Microbial Physiology Flashcards
GROWTH
GROWTH in bacteriology is defined as a steady increase in all of the chemical components of the cell
Increase in chemical constituents of the cell leading to BIOMASS increase
BIOMASS increase is accompanied with increase in the SIZE of a cell though not often visible
Maximally enlarged cell subsequently undergoes cell division
Evidence of growth in bacteria is CELL DIVISION
What is binary fission?
BINARY FISSION is a process that involves involution of the bacterial cell membrane and the nascent cell wall near the site of a septal mesosome thus forming a septum.
The septum subsequently separates the cells into two daughter cells of nearly equal size such that each daughter cell contains about half the complements of structures, macromolecules, enzymes of the mother cell
GENERATION TIME
GENERATION TIME
The time required for a cell to divide (and its population to double)
It includes the period of cell growth and division Growth [Biomass increase] and DNA Replication are simultaneous and interdependent aka- Doubling time
Factors affecting cell division
- Genetic nature of bacteria
- Culture medium
- Physical & Chemical agents
Antibiotics
Dyes
Detergents
Disinfectants
Anti-metabolites
UV irradiation
Extremes of temperature
Balanced Growth
Balanced Growth: one in which the rate of increment of all the chemical constituents of all cells in a population is constant
At optimal environment, defined as:
Change in no of cell per unit time
Change in biomass per unit time
It is an indication of the orderliness of increase
Characteristic of bacteria
Function of the culture medium, physical & chemical growth conditions
Macronutrients
Microorganisms require about ten elements in large quantities,
they are used to construct carbohydrates, lipids, proteins, and nucleic acids
≥95% of cell dry weight is made up of these major elements: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium and iron.
The first six ( C, H, O, N, P and S) are components of carbohydrates, lipids, proteins and nucleic acids
Trace Elements
Microbes require very small amounts of other mineral elements,
Examples: iron, copper, molybdenum, and zinc;
Most are essential for activity of certain enzymes, usually as cofactors.
Growth Factors
These are intact nutrients (not monosaccharide or inorganic elements like nitrogen) required for growth
They include amino acids, purines and pyrimidines, vitamins
Amino acids are needed for protein synthesis,
Purines and pyrimidines for nucleic acid synthesis.
Vitamins are small organic molecules that usually make up all or part of enzyme cofactors, and only very small amounts are required for growth.
Nutritional types of microorganisms
Significance of nutritional requirements
Culture media formulation
Growth in the laboratory
Advantages of laboratory culture
Identification
Sensitivity testing
Understanding pathogenesis
Effects of O2 concentration
pH
Alkalophiles
Neutrophiles
Acidophiles
Components of peptidoglycan cell wall
