Kingdoms

Kingdoms: Archaebacteria & Eubacteria

  • Presentation by Annabeth M. Aque at Mindanao State University - Iligan Institute of Technology.

Archaebacteria

Definition

  • Derives from the Greek term "arkhaion" meaning "ancient".

  • Prokaryotic cells without a nucleus or membrane-bound organelles.

  • Belong to the domain Archaea.

  • Represent the oldest organisms on Earth.

Discovery

  • First identified by Carl Woese and George Fox in 1977.

  • Morphologically similar to bacteria but genetically distinct from both bacteria and eukaryotes.

Structures and Functions

  • Functions and genetic structures of archaebacteria are more similar to eukaryotes than to eubacteria.

  • Can survive in extreme environments such as high salinity, acidity, or temperature.

  • Example: Methanobrevibacter oralis is found in the human microbiome.

Types of Archaebacteria

Methanogens

  • Thrive in oxygen-free environments and produce methane gas.

  • Locations include marshes, lake sediments, and digestive tracts of animals.

  • Commercial uses in sewage breakdown.

Halophiles

  • Adapted to high salt concentrations.

  • Found in places like the Great Salt Lake and the Dead Sea.

  • Example: Halobacterium salinarum.

Thermophiles

  • Live in extremely hot conditions such as acidic sulfur springs or ocean cracks.

  • Example: Pyrolobus fumarii, thrives at 113°C (235°F).

  • Capable of surviving temperatures higher than boiling water due to extreme pressure.

Eubacteria

Definition

  • Known as "true bacteria" or simply "bacteria".

  • Ubiquitous prokaryotic cells found in diverse habitats, including human bodies.

  • Essential roles in human health, ecosystems, antibiotic production, and food fermentation.

  • Did you know? More bacteria reside in the human mouth than there are people on Earth.

Microbial Communities in Food Systems

  • Diverse communities of fungi, bacteria, and protozoa are fundamental to food system health and functioning.

  • Can cause diseases in plants, animals, and humans under favorable conditions.

  • Aquatic animals have microbiomes that assist in nutrient absorption from food.

Bacterial Morphology

Shapes of Bacteria

  • Cocci: spherical shaped.

  • Bacilli: rod shaped.

  • Spirilla: spiral shaped.

Gram Staining

  • Gram-positive bacteria stain purple due to thick peptidoglycan cell walls (e.g., cyanobacteria).

  • Gram-negative bacteria stain pink due to a thin cell wall and outer membrane (e.g., Salmonella).

Types of Eubacteria

Based on Energy Acquisition

  • Heterotrophs: Consume other organisms.

  • Autotrophs: Produce their own food.

Autotrophic Bacteria

  • Example: Cyanobacteria - blue-green algae that photosynthesize.

Heterotrophic Bacteria

  • Free-living consumers: E.g., Azobacter (nitrogen fixation), E. coli (collaborates with humans for vitamin K production).

  • Parasitic bacteria: Require a host for survival (e.g., Impetigo).

  • Decomposers: Help recycle nutrients (e.g., Pseudomonas in soil).

Bacterial Shapes and Their Examples

  • Sphere-shaped: Staphylococcus aureus, Streptococcus pyogenes.

  • Rod-shaped: Mycobacterium tuberculosis, Bacillus anthracis.

  • Spiral-shaped: Vibrio cholerae, Helicobacter pylori.