Identification of two secondary acyltransferases of lipid A in Pseudomonas putida KT2442

Engineering Pseudomonas putida for efficient aromatic conversion to bioproduct using high throughput screening in a bioreactor

Pseudomonas putida KT2440 is an emerging biomanufacturing host amenable for use with renewable carbon streams including aromatics such as para-coumarate. We used a pooled transposon library disrupting nearly all (4,778) non-essential genes to characterize this microbe under common stirred-tank bioreactor parameters with quantitative fitness assays. Assessing differential fitness values by monitoring changes in mutant strain abundance identified 33 gene mutants with improved fitness across multiple stirred-tank bioreactor formats. Twenty-one deletion strains from this subset were reconstructed, including GacA, a regulator, TtgB, an ABC transporter, and PP_0063, a lipid A acyltransferase. Thirteen deletion strains with roles in varying cellular functions were evaluated for conversion of para-coumarate, to a heterologous bioproduct, indigoidine. Several mutants, such as the ΔgacA strain improved fitness in a bioreactor by 35 fold and showed an 8-fold improvement in indigoidine production (4.5 g/L, 0.29 g/g, 23% of maximum theoretical yield) from para-coumarate as the carbon source.

Identification of four secondary acyltransferases for lipid A biosynthesis in Vibrio parahaemolyticus

In this study, four genes encoding secondary acyltransferases of lipid A in Vibrio parahaemolyticus ATCC33846 were identified. When the four genes were overexpressed in Escherichia coli MLK1067 that which produces the penta-acylated lipid A lacking the secondary acylation at the C3' position, a C_12:0 secondary acyl chain was added at the C3' position of lipid A only in E. coli overexpressing VP_RS01045, but not VP_RS00880, VP_RS08405, or VP_RS12170. When the four genes were overexpressed in E. coli MKV15b that produces lipid IV_A , a C_12:0 secondary acyl chain was again added at the C3' position in E. coli overexpressing VP_RS01045, but a C_14:0 secondary acyl chain was added at the C2' position of lipid A in E. coli overexpressing VP_RS00880, VP_RS08405, or VP_RS12170. The results indicate that four acyltransferases of lipid A are encoded by VP_RS01045, VP_RS00880, VP_RS08405, or VP_RS12170 in V. parahaemolyticus. The acyltransferase encoded by VP_RS01045 adds a C_12:0 secondary acyl chain at the C3' position of lipid A, whereas the acyltransferase encoded by VP_RS00880, VP_RS08405, or VP_RS12170 adds a C_14:0 secondary acyl chain at the C2' position of lipid A. This work contributes to understanding the biosynthetic pathway of lipid A in V. parahaemolyticus.