Betaproteobacteria

Abstract Be.ta.pro.te.o.bac.te'ri.a. Gr. neut. n. bêta , name of the second letter of Greek alphabet (indeclinable); Gr. masc. n. Prōteus , Greek god of the sea, capable of assuming many different shapes; N.L. masc. n. bacter , a rod, L. neut. pl. n. suff. ‐ia, ending to denote a class; N.L. neut. pl. n. Betaproteobacteria , class of bacteria included in the phylum Proteobacteria and having 16S rRNA gene sequences related to those of the members of the order Spirillales . Pseudomonadota / Betaproteobacteria Cells are morphologically diverse—rods, curved rods, spirillae, rings, cocci, reniform rods, stalked rods, multicellular “tablets,” palisades (“ribbons”), or filaments all occur in this class. Cells range from atrichous to monotrichous, amphitrichous or lophotrichous, with “degenerate flagella” in some families. Gliding motility is found in the Neisseriales . Gram‐stain‐negative. Endospores, exospores, and cysts are not produced. Metabolism is extremely variable from fermentation to diverse respiration (molecular oxygen, nitrate, nitrite, nitrous oxide, elementary sulfur, Fe(III), Mn(IV), selenite and/or (per)chlorate are used across the class). Growth ranges from heterotrophic to obligately autotrophic, facultatively autotrophic, or potentially obligately mixotrophic ( sensu heterotrophy and autotrophy occurring simultaneously). Autotrophic taxa are mostly chemolithoautotrophic at the expense of Fe(II), ammonium, nitrite, molecular hydrogen, or reduced sulfur species, with photoautotrophy observed in some Rhodocyclales . Carbon and energy sources for heterotrophic growth include complex media, amino acids, intermediates of Krebs' cycle, aromatics, sugars, sterols, fatty acids, C 1 compounds, alcohols, and amino acids. Most taxa are mesophiles with optimal growth <50°C. Most genera are cytochrome c oxidase‐positive, but catalase activity is variable. The major respiratory quinone is ubiquinone‐8 (UQ‐8), though some taxa use menaquinone‐8 (MK‐8) or rhodoquinone‐8 (RQ‐8). Dominant fatty acids are C 16:0 , C 16:1 , and C 18:0 , with some variation across orders. The class accommodates the orders Burkholderiales , Neisseriales , Spirillales , and Rhodocyclales . DNA G + C content (mol%) : 36.0–72.6 (genomic DNA). Type genus : Burkholderia Yabuuchi et al. 1993, VL45 emend. Gillis et al. 1995, Sawana et al. 2014, Dobritsa and Samadpour 2019.