Nitrogen fixation mechanism in legumes

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1. Presentation on Nitrogen fixation mechanism in legumes Nusrat Jahan Shimmi ID: 1502036 Faculty of Agriculture Sylhet Agricultural University

2. The  process by which free nitrogen from the air  is combined  with other elements to form  organic   compounds   that plants  can use as nutrients .   Cyanobacteria  and certain  other  forms  of bacteria,especially   those  that live in  the  roots  of legumes,   convert   gaseous ,   nitrogen   into organic  compounds . T he  conversion of  nitrogen   gas  to  nitrates  by  some   bacteria. Nitrogen Fixation

3. Importance Of Nitrogen Fixation

4. Rhizobia Bacteria The first Rhizobia were isolated from root nodules by M. Beijerinck , and shown to have the ability to re-infect their legume hosts, and to fix N 2  in symbiosis. Rhizobium   leguminosarum   is aspecies of gram-negative, aerobic, rod shaped bacteria that is found in soil and which causes formation of root nodules on some, but not all, types of field pea, lentil, kidney bean, and clover.

5. 1. Rhizobia attracted to root 2. Rhizobia attach to root hairs 3. Root hair curling 4. Infection thread formation Nodule Formation

6. CONTD.. 5. Root cortical cell division 6. Rhizobia invade cortical cells 7. The nodule grows 8. Fully functional nodule

7. Biological nitrogen fixation was discovered by the German agronomist Hermann Hellriegel  and Dutch microbiologist Martinus Beijerinck . Biological nitrogen fixation can be represented by the following equation, in which two moles of ammonia are produced from one mole of nitrogen gas, at the expense of 16 moles of ATP and a supply of electrons and protons (hydrogen ions): N 2   + 8H+ + 8e –  + 16 ATP = 2NH 3  + H 2  + 16ADP + 16 Pi This reaction is performed exclusively by prokaryotes (the bacteria and related organisms), using an enzyme complex termed  Nitrogenase . This enzyme consists of two proteins – an iron protein and a molybdenum-iron protein . Symbiotic Nitrogen Fixation:

8. Mechanism of Nitrogen Fixation in Root Nodules of Legumes Nitrogen fixing bacteria (Rhizobium) that fix atmospheric Nitrogen

9. Glucose-6-phosphate acts as a electron donor Glucose-6-phosphate is converted to phosphogluconic acid NADPH donates electrons to ferrodoxin. Protons released and ferrodoxin is reduced Reduced ferrodoxin acts as electron carrier. Donate electron to Fe-protein to reduce it. Electrons released from ferrodoxin thus oxidized Pathway of Nitrogen Fixation in Root Nodules of Legumes

10. Reduced Fe-protein combines with ATP in the presence of Mg +2 Second sub unit is activated and reduced It donates electrons to N2 to NH3 Enzyme set free after complete reduction of N2 to NH3 CONTD..