Microorganisms are very tiny living organisms that can’t be seen with the eyes except through the aid of a microscope or magnifying lens. These microorganisms are beneficial to the human health as well as dangerous also.
Microorganisms like all living things grow and multiply. The growth of microorganisms involves increase in size and in number of cells. Both nutritional and physical factors affects their growth. The nutritional factors include carbon, oxygen, hydrogen, nitrogen, and minerals. Physical factors are suitable temperature (between 25˚C to 40˚C for most microorganisms), suitable pH medium, osmotic pressure, and feeble light. Aerobes require oxygen for growth while anaerobes do not require oxygen.
PHASES OF GROWTH OF MICROORGANISMS:
Microorganisms become visible as colonies when they are left in a culture medium.
Under normal circumstances, a culture grows in four phases
1. LAG PHASE; This phase which shows no increase in the number of microbial cells.
2. EXPONENTIAL PHASE; in this phase, there is exceptional increase in number of cells with time. The highest growth occurs in this phase.
3. STATIONARY PHASE; the growth in this phase tends towards an equilibrium state or the number of viable cells is constant.
4. DECLINE PHASE; In this phase, the number of viable cells decreases exponentially with time.
WAYS OF MEASURING GROWTH OF MICROORGANISMS
1. MICROSCOPIC COUNT; Correct dilutions of the bacterial or yeast cells are prepared and the cells on the slide are counted under a microscope.
2. PLATE COUNT; This involves counting the number of viable cells that grow out in colonies from dilutions of microbial cells in a petri- dish using a colony- counter.
3. MEASUREMENT OF CELL DENSITY; In this method, a calorimeter /or spectrophotometer is used to measure cell density of a population of cells. This method is used to measure growth of microorganisms in aqueous suspensions.
4. DRY WEIGHT METHOD; Dry the cell crop from heavy culture suspension in an oven at a particular temperature for a given time and then weigh the dried cell crop. This may be employed in determining the growth of moulds.
5. MEMBRANE FILTER METHOD; The membrane filter with its trapped microorganism is placed in a favourable medium for a period of time. The microorganisms which appear in colonies on the membrane filter by their growth are counted. This method is employed in counting the microbial cells in food, water, soil and milk.
6. METABOLIC ACTIVITY; This can be used to measure the growth rate of microorganisms since the degree of metabolic activity is directly related to the size of microbial population.
BENEFICIAL EFFECT OF MICROORGANISMS
1. IN NATURE OR IN AGRICULTURE:
A. In making compost, bacteria and fungi decompose organic matter such as plant and animal.
B. Bacteria such as Rhizobium and bacillus radicicola which exists in root noodle and Azotobacter and Clostridium (in soil) fix atmospheric nitrogen into nitrates for plant use.
C. Nitrifying bacteria such as Nitrosomas and Nitrobacter convert ammonia into nitrates for plant use.
D. They are important nutrient cycling and balance in nature.
A. Microorganisms are used in the manufacture of antibiotics, enzymes, vitamins. An antibiotic, penicillin extracted from a fungus, Penicillum was discovered by Alexander Flemming.
B. Disease-causing-microorganisms produce antibodies in the bloodwhen injected into the body to help in the body defence system.
C. Some produce Vitamin B12, and Vitamin K in intestines while others help to digest cellulose.
A. Fermentation by yeast is employed in brewing of beers, other alcoholic drinks or beverages and baking of bread.
B. Microorganisms are employed in tanning of leather, making of butter and cheese by curdling of milk and curing of tobacco.
C. They are used in the production of lactic acid, vinegar and citric acid.
HARMFUL EFFECTS OF SOME MICROBES
1. Microorganisms cause food spoilage, through decay.
2. They destroy materials such as wood, paper, rubber, leather, paint work, and textile.
3. Some microbes such as Desulfovibrio specie corrode metals used in petroleum industry.
4. Some microorganisms cause diseases of plants and animals. For example, some bacteria produce toxin which are poisonous substances that causes diseases.
TYPES OF DISEASE CAUSING MICROORGANISMS
1. BACTERIA DISEASES; They are diseases caused by bacteria. Examples are tetanus, pneumonia, anthrax, gonorrhoea, and syphilis.
2. VIRAL DISEASES; They are diseases caused by viruses. Examples are small pox, influenza, yellow fever, common cold, chicken pox, measles, and meningitis.
3. PROTOZOAN DISEASES; Malaria, sleeping sickness, and itching in genital organs.
Microorganisms may be transmitted and spread by the following ways;
1. By insects and other animals.
2. Through water and food.
3. Through air
4. By direct contact with an infected person.
DISEASES CAUSED BY MICROORGANISMS
Causative agent; Vibrio cholera (V)
Mode of transmission; through contaminated food and water and by faeces of infected person.
Symptoms; frequent watery stools, vomiting, dehydration and drop in blood pressure.
Causative agent; Gonococcus (B)
Mode of transmission; Direct sexual contact
Symptoms; Pain and burning sensation during urination, white discharge from the penis, difficulty in passing out urine, if untreated may lead to infertility. Infected women have pains in their lower belly and causes menstrual problems. They may be infertile.
Control; Avoid sexual contact with an infected person, prevention with antibiotics and treatment of the sufferer.
AIDS (Acquired Immune Deficiency Syndrome)
Causative organism; Hiv Virus which Trans cedes to Aids after a long period of time.
Mode of transmission; Sexual contact, blood transfusion, use of infected syringes for injection, use of infected instruments for circumcision, and ear perforation.
Symptoms; Fever, loss of weight, various cancers, pains, illnesses, itchy skin, rashes, tuberculosis, and sunk cheeks.
Control; Having one sex partner, use of condoms, isolation of patients, use of sterilized injection, syringes, and instruments for circumcision and ear opening.
Immunity is a natural or acquired resistance provided by antibodies to a specific disease.
In natural immunity, a person suffering from a diseases produces antibodies to combat and neutralize the effect of causative organisms and their toxins while in acquired immunity, the sufferer from some of these diseases become immune as the body has available antibodies to combat the disease. Such disease include Small pox and Yellow fever.
Active artificial immunity is achieved by inoculating the body with a vaccine. The vaccine is a mild or dead pathogen injected into the body to stimulate the production of antibodies. This process is known as Vaccination.
In passive artificial immunity, a serum containing already formed antibodies is injected into the body to produce an immediate but temporary protection. This is important in combating diseases such as tetanus that have very poisonous reactions.
Immunization is the administration of a vaccine to protect an individual from a particular disease or infection.