Lesson 5 - Eubacteria and Archaeabacteria

Question 1

What are Bacteria?

Answer 1

• Bacteria are prokaryotes → living things without a nucleus, but they do have a single strand of DNA (plasmid)
• Eukaryotic cells have a true nucleus and membrane-bound organelles.
• Bacteria are:
• Single-celled
• Reproduce asexually and sexually
• Live in moist environments
• Bacteria were once classified into one kingdom (Monera), but now scientists have separated them into two distinct kingdoms:
• Archaeabacteria
• Eubacteria

Question 2

Kingdom Archaeabacteria

Answer 2

• “Extremophiles” – live in extreme environments:
• temperatures
• salinity
• pH
• darkness
• In the presence of gases like nitrogen
• All respire/breathe anaerobically (in the absence of oxygen)

Examples:
Methanogens – methane-producing bacteria
Thermophiles – thrive in temperatures in oC up to 110°C
Halophiles – live in very salty water

Question 3

Kingdom Eubacteria

Answer 3

• Organisms we commonly refer to as “bacteria”
  or “true bacteria”
• These organisms need oxygen (they are
  aerobic)
• They are classified by:
• Shape: Cocci, Bacilli, Spirilli
• Cell wall: Structure and reactions to stains (gram +/-)
• Energy Source: N2, CO2, Light

Examples:
Cyanobacteria - A group of bacteria including some that are single cells and some that are chains of cells. You may have seen them as “green slime” in your aquarium or in a pond.

Question 4

Bacterial Shapes

Answer 4

coccus/cocci - Spherical - Cause: Tooth decay
bacillus/bacilli - Rod shaped - Cause: Food poisoning
spirillum/spirilli - Spiral - Cause: Syphillus (sexually transmitted infection)

Question 5

How do Bacteria Reproduce

Answer 5

• Bacteria are unique in many ways.
• One is that they can reproduce both sexually and asexually
• Sexual Production: Conjugation
• a type of sexual reproduction in bacteria whereby one bacterium makes a copy of its genetic info (mobile plasmid) and uses a pilus (pl. pili) to transfer the mobile plasmid to another bacterium. These bacterial cells are not genetically identical.
• Asexual Production: Binary Fission
• A type of asexual reproduction in bacteria whereby one bacterium makes a copy of its plasmid and elongates. When it reaches a maximum size, it will split into 2 new bacterial cells that are genetically identical.