BACTERIA

It was Anton Van Leuwanhoek in 1683 who observed bacteria with the help of his self constructed compound microscope. Bacteria are found everywhere in air, water, soil, food in living organisms such as the intestines of man and animals, on dead decaying organic matter, etc.

Bacteria are single celled organisms or made up of chains or clusters of similar cells. Bacteria has no distinct nucleus. The nucleus is not bounded by a nuclear membrane, i.e. bacterial cell is prokaryotic. Chromatin material is present in the central region. Nucleolus is absent. Bacterial cell have a cell wall composed of mainly chitin. A thin layer called capsule surrounds the cell wall.

    Mitochondria and chlorophyll are absent. Reserve food is glycogen. On the basis of general shape four main types of bacteria are recognized

 They are:    1.   Coccus    
                      2.   Bacillus   
                      3.   Spirillum
                      4.   Vibrio              
   
                                 Cocci bacteria are spherical in shape and may stick together in pairs, chains and clusters. Bacilli bacteria are rod shaped. They can form into filaments of cells that look like hyphae of fungi. Bacteria may be flagellated or nonflagellated.

           Vibrio bacteria are comma shaped bacteria. Desulfovibrio desulfuricans is an example of vibrio bacteria. If this bacteria are living in water rich in iron compounds the sulphur released from them reacts with iron to from iron sulphide. Iron sulphide glitters like gold therefore this compound-iron sulphide is called “Fool’s gold”

                       Spirilla bacteria or spirillum bacteria are twisted bacteria. They look like tightly coiled springs. One example for spirilla bacteria is Triponema palladium which causes syphilis-a sexually transmitted disease.

                    According to the modes of nutrition bacteria can be divided in to four types.

                     

01. Saprophytic bacteria                                 

02. Parasitic bacteria

03. Chemosynthetic bacteria

04. Photosynthetic bacteria

                                                      

• Saprophytic bacteria live on dead organic matter of plant or animal origin. They secrete enzymes and digest the food substances. The soluble simple foods are then absorbed by the bacterial cell.

• Parasitic bacteria obtain food from the body of living hosts.

• Chemosynthetic bacteria obtain energy by oxidizing inorganic compounds like suphur nitrogen and iron compounds. 

• Photosynthetic bacteria contain chlorophyll. These enable the bacteria to produce food by photosynthesis.

Industrial Uses of Bacteria 

    01.   Retting fibers

     Fibers from hemp, jute and coconut husk are obtained by submerging in water for    some period. Then the middle lamellae of the fibers are acted upon by the bacteria growing in water, and the fibers are set free.

    02.   Curing of cheese, tobacco and tea

    03.   Production of vinegar

     Ethyi alcohol is converted into acetic acid (vinegar) by the action of bacteria such as Acetobacrer aceti.

    04.   Formation of curd

     Lactose or milk sugar of the milk is converted into lactic acid by the action of certain bacteria like Bacterium lactis aside. It is lactic acid that gives the sour taste to the curd.

 

Medicinal uses of bacteria

   01.   Antibiotics

    Antibiotic drugs like streptomycin, chloromycetin are produced frem bacteria.

   02.   Synthesis of Vitamin B

    Some bacteria synthesize vitamins. Specially vitamin B (e.g- Escherika coli)
 

Harmful bacteria

 

   01.   Spoilage of foods

Eg. Botulism is a food poisoning due to a bacteria called Clostredium botulinum in tinned or sealed foods. 

 

   02   Cause disesses

Diseases are caused by bacteria. Some examples are given below.

                                                                                                   

• Typhoid            : Bacillus typhosus
• Tetanus            : Clostridum tetani
• Tuberculosis  : Myobacterium tuberculosis
• Pneumonia    : Bacillus dysenteriae
• Cholera           : Vibrio cholera
• Diphtheria      : Corynebacterium diphtheriae