Heterotrophic cell lines

A number of factors have been studied for their influence on nicotine production. Of these the negative effect of auxins, and in particular 2,4-D, on alkaloid production is worth mentioning (202-204,211,220, 225,226,229,255). In root cultures the addition of indoleacetic acid (lAA) also reduces alkaloid production (196). Light was reported to inhibit nicotine formation (50,255). In a green cell suspension, however, increased nicotine levels were found on illumination (229). Ikemeyer and Barz (243) reported that a photoautotrophic cell line of N. tabacum did not produce nicotine, whereas a heterotrophic cell line did accumulate this alkaloid. Elicitation with a preparation of the fungus Phytophthora megasperma did not affect the nicotine levels of these cell lines. Addition of organic acids to the medium resulted in increased alkaloid formation in callus cultures (up to 3.25%) (230). For a review of the various cultural factors which influence secondary metabolism, the reader is referred to Mantell and Smith (255). 

The outlined hypothetical scenario implies that the demise of ZnS mediated photosynthesis tri ered a major separation of the first life forms into (i) the sub-aerial communities dependent on (bacterio)chlorophyll-type photosynthesis as source of reducing equivalents (the future Bacteria) and (ii) the communities confined to the ZnS settings at the sea floor. The dwellers of the sea floor habitats could diversify further. Some of their lineages would evolve by developing new types of metabolism, e.g. chemoautotrophy. Acquisition of cell envelopes would enable their spread into Zn-poor media and give rise to diverse archaeal branches. In contrast, the most conservative line e would remain adherent both to the ancient ZnS milieu and to the primeval, heterotrophic way of life. Only after the... 

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