International Journal of Systematic and Evolutionary Microbiology (2002), 52, 141–148 Printed in Great Britain Taxonomic study of Weissella confusa and description of Weissella cibaria sp. nov., detected in food and clinical samples 1 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, PO Box 57, FIN- 00014 Helsinki, Finland 2 Institute for Hygiene and Toxicology, Federal Research Centre for Nutrition, Karlsruhe, Germany 3 German Collection of Micro-organisms and Cell Cultures, Braunschweig, Germany 4 BCCM/LMG Bacteria Collection, Laboratory of Microbiology, University of Gent, Gent, Belgium 5 Laboratory of Microbiology, University of Gent, Gent, Belgium K. Johanna Bjo $ rkroth, 1 Ulrich Schillinger, 2 Rolf Geisen, 2 Norbert Weiss, 3 Bart Hoste, 4 Wilhelm H. Holzapfel, 2 Hannu J. Korkeala 1 and Peter Vandamme 5 Author for correspondence : K. Johanna Bjo $ rkroth. Tel : ›358 9 19149705. Fax : ›358 9 19149718. e-mail : johanna.bjorkroth!helsinki.fi A taxonomic study was conducted to clarify the relationships of two bacterial populations belonging to the genus Weissella. A total of 39 strains originating mainly from Malaysian foods (22 strains) and clinical samples from humans (9 strains) and animals (6 strains) were analysed using a polyphasic taxonomic approach. The methods included classical phenotyping, whole-cell protein electrophoresis, 16S and 23S rDNA RFLP (ribotyping), determination of 16S rDNA sequence homologies and DNA–DNA reassociation levels. Based on the results, the strains were considered to represent two different species, Weissella confusa and a novel Weissella species, for which the name Weissella cibaria sp. nov. is proposed. Weisella confusa possessed the highest 16S rDNA sequence similarity to Weisella cibaria, but the DNA–DNA reassociation experiment showed hybridization levels below 49 % between the strains studied. The numerical analyses of Weisella confusa and Weisella cibaria strains did not reveal any specific clustering with respect to the origin of the strains. Based on whole-cell protein electrophoresis, and ClaI and HindIII ribotyping patterns, food and clinical isolates were randomly located in the two species-specific clusters obtained. Keywords : Weissella confusa, Weissella cibaria, Malaysian foods, clinical samples INTRODUCTION The phylogeny of the bacteria classified currently in the genus Weissella was clarified in 1990. Using both 16S and 23S rRNA sequence data, Martinez-Murcia & Collins (1990) and Martinez-Murcia et al. (1993) showed that Leuconostoc paramesenteroides is phylo- genetically distinct from Leuconostoc mesenteroides and that it groups together with five heterofermen- tative lactobacilli, Lactobacillus confusus, Lactobacil- lus halotolerans, Lactobacillus kandleri, Lactobacillus minor and Lactobacillus viridescens. In a study of leuconostoc-like organisms originating from fer- mented sausages (Collins et al., 1993) the taxonomy of these species was further assessed. This resulted in the description of the genus Weissella comprising the ................................................................................................................................................. Abbreviation : LAB, lactic acid bacteria. The EMBL accession number for the 16S rRNA gene sequence of LMG 17699 T is AJ295989. former Leuconostoc paramesenteroides, the five Lacto- bacillus species, and at that time a novel species, Weissella hellenica. Recently, a novel species, Weissella thailandensis, has been described and suggested to belong to this genus (Tanasupawat et al., 2000). Thus there are currently eight species in the genus Weissella, Weissella confusa, Weissella halotolerans, Weissella hellenica, Weissella kandleri, Weissella minor, Weiss- ella paramesenteroides, Weissella thailandensis and Weissella viridescens. Weissella strains have been isolated from a variety of sources. Weisella paramesenteroides is one of the predominant species in fresh vegetables and it also plays an important role in the first phase of silage fermentation (Dellaglio et al., 1984 ; Dellaglio & Torriani, 1986). Weisella halotolerans, Weisella hellen- ica and Weisella viridescens have been commonly associated with meat or meat products (Niven et al., 1957 ; Milbourne, 1983 ; Collins et al., 1993), whereas the natural habitat of Weisella kandleri is unknown 01891 # 2002 IUMS 141