The taxonomy and significance of Chryseobacterium isolates from poultry
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Species of the genus Chryseobacterium (family Flavobacteriaceae) occur widely in clinical, environmental and industrial ecosystems. In the clinical environment, they are uncommon etiologic agents, but their infections may be serious in immunocompromised patients. They are often resistant to multiple antimicrobial agents making infections due to these organisms potentially difficult to treat. In the food environment, they are known to cause spoilage of foods such as canned products, milk and dairy products, fish, meat and poultry. It is therefore necessary to be able to solve or anticipate and avert possible problems caused by Chryseobacterium species. This genus also has positive characteristics which include synthesis of a number of enzymes potentially useful in industry (e.g. keratinolytic enzymes), medicine (e.g. prion degradation) and turnover of organic matter in soil, water and sewage plants. Taxonomic studies are key to solving such problems by characterization and identification of such organisms. This also sets the foundation for investigation of the organism’s beneficial roles and applications. In this study, some Chryseobacterium strains isolated from poultry feather waste and raw chicken, were phenotypically characterized and identified using conventional tests and the BIOLOG Omnilog Gen II system. Phylogenies of seven selected isolates were determined using the 16S rRNA gene sequence analysis and they were further characterized using the BIOLOG Omnilog Gen III identification system. They fell into four taxonomic groups (Group 1: 1_F178; Group 2: 5_R23647; Group 3: 6_F141B and 7_F195; and Group 4: 8_R23573, 9_R23581 and 10_R23577) which did not show affiliation to any currently recognised type species of the genus Chryseobacterium suggesting that these groups were possible representatives of novel species. Three selected strains (8_R23573, 9_R23581 and 10_R23577) were subjected to a polyphasic taxonomic study to determine their exact taxonomic identities. Results of the predominant respiratory menaquinone, fatty acid methyl esters and DNA base composition supported the affiliation of the strains to the genus Chryseobacterium. When subjected to DNA-DNA hybridization, the strains gave relatedness values of more than 81% among the three strains and less than 57% similarity between the strains and their two nearest phylogenetic neighbours C. shigense (DSM 17126T) and C. luteum (LMG23785T). A novel species emerged after a comparison of the phenotypic, chemotypic and genotypic results. The new species was described and the name Chryseobacterium carnipullorum sp. nov. was proposed. Analysis using the BIOLOG Phenotype MicroArray (PM) system, revealed that C. carnipullorum has the potential to cause food spoilage mainly by utilizing carbohydrates, carboxylic acids and amino acids by producing metabolites which lead to souring, butyric spoilage defects, alkalinisation, bitter tastes and sulphide spoilage. The organism was also shown to have potential for biotechnological applications in food and stockfeed technology; coffee extraction, oil drilling and detergent industries; manufacture of artificial antigens and chemical diagnostic agents and release of oligosaccharides and oligopeptides in (ultra) oligotrophic freshwater environments. It was found that the new species was able to produce extracellular keratinases that were able to extensively degrade chicken feather waste in 48 h. This has the potential of contributing toward solving the disposal problem which is experienced by the poultry industry that produces huge amounts of the recalcitrant feather waste as a by-product. Currently, a very small percentage of feather waste is steamed, treated chemically and ground to form dietary protein supplement for stockfeeds. Degradation of feathers using keratinolytic organisms is a more economical and environmentally friendly alternative. Chryseobacterium carnipullorum also has the potential for application in other biotechnological processes involving keratin hydrolysis. Hydrolysed feathers can be converted to fertilizers, glues, films, and they can be used as the source of rare amino acids, such as serine, cysteine and proline.