microparasites

• Basic groups of microorganisms include:

  • Bacteria (prokaryote)
  • Fungi, molds, yeast, algae (eukaryotes)
  • Protozoan (parasites)
  • Metazoan (helminths)
  • Virus
• Prokaryotic cells:

  • No nucleus
  • No membrane-bound organelles
  • Cell wall containing peptidoglycan
  • No chromosomes
  • No CHO (and generally lacks sterols essential in cell structure)
• Eukaryotic cells:

  • Has a nucleus
  • Has membrane-bound organelles
  • Contains chromosomes
  • Contains sterols and CHO that serve as receptors
• Characteristics of prokaryotic cells:

  • No nucleus
  • No membrane-bound organelles
  • No chromosomes
  • No CHO (only nucleoid)
  • No sexual reproduction (only bacterial conjugation)
  • No endospore staining
  • No colony characteristics
• Characteristics of eukaryotic cells:

  • Has a nucleus
  • Has membrane-bound organelles
  • Contains chromosomes
  • Has sterols and CHO
  • Has sexual reproduction
  • Has endospore staining
  • Has colony characteristics
• Endospores:

  • A resistant asexual spore that develops inside some bacterial cells
  • Metabolically inactive and highly resistant to various conditions
  • Contains calcium dipicolinate for heat resistance
  • Contains specialized DNA for survival without nutrients
  • Cortex for resistance against UV light and harsh chemicals
  • DNA repair enzymes for damaged DNA during germination
• Cytoplasm/Protoplasm:

  • Protein synthesis, energy production, signal transduction, transportation of metabolites
  • Contains colloidal proteins, enzymes, carbohydrates, ribosomes, and RNA
  • Eukaryotes have cytoplasm external to the nuclear membrane, while prokaryotes have it internal to the cellular membrane
• Structures within the cytoplasm:

  • Nucleoid (bacterial chromosome)
  • Plasmids containing genes for biological functions
  • Ribosomes as microscopic "factories" for protein synthesis
  • Cytoplasmic membrane/plasma membrane for cell protection
• The bacterial plasma (cytoplasmic) membrane is mostly made of fat and protein molecules
• Main functions of the bacterial plasma (cytoplasmic) membrane include:

  • Protecting the inner components of the cell
  • Providing selective permeability through a phospholipid bilayer, allowing nutrients to enter and waste to exit
• Materials move across the bacterial cytoplasmic membrane by:

  • Passive diffusion
  • Active diffusion
  • Cytolysis
• Passive diffusion:

  • Diffusion of substances across a membrane without the use of cellular energy
  • Molecules move from areas of higher concentration to areas of lower concentration
• Facilitated diffusion:

  • Type of passive transport that uses special transport proteins to help substances cross membranes
  • Allows molecules like glucose, sodium ions, and chloride ions to pass through the phospholipid bilayer
• Osmosis:

  • Special case of passive transport where water moves from a hypotonic to a hypertonic solution
  • Direction of water flow is determined by solute concentration
• Active transport:

  • Process of transferring substances into, out of, and between cells using energy, typically ATP
  • Types include antiport pumps, symport pumps, and endocytosis
• Cytolysis:

  • Also known as osmotic lysis, occurs when a cell bursts due to a great influx of water, releasing its contents into the extracellular environment
  • Types include endocytosis and exocytosis
• Functions associated with bacterial cytoplasmic membrane & divisome:

  • Energy production
  • Containing bases of bacterial flagella
  • Waste removal
  • Formation of endospore
• Morphological differences in bacteria:

  • Cocci: spherical, oval, or flattened shapes
  • Bacilli: rod-shaped with various end shapes
  • Spirochetes: spiral forms
  • Pleomorphic: lacking distinct shape
• Bacteria rely on enzymes for their biochemistry, including endoenzymes and exoenzymes

  • Lipolytic bacteria hydrolyze triglycerides using extracellular lipases
  • Saccharolytic bacteria metabolize complex carbohydrates for energy
  • Proteolytic bacteria produce protease enzymes
• Metabolic characteristics of bacteria:

  • Oxygen can form reactive products, enzymes like catalase and peroxidase break down these products
  • Growth characteristics based on oxygen requirements and characteristics
• Different types of microbial growth based on oxygen requirements:

  • Obligate aerobe: can only grow in the presence of oxygen
  • Facultative anaerobe: can grow with or without oxygen
  • Microaerophilic anaerobe: requires low levels of oxygen for growth
  • Aerotolerant anaerobe: can survive in the presence of oxygen but does not use it for growth
  • Obligate anaerobe: cannot survive in the presence of oxygen
• Nutrition sources for microorganisms:

  • Phototrophs: use light as an energy source
  • Chemotrophs: use chemical compounds as an energy source
  • Autotrophs (litotrophs): use inorganic sources like ammonium and sulfide as an energy source
  • Heterotrophs (organotrophs): use organic carbon (lipids, proteins, and carbohydrates) as an energy source
  • Chemoheterotrophs: use chemical and organic compounds like glucose for energy, including medically important bacteria
• Temperature requirements for microbial growth:

  • Psychrophilic (cold-loving): grow below 10°C
  • Mesophilic: grow at 20-40°C, best at 30-40°C
  • Thermophilic (heat-loving): grow at 50-55°C, often found in hot springs associated with volcanic activity
  • Hyperthermophilic: optimum growth at 80°C or more
• Staining characteristics of bacteria:

  • Gram-positive bacteria: retain crystal violet dye, have a thick layer of peptidoglycan in the cell wall
  • Gram-negative bacteria: lose crystal violet dye, have a thin layer of peptidoglycan covered by an outer membrane containing lipopolysaccharides
• Steps in Gram staining:

  1. Bacterial smear preparation: transfer sample to slide, spread evenly, air dry, heat fix

  2. Staining procedures: flood with crystal violet, rinse, flood with mordant, rinse, decolorize, counterstain, rinse, air dry
• Acid-fast stain:

  • Used to identify acid-fast organisms like Mycobacterium and Nocardia
  • Reagents: Carbol fuchsin, phenol, acid alcohol, methylene blue or brilliant cresyl green
  • Procedure: heat fix, flood with carbol fuchsin, steam, rinse, acid alcohol, rinse, counterstain, rinse, air dry