Download 1. Sporulation in genus Bacillus: properties of endospores that

1. Sporulation in genus Bacillus:
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properties of endospores that distinguish them from vegetative cells (table 4.3 text).
nutritional factors that induce- C, N, and P limitation.
7 stages of sporulation. what features/properties distinguishes each stage?
differential gene expressiono role of sigma subunit of RNA polymerase.
o activation of sigma F and E in forespore and mother cell compartment
respectively.
o cross-talk between forespore and mother cell leads to mature endospore.
not a reproductive stage in the life cycle of bacterium, but a survival mechanism.
2. Heterocyst Formation (in the filamentous cyanobacteria Anabaena):
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assimilation of ammonia into organic carbon:
o L-glutamate dehydrogenase (GH)
o L-glutamine synthetase (GS) and glutamate synthetase (GOGAT)
nitrogen fixation:
o requirement for reducing power and ATP
o Properties of enzyme (nitrogenase)- sensitivity to O2
o general groups of bacteria that carry out N2-fixation (table 20.2). How do obligate
aerobes like Azotobacter vinelandii protect the nitrogenase enzyme for oxygen?
properties of heterocyst:
o heterocyst formation triggered when cells limited for fixed nitrogen. Heterocysts
formed every 10-20 cells in filament.
o cell wall of heterocyst limits or prevents O2 and other gases from entering.
o photosystem II non-functional.
o photosystem I directed at producing ATP not NADPH.
o heterocyst no longer able to fix CO2
o nitrogenase in heterocyst fixes N2 to NH3
o NH3 is converted to glutamine in heterocyst and exported to neighboring
photosynthetic cells. For these processes to occur the photosynthetic neighbors
must provide heterocyst with an electron donor and glutamic acid.
o heterocyst is terminally differentiated (unlike endospores, heterocyst can not
differentiate back to a oxygenic photosynthetic cell).