Proteome and Physiological Characterization of Halotolerant Nodule Endophytes: The Case of Rahnella aquatilis and Serratia plymuthica

Abstract

Bacterial endophytes were isolated from nodules of pea and fava bean. The strains were identified and characterized for plant beneficial activities (phosphate solubilization, synthesis of indole acetic acid and siderophores) and salt tolerance. Based on these data, four strains of Rahnella aquatilis and three strains of Serratia plymuthica were selected. To shed light on the mechanisms underlying salt tolerance, the proteome of the two most performant strains (Ra4 and Sp2) grown in the presence or not of salt was characterized. The number of proteins expressed by the endophytes was higher in the presence of salt. The modulated proteome consisted of 302 (100 up-regulated, 202 down-regulated) and 323 (206 up-regulated, 117 down-regulated) proteins in Ra4 and Sp2, respectively. Overall, proteins involved in abiotic stress responses were up-regulated, while those involved in metabolism and flagellum structure were down-regulated. The main up-regulated proteins in Sp2 were thiol: disulfide interchange protein DsbA, required for the sulfur binding formation in periplasmic proteins, while in Ra4 corresponded to the soluble fraction of ABC transporters, having a role in compatible solute uptake. Our results demonstrated a conserved response to salt stress in the two taxonomically related species.

Serratia spp. as plant growth-promoting bacteria alleviating salinity, drought, and nutrient imbalance stresses

“…On the other hand, explanatory studies have emerged showing how halotolerant strain responds to salinity at the level of the proteome. ACC deaminase-producing S. plymuthica Sp2 was molecularly studied using a proteomic approach ( Novello et al, 2022 ). Overall, the study revealed that the levels of proteins involved in salt stress responses (4.4% NaCl) were increased, while the levels of proteins involved in metabolism and strand structure were decreased.…”

“…Overall, the study revealed that the levels of proteins involved in salt stress responses (4.4% NaCl) were increased, while the levels of proteins involved in metabolism and strand structure were decreased. The main proteins with increased expression in the Sp2 proteome were DsbA, ATP, Porin OmpA, Porin OmpC, and LpoB ( Novello et al, 2022 ).…”

Rhizosphere Bacterial Isolation from Indigenous Plants in Arid and Semi-Arid Algerian Soils: Implications for Plant Growth Enhancement

“…Bacterial strain identification was performed using mass spectrometry MALDI (Matrix-Assisted Laser Desorption/Ionization) and TOF/TOF (UltrafleXtreme, Bruker, Billerica, MA, USA), as reported by Novello et al [21]. A fresh bacterial colony grown on TSA was spotted in triplicate on an MTP 384 target plate (Bruker Daltonics, Milan, Italy).…”

“…The minimal inhibitory concentration (MIC) of sodium chloride was determined by microplate assay, as reported by Novello et al [21]. In detail, NaCl (Fluka) was dissolved in Tryptic Soy Broth (TSB, Sigma, Burlington, MA, USA) until a concentration of 28.8%.…”

Understanding the mechanisms of halotolerance in members of Pontixanthobacter and Allopontixanthobacter by comparative genome analysis

“…In the exoproteome of the halotolerant bacterium Tistlia consotensis grown at high salinity, proteins associated with osmosensing, exclusion of Na + and transport of compatible solutes, such as glycine betaine or proline are abundant ( Rubiano-Labrador et al, 2015 ). Similarly, the proteomic analysis of halotolerant nodule endophytes, Rahnella aquatilis strain Ra4 and Serratia plymuthica strain Sp2 identified that different trans-membrane ABC transporters (ATP-binding cassettes) were the most represented among the up-regulated proteins in response to salt stress ( Novello et al, 2022 ). Moreover, the proteome comparison of halotolerant bacterium Staphylococcus aureus under different osmotic stress conditions revealed the differentially expressed proteins (DEPs) involved in fatty acid synthesis, proline/glycine betaine biosynthesis and transportation, stress tolerance, cell wall biosynthesis, and the TCA cycle, which may contribute to the osmotic stress tolerance of S. aureus ( Ming et al, 2019 ).…”