Photosynthetic Bacteria

Abstract

The purple photosynthetic bacteria belong to two families, the Rhodo-spirillaceae [1] (previously Athiorhodaceae) and the Chromatiaceae [1] (previously Thiorhodaceae) according to whether or not they require a reduced form of sulphur for growth. Although they differ in detail their carotenoids have certain characteristics such as: (i) they are, with a few exceptions, acyclic; (ii) they have tertiary hydroxyl groups at C-l and/or C-l{\textasciiacutex}, which are frequently methylated; (iii) they contain double bonds at C-3,4 and/or C-3{\textasciiacutex},4{\textasciiacutex} and (iv) they can contain keto groups at C-2 and/or C-2{\textasciiacutex} and at C-4.