Spore-forming Serratia marcescens subsp. sakuensis subsp. nov., isolated from a domestic wastewater treatment tank.

A strain (KREDT) that formed endospores and produced the pigment prodigiosin was isolated from activated sludge. The presence of spores in cells of strain KREDT was evident upon electron microscopy examination, heat treatment and the detection of dipicolinic acid in the cells. Biochemical characteristics, and 16S rDNA sequence and DNA-DNA homology data identified strain KREDT as Serratia marcescens. The major respiratory quinone of strain KREDT was found to be ubiquinone Q-8. The formation of endospores by Gram-negative bacteria has not been observed previously, and has never been reported in any species of Serratia. Here, it is shown that strain KREDT (JCM 11315T = CIP 107489T) represents a novel subspecies of S. marcescens, for which the name Serratia marcescens subsp. sakuensis is proposed.