Microorganisms: Friend and Foe – Vocabulary Review

These vocabulary flashcards cover the essential terms, organisms, processes, and scientists discussed in the lecture chapter “Microorganisms: Friend and Foe.” Use them to review beneficial and harmful roles of microbes, key biological processes, and methods of food preservation and disease prevention.

Microorganism (Microbe)

A living organism too small to be seen with the unaided eye; includes bacteria, fungi, protozoa, some algae, and viruses.

Bacteria

Single-celled microorganisms that may exist as independent organisms or live in colonies; can be beneficial (e.g., nitrogen fixation) or pathogenic (e.g., cholera).

Fungi

A group of microorganisms that include molds and yeasts; may be unicellular or multicellular and often decompose organic matter.

Protozoa

Single-celled, animal-like microorganisms such as Amoeba or Plasmodium; some cause diseases like malaria.

Algae

Photosynthetic microorganisms; some species are microscopic and contribute to nitrogen fixation (e.g., blue-green algae).

Virus

A microscopic infectious agent that can reproduce only inside the cells of a host organism, causing diseases like flu, polio, and chickenpox.

Yeast

A unicellular fungus used in baking and brewing because it ferments sugars to produce carbon dioxide and alcohol.

Lactobacillus

A bacterium that converts milk into curd by fermenting lactose; also used in making cheese and other dairy products.

Rhizobium

Nitrogen-fixing bacterium living symbiotically in root nodules of leguminous plants, enriching soil fertility.

Blue-green Algae (Cyanobacteria)

Photosynthetic microorganisms that fix atmospheric nitrogen and improve soil fertility.

Pathogen

Any microorganism that causes disease in humans, animals, or plants.

Carrier

An organism (often an insect) that transmits pathogens from one host to another, e.g., female Anopheles mosquito for malaria.

Communicable Disease

An illness caused by pathogens that can spread from an infected person to a healthy person through air, water, food, or contact.

Antibiotic

A medicine produced by microorganisms (or synthetically) that kills or inhibits other microbes; examples include penicillin and streptomycin.

Penicillin

The first commercial antibiotic, discovered by Alexander Fleming from the mold Penicillium; effective against many bacterial infections.

Streptomycin

An antibiotic derived from bacteria that is effective against tuberculosis and other bacterial diseases.

Antibodies

Proteins produced by the body’s immune system to neutralize or destroy invading pathogens.

Vaccine

A preparation of weakened or dead pathogens used to stimulate immunity and prevent specific diseases (e.g., polio drops).

Fermentation

The conversion of sugars into alcohol and carbon dioxide by microorganisms such as yeast; discovered by Louis Pasteur.

Pasteurization

Heat treatment (about 70 °C for 15–30 s) followed by rapid cooling to kill harmful microbes in milk without affecting taste; devised by Louis Pasteur.

Food Preservation

Methods used to prevent spoilage by inhibiting microbial growth, such as salting, sugaring, oil & vinegar, heat, refrigeration, and airtight packing.

Preservative

A chemical (e.g., salt, sugar, sodium benzoate) added to food to inhibit microbial growth and extend shelf life.

Common-Salt Preservation

Use of dry salt to inhibit bacterial growth in foods like meat, fish, amla, and raw mangoes.

Sugar Preservation

High sugar concentration in jams and jellies reduces water availability, preventing bacterial growth.

Oil and Vinegar Preservation

Method that creates an acidic or oxygen-limited environment unsuitable for bacterial survival; used in pickles.

Food Poisoning

Illness caused by consuming food contaminated with toxin-producing microorganisms.

Decomposition

Microbial breakdown of dead organic matter into simpler substances, recycling nutrients in ecosystems.

Biological Nitrogen Fixer

Microorganism (bacteria or blue-green algae) that converts atmospheric nitrogen into usable nitrogenous compounds in soil.

Nitrogen Fixation

The process of converting atmospheric nitrogen into ammonia or related compounds usable by plants, accomplished by microbes or lightning.

Nitrogen Cycle

The continual movement of nitrogen among atmosphere, soil, plants, animals, and microorganisms through fixation, uptake, decomposition, and denitrification.

Symbiotic Relationship

A mutually beneficial association between two organisms, such as Rhizobium bacteria and leguminous plant roots.

Root Nodule

A swelling on the root of a legume housing Rhizobium bacteria for nitrogen fixation.

Female Anopheles Mosquito

Insect carrier (vector) that transmits malaria-causing protozoan (Plasmodium) to humans.

Female Aedes Mosquito

Mosquito species that carries dengue virus and transmits it to humans.

Anthrax

A serious disease of humans and cattle caused by the bacterium Bacillus anthracis; discovered by Robert Koch.

Pasteurized Milk

Milk that has been heat-treated to eliminate harmful microbes, making it safe to drink without further boiling.