Biosensor-based isolation of amino acid-producing strains.

The marine bacterium has recently been demonstrated to be a promising new host for molecular biology and next generation bioprocesses. is a Gram-negative, non-pathogenic slight-halophilic bacterium, with a high nutrient versatility and a reported doubling time of under 10 min. However, is not an established model organism yet, and further research is required to promote its transformation into a microbial workhorse. In this work, the potential of as an amino acid producer was investigated. First, the transcription factor-based biosensor LysG, from , was adapted for expression in to facilitate the detection of positively charged amino acids. A set of different biosensor variants were constructed and characterized, using the expression of a fluorescent protein as sensor output. After random mutagenesis, one of the LysG-based sensors was used to screen for amino acid producer strains. Here, fluorescence-activated cell sorting enabled the selective sorting of highly fluorescent cells, potential producer cells. Using this approach, individual L-lysine, L-arginine and L-histidine producers could be obtained producing up to 1 mM of the effector amino acid, extracellularly. Genome sequencing of the producer strains provided insight into the amino acid production metabolism of . This work demonstrates the successful expression and application of transcription factor-based biosensors in and provides insight into the underlying physiology, forming a solid basis for further development of this promising microbe.