Bacteria, like all living organisms, require a variety of nutrients to grow and reproduce.
These Nutritional Requirements of Bacteria can be categorized into macronutrients and micronutrients.
Macronutrients:
A) Carbon:
Fundamental for cellular structure and energy. Sources include carbohydrates, lipids, proteins, and carbon dioxide.
B) Nitrogen:
Essential for amino acids, nucleotides, and other cellular constituents. Sources include ammonia, nitrate, nitrogen gas (for nitrogen-fixing bacteria), and organic nitrogen compounds.
C) Phosphorus:
Required for nucleic acids, phospholipids, ATP. Common source is phosphate.
D) Sulfur:
Important for amino acids (cysteine and methionine) and coenzymes. Sources include sulfate and sulfur-containing amino acids.
E) Potassium, Magnesium, Calcium, and Iron:
Serve various roles in enzyme activation, cellular structure, and electron transport.
Micronutrients
Potassium (K): Enzyme activation and cellular functions.
Magnesium (Mg): Stabilizes ribosomes, membranes, and nucleic acids; involved in enzyme reactions.
Calcium (Ca): Important for cell wall stability and spore formation.
Iron (Fe): Essential for electron transport proteins and enzymes.
Growth Factors
Vitamins: Often function as coenzymes in metabolic pathways.
Amino Acids: Required for protein synthesis.
Purines and Pyrimidines: Needed for nucleic acid synthesis.
Classification of Bacteria by Energy Sources
1) Phototrophs:
Energy Source: Light
Example: Cyanobacteria (photosynthetic bacteria that use light energy to produce organic compounds).
2) Chemotrophs:
Energy Source: Chemical compounds
Subtypes:
A) Chemoautotrophs (Lithotrophs):
Energy Source: Inorganic chemicals (e.g., hydrogen sulfide, ammonia)
Example: Nitrosomonas (oxidizes ammonia to nitrite)
B) Chemoheterotrophs (Organotrophs):
Energy Source: Organic compounds
Example: Escherichia coli (uses glucose and other organic molecules for energy).
3) Autotrophs:
Carbon Source: Carbon dioxide
Example: Nitrifying bacteria (convert ammonia into nitrates, using carbon dioxide for their carbon source).
4) Heterotrophs:
Carbon Source: Organic compounds
Example: Lactobacillus (uses organic molecules like lactose as both carbon and energy sources).