Economic Importance of Bacteria and Fungi

The One Thing

Bacteria and fungi have both beneficial and harmful economic effects, depending on the species, the conditions in which they grow, and how humans use or control them. Their major beneficial roles include food and medicine production, decomposition, nutrient cycling, agriculture, and environmental cleaning, whereas harmful species cause disease, spoilage, and material damage.

Reactions, Processes and Experiments

Key Terms

• Decomposers: Organisms that break down dead and decaying matter into simpler substances, returning nutrients to the environment.
• Nitrogen fixation: The conversion of atmospheric nitrogen into usable nitrogen compounds by certain bacteria, such as Rhizobium in the root nodules of leguminous plants.
• Fermentation: The breakdown of sugars by microorganisms, usually without oxygen, producing useful products such as alcohol, acids, or gases.
• Antibiotics: Substances produced by some microorganisms that kill or stop the growth of disease-causing bacteria.
• Pathogens: Disease-causing microorganisms, including harmful bacteria and fungi.
• Mycorrhiza: A mutually beneficial association between certain fungi and plant roots; the fungus improves water and mineral absorption while receiving food from the plant.
• Food spoilage: The undesirable change in food caused by the growth and activities of microorganisms.
• Mushroom cultivation: The controlled growing of edible fungi as a source of food and income.
• Biofertiliser: A preparation containing useful microorganisms that improve soil fertility or plant nutrient availability.
• Bioremediation: The use of microorganisms to break down pollutants and help clean contaminated soil or water.
• Antibiotic resistance: A condition in which bacteria are no longer effectively killed or inhibited by an antibiotic, often associated with misuse of antibiotics.

Easily Confused

• Yeast and mushrooms: Yeast is a single-celled fungus, whereas mushrooms are multicellular fungi.
• Fermentation and aerobic respiration: Fermentation usually occurs without oxygen and produces products such as alcohol and carbon dioxide; aerobic respiration uses oxygen and produces carbon dioxide, water, and energy.
• Useful and harmful microorganisms: The same broad group may contain species that produce food or medicines and species that cause disease, spoilage, or material damage.
• Decomposition and food spoilage: Decomposition is an environmentally beneficial process that recycles nutrients, whereas food spoilage is an undesirable change that makes food unacceptable or unsafe.
• Mycorrhiza and nitrogen fixation: Mycorrhiza involves fungi improving plant uptake of water and minerals, especially phosphorus; nitrogen fixation involves bacteria converting atmospheric nitrogen into usable nitrogen compounds.
• Edible and poisonous mushrooms: Edible mushrooms provide proteins, vitamins, minerals, and fibre, whereas poisonous mushrooms must not be eaten.
• Biofertilisers and bioremediation: Biofertilisers improve soil fertility or plant nutrient availability; bioremediation uses microorganisms to break down pollutants in contaminated soil or water.
• Food preservation methods: Drying, salting, sugaring, refrigeration, pasteurisation, canning, and chemical preservation all control microbial growth, but they do so through different processes.

What Gets Asked

• Questions may ask for useful bacteria and their applications, such as Rhizobium in nitrogen fixation, Lactobacillus in curd production, and Acetobacter in vinegar production. Marks are lost by naming the organism without linking it to the correct product or process.
• Questions may require the equation for alcoholic fermentation: sugar → alcohol + carbon dioxide + energy. Marks are lost by omitting carbon dioxide or by confusing fermentation with aerobic respiration.
• Questions may ask how yeast is used in baking and brewing. The required distinction is that carbon dioxide makes bread dough rise, while alcohol is produced during brewing.
• Questions may ask about the economic importance of fungi, including Penicillium, edible mushroom cultivation, decomposition, humus formation, and mycorrhiza. Marks are lost by treating all fungi as harmful or by failing to state the benefit to plants or soil.
• Questions may require examples of diseases caused by harmful bacteria and fungi, including cholera, typhoid, tuberculosis, pneumonia, food poisoning, ringworm, athlete’s foot, rust of wheat, and smut of maize. Marks are lost by assigning a disease to the wrong group.
• Questions may ask how food or materials are protected from microorganisms. Answers should identify methods such as drying, salting, sugaring, refrigeration, pasteurisation, canning, and chemical preservation, and should relate them to slowing or preventing microbial growth.
• Questions may ask about conditions favouring microbial growth or the consequences of poor control. Warmth, moisture, food supply, and suitable pH encourage growth, which may result in disease, food spoilage, or damage to leather, cotton, wood, paper, and stored grains.