The ultrastructure and hydrocarbons of Botryococcus braunii Kützing (Chlorophyceae)

Abstract

The ultrastructure of resting state colonies of Botryococcus braunii Kutzing from two localities is compared to active state colonies maintained in the laboratory. Qualitative hydrocarbon analyses confirmed the physiological status of each sample according to the precedent in the literature; resting state colonies contained botryococcenes, while active state colonies contained a predominance of straight-chain olefins. The ultrastructure of resting and active state colonies is fundamentally similar. The chloroplast of resting state cells contains fewer thylakoids and larger relative numbers of plastoglobuli than the chloroplast of active state cells maintained under favorable growth conditions. Previously undescribed phenomena include the cytochemical demonstration of polyphosphate bodies, microbody-like organelles and ER-ribosomal-mitochondrial complexes. Several new botryococcenes were identified by GC-MS in natural collections of Botryococcus: B30-6a-B33:6a and B35:6a. The mass spectra of the botryococcenes do not yield much structural information, however, they are quite distinct from spectra of the straight-chain olefins. The mass spectra of the hydrogenated derivatives of the botryococcenes (botryococcanes), in contrast, contain three distinctive molecular fragments: M-29, and the two other cleavage products induced by the quaternary carbon. The latter two fragments indicate for each of the homologues the part of the molecule to which the methyl groups are attached. The hydrocarbon fractions of natural collections of resting state colonies fell into three categories. Colonies from Lake Michigan contained B30:6-B32:6, while those from Australia included B34:6-B37:6 as previously reported by other investigators. The remainder of colonies contained green colonies which included olefins characteristic of active state colonies. This is the first report of a mixed population of physiological states from one locality validated by chemical analysis. The identification of major hydrocarbon components is necessary to determine physiological state. This requirement was first indicated by the report of botryococcenes in green colonies by Australian workers. Green colonies grown in another laboratory and analysed in this study also contained botryococcenes.