BIOL 1108 Edition 1nd Lecture 8 Outline of Last Lecture I Learning Objectives II In The News III Bacterial Growth IV Bacterial Habitats V Antibiotics Outline of Current Lecture I Learning Objectives II In The News III Functions of Cilia IV Symbiogenesis V Origin of Mitochondria VI Hydrogen Hypothesis VII Mitochondrial Metabolism VIII Ring of Life IX Stromatolites Current Lecture I Learning Objectives What are the evolutionary relationships between Archaea Bacteria Eukaryotes What functions do cilia eukaryotic flagella play in protists and multicellular organisms How would you describe the chimeric nature of the eukaryote cell Are mitochondria and plastids the descendants of bacteria How and when did they become established in eukaryotes How is it that both mitochondria and chloroplasts came to be distributed throughout all the major lineages of protists These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II In The News Why did a Georgia jury convict brothers Michael and Stewart Parnell for making peanut butter Salmonella poisoning III The most likely explanation for how the Salmonella got into the peanut butter was a leaky roof at the factory Salmonellae are disseminated in the natural environment water soil sometimes plants used as food through human or animal excretion Humans and animals either wild or domesticated can excrete Salmonella either when clinically diseased or after having had salmonellosis if they remain carriers Salmonella bacteria are hardy and can survive remain dormant for a long time The roasting of peanuts is the only step that will kill the salmonella Fatty foods are also more protective of salmonella so when it gets into the acid of the stomach which is our first line of defense it may not get destroyed Peanut butter being a highly fatty food could survive better http youtu be j5GvvQJVD Y Functions of Cilia Motility Photosensory flagellar swelling is the light detector by using light sensitive protein rhodopsin and the eyespot determines light shading Cells reorient moving towards moderate light in a positive phototaxis and away from strong light in a negative phototaxis Chemosensory IV Thigmosensory Covered with long hairs Intraflagellar transport The nine fold symmetry of the outer doublets allows for the greatest number of possible movements Symbiogenesis The merging of two separate organisms to form a single new organism coined by Konstantin Mereschkowski Endosymbiosis V It is reasonable to assume that the cyanobacterial symbiont willingly gave up its fixed carbohydrates to the host cell All cyanobacteria surround themselves with a coating of mucilage a transparent mixture of carbohydrates that helps hold cells together and also prevents desiccation serves as a carbohydrate source for the host cell Selection could favor a cell that can retain a photosynthetic symbiont as this would provide a steady source of fixed carbohydrates as long as there were available sunlight water and carbon dioxide 3 Levels of symbiosis In primary 1o symbiosis a eukaryote consumed a cyanobacterium which evolved into a chloroplast In the case of secondary symbiosis 2o a phagotrophic eukaryote ingests a photosynthetic eukaryote red or green alga and retains the chloroplast In tertiary 3o a eukaryote ate a eukaryote which ate a eukaryote which ate a prokaryote Origin of Mitochondria Facilitated a bacterium becoming a mitochondrion The original bacterium was a parasite The environment inside the host cell provided protection for the bacterium The bacterium had the ability to resist digestion by the host cell Been an impediment to a bacterium becoming a mitochondrion How would the original bacterium transport energy ATP to the host How did the bacterium have the ability to resist digestion by the host cell How would an anaerobic host ever encounter an aerobic bacterium if they lived in separate environments Provide data in support of a bacterium becoming a mitochondrion Do mitochondria still have bacterial cell walls or the genes for peptidoglycan walls Does the lipid composition of the mitochondrial membrane match that of bacteria or archaea o Both of the mitochondrial membranes appear to be bacterial origin Where is the DNA of mitochondria o The DNA mitochondria and chloroplasts is both in the nucleus and still retained in the organelle Booth chloroplasts and mitochondria have retained their own ribosome genes and translation machinery and still make a few essential proteins that are not yet made in the nucleus The primary selective force that led to the establishment of the first mitochondrion was the host cell needed the waste products of the bacterium VI Hydrogen Hypothesis Ancient Earth conditions were such that much of the marine ecosystem was anaerobic but as cyanobacteria pumped out oxygen as a waste product of photosynthesis there was increasing amounts of O2 There was also plentiful amounts of H2 from natural sources After a time the natural geologic source of H2 became depleted and yet methanogenic Archaea still need hydrogen As it turns out hydrogen carbon dioxide and acetate are waste products of anaerobic metabolism in some bacteria As the dependency of the Archaean grew on the bacterium there would have been a strong selection for a closer physical connection between the two This would have made it easier for the waste products of anaerobic metabolism to have been transferred to the Archaean cell Eventually this connection became complete with the bacterium becoming completely encompassed by the Archaean host If the bacterium still retained it dual ability to function as a facultative anaerobe then the chimeric proto eukaryote would also be a facultative anaerobe VII Mitochondrial Metabolism Aerobic vs anaerobic VIII Among the protists all varieties of mitochondria are found from classic aerobic to strictly anaerobic It is presumed that adaptations to anaerobic or microaerobic environments has occurred multiple times among the protists leading to a variety of lineages that have either permanently reduced their mitochondria or can function as facultative anaerobes Ring of Life The eukaryotic genome is therefore a chimera of genes from multiple different organisms and lineages Originally a hybrid of the archaean host and the alpha proteobacterial partner there have been subsequent gene transfers from parasites both bacterial and viral and in the case of plants from