Lecture 4 notes Microbiology 1 (MIB151S)

MIB151S: Microbial Nutrition, including bacterial isolation methods (Microbiology 1)
Cape Peninsula University of Technology
Lecture 4 Notes

Microbiology 1
________________________________________________________________
 The common nutrient requirements
 Requirements for Carbon, Hydrogen and Oxygen
 Nutritional Types of Micro-organisms
 Sources of Carbon, Energy and Electrons
 Major Nutritional Types of Microorganisms
 Requirements for Nitrogen, Phosphorous, and Sulphur
 Growth Factors
 Uptake of Nutrients by the Cell
 Culture Media
 Different forms of media
 Isolation of Pure Cultures
 Streak Plate Technique
 The Spread Plate
 The Pour Plate
 Colony Morphology and Growth
_______________________________________________________
Microbial Nutrition, including bacterial isolation methods


 Nutrients are substances used in biosynthesis end energy production, and
are therefore required for microbial growth;
 Bacterial growth is dependent on a number of factors:
 A supply of suitable nutrients
 An energy source
 Water
 A suitable temperature
 A suitable pH
 A suitable amount of O2


4.1 The common nutrient requirements
 Over 95% of cell dry weight is made up of carbon, oxygen, hydrogen,
nitrogen, sulphur, potassium, calcium, magnesium and iron;
 The major macroelements (C, O, H, N, S) – are required by
microorganisms in relatively large amounts;
 Used for the synthesis of carbohydrates, lipids, proteins and nucleic acids

1

, MIB151S: Microbial Nutrition, including bacterial isolation methods (Microbiology 1)
Cape Peninsula University of Technology
Lecture 4 Notes

 The minor macroelements (K+, Ca+, Mg+ and Fe2+ and Fe3+);
 Functions include:
 K+ - involved in enzyme activity, including the ones involved in
protein synthesis;
 Ca+ - contributes to the heat resistance of endospores;
 Mg+ - serves as a cofactor for many enzymes, complexes with ATP,
and stabilises ribosomes and cell membranes;
 Fe2+ and Fe3+ - is a part of cytochromes and a cofactor for enzymes
and electron-carrying proteins;
 Several micronutrients or trace elements (manganese, zinc, cobalt,
molybdenum, nickel and copper) are needed by most cells;
 In nature, micronutrients are ubiquitous and probably do not usually limit
growth;
 They are part of enzymes and cofactors, and aid in the catalysis of
reactions and maintenance of protein structure;
 Certain micro-organisms have specific requirements for certain nutrients,
e.g. although most bacteria do not require large amounts of sodium, many
bacteria growing in saline lakes and oceans depend on the presence of
high concentrations of sodium ion (Na+).


4.2 Requirements for Carbon, Hydrogen and Oxygen
 Carbon is needed for the skeleton or backbone of all organic molecules;
 Organic nutrients can serve as energy sources – when they are reduced,
they can donate electrons to other molecules;
 The more reduced the organic molecules, the higher their lipid content
(lipids have a higher energy content than carbohydrates);
 CO2, as it lacks hydrogen, does not supply energy;
 Probably all organisms can fix CO 2 (reduce it and incorporate it into
organic molecules);
 Only autotrophs can use CO2 as their sole carbon source;

2