Beneficial and Harmful effects of Micro organisms Biology

Beneficial Effects of Micro-organisms in Nature

(i) Bacteria in the large intestine of man synthesize the vitamin K that is needed.

(ii) Yeasts are used in baking and preparation of alcoholic drinks. Yeasts are an important source of vitamin B.

(iii) Some bacteria are used in curdling of milk, brewing of wine and in butter and cheese making.

(iv) It is used in the production of antibiotics e.g. penicillin from the mould called penicillium.

(v) Saprophytic micro-organisms decompose sewage into harmless inorganic compounds.

(vi) Most decomposers are micro-organisms and they help to maintain soil fertility.

(vii) Some bacteria living in the rumen of ruminants like sheep, goat, cattle help to digest cellulose in their food (grasses/vegetation).

(viii) Micro-organisms help in maintaining some cycles in nature e.g. the nitrogen cycle and carbon cycle. They also help in recycling phosphates and sulphate.

EVALUATION (POST YOUR ANSWERS IN THE BOX BELOW FOR DISCUSSION)

Name two beneficial microorganisms and state their benefits to man.

Harmful Effects of Micro-organisms

(i) Most diseases in animals and plants are caused by micro-organisms especially bacteria, viruses and protozoans.

(ii) Huge amounts of food are spoiled annually by saprophytic fungi and bacteria.

(iii) They also cause deterioration/damage to materials such as paper, wood, cotton, leather, etc.

(iv) Micro-organisms can also cause the death of plants and animals.

Disease-causing Micro-Organisms

Micro-organisms are spread through the following:

(i) Air: Dust and water droplets in our air contain micro-organisms such as polio virus, measles virus, pox virus, common cold virus, Pneumococci

(a bacteria), Pencillium (a fungus), etc.

(ii) Water: Bacteria found in water include Bacillus, Pseudomonas, Vibrio, Azotobacter, Coliform micro-organisms (e.g. Escherichia coli, Vibro cholerae, Salmonella typhi), etc. Blue-green algae found in water include Nostoc,Anabaena and Oscillatoria.Protists in water include Chlamydomonas, Euglena,Amoeba, etc. Algae include Spirogyra, Volvox. Fungi include moulds and mildews.

(iii) Food: Most micro-organisms in food get in through faeces, dirty utensils and equipment, unhygienic habits and vectors like flies and cockroaches. Examples are Shigella sp, Salmonella enteriditis, Aspergillus flavus, etc.

(iv) Animal vectors or carriers.

(v) Personal or direct skin contact with a sufferer.

Disease-causing micro-organisms can enter the body through body openings like the mouth, nose or reproductive opening, through wounds, through bites of other animals and through blood transfusions.

Some important diseases, their causative micro-organisms, mode of transmission, host and symptoms are outlined in the following tables.

Air-borne Diseases



	Disease	Causative organism	Mode of transmission	Host	Major symptoms
1.	Common cold	Virus	Airborne	Man	High fever, headache running nose.
2.	Chicken pox	Pox virus	Airborne	Man	Itchy skin rash
3.	Measles	Paramyxo-virus	Airborne and close contact	Children	High fever, skin rashes, headache, head cold, cough, body pain.
4.	Pneumonia	Bacteria	Air	Man, birds, pigs, cows	High fever, difficult breathing and cough
5.	Tuberculosis	Myco bacterium tuberculosis (bacterium)	Airborne, food	Man, cow	Persistent dry cough and profuse sweating at night.
6.	Meningitis	Meningo coccus (Bacterium)	Airborne	Man	High fever, headache, vomiting and stiffness of the neck.

Food and Water-borne Diseases



	Disease	Causative organism	Mode of transmission	Host	Major symptoms
1.	Typhoid	Salmonella typhi (bacteria)	Contaminated food and water	Man	High temperature, followed by bloody diarrhea
2.	Cholera	Vibro cholerae (bacterium)	Food and water	Man	Vomiting and diarrhea
3.	Food poisoning	Salmonella sp. (bacteria)	Infected meat, Poultry, eggs, milk and contaminated food	Man	Diarrhea and vomiting
4.	Amoebic dysentery	Entamoeba histolytica (protozoan)	Contaminated food and water	Man	Abdominal pain, and diarrhoea
5.	Poliomyelitis (infantile paralysis)	Picornavirus (virus)	Infected food and water, direct contact	Children	High fever, headache nausea, fits and stiffness of limbs

Vector-borne Diseases


	Disease	Causative organism	Mode of transmission	Host	Major symptoms
1.	Malaria	Plasmodium sp. (protozoan)	Bite of infected female Anopheles mosquito	Man	High fever, shivering and sweating
2.	Sleeping sickness (Trypanosomiasis)	Trypanosom agambiense (protozoan)	Tsetse fly bite	Man and domestic animals	Fever, headache, sluggishness, drowsiness and un- controllable sleep
3.	Yellow fever	Arbovirus	Bite of infected Aedes mosquito	Man	High fever, headache, backache followed by low body temperature and jaundice
4.	Plague	Bacterium	Bite of infected Rat flea	Man	Shivering fever, cough and difficult breathing
5.	River blindness (onchocerciasis)	Onchocerca volvolus	Bite of infected black fly	Man	Severe headache, high fever and gradual blindness

Diseases Spread by Contacts


	Disease	Causative organism	Mode of transmission	Host	Major symptoms
1.	Tinea versicolor	Dermatophytes	Direct skin contact	Man	Yellow patches on chest, neck, face and back
2.	Athlete’s foot	Fungi	Direct skin contact	Man	Itching, smelly patches between toes
3.	Gonorrhea	Neisseria gonorrhoea (bacterium)	Sexual intercourse	Man	Inflamed urethra burning sensation during urination and thick yellowish discharge in male. In females there may be pain during urination, redness around the urinary opening and vaginal discharge.
4.	Syphilis	Treponema pallidum (bacterium)	Sexual intercourse	Man	A small painless sore or chancre on the penis or vulva. Mild fever, skin rashes, mouth ulcers and aches in lymph node regions. It may lead to abortion, attack the brain and cause blindness and insanity
5.	AIDS	Human immunodeficiency virus (HIV)	Sexual intercourse, blood transfusion, infected sharp instruments, mother to unborn child	Man	Susceptibility to all microbial infections, high fever, loss of weight, chronic diarrhoea, skin rashes, wasting away of muscles.