Rowland S J, Allard W G, Belt S T, Massé G, Robert J M, Blackburn S, Frampton D, Revill A T, Volkman J K
Petroleum and Environmental Geochemistry Group, Department of Environmental Sciences, Plymouth Environmental Research Centre, University of Plymouth, Drake Circus, PL4 8AA, Plymouth, UK.
Phytochemistry. 2001 Nov;58(5):717-28. doi: 10.1016/s0031-9422(01)00318-1.
Polyunsaturated highly branched isoprenoid (HBI) hydrocarbon distributions of laboratory cultures of five strains of the planktonic diatom Rhizosolenia setigera (Brightwell) are shown herein to be highly variable. Some strains produced both haslenes with from three to five double bonds and rhizenes. The haslenes comprised not only Delta5 alkenes but also those with C7(20) unsaturation, including hasla-7(20),9E,Z, 23-trienes and hasla-7(20),9E,Z-13, 23-tetraenes. The rhizenes contained C7(25) unsaturation and the vinyl moiety common to all algal haslenes so far characterised. The effects of temperature and salinity on HBI composition, along with isotopic content, were determined in strain CS 389/A. Increase in growth temperature from 18 to 25 degrees C increased the degree of unsaturation in the haslenes and E to Z isomerisation in the triene. There was also an increase in unsaturation in the rhizenes at the highest growth temperature, with hexaenes dominant over the pentaenes but in the rhizenes, Z to E isomerisation increased. Increased salinity from 15 to 35 psu increased cell growth and rhizene production but decreased haslene production. Unsaturation in haslenes was not changed by increased salinity but unsaturation in the rhizenes decreased. These may reflect growth rate differences. The carbon isotopic compositions of the haslenes and rhizenes were similar to that of the major sterol at 18 degrees C, but the major HBI isomers were 3-4 per mil depleted relative to phytol released by saponification from chlorophyll a. This suggests biosynthesis of HBIs from a different isotopic pool of isopentenyl biphosphate to that from which phytol is biosynthesised. At 25 degrees C, further isotopic differences were observed. The variables controlling HBI distributions in R. setigera are still not fully understood and rationalisation of the environmental controls on the sedimentary distributions of the HBIs from R. setigera may only be possible once such factors are established.
本文展示了五株浮游硅藻根管藻（Rhizosolenia setigera，布赖特韦尔）实验室培养物的多不饱和高度支链异戊二烯（HBI）烃分布具有高度变异性。一些菌株既产生了具有三到五个双键的哈斯烯，也产生了根管烯。哈斯烯不仅包括Δ5烯烃，还包括具有C7(20)不饱和度的那些，包括哈斯拉-7(20),9E,Z,23-三烯和哈斯拉-7(20),9E,Z-13,23-四烯。根管烯含有C7(25)不饱和度以及迄今为止所表征的所有藻类哈斯烯共有的乙烯基部分。在菌株CS 389/A中测定了温度和盐度对HBI组成以及同位素含量的影响。生长温度从18℃升高到25℃会增加哈斯烯中的不饱和度以及三烯中的E到Z异构化。在最高生长温度下，根管烯中的不饱和度也有所增加，六烯比五烯占主导地位，但在根管烯中，Z到E异构化增加。盐度从15 psu增加到35 psu会增加细胞生长和根管烯的产生，但会减少哈斯烯的产生。盐度增加不会改变哈斯烯中的不饱和度，但会降低根管烯中的不饱和度。这些可能反映了生长速率差异。哈斯烯和根管烯的碳同位素组成在18℃时与主要甾醇相似，但主要的HBI异构体相对于通过皂化从叶绿素a释放的植醇贫化3-4‰。这表明HBI的生物合成来自异戊烯基二磷酸的不同同位素库，与植醇的生物合成来源不同。在25℃时，观察到了进一步的同位素差异。控制根管藻中HBI分布的变量仍未完全理解，只有在确定这些因素后，才有可能对根管藻HBI在沉积物中的分布的环境控制进行合理化解释。
