Brief presentation on growth curve and mathematics of growth kinetics in microorganisms.

1. Bacteriology and Virology
Seminar
Topic: Growth curve and Growth kinetics
Presented by:
Suby Mon Benny (20LS601032)
Submitted to:
Dr. Elcey C. Daniel

2. Introduction
The Study of Microbial Growth
• Growth takes place on two levels
• Cell synthesizes new cell components and increases in size
• The number of cells in the population increases
• The Basis of Population Growth: Binary Fission

4. Basic Nutrients for Growth
ATP for cellular processes
Carbon is necessary for the production of
many macromolecules (proteins, lipids, and
carbohydrates)
Oxygen for metabolism
Nitrogen for amino acid synthesis
Sulfur for vitamins, amino acids, structural
stability of proteins
Phosphorous makes ATP and membranes
Trace elements are used for metabolic
reaction in the cell and cell component
stabilization
cobalt Co
potassium K
molybdenum Mo
magnesium Mg
manganese Mn
calcium Ca
iron Fe
zinc Zn
Organic growth factors such as vitamins, amino
acids, and nucleic acids some growth factors
cannot be synthesized by own cellular processes
Water - water activity

7. The Population Growth Curve
 A population of bacteria does not maintain its potential growth rate
and double endlessly
 A population displays a predictable pattern called a growth curve.
 Batch culture/closed culture system
 Continuous culture/open culture system

8. The Rate of Population Growth
• Generation or doubling time(k): The time required for a complete fission cycle
• Each new fission cycle or generation increases the population by a factor of 2
• As long as the environment is favorable, the doubling effect continues at a
constant rate
• The length of the generation time- a measure of the growth rate of an organism
• Average generation time- 30 to 60 minutes under optimum conditions
• Can be as short as 10 to 12 minutes
• For example: E coli has a k value of 15-20 minutes in lab conditions, whereas its 12-24 hours
in intestinal tract of mammals

9. The Population Growth Curve measurement
 The methods used to observe the population growth are:
 Direct measurement
 Counting chamber
 Petroff- Hausser Counting Chamber
 Flow cytometry
 Electronic counter
 Fluorescence microscopy
 Indirect measurement
 Viable counting
 Plating technique
 Cell mass measurement

10. Stages in the Normal Growth Curve
• Data from an entire growth period typically produce a curve with a
series of phases
• Lag Phase
• Exponential Growth Phase
• Stationary Growth Phase
• Death Phase

11. Lag Phase
• Relatively “flat” period
• Newly inoculated cells require a period of adjustment, enlargement,
and synthesis
• The cells are not yet multiplying at their maximum rate
• The population of cells is so sparse that the sampling misses them
• Length of lag period varies from one population to another

12. Exponential Growth (Logarithmic or log) Phase
• When the growth curve increases geometrically
• Cells reach the maximum rate of cell division
• Will continue as long as cells have adequate nutrients and the
environment is favorable
• The number of cells growing greatly outnumber the number of cells
dying.
• The cultures in this phase are usually used in biochemical and
physiological studies.

13. Stationary Growth Phase
• The population enters a survival mode in which cells stop growing or
grow slowly (~109 cells per ml)
The rate of cell inhibition or death balances out the rate of multiplication
Depleted nutrients and oxygen
Excretion of organic acids and other biochemical pollutants into the growth
medium.
• The number of cells growing will become equal to the amount of cells
dying.
VBNC is a serious public health threat
• Endospores begin to form in this phase.

14. Death Phase
• The number of viable cells decline exponentially
• The rate of cell death reaches a constant level
• Programmed cell death
• The dying cell are “altruistic”

15. Mathematics of Growth Kinetics
Source: Prescott’s Microbiology, 10th edition

16. EFFECT OF SUSTRATE CONCENTRATION
IN BATCH CULTURE
• The specific growth rate is generally found to be a function of three parameters
1. The concentration of growth limiting substrate - [S]
2. The maximum specific growth rate - μmax
3. A substrate - specific constant - Ks
MONOD EQUATION
μ = μmax [S] / Ks + [S]
• Specific growth rate is independent of substrate concentration as long as excess
substrate is present.

17. Source: Wikipedia

18. Potential Importance of the Growth Curve
• Implications in microbial control, infection, food microbiology, and
culture technology
• Growth patterns in microorganisms can account for the stages of
infection
• Understanding the stages of cell growth is crucial for working with
cultures
• In some applications, closed batch culturing is inefficient, and instead,
must use a chemostat or continuous culture system

19. My References
• Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier
India.
• Willey, Sherwood, Woolverton; Prescott’s Microbiology; 10th ed; McGrawHill
Education,US:
• Trivedi P.C., Pandey S, and Bhadauria S. (2010). Textbook of Microbiology. Pointer
Publishers; First edition
• JoVE Science Education Database. Environmental Microbiology. Bacterial Growth
Curve Analysis and its Environmental Applications. JoVE, Cambridge, MA, (2019).
• Kim, K. S., & Anthony, B. F. (1981). Importance of bacterial growth phase in
determining minimal bactericidal concentrations of penicillin and methicillin.
Antimicrobial agents and chemotherapy, 19(6), 1075-7.