Bacteria are procaryotic unicellular organisms which are found in everywhere.

�Small group of bacteria are harmful but generally bacteria are benefit (useful).

�Useful bacteria are used in the production of yoghurt and cheese.

 �Some bacteria cause diseases.    This type of bacteria is called phatogenic bacteria.

�Phatogenic bacteria cause disease such as tuberculosis, cholera, diptheria, pneumonia, typhoid and teeth decay.

 �Bacteria have cell membrane, cytoplasm and hereditary material (DNA).

�They have also cell wall.

�Ribosomes are found in bacteria to produce protein.

 Some bacteria have mesosome

�Aerobic respiration takes place in mesosome of bacteria.

�Energy is produced at the end of the aerobic respiratoin.

Some bacteria may contain free chlorophyll in its structure..

�Chlorophyll makes food by means of sunlight. This process is called photosynthesis.

�Most bacteria also have flagella to provide motion.

 Types of bacteria according to their shape; 

a) Bacillus          b)Coccus     c)Vibrio      d) Spirillia

Types of bacteria according to their nutrition

�Hetetrophs

�Autotrophs

1. Autotrophic Bacteria: Autotrophic bacteria can synthesize their own food.

If bacteria use sunlight as an energy source, they are known as phototrophic bacteria.

However some bacteria obtain their energy from NH₃ ad H₂O. This type of bacteria are called chemotrophs.

2. Hetetrophic Bacteria:                         Some bacteria obtain their foodstuffs from other organisms.These types of bacteria are called hetetrophic bacteria. 

Sabrobes (Saprophytes) are  hetetrophs which live on dead organisms.

�They decompose dead organisms.

�They have an important role in the recycling of material such as Nitrogen.

�Some hetotrophic bacteria are parasitic.

Types of bacteria according to their oxygen dependency;

 

�Anaerobic bacteria

�Aerobic bacteria

�Aerobic bacteria are require O2 to obtain energy from food.

�Anaerobic bacteria don�t need oxygen for production of energy.

Types of bacteria according to the gram staining;

�Gram (+):                                               A group of bacteria which paints with gram stain.

�Gram (-):                                                           A group of bacteria which doesn't paint with gram stain.

Types of bacteria according to their flagella;

�Flagellate:A group of bacteria that have flagella.

�Non-flagellate: A group of bacteria that don�t have flagella.

�Bacteria reproduce both sexually and asexually.

�They divide into 2 parts to form new offsprings by binary fission.

�They reproduce sexually by Conjugation.