Plasticicumulans lactativorans sp. nov., a polyhydroxybutyrate-accumulating gammaproteobacterium from a sequencing-batch bioreactor fed with lactate.

ABSTRACT

A bacterial consortium that accumulated more than 90 % (w/w) polyhydroxybutyrate (PHB) from lactate was selected in a laboratory-scale bioreactor with a 'feast-famine' regime. Bacterial strain YD(T), representing a dominant species in this enrichment, was isolated and characterized. Analysis of the 16S rRNA gene sequence revealed that the isolate is a member of the class Gammaproteobacteria, forming an independent phylogenetic lineage. The closest relative of the isolate was Plasticicumulans acidivorans TUD-YJ37(T), with 94 % 16S rRNA gene sequence similarity. Strain YD(T) was an obligate aerobe with large, ovoid, Gram-negative cells, motile by means of a polar flagellum. It utilized a relatively broad spectrum of substrates (e.g. carbohydrates, fatty acids) as carbon and energy sources. The temperature range for growth was 20-45 °C, with an optimum at 40 °C; the pH range was pH 6.0-8.0, with an optimum at pH 7.0. The major respiratory lipoquinones were Q-8 (91 %) and Q-7 (9 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine and an unidentified aminolipid. The predominant fatty acids in the membrane polar lipids were C16  1ω7c, C16  0 and C18  1ω7c. The G+C content of the genomic DNA was 68.5 mol%. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, the isolate is proposed to represent a novel species in the genus Plasticicumulans, for which the name Plasticicumulans lactativorans sp. nov. is proposed. The type strain is YD(T) ( = DSM 25287(T) = NCCB 100398(T)).