The main claim made by this paper is that a strain of Pseudomonas can cause the formation of nitrogen-fixing root nodules on Acacia - in other words, it is a rhizobium. This is not the first such claim and, like the others, I believe that it falls short of convincing proof. There remains the possibility that the culture was mixed, and the bacteria that actually initiated nodule formation were not the pseudomonads that dominated the culture. I have discussed this in more detail on my rhizobium blog at http://rhizobium.wordpres...