Characterization of a Soil Metagenome-Derived Gene Encoding Wax Ester Synthase

Abstract

A soil metagenome contains the genomes of all microbes included in a soil sample, including those that cannot be cultured. In this study, soil metagenome libraries were searched for microbial genes exhibiting lipolytic activity and those involved in potential lipid metabolism that could yield valuable products in microorganisms. One of the subclones derived from the original fosmid clone, pELP120, was selected for further analysis. A subclone spanning a 3.3 kb DNA fragment was found to encode for lipase/esterase and contained an additional partial open reading frame encoding a wax ester synthase (WES) motif. Consequently, both pELP120 and the full length of the gene potentially encoding WES were sequenced. To determine if the wes gene encoded a functioning WES protein that produced wax esters, gas chromatography-mass spectroscopy was conducted using ethyl acetate extract from an Escherichia coli strain that expressed the wes gene and was grown with hexadecanol. The ethyl acetate extract from this E. coli strain did indeed produce wax ester compounds of various carbon-chain lengths. DNA sequence analysis of the full-length gene revealed that the gene cluster may be derived from a member of Proteobacteria, whereas the clone does not contain any clear phylogenetic markers. These results suggest that the wes gene discovered in this study encodes a functional protein in E. coli and produces wax esters through a heterologous expression system.

Metagenomic Approaches as a Tool to Unravel Promising Biocatalysts from Natural Resources: Soil and Water

“…This category also includes samples from soils with high moisture content, such as alluvial soils from Eulsukdo Island (South Korea) [142,163], soils collected from lakes [64,145] and even soils with a significant salinity content [145,164], mountain soils such as an acid peatland site in Germany [159] and arid areas, namely, soils of the Cerrado region of Brazil [165,166] that present a high clay content, low pH and high iron levels. All these environments have interesting characteristics that give them unique ecosystems with high enzymatic potential.…”

“…Hence, several metagenomic studies were implemented in fields designed for agriculture and/or grasslands, many of them subject to the ploughing and cultivation of different crops. Rhizosphere soils of, for example, red pepper plants and strawberry plants represent a complex but interesting ecosystem due to the symbiosis and parasitism interactions that happen between plants and microorganisms in these soil regions [92,115,142]. Cotton [132], wheat [116,141], sugarcane [83,90,103], corn [81,144], straw [86] and paddy [94,142] fields are examples of agricultural environments from which samples were collected, in particular from topsoil, to be analysed through metagenomic approaches.…”

“…Rhizosphere soils of, for example, red pepper plants and strawberry plants represent a complex but interesting ecosystem due to the symbiosis and parasitism interactions that happen between plants and microorganisms in these soil regions [92,115,142]. Cotton [132], wheat [116,141], sugarcane [83,90,103], corn [81,144], straw [86] and paddy [94,142] fields are examples of agricultural environments from which samples were collected, in particular from topsoil, to be analysed through metagenomic approaches. The selection of topsoil samples and not samples at higher depths is due to the presence of a higher soil microbial biomass on the surface since there is larger evidence of litter composition and root turnover rates in this type of land [149].…”

“…On the other hand, some phosphatases/phytases were identified in samples from European soils. Additionally, the metagenomic studies performed with both European and Asian soil samples showed the presence of other types of enzymes such as RNase [69], rhodanase [70], trehalose synthase [143], sulfatases [145] or wax ester synthase [142]. The soil samples collected in Africa and Antarctica, as well as the marine sediments from the Pacific, Antarctic and Atlantic Oceans, essentially allowed the identification of lipolytic enzymes.…”

“…; Montoya, S. Compost supplementation with nutrients and microorganisms in composting process.Waste Manag. 2017,69,[136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153] [PubMed] 79. Madhuri, R.J.; Saraswathi, M.; Gowthami, K.; Bhargavi, M.; Divya, Y.; Deepika, V. Recent approaches in the production of novel enzymes from environmental samples by enrichment culture and metagenomic approach.…”