Microbial Growth #4

Question 1

1. Describe the three major steps in the process of binary fission.

Answer 1

1: cell elongation (autolysens cleave peptidoglycan in a very specific area, allowing growth)
2: Chromosome replication:
3: binary fission: one cell forms two cells

Question 2

DNA Polymerase III

DNA Polymerase I

Answer 2

DNA Polymerase III: performs standard chain building

DNA Polymerase I: removes and ‘writes’ over RNA primers

Question 3

give units and explain
dN/dt = uN
1      0
2     20
4     40
8     60

Answer 3

u = growth rate constant = 1/h
N = concentration of cells = cells/ml

uN = #of cells/(h*ml)

so if I know I have 2 cells per ml, and a growth constant of 6, then i’ll have 12 cells per ml in 1 hour

Question 4

Distinguish between microbial growth rate and the growth rate constant, and provide an equation that shows the relationship between the two.

Answer 4

dN/dt = uN
u is the growth rate constant, the higher the u, the faster it divides

dN/dt is the growth rate. It is how fast it divides, multiplied by its concentration

Question 5

Describe seven methods of determining bacterial population size, indicate what aspect of population size they measure (e.g. number, c.f.u., mass, etc.), and pick which method would be more appropriate for different purposes.

Answer 5

1, optical density (measure light that comes through)
2, dilution and plate count (counting cfu’s, viable plate counts)
3, Most probable number calculation (likely how many viable cells there are), uses dilution to extinction
4, Petroff counting chamber (25 chambers per a square millimeter) if you know height you know volume
5, .1 ml into 1cm by 1 cm square. Count cells. Figure out size of field of view.
6, filter cells with .2-.4 uL filters
7, capillary tube cell counter (flow cytometry)

Question 6

Acridine orange

Answer 6

dye’s DNA orange

Question 7

DAP1

Answer 7

binds to DNA (a-t rich regions)

blue

Question 8

fluorescence in situ hybridization (FISH)

Answer 8

Allows you to pick a sequence and fluoresce it. Uses RNA probes.

Question 9

FITC

Answer 9

Fluorescein isothiocyanate (FITC)
Stain that stains cyanish-green, often used in flow cytometry

Question 10

flourochrome

Answer 10

A type of stain, fairly non specific

Question 11

fluorescent antibody stain

Answer 11

can attach an antibody to a stain to target specific cells and fluoresce them

Question 12

Gravimetric measurements

Answer 12

1 Centrifuge cells
2 Oven dry
3 Weigh

Know mass is analogous to cell#/ cell size

Question 13

Live dead stain:

Answer 13

detects whether the membrane is intact (green stain to all cells, red stain only can enter dead cells with broken membrane)

Red dead

Question 14

SAR11

Answer 14

the taxon Pelagibacterales, that make up most of the ocean biomass. This is the name given these bacterium prior to more specific isolation

Question 15

Signature compounds

Answer 15

You can measure signature compounds as a proxi to the # of bacteria which must be there to produce that amount of substance X

Question 16

triphenyl tetrazolium chloride

Answer 16

Is a metabolic stain, it starts clear and turns red if reduced by a dehydrogenase.

Question 17

Explain why viable counts have limited usefulness in determining bacterial population sizes in environmental samples such as seawater or soils.

Answer 17

< 1% of bacterial will be culturable/viable in the lab.

Question 18

Describe how the most abundant organism on earth was identified and isolated.

Answer 18

Pelagibacter ubique, was the most abundant thing in the ocean so…
dilution to extinction.
FISH
all used to identify the little bugger