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Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

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Page 1: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Enzyme catalyzing Nitrogen Fixation in Bacteria

Root nodules on legumes

Page 2: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Nitrogenase is the enzyme found in a variety of bacteria, some of them symbiotic with

plants

• catalyzes the conversion of molecular nitrogen (N2) from the air into ammonia (NH3).

• It is found in a variety of bacteria, some of them symbiotic with plants.

Page 3: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Diversity of N-fixing Bacteria

Page 4: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Choosing the sequence to compare

• Nitrogenase consists of a molybdenum-iron (MoFe) protein and an iron (Fe) protein. The MoFe protein contains 2 alpha protein chains and 2 beta protein chains.

Page 5: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Trials and Errors

• Constructed a phylogenetic tree of the Mo-Fe protein of nitrogenase from published nucleic acid data.

• Tried to get a more coherent tree by eliminating some of the sequences.

• Tree still not revealing.• Mistake: using nucleotides, switched to amino acid

sequences for the alpha and beta chains.

Page 6: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Amino Acid sequence

• Obtained amino acid sequence of alpha and beta subunits of MoFe protein from Azotobacter vinelandii

• Did an alignment on alpha and beta subunits and found 20.1% identity and , 78% global alignment, suggesting that alpha and beta chains are the product of gene duplication.

Page 7: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Crystallographic structure

• Found crystallographic structure for MoFe protein from A. vinelandii shown on next slide.

Page 9: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Gene Duplication in the Mo-Fe Protein of Nitrogenase

Page 10: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 54.18 The nitrogen cycle

Page 11: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.9 The role of soil bacteria in the nitrogen nutrition of plants (Layer 3)

Page 12: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.10 Root nodules on legumes

Page 13: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.10x Nodules

Page 14: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.11 Development of a soybean root nodule

Page 15: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.13 Molecular biology of root nodule formation

Page 16: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 37.12 Crop rotation and “green manure”

Page 17: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 27.11 One of the most independent organisms on earth: Cyanobacteria (Anabaena)

Page 18: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 27.11x1 Cyanobacteria: Gloeothece (top left), Nostoc (top right), Calothrix (bottom left), Fischerella (bottom right)

Page 19: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 27.11x2 A bloom of cyanobacteria

Page 20: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Nutrient Deficiencies: Agricultural Importance

Nitrogen deficiency

Page 21: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 54.9 Nutrient addition experiments in a Hudson Bay salt marsh

Page 22: Enzyme catalyzing Nitrogen Fixation in Bacteria Root nodules on legumes

Figure 27.8 Specialized membranes of prokaryotes