Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Lysine propionylation was recently shown to be abundant in T. thermophilus, an extremely thermophilic Gram-negative bacterium that belongs to the Deinococcus–Thermus phylum (Okanishi et al. 2014).
Category: