Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Define micro-organisms and their significance, with South African examples.
• Describe and differentiate the basic structures of viruses and bacteria.
• Classify micro-organisms into their major groups.
• Explain the beneficial and harmful roles of micro-organisms.

Lesson summary

Micro-organisms, often invisible to the naked eye, play a pivotal role in our lives and the environment. They are incredibly diverse, ranging from bacteria and archaea to fungi, protists, and even viruses. Understanding their biodiversity and how they are classified is crucial. Firstly, micro-organisms are vital for processes like decomposition, nutrient cycling, and food production (think amasi, mageu, and bread). Secondly, some are essential for our health, such as the bacteria in our gut that aid digestion.

However, others are pathogenic and cause diseases like tuberculosis (TB) and cholera, which are significant health challenges in South Africa.

Lesson notes

What are Micro-organisms? Micro-organisms, also known as microbes, are living organisms too small to be seen with the naked eye. They include bacteria, archaea, fungi (some types), protists, and viruses.

Importance of Micro-organisms: Decomposers: Break down dead organic matter, returning nutrients to the soil. In South Africa, this is crucial for maintaining soil fertility in agricultural areas and natural ecosystems.

Nutrient Cycling: Play a key role in cycles like the nitrogen cycle, ensuring the availability of essential elements for plant growth. Nitrogen-fixing bacteria in the soil convert atmospheric nitrogen into usable forms for plants, improving crop yields.

Food Production: Used in the production of many traditional foods.

Examples in South Africa include: Amasi: A fermented milk product, similar to yogurt. The fermentation process involves bacteria like Lactococcus lactis and Streptococcus thermophilus.

Mageu: A traditional fermented maize-based drink. Lactobacillus bacteria are involved in the fermentation process, giving it a slightly sour taste.

Bread: Yeast (a type of fungi), such as Saccharomyces cerevisiae,* is used to make bread rise.

Human Health: Some microbes are beneficial, aiding in digestion (gut bacteria).

However, others are pathogenic, causing diseases.

Bioremediation: Microbes can be used to clean up pollutants in the environment. For example, certain bacteria can break down oil spills. This is particularly relevant in South Africa, where industrial activities can lead to pollution.

Classification of Micro-organisms: Micro-organisms are broadly classified into the following groups: Viruses: Non-cellular entities. They are not considered living organisms because they cannot reproduce on their own.

Structure: A virus consists of a nucleic acid core (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an envelope derived from the host cell membrane.

Reproduction: Viruses can only replicate inside a host cell, using the host's cellular machinery.

Examples: HIV (causes AIDS), Influenza virus (causes flu), SARS-CoV-2 (causes COVID-19).

Example: Consider the HIV virus, a major health concern in South Africa. HIV infects immune cells, weakening the immune system and leading to AIDS. The virus attaches to the host cell, injects its RNA, and hijacks the cell's machinery to create more viral particles.

Bacteria: Prokaryotic cells (lack a nucleus and other membrane-bound organelles).

Structure: Cell wall, cell membrane, cytoplasm, ribosomes, and a circular DNA molecule (nucleoid). Some bacteria also have plasmids (small, circular DNA molecules) and flagella (for movement).

Reproduction: Primarily through binary fission (asexual reproduction).

Examples: Escherichia coli (some strains cause food poisoning), Streptococcus pneumoniae (causes pneumonia), Mycobacterium tuberculosis (causes tuberculosis).

Example: Mycobacterium tuberculosis, the bacterium responsible for TB, a leading cause of death in South Africa. These bacteria primarily infect the lungs, causing coughing, fever, and weight loss. Understanding the bacterial structure and its mechanisms of infection is crucial for developing effective treatments.

Fungi: Eukaryotic cells (have a nucleus and other membrane-bound organelles).

Structure: Cell wall (made of chitin), hyphae (thread-like filaments), mycelium (a network of hyphae).

Reproduction: Can reproduce sexually or asexually (through spores).

Examples: Yeast (Saccharomyces cerevisiae), mold (Penicillium), mushrooms. Some fungi cause diseases like athlete's foot and ringworm.

Example: Aspergillus flavus, a fungus that can contaminate maize (mealies) with aflatoxins. Aflatoxins are toxic substances that can cause liver damage and cancer. This is a concern in South Africa, where maize is a staple food.

Protists: Eukaryotic cells that are not fungi, plants, or animals.

Structure: Highly diverse; can be unicellular or multicellular.

Reproduction: Can reproduce sexually or asexually.

Examples: Amoeba, Paramecium, Plasmodium (causes malaria).

Example: Plasmodium, the protist that causes malaria, a significant public health problem in certain regions of South Africa. Plasmodium is transmitted to humans through mosquito bites, infecting liver and blood cells. Distinguishing between Viruses and Bacteria: | Feature | Virus | Bacteria | | ---------------- | ------------------------------------- | --------------------------------------- | | Cellular Structure | Non-cellular | Cellular (prokaryotic) | | Genetic Material | DNA or RNA | DNA | | Reproduction | Requires a host cell | Binary fission | | Size | Much smaller than bacteria | Larger than viruses | | Treatment | Antiviral drugs or vaccines | Antibiotics | Guided Practice (With Solutions)

Question 1: Define the term "micro-organism" and provide three reasons why studying them is important in the South African context.