Minimal media agar plates could be prepared (as this media provides minimal nutrients and is not selective either for Pseudomonas or for Rhizobium )and both the bacterial strains Pseudomonas and Rhizobium could be cross streaked on it. After incubation for about a week the results could be noted. The positive interaction could be seen if both the bacterial population were maintained on agar plates even after a week and if one population survived and other wiped out it suggests negative interaction.

U can also do induction studies. Seedlings can be incubated with particular bacterium and see the grwth rate and promotion etc.  

This depends on the questions you are asking?

Its very difficult to check the interaction on agar plates. And what about the growth rate? We are concerned with bacterial community interface not about plants. This is to check the fate of inoculated bacteria and for consortia studies.

This is where i was telling,  u can find out the colonisation in the rhizosphere if induce the seedlings with particular or a consortium of bacteria.  

I would suggest the used of Ecoplate by biolog. This is usually used for microbial communities studies. When you know the utilization pattern you will be able to know the interaction between each bacteria of your.   

It really depends on what you want to study. If you want to study differential gene expression for instance in the pseudomonas strain in response to the presence of Rhizobia, you could use a promoter trapping technique such as IVET or DFI. IVET is for instance used to study microbe-host interactions or microbe-microbe interactions. Alternatively, you could use RNAseq, but this is technically more demanding and more expensive.

If you want to look for differences in utilization of C- or N-sources you could use omnilog.  

HI Dear Naveen Arora  

You can perform an in vitro antagonistic assay on all isolates. Briefly, spread 100 µl of 5 ×108 CFU ml-1 suspension of each strain on the NA plate’s surface and dry. Then, inoculate 10 µl of 5 ×108 CFU ml-1 suspension of each strain on sterile assay disks (5-mm diameter) and place on the agar. Incubate these plates at 28 ͦC for 48 h and check for signs of clear zones indicating growth inhibition and record.

Best regards

Dear Hans,

Could you please provide more information/papers/articles on the DFI and IVET techniques?

I want to study the interaction of bacteria and fungi in vitro, whether they are antagonistic, mutual, positive or negative.

What is the best approach?

many thanks

Shubhangi