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

Abstract

Ethylene and ethylene oxide are widely used in the chemical industry, and ethylene is also important for its role in fruit ripening. Better sensing systems would assist risk management of these chemicals. Here, we characterise the ethylene regulatory system inMycobacteriumstrain NBB4 and use these genetic parts to create a biosensor. The regulatory genesetnR1andetnR2and cognate promoter Petnwere combined with a fluorescent reporter gene (fuGFP) in aMycobacteriumshuttle vector to create plasmid pUS301-EtnR12P. Cultures ofM. smegmatismc2-155(pUS301-EtnR12P) gave a fluorescent signal in response to ethylene oxide with a detection limit of 0.2 µM (9 ppb). By combining the epoxide biosensor cells with another culture expressing the ethylene monooxygenase, the system was converted into an ethylene biosensor. The co-culture was capable of detecting ethylene emission from banana fruit. These are the first examples of whole-cell biosensors for epoxides or aliphatic alkenes. This work also resolves long-standing questions concerning the regulation of ethylene catabolism in bacteria.