The monotypic genus Gemmiger is placed within the Alphaproteobacteria in Bergey's Manual of Systematic Bacteriology (2nd edition) based on phenotypic characteristics (Gosslilng, 2005) but other data are in conflict with this assignment (ibid.), including small subunit rRNA sequence data (Yarza et al., 2008). Consequently, it has been transferred to Firmicutes in the NCBI taxonomy database based on phylogenetic analysis of the rRNA sequence of the type strain of the type species.

Gossling, J. "Genus XI. Gemmiger Gossling and Moore 1975, 206AL." In: D.J. Brenner,, N.R. Krieg, J.T. Staley, and G. M. Garrity (eds), Bergeys Manual of Systematic Bacteriology, second edition, vol. 2 (The Proteobacteria), part C (The Alpha-, Beta-, Delta-, and Epsilonproteobacteria), Springer, New York, 2005, pp. 520-523. [No PubMed record available.]

Yarza, P., Sproer, C., Swiderski, J., Mrotzek, N., Spring, S., Tindall, B.J., Gronow, S., Pukall, R., Klenk, H.-P., Lang, E., Verbarg, S., Crouch, A., Lilburn, T., Beck, B., Unosson, C., Cardew, S., Moore, E.R.B., Gomila, M., Nakagawa, Y., Janssens, D., De Vos, P., Peiren, J., Suttels, T., Clermont, D., Bizet, C., Sakamoto, M., Iida, T., Kudo, T., Kosako, Y., Oshida, Y., Ohkuma, Arahal, D.R., Spieck, E., Pommerening Roeser, A., Figge, M., Park, D., Buchanan, P., Cifuentes, A., Munoz, R., Euzeby, J.P., Schleifer, K.H., Ludwig, W., Amann, R., Glockner, F.O., and Rossello-Mora, R. "Sequencing orphan species initiative (SOS): Filling the gaps in the 16S rRNA gene sequence database for all species with validly published names." Syst. Appl. Microbiol. (2013) 36(1):69-73.