Wk 6A

Three Domains of Life

  • The classification of life is categorized into three domains:

    • Domain Bacteria

    • Domain Archaea

    • Domain Eukarya

  • Prokaryotic Nature: Both Bacteria and Archaea are characterized as prokaryotes, meaning they lack a membrane-bound nucleus, which is essential to be classified as a eukaryote.

  • Study of Microorganisms:

    • The study of bacteria and archaea has not progressed as swiftly compared to the study of larger organisms like animals and birds.

    • The microscopic size of bacteria and archaea contributes to the slower pace of understanding these microorganisms.

Micrographs and Bacterial Structures

  • Scanning Electron Micrograph:

    • A photograph shows a colored scanning electron micrograph of bacteria.

    • Even when magnified, some features may not be visible to the naked eye but are revealed in the micrograph.

  • Bacterial Shapes:

    • Coccus (singular): Round-shaped bacteria, plural termed cocci. Example: Shown in the photograph.

    • Bacillus (singular): Rod-shaped bacteria, plural termed bacilli. Example: Displayed in the next panel.

  • Potential Dangers of Bacteria:

    • Suggests caution against inhalation of bacteria as they are shown to cover surfaces densely.

Bacterial Reproduction and Structure

  • Reproduction Rate:

    • Bacteria reproduce rapidly, which is an aspect microbiologists consider when studying their structure and wall composition.

  • Gram Staining Methodology:

    • Gram Positive Bacteria:

    • Characterized by having a thick layer of peptidoglycan in their cell wall.

    • Stains purple due to the retention of crystal violet during the Gram staining process.

    • Gram Negative Bacteria:

    • Have a thinner layer of peptidoglycan with an additional lipopolysaccharide layer.

    • Stains pink as most of the crystal violet is washed away during the staining process.

Importance of Cell Wall Structure

  • Influence on Antibiotic Efficacy:

    • The structure of bacterial cell walls plays a crucial role in the effectiveness of antibiotics.

    • Understanding Gram staining helps determine the appropriate antibiotic for treatment.

    • For example:

    • Penicillin effectively targets Gram positive bacteria but is ineffective against Gram negative due to the additional protective layers.

Interaction of Bacteria and Antibiotics

  • Mixed Infections:

    • Significance of identifying whether a bacterial infection involves Gram positive or Gram negative strains to tailor effective antibiotic treatments.

  • Antibiotic Resistance:

    • Certain bacterial strains may develop resistance to antibiotics, creating challenges in treatment:

    • Resistance can arise through various mechanisms, including:

      • Gene Mutations: Allowing the bacteria to pump out antibiotics or produce enzymes to neutralize them.

      • Horizontal Gene Transfer: Rapid gene exchange among bacterial populations can propagate resistance traits.

Prokaryotic Communities and Biofilms

  • Biofilms:

    • Biofilms are communities of microorganisms adhering to surfaces, producing mucus-like polymers.

    • These structures can have both harmful and beneficial roles:

    • Negative Impacts: Pathogenic bacteria in dental plaque can lead to decay and disease.

    • Positive Contributions: Helpful bacteria in sewage treatment processes that detoxify harmful substances.

Overview of Bacterial Species

  • Highlighting various bacterial species:

    • Yersinia pestis:

    • Bacteria found in the throat of infected fleas, causative agent of the plague.

    • Borrelia burgdorferi:

    • Causes Lyme disease, now prevalent in areas like Southern Ontario.

    • Lactobacillus acidophilus:

    • Beneficial bacteria, typically involved in fermentation processes, shown as a bacillus shaped type.

Comparison Between Bacteria and Archaea

  • Bacteria vs. Archaea:

    • Illustrated distinctions between a bacterial cell (left) and an archaeal cell (right).

    • Archaea: Found in extreme environments such as hydrothermal vents and low-oxygen areas, with specific subgroups like methanogens that produce methane in anaerobic conditions.

  • Habitat:

    • Many archaea thrive in low-oxygen environments like swamps and intestines of animals.

Summary and Implications

  • The interaction between prokaryotic organisms shapes their evolutionary paths.

  • The study underscores the importance of understanding microbial structure for medical and environmental applications.