Microorganisms Study Notes: Bacterial Classification

Definition: Bacteria are unicellular, prokaryotic organisms.
Classification Criteria:
- Shape:
  - Cocci (spherical)
  - Bacilli (rod-shaped)
  - Spirilla (spiral-shaped)
- Gram Staining:
  - Gram-positive: Thick peptidoglycan layer, retains crystal violet stain.
  - Gram-negative: Thin peptidoglycan layer, does not retain crystal violet stain, appears pink after counterstaining.
- Oxygen Requirement:
  - Aerobic: Require oxygen.
  - Anaerobic: Do not require oxygen; some can tolerate it (facultative anaerobes).
- Metabolism:
  - Autotrophic: Produce own food (e.g., photosynthetic, chemosynthetic).
  - Heterotrophic: Consume organic substances.
Reproduction: Primarily asexual via binary fission.

Definition: Fungi are eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds, mushrooms).
Characteristics:
- Cell wall composed of chitin.
- Heterotrophic, obtaining nutrients through absorption.
Reproduction:
- Asexual: Via spores (conidia, budding in yeasts).
- Sexual: Through the formation of specialized structures (e.g., asci in ascomycetes).
Major Groups:
- Chytridiomycota (chytrids)
- Zygomycota (bread molds)
- Ascomycota (sac fungi)
- Basidiomycota (club fungi)
Ecological Roles:
- Decomposers: Break down dead organic matter.
- Symbionts: Form mutualistic relationships (e.g., mycorrhizae with plants).

Bacteria: Prokaryotic, diverse in habitat and function, vital for nutrient cycling.
Fungi: Eukaryotic, essential for decomposition, include yeasts and molds.
Viruses: Acellular entities that require a host to reproduce; consist of DNA/RNA surrounded by a protein coat.
Protozoa: Unicellular eukaryotes, often motile, can be free-living or parasitic (e.g., amoebas, flagellates).
Algae: Photosynthetic eukaryotes, can be unicellular or multicellular, important in aquatic ecosystems as primary producers.
Archaea: Prokaryotic, similar to bacteria but genetically distinct; often extremophiles (e.g., thermophiles, halophiles).

Bacteria are unicellular and prokaryotic organisms.
Classification based on shape:
- Cocci: Spherical bacteria.
- Bacilli: Rod-shaped bacteria.
- Spirilla: Spiral-shaped bacteria.
Gram Staining distinguishes bacteria into:
- Gram-positive: Thick peptidoglycan layer, retains crystal violet stain.
- Gram-negative: Thin peptidoglycan layer, does not retain crystal violet stain, appears pink.
Oxygen requirements categorize bacteria into:
- Aerobic: Require oxygen for survival.
- Anaerobic: Do not require oxygen; facultative anaerobes can tolerate oxygen.
Metabolic classification includes:
- Autotrophic: Produce their own food through methods like photosynthesis or chemosynthesis.
- Heterotrophic: Consume organic substances for energy.
Bacteria primarily reproduce asexually through binary fission.

Fungi are eukaryotic organisms; can be unicellular (yeasts) or multicellular (molds, mushrooms).
Characterized by a cell wall made of chitin and are heterotrophic, obtaining nutrients via absorption.
Reproduction methods:
- Asexual: Via spores, such as conidia or budding in yeasts.
- Sexual: Involves specialized structures, e.g., asci in ascomycetes.
Major fungal groups include:
- Chytridiomycota: Chytrids, primarily aquatic.
- Zygomycota: Bread molds, used in food production.
- Ascomycota: Sac fungi, includes yeast and mold varieties.
- Basidiomycota: Club fungi, includes mushrooms.
Ecological roles:
- Decomposers: Break down dead organic matter, recycling nutrients.
- Symbionts: Engage in mutualism, such as forming mycorrhizae with plant roots.

Bacteria: Prokaryotic, indispensable for nutrient cycling and have diverse habitats.
Fungi: Eukaryotic organisms, crucial for decomposition, includes yeasts and molds.
Viruses: Acellular entities requiring a host for reproduction; consist of DNA or RNA encased in a protein coat.
Protozoa: Unicellular eukaryotes, often motile; can be free-living or parasitic (e.g., amoebas, flagellates).
Algae: Photosynthetic eukaryotes, range from unicellular to multicellular forms; essential primary producers in aquatic ecosystems.
Archaea: Prokaryotic organisms akin to bacteria but genetically distinct; often known as extremophiles, living in extreme environments like hot springs or salt lakes.