Lab 4 - Prokaryotes and Species Diversity - Tagged

Prokaryotic Overview

• Transition from simple prokaryotic lifestyles to complex eukaryotic forms.

• Evidence indicates Archaea and Eukarya are closer relatives than either is to Bacteria.

Characteristics of Prokaryotes

• Size: Much smaller than Eukaryotes; prokaryotic cells are typically 1-5 µm in diameter compared to eukaryotic cells at 10-100 µm.

• Habitat: Many prokaryotes, especially Archaea, thrive in extreme environments (extremophiles).

• Metabolism: Diverse methods for acquiring carbon and energy.

• Structure: Unicellular, minimal specialization, referred to as generalists.

• Complexity: Although they are simpler than eukaryotes, prokaryotes can exhibit significant biological complexity.

Distinctions Between Bacteria and Archaea

• Bacteria:

  • Possess peptidoglycan in their cell walls.

  • Exhibit various photosynthesis capabilities, though primarily absent.

• Archaea:

  • Have pseudopeptidoglycan or alternative polymers (polysaccharides, glycoproteins).

  • Have free mycolic acids, differ chemically in cell wall composition.

Gram-Staining of Bacteria

• Essential method for visual identification of bacteria based on cell wall structure.

• Gram-Negative:

  • Thin peptidoglycan layer, surrounded by a lipid bilayer.

  • Stains pink, as the stain does not penetrate well.

• Gram-Positive:

  • Thick peptidoglycan layer, which retains the stain.

  • Stains purple due to interaction with peptidoglycan.

Morphological Diversity Among Bacteria and Archaea

• Shapes:

  • Coccus (spherical), Bacillus (rod-shaped), Spiral (e.g., Spirillum).

• Clinical Examples:

  • Staphylococcus: Staph infections.

  • Bacillus cereus: Food poisoning.

  • Spirillum: Associated with peptic ulcers.

Study of Bacteria and Archaea

• Microscopy:

  • Uses direct light, includes compound microscopes with various lenses (10x ocular, 4x-100x objective).

  • Total magnification ranges typically from 40x to 1000x.

• Culturing:

  • Growth of cells in media; observations made from growth in broth or on solid agar plates.

  • Understanding of colony morphology important for identification.

Importance of Scale in Microbiology

• Essential to note magnifications when documenting observations in drawings or photographs.

Colony Morphology

• Characteristics like shape, size, and color are species-specific and stable unless affected by environmental changes or mutations.

• Useful for microbial identification.

Species Diversity Concepts

• Species: An evolutionarily independent monophyletic group.

• Diversity: Refers to the number of different populations within a specific area.

• Species Diversity: Measures both the number of species and the evenness in their abundances, affecting energy flow and productivity in ecosystems.

High vs. Low Species Diversity

• High Diversity:

  • Community with many species (richness) and approximately equal abundance (evenness).

  • Examples: Tropical rainforests, coral reefsv.

• Low Diversity:

  • Few species or unequal abundance among many species.

  • Examples: Deserts, arctic tundra, salt marshes.

Evenness in Communities

• Comparison of community compositions:

  • Community 1: Even distribution (e.g., 25% each species).

  • Community 2: Uneven distribution (e.g., 80%, 5%, 5%, 10%).

Diversity Indices

• Shannon Index (H’): A mathematical formula to quantify diversity, representing both species richness and evenness.

• Calculation: H΄ = -Σ (pi ln pi)

  • Where pi = proportion of individuals of a species relative to total individuals.

• Maximum Diversity (Hmax):

  • Hmax = ln(S), where S is the number of species.

• Evenness (J):

  • J = H’/Hmax, indicating distribution across species.

Implications of Diversity

• Results in complex ecological interactions:

  • Increases in predation, competition, and parasitism levels.

  • Enhances productivity within communities.

Calculation of Diversity (Example Tables)

• Importance of systematic data recording for species, morphology, and abundance during observations.

• Inclusion of attributes like margin, colony morphology, and size aids in understanding biodiversity.

• Practice in calculations for indices helps in quantifying diversity using actual data from colonies.