Plants without bacteria? is it theoretically possible?
This is the sort of question that should be considered from more than one perspective.  Since this is speculation, take it as a given that there is a lot of 'what if' here. 

I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen.  If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.  

Can bacteria emerge from just a world of plants?  I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes.  Would it happen in time?  Most would be skeptical whether that timing could work out.  

In practice it would be hard to create a world like this.  I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance.  If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight.  Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included.  But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear.  Here it looks like some water plants and fish have been done.  If there was a plant that created CO₂ at an adequate rate its possible.

At one time there were no animals at all.  Its thought that for a while there might have only been photosynthetic structures that lay in the water and soaked up the rays.  Its not clear whether as some say there were colony formations of cyanobacteria as we see today, or whether there may have been larger pre-cellular or proto-cellular structures.  But recovering the pre-cambrian configurations of genes from just plant genomes seems like a gambler's bet to me.