9 CH 13 Prokaryotes endo
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Prokaryotes
Prokaryotes
Smallest and simplest organisms on earthWeight of all bacteria on earth is expected to outweigh all other organisms combined
Incredibly abundant90% of organismal weight in oceans1 g of soil may contain 2.5 billion prokaryote individs
Prokaryotes
Classified as two distinct lineages (domains)Archaea
Do not contain chlorophyll based photosynthesis
BacteriaCell walls containing the complex polymers peptidoglycansSignature molecule to characterize the domains
Prokaryotes
Single circular molecule of DNA associated in nucleoid regionCapacity for plasmids
Remember recombinant DNA technologyCells are generally not compartmentalized
The main exception being thylakoids bearing chlorophyll
Prokaryote Diversity
Rods (bacilli)Cylindrical
CocciSpherical
SpirillaSpiral rods
Prokaryote Repro
Binary FissionAsexual doubling E. coli colony doubling 30 times contains ~1.5% mutant cellsGenetic response to changing environments
Prokaryote ReproConjugation
Most analogous to sexual reproductionCells join via aid of pili and directly pass DNA
Can pass nuclear DNA or independently reproducing plasmidsDNA even passed between bacteria and plant cells
Agrobacterium
TransformationUptake of free naked DNA
TransductionVirus mediated
Endospores
Heat, radiation, and chemically resistant
Often a response to unfavorable conditions or low food supplyCan then germinate in more favorable conditions
EndosporesI Am Legend? Interesting 1954 take on vampires
Nuclear apocalypse releases
Clostridium botulinumCan survive hours of boiling water
Even ancient endospores in the gut of a bee in amber preserved for ~20+ million years were viable
Cyanobacteria
Contain chl. a, carotenoids, and phycobilins
Phycobilins consist of red phycocyanin and blue phycoerythrinDo contain two photosystems
Contain thylakoids and are roughly similar in size to chlorophyll plastids
Endosymbiont theory?Storage product is glycogen
Diversity
Although there may be over 7500 sp. Only ~200 recognized as free living
More evidence of endosymbiont theory
Cyanobacteria
Combined with photosynth algae to form
Vast majority of marine primary productivity~1/2 of all O2 fixed by photosynthesis
Use gas vesicles to regulate their
Extreme fluctuations of temp, nutrients or oxygen causes blooms
Cyanobacteria
Can also fix nitrogenHeterocystsVery few organisms on earth can convert atmospheric N gas to biological relevant NH compounds
AkinetesSpecialized endospore-like structures
Heterocyst Akinete
Purple\ Green Bacteria
The second major group of photosynthetic bacteriaGrow without O2
AnaerobicContain multiple different types of bacteriochlorophyll but only a single photosystemNo phycobillins either
Purple\ Green Bacteria
CO2 +H2S (CH2O) + H2O + 2SMay also substitute different organic compounds such as alcohols and fatsLack thylakoids but have highly convoluted plasma membrane containing sites of photosynthesis and ETC
Closely related to the other major endosymbiont in eukaryotes
Purple\ Green Bacteria
Notice no photolysis! P.121
Hu X et al. PNAS 1998;95:5935-5941