Fig. 5: The in situ structure of the N. maritimus S-layer shows a multichannel sieve nearly perfectly coating cells at high-copy numbers.
From: Membraneless channels sieve cations in ammonia-oxidizing marine archaea
a, The S-layer lattice coats nearly the entire outer surface of N. maritimus cells. A small part of the lattice map (black dashed line) has been cut out from the top of the cell for clarity. The pseudohexagonal lattice is joined together by pentameric defects (Extended Data Fig. 8). Scale bar, 500 Å. Cellular tomography was performed at least 32 times (Extended Data Table 1). b, A model of the S-layer lattice is shown as a space-filling representation with the same colour scheme as in Fig. 1. c, The ion-exchanging model for the N. maritimus S-layer. The highly negatively charged S-layer entraps ammonium ions, and these ions may move along multiple pores in the lattice, aided by increasing negative charge along the lattice. Once beyond the S-layer, the ammonium ions can diffuse to the membrane predominantly composed of crenarchaeol39, where they are converted to nitrite through hydroxylamine (NH2OH) as an intermediate by an unknown protein complex (pink)34, setting up an ion sink and concentration gradient between the S-layer and the membrane.
