Exploring the strain-specific attachment of Leuconostoc gelidum subsp. gasicomitatum on food contact surfaces

Abstract

The psychrotrophic lactic acid bacterium (LAB) Leuconostoc gelidum subsp. gasicomitatum has emerged as one of the most prevalent specific spoilage organisms (SSOs) of packaged, cold-stored food products in Northern Europe. The whole genome sequencing of the type strain L. gelidum subsp. gasicomitatum LMG 18811T revealed genes encoding for proteins related to adhesion. In the present study the attachment of six food and environmental isolates was monitored on stainless steel (SS) and glass surfaces incubated (7°C for 5–9days) in two food simulating substrates (i.e. sweet bell pepper juice and boiled eggs in brine). The selection encompassed unique genotypes, isolated from different food products or sampling sites as well as slime-forming biotypes. The evaluation of the attached cells was performed with the bead vortexing method and a viability staining assay coupled with epifluorescence microscopy. On SS surfaces the slime-formers showed the lowest attachment (3.3–4.5logCFU/cm2), while strain L. gelidum subsp. gasicomitatum ab2, which was isolated from an acetic acid bath in a vegetable salad company, reached significantly higher populations of attached cells exceeding 7logCFU/cm2. Strain ab2 formed dense cell aggregations on SS after 9days of incubation in sweet bell pepper juice. The attachment ability of L. gelidum subsp. gasicomitatum on surfaces documented in the present study extends our knowledge and understanding of the spoilage potential and intra-subspecies diversity of this microbe.