LEARNING OBJECTIVES

• Prokaryotes


  Single-celled microorganisms that lack a true nucleus and other membrane-bound organelles.
• Binary Fission


  A type of cell division in prokaryotes where the parent cell divides into two identical daughter cells.
• DNA Structure


  Eukaryotes have multiple linear chromosomes, while Prokaryotes have a single circular chromosome.
• Cytoskeleton


  Eukaryotes have a complex cytoskeleton with microtubules, microfilaments, and intermediate filaments, while Prokaryotes lack a cytoskeleton.
• Bacterial Cell Wall


  Composed of peptidoglycan, a mesh-like structure providing structural support and shape to the cell.
• Peptidoglycan Layer (Bacterial Cell Wall)


  Composed of sugar molecules (NAM and NAG), peptidoglycan bonds, and cross-linking peptides, providing structural support to the bacterial cell wall.
• Plasma Membrane


  A semi-permeable layer composed of a phospholipid bilayer, cholesterol, proteins (receptors, channels, and transporters), and glycoproteins and glycolipids, regulating cell structure and function.
• Nucleoid


  A region in bacterial cells containing the chromosome, composed of DNA, histone-like proteins, nucleoid-associated proteins, and nucleoid-intrinsic proteins, regulating gene expression and structural organization.
• Flagella


  A whip-like structure used by bacteria for motility, composed of flagellin, flagellar basal body, filamentous flagellum, hook, and C-ring, regulating bacterial movement and motility.
• Pili (Fimbriae)


  A thin, whip-like structure protruding from bacteria, composed of pilus tip proteins, MreB core, pilus shaft, pilus tip domain, and pilus-receptor interaction, regulating bacterial adhesion, attachment, and colonization.
• Capsule


  A protective shell surrounding bacteria, composed of capsular polysaccharide (K-polymers), K-deficiency incapsulare (K-DIC) proteins, glycosyltransferases, flippases, and structural motifs, regulating antimicrobial defense and bacterial adhesion.
• Endospores


  A highly resistant, dormant structure formed by certain bacteria, composed of asporogenic cell wall, cortex, exosporium, core and core-rib, and dipicolinic acid (DPA), allowing them to survive extreme conditions and ensure bacterial survival.
• Gram Stain


  A staining technique used to Identify bacterial species, based on their cell wall composition, employing Biebrich Scarlet Granules, iodine treatment, and counterstaining, distinguishing Gram-positive and Gram-negative bacteria.
• Gram Stain


  A staining technique used to Identify bacterial species, based on cell wall composition, classifying bacteria into Gram-positive and Gram-negative categories, essential in diagnostic microbiology for understanding pathogenesis, virulence, and antibiotic susceptibility.
• Gram Stain Process


  A multi-step staining technique used to classify bacteria as Gram-positive or Gram-negative, involving fixation, decolorization, staining, counterstaining, fixation and dehydration, and microscopy, allowing for bacterial species identification and classification.
• Bacterial Morphologies


  A variety of bacterial shapes, including rod-shaped, coccus-shaped, spiral-shaped, flagellated bacteria, filamentous bacteria, and coccobacillus-shaped bacteria, each with unique characteristics, essential for identifying bacterial species and understanding associated diseases.
• Bacteria


  Found almost everywhere on Earth, essential for the existence of all life on the planet, play crucial roles in decomposition, nutrient cycling and ecosystem balancing
• Cocci


  A type of bacterial shape, appears as small spheres or ovals, examples include Staphylococcus, Streptococcus and Enterococcus
• Bacilli


  A type of bacterial shape, appears as rod-shaped, examples include Escherichia, Pseudomonas and Bacillus
• Diverse Morphologies


  Bacteria exhibit a wide range of shapes and forms, examples include spherical (Cocci), rod-shaped (Bacilli), spiral (Spirilla) and branched (Actinomycetes)
• Bacterial Cell Size


  Typical size: 0.5-5.0 µm, range: 0.1-100 µm, examples include E. coli, Mycobacterium tuberculosis and Thermus aquaticus
• Bacterial Cell Structure (SEM)

  Cell Wall: outermost layer composed of Peptidoglycan, Teichoic acids and Lipoarabinomannan; Peptidoglycan layer confers shape and provides structural support; Cytoplasm contains water, solutes and ribosomes; Membranes include Inner membrane and Outer membrane with lipopolysaccharides
• Prokaryotes


  Definition: lack a true nucleus and membrane-bound organelles, characterized by simple cell structure, no membrane-bound organelles, DNA is not separated from the cytoplasm by a nuclear membrane, reproduce by binary fission, examples include bacteria and Archaea
• Comparison of Bacterial and Animal Cell Structure

  Bacterial cells have a cell wall, cytoplasm, and membranes, whereas animal cells do not have a cell wall, have a more complex cytoplasm with organelles, and multiple membranes including the plasma membrane and nuclear envelope
• Prokaryotic Cell Structure


  Prokaryotic cells have a cell wall, cytoplasm and membranes, with DNA arranged as a circular chromosome not separated from the cytoplasm by a nuclear membrane
• Prokaryotic Cell Characteristics


  Prokaryotic cells lack a true nucleus, have no membrane-bound organelles and have a single circular chromosome
• Cytoplasm


  Cytoplasm is a gel-like substance in cells, made up of water and solutes, containing diverse macromolecules and ribosomes, with functions in transportation, storage and cellular metabolism
• Plasmids


  Plasmids are small, circular DNA molecules that replicate independently of the bacterial chromosome, can exist in multiple copies, and can be used as vectors in molecular biology applications
• Types of Plasmids


  Plasmids can be categorized based on their size, with examples including:
• Ribosomes


  Ribosomes are the site of protein synthesis in the cytoplasm, where RNA-directed translation of messenger RNA sequence adds amino acids to a growing chain
• Ribosomal Subunits


  Ribosomes are composed of two subunits, one large and one small, which interact to form a complete ribosome
• Bacterial Envelope


  The bacterial envelope is composed of a thick peptidoglycan layer, a thin outer layer, and a permeable outer membrane, providing structural support and regulating osmotic balance
• Gram Negative


  Gram-negative bacteria have a distinct cell wall composition, with a thin peptidoglycan layer and a thick outer layer of lipopolysaccharides, and do not retain the Gram stain
• Peptidoglycan Layer


  The peptidoglycan layer is composed of a polysaccharide made up of repeating units of N-acetylglucosamine and N-acetylmuramic acid, cross-linked by short peptides
• Gram Negative vs Gram Positive

  Gram-negative bacteria, like E. coli, have a different cell wall composition and are stained pink by Gram stain, whereas Gram-positive bacteria, like S. aureus, have a thicker peptidoglycan layer and are stained purple
• Gram Positive


  Gram-positive bacteria have a characteristic cell wall composition, with a thick peptidoglycan layer and lack of an outer membrane, and retain the Gram stain
• Cytoplasmic Membrane


  The cytoplasmic membrane is a thin, selectively permeable layer that surrounds the cytoplasm, allowing for the regulation of molecule and ion movement, and participating in cell signaling and maintaining the cell's electrical potential
• Phospholipid Bilayer


  The phospholipid bilayer is the main component of the cytoplasmic membrane, composed of phospholipids with their polar heads facing outwards and non-polar tails facing inwards
• Membrane-Associated Proteins


  Membrane-associated proteins interact with the cytoplasmic membrane, participating in cell signaling, transport, and cell adhesion, and include integral, peripheral, and lipid-anchored proteins
• Membrane Proteins


  Membrane proteins can be integral, peripheral, or lipid-anchored, and participate in various cellular processes, including cell signaling and transport