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 CS4(T), 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 mu m in diameter and 0.4-4 mu m long, depending, in part, on the growth substrate). Growth optima were 35 degrees C (range 15-35 degrees C), pH 5.6 (range of 5.0-6.8), and with 0-50mM added NaCl (range, 0-100mM 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 C-18 : 1 omega 7c, C-19 : 0 cyclo omega 8c, C-14 : 0 and C-16 : 0. The G+C content of the DNA was 61.9 +/- 0.3 mol%. The two most closely related species phylogenetically, Rhizomicrobium palustre A48(1) (AB081581) and Rhizomicrobium electricum Mfc52(1) (AB365487) shared 94 and 93% SSU rRNA gene sequence identity, respectively, to that of strain CS4(T). 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 CS4(T) 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 CS4(T) (= JCM 30711(T) = ATCC BAA-2724(T)).