Bio 101

• Prokaryotes


  Cells lacking a true nucleus and membrane-bound organelles. Simpler structure compared to eukaryotic cells. Include Bacteria and Archaea.
• Eukaryotes


  Cells or organisms that possess a clearly defined nucleus.
• Cell structure of Bacteria


  • Cell wall (made of peptidoglycan)
  • Plasma membrane
  • Cytoplasm
  • Flagella
  • Pili
• Bacteria


  • Broadly divided into Gram-positive and Gram-negative based on reaction to Gram staining
  • Can exist in different shapes like cocci, bacilli, spirilla
  • Cell arrangements like single, pairs, clusters, chains
  • Genetic material is single, circular chromosome with or without plasmid
  • Lack membrane-bound nucleus
• Bacterial reproduction


  1. Binary fission

  2. Genetic diversity (transformation, conjugation, transduction)
• Role of Bacteria in Ecosystems


  • Decomposition and recycling of nutrients
  • Nitrogen fixation and symbiotic relationships with plants
  • Bioremediation and cleanup of pollutants
• Major Differences Between Prokaryotes and Eukaryotes


  • Nucleus
  • Genetic material
  • Organelles
  • Size
  • Complexity
  • Chromosome
  • Replication of DNA
  • Ribosomes
  • Examples
• Cell Wall


  Composed of peptidoglycan, determines Gram-positive or Gram-negative
• Plasma Membrane


  Composed of phospholipid bilayer with selective permeability. Functions include controlling entry/exit of substances and site of energy production
• Cytoplasm


  Composed of water, proteins, ions, organic molecules. Contains ribosomes for protein synthesis
• Nucleoid Region


  Houses the single, circular DNA molecule and may contain plasmids
• Flagella and Pili


  Flagella are for movement and motility, Pili are for adhesion to surfaces and other cells
• Capsule


  Composed of slimy polysaccharides, provides protection against host defenses and facilitates adherence
• Endospores


  Stress-induced survival mechanism, aid in resistance to hostile environments
• Bacterial Shapes and Arrangements


  • Cocci (spherical)
  • Bacilli (rod-shaped)
  • Spirilla (spiral-shaped)
  • Single
  • Pairs
  • Clusters
  • Chains
• Unique Features in Some Bacteria


  • Magnetosomes (magnetic particles for orientation)
  • Gas vesicles (buoyancy control)
  • Phototaxis (movement in response to light)
• Classification of Bacteria Based on Shape


  • Cocci (Streptococcus, Staphylococcus)
  • Bacilli (Escherichia coli, Bacillus subtilis)
  • Spirilla (Spirillum, Helicobacter pylori)
• Classification of Bacteria Based on Oxygen Requirement


  • Aerobic
  • Anaerobic
  • Facultative anaerobes
• Classification of Bacteria Based on Staining Characteristics


  • Gram-positive
  • Gram-negative
• Classification of Bacteria Based on Metabolic Pathways

  • Autotrophic
  • Heterotrophic
• Classification of Bacteria Based on Temperature Requirements

  • Psychrophilic
  • Mesophilic
  • Thermophilic
• Pathogenic and Non-Pathogenic Bacteria

  • Pathogenic (Mycobacterium tuberculosis, Salmonella)
  • Non-pathogenic (Lactobacillus, Bacillus subtilis)
• Nutritional Categories in Bacteria

  • Autotrophic (Photosynthetic, Chemoautotrophic)
  • Heterotrophic (Saprophytes, Parasites, Symbionts)
• Modes of Nutrition in Bacteria

  • Photoautotrophy
  • Chemoautotrophy
  • Photoheterotrophy
  • Chemoheterotrophy
• Metabolic Pathways in Bacteria

  • Glycolysis
  • Krebs Cycle
  • Electron Transport Chain (Aerobic Respiration, Anaerobic Respiration, Fermentation)
• Nitrogen Fixation


  Conversion of atmospheric nitrogen (N2) into ammonia (NH3) by nitrogen-fixing bacteria
• Bacterial Reproduction and Population Growth


  1. Binary Fission

  2. Generation Time

  3. Bacterial Growth Curve (Lag Phase, Logarithmic Phase, Stationary Phase, Death Phase)
• Factors Affecting Bacterial Population Growth


  • Nutrient Availability
  • Temperature
  • pH
  • Oxygen Availability
• Horizontal Gene Transfer in Bacteria


  • Transformation
  • Conjugation
  • Transduction
• Biofilms


  Aggregations of bacteria in a matrix of extracellular polymeric substances, enhancing resistance to antimicrobial agents
• Opportunistic Infection


  Infection caused by microorganisms that typically do not cause disease in healthy individuals, but may become pathogenic when immune defenses are weakened
• Common Opportunistic Bacterial Pathogens


  • Escherichia coli
  • Pseudomonas aeruginosa
  • Staphylococcus aureus
  • Streptococcus pneumoniae
• Factors Contributing to Opportunistic Infections


  • Immune Suppression
  • Breakdown of Barriers
  • Changes in Microbiota
• Prevention and Control of Opportunistic Infections


  • Immunization
  • Infection Control Measures (Hand hygiene, Sterile procedures)
  • Antimicrobial Stewardship
  • Monitoring and Early Detection
• Cell


  Fundamental unit of life, where all life's activities are carried out
• Cell Biology


  Study of cells from basic structures to functions of organelles
• George Emil Palade


  Founding father of cell biology
• Discovery of cells


  First made by Robert Hooke in 1665, later Antonie Van Leewenhoek observed cells and discovered they were living, calling them 'Animalcules'
• Robert Brown


  Scottish Botanist who provided insight into cell structures around 1831
• Types of organisms based on number of cells


  • Unicellular
  • Multicellular