Table 1.

Elongated carboxysome numbers in chloroplast cross-sections and in purified preparations

Particle type	Proportion in chloroplast sectionsa	Proportion in purified extractsa	Dimensions (nm)b,c
Cyanobium carboxysomes	n.a.	100%	101.3 ± 0.7
CyLS-S1S2 carboxysomes	96% (n = 565)	84% (n = 412)	100.3 ± 1.5
CyLS-S1S2 elongated rods	4% (n = 24)	16% (n = 78)	59 ± 5 (n = 16) × 437 ± 190 (n = 12)

^aProportions in each particle type in chloroplast sections and purified extracts were determined from analysis of TEM images. Elongated rods were defined as structures with average widths <75 nm and disproportionate length

^bCarboxysome dimensions were determined as the mode (±s.e.m.) of particle distributions measured using a Nanosight NS300 from 12 analyses of two independent preparations of Cyanobium carboxysomes and 19 analyses of three independent preparations of CyLS-S₁S₂ carboxysomes

^cElongated rod dimensions were determined as mean widths and lengths (±s.d.) of particles analysed in TEM images of purified carboxysome preparations from CyLS-S₁S₂ leaves. Note that there is a greater proportion of elongated particles observed in purified extracts, which we assume to be due to a combination of: breakage of very long particles during isolation, giving rise to a greater proportion of rods and, difficulty in accurately identifying elongated carboxysomes in random cross-sections of chloroplasts. n.a. not applicable