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Probiotics and Antibiotics

• Probiotics: Live bacteria that provide health benefits when consumed.

• Antibiotics: Drugs used to treat bacterial infections by killing or inhibiting the growth of bacteria.

Taxonomy Hierarchy

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Domains of Life

• Bacteria:

  • Prokaryotes that have peptidoglycan in their cell wall.

• Archaea:

  • Prokaryotes that often exist in extreme environments.

• Eukarya:

  • Eukaryotic cells, more complex and include all organisms with a nucleus.

Classification of Life

• Bacteria (Kingdom: Eubacteria)

• Archaea (Kingdom: Archaebacteria)

• Protista

• Plantae

• Animalia

• Fungi

Archaea

• Known as extremophiles.

  • Thrive in extreme environments like salt flats, deep-sea vents, and hot springs.

Bacteria Characteristics

• Domain: Bacteria

• Kingdom: Eubacteria

• Type: Prokaryotic and unicellular

• Cell wall features: Contain peptidoglycan

• Nutrition: Mostly heterotrophic; some are autotrophs (e.g., cyanobacteria).

Bacterial Morphology

• Shapes:

  • Coccus: Spherical shape.

    • Diplococci: Paired cocci.

    • Staphylococci: Clusters of cocci.

    • Streptococci: Chains of cocci.

    • Tetrad: Groups of four cocci.

    • Sarcina: Cubical packets of eight cocci.

  • Bacilli: Rod-shaped.

  • Spirilli: Spiral-shaped.

Bacterial Cell Types

• Gram Positive: Stain appears purple, indicating a thicker peptidoglycan layer.

• Gram Negative: Stain appears red, indicating a thinner peptidoglycan layer and an outer membrane.

Gram Staining Process

• Before staining, bacteria are colorless.

• A gram stain results in either a purple (Gram-positive) or red (Gram-negative) result.

Specifics of Gram Staining

• Crystal Violet: Stains all bacteria.

• Iodine Treatment: Fixes the color.

• Decolorisation: Removes the stain from Gram-negative cells.

• Counterstain with Safranin: Stains Gram-negative cells red.

Cyanobacteria (Blue-Green Algae)

• Characteristics:

  • Gram-negative bacteria.

  • Autotrophs and photosynthetic.

  • Contain phycobilin pigment giving them a blue-green color.

• Genera studied:

  • Nostoc

  • Oscillatoria

  • Merismopedia

  • Anabaena

Biological Importance of Cyanobacteria

• Contribute to an oxygen-rich atmosphere.

• Responsible for nitrogen fixation.

• Rapid reproduction leading to noxious blooms.

• Produce toxins and are nutritious with high protein content.

Nostoc spp.

• Colony Shape: Filamentous, large balls of filaments.

• Cell Types:

  • Vegetative Cells: Round shape.

  • Heterocyst: Clear, large, round; involved in nitrogen fixation.

Anabaena spp.

• Colony Shape: Filamentous.

• Cell Types:

  • Vegetative Cells: Barrel-shaped.

  • Heterocyst: Clear, large, round; aids in nitrogen fixation.

  • Akinete: Densely packed spore-like reproductive cells.

Symbiotic Relationships: Azolla and Anabaena

• Azolla: Water/mosquito fern.

• Anabaena: Cyanobacteria living near roots.

• Mutual Benefits:

  • Anabaena fixes nitrogen into a usable form for Azolla.

  • Azolla provides sugars from photosynthesis.

Oscillatoria spp.

• Colony Shape: Filamentous, protected by mucilaginous sheaths.

• Cell Types:

  • Trichomes: Vegetative cells.

  • Hormogonia: Formed by necrotic discs; asexual reproduction through fragmentation.

Merismopedia spp.

• Colony Shape: Mat-forming, encased in a gelatinous matrix.

• Size: Approximately 20 μm.

Symbiotic Relationships with Plants

• Importance of Nitrogen: Essential for plant growth.

• Plants cannot utilize atmospheric nitrogen (N2) and rely on nitrogen-fixing bacteria (transforming N2 into NH3).

• Example Observations:

  • Symbiotic relationship between Azolla and Anabaena.

  • Symbiotic relationship between Rhizobium and root nodules of clover.

Symbiotic Relationship with Clover and Rhizobium

• Brownish nodules found on clover roots.

• Process:

  • Clover makes sugar via photosynthesis.

  • Rhizobium fixes nitrogen into forms usable by plants.

Microscopic View of Gram Staining Steps

• Crystal Violet: 60 seconds.

• Iodine: 60 seconds.

• Decolorisation with Ethanol: 5-10 seconds.

• Safranin Counterstain: 45 seconds.

• Results: Gram-positive: purple; Gram-negative: red.