<i>In situ</i> characterisation of biofilms formed by psychrotrophic meat spoilage pseudomonads

Abstract

Psychrotrophic <i>Pseudomonas</i> species form biofilms on meat during refrigerated and temperature abuse conditions. Biofilm growth leads to slime formation on meat which is a key organoleptic degradation characteristic. Limited research has been undertaken characterising biofilms grown on meat during chilled aerobic storage. In this work, biofilms formed by two key meat spoilage organisms, <i>Pseudomonas fragi</i> and <i>Pseudomonas lundensis</i> were studied <i>in situ</i> using five strains from each species. Biofilm structures were studied using confocal microscope images, cellular arrangement, cell counts and biomass quantifications. This work demonstrated that highly dense, compact biofilms are a characteristic of <i>P. fragi</i> strains. <i>P. lundensis</i> formed biofilms with loosely arranged cells. The cells in <i>P. fragi</i> biofilm appear to be vertically oriented whereas this characteristic was absent in <i>P. lundensis</i> biofilms formed under identical conditions. Despite the continued access to nutrients, biofilms formed on meat by proteolytic <i>Pseudomonas</i> species dispersed after a population maximum was reached.