Characteristics of Bacteria
1. Some are motile by means of one or more flagella.
2. Some have a slime layer around them that helps to prevent them from drying out and also increases their ability to cause disease.
3. Some produce an endospore in order to survive adverse conditions. An endospore is formed when a thick protective coat surrounds the nuclear material. Endospores are resistant to high temperature and desiccation.
4. Bacteria react in two different ways to gram stain. Gram positive bacteria absorb a blue stain. Gram negative bacteria absorb a red stain.
5. Bacteria have short hair-like structures called pilli which allow them to stick to surfaces.
6. Bacteria have small rings of genetic material called plasmids which are transferred from a door to a recipient during a type of sexual reproduction called conjugation.
7. Bacteria have several ways of getting nutrients
a. Saprophytic bacteria breakdown dead organic matter.
b. Parasitic bacteria utilize living cells as a source of food.
c. Autotrophic bacteria utilize a source of energy to make their own food.
Cyanobacteria are photosynthetic autotrophs that use light as a source of energy.
Chemosynthetic bacteria use inorganic compounds as a source of energy to synthesize their food.
8. Bacterial cells have three definite shapes:
a. bacilli – rod shaped
b. cocci – spherical shaped
c. spirilli – spiral shaped
9. Bacterial cells may occur as:
a. single cells
b. two cells joined together
c. clusters of cells
d. chains of cells
10. Bacteria reproduce asexually by binary fission and sexually by conjugation. Conjugation involves the transfer of a plasmid from a donor organism to a recipient organism.
Types of Bacteria and their mode of Nutrition
1. Obligate aerobes – these bacteria must have oxygen to survive.
2. Obligate anerobes – these bacteria can only live in the absence of oxygen.
3. Facultative anaerobes – these bacteria can live in the presence or absence of oxygen.
Ways that Bacteria are Helpful to People
1. Production of foods and useful substances such as yogurt, sauerkraut, vinegar, cheese.
2. Help to prevent invasion of disease causing bacteria in the intestines.
3. Produce some vitamins in our intestines.
4. Decomposition of dead organic matter.
5. Genetic engineering experiments. Bacteria can be produced to carry out specific functions. Production of interferon, insulin, oil breakdown.
6. Nitrogen fixing bacteria can convert nitrogen gas into a form of nitrogen that plants can use to make protein.
Ways that Bacteria are Harmful
1. Cause tooth decay, diseases and infections.
2. Cause food infections and spoilage.
3. Cause food poisoning – botulism.
4. Cause disease in plants and animals people use for food.
5. Cause decay of organic matter – wood rot in houses.