Aerobic bacterial metabolism of phytol in seawater: effect of particle association on an abiotic intermediate step and its biogeochemical consequences

The biodegradation of phytol by a bacterial community isolated from the oxi c zone of a Recent temperate marine sediment was studied in the presence, a nd in the absence, of a solid support. Analyses of isoprenoid wax esters pr oduced by condensation of bacterial metabolites with themselves, or with ph ytol, showed that bacterial metabolism of phytol was strongly modified in t he presence of the solid support. Aerobic metabolism of phytol involves the transient production of(E)-phytenal, which in turn can be quickly abiotica lly converted to 6,10,14-trimethylpentadecan-2-one or (E)-phytenic acid. So rption on mineral particles appears to hinder the addition of water to the activated double bond of(E)-phytenal, which constitutes the first step of i ts transformation to the Cls isoprenoid ketone. Consequently, it is conclud ed that in surface temperate sediments phytol must be metabolised mainly vi a (E)-phytenic acid and that results obtained from in vitro experiments wit h free cell cultures may not be comparable to processes occuring in marine sedimentary environments. (C) 2000 Elsevier Science Ltd. All rights reserve d.