Rhizobium leguminosarum bv. viciae 3841 Adapts to 2,4-Dichlorophenoxyacetic Acid with “Auxin-Like” Morphological Changes, Cell Envelope Remodeling and Upregulation of Central Metabolic Pathways

Abstract

There is a growing need to characterize the effects of environmental stressors at the molecular level on model organisms with the ever increasing number and variety of anthropogenic chemical pollutants. The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), as one of the most widely applied pesticides in the world, is one such example. This herbicide is known to have non-targeted undesirable effects on humans, animals and soil microbes, but specific molecular targets at sublethal levels are unknown. In this study, we have used Rhizobium leguminosarum bv. viciae 3841 (Rlv) as a nitrogen fixing, beneficial model soil organism to characterize the effects of 2,4-D. Using metabolomics and advanced microscopy we determined specific target pathways in the Rlv metabolic network and consequent changes to its phenotype, surface ultrastructure, and physical properties during sublethal 2,4-D exposure. Auxin and 2,4-D, its structural analogue, showed common morphological changes in vitro which were similar to bacteroids isolated from plant nodules, implying that these changes are related to bacteroid differentiation required for nitrogen fixation. Rlv showed remarkable adaptation capabilities in response to the herbicide, with changes to integral pathways of cellular metabolism and the potential to assimilate 2,4-D with consequent changes to its physical and structural properties. This study identifies biomarkers of 2,4-D in Rlv and offers valuable insights into the mode-of-action of 2,4-D in soil bacteria.

Correlative atomic force microscopy quantitative imaging-laser scanning confocal microscopy quantifies the impact of stressors on live cells in real-time

“…coli surface 37 is enhanced by bridging, which is more prevalent at higher ionic strengths 38 . Adhesion, even when non-specific, is an important comparative characteristic that reflects the macromolecular arrangement of the cell surface which can impact important physiological processes such as biofilm formation and host cell invasion 9 , 33 , 34 , 39 – 41 .…”

Cinnamomum zeylanicum bark essential oil induces cell wall remodelling and spindle defects in Candida albicans

“…The cell surface biophysical properties of CNB oil treated C. albicans RSY150 and a clinical isolate from blood were analyzed by Quantitative Imaging (QI™) using a Nanowizard III AFM (JPK Instruments, Berlin, Germany) as described previously [ 47 , 48 ]. Briefly, cell suspensions (2.2 × 10 5 cells/mL) from both strains treated either with YPD only (control) or YPD with 1/2 MIC CNB oil for 24 h were deposited onto poly- l -Lysine coated cover slips for 1 h, fixed with formalin and air dried prior to AFM imaging.…”

Exposure to Sub-lethal 2,4-Dichlorophenoxyacetic Acid Arrests Cell Division and Alters Cell Surface Properties in Escherichia coli

“…The herbicide is known to act through a combination of hormonal, oxidative stress and disruptive cell division mechanisms in target plants ( Pazmino et al, 2012 ). It is known to cause membrane defects, disrupt fatty acid biosynthesis, lipid peroxidation, protein synthesis and induce oxidative stress in bacteria ( Chinalia et al, 2007 ; Pazmino et al, 2014 ; Bhat et al, 2015a ). Despite the significant application of this herbicide, its specific effects on non-target species are unknown.…”