STUDY GUIDE (Ch. 6) : Bacteria, Protists, and Fungi – Classification, Roles, and Impact

Bacteria (Prokaryotes)

Classification and Properties of Prokaryotes

Bacteria are single-celled prokaryotic organisms that exhibit a wide range of structural and functional diversity. Their classification is based on various properties, including cell wall composition, shape, and metabolic capabilities.

• Classification of Prokaryotes: Prokaryotes are classified by characteristics such as cell shape (cocci, bacilli, spirilla), cell wall structure, and metabolic pathways.

• Gram Staining: The Gram stain is a differential staining technique that divides bacteria into Gram-positive and Gram-negative groups based on cell wall composition.

• Antibiotic Resistance: Some bacteria develop resistance to antibiotics, making infections harder to treat and posing a significant public health risk.

• Roles of Bacteria: Bacteria can be pathogens, beneficial organisms in food production, environmental recyclers, and tools in biotechnology.

Example: Escherichia coli is a Gram-negative bacterium found in the intestines; some strains are pathogenic, while others are harmless.

Additional info: Gram-positive bacteria have thick peptidoglycan cell walls, while Gram-negative bacteria have thin peptidoglycan layers and an outer membrane.

Protists

Diversity and Impact of Protists

Protists are a diverse group of mostly unicellular eukaryotic organisms. They play important roles in ecosystems and can also cause diseases in humans and other organisms.

• Variety of Protists: Protists include algae, protozoa, and slime molds, exhibiting a wide range of forms and lifestyles.

• Pathogenic Protists: Some protists, such as Plasmodium (causative agent of malaria), can cause serious diseases.

• Toxin Production: Certain protists release toxins that can affect other organisms in their environment.

Example: Plasmodium species cause malaria by infecting red blood cells.

Additional info: Algal blooms caused by protists can release toxins harmful to aquatic life and humans.

Fungi

Forms, Roles, and Importance of Fungi

Fungi are eukaryotic organisms that exist in various forms, including yeasts, molds, and mushrooms. They play crucial roles in ecosystems, food production, and medicine.

• Variety of Fungal Forms: Fungi can be unicellular (yeasts) or multicellular (molds, mushrooms).

• Fungi as Food Sources: Many fungi are edible and used in food production, such as Agaricus bisporus (common mushroom) and Saccharomyces cerevisiae (baker's yeast).

• Fungi as Pathogens: Some fungi cause diseases in plants, animals, and humans (e.g., athlete's foot, ringworm).

• Fungi in Medicine: Fungi are sources of important medicines, such as antibiotics (e.g., penicillin from Penicillium species).

Example: Penicillium notatum produces penicillin, the first widely used antibiotic.

Additional info: Fungi decompose organic matter, recycling nutrients in ecosystems.