The controversial nature of the Weissella genus: technological and functional aspects versus whole genome analysis-based pathogenic potential for their application in food and health.

Hikmate Abriouel,Vincenzina Fusco,María Del Carmen Casado Muñoz,Jan Kabisch,Beatriz Pérez Montoro,Rohtraud Pichner,Horst Neve,Leyre Lavilla Lerma,Gyu-Sung Cho,Charles M A P Franz,Antonio Gálvez,Nabil Benomar

doi:10.3389/fmicb.2015.01197

Abstract

Despite the use of several Weissella (W.) strains for biotechnological and probiotic purposes, certain species of this genus were found to act as opportunistic pathogens, while strains of W. ceti were recognized to be pathogenic for farmed rainbow trout. Herein, we investigated the pathogenic potential of weissellas based on in silico analyses of the 13 whole genome sequences available to date in the NCBI database. Our screening allowed us to find several virulence determinants such as collagen adhesins, aggregation substances, mucus-binding proteins, and hemolysins in some species. Moreover, we detected several antibiotic resistance-encoding genes, whose presence could increase the potential pathogenicity of some strains, but should not be regarded as an excluding trait for beneficial weissellas, as long as these genes are not present on mobile genetic elements. Thus, selection of weissellas intended to be used as starters or for biotechnological or probiotic purposes should be investigated regarding their safety aspects on a strain to strain basis, preferably also by genome sequencing, since nucleotide sequence heterogeneity in virulence and antibiotic resistance genes makes PCR-based screening unreliable for safety assessments. In this sense, the application of W. confusa and W. cibaria strains as starter cultures or as probiotics should be approached with caution, by carefully selecting strains that lack pathogenic potential.

Highlights

Weissella species are non-spore forming, catalase-negative and Gram-positive bacteria that are nonmotile, with the exception of Weissella (W.) beninensis
No Weissella species have QPS status (European Food Safety Authority (EFSA), 2015) Data on virulence factors present in Weissella species are quite scarce, and genomic analysis can aid in detecting and describing the occurrence of virulence determinants that may be present at species or strain level within this genus
Considering the large number of health-promoting benefits which could arise from the use of strains of Weissella spp., such as antibacterial, anti-viral, anti-tumoral, anti-obesity, antiinflammatory, and antioxidant activities, several weissellas could be targeted for use as starter cultures or probiotics

Summary

Introduction

Weissella species are non-spore forming, catalase-negative and Gram-positive bacteria that are nonmotile, with the exception of Weissella (W.) beninensis. The Weissella genus comprises 19 validly described species (February 20151). Most of these were isolated from and associated with fermented foods, e.g., W. confusa, W. cibaria (Björkroth et al, 2002), W. kimchii (Choi et al, 2002), 1http://www.bacterio.net. As a member of the lactic acid bacteria (LAB), Weissella have complex nutritional requirements. Because of this, they inhabit nutrientrich environments and can be isolated from a variety of such sources, including vegetables, meat, fish, raw milk, sewage, blood, soil, the gastrointestinal tracts of humans and animals, as well as the oral cavity and uro-genital tract of humans (Fusco et al, 2015)

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