lesson two
Topics:
1. Archaebacteria vs. Eubacteria
2. Structure & Composition
3. Reproduction
ARCHAEBACTERIA VS. EUBACTERIA
Bacteria can be classified into two kingdoms: Archaebacteria and Eubacteria. Bacteria in both of these kingdoms have similarities and differences. Let’s explore the similarities first!
Similarities
· They are unicellular and can stick together in colonies
· They have rigid outer walls and a plasma membrane
· Cells are prokaryotic so bacteria typically lack membrane-bound structures unlike plant and animal cells that are eukaryotic
· A plasmid (a single chromosome DNA loop) is the genetic material that floats freely inside the cell
· Reproduction is asexual therefore occurs through binary fission
· Bacteria live in moist environments and typically become inactive in dry environments
Archaebacteria
Archaebacteria (meaning early or primitive) derived from the first living organisms on Earth. They can tolerate extreme conditions unlike other organisms, including living without oxygen. The three major groups found in this kingdom are:
a) Thermophiles- they live in extremely hot environments such as hot springs by obtaining energy through the oxidization of sulfur
b) Methanogens- they live in environments such swamps and the intestines of humans by growing on carbon dioxide and hydrogen to produce methane
c) Halophiles- they live in extremely saline environments such as salt lakes and produce the purple-red colour in those areas
Eubacteria
Eubacteria comprises of organisms that are 0.4 micrometers to several micrometers in length. The most well known organism in the kingdom Eubacteria is Escheria coli or, E. coli. This organisms can be both harmful and helpful to humans. Many live in the human intestine aiding in food digestion and synthesis of vitamin K and B. On the other hand, increased numbers of the bacteria in water shows contamination and is dangerous to human health.
The gram staining method developed by Hans Christian Gram in 1884 can be used to classify bacteria according to its cell composition and cell-wall types. Bacteria samples are smeared on a slide, stained with violet dye and fixed with Gram’s iodine. Gram-positive bacteria appear purple in the microscope whereas gram-negative bacteria appear pinkish-red. The amount of peptidoglycan determines the colour of these walls; the more peptidoglycan the more purple they appear.
Eubacteria can also be classified according to shape, configuration, respiration and nutrition. Most organisms are either spherical, rod, or spiral in shape. After division, bacteria group together and form either cocci, bacilli, spirillia, pairs, clumps or chain configurations. Large numbers of cells are referred to as colonies. Some bacteria require oxygen so they are aerobic (ex: bacteria causing tuberculosis) whereas those that don’t are called anaerobic (ex: bacteria causing tetanus). (See picture below!)
Click here for an activity on bacteria classification!
Growth & Reproduction
Bacteria reproduce via binary fission, a process that looks a bit like mitosis but is simpler. A single strand of DNA replicates and transfers all its genetic material to each new cell. After replication, the bacteria divides into two identical bacteria which can either remain attached or separate.
Click here to see an animation!
Even though sexual reproduction is not common, conjugation occurs in some bacteria. During this process the donor and recipient make cell-to-cell contact through a sex pilus which allows the transfer of plasmids. This gives the recipient altered characteristics. The bacteria then separate.
Click here to see an animation!
If environmental conditions are harsh, some bacteria survive by forming endospores, dormant cells. They are resistant to extreme conditions and when normal conditions return, they sprout and an active bacterium emerges.
Click here to see an animation!
1. Archaebacteria vs. Eubacteria
2. Structure & Composition
3. Reproduction
ARCHAEBACTERIA VS. EUBACTERIA
Bacteria can be classified into two kingdoms: Archaebacteria and Eubacteria. Bacteria in both of these kingdoms have similarities and differences. Let’s explore the similarities first!
Similarities
· They are unicellular and can stick together in colonies
· They have rigid outer walls and a plasma membrane
· Cells are prokaryotic so bacteria typically lack membrane-bound structures unlike plant and animal cells that are eukaryotic
· A plasmid (a single chromosome DNA loop) is the genetic material that floats freely inside the cell
· Reproduction is asexual therefore occurs through binary fission
· Bacteria live in moist environments and typically become inactive in dry environments
Archaebacteria
Archaebacteria (meaning early or primitive) derived from the first living organisms on Earth. They can tolerate extreme conditions unlike other organisms, including living without oxygen. The three major groups found in this kingdom are:
a) Thermophiles- they live in extremely hot environments such as hot springs by obtaining energy through the oxidization of sulfur
b) Methanogens- they live in environments such swamps and the intestines of humans by growing on carbon dioxide and hydrogen to produce methane
c) Halophiles- they live in extremely saline environments such as salt lakes and produce the purple-red colour in those areas
Eubacteria
Eubacteria comprises of organisms that are 0.4 micrometers to several micrometers in length. The most well known organism in the kingdom Eubacteria is Escheria coli or, E. coli. This organisms can be both harmful and helpful to humans. Many live in the human intestine aiding in food digestion and synthesis of vitamin K and B. On the other hand, increased numbers of the bacteria in water shows contamination and is dangerous to human health.
The gram staining method developed by Hans Christian Gram in 1884 can be used to classify bacteria according to its cell composition and cell-wall types. Bacteria samples are smeared on a slide, stained with violet dye and fixed with Gram’s iodine. Gram-positive bacteria appear purple in the microscope whereas gram-negative bacteria appear pinkish-red. The amount of peptidoglycan determines the colour of these walls; the more peptidoglycan the more purple they appear.
Eubacteria can also be classified according to shape, configuration, respiration and nutrition. Most organisms are either spherical, rod, or spiral in shape. After division, bacteria group together and form either cocci, bacilli, spirillia, pairs, clumps or chain configurations. Large numbers of cells are referred to as colonies. Some bacteria require oxygen so they are aerobic (ex: bacteria causing tuberculosis) whereas those that don’t are called anaerobic (ex: bacteria causing tetanus). (See picture below!)
Click here for an activity on bacteria classification!
Growth & Reproduction
Bacteria reproduce via binary fission, a process that looks a bit like mitosis but is simpler. A single strand of DNA replicates and transfers all its genetic material to each new cell. After replication, the bacteria divides into two identical bacteria which can either remain attached or separate.
Click here to see an animation!
Even though sexual reproduction is not common, conjugation occurs in some bacteria. During this process the donor and recipient make cell-to-cell contact through a sex pilus which allows the transfer of plasmids. This gives the recipient altered characteristics. The bacteria then separate.
Click here to see an animation!
If environmental conditions are harsh, some bacteria survive by forming endospores, dormant cells. They are resistant to extreme conditions and when normal conditions return, they sprout and an active bacterium emerges.
Click here to see an animation!