General Characteristics
- Unicellular and microscopic
- Some single cells ,others colonial
- Nuclear material not enclosed within nuclear membrane-prokaryotic
- Have cell wall but not of cellulose.
- Have few organelles which are not membrane bound
- Mitochondria absent
- Mostly heterotrophic, feeding saprotrophically or parasitically,some are autotrophic.
- Reproduction mostly asexual through binary fission
- Most of them are anaerobes but others are aerobes
- Most move by flagella
Examples include Escherichia coli, Vibrio cholerae and Clostridium tetani.
- Spherical known as Cocci.
- Rod shaped – e.g. Clostridium tetani
- Spiral shaped e.g. sprilla
- Coma shaped- Vibrios -e.g., Vibrio cholerae.
Economic importance of bacteria
Benefits to man include:
- They are used in food processing e.g., Lactobacillus used in processing of cheese, yoghurt.
- Involved in synthesis of vitamin Band K, in humans and breakdown of cellulose in herbivores.
Genetic Engineering
Bacteria are easily cultured and are being used for making antibiotics, aminoacids and enzymes e.g. amylase, and invertase e.g., Escherichia coli.
Nutrient cycling:
Saprophytes
- They are involved in decomposition of dead organic matter.
- They are useful in the nitrogen cycle.
- Nitrogen fixing and nitrifying bacteria.
- They increase soil fertility.
- Modem sewage works use bacteria in treatment of sewage.
- Cleaning oil spills in oceans and lakes.
Harmful Effects
- Bacteria cause disease:
- To humans (e.g. Cholera).
- To animals (e.g. Anthrax).
- Bacteria cause food spoilage.
- Others cause food poisoning e.g. Salmonella.
- Denitrifying bacteria reduce soil fertility e.g., Pseudomonas denitrificans.