Give some unique characteristics of the genus Hydrogenobacter of Aquiticales.
(1) They are obligate autotrophs, and represent unusual lipid profile with linear C 18 : 0 and C 20: 1 as major lipids.
(2) They possess a unique quinone, 2 methylthio -1, 4 naphthoquinone.
(3) They have a unique carotenoid pigment.
(4) They possess outer protein coats.
(5) They have a relatively small genome size (Ca 1.0 x 10° bp) compared with the genomes of other bacteria (Ca. 4.0 x 106 bp).