Micro organisms 8th basic level

The term “micro-organism” literally means a microscopic organism. They are too small to be seen without a microscope, and they are found everywhere, with many being beneficial or harmless.

Viruses are significantly smaller than bacteria, fungi, and protozoa. They are considered the smallest infectious agents, often ranging from 20 to 300 nanometers in size.

Blue-green algae, also known as cyanobacteria, are capable of nitrogen fixation. They convert atmospheric nitrogen into a form that plants can use for growth.

In this context, infection refers to the successful transmission and establishment of a pathogen from an infected individual to a healthy one, leading to the spread of the disease.

*Lactobacillus* bacteria are used to ferment milk. They convert lactose (milk sugar) into lactic acid, which causes the milk to thicken and develop the characteristic sour taste of yogurt.

Ringworm is caused by a group of fungi called dermatophytes. It is a skin infection, not caused by a worm. Typhoid, malaria, and cholera are bacterial or protozoan diseases.

Houseflies are mechanical carriers. They feed on contaminated waste and then land on food, transferring disease-causing pathogens like those for typhoid and cholera from their feet and mouthparts.

The bacterium responsible for cholera is *Vibrio cholerae*. It is distinguished by its characteristic curved, comma-like shape.

Viruses are considered a link because they exhibit characteristics of both. They are non-living when outside a host (inactive, crystalline structure) but become living when they enter a host cell (reproducing and carrying out metabolic processes).

The high energy of lightning splits nitrogen molecules in the atmosphere, allowing them to combine with oxygen to form nitrogen oxides. These dissolve in rain to form nitrates that enter the soil.

Leguminous plants, like peas and beans, form a symbiotic relationship with *Rhizobium* bacteria. The bacteria reside in and infect the root hairs, leading to the formation of specialized structures called root nodules where nitrogen fixation occurs.

Antiseptics are chemical agents applied to living tissue, such as a wound, to kill or inhibit the growth of microorganisms, thereby preventing infection.

The common cold virus is spread through respiratory droplets. When an infected person sneezes or coughs, these droplets are released into the air and can be inhaled by a healthy person.

Flagella are long, whip-like appendages that protrude from the cell body of some bacteria. Their rotation propels the bacterium through its environment.

Dehydration is the process of removing water from food. Since microorganisms need moisture to grow, this method prevents spoilage and inhibits their growth.

Yellow vein mosaic is a viral disease that affects okra (bhindi). Citrus canker is bacterial, rust of wheat is fungal, and blight of potato is also a fungal disease.

Antibodies are Y-shaped proteins produced by the immune system in response to antigens (foreign substances). They specifically bind to pathogens to neutralize or mark them for destruction.

Foot and mouth disease is a highly contagious viral disease that affects cloven-hoofed animals like cattle, sheep, and pigs. It can be transmitted from animal to animal.

Saprotrophs, also called saprophytes, are organisms that feed on dead and decaying organic matter. They secrete digestive enzymes onto the matter and then absorb the nutrients, playing a key role in decomposition.

During anaerobic decomposition (in the absence of oxygen), microbes break down organic waste and produce biogas, a mixture of gases that is primarily composed of methane.

Several fungi are used to produce antibiotics. The most famous example is *Penicillium* fungus, from which the first antibiotic, penicillin, was derived.

Amoebic dysentery is caused by a protozoan called *Entamoeba histolytica*. It infects the large intestine, leading to severe diarrhea and abdominal pain.

Using salt (sodium chloride) for preservation is a chemical method. Salt draws water out of microbial cells through osmosis, inhibiting their growth, and also creates an environment that is hostile for many spoilage organisms.

Boiling water kills most pathogens that cause water-borne diseases. Regular hand washing, especially before eating or preparing food, prevents the transmission of these pathogens from contaminated surfaces to the mouth.

Louis Pasteur was a French scientist who invented pasteurization, a process of heating liquids like milk and wine to kill harmful bacteria without destroying the product’s quality.

Malaria is caused by the protozoan parasite *Plasmodium*. It is transmitted to humans through the bite of an infected female *Anopheles* mosquito.

The majority of naturally occurring antibiotics are derived from bacteria (like *Streptomyces*) and fungi (like *Penicillium*). These organisms produce these substances as a defense mechanism against other microbes.

