Abstract
Photobacteria are common psychrophilic bacteria found in marine environments. Recently, several studies revealed high numbers of Photobacterium (P.) spp. on packaged fresh meat. Their occurrence appears relevant for the spoilage of meat, since species of the genus are already known as potent fish spoilage organisms. Here we report on distribution, biodiversity, and specific traits of P. carnosum (n = 31), P. phosphoreum (n = 24), and P. iliopiscarium (n = 3) strains from different foods. Biodiversity was assessed by genomic fingerprinting, diversity index analysis, growth dynamics, comparison of metabolic activities, and antibiotic resistance. We observed a ubiquitous occurrence of the species on all common meats independent of packaging conditions and producer, suggesting contamination during an established processing or packaging step. Regarding biodiversity, the three species differed clearly in their growth properties and metabolic characteristics, with P. phosphoreum growing the fastest and showing the strongest alkalization of the media. On strain level we also recorded variations in enzymatic reactions, acid production, and antibiotic resistances not restricted to specific meat types. This depicts high biodiversity on species and strain level on each contaminated meat sample. Our analysis showed that meat-borne strains of P. phosphoreum and P. iliopiscarium clearly differ from their type strains from a marine habitat. Additionally, we report for the first time isolation of P. carnosum strains from packaged fish, which in contrast showed comparable phenotypic properties to meat-borne strains. This hints at different initial origins of P. phosphoreum/P. iliopiscarium (marine background) and P. carnosum (no demonstrated marine background) contaminations on fish and meat, respectively.
Highlights
Photobacteria are Gram-negative, facultatively aerobic members of the Vibrionaceae family and well known as marine-related species (Lo et al, 2014; Li et al, 2017; Wang et al, 2017)
We identified a correlation of isolation source and metabolic properties that was depicted by the clustering of almost all P. phosphoreum strains from beef (Figure 4A)
The data obtained from our study give further evidence that photobacteria, FIGURE 4 | Clustering of selected strains by metabolic properties based on API 50CH and API ZYM
Summary
Photobacteria are Gram-negative, facultatively aerobic members of the Vibrionaceae family and well known as marine-related species (Lo et al, 2014; Li et al, 2017; Wang et al, 2017). Photobacteria are known as effective saprotrophs in marine habitats (Urbanczyk et al, 2011). In this context, certain species, i.e., Photobacterium (P.) phosphoreum and P. iliopiscarium constitute a considerable problem in the food industry, representing potent spoilers of chilled fish and seafood products (Okuzumi et al, 1994; Dalgaard et al, 1997). The spoilage processes involve production of biogenic amines such as histamine (Okuzumi et al, 1994; Jorgensen et al, 2000; Emborg et al, 2002; Torido et al, 2012; Takahashi et al, 2015; Bjornsdottir-Butler et al, 2018) that can lead to scombroid fish poisoning (Lehane and Olley, 2000)
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