In addition to P. luminescens and X. nematophila, most studied species include P. asymbiotica Fischer- Le Saux et al., P.temperata Fischer-Le Saux et al., X. beddingii (Akhurst) Akhurst and Boemare, X. bovienii (Akhurst) Akhurst and Boemare, X. japonica Nishimura, and X. poinarii (Akhurst) Akhurst and Boemare