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BI-122 Biology
Prokaryotes
General Characteristics
- Cells bounded by plasma membrane
- cell walls, various materials
- gelatinous capsule, various materials
- classified by chemical characters
- absence of membrane-bound organelles
infolding of cell membrane probably serves organelle function
- absence of nuclear membrane;
presence of central nuclear region
- single, circular double stranded DNA molecule ['chromosome']
without associated chromatin protein [typical of eukaryotic chromosomes]
- few to numerous plasmids
consist of short DNA fragments
- asexual reproduction
- reorganization of nuclear region to separate DNA into two nuclear regions
- cell fission
- no sexual reproduction
exchange of genetic information occurs:
- conjugation = sharing of DNA material by merging two cells together
- transformation = collect plasmids from dead cells in medium
- transduction = transfer of plasmids between cells by bacteriophage virus
- plasmids may be incorporated into circular DNA molecule
Classification
Archaea [archaebacteria]
- Most primitive organisms known
- may still be forming near volcanic 'black smokers' along Mid-Atlantic rift
- unique sequences of bases in RNA
- chemosynthetic
- methane bacteria
- obligate anaerobes
- common in benthic deposits, hot springs, fecal material, decaying organisms,...
- derive energy from methane [marsh gas] production
CO2 + 4H+ → CH4 + 2O-2
- Salt bacteria
- photosynthetic, using bacterial rhodopsin, red in color
does not produce waste O2
- found in brine [Great Salt Lake, Dead Sea, desalination plants,...]
- Sulfolobus bacteria
- derive energy by changing ionization state of sulfur
sulfurous to sulfuric, yielding H2S [rotten egg smell]
- found in geothermal sulfur hot springs, embers of coal tailing,
perhaps coal deposits,...
- ribosomes are unusual shape (and smaller) compared to other organisms
Bacteria, or true bacteria
- Class Bacteriophyta
- heterotrophic free-living
saprophytes, on decaying organisms
- heterotrophic parasites
including pathogenic types
- autotrophic, free-living
- purple sulfur bacteria, with bacteriochlorophyll, or b-chlorophyll
CO2 + 2H2S → (CH2O)n
+ H2O + 2S
- purple nonsulfur bacteria, with bacteriochlorophyll, or b-chlorophyll
CO2 + 4H+ → (CH2O)n
+ H2O
- green sulfur bacteria, with unique chlorobium chlorophyll
CO2 + 2H2S → (CH2O)n
+ H2O + 2S
- Iron bacteria, change ionic state of Fe (ferrous to ferric)
- Sulfur bacteria
hydrogen sulfide to elemental sulfur
elemental sulfur to sulfate (sulfurous)
- Hydrogen bacteria, molecular hydrogen to ionic hydrogen
- Nitrifying bacteria, molecular N2 to nitrites (nitric)
- Nitrogen fixing bacteria, nitires to nitrates (nitrous)
frequently in root nodules of Legumes
- Class Cyanobacteria [blue-greens, formerly blue-green algae]
- chlorophyll a, as in green Protists and Plants
- phycobilins
blue phycocyanin
red phycoerythrin
- produce waste O2
- alternate pathway: nitrogen fixing
- found in non-acidic fresh water, salt water (marine), hot springs [Yellowstone],
frozen lakes and glaciers (Antarctic and Arctic regions)
- Class Prochlorobacteria [bright green]
- discovered in 1976 by R. A. Lewin, Scripps Institute of Oceanography
shallow marine waters, off the coast of Baja California
- chlorophyll a and chlorophyll b, as in green Protista and Plants
- no phycobilins, but caretinoid pigments as in Plants
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© 2004-2005 TwoOldGuys ™
revised 19 aug 2006