Nutritional and Metabolic Diversity Prokaryotes can be grouped into four categories according to how they obtain energy and carbon. Autotrophs are organism that can make their own food from inorganic sources. Heterotrophs are organisms that require other organisms in order to obtain organic molecules. 1. A Photoautotroph uses light as its energy source, and CO2 as its inorganic source of carbon. Photosynthetic prokaryotes, include cyanobacteria, plants, certain protists (algae) 2. A Chemoautotroph derives all of its energy from the oxidation of inorganic chemicals. They can the make their organic molecules from the inorganic source such as CO2. 3. A Photoheterotroph is an organism that derives its energy from light but requires organic compounds in order to build its own organic material. 4. A Chemoheterotrophs consumes organic molecules for both energy and organic compounds. Nutritionally, chemoheterotrophs are either saprobes or parasites. Bacteria are called decomposers because they break down organic material and have a role in digesting sewage and oil, production of alcohol, vitamins, antibiotics, and genetic engineering. Saprobes are decomposers that absorb their nutrients from dead decaying matter. Parasites derive their nutrients from the body fluids of living organisms. Non-biodegradable – term use to describe material that are inert to decomposition by microorganisms. Chemoheterotrophs are a very diverse group and shows great variation in their capcity to metabilize nutrients. Some organisms are auxotrophs and require the presence of Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program specific organic nutrients for their growth. Auxotrophy is the inability of an organism to synthesize a particular organic compound required for its growth. Prototrophs can grow on media that contain only a single organic nutrient for example glucose from which they synthesize all of their organic molecules. Bacteriorhodopsin is a protein used by archaea, most notably halobacteria. It acts as a proton pump, i.e. it captures light energy and uses it to move protons across the membrane out of the cell. The resulting proton gradient is subsequently converted into chemical energy. Bacteriochlorophylls are photosynthetic pigments that occur in various phototrophic bacteria. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria. Groups that contain bacteriochlorophyll conduct photosynthesis, but do not produce oxygen. Q. What is the significance of bacteria having so many modes of nutrition as well as being able to live with or without oxygen? Nitrogen is Essential Nitrogen is an important component of proteins as well as nucleic acids. Amino acids and nitrogenous bases are the building blocks of proteins and nucleic acids respectively, and are essential nutrients. Bacterial play a key role in its nitrogen cycling, as well as, other important nutrients through the ecosystem. The Nitrogen cycle is an example of a biogeochemical cycle. Some bacteria can take N2 gas directly from the atmosphere. Anabaena is a good example of a nitrogen fixing prokaryote. It belongs to a group called the cyanobacteria. Still other bacteria like Agrobacteriaum and Rhizobium form mutualistic relationships with plants and help to trap atmospheric nitrogen into a more useful form. Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program Member of what family of plants form mutualistic symbiotic relationships in order to fix nitrogen? ________________________________ Click here for more on the nitrogen cycle Which of the following can bacteria use as an energy source? a. hydrogen sulfide b. nitrites c. sunlight d. ammonia e. all of these What is the role of decomposers in the ecosystem? ________________________________ ________________________________ ________________________________ Distinguish saprobes and parasites. ________________________________ ________________________________ ________________________________ Why is nitrogen important to living organisms? ________________________________ ________________________________ ________________________________ Bacteria play an important role in the cycling of nitrogen. Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program http://www.physicalgeography.net/fundamentals/9s.html Click on the figure for a more detailed description of the nitrogen cycle. By what process is nitrogen returned to the atmosphere in the form of N2? ________________________________ By what process is ammonia converted to either nitrate or nitrate? ________________________________ What is the process that takes nitrogen gas (N2) and assimilates it into organic material? ________________________________ What is the source of nitrogenous material that leads to eutrophication? ________________________________ Organisms also are affected by the presence or absence of oxygen. Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program Important oxygen and metabolism terms Obligate aerobes use O2 for cellular respiration and cannot grow without it. Facultative anaerobes will use O2 if it present, but can also survive by fermentation in its absence. Obligate anaerobes are poisoned by O2. Identify three taxa of photoautotrophs 1 2 3 Food for thought Distinguish between autotrophs and heterotrophs. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ What are the four nutritional modes of bacterial metabolism and how do they differ? Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ What are decomposers? _____________________________________________________ _____________________________________________________ _____________________________________________________ Distinguish between saprobes and parasites? _____________________________________________________ _____________________________________________________ _____________________________________________________ Distinguish between auxotrophic mutants and prototrophs. _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ _____________________________________________________ What do we call organism that are poisoned by the presence of atmospheric oxygen? _____________________________________________________ _____________________________________________________ _____________________________________________________ Organisms that will use oxygen but can use fermentation in its absence? _____________________________________________________ _____________________________________________________ _____________________________________________________ Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program This protein captures light and moves protons across a plasma membrane? _____________________________________________________ _____________________________________________________ _____________________________________________________ Summer 2008 Workshop in Biology and Multimedia for High School Teachers Harvard University Life Sciences – HHMI Outreach Program