Micropepsis pineolensis gen. nov., sp. nov., a mildly acidophilic alphaproteobacterium isolated from a poor fen, and proposal of Micropepsaceae fam. nov. within Micropepsales ord. nov.

An obligately anaerobic, mildly acidophilic, fermentative alphaproteobacterium, designated strain CS4T, was isolated from an acidic, oligotrophic (nutrient poor) poor fen located near Pineola, NC, USA. Cultures contained Gram-negative, slightly curved, non-motile, non-spore-forming, non-prosthecate rods (0.1-0.4 µm in diameter and 0.4-4 µm long, depending, in part, on the growth substrate). Growth optima were 35 °C (range 15-35 °C), pH 5.6 (range of 5.0-6.8), and with 0-50 mM added NaCl (range, 0-100 mM added NaCl). The culture fermented cellobiose, d-glucose, d-mannose, fructose, galactose, glycerol, lactose, maltose, peptone, sucrose, trehalose and xylose. Respiratory growth was not detected. Major fatty acids were C18 : 1ω7c, C19 : 0 cyclo ω8c, C14 : 0 and C16 : 0. The G+C content of the DNA was 61.9±0.3 mol%. The two most closely related species phylogenetically, Rhizomicrobium palustre A48T (AB081581) and Rhizomicrobium electricum Mfc52T (AB365487) shared 94 and 93 % SSU rRNA gene sequence identity, respectively, to that of strain CS4T. Lower SSU rRNA gene sequence identities resulted from pairwise comparisons with members of the order 'Rhizobiales'(85-88 %) or Sphingomonadales(85-86 %). These findings all support the classification of strain CS4T as representative of a novel genus, family and order of Alphaproteobacteria. The type strain of the species pineolensis within the genus Micropepsis, family Micropepsaceae and order Micropepsales is CS4T (=JCM 30711T=ATCC BAA-2724T).