VARIABILITY OF CELL WALL STRUCTURE AND HYDROCARBON TYPE IN DIFFERENT STRAINS OF BOTRYOCOCCUS BRAUNII 1

Different samples of Botryococcus braunii Kütz., freshly collected from nature or laboratory‐grown from culture collection strains, were studied by electron microscopy and their hydrocarbon content analyzed. Although the general internal structure of the cells was rather constant, the organization of the outer walls forming the hydrocarbon‐rich matrix of the colonies differed greatly from one sample to another. In the majority of cultivated strains, the colonies were rather small, the different successive external walls remained distinct and all strains contained dienic or trienic hydrocarbons. In contrast, most of the collected samples possessed large colonies with a rather compact matrix formed by the hydrocarbon‐rich part of the successive closely appressed external wall layers. These samples contained polyunsaturated hydrocarbons, i.e. botryococcenes. Well defined cell caps which sheared off the cells were observed only in those strains with a compact matrix. The Austin strain and some collected samples, however, were intermediate with rather small colonies, dense matrix, definite cell caps and dienic hydrocarbons. Thus, the hydrocarbon composition did not correlate directly with the variations in wall structure; however, the occurence of dienic and botryococcene‐like hydrocarbons together in one strain was never observed, although analyzed at various stages of growth. Thus, the existence of distinct strains of Botryococcus braunii, some synthesizing dienes, others botryococcenes, appears highly probable.