Biodegradation of Free Phytol by Bacterial Communities Isolated from Marine Sediments under Aerobic and Denitrifying Conditions

Abstract

Biodegradation of (E)-phytol [3,7,11,15-tetramethylhexadec-2(E)-en-1-ol] by two bacterial communities isolated from recent marine sediments under aerobic and denitrifying conditions was studied at 20°C. This isoprenoid alcohol is metabolized efficiently by these two bacterial communities via 6,10,14-trimethylpentadecan-2-one and (E)-phytenic acid. The first step in both aerobic and anaerobic bacterial degradation of (E)-phytol involves the transient production of (E)-phytenal, which in turn can be abiotically converted to 6,10,14-trimethylpentadecan-2-one. Most of the isoprenoid metabolites identified in vitro could be detected in a fresh sediment core collected at the same site as the sediments used for the incubations. Since (E)-phytenal is less sensitive to abiotic degradation at the temperature of the sediments (15°C), the major part of (E)-phytol appeared to be biodegraded in situ via (E)-phytenic acid. (Z)- and (E)-phytenic acids are present in particularly large quantities in the upper section of the core, and their concentrations quickly decrease with depth in the core. This degradation (which takes place without significant production of phytanic acid) is attributed to the involvement of alternating β-decarboxymethylation and β-oxidation reaction sequences induced by denitrifiers. Despite the low nitrate concentration of marine sediments, denitrifying bacteria seem to play a significant role in the mineralization of (E)-phytol.

Degradation of naphthenic acids by sediment micro-organisms

“…This implies that NAs belonging to the Z ¼ )4 family are not degraded via b-oxidation, because b-oxidation is a widely available catabolic pathway under aerobic and anaerobic conditions. For example Rontani et al (1999) found that two different bacterial communities isolated from marine sediments under aerobic and denitrifying conditions were able to completely mineralize (E)-phytol (3,7,11,15-tetramethylhexadec-2(E)-en-1-ol) and that in both cases the mineralization occurred by alternating b-decarboxymethylation and b-oxidation. A possible mechanism for the aerobic biodegradation of bicyclic NA is the b-oxidation of the carboxylated side-chain followed by a decarboxylation reaction to give the bicyclic hydrocarbon, which in turn can be hydroxylated followed by an oxidation reaction to give the corresponding cyclic ketone.…”

Peroxisomal trans‐2‐enoyl‐CoA reductase is involved in phytol degradation

“…, C24:1-CoA were enzymatically synthesized from the corresponding saturated CoA esters using acyl-CoA oxidase from Arthrobacter (Sigma-Aldrich). A mixture of cis-and trans-phytenic acid was synthesized as described previously [9]. A mixture of cis-and trans-phytenoyl-CoA isomers was chemically synthesized from this mixture as described before [10].…”

Microbial life under ice: Metagenome diversity and in situ activity of Verrucomicrobia in seasonally ice‐covered Lakes

“…The phytanic acid-rich particles would be available in the water column for consumption by bacteria possessing the α-oxidation pathway Additionally, it is possible that phytol may accumulate in particles that sink into the anoxic hypolimnion of lakes. Since the α-oxidation pathway requires oxygen (through the essential phytanoyl CoA hydroxylase), phytol may accumulate under anoxic conditions, although anaerobic degradation of phytol in sediments has been reported (Rontani et al, 1999). Nevertheless, during breakdown of stratification in autumn, phytol accumulated in the hypolimnion could serve as a carbon reserve supporting microbial metabolism throughout the winter.…”