Effect of Iron Limitation, Elevated Temperature, and Florfenicol on the Proteome and Vesiculation of the Fish Pathogen Aeromonas salmonicida

Abstract

We analyzed the proteomic response of the Gram-negative fish pathogen A. salmonicida to iron limitation, an elevated incubation temperature, and the antibiotic florfenicol. Proteins from different subcellular fractions (cytosol, inner membrane, outer membrane, extracellular and outer membrane vesicles) were enriched and analyzed. We identified several iron-regulated proteins that were not reported in the literature for A. salmonicida before. We could also show that hemolysin, an oxidative-stress-resistance chaperone, a putative hemin receptor, an M36 peptidase, and an uncharacterized protein were significantly higher in abundance not only under iron limitation but also with an elevated incubation temperature. This may indicate that these proteins involved in the infection process of A. salmonicida are induced by both factors. The analysis of the outer membrane vesicles (OMVs) with and without applied stresses revealed significant differences in the proteomes. OMVs were smaller and contained more cytoplasmic proteins after antibiotic treatment. After cultivation with low iron availability, several iron-regulated proteins were found in the OMVs, indicating that A. salmonicida OMVs potentially have a function in iron acquisition, as reported for other bacteria. The presence of iron-regulated transporters further indicates that OMVs obtained from ‘stressed’ bacteria might be suitable vaccine candidates that induce a protective anti-virulence immune response.

Comparative genomic analysis provides insights into taxonomy and temperature adaption of Aeromonas salmonicida

“…T2SS functions as a transport mechanism to translocate proteins (such as aerolysin, proteases, DNases and amylases) from the periplasm to the extracellular environment in Aeromonas (Li et al, 2011; Seshadri et al, 2006), and the ExeAB homologue GspAB complex has been demonstrated to be functional in the assembly of the T2SS secretin multimer in A. salmonicida (Strozen et al, 2011). The haemolytic genes aerA and hlyA have been found to be significantly up‐regulated in mesophilic A. salmonicida SRW‐OG1 grown at 28 and 37°C compared to 18°C (Chen et al, 2022), and the haemolytic activity of A. salmonicida is enhanced by elevated incubation temperature or limited iron (Chen et al, 2022; Kroniger et al, 2022). It can be thought that these common virulence factors constitute the basic virulence of A. salmonicida .…”

“…salmonicida is enhanced by elevated incubation temperature or limited iron (Chen et al, 2022;Kroniger et al, 2022). It can be thought that these common virulence factors constitute the basic virulence of A. salmonicida.…”

Availability of iron ions impacts physicochemical properties and proteome of outer membrane vesicles released by Neisseria gonorrhoeae

“…For other bacteria, the OMV secretion in environments with different iron availability was demonstrated mainly for iron starvation conditions. For example, Aeromonas salmonicida , Haemophilus influenzae , Vibrio cholerae , Helicobacter pylori , Escherichia coli, and Mycobacterium tuberculosis produce OMVs in iron starvation conditions 7 , 28 – 31 . Data on OMVs released by bacteria in iron repletion conditions are minimal.…”

Outer-Membrane Vesicles of Fusobacterium necrophorum: A Proteomic, Lipidomic, and Functional Characterization

“…Previous studies further showed that iron limitation leads to the activation of numerous virulence genes in many pathogenic bacteria, including N. meningitidis [ 46 ]. In addition, the results of investigations on Aeromonas salmonicida suggest that OMVs produced from limited-iron stressed bacteria are involved in iron acquisition and may be suitable for inducing protective immune responses [ 47 ].…”