I have been trying to find out a bit about what kinds of bacteria have already been found in the atmosphere, so that we can take some educated guesses in trying to culture them in situ. All of the articles I have read thus far have captured some air and tried to culture things from it - and this started back in 1878 by Mr Dowdeswell! But more contemporary accounts ranging from 2m off the ground to 41km up find remarkabley similar types of species. The vast majority are Gram positive from two main groups of G+ve bacteria - Firmiculates and Actinobacteria. There are also reports for the species Pseudomonas from the Proteobacteria but these are G-ve, though very hardy, and are very good at nucleation in clouds. The G+ve are a mix of rods and cocci in shape. And as far as I can tell they're all spore formers - which is a good way of getting through a tough spot. As for the two fungi that have been reported - Engyodontium and Penicillium - they also form spores. Lots more information can be gleaned from the Microbewiki.
So what could we grow them on - they're likely to be anaerobic, and hopefully cold adapted if we're going to grow them, if we start looking at interesting agars may be we'd need something with a low redox potential (like Schaedler's) or something with inorganic nitrogen ( eg Czapek-Dox or Simmon's) or may be try and mimic other extreme environments (Marine) or just go for bog standard stuff (nutrient) in an anaerobic environment. All suggestions welcome, and I'll go and seek advice from some of the micro people here in Brum. I'm going to do some ground level (sea level and ~1000m ie up Snowdon) experiments and comparisons.