Phosphonates: The Good, The Bad, and The Biodegradable

Organophosphonates are ancient molecules that contain the chemically stable C–P bond, which is considered a relic of the reducing atmosphere on primitive earth. Synthetic phosphonates now have a wide range of applications in the agricultural, chemical and pharmaceutical industries. However, the existence of C–P compounds as contemporary biogenic molecules was not discovered until 1959, with the identification of 2‐aminoethyl‐ phosphonic acid in rumen protozoa.

The biochemistry and genetics of C–O–P metabolism have been the subject of intensive research for many decades. However, on the primitive Earth, where oxygen concentrations were most probably very low, organophosphonates might have predominated. Indeed, their detection among the numerous organic compounds brought to Earth on the Murchison meteorite in 1969 points to their likely prebiotic origins.

In recent years, there has been increased recognition of the importance of these chemical fossils both as alternative nutrient sources for organisms in oligotrophic environments, such as some oceanic gyres, and in their diverse commercial applications as insecticides, herbicides, fungicides, water additives, antibiotics and nerve gases. Characteristically, phosphonates are more resistant to chemical hydrolysis, thermal decomposition, enzymatic degradation and photolysis than congeneric compounds containing the more reactive N–P, S–P or O–P linkages.

Microbial phosphonate metabolism is an important area of research, and advances in our understanding of the underpinning biochemistry and genetics have been made in recent years particularly in our own group. However, there is still much to learn for example, the extent to which organophosphonates are utilized as phosphorus sources is still a matter of debate. Biodegradation of organophosphonates is generally accepted to be dependent upon the phosphate status of the cell, and occurring only under conditions of phosphate limitation. In recent years, however, several novel bacteria capable of completely mineralizing both natural and man-made organophosphonates have been isolated and this is the focus of this PhD project.

By way of further example, a synthetic phosphonate of particular interest is Glyphosate, widely used as a herbicide in agriculture, silviculture, urban areas, and domestic gardens. Glyphosate biodegradation has been the subject of intensive research and several glyphosate-degrading microorganisms have been isolated. However, to date, only one microbial enzyme known as C-P lyase is acknowledged to drive complete glyphosate mineralization. AMPA, the common metabolite product of glyphosate biodegradation, still possesses the unique C-P bond of phosphonates and thus retains its toxic profile and recalcitrance.

The focus of this doctoral project will be to further investigate the mechanisms of organophosphonate biodegradation, to identify novel proteins central to these processes and to understand more completely their significance in global biogeochemical cycles and their role in sustaining planetary health.

Postgraduate Research applicants who are interested in applying for this fully funded studentship must have applied to Queen’s University Belfast, via the Direct Applications Portal (link below), and submitted all required supporting documents by the closing date: https://dap.qub.ac.uk/portal/user/u_login.php                                                                           

For further information about academic requirements please see below:                      https://www.qub.ac.uk/courses/postgraduate-research/biological-sciences-phd.html