Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Describe key characteristics of Bacteria and Fungi.
• Explain structural differences between Bacteria and Fungi.
• Describe their beneficial and harmful roles with South African examples.
• Explain the importance of hygiene in controlling their spread.
• Identify micro-organisms based on their characteristics.

Lesson summary

Micro-organisms, despite their tiny size, play a vital role in our lives and the environment. From the bacteria in our gut that aid digestion to the fungi that decompose organic matter, these organisms are essential for maintaining ecological balance and human health. This week, we will delve into the biodiversity of micro-organisms, focusing on their classification and characteristics. Understanding this biodiversity is crucial in South Africa as it relates to issues like food security (through soil bacteria and plant diseases), public health (identifying and combating pathogens), and environmental sustainability (bioremediation).

Lesson notes

2. 1.

Classification of Micro-organisms: Bacteria (Monera) The Kingdom Monera consists solely of bacteria, which are prokaryotic organisms. "Prokaryotic" means they lack a membrane-bound nucleus and other membrane-bound organelles.

Key Characteristics: Cell Structure: Unicellular, prokaryotic cells. Their cell walls are made of peptidoglycan (a unique substance not found in eukaryotes). They lack a true nucleus; their genetic material (DNA) is a single circular chromosome located in the cytoplasm (nucleoid region).

Shape: Bacteria come in various shapes: Cocci: Spherical (e.g., Streptococcus, causes strep throat)

Bacilli: Rod-shaped (e.g., Escherichia coli (E. coli))

Spirilla: Spiral-shaped (e.g., Spirillum, some cause waterborne diseases)

Vibrio: Curved rod (e.g., Vibrio cholerae, causes cholera)

Nutrition: Bacteria exhibit diverse modes of nutrition: Autotrophs: Some bacteria are photosynthetic (e.g., cyanobacteria) using sunlight to produce their own food. Others are chemosynthetic, using chemical energy (e.g., bacteria in deep-sea vents).

Heterotrophs: Most bacteria are heterotrophic, obtaining nutrients from organic matter. Some are saprophytes (decomposers), while others are parasites (living in or on other organisms, causing harm).

Reproduction: Bacteria primarily reproduce asexually through binary fission, a process where the cell divides into two identical daughter cells. Under unfavourable conditions, some bacteria can form endospores, which are resistant structures that can survive harsh conditions and germinate when conditions become favourable.

Movement: Some bacteria are motile, using flagella (whip-like structures) to move. Others are non-motile.

Gram Staining: Bacteria can be classified based on their cell wall structure using Gram staining. Gram-positive bacteria have a thick peptidoglycan layer and stain purple, while Gram-negative bacteria have a thin peptidoglycan layer and stain pink/red. This difference is crucial for antibiotic selection. 2.

2. Classification of Micro-organisms: Fungi Fungi belong to the Kingdom Fungi, which consists of eukaryotic organisms. "Eukaryotic" means they possess a membrane-bound nucleus and other membrane-bound organelles.

Key Characteristics: Cell Structure: Eukaryotic cells. Fungal cell walls are made of chitin (a complex carbohydrate also found in insect exoskeletons). They have a true nucleus containing multiple chromosomes. Fungi can be unicellular (e.g., yeast) or multicellular (e.g., mushrooms). Multicellular fungi are composed of hyphae, which are thread-like filaments that intertwine to form a mycelium (the vegetative part of the fungus).

Nutrition: Fungi are heterotrophic. They obtain nutrients by absorption.

Saprophytes: Most fungi are saprophytes, decomposing dead organic matter (e.g., bread mould).

Parasites: Some fungi are parasites, living on or in other organisms, causing diseases (e.g., athlete's foot fungus).

Mutualists: Some fungi form mutualistic relationships with other organisms (e.g., mycorrhizae, which associate with plant roots, helping them absorb nutrients).

Reproduction: Fungi reproduce both sexually and asexually.

Asexual Reproduction: Includes spore formation, budding (in yeast), and fragmentation.

Sexual Reproduction: Involves the fusion of hyphae from different mating types, resulting in the formation of spores.

Structure: Fungi can exist as single-celled yeasts, filamentous molds, or complex fruiting bodies (mushrooms). 2.

3. Examples and their Relevance in South Africa: Bacteria: Mycobacterium tuberculosis (causes tuberculosis): A major health concern in South Africa, especially among individuals with HIV/AIDS. Understanding its classification and characteristics is crucial for diagnosis and treatment.

Rhizobium (nitrogen-fixing bacteria): Found in the roots of legumes, playing a vital role in nitrogen fixation and improving soil fertility for agriculture. A crucial consideration for sustainable farming practices in South Africa. Streptococcus pneumoniae (causes pneumonia): A common cause of pneumonia, especially in young children and the elderly in South Africa.

Fungi: Penicillium (produces penicillin): An important source of antibiotics, used to treat bacterial infections. South Africa relies on antibiotics to manage various diseases.

Aspergillus flavus (produces aflatoxins): A common contaminant of crops like maize and groundnuts, which can be toxic to humans and animals. A major concern for food safety and agricultural practices in South Africa. Aflatoxins can lead to liver cancer.

Yeast (Saccharomyces cerevisiae): Used in the production of bread and beer, important food and beverage industries in South Africa. Guided Practice (With Solutions)

Question 1: Identify the following micro-organism based on the given characteristics: Unicellular, prokaryotic, rod-shaped, peptidoglycan cell wall.

Solution: This micro-organism is a bacterium (specifically a bacillus).