BIOLOGY 3 Lecture Notes - Lecture 32: Chlorophyll, Ribosomal Rna, Chemotroph
Document Summary
Earlier classification of bacteria was based on metabolism, nutrition, etc. Work by carl woese since 1980 has revised bacterial taxonomy based on similarity of 16s rrna. 12 groups are now recognized based on bacterial 16s ribosomal rna sequences. Some possess heterocysts, thick-walled cells without a nucleoid, where nitrogen fixation occurs. Cyanobacteria are common in fresh water, soil, on moist surfaces, and in harsh habitats (e. g. , hot springs) Some are symbiotic with other organisms (e. g. , liverworts, ferns, and corals) lichens are a symbiotic relationship where the cyanobacteria provide organic nutrients to the fungus and the fungus protects and supplies inorganic nutrients. Cyanobacteria were probably the first colonizers of land during evolution. Cyanobacteria bloom when nitrates and phosphates are released as wastes into water; when they die off, decomposing bacteria use up the oxygen and cause fish kills. Relationship to domain bacteria and domain eukarya.
