Syntrophomonas palmitatica sp. nov., an anaerobic, syntrophic, long-chain fatty-acid-oxidizing bacterium isolated from methanogenic sludge Natural lipids such as fats and oils are hydrolysed to longchain fatty acids (LCFAs) and glycerol. Under methanogenic conditions, LCFAs are further degraded by the syntrophic association of LCFA-oxidizing, hydrogen (and/ or formate)-producing fermentative bacteria and hydrogenotrophic methanogens, because the oxidation of LCFAs is thermodynamically unfavourable in such environments unless the consumption of hydrogen and/or formate is coupled with oxidation (Schink, 1997). Therefore, LCFAdegrading anaerobes can gain only a small amount of energy through these syntrophic reactions and thus their growth is generally slow. In addition, LCFAs can cause substrate toxicity in microbes. Consequently, isolation of LCFA-degrading bacteria has been difficult and, at the time of writing, only six species/subspecies have been described. Five of these belong to the family Syntrophomonadaceae within the phylum , 2007). There is only one species described to date belonging to the class Deltaproteobacteria, i.e. Syntrophus aciditrophicus (Jackson et al., 1999), which also degrades LCFAs syntrophically.Recently, we successfully isolated strain MPA T from methanogenic granular sludge that was taken from palm oil mill effluent treated in a mesophilic upflow anaerobic sludge blanket reactor (Hatamoto et al., 2007). In a previous study, strain MPA T was found to be able to grow on palmitate in co-culture with the hydrogenotrophic methanogen Methanospirillum hungatei JF-1 T (DSM 864 T ).Abbreviations: FAME, fatty acid methyl ester; LCFA, long-chain fatty acid.The GenBank/EMBL/DDBJ accession numbers for the rrnA and rrnB operons of the 16S rRNA gene sequence of strain MPA T are AB274039 and AB274040, respectively.A phase-contrast micrograph showing the cell morphology of strain MPA T is available as supplementary material with the online version of this paper.