Microbial Biology: Prokaryotes, Archaea, and Bacterial Structures

Can microbes live in lava?

No, it's too hot (1000°F). They can live in volcanic deposits, not lava.

What does "prokaryote" mean?

"Pro" = before, "kary" = nucleus → No true nucleus, no membrane-bound organelles.

Biodiversity fact

Bacteria = 78% of known global biodiversity.

Size of bacteria

0.5-1 μm wide, 1-2 μm long. Red blood cell = 5 μm.

Why do bacteria replicate so fast?

High surface-area-to-volume ratio.

Nucleoid

circular chromosome (DNA)

Plasmids

Small, extra DNA, not required for survival but beneficial

Ribosomes

Protein synthesis

Cytoplasm

Gel matrix holding ribosomes and molecules

RNA types

mRNA (codes), rRNA (ribosome core), tRNA (brings amino acids)

Gram Positive

- Thick peptidoglycan → stains purple.

- "Monoderm."

- Has teichoic acids (immune response, adhesion).

Gram Negative

- Thin peptidoglycan → stains pink.

- "Diderm."

- Outer membrane with LPS (lipopolysaccharides → toxic response).

- Periplasmic space with enzymes & transport proteins.

Glycocalyx (capsule/slime layer)

- Extra polysaccharide coating.

- Protects against drying, predation, antimicrobials.

- Helps with surface attachment & biofilm formation.

Flagellum

motility

Fimbriae

attachment, not motility

Pilus

- only in Gram -

- used in conjugation (DNA transfer)

Conjugation

Pilus forms, plasmid strand transferred

Transformation

Uptake of free DNA from environment

Transduction

Bacteriophages transfer bacterial DNA between hosts

Archaea's similarities to Bacteria

- Size

- Shape

- Lack Nucleus

Archaea's differences to Bacteria

- Cell membranes have ether linkages

- Use phytanyl sidechains (more stable in extreme environments)

- Genes & Enzymes more similar to eukaryotes

Where Archaea Lives

High Salt, hot springs, hydrothermal vents, wetlands, acid mine drainage

what is archaea

prokaryotes that often live in Earth's extreme environments