Smoking is a traditional preservation method, especially for fish and meat. The smoke contains antimicrobial compounds and also dehydrates the food’s surface, both of which inhibit microbial growth.

Crop rotation is the practice of growing different types of crops in the same area in sequenced seasons. This helps improve soil health, manage pests, and prevent the depletion of specific soil nutrients.

*Acetobacter* are bacteria that oxidize ethanol (alcohol) to acetic acid, the main component of vinegar. They are used in the second stage of vinegar production after yeast has fermented a sugar source into alcohol.

An epidemic is a sudden increase in the number of cases of a disease above what is normally expected in a specific population or geographic area.

Bacteria have three main shapes: spherical (coccus), rod-shaped (bacillus), and spiral (spirillum). Cubical is not a standard bacterial shape.

Yeast in the batter ferments the sugars present, producing carbon dioxide gas. This gas gets trapped in the batter, forming bubbles that make the idli and dosa spongy and fluffy.

Rabies is a viral disease that affects the central nervous system. It is transmitted through the saliva of an infected animal, most commonly through a bite, and is almost always fatal if not treated promptly.

Vaccination is the process of administering a vaccine, which contains a weakened or inactivated form of a pathogen. This triggers the immune system to produce antibodies and create immunological memory without causing the disease.

Excessive growth of algae, known as algal blooms, can be harmful. They deplete oxygen in the water (creating dead zones), block sunlight, and some species can release toxins that harm aquatic life and contaminate drinking water.

*Clostridium tetani* causes tetanus, a disease commonly known as lockjaw. The bacterial toxin causes painful muscle stiffness and spasms, particularly in the jaw and neck muscles.

The production of soy sauce and tempeh involves fermentation using specific fungi. For tempeh, *Rhizopus oligosporus* is used, and for soy sauce, a combination of *Aspergillus* moulds and yeasts are used in the fermentation process.

A layer of oil on top of pickles acts as a seal, preventing air (oxygen) from coming into contact with the pickles. This prevents the growth of aerobic spoilage-causing microorganisms, helping to preserve the pickles.

A classic example of an asymptomatic carrier is “Typhoid Mary” (Mary Mallon), a cook who spread typhoid fever to many people while never showing symptoms of the disease herself.

Extremophiles are organisms, primarily microorganisms, that thrive in physically or geochemically extreme conditions that are detrimental to most life on Earth, such as high temperatures, extreme pH, or high salinity.

The female *Anopheles* mosquito is the sole vector for transmitting malaria. It carries the *Plasmodium* parasite, which is injected into the human host when the mosquito takes a blood meal.

Nitrification is a two-step aerobic process carried out by specific bacteria. First, ammonia (NH₃) is oxidized to nitrite (NO₂⁻), and then nitrite is further oxidized to nitrate (NO₃⁻), which is a form of nitrogen readily absorbed by plants.

A standard ORS solution is a mixture of clean water, salt (sodium chloride), and sugar (glucose). This combination is scientifically formulated to optimize water absorption in the intestines. Lemon juice is not a required component.

A chronic disease is a long-lasting condition that typically persists for three months or more. It may progress slowly and often requires ongoing medical management. Examples include diabetes, heart disease, and arthritis.

*Chlamydomonas* is a single-celled green alga. It contains chloroplasts and can carry out photosynthesis to produce its own food, unlike fungi (mushroom, *Penicillium*) or heterotrophic protozoa (amoeba).

The primary purpose of vaccination is to stimulate the body’s own immune system to build a defense (immunity) against a specific pathogen, providing long-term protection before exposure to the actual disease.

Smallpox is the only human disease to have been completely eradicated worldwide. This was achieved through a successful global vaccination campaign led by the World Health Organization, with the last natural case occurring in 1977.

The common black mold seen on stale bread is typically *Rhizopus stolonifer*. It is a fast-growing fungus with a characteristic appearance of black sporangia on white, cottony hyphae.

Misuse and overuse of antibiotics accelerate the process of antimicrobial resistance. Bacteria can evolve to survive exposure to an antibiotic, rendering that drug less effective or completely ineffective for treating future infections.