In situ characterisation of biofilms formed by psychrotrophic meat spoilage pseudomonads

Psychrotrophic Pseudomonas 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, Pseudomonas fragi and Pseudomonas lundensis were studied in situ 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 P. fragi strains. P. lundensis formed biofilms with loosely arranged cells. The cells in P. fragi biofilm appear to be vertically oriented whereas this characteristic was absent in P. lundensis biofilms formed under identical conditions. Despite the continued access to nutrients, biofilms formed on meat by proteolytic Pseudomonas species dispersed after a population maximum was reached.