Taxonomy, growth and food spoilage characteristics of a novel Chryseobacterium species
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Animals, humans and food environments are major sources for the isolation of Chryseobacterium species. Spoilage of food by these organisms have become significant in poultry, red meat, milk and fish. Other sources include Beer-bottling plants and lactic acid beverages. Spoilage of food by Chryseobacterium species is mainly due to its proteolytic characteristics. The genus Chryseobacterium was proposed in 1994 and has since expanded to a total of 112 species today. The first aim of this study was to use a polyphasic approach to describe and name strain 7_F195T previously isolated from chicken feather waste collected from an abattoir in Bloemfontein. Methods used for describing strain 7_F195T included: whole genome and 16S rRNA gene sequencing; phylogenetic treeing methods, conventional and commercial system methods for phenotypic characterization; fatty acid profile, polar lipid and respiratory lipoquinone analysis. Chryseobacterium flavum, C. gleum and C. arthrospaerae were identified as being the nearest neighbours. The DNA G+C content of strain 7_F195T supported the affiliation of the strain to the genus Chryseobacterium. The digital DNA-DNA hybridization, ANI and AAI values confirmed that strain 7_F195T does not belong in the following species: C. flavum, C. gleum or C. arthrosphaerae. Various similar phenotypic characteristics were reported between strain 7_F195T and the reference strains, but many differences were also noted. Results obtained from the fatty acid profile, polar lipid and respiratory quinone analysis supported the affiliation of strain 7_F195T to the genus Chryseobacterium. Based on the data generated from this polyphasic study, strain 7_F195T represents a novel Chryseobacterium species for which the name Chryseobacterium pennipullorum sp. nov. is proposed. The second aim of this study was to investigate the temperature growth relationship of a novel Chryseobacterium species, strain 7_F195T, isolated from poultry feather waste in comparison to C. carnipullorum and C. vrystaatense that were isolated from raw chicken portions. The growth study was conducted using a Temperature Gradient Incubator and growth rates and cardinal temperatures were determined through optical density measurements. Temperature profiles and Arrhenius plots were constructed. Strain 7_F195T showed a higher maximum specific growth rate at its optimum temperature in comparison with C. carnipullorum and C. vrystaatense. All the cultures showed relatively low sensitivity to temperature change in the temperature range 25 - 32°C. Strain 7_F195T was the most sensitive while C. vrystaatense was the least sensitivite towards temperature change in the temperature range of about 15 – 26°C. The results of this study concluded that strain 7_F195T may have the ability to cause spoilage at a faster rate than C. carnipullorum and C. vrystaatense at its optimal temperature. Chryseobacterium pennipullorum 7_F195T was successfully classified, described and named as a new species of the genus Chryseobacterium. The growth kinetics of C. pennipullorum 7_F195T was determined and will add value to future research on its food spoilage potential.