9 CH 13 Prokaryotes endo

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