Preface to Volume Two of the Second Edition of Bergey’s Manual of Systematic Bacteriology -- Preface to the First Edition of Bergey’s Manual of Systematic Bacteriology -- Preface to the First Edition of Bergey’s Manual of Determinative Bacteriology -- Contributors -- Betaproteobacteria -Burkholderiaceae -- Oxalobacteraceae -- Alcaligenaceae -- Comamonadaceae -- Genera incertae sedis -- Hydrogenophilales -- Methylophilales -- Neisseriales -- Genera incertae sedis -- Nitrosomonadales -- Spirillaceae -- Gallionellaceae -- Rhodocyclales -- Class IV. Deltaproteobacteria -- Desulfovibrionales -- Desulfomicrobiaceae -- Desulfobacterales -- Desulfarcales -- Desulfuromonales -- Peolobacter -- Syntrophobacterales -- Syntrophaceae -- Bdellovibrionales -- Myxococcales -- Sorangineae -- Nannocystineae -- Class V.: Epsilonproteobacteria -- Campylobacterales -- Helicobacteraceae -- Index.