Bacterial Growth l Introduction Population vs Cellular Growth

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

Bacterial Growth

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

Bacterial Growth Stationary Log Lag Death

Bacterial Growth l Calculations - Number of cells l Example: Initial Cells = Number of cells x 2 number of generations

Bacterial 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 Growth l Calculations - Number of Generations l Example: Generations = log n 2 – log n 1/log 2 Generations = log n 2 – log n 1/0. 301 where n = number of cells at a given time

Bacterial 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 Growth Calculations - Generation Time l Time for single cell to double l Example: l Generation Time Elapsed time = Number of Generations between n 1 and n 2

Bacterial Growth Calculations - Generation Time l Time for single cell to double l Example: l Generation Time = 5 hours (Log 1, 720, 320 – log 100)/. 301 = 5/((6. 23 – 2)/. 301) =. 356 hrs or 21 min

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

Bacterial Growth l Biomass – Dry weight – Turbidity – Metabolic Activity

Bacterial Growth l Dry Weight – Mass increases in proportion to growth – Filter onto pre-weighed paper – Dry under vacuum – Time consuming but usually accurate

Bacterial Growth l Metabolic Activity – Dissolved oxygen » Decrease in oxygen as cells increase – p. H » Use indicator change or p. H meter – Monitor a metabolite » Glucose use or ethanol production or carbon dioxide

Bacterial Growth l Viable Counts – Plate counts – Membrane filters

Bacterial Growth l Total Counts – Direct Microscopic Count – Most Probable Number – Electronic Counter

Bacterial Growth l Most Probable Number – 5 tubes at 10 m. L, 1 m. L and 0. 1 m. L sized inoculum – Use combinations with table to calculate the most probable number – Confidence limits set range

Bacterial Growth l 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