Plot of increases in cell number vs time for cell dividing by binary fission = Growth Curve Plot of increases in cell number vs time for cell dividing by binary fission = Growth Curve

Logarithmic GrowthLogarithmic Growth

N = No2N = No2nnExponential GrowthExponential Growth

N = No2N = No2nn

n = number of generations (doublings) required for a population at aninitial cell density (No) to reach a specific higher cell density (N)

n = (log Nt-logNo )/log2 log2 = 0.301log2 = 0.301

When cell concentrations of 10When cell concentrations of 1022 reaches 10 reaches 1055 cells/Liter in 4 hrs, how many generations has passed? cells/Liter in 4 hrs, how many generations has passed?

n =1

n =2

n = (log 101055 -log 101022 ) / 0.301= (5-2)/0.301 = 9.67 generations (doublings)0.301= (5-2)/0.301 = 9.67 generations (doublings)

What was the generation time (gt) or What was the generation time (gt) or doubling timedoubling time (Dt)? (Dt)?

gt = Dt = 4 hours/ 9.67 generations (doublings)/ = 0.41 hrs ~ 25 minutes = Dt = 4 hours/ 9.67 generations (doublings)/ = 0.41 hrs ~ 25 minutes

ADD TO YOUR NOTES Doublings per day = 24 h/gt = 24/0.41 ~ 58! ADD TO YOUR NOTES Doublings per day = 24 h/gt = 24/0.41 ~ 58!

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Compare pattern of growth based upon cell number vs biomass estimates over timeCompare pattern of growth based upon cell number vs biomass estimates over time

Under LD, cell division is often phased to one time of day, with gt varying in a repeatable (predictable) pattern over time

•Here, in situ diatoms were incubated in collecction water plus one of 3 possible inorganic nitrogen sources were added.

•Do results indicate that N is limiting in the original sample? •Which is the most limiting N source?•need control expt to see growth in absence of extra nutrients

max min

max

Synchronous growth

Nt1

Nto

Another way of estimating growth rate is to calculate the rate of change in cell number or Another way of estimating growth rate is to calculate the rate of change in cell number or mass per change unit time (dN/dt), esp. to identify phased & highly dynamic growth ratesmass per change unit time (dN/dt), esp. to identify phased & highly dynamic growth rates

Where Where dN/dtdN/dt = i = is the rate of change in cell number or s the rate of change in cell number or mass per unit time&mass per unit time& == specific growth rate constant, specific growth rate constant, usually expressed in values per day (D-1)usually expressed in values per day (D-1)

dN/dt = dN/dt = NN

To solve forTo solve for for any specific time interval, the for any specific time interval, the differential differential dN/dtdN/dt must be integrated between times must be integrated between times t1t1 & & t2t2

lnNt2 - lnNt1 = (t2-t1)

Note: ln (natural exponential log)Note: ln (natural exponential log)

[lnNt2 - lnNt1]/ (t2-t1) = unitsunits (d(d

Exponential GrowthExponential Growth

dN/dt = dN/dt = NN

N = ln 2/ n, where n = number of generations

unitsunits (d(d

Continuous culture systemContinuous culture system ( (chemostat, cyclostat, turbidostatchemostat, cyclostat, turbidostat) differ from batch cultures ) differ from batch cultures in that nutrients are supplied to the cell culture at a in that nutrients are supplied to the cell culture at a constantconstant rate, and in order to maintain a rate, and in order to maintain a constant volume, an equal volume of cell culture is removed. This allows the cell population to constant volume, an equal volume of cell culture is removed. This allows the cell population to reach a “steady state” (ie. growth and cell division where the growth rate and the total reach a “steady state” (ie. growth and cell division where the growth rate and the total number of cells per milliliter of culture remains constant).number of cells per milliliter of culture remains constant).

1. If flow rate removes cells as fast as they divide, then the cell concentration in the chemostat will stay the same and its gt = time it takes to completely replace the volume of medium in the chemostat once.

2. However, cell concentrations in chemostat can rise when the actual gt is faster than the gt predicted by setting the flow rate.

3. And cell concentrations in chemostat will fall when the actual gt is predicted than the gt predicted by the set the flow rate.

Pattern of diel variation in cell division ofdiatom grown in a cyclostat (chemostat with LD cycle)

Fe concentration in growth media

4 diatom spp

What is the experimental set up to get this data using batch cultures ?What is the experimental set up to get this data using batch cultures ?

Growth rate is dependent upon many biological variables and comparison of growth rates under different conditions and between phytoplankton type show the great variability that any one variable may have on growth rate.

Temperature Regulation of microbial growth rates

(k = (k = ))

Winter SST

Different races of a Different races of a single specie of single specie of phytoplankton havve phytoplankton havve developed at each pole developed at each pole as ocean warmed and as ocean warmed and separated the specie separated the specie into isolated niches. into isolated niches.

Atlantic temperature sectionAtlantic temperature section

Falklands Greenland

Surface salinitySurface salinityNote how muchNote how much

Saltier the N. Saltier the N. Atlantic is than N. Atlantic is than N.

Pacific OceanPacific Ocean

Salinity regulation of microbial growth…not the different shapes of the different curves

• Extreme halophile…salt pondssalt ponds

• halophile… most marine phytoplankton most marine phytoplankton

• halotolerant…estuaries, coastal zone, ice estuaries, coastal zone, ice edgeedge

• Non-halophile… freshwater, soil, gut freshwater, soil, gut (enteric)(enteric)

Non-halophile

Halophile

ExtremeHalophile

Halotolerant

7. Sinking &/or Burying of POC in sediment

Fecal material

Review of the Carbon Cycle found in all types of aquatic ecosystemsReview of the Carbon Cycle found in all types of aquatic ecosystems

inorganic

1

1. Inorganic Nutrient Uptake & Limited availability controls u

2. Autotrophic Growth (formation of new organic C, N, P, S, Si etc. from external inorganic sources)

/ Plant Biomass

/Animal Biomass

/Bacterial Biomass

3. Grazing (consuming new POM, DOM ) and passing through food webs, microbial loops5

5. Uptake of DOM to support heterotrophic growth

66

6. Remineralization

DOM

44

4. Create DOM pool due to excretion sloppy feeding, death / decay

3*. Grazing (consuming recycled POM, DOM ) and passing through microbial loops