The Bio Brief

Not all microorganisms are useful. Some microorganisms are harmful and cause diseases in humans, animals, and plants.
These disease-causing microorganisms are called pathogens.

Microorganisms

      |

      |—— Useful

      |—— Harmful (Pathogens)

They can also:

• Spoil food
• Damage clothes and leather

Disease-Causing Microorganisms in Humans

How Do Pathogens Enter Our Body?

Pathogens enter our body through:

• Air we breathe
• Water we drink
• Food we eat
• Direct contact with infected persons
• Animals or insects (carriers)

Pathogens

    ↓

Air / Water / Food / Contact

    ↓

Human body

    ↓

Disease

Communicable Diseases

Diseases that spread from one person to another are called communicable diseases.

Examples:

• Cholera
• Common cold
• Chicken pox
• Tuberculosis (TB)

Spread of Common Cold

• When an infected person sneezes
• Tiny droplets carrying viruses spread in air
• Healthy person breathes them in and gets infected

Sneezing

   ↓

Virus in air

   ↓

Healthy person breathes

   ↓

Infection

Prevention of Communicable Diseases

• Cover nose and mouth while sneezing
• Keep distance from infected persons
• Wash hands regularly
• Keep food covered

Carriers of Diseases

Some animals and insects carry disease-causing microbes. These are called carriers.

Housefly

• Sits on garbage and animal waste
• Carries pathogens on its body
• Transfers them to uncovered food

Prevention:

• Keep food covered
• Maintain cleanliness

Mosquitoes

Mosquito	Disease Spread
Female Anopheles	Malaria
Female Aedes	Dengue

• Mosquitoes breed in standing water

Prevention:

• Do not allow water to collect in coolers, tyres, pots
• Keep surroundings clean and dry

Disease-Causing Microorganisms in Animals

Some microorganisms also cause diseases in animals.

Examples:

• Anthrax
  • Caused by bacterium Bacillus anthracis
  • Affects humans and cattle
  • Discovered by Robert Koch (1876)
• Foot and Mouth Disease
  • Caused by a virus
  • Affects cattle

Table: Animal Diseases

Disease	Causative Agent	Mode of Transmission	Preventive Measures
Anthrax	Bacteria (Bacillus anthracis)	Contact with infected animals	Vaccination, proper disposal of dead animals
Foot and Mouth Disease	Virus	Direct contact	Vaccination, isolation of infected animals

Disease-Causing Microorganisms in Plants

Microorganisms also cause diseases in plants like:

• Wheat
• Rice
• Potato
• Sugarcane
• Apple
• Orange

These diseases:

• Reduce crop yield
• Damage plants

They can be controlled using chemicals (pesticides) that kill microbes.

Table: Plant Diseases

Disease	Causative Agent	Mode of Transmission	Preventive Measures
Citrus canker	Bacteria	Air, water	Spraying antibiotics, removing infected plants
Rust of wheat	Fungus	Air	Use resistant varieties, fungicides
Yellow vein mosaic of bhindi	Virus	Insects	Control insects, remove infected plants

Food Poisoning

Food can become harmful when microorganisms grow on it.

What is Food Poisoning?

• Caused by eating food spoiled by microorganisms
• Microbes produce toxic substances
• Can cause vomiting, stomach pain, diarrhoea
• May be serious or even fatal

Spoiled food

     ↓

Growth of microbes

     ↓

Toxins produced

     ↓

Food poisoning

Prevention of Food Poisoning

• Eat fresh food
• Keep food covered
• Store food properly
• Avoid stale and uncovered food

Harmful microorganisms:

• Cause diseases in humans, animals, and plants
• Spread through air, water, food, and carriers
• Spoil food and other materials

By maintaining cleanliness, proper food habits, and preventive measures, we can protect ourselves from harmful microorganisms.