Actually your question is very interesting. Up to today is known that rhizobia are involved in the change for Auxins and cytokinins synthesis across all the symbiotic interaction stages.

Regards.

Maybe this helps:

SYNTHESIS OF PHYTOHORMONES BY PLANT-ASSOCIATED BACTERIA

By: COSTACURTA, A; VANDERLEYDEN, J

CRITICAL REVIEWS IN MICROBIOLOG Volume: 21   Issue: 1   Pages: 1-18  Published: 1995

If ypou are interested in hormonal manipulation of plants by fungi, you could start to read about the interaction between Gibberella (Fusarium) fujikuroi and rice plants.

Agrobacterium & Pseudomonas strains produce trans-zeatin but don't know about the Rhizobial strains.

Phytohormone production by plant growth promoting bacteria/rhizobia (PGPB) is a major mechanism of growth promotion during plant-microbe interaction. This is also seen in bacterial endophytes which produce IAA for example to modulate plant growth. The one suggested by Mr. Wostemeyer on Gibberella if my reading is accurate, is the first time where gibberellin was discovered to be produced by Fusarium that causes abnormal growth in rice plants.

Rhizobium strains induce nodulations by means of nod factors which are released by the bacteria. This nod factors also is responsible for strain specific interaction of Rhizobium to a particular plant species. 

Isolated Nod factors have also been shown to induce nodulation in the plant roots even in the absence of the bacteria. 

So rather than synthesizing phytohormones, I feel that microbes elicit reponses in plants through certain effector molecules that change the hormonal modulation in the plant cells.

Hope you find the answer useful.

PPFM's or Pink Pigmented Facultative Methylotrophs are a group of ubiquitous epiphytes on most plant surfaces and are thought to be the major source of cytokinins in the plant system. This is a classical example of hormonal level exchange between a microbe and a plant

This seems to me a question of basic nature. As I understand Rhizobia induce nodulation with the help of IAA (plants produce tryptophan and rhizobia convert it into IAA) this IAA is involved in curling of root hair that ultimately leads to nodule formation.