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Biology 2108 Lecture
Biodiversity - Prokaryotes: bacteria and archaea
Chapter 27
 

Prokaryotes are typically unicellular organisms that lack a membrane-enclosed nucleus and membrane-enclosed organelles.  From an evolutionary prospective, have prokaryotes been successful?

A side note: where do we put viruses on the tree of life?

The two major groups, bacteria and archaea, were placed in the Kingdom Monera.
Recent molecular analysis of nucleotide sequences have shown that these two groups are distinctly different and diverge from one another very early in the history of life.  Given the phylogenetic tree shown below, why would some systematists insist that these two groups of prokaryotes not be grouped under a single name (i.e. Monera)?
 
 
Numerous other differences now support this division



Are all prokaryotes disease-causing?
   
The human intestine is home to an estimated 500 to 1000 bacterial species, many of which are symbiotes.

Bacteria make up a great proportion of biomass in the worlds oceans.

What would an alien viewing the Earth without bias to size conclude about life on our planet?


Domain Bacteria
Prokaryote, most having cell wall composed of peptidogylcan (and surrounded by a sticky capsule)




The most common method of locomotion in bacteria is the flagellum allowing for taxis.

Would a flagellum work on your motor boat?

Major groups of Bacteria:
Group
Characteristics
Examples
Proteobacteria
gram-negative, diverse group capable
of numerous biochemical pathways
soil bacterium capable of converting
ammonium to nitrate
Chlamydias
parasites on animal cells,
gram-negative
bacterium causing blindness and
urethritis
Spirochetes
helical heterotrophs
syphilis-causing bacterium
Cyanobacteria
photoautotrophs
important planktonic organism in
oceans
Gram-positive bacteria
gram-positive, diverse group important
both ecologically and in human disease
soil bacteria used to produce
the antibiotic streptomycin

Many bacteria can be divided into groups based on response to stain:







Domain Archaea
Prokaryote, cell wall not composed of peptidogylcan

Extremophiles (extreme thermophiles, extreme halophiles, methanogens)




Methanogens use CO2 to oxidize H2 for energy.



Recent molecular analysis of nucleotide sequences has also indicated that prokaryote diversity is much greater and more complex than previous studies have suggested. 

   

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