Genome reduction enhances production of polyhydroxyalkanoate and alginate oligosaccharide in Pseudomonas mendocina.

Pseudomonas mendocina NK-01 previously isolated by our lab is able to accumulate medium-chain-length polyhydroxyalkanoate (mcl-PHA) intracellularly and secrete alginate oligosaccharide (AO) to the extracellular milieu. The present study aimed at investigating whether improved production of mcl-PHA and AO by P. mendocina can be accomplished by genome reduction. In this study, 14 large genomic fragments accounting for 7.7% of the genome of P. mendocina NK-01 were sequentially deleted to generate a series of genome-reduced strains by an upp-based markerless knockout method. As a result, the intracellular ATP/ADP ratio of the strain NKU421 with the largest deletion improved by 11 times compared to NK-01. More importantly, the mcl-PHA and AO yields of NKU421 increased by 114.8% and 27.8%, respectively. Enhancing mcl-PHA and AO production by NKU421 may be attributed to improved transcriptional levels of PHA synthase genes and AO secretion-related genes. The present study suggests that rational reduction of bacterial genome is a feasible approach to construct an optimal chassis for enhanced production of bacterial metabolites. In the future, further reduction of the NKU421 genome can be expected to create high-performance chassis for the development of microbial cell factories.