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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. Attempts to elicit the transition of active to resting state colonies utilizing different light intensities and/or nitrogen deficient media were unsuccessful. Instead, these experiments induced the formation of yellow or whitish-brown senescent colonies which always contained a predominance of olefins. Senescent cells contain reduced, peripherally displaced organelles. Most of the cytoplasm is occupied by vacuoles and lipid (probably hydrocarbon) inclusions. Morphologically identifiable polyphosphate bodies are usually small or absent. Observations pertinent to the mechanism of hydrocarbon secretion were in basic agreement with previously published information. The outer cell wall, or trilamellar structure (TLS), was recently as the primary site of hydrocarbon accumulation and production. The role of the TLS in hydrocarbon biosynthesis, however, should be cautiously regarded without additional evidence. |
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