Identifying and classifying bacteria
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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