The cosmopolitan, filamentous brown alga Ectocarpus siliculosus is the first fully-sequenced multicellular alga (Cock et al. 2010) and widely established biological model with a plethora of information about its biochemistry, developmental biology, genetics (including mutants), and pathologies (including fungi, oomycetes and viruses). It is also an important fouling organism on many natural and man-made surfaces in the sea. It can easily be cultured in small volumes of seawater-derived or synthetic media and its full life cycle can be completed in culture within a matter of weeks. As such, it has potential for industrial biotechnology which is nevertheless untapped to date.
Interestingly, its genome annotation has revealed the presence of several putative haloalkane dehalogenases – the first cases found in algal systems. We hypothesize that these haloalkane dehalogenases
(1) facilitate detoxification of chemical defence metabolites produced by other marine organisms on which Ectocarpus commonly lives as an epiphyte;
(2) have biotechnological potential for the degradation of anthropogenic, halogenated pollutants.
Within the framework of this PhD project, we aim to further elucidate the structure and function of brown algal dehalogenases. Specifically, we aim to
(1) elucidate the naturally occurring halometabolites of Ectocarpus and the role of dehalogenases in the degradation (or synthesis);
(2) generate mutants, in which the identified genes are inactivated, and compare the detoxification process among the wild type Ectocarpus and the mutants monitored by LC-MS and GC-MS;
(3) clone and heterologously express these enzymes in Escherichia coli;
(4) study the substrate specificity, kinetics and potential inhibitors of these inhibitors;
(5) explore their biotechnological potential as biocatalysts for the degradation of halogenated pollutants.
We will collaborate with the group of James Naismith (St. Andrews) for the further X-ray structure elucidation of dehalogenases from Ectocarpus, and with the Aberdeen Marine Biodiscovery Centre for the potential commercial development of metabolites and enzymes of biotechnological interest.
Our group has a long-standing track record with Ectocarpus. Significant for this project, we have expertise in its unialgal and axenic culturing, genome annotation (Cock et al. 2010), transcriptomics, elucidation of speciation of its in vivo halogen storage by X-ray absorption spectroscopy and, most recently, its halogen and oxidative metabolism in the context of defense against the oomycete pathogen Eurychasma. We are currently preparing publication of a substantial dataset about the cellular localization of halogens and volatile emissions of halocarbons and molecular iodine (I2). We have also discovered the antioxidant role of iodide in the related kelp Laminaria, impacting atmospheric chemistry, and contributed to the field of algal halogen biochemistry in general (reviewed by Küpper et al. 2011). Dr Deng has 15 years research experience of identification of new halogenated metabolites, elucidation of the functions of halogenases and application of halogenases as biocatalysts (O'Hagan and Deng 2015).
Cock JM et al. (2010) The Ectocarpus genome and the independent evolution of multicellularity in the brown algae Nature 465:617-621
Küpper FC et al. (2011) Commemorating two centuries of iodine research: An interdisciplinary overview of current research Angewandte Chemie - International Edition 50:11598 – 11620
O'Hagan D, Deng H (2015) Enzymatic fluorination and biotechnological developments of the fluorinase Chemical Reviews 115:634-649 doi:10.1021/cr500209t