Overexpression of mltA in Edwardsiella tarda reduces resistance to antibiotics and enhances lethality in zebra fish

Abstract

Aims: The aim of this study was to investigate the role of membrane‐bound lytic murein transglycosylase A (MltA) in a bacterial fish pathogen Edwardsiella tarda. Methods and Results: An mltA in‐frame deletion mutant (ΔmltA) and an mltA overexpression strain (mltA+) of Edw. tarda were constructed through double‐crossover allelic exchange and by transformation of a low‐copy plasmid carrying the intact mltA into the ΔmltA mutant, respectively. Either inactivation or overexpression of MltA in Edw. tarda resulted in elevated sensitivity to β‐lactam antibiotics and lower viability in oligotrophic or high osmotic environment than wild‐type strain. Autolysis induced by EDTA was reduced in ΔmltA strain, while mltA+ strain was virtually flimsy, indicating that MltA is responsible for the lysis effect. Moreover, mltA+ strain exhibited significant increases in lipopolysaccharide (LPS) biosynthesis and virulence to zebra fish compared with wild‐type strain. Conclusions: The results indicated that MltA plays essential roles in β‐lactam antibiotics and environmental stresses resistance, autolysis, LPS biosynthesis and pathogenicity of Edw. tarda. This is the first report that MltA has a virulence‐related function in Edw. tarda. Significance and Impact of the Study: This study provided useful information for further studies on pathogenesis of Edw. tarda.

Invasin of Edwardsiella tarda is essential for its haemolytic activity, biofilm formation and virulence towards fish

“…This indicates the expression level of invasin might be controlled tightly by complex and multifactorial regulatory mechanisms from the genome (Liu et al . ).…”

“…The qRT-PCR analysis showed that the invasin was excessively expressed in inv + without any extrinsic inducer. This indicates the expression level of invasin might be controlled tightly by complex and multifactorial regulatory mechanisms from the genome (Liu et al 2012).…”

The lytic transglycosylase MltB connects membrane homeostasis and in vivo fitness of Acinetobacter baumannii

“…The contribution of LTs to pathogenesis was recently observed in N. gonorrhoeae, B. abortus and E. tarda (Liu et al, 2012;Bao et al, 2017;Knilans et al, 2017;Ragland et al, 2017). However, the molecular mechanisms connecting LTs to pathogenesis are not well defined, especially in A. baumannii.…”

“…These enzymes are involved in remodeling of the PG layer and releasing PG fragments (1,6-anhydro-muropeptides), and consequently, important for cell wall integrity (Dik et al, 2017). Recently, it was shown that LTs are important for pathogenesis in Neisseria gonorrhoeae, Brucella abortus and Edwardsiella tarda (Bao et al, 2017;Knilans et al, 2017;Liu et al, 2012;Ragland et al, 2017).…”

Loss of membrane‐bound lytic transglycosylases increases outer membrane permeability and β‐lactam sensitivity in Pseudomonas aeruginosa

“…Cells in a biofilm are protected from exposure to many antibiotics by the surrounding extracellular polymeric substance matrix and are heterogeneous with respect to growth rates, with reduced sensitivity in slow-growing or persister subpopulations (Kostakioti et al 2013). Factors affecting cell wall metabolism can modulate bacterial surface properties (Reid et al 2004;Liu et al 2012) and biofilm formation (Monteiro et al 2011;Payne et al 2013;Brambilla et al 2014), altering adhesion to surfaces or the ability to form the protective matrix (Monteiro et al 2011;Liu et al 2014). Therefore, we asked whether the ability of LT mutants to form biofilms was altered.…”