What class of proteobacteria that are oligotrophs, an organisms capable of living in low-nutrient environments such as deep oceanic sediments, glacial ice, or deep undersurface soil?

What class of proteobacteria which survive on a minimal amount of nutrients and also are eutrophs?  

What class of proteobacteria is the most diverse class of gram-negative bacteria and it includes a number of human pathogens?

What class of proteobacteria that has a small class of gram-negative Proteobacteria that includes sulfate-reducing bacteria?

What is the smallest class of proteobacteria which are gram-negative microaerophilic bacteria?

What class of proteobacteria that genus Bordetella belong?

What class of proteobacteria that genus Begiattoa belong?

What class of proteobacteria that genus Rhizobium belong?

What class of proteobacteria that genus Helicobacter belong?