Prokaryotes Summer 2024 (1)

Probiotics and Antibiotics

  • Probiotics: Beneficial microorganisms that promote gut health and overall wellness.

  • Antibiotics: Medications that inhibit the growth of bacteria or kill bacteria, used to treat infections.

Taxonomy Hierarchy

  • Domain

  • Kingdom

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species

Three Domains of Life

  • Bacteria: Prokaryotic organisms that lack nuclei and membrane-bound organelles.

  • Archaea: Also prokaryotic, includes extremophiles that thrive in extreme conditions.

  • Eukarya: Eukaryotic organisms with true nuclei.

Major Kingdoms under Eukarya Domain

  • Bacteria (Eubacteria): Common bacteria.

  • Archaea (Archaebacteria): Extremophiles living in harsh environments.

  • Protista: Diverse group including protozoa and some algae.

  • Plantae: Multicellular organisms that perform photosynthesis.

  • Animalia: Multicellular organisms that consume organic material.

  • Fungi: Organisms like molds and mushrooms that absorb nutrients.

Characteristics of Archaea

  • Known as extremophiles.

  • Found in extreme environments: salt flats, deep-sea vents, hot springs.

Characteristics of Bacteria

  • Domain: Bacteria

  • Kingdom: Eubacteria

  • Characteristics:

    • Prokaryotic and unicellular.

    • Peptidoglycan in cell wall provides structural support.

    • Mostly heterotrophic with some autotrophs (e.g., cyanobacteria).

Bacterial Morphology

Cell Shapes

  • Cocci: Spherical shapes. Examples:

    • Diplococci: Pairs.

    • Staphylococci: Clusters.

    • Streptococci: Chains.

    • Sarcina: Cubical packets.

  • Bacilli: Rod-shaped bacteria.

  • Spirilli: Spiral-shaped bacteria.

Arrangements

  • Tetrad: Groups of four.

Bacterial Cell Types

  • Gram-positive: Thick peptidoglycan layer retains purple dye during gram staining.

  • Gram-negative: Thinner peptidoglycan layer does not retain dye, appears red.

Gram Staining Process

  • Before staining: Bacteria are colorless.

  • After gram staining:

    • Purple stain indicates gram-positive bacteria.

    • Red stain indicates gram-negative bacteria.

Steps for Gram Staining

  1. Fixation with heat.

  2. Apply crystal violet (purple dye).

  3. Iodine treatment (fixes the dye).

  4. Decolorization step with alcohol.

  5. Counterstain with safranin (red dye).

Cyanobacteria - Features

  • Commonly known as blue-green algae (though they are not true algae).

  • Characteristics:

    • Gram-negative.

    • Autotrophs that perform photosynthesis using phycobilin pigments for the blue-green color.

  • Genera in Lab:

    • Nostoc

    • Oscillatoria

    • Merismopedia

    • Anabaena

Biological Importance of Cyanobacteria

  • Contribute to an oxygen-rich atmosphere.

  • Nitrogen fixation: Convert atmospheric nitrogen (N2) to ammonia (NH3), essential for plant growth.

  • Rapid reproduction can lead to noxious blooms, producing toxins.

  • High protein content.

Nostoc spp.

  • Colony Shape: Filamentous; surrounded by gelatinous sheath, forming large balls of filaments.

  • Cell Types:

    • Vegetative Cells: Round.

    • Heterocysts: Clear, large, round cells used for nitrogen fixation.

Anabaena spp.

  • Colony Shape: Filamentous.

  • Cell Types:

    • Vegetative Cells: Barrel-shaped.

    • Heterocysts: Clear, large, round cells for nitrogen fixation.

    • Akinete: Densely packed, spore-like reproductive cells, larger and oval-shaped.

Symbiotic Relationship #1: Azolla and Anabaena

  • Azolla: Water fern.

  • Anabaena: Cyanobacterium living in the water near roots of the Azolla.

  • Benefits:

    • Cyanobacteria fix nitrogen into a usable form for the plant.

    • Plants make sugars through photosynthesis.

Symbiotic Relationships with Plants

  • Nitrogen is crucial for plant health.

  • Plants cannot utilize atmospheric nitrogen directly; rely on nitrogen-fixing bacteria.

  • Examples observed in lab:

    • Azolla and Anabaena.

    • Root Nodules with Rhizobium.

Symbiotic Relationship #2: Clover and Rhizobium

  • Clover: Plant hosting Rhizobium bacteria.

  • Benefits:

    • Fix N into a usable form for plants.

    • Produce sugars via photosynthesis.

Microscopic View of Gram Staining Procedure

  • Visualize through microscopy after each staining step:

    • Crystal violet application.

    • Iodine treatment.

    • Decolorization with 95% ethyl alcohol.

    • Final staining with safranin.