Bacterial Growth l Introduction –Population vs. Cellular Growth –Exponential vs. Arithmetic...

Post on 01-Jan-2016

222 views 0 download

Transcript of Bacterial Growth l Introduction –Population vs. Cellular Growth –Exponential vs. Arithmetic...

Bacterial GrowthBacterial Growth

Introduction– Population vs. Cellular Growth– Exponential vs. Arithmetic Growth– Bacterial Growth - Binary Fission

Bacterial GrowthBacterial Growth

Gen # Exp. Arith. # Log10 #0 20 1 05 25 32 1.51

10 210 1024 3.0115 215 32768 4.5220 220 1,048,576 6.0225 225 33,554,432 7.53

Bacterial GrowthBacterial Growth

Bacterial Growth Curve– Lag Phase– Log Phase– Stationary Phase– Death Phase

Bacterial GrowthBacterial Growth

Lag

Log

Stationary

Death

Bacterial GrowthBacterial Growth

Calculations - Number of cells

Example:

InitialCells = Number x 2 number of

generations

of cells

Bacterial GrowthBacterial Growth

Sample calculation:

How many cells would be in a culture if the starting number were 100,000 and the culture was allowed to divide 5 times?

Bacterial GrowthBacterial Growth

Calculations - Number of Generations

Example:

Generations = log n2 – log n1/log 2Generations = log n2 – log n1/0.301where n = number of cells at a given time

Bacterial GrowthBacterial Growth

Sample calculation:

How many generations have elapsed if the cell count in a culture went from 3 x 108 to 8 x 1010 in 1.5 hours?

Bacterial GrowthBacterial Growth

Calculations - Generation Time Time for single cell to double Example:

Generation Time

=Elapsed time

Number of Generations

between n1 and n2

Bacterial GrowthBacterial Growth Calculations - Generation Time Time for single cell to double Example:

Generation Time

=5 hours

(Log 1,720,320 – log 100)/.301

=5/((6.23 – 2)/.301)

= .356 hrs or 21 min

Bacterial GrowthBacterial Growth

Measurement of Growth– Biomass– Viable Counts– Total Counts– Most Probable Number (MPN)

Bacterial GrowthBacterial Growth

Biomass– Dry weight– Turbidity– Metabolic Activity

Bacterial GrowthBacterial Growth

Dry Weight– Mass increases in proportion to

growth– Filter onto pre-weighed paper – Dry under vacuum – Time consuming but usually accurate

Bacterial GrowthBacterial Growth

Metabolic Activity– Dissolved oxygen

»Decrease in oxygen as cells increase

– pH»Use indicator change or pH meter

– Monitor a metabolite»Glucose use or ethanol production or

carbon dioxide

Bacterial GrowthBacterial Growth

Viable Counts– Plate counts– Membrane filters

Bacterial GrowthBacterial Growth

Total Counts– Direct Microscopic Count– Most Probable Number– Electronic Counter

Bacterial GrowthBacterial Growth

Most Probable Number– 5 tubes at 10 mL, 1 mL and 0.1 mL

sized inoculum– Use combinations with table to

calculate the most probable number– Confidence limits set range

Bacterial GrowthBacterial Growth

Electronic counter– Cells move past light source in very

narrow tube– Each cell passing is counted– Counts both live and dead cells so

must be used before culture gets to stationary phase