Kingdoms Eubacteria and Archaebacteria (Bio Unit 2 Quest 1)

Kingdoms Eubacteria and Archaebacteria

Overview of the 5 Kingdom System

  • Linnaeus’ Classification: Initiated with 2 kingdoms: Animalia and Plantae. This binary system remained until the invention of the microscope.
  • Revisions: As new organisms were discovered, classifications became complicated:
    • Introduction of a third kingdom, Protista, for organisms that did not fit into plants or animals (essentially a "junk drawer" for diverse organisms).
    • Development of the 5 kingdom system: Animalia, Plantae, Protista, Fungi, and Monera (the latter for prokaryotic organisms).
  • Bacteria Classification: In recent years, bacteria were divided into two kingdoms: Eubacteria and Archaebacteria.

Archaebacteria

  • Origins: The term 'archae' means early or primitive, indicating their ancient origins.
  • Environment: Thrive in extreme conditions where other life forms cannot survive, such as high temperatures, high salinity, and high acidity. They can exist in anaerobic (without oxygen) environments, mimicking early Earth conditions.
Major Groups of Archaebacteria
  1. Methanogens: Produce methane, often found in the guts of animals aiding in cellulose digestion.
  2. Thermophiles: Can withstand extreme heat.
  3. Halophiles: Live in high salinity environments.
Importance of Archaebacteria
  • Scientific Research: Their ability to thrive in extreme conditions provides insight into ancient Earth’s environment.
  • Biological Roles: Involved in carbon, nitrogen, and sulfur cycles. For example, Methanobacterium ruminantium aids in cellulose digestion in animal guts.
  • Applications: Enzymes from extremophiles are utilized in high-temperature industrial processes and in antibiotic development.
Characteristics of Archaebacteria
  • Cell Wall Composition: Lacks peptidoglycan; cell walls are made of glycoproteins and polysaccharides.
  • Resistance: High resistance to antibiotics.
  • Structure: Unicellular and prokaryotic.
  • Reproduction: Asexual reproduction through binary fission.
  • Nutrition: Can be heterotrophic or autotrophic.

Bacteria (Domain: Eubacteria)

  • Prevalence: Each cm² of human skin has approximately 100,000 bacteria. A teaspoon of topsoil contains over 1 billion bacteria.
Characteristics of Eubacteria
  • Diversity: Most are beneficial; some can be harmful.
  • Structure: Unicellular and prokaryotic; exist as aerobic (requiring oxygen) or anaerobic (not requiring oxygen) organisms.
  • Classification by Shape: 1) Spherical (cocci), 2) Rod (bacilli), 3) Spiral (spirilla).
Makeup of Bacteria
  • Genetic Material: Composed of a single circular chromosome and smaller pieces called plasmids.
  • Components: Contains ribosomes, which are essential for protein synthesis.
Representative Organisms and Their Impacts
  1. Spiral Bacteria:
    • Example: B. burgdorferi (causes Lyme disease).
    • Shape and motility vary among species.
  2. Rod Bacteria:
    • Example: E. coli, found in the intestines of warm-blooded animals.
    • Capable of both aerobic and anaerobic respiration.
  3. Sphere Bacteria:
    • Example: Streptococcus pneumoniae (causes respiratory infections and meningitis).
    • Transmitted via direct contact, commonly treated with penicillin.

Classification of Eubacteria

  • Shape-Based Classification:
    1. Spherical: coccus (singular); cocci (plural)
    2. Rod-shaped: bacillus (singular); bacilli (plural)
    3. Spiral: spirillum (singular); spirilla (plural)
  • Grouping:
    • Pairs: diplo-
    • Chains: strepto-
    • Clusters: staphlo-
Reproduction in Bacteria
  • Asexual Reproduction: Primarily through binary fission, where a parent bacterium divides into two identical cells.
  • Sexual Reproduction: Less common; involves conjugation, where genetic material is exchanged between bacteria.

Beneficial and Harmful Effects of Bacteria

  • Bacteria play both beneficial roles (e.g., in digestion and decomposition) and harmful roles (pathogenic effects).
  • For detailed understanding, refer to pages 343-344 of the source content for examples and the practice questions on page 346.

Summary of Key Points

  1. Both Eubacteria and Archaebacteria are classified as prokaryotes, lacking a membrane-bound nucleus.
  2. Reproduction is mainly asexual by binary fission, with some exceptions for sexual reproduction.
  3. Their rapid reproduction leads to their abundance.
  4. Different modes of nutrition exist between the two kingdoms.
  5. Eubacteria play significant roles in ecological processes such as decomposition, nitrogen fixation, oxygen production, and sometimes act as pathogens.