Table 1. Geometric Parameters of Spiroplasma Cells.

Parameters	Mean	SD	Units	Reference
Geometric parameters
Coil outer diameter (D+d)	570	70	nm	Fig. 1
Tube diameter (d)	188	19	nm	Fig. 1
Coil centerline diameter (D)	382	69	nm	Fig. 1
Coil inner diameter (D-d)	194	29	nm	Fig. 1
Helical pitch (P)	889	118	nm	Fig. 1
Number of turns (n)	4	0.4		Fig. 1
Centerline lengthper turn (LC)	1,490	210	nm	Eq. 2, Fig.1
Centerline lengthper cell (Lcell)	5,950	1033	nm	Eq. 3
Cell axial length (nP)	3,510	593	nm	Fig. 1
Axial ratio (r)	6.24	1.46		Eq. 1
Helical repeat volume (VC)	4.10×107	6.00×106	nm3	Eq. 4
Cell volume (Vcell)	1.65×108	0.23×108	nm3	Eq. 5
Helical repeat surface (SC)	8.90×105	1.24×105	nm2	Eq. 15
Cell surface area (Scell)	3.54×106	0.61×106	nm2	Eq. 16
Mass parameters
Cell mass-per-length (mcell)	3.74	0.68	MDa/nm	Eq. 6, Figs. 1,3
Mass per cell (Mcell)	22.2	5. 4	GDa	Eq. 7
Membrane mass-per-area(µmemb)	4.67	0.70	kDa/nm2	Figs. 1, 6
Membrane mass per cell(Mmemb)	1.66	0.38	GDa	Eq. 17
Ribosome parameters
Number per unit area (nribosome)	962	102	µm−2	Eq. 24, Fig. 1
Number per unit volume(νribosome)	8,754	935	µm−3	Eq. 24
Number per cell (Nribosome)	1,440	159		Eq. 24
Unit mass of ribosome(mribosome)	2.7	0.05	MDa
Mass per cell (Mribosome)	3.89	1.06	GDa	Eq. 27
Cytoskeleton mass parameters
Length of ribbon per turn(lR = lS)	1,092	179	nm	Eq. 19, Fig. 1
Length of ribbonper cell (LR)	4,368	716	nm	Eq. 20
mass-per-length (mR)	189	70	kDa/nm
Mass per cell (MR)	8.26×105	3.49×105	kDa/nm	Eq. 21

Geometric parameters of Spiroplasma cells were measured directly from high-intensity, dark-field light microscopy and cryoelectron microscopy. Using the helical symmetry of the cell, parameters were extrapolated to entire cells. STEM mass data, obtained per unit length or area, were similarly extrapolated to whole cells. Fig. 1 illustrates diagramatically several of these parameters.