Microbiology Question 2 Some photosynthetic Cyanobacteria ca

Microbiology Question 2: Some photosynthetic Cyanobacteria can fix N2 to NH4 + (using the enzyme Nitrogenase) when they are otherwise starved for nitrogen. They sense nitrogen starvation by sensing an excess of the amino acid Glutamate (Glu) within the cell. If there is adequate nitrogen, much of the Glutamate is converted to Glutamine (Gln), so that the [Glu] remains low. A. Sketch the photosynthesis system in a typical Cyanobacterium. B. When the [Glu] gets too high, the genes for Photosystem II are shut off, and the Nitrogenase genes are turned on. What terms are used to describe this regulation ? Assume that the genes in the Nitrogenase operon are under Negative control, and the genes in the Photosystem II operon are under Positive control. Make sketches showing how [Glu] affects both of these operons. C. On your diagram from part (A), show and explain how turning off the genes for Photosystem II will affect the photosynthetic electron flow in this Cyanobacterium? Why is this important to do before the cells produce Nitrogenase? D. Compare this modified photosynthetic system with the system used by Purple Sulfur Bacteria. How are the systems similar? How do they differ?

2. Some photosynthetic Cyanobacteria can fix N2 to NH4 (using the enzyme Nitrogenase) when they are otherwise starved for nitrogen. They sense nitrogen starvation by sensing an excess of the amino acid Glutamate (Glu) within the cell. If there is adequate nitrogen, much of the Glutamate is converted to Glutamine (Gln), so that the [Glu remains low. L12 A. Sketch the photosynthesis system in a typical Cyanobacterium. L16 B. When the Gluk gets too high, the genes for Photosystem II are shut off, and the Nitrogenase genes are turned on. What terms are used to describe this regulation Assume that the genes in the Nitrogenase operon are under Negative control, and the genes in the Photosystem II operon are under Positive control. Make sketches showing how [Glul affects both of these operons. C. On your diagram from part (A), show and explain how turning off the genes for Photosystem L12 I 12 II will affect the photosynthetic electron flow in this Cyanobacterium? Why is this important to do before the cells produce Nitrogenase? L12 D. Compare this modified photosynthetic system with the system used by Purple Sulfur Bacteria. How are the systems similar? How do they differ?

Solution

Cyanobacteria are prokaryotes that can use photosynthesis to convert sunlight into cellular fuel. Knowledge of the organization of the membrane systems in cyanobacteria is critical to understanding the metabolic processes in these organisms. We examined the wild-type strain of Synechocystis sp. PCC 6803 and a series of mutants with altered light-harvesting phycobilisome antenna systems for changes in thylakoid membrane architecture under different conditions. Using small-angle neutron scattering, it was possible to resolve correlation distances of subcellular structures in live cells on the nanometre scale and capture dynamic light-induced changes to these distances. Measurements made from samples with varied scattering contrasts confirmed that these distances could be attributed to the thylakoid lamellar system. So now we know that nitrogenase is the enzyme responsible for fixing atmospheric nitrogen, and it’s found in various microbes that may live alone in the nature or in symbiotics with plants. The nitrogenase molecule looks similar to the sandwich. On both ends of the molecule are two iron containing proteins that are bounded to a molybdenum/iron protein.