What Are and what do they do???

Survive without food?

Legumes like Nitrogen Fixation.

Then, why do Nitrogen Fixing bacteria exist?

• To give plants the nitrogen needed to develop and grow to many of our favorite vegetables.

Nitrogen fixating bacteria has specific genes, Nitrogen Fixing genes (Nifs)

There are many kinds of Nif Genes!

Such as NifA, NifD, NifK…

Where are Nifs found?

• In some kinds of bacteria.

Example : Anabaena and Azotobacter.

Nitrogen Fixation is done through a Nitrogenase complex…

But due to the complexity of the cofactor, there are three kinds…

Most Nitrogen fixing bacteria has 1 of the 3,

yet, Anabaena has ALL 3 kinds!!!

Then… How did Anabaena acquire those different Nitrogen Fixing

genes?

• First, let us look at the genes of Azotobacter Vinelandii (which is not a cyanobacterium) that contains Nifs and alternatives, Anfs and Vnfs.

• Then, Let us compare its genes to genes of Anabaena.

• Do you think there is a similarity between their Nifs? How about between Vnfs or Anfs of Azobacter and Nifs of Anabaena?

• Considering that they are all Nitrogen Fixing genes, one would expect one of two possibilities…

All Anabaena genes evolved from the same ancestor, while Azotobacter is different…

Or…All Nif genes in Anabaena evolved from the same ancestor, while Vnf evolved from same ancestor as for Vnf in Azotobacter

How do we compare them?

• To understand where it all came from, a TREE must be constructed to compare Azotobacter gene sequence with Cyanobacter gene sequence.

• By Run-Phylip, or Make-Tree

Go to biolingua…

• Bring genes of Azotobacter to biolingua.

• BLAST them against Cyanobacteria

• Add them together, then ALIGN.

• Finally, make a tree.

• Giving the following actual results…

So, how did Anabaena acquire those different Nitrogen Fixing

genes?

• Anabaena genes and Azotobacter genes can share the same ancestors:

Maybe.• Anabaena genes and Azotobacter genes don’t

share the same ancestors:

Most likely the case.

• In order to answer this complex question, further research must be done on this topic to provide enough supporting evidence.

Special Thanks to…

• Dr. Teresa Thiel Associate Dean, College of Arts and Sciences Professor of Biology Department of Biology University of Missouri-St. Louis

…And…• Dr. Jeff Elhai

Dept. of Biology and Center for the Study of Biological ComplexityVirginia Commonwealth University