BIOL1102 Week 3(Bacteria and Viruses)

• Bacteria and Archaea are prokaryotes
• Bacteria and Archaea were the first living organisms
• Archaea habitats


  • Hydrothermal vents
  • Ice sheets
  • Soda lakes
  • Volcanic springs
• Prokaryotic cells


  • Size range from 0.5-5μm diameter, with some exceptions like Thiomargarita namibiensis at 750μm
  • Various shapes like cocci, rods, and spirals
  • Capsule - sticky layer of polysaccharides for protection from desiccation
  • Gram positive - thick layer of peptidoglycan
  • Gram negative - thin layer of peptidoglycan and outer membrane of lipopolysaccharides
  • No membrane-bound organelles, specialised membranes perform metabolic functions
  • No true nucleus, single circular chromosome and plasmids
  • Appendages like fimbriae, pili, and flagella for motility at 50μm/sec
  • Endospores for protection from external environment
• Gram stain


  Technique to differentiate between gram positive and gram negative bacteria
• Penicillin


  Antibiotic that inhibits peptidoglycan cross-linking
• Archaea cell membrane


  Phospholipid tails joined as single tail, forming a monolayer
• Bacterial reproduction


  Binary fission
• E. coli can divide every 20 minutes
• There are 2 x 10^10 E. coli per human gut
• E. coli has approximately 4300 genes, so there are 8 million mutations per day per human gut
• Mechanisms of genetic diversity in prokaryotes

  1. Transformation - uptake of foreign DNA

  2. Transduction - phages carrying genes between cells
• E. Coli has approximately 4300 genes
• E. Coli has approximately 8 million mutations per day per human
• Genetic Diversity


  • Transformation - uptake of foreign DNA from surroundings
  • Transduction - phages carry genes from one cell to another
  • Conjugation/Horizontal gene transfer - movement of genes between individuals of different species
• Prokaryotes play a crucial role in the biosphere
• Prokaryotes have both beneficial and harmful impacts on humans
• Diverse nutritional & metabolic adaptations

  • Energy Source: Sunlight = phototroph, Chemical = chemotroph
  • Carbon Source: CO2 etc = autotroph, Organics = heterotroph
  • 4 modes of nutrition
• Photoautotroph


  Cyanobacteria, Photosynthetic, Require sunlight and carbon dioxide
• Chemoautotroph


  Rhizobium, Produce nodules on the roots of plants and exchange nitrogen with the host plant
• Photoheterotroph


  Purple sulphur bacteria, Use sulfur as the electron donor in photosynthesis instead of water
• Chemoheterotroph


  E.coli, Use chemical energy to fix CO2
• Prokaryotic diversity: >10,000 named species, Estimated 2.2-4.3 million species, Estimated 10,000 species in a handful of soil
• Role of Prokaryotes in the Biosphere

  • Decomposers, Convert some molecule forms
  • Cyanobacteria produce atmospheric O2
  • Variety of prokaryotes fix atmospheric N2
  • Rhizobium bacteria increase potassium uptake in seedlings

  
• Gut microbiota


  Involved in development of obesity and related comorbidities
• Dogs have 350 oral bacterial species, Humans have > 600 oral bacterial species, 16.4% shared taxa
• Zoonotic Diseases


  • Anthrax
  • Bubonic plague
  • Q fever
• Capnocytophaga canimorsus


  Emerging cause of sepsis, meningitis, and post-splenectomy infection after dog bites, 26% fatality rate
• Penicillin was discovered in 1928 by Alexander Fleming
• Antibiotic resistance was first observed in Shigella in the 1950s
• Antibiotic resistance


  Ability of bacteria to resist the effects of antibiotics
• Shigella


  • Causes dysentery
  • First observed antibiotic resistance in 1950s
• 1. plasmids


  • Promote resistance to antibiotics
  • Passed on via conjugation
• Bacteriophages


  • Bacteria eaters
  • A virus that infect bacteria

  
• Q fever, also called query fever, is a bacterial infection caused by the bacteria Coxiella burnetii. The bacteria are most commonly found in cattle, sheep, and goats around the world. Humans typically get Q fever when they breathe in dust that was contaminated by infected animals.
• Diphtheria is an acute infectious disease caused by the bacteria Corynebacterium diphtheriae and characterized by severe inflammation of the upper respiratory tract. It is spread through droplets of respiratory secretions expelled by active cases or carriers during speaking or coughing.
• Tetanus is a bacterial infection caused by Clostridium tetani. A toxin released from the bacterium causes severe muscle spasms, especially in the neck and jaw. Tetanus is typically contracted through deep punctures from wounds that are exposed to the bacteria, which is common in soil.
• Salmonella is one of the most common types of food poisoning caused by bacteria. It usually causes stomach cramps and diarrhea that lasts four to seven days. Infection with bacteria that are transferred to the mouth from contaminated food or water are common sources.
• Virus


  • Consists of a nucleic acid surrounded by a protein coat
  • Obligate intracellular parasites

  
• Viral structure


  • Size range: 20nm - 1500nm
  • Genome: Double or single-stranded DNA or Double or Single-stranded RNA
  • Structure: nucleic acid enclosed in protein coat