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Toxic accumulation of LPS pathway intermediates underlies the essentiality of LpxH in Acinetobacter baumannii ATCC19606

Richie, Daryl and Takeoka, Ken and Bojkovic, Jade and Rath, Christopher and Sawyer, William and Wei, Jun-Rong and Dean, Charles (2016) Toxic accumulation of LPS pathway intermediates underlies the essentiality of LpxH in Acinetobacter baumannii ATCC19606. PLOS one, 11 (8). pp. 1-22. ISSN 1932-6203

Abstract

Acinetobacter baumannii ATCC 19606 tolerates loss of lipopolysaccharide (LPS) caused by inactivation of early LPS pathway genes. However, mutations in pathway genes encoding steps downstream of LpxD have not been reported, implying that later biosynthetic steps may be essential for viability. Here, we determined if LpxH, the UDP-2,3-diacylglucosamine hydrolase that generates UMP-2,3-diacylglucosamine 1-phosphate (lipid X), was essential in A. baumannii ATCC 19606. Multiple attempts to disrupt lpxH on the genome were unsuccessful. When expression of LpxH was placed under control of an isopropyl β-D-1-thiogalactopyranoside (IPTG) inducible promoter, the cells failed to grow under standard laboratory conditions without IPTG induction. Growth under LpxH depletion conditions (-IPTG) was rescued by chemical inhibition of LpxC, upstream of LpxH, indicating that toxic accumulation of LPS pathway intermediates underlies LpxH essentiality. Consistent with this, the levels of LpxH substrate (product of LpxD) and a C14:0(3-OH) acyl variant of the LpxD substrate had accumulated in cells that were depleted of LpxH causing a growth defect. Intriguingly, under these partial depletion conditions, there was also a smaller but reproducible accumulation of the downstream pathway intermediates disaccharide 1-monophosphate and lipid IVA suggesting a complex downstream response to LpxH depletion.

Item Type: Article
Date Deposited: 17 Aug 2016 00:45
Last Modified: 17 Aug 2016 00:45
URI: https://oak.novartis.com/id/eprint/29005

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