Synthetic Biology Approaches to Hydrocarbon Biosensors: A Review

Abstract

Monooxygenases are a class of enzymes that facilitate the bacterial degradation of alkanes and alkenes. The regulatory components associated with monooxygenases are nature’s own hydrocarbon sensors, and once functionally characterised, these components can be used to create rapid, inexpensive and sensitive biosensors for use in applications such as bioremediation and metabolic engineering. Many bacterial monooxygenases have been identified, yet the regulation of only a few of these have been investigated in detail. A wealth of genetic and functional diversity of regulatory enzymes and promoter elements still remains unexplored and unexploited, both in published genome sequences and in yet-to-be-cultured bacteria. In this review we examine in detail the current state of research on monooxygenase gene regulation, and on the development of transcription-factor-based microbial biosensors for detection of alkanes and alkenes. A new framework for the systematic characterisation of the underlying genetic components and for further development of biosensors is presented, and we identify focus areas that should be targeted to enable progression of more biosensor candidates to commercialisation and deployment in industry and in the environment.

Development of a whole-cell biosensor for ethylene oxide and ethylene

“…Bacterial MO's are typically inducible by the initial hydrocarbon substrate or a downstream metabolite; this is a sensible strategy for the host cell given both the exotic nature of the substrates and the physiological stress of MO expression 9 . In the alkane-oxidising bacteria, regulatory systems controlling MO expression are well-characterised, and many have been developed into biosensors for alkanes or their metabolites [10][11][12][13][14][15][16][17][18][19][20][21][22][23] ; this research field has been recently reviewed 24 . In contrast, the regulation of alkene oxidation in bacteria has not been well-studied; some regulatory genes [25][26][27] and inducers [28][29][30] have been identified or predicted, but rigorous evidence for specific interactions between inducers, regulatory proteins and promoters has not been presented to date, limiting the development of this biotechnology.…”

Development of a whole‐cell biosensor for ethylene oxide and ethylene

“…Bacterial MO's are typically inducible by the initial hydrocarbon substrate or a downstream metabolite; this is a sensible strategy for the host cell given both the exotic nature of the substrates and the physiological stress of MO expression (Leak et al., 2009 ). In the alkane‐oxidising bacteria, regulatory systems controlling MO expression are well characterised, and many have been developed into biosensors for alkanes or their metabolites (Dietrich et al., 2013 ; Grant et al., 2014 ; Jaspers et al., 2001 ; Kumari et al., 2011 ; Lehtinen et al., 2017 ; Li et al., 2013 ; Minak‐Bernero et al., 2004 ; Reed et al., 2012 ; Santala et al., 2012 ; Sevilla et al., 2017 ; Sticher et al., 1997 ; Wu et al., 2015 ; Zhang et al., 2011 , 2012 ); this research field has been recently reviewed (Moratti et al., 2022 ). In contrast, the regulation of alkene oxidation in bacteria has not been well studied; some regulatory genes (Broberg & Clark, 2010 ; Coleman et al., 2011 ; Mattes et al., 2010 ) and inducers (Dawson et al., 2020 ; Ensign, 1996 ; Mattes et al., 2007 ) have been identified or predicted, but rigorous evidence for specific interactions between inducers, regulatory proteins and promoters has not been presented to date, limiting the development of this biotechnology.…”