Lecture Notes: Protists, Archaea, and Bacteria

Introduction

Focus on mostly unicellular organisms: protists, archaea, and bacteria.
These organisms make up most of the living things on Earth.
Evolutionary distinction: eukaryotes (protists) vs. prokaryotes (archaea and bacteria).
- "Karyote" refers to nucleus; "pro" means before, indicating prokaryotes lack a nucleus.

Oldest organisms, name suggests ancient (archaic means really old).
First organisms on Earth, adapted to extreme environmental conditions.
Types of extremophiles:
- Thermophiles: thrive in extreme temperatures.
- Halophiles: thrive in high salt concentrations.
- Methanogens: produce methane gas.
Unique cell walls and membranes compared to bacteria and protists.

A diverse group: eukaryotic organisms that aren't plants, fungi, or animals.
Common trait: most live in moist or aquatic environments.
Categories:
- Photosynthesizing protists (related to plants): Algae.
- Non-photosynthesizing protists (related to fungi and animals):
  - Fungus-like and Protozoa (e.g., amoebas).
Evolved diverse methods for nutrition and movement (e.g., cilia, flagella, amoeboid movements).

Found in diverse environments: from surroundings to the human gut.
Can be beneficial or harmful.
General bacterial structure:
- Capsule/Slime Layer: Protective outer layer, capsules can't be washed off.
- Cell Wall: Varies in structure (gram-positive vs. gram-negative).
- Plasma Membrane: Lipid bilayer.
- Flagella: Movement; prokaryotic flagella made of protein flagellin.
- Fimbriae (Pili): May be present; help in attachment.
Internal structure:
- Cytoplasm and Ribosomes: Basic cell structures.
- Nucleoid Area: Contains bacterial chromosome (circular, double-stranded DNA).
- Plasmids: Extra DNA providing genetic advantages.
- Inclusion Bodies: Storage for nutrients due to lack of membrane-bound organelles.

Bacteria use chemotaxis to move towards nutrients and away from toxins.
Protists, archaea, and bacteria show different adaptations and structures based on their evolutionary paths.