Serratia nevei sp. nov. and Serratia bockelmannii sp. nov., isolated from fresh produce in Germany and reclassification of Serratia marcescens subsp. sakuensis Ajithkumar et al. 2003 as a later heterotypic synonym of Serratia marcescens subsp. marcescens

Abstract

Fifteen enterobacterial strains were isolated from fresh produce. The 16S rRNA gene sequences indicated that these belong to Serratia, with twelve strains showing 99.57%-99.93% and three strains showing 99.86-100% 16S rRNA gene sequence similarity with Serratia marcescens and Serratia nematodiphila as nearest neighbors, respectively. Further comparative multi locus sequence analyses, as well as phylogenomic comparisons, revealed that 6 of the 15 strains were well-separated from their nearest neighbors and formed two clearly distinct taxa. Strains S2, S9, S10 and S15^T were urease-positive, while strains S3^T and S13 were urease-negative. Average nucleotide identity and digital DNA-DNA hybridization comparisons of representative strains S3^T and S15^T with type strains of S. marcescens, S. nematodiphila and S. ureilytica indicated that these shared less than 96% and 70% homology, respectively. Major fatty acids of strains S3^T and S15^T included C16:0, C16:1 ω7c/C16:1 ω6c, C17:0 Cyclo and C18:1 ω6c /C18:1 ω7c. The mol% G+C of genomic DNA of strain S15^T was 59.49% and of strain S3^T was 59.04. These results support the description of two novel species, Serratia nevei and Serratia bockelmannii, with strains S15^T (=LMG 31536^T =DSM 110085^T) and S3^T (=LMG 31535^T =DSM 110152^T) as type strains, respectively. Although Serratia marcescens subsp. sakuensis was previously described to form spores, spores could not be determined in this study. As spore formation was the only differential characteristic of this subspecies, S. marcescens subsp. sakuensis is a later heterotypic synonym of Serratia marcescens.

Keywords: Endospore; Genome; Multi locus sequence analysis; Serratia.