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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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Identifying and Classifying Bacteria

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Identifying and classifying bacteria

Identifying and Classifying Bacteria

Ch. 23

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

Identifying and classifying bacteria





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

Identifying and classifying bacteria

  • Photoheterotrophs- uses photosynthesis and eats organic compounds

  • Heterotroph – consumes organic compounds



  • What role do chemosynthetic bacteria have in the ecosystem?


Bacterial reproduction

Bacterial Reproduction

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

What are other ways that antibiotic resistance is passed

What are other ways that antibiotic resistance is passed?

  • Genetic recombination

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