General characteristics and classification of bacteria and fungi

General Characteristics of Bacteria

1. Cell Structure: Bacteria are prokaryotic organisms lacking membrane-bound nuclei and organelles. They have a simple structure with a cell wall made of peptidoglycan.
2. Shape: Common shapes include cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).
3. Reproduction: Bacteria primarily reproduce asexually through binary fission.
4. Metabolism: They exhibit diverse metabolic pathways, including autotrophy (producing food) and heterotrophy (absorbing nutrients).
5. Size: Typically small, ranging from 0.2 to 10 micrometres in diameter.
6. Genetic Material: Bacteria usually have a single circular chromosome and may also contain plasmids, which are small, circular DNA molecules.
7. Movement: Some bacteria are motile, using flagella or pili for locomotion.

Classification:

• Gram Staining: Based on their cell wall composition, bacteria are classified into Gram-positive (thick peptidoglycan layer) and Gram-negative (thin layer with an outer membrane).
• Oxygen Requirements:
  • Aerobic: Requires oxygen.
  • Anaerobic: Do not require oxygen and may be harmed by it.
  • Facultative: Can survive with or without oxygen.
• Metabolic Type:
  • Autotrophic: Include photoautotrophs and chemoautotrophs.
  • Heterotrophic: Include saprophytic and parasitic bacteria.
• Shape and Arrangement: Cocci (singular or in chains), bacilli (single or in clusters), etc.

Importance of Bacteria:

• Decomposers: Bacteria are crucial in breaking down organic matter and recycling ecosystem nutrients.
• Symbiosis: Many bacteria form beneficial relationships with plants and animals (e.g., gut bacteria aiding in digestion).
• Pathogens: Some bacteria can cause diseases in humans, animals, and plants (e.g., streptococcus, E. coli).
• Biotechnology: Bacteria are used in various applications, including fermentation (e.g., yoghurt production) and genetic engineering.

General Characteristics of Fungi:

1. Cell Structure: Fungi are eukaryotic organisms with a defined nucleus and organelles. Their cell walls contain chitin.
2. Morphology: They can exist as single-celled organisms (yeasts) or multicellular (molds and mushrooms). Fungi often have a filamentous structure known as mycelium.
3. Reproduction: Fungi can reproduce asexually (e.g., budding, fragmentation) and sexually (spore formation).
4. Metabolism: Fungi are heterotrophic, obtaining nutrients through absorption. They are decomposers, breaking down organic material.
5. Size: Varies widely, from microscopic yeasts to large mushrooms.

Classification:

• Chytridiomycota: Aquatic fungi with flagellated spores.
• Zygomycota: Includes molds; known for zygospore formation.
• Ascomycota: The largest group, includes yeasts and morels; characterized by ascus (sac-like structure).
• Basidiomycota: Includes mushrooms and puffballs; characterized by basidium (club-shaped structure).
• Glomeromycota: Forms arbuscular mycorrhizal associations with plant roots.

Importance of Fungi:

• Decomposers: Fungi play a crucial role in nutrient cycling by breaking down dead organic matter and returning nutrients to the ecosystem.
• Food Sources: Many fungi are edible (e.g., mushrooms) and are used in food production (e.g., yeast in bread and fermentation).
• Medicinal Uses: Some fungi produce antibiotics (e.g., penicillin) and other pharmaceuticals.
• Pathogens: Certain fungi can cause plant, animal, and human diseases.