🦠 Bacteria & Archaea

• Antibiotic Resistance

Occurs when bacteria evolve mechanisms to survive exposure to antibiotics, often via gene transfer and selection.

• Natural Selection & Resistance

Antibiotic use selects for resistant strains, increasing their frequency in populations.

• Binary Fission

A form of vertical gene transfer where prokaryotes replicate DNA and divide into identical cells.

• Budding

Vertical gene transfer where a new organism grows from the body of the parent.

• Horizontal Gene Transfer

Movement of genetic material between organisms via transformation, transduction, or conjugation.

• Transformation

Uptake of free DNA from the environment by a prokaryote.

• Transduction

Transfer of DNA between bacteria via bacteriophages.

• Conjugation

Direct transfer of DNA between bacteria using a pilus; F+ cells donate plasmids to F- cells.

• F+ vs F- Cell

F+ cells contain the fertility plasmid and can initiate conjugation; F- cells lack it.

• Genetic Variation in Prokaryotes

Achieved through horizontal gene transfer, mutations, and plasmid exchange.

• Acquired Genes

Can confer antibiotic resistance, virulence factors, or new metabolic capabilities.

• Metabolic Diversity via Gene Transfer

Allows adaptation to diverse habitats and ecological niches.

• Habitat Diversity

Includes acidophiles, halophiles, mesophiles, psychrophiles, and thermophiles.

• Lateral Gene Flow

Another term for horizontal gene transfer.

• Vertical Gene Flow

Transmission of genetic material from parent to offspring.

• Photoautotrophs

Use light energy to synthesize organic compounds from CO₂.

• Chemoorganotrophs

Obtain energy from organic molecules.

• Chemolithotrophs

Use inorganic molecules for energy.

• Methanogens

Produce methane as a metabolic byproduct in anaerobic conditions.

• Methanotrophs

Consume methane as their energy source.

• Acidophile

Thrives in acidic environments.

• Halophile

Thrives in high-salt environments.

• Mesophile

Prefers moderate temperatures.

• Psychrophile

Thrives in cold environments.

• Thermophile

Thrives in high-temperature environments.

• Anabaena

A genus of cyanobacteria with nitrogen-fixing heterocysts.

• Heterocyst

Specialized nitrogen-fixing cell in cyanobacteria.

- Prokaryote vs Eukaryote

Prokaryotes lack membrane-bound organelles and a nucleus; eukaryotes have both.

- Morphological Differences

Prokaryotes are typically smaller, lack compartmentalization, and have simpler structures.

- Molecular Differences

Prokaryotes have circular DNA and 70S ribosomes; eukaryotes have linear DNA and 80S ribosomes.

- Role of Natural Selection

Antibiotic use selects for resistant strains, increasing their frequency in populations.

- Binary Fission

A form of vertical gene transfer where prokaryotes replicate DNA and divide into identical cells.

- Budding

Vertical gene transfer where a new organism grows from the body of the parent.

- Vertical Gene Transfer

Transmission of genetic material from parent to offspring.

- Horizontal Gene Transfer

Movement of genetic material between organisms via transformation, transduction, or conjugation.

- Transformation

Uptake of free DNA from the environment by a prokaryote.

- Transduction

Transfer of DNA between bacteria via bacteriophages.

- Conjugation

Direct transfer of DNA between bacteria using a pilus; F+ cells donate plasmids to F- cells.

- F+ vs F- Cell

F+ cells contain the fertility plasmid and can initiate conjugation; F- cells lack it.

- Genetic Variation in Prokaryotes

Achieved through horizontal gene transfer, mutations, and plasmid exchange.

- Acquired Genes

Can confer antibiotic resistance, virulence factors, or new metabolic capabilities.

- Virulence via Gene Transfer

Genes may encode toxins or adhesion factors that increase pathogenicity.

- Resistance via Gene Transfer

Genes may encode enzymes that degrade antibiotics or alter target sites.

- Metabolic Function via Gene Transfer

Genes may enable use of new substrates or survival in extreme environments.

- Comparison to Eukaryotic gene transfer

Eukaryotes use sexual reproduction and meiosis for genetic variation; prokaryotes rely on gene transfer and mutation.