Evaluating the relationship between photopigment synthesis and 2-methylisoborneol accumulation in cyanobacteria

The relationship between photopigments and the terpene-derived secondary me tabolite, 2-methyliso-borneol (MIB), was analyzed in photoacclimated cultur es of Pseudanabaena articulata Skuja throughout growth, during the diel cyc le, and following chemical-induced inhibition of the isoprenoid pathway, Ac cumulation of MIB coincided with the accumulation of lipophilic and phycobi lin pigments during the early to mid-exponential portion of the growth cycl e with the greatest accumulation of MIB during the late-exponential phase, Cellular release of MIB occurred as culture populations entered mid- to lat e-logarithmic phase of growth and was greatest in irradiance-stressed cultu res. The greater correspondence of MIB accumulation with photopigments was seen in cultures transferred from a 12:12 h LD photoperiod alone and the co nsistent relationship between MIB and photopigment accumulation under varyi ng irradiance suggested a photopigment-dependent regulation for MIB synthes is. However, the consistent allocation of carbon into MIB during instances of phytofluene and tetrapyrrole biosynthetic inhibition within P. articulat a and Oscillatoria perornata Skuja indicated that MIB accumulation is not L imited by isopreniod-carbon availability and does not appear to serve as an "overflow" product. Rather, MIB accumulation simply appears to reflect ove rall carbon accumulation resulting from increased cell metabolism.