TAXONOMY

• The traditional Whittaker system of classification divides living organisms into five kingdoms: Plantae, Animalia, Fungi, Protista, and Monera, further divided into phyla, classes, orders, families, genera, and species

  
• Carl von Linné (Linnaeus) laid down the basic rules for classification and established taxonomic categories or taxa
• Robert Whittaker's classification system is based on structural similarities and differences, such as prokaryotic and eukaryotic cellular organization and nutrition methods
• Carl R. Woese devised a Three-Domain System of Classification, including Archaea, Bacteria, and Eukarya
• The International Code of Nomenclature of Bacteria provides the accepted labels by which organisms are universally recognized
• In the binomial system of nomenclature, every organism is assigned a genus and a species of Latin or Greek derivation
• Genotypic characteristics relate to an organism's genetic makeup, while phenotypic characteristics are based on features beyond the genetic level
• Prokaryotic cells typically range from 0.4 to 2 micrometers in diameter, while eukaryotic cells are larger, ranging from 10 to 100 micrometers in diameter
• Prokaryotic cells lack a classic membrane-bound nucleus, while eukaryotic cells have a nucleus with a nuclear membrane
• Prokaryotic cells have a circular chromosomal DNA, while eukaryotic cells have linear DNA complexed with histones and other proteins
• Flagella in bacteria can have different arrangements, such as simple flagella composed of flagellin or complex cilia composed of microtubules and tubulin polymers
• The traditional Whittaker system of classification divides organisms into five kingdoms: Plantae, Animalia, Fungi, Protista, and Monera, further divided into phyla, classes, orders, families, genera, and species

  
• The Ziehl–Neelsen stain is a differential staining technique used to differentiate between acid-fast and non-acid-fast bacteria

  
• The Ziehl–Neelsen stain involves several steps:

  • Primary staining with Carbol Fuchsin
  • Mordanting with heat
  • Decolorization with Acid Alcohol
  • Counterstaining with Methylene Blue
• Gram-positive cell walls have a thick peptidoglycan layer, while Gram-negative cell walls have a thin layer of peptidoglycan in the periplasmic space within its inner and outer lipid membranes
• Gram-positive cell walls appear purple after staining, while Gram-negative cell walls appear pink or red
• Mycobacteria, like Mycobacterium tuberculosis, have a distinctly acid-fast cell wall due to a waxy layer of glycolipids and fatty acids
• Steps in the Ziehl–Neelsen stain:

  • Primary/Initial Staining: Carbol Fuchsin for 5 minutes (rinse) - results in red color for acid-fast bacteria
  • Mordanting: Tergitol - results in red color for acid-fast bacteria
  • Decolorization: Acid Alcohol for 2 minutes (rinse) - results in colorless for non-acid-fast bacteria
  • Counterstaining: Methylene Blue for 1-3 minutes (rinse) - results in blue color
• Internal parts of the bacterial cell wall include:

  • Cytoplasmic/Plasma Membrane: site of energy production, separates intracellular components, osmotic barrier, houses enzymes
  • Mesosomes: folds along the membrane for chromosome attachment
  • Free Ribosomes: sites of protein synthesis
  • Inclusion Bodies: storage deposits for nutrients
  • Bacterial Spores/Endospores: resting stage for bacteria in unfavorable conditions
• Types of flagella arrangements in bacteria:

  • Peritrichous: flagella around the bacterium
  • Amphitrichous: single flagella at both ends
  • Lophotrichous: multiple flagella at one end
  • Monotrichous: single flagella at one end
• Glycocalyx in bacteria:

  • Exterior high molecular weight structure made of polysaccharides or polypeptides
  • Two forms: Capsule (firmly attached, virulence factor) and Slime Layer (loose, protective or adhesive)