Categories
Biology

Beneficial and Harmful effects of Micro organisms

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 BacillusPseudomonas, Vibrio, Azotobacter, Coliform micro-organisms (e.g. Escherichia coliVibro choleraeSalmonella typhi), etc. Blue-green algae found in water include Nostoc,Anabaena and Oscillatoria.Protists in water include ChlamydomonasEuglena,Amoeba, etc. Algae include SpirogyraVolvox. 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 enteriditisAspergillus 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

DiseaseCausative
organism
Mode of
transmission
HostMajor symptoms
1.Common coldVirusAirborneManHigh fever,
headache running
nose.
2.Chicken poxPox virusAirborneManItchy skin rash
3.MeaslesParamyxo-virusAirborne and
close contact
ChildrenHigh fever, skin rashes,
headache, head
cold, cough, body pain.
4.PneumoniaBacteriaAirMan, birds,
pigs, cows
High fever, difficult
breathing and cough
5.TuberculosisMyco bacterium
tuberculosis
(bacterium)
Airborne,
food
Man, cowPersistent dry cough
and profuse sweating
at night.
6.MeningitisMeningo coccus
(Bacterium)
AirborneManHigh fever, headache,
vomiting and stiffness
of the neck.

Food and Water-borne Diseases

DiseaseCausative organismMode of transmissionHostMajor symptoms
1.TyphoidSalmonella typhi
(bacteria)
Contaminated
food and water
ManHigh temperature,
followed by
bloody diarrhea
2.CholeraVibro cholerae
(bacterium)
Food and waterManVomiting and
diarrhea
3.Food
poisoning
Salmonella sp.
(bacteria)
Infected meat,
Poultry, eggs, milk and
contaminated food
ManDiarrhea and
vomiting
4.Amoebic
dysentery
Entamoeba histolytica
(protozoan)
Contaminated food
and water
ManAbdominal pain,
and diarrhoea
5.Poliomyelitis
(infantile
paralysis)
Picornavirus
(virus)
Infected food and
water, direct contact
ChildrenHigh fever, headache
nausea, fits and
stiffness of limbs

Vector-borne Diseases

DiseaseCausative organismMode of transmissionHostMajor symptoms
1.MalariaPlasmodium sp.
(protozoan)
Bite of infected
female Anopheles
mosquito
ManHigh fever, shivering
and sweating
2.Sleeping sickness
(Trypanosomiasis)
Trypanosom
agambiense
(protozoan)
Tsetse fly biteMan and
domestic
animals
Fever, headache,
sluggishness,
drowsiness and
un- controllable sleep
3.Yellow feverArbovirusBite of infected
Aedes mosquito
ManHigh fever, headache,
backache followed by
low body temperature
and jaundice
4.PlagueBacteriumBite of infected
Rat flea
ManShivering fever, cough
and difficult breathing
5.River blindness
(onchocerciasis)
Onchocerca
volvolus
Bite of infected
black fly
ManSevere headache,
high fever and
gradual blindness

Diseases Spread by Contacts

DiseaseCausative organismMode of transmissionHostMajor symptoms
1.Tinea versicolorDermatophytesDirect skin
contact
ManYellow patches on
chest, neck, face
and back
2.Athlete’s footFungiDirect skin
contact
ManItching, smelly patches
between toes
3.GonorrheaNeisseria
gonorrhoea
(bacterium)
Sexual
intercourse
ManInflamed 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.SyphilisTreponema
pallidum
(bacterium)
Sexual
intercourse
ManA 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.AIDSHuman
immunodeficiency
virus (HIV)
Sexual intercourse,
blood transfusion,
infected sharp
instruments,
mother to
unborn child
ManSusceptibility to all
microbial infections,
high fever, loss of
weight, chronic
diarrhoea, skin rashes,
wasting away of
muscles.

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

  1. Mention two disease causing microbes, state the diseases caused, the host, the mode of transmission and the symptoms of the disease.
  2. How do microorganisms gain access into the body?
  3. Describe the stages involved in the growth of inoculated microorganisms (Graphical illustration is important).
  4. (a) What is a venereal disease? (b) Mention four venereal diseases (c) Outline five ways of controlling venereal diseases.
  5. Read up on Towards Better Health.

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