BIOLOGY 3 Lecture Notes - Lecture 31: Cellulase, Autotroph, Nitrifying Bacteria
Document Summary
Bacteria differ in the need for, and tolerance of, oxygen (o2) Obligate anaerobes are unable to grow in the presence of o2 (anaerobic bacteria that cause botulism, gas gangrene, and tetanus) Facultative anaerobes are able to grow in either the presence or absence of gaseous o2. Aerobic organisms (including animals and most prokaryotes) require a constant supply of o2 to carry out cellular respiration. Photoautotrophs are photosynthetic and use light energy to assemble the organic molecules they require. Primitive photosynthesizing bacteria (e. g. , green sulfur bacteria and purple sulfur bacteria) use only photosystem i that contains bacteriochlorophyll; they do not give off o2 because hydrogen sulfide (h2s) is used as an electron and h. Advanced photosynthesizing bacteria (e. g. , cyanobacteria) use both photosystem i and ii that contain the same types of chlorophylls found in plants; they do give off o2 because h2o is used as an electron and h + donor.
