Functionality of Root-Associated Bacteria along a Salt Marsh Primary Succession

Area of Science:

• Microbiology
• Plant Science
• Ecology

Background:

• Plant-associated bacteria exhibit diverse functional traits crucial for plant establishment in challenging environments.
• Salt marshes present unique ecological conditions shaped by soil development over time, influencing microbial communities.
• Understanding bacterial functional traits is key to comprehending plant-microbe interactions and ecosystem dynamics.

Purpose of the Study:

• To assess the response of plant-associated bacterial functional traits to soil type, plant species, and plant compartment.
• To investigate bacterial adaptation and functional diversity across a 100-year salt marsh soil chronosequence.
• To identify specific bacterial genera with plant growth-promoting capabilities in salt marsh ecosystems.

Main Methods:

• Isolation and characterization of 808 bacterial colonies from rhizosphere soil and root endosphere of *Limonium vulgare* and *Artemisia maritima*.
• Screening of 59 selected strains for plant growth-promoting traits, stress resistance (antibiotic, abiotic), and metabolic potential.
• Multivariate analysis to determine the influence of soil type, plant species, and plant compartment on bacterial functional traits.

Main Results:

• Bacterial functional trait distribution was primarily driven by soil type, with late-successional soils showing restricted functional diversity.
• Plant endophyte functionality remained consistent across succession, indicating a plant-driven effect, while rhizosphere isolates responded to soil type.
• Specific *Pseudomonas* and *Serratia* strains demonstrated high antibiotic/abiotic stress resistance and significant siderophore production.

Conclusions:

• Soil type significantly impacts rhizosphere bacterial functionality, particularly antibiotic resistance, but not endophyte functionality.
• Plant species exert a strong influence on the functional traits of root endophytes, independent of soil succession stage.
• The study highlights the adaptive capacity of salt marsh bacteria and identifies key genera with potential for plant growth promotion.