Bacteria

• Prokaryote


  • No nucleus (pro=before)
  • Exist almost everywhere on earth
  • Classified into kingdoms eubacteria or archaebacteria
• Prokaryotic Cell Structure


  • Cell Envelope
  • Capsule
  • Cell membrane
  • Cell wall
  • Pilli (fimbriae)
  • Flagellum
  • Ribosomes
  • Nucleoid region
  • DNA- Plasmid
  • Cytoplasm
  • No nucleus or membrane-bound organelles
• Cell Envelope


  • Capsule and slime layer: protects cell, assists in attaching to other surfaces
  • Cell Wall: Protects, maintains shape of cell
  • Plasma or cell membrane: selectively permeable barrier
  • Pilus (Pilli): assist in attaching to other surfaces, (important for genetic recombination)
  • Fimbriae: shorter pili
  • Flagellum: used for locomotion
• Nucleoid


  • Contains genetic info
  • Double stranded circular chromosome: provide instructions for protein synthesis
  • Plasmids: small double stranded DNA, information for bacterial resistance
• Classification


  • Earliest Classification: Kingdom Monera (Archaebacteria, Cyanobacteria, Eubacteria)
  • Modern Classification: Based on presence of peptidoglycan (complex carb) that prevents bacterial cell walls from rupturing due to changes in osmotic pressure
  • Archaebacteria - no peptidoglycan
  • Eubacteria – have peptidoglycan
• Kingdom Archaebacteria


  • "Ancient Bacteria"
  • Cell wall-lacks PEPTIDOGLYCAN
  • Extreme habitats
  • Anaerobic (absence of oxygen)
  • Autotrophs or heterotrophs
  • DNA sequences are more closely related to Eukarya than Eubacteria
• Phyla of Archaebacteria


  • Halophiles - found only in bodies of concentrated salt water (ex. The Great Salt Lake in Utah and the Dead Sea in the Middle East)
  • Methanogens - produce methane gas (swamp gas). Many species live in the intestines of animals.
  • Thermoacidophiles - found in the hot, acidic waters of sulfur springs. Can handle temperatures near 80°C (186° F), pH=2
• Kingdom Eubacteria


  • "True" Bacteria
  • Most diverse bacterial kingdom
  • Cell walls contain PEPTIDOGLYCAN
• Ways to Classify Bacteria

  • Gram-Staining
  • Shape
  • Modes of Movement
  • Method of obtaining energy
  • "Relationship" with oxygen
  • Method of reproduction
• Gram-Staining


  • Determines the thickness of cell wall and lipid layers
  • Hans Christian Gram, a Danish Microbiologist, developed the Gram-stain technique in 1884
  • Gram staining helps scientists to determine which medicines to use to kill the bacteria
• Gram-Positive Bacteria


  • Will retain the PURPLE DYE
  • Thick layer of peptidoglycan in cell wall
• Gram-Negative Bacteria


  • Will appear PINK/RED
  • Thin Layer of peptidoglycan in cell wall
• Common Eubacteria Shapes


  • Rod - Bacilli
  • Sphere - Cocci
  • Spiral - Spirilla
• Bacterial names


  Often based on their shape
• Types of Movement


  • Flagellum - long whip-like structures to direct the bacterium
  • Layer of slime - bacterium releases slime to slide along and reduce friction
  • Corkscrew rotation - uncoordinated movement, propulsion mechanism, commonly observed in bacilli and spirilla
• Energy


  • Autotrophs: Make the sugar they need to survive from hydrogen & carbon in their environment
  • Photoautotroph: use sunlight
  • Chemoautotroph: make energy from inorganic molecules (Ex: nitrogen fixing bacteria)
  • Heterotrophs: take the sugars they need to survive and reproduce from their environment
• Respiration: "Relationship with Oxygen"

  • Obligate aerobe: Must use oxygen for aerobic respiration
  • Obligate anaerobe: Cannot live in the presence of oxygen. Use fermentation
  • Facultative anaerobes: Can use oxygen when available but does not depend upon it. Switch between aerobic respiration and fermentation
• Binary Fission


  • Asexual reproduction
  • Identical cells are created
  • Lack of genetic variation
  • Large numbers can be made quickly
• Conjugation


  • Sexual reproduction
  • Pilli extension is used to exchange genetic material between 2 cells
  • Promotes genetic variation among cells
• Endospores


  • Tough, dormant cell
  • Resistant to environmental stress (high temperatures, harsh chemicals, drought, etc.)
  • Thick outer coat surrounds the cell's DNA
  • When conditions become favorable, the endospore breaks open and dormant bacteria reproduces
• Endospore-forming bacteria


  • Bacillus anthracis (Anthrax)
  • Clostridium botulinum (Botulism)
  • Clostridium tetani (Tetanus)
• Roles of Bacteria in the Environment

  • Decomposers
  • Nitrogen Fixers
  • Pathogens
• Human Uses of Bacteria

  • Clean up oil spills
  • Production of food: bleu cheese, yogurt, pickles
• Bacteria as Decomposers


  • Saprobes
  • Break down organic matter
  • Recycle nutrients back to the soil
  • May live in the intestines of animals to break down material or may decompose dead plants, fungi, or animals
• Bacteria as Nitrogen Fixers

  • Major role in helping plants convert nitrogen into a useable form – Ammonia
  • Nitrogen Cycle
  • Plants and animals require ammonia for growth and development
• Bacteria as Pathogens


  • Bacteria that cause disease are known as pathogens
  • Release toxins that poison cells = breakdown of tissue
• Bacterial Pathogens


  • Rocky Mountain Spotted Fever – infected ticks
  • Lyme Disease - Borrelia burgdorferi (black-legged ticks)
  • Flesh-Eating Bacteria – Necrotizing fasciitis
  • Gas Gangrene- Clostridium species
• Viruses are not cells, they have no cell membrane or other components of living cells
• Viruses


  • Require a host for reproduction
  • They do not metabolize or respond to stimuli
  • They DO have genetic material and can mutate and evolve
  • They form parasitic relationships with living organisms, virus benefits at the expense of the organism (their host)
• Characteristics of Viruses


  • Very, very small (1/2 -1/100 size of bacteria)
  • Non-Cellular
  • Contain a protein coat – capsid
  • Classified 3 Ways: Host cell, Structure, Life cycle
• Viruses


  • Swine Flu
  • Herpes Simplex B
• Types of Viruses


  • Bacteriophages
  • Animal Viruses
  • Plant Viruses
• Classification of Viruses by Host Cell

  • Avian flu, Ebola virus, influenza, MERS-CoV, rabies, SARS, smallpox, Zika
• Classification of Viruses by Structure

  • Enveloped
  • Non-Enveloped
• Enveloped Viruses


  • Envelope comes from infected cell, or host
  • Least resistant
  • Do not undergo lysis
  • Non-rupturing
• Non-Enveloped Viruses


  • No envelope: capsid and spike proteins
  • Most resistant
  • Undergo lysis
  • Rupturing
  • Devastating to humans
• Viral Structure


  • Inner Core – contains DNA or RNA
  • Outer Core – called capsid
• Naming Viruses


  Often named for the diseases they cause or organ/ tissue they infect
• Virus Names


  • Poliovirus (causes polio)
  • Adenovirus (infects adenoid tissue)
• Viral Replication


  Viruses only do one thing – MAKE MORE OF THEMSELVES (using host cell)