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Identifying and Classifying Bacteria. Ch. 23 . What is a prokaryote?. Cells that lack a true nucleus . Cells that lack membrane-bound organelles . Most surrounded by a cell wall. Many secrete a protective slime capsule . How big is a prokaryotic cell?. 1- 5 micrometers

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what is a prokaryote
What is a prokaryote?
  • Cells that lack a true nucleus.
  • Cells that lack membrane-bound organelles.
  • Most surrounded by a cell wall.
  • Many secrete a protective slime capsule.
how big is a prokaryotic cell
How big is a prokaryotic cell?
  • 1- 5 micrometers
  • (1 millionth of a meter)
  • Archaebacteria vs Eubacteria
  • Surrounded by a cell wall lacking peptidoglycan.
  • Live in extreme conditions
examples of archae
Examples of Archae
  • Methanogens: convert H2 and CO2 into methane gas for energy
  • Halophiles: love salt
  • Thermoacidophiles: love heat and acid
  • Surrounded by a cell wall made of peptidoglycan.
  • Example: rhizobium- nitrogen–fixing bacteria
identifying prokaryotes
Identifying Prokaryotes

1. Shape:

  • Coccus – spherical
  • Bacillus – rod-shaped
  • Spirillum – spiral
  • Vibrio – comma shape




cocci and bacilli may group together
Cocci and Bacilli may group together

Prefixes for arrangements:

Diplo – two

Ex. Diplococcus

strepto chain
Strepto – chain



staphylo clustered
Staphylo - clustered


2 motility ability to move
2. Motility: ability to move
  • Flagella: whip-like structure used to propel bacteria
  • Slime: glide along slime secretion
  • Spiral motion: cork-screw motion (spirillum)
3 metabolism oxygen or not
3. Metabolism: Oxygen or NOT
  • Obligate Aerobes: Need oxygen
  • Obligate Anaerobes: cannot live in oxygen
  • Facultative anaerobes: can live with or without oxygen
3 metabolism obtaining energy
3.Metabolism: Obtaining Energy

Autotroph vs. Heterotroph

  • Photoautotroph- uses light energy for photosynthesis
  • Chemoautotroph- uses energy from inorganic chemicals for chemosynthesis
Photoheterotrophs- uses photosynthesis and eats organic compounds
  • Heterotroph – consumes organic compounds
  • What role do chemosynthetic bacteria have in the ecosystem?
asexual binary fission
Asexual: Binary fission
  • Circular DNA replicates
  • Cell membrane and cell wall divide
  • Identical daughter cells separate
how fast does this happen
How fast does this happen?
  • approximately every 20 minutes
genetic recombination
Genetic recombination

Sharing or exchanging of genetic material

3 types:

  • Conjugation
  • Transformation
  • Transduction
1 conjugation
1. Conjugation
  • A temporary bridge forms between two cells.
  • A plasmid, a separate section of DNA, is transferred from one cell to the other.
  • Often the plasmid contains useful genes, like antibiotic resistance.
2 transformation
2. Transformation
  • Bacteria takes in DNA from the environment.
  • Dead bacteria may break apart and release DNA.
  • Other bacteria can pick up this DNA and become genetically different.
3 transduction
3. Transduction
  • Viruses can pick up small amounts of DNA from a host bacteria.
  • When it infects another bacteria, the new DNA is transferred into that cell.
  • Pathology is the study of disease.
  • Pathogens: organisms that cause disease.
gram staining test
Gram-staining Test
  • Gram-positive: bacteria contain lots of peptidoglycan in cell walls. Stains purple.
  • Gram- negative: bacteria contain little peptidoglycan in cell walls. Stains red.
  • Poisonous proteins that are released by some gram-positive bacteria.
for example
For example
  • Clostridium tetani secretes an exotoxin that causes tetanus.
    • Tetanus causes stiffness in muscles.
  • Clostridium botulinumproduces a very powerful exotoxin that causes the fatal disease, botulism.
  • 1 g of botulism toxin can kill 1 million people.
  • Lipids and carbohydrates in the cell membranes of some Gram-negative bacteria, that are poisonous.
  • They are released when the bacteria die.
for example1
For example:
  • Most species of Salmonella, are endotoxin producing bacteria.
  • Salmonellatyphi, causes typhoid fever.
  • Antibiotics interfere with the bacteria’s cellular activities.
for example2
For example:
  • Penicillin: blocks the building of the cell wall.

“Accidently” discovered by Alexander Fleming in 1920s

  • Tetracyline: blocks protein synthesis.
where do antibiotics come from
Where do antibiotics come from?
  • Antibiotics are naturally made by some fungi and bacteria.
  • Some are made synthetically in labs.
  • But most used in treatment still come from bacteria.
antibiotic resistance
  • Bacteria can quickly adapt to their environment because of their rapid rate of reproduction.
antibiotic resistance1
  • If one bacterium mutates and becomes resistant,
  • then in the presence of antibiotics, bacteria not resistant die
  • Those with the resistance take over the population.
which diseases are preventable by better sanitation practice
Which diseases are preventable by better sanitation practice?
  • Cholera
  • Salmonella
  • Tetanus
  • Staph