Structural and functional delineation of aerobactin biosynthesis in hypervirulent Klebsiella pneumoniae

Abstract

Aerobactin, a citryl-hydroxamate siderophore, is produced by a number of pathogenic Gram-negative bacteria to aid in iron assimilation. Interest in this well-known siderophore was reignited by recent investigations suggesting that it plays a key role in mediating the enhanced virulence of a hypervirulent pathotype of (hvKP). In contrast to classical opportunistic strains of, hvKP causes serious life-threatening infections in previously healthy individuals in the community. Multiple contemporary reports have confirmed fears that the convergence of multidrug-resistant and hvKP pathotypes has led to the evolution of a highly transmissible, drug-resistant, and virulent "super bug." Despite hvKP harboring four distinct siderophore operons, knocking out production of aerobactin led to a significant attenuation of virulence. Herein, we continue our structural and functional studies on the biosynthesis of this crucial virulence factor. heterologous production and reconstitution of aerobactin biosynthesis from hvKP was carried out, demonstrating the specificity, stereoselectivity, and kinetic throughput of the complete pathway. Additionally, we present a steady-state kinetic analysis and the X-ray crystal structure of the second aerobactin synthetase IucC, as well as describe a surface entropy reduction strategy that was employed for structure determination. Finally, we show solution X-ray scattering data that support a unique dimeric quaternary structure for IucC. These new insights into aerobactin assembly will help inform potential antivirulence strategies and advance our understanding of siderophore biosynthesis.

Hypervirulent Klebsiella pneumoniae – clinical and molecular perspectives

“…Aerobactin (luc) has long been appreciated as a critical siderophore system of hvKp , and as such, it has been proposed as an anti‐virulence target . Encoded in just four genes with a relatively simple synthetic pathway , Iuc appears to be the only siderophore system required in hvKp isolates in laboratory experiments, and in mouse models of disease, inactivation of other siderophore systems had minimal effect . However, the occurrence of multiple siderophore systems in hvKp strains suggests siderophore systems in addition to Iuc play important roles in the human host, either in colonization or invasive disease that largely remains to be uncovered.…”

The Iron Tug-of-War between Bacterial Siderophores and Innate Immunity

“…1C [3]. Due to being Lcn2-resistant, aerobactin has been shown to enhance the hypervirulent phenotype of K. pneumoniae in lung infections [43]; likewise, yersiniabactin promotes the virulence of the bubonic plague pathogen, Y. pestis [44]. In addition to these naturally synthesized mixed siderophores, certain bacteria can modify an existing Lcn2-sensitive siderophore into a stealth siderophore as another evasive strategy.…”

Promising bacterial genera for agricultural practices: An insight on plant growth-promoting properties and microbial safety aspects

“…Usually, hydroxamates are more commonly found in neutral to acid environments while catecholates are more commonly found in neutral to alkaline environments (Saha et al, 2013). Several bacterial genera were described to produce siderophores, such as Azotobacter (Baars et al, 2016;McRose et al, 2017;Romero-Perdomo et al, 2017), Azospirillum (Banik et al, 2016), Bacillus (Kesaulya et al, 2018;Pourbabaee et al, 2018), Dickeya (Sandy and Butler, 2011), Klebsiella (Bailey et al, 2018;Zhang et al, 2017), Nocardia (Hoshino et al, 2011), Pantoea (Burbank et al, 2015;Soutar and Stavrinides, 2018), Paenibacillus (Liu et al, 2017), Pseudomonas (Baune et al, 2017;Deori et al, 2018;Pourbabaee et al, 2018), Serratia (Coulthurst, 2014) and Streptomyces (Gáll et al, 2016;Goudjal et al, 2016;Schütze et al, 2014).…”