumping: form large particles –> error –> higher OD
2) attachment to surfaces –> lower OD
how is the turbidimetric method done
measured using a spectrometer, by measuring the amount of light that goes through
- technically measures the OD: log I0/I
The relationship between the number of cells and OD depends on:
the type of the cell: size, shape, composition, cells inclusion, mutations, etc
generation time
the time needed for the population to double
- depends on the growth medium and conditions
when the conditions are right, microorganisms can grow —–
exponentially , the population forms at a constant rate
equation
N = N02^n –> number of cells
calculating generation time
g = t/n
know the growth cycle
in the notes
most natural envs are —–, they have:
open systems
1) constant supply of nutrients and diffusion of waste
2) predations
3) competition with other microorganisms
4) changing env conditions
chemostats
notes
factors affecting growth
1) temp
2) pH
3) osmolarity
4) oxygen
5) pressure
6) radiation
extremophiles
microorganism that grow preferentially under extreme conditions
membrane gelling
transport processes so low that growth cannot occur
what happens above the optimum growth rate
thermolysis
membrane gelling occurs at:
minimum temp *doesn’t kill them
the temp range for most microorganism is typically —-
25- 40 degrees around the optimal temp
psychrotolerant
can grow at zero degrees but have a optimal range of 25-40 degrees
psychrophile
notes
mesophile
notes
thermophile
notes
hyperthermophile
notes
barophilic
grow best at high pressure
