EGU2020-19304
https://doi.org/10.5194/egusphere-egu2020-19304
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Developing 3D polymer nanostructured fabric as a soil-like model for studying interactions between microorganisms and soil structure - The case of bacterial biofilm development

Fabrizio De Cesare1,3, Elena Di Mattia2, and Antonella Macagnano1,3
Fabrizio De Cesare et al.
  • 1University of Tuscia, Department for Innovation in Biological, Agro-food and Forest Systems (DIBAF), Viterbo, Italy (decesare@unitus.it)
  • 2University of Tuscia, Department of Agriculture and Forest Sciences (DAFNE), Viterbo, Italy (dimattia@unitus.it)
  • 3National Research Council (CNR), Institute of Atmospheric Pollution Research (IIA), Monterotondo (RM), Italy (antonella.macagnano@cnr.it)

Soil structure is the organisation of soil particles in aggregates with increasing hierarchical levels, from nano- to macro-architectures. Several processes and the functioning of the entire soil ecosystem fundamentally depends on soil structure. Soil is also a very heterogeneous and complex matrix to study because of several components with different nature (mineral, organic and biological), physics and chemistry comprise it. Its study often involves techniques that profoundly alter its natural composition or destroy its original 3D arrangement, including the pore distribution and organisation, which is crucial in preserving a suitable habitat for soil ecology and functioning.

Microbial life has been discovered in the last decades to exist in biofilms, 3D spatial organisations of microbial communities adhering to solid surfaces. In these well-organised assemblages of one or more different microbial species, extracellular polymeric substances (EPS) play remarkable functions for microorganisms in biofilms and facilitate aggregation of soil particles.

As a model system, a self-standing polymer biodegradable nanostructured scaffolds (NS) composed of a mixture of nano- to microfibres and microbeads mimicking the fibrous materials and particles comprising the main morphological types of soil (organic matter and mineral particles) and the relative spatial architecture at the micro- and nanoscale were created by electrospinning. Electrospinning is a nanotechnology producing 2D and 3D nano- and microfibrous scaffolds under an electric field. The resulting NS were characterised by considerable porosity and extensive surface area. A PGPR species was employed as a model microbial type to test the capacity of similar NS of supporting the biofilm development. Incubation was performed under stirring to stimulate only stable interactions between microorganisms and the various morphological types of the NS, and also to assess the stability of the NS mimicking the soil aggregates. To shed some light into the nexus between microorganisms and soil structure and the reciprocal influence, combination of imaging techniques such as optical, SEM and TEM microscopy were used to observe “in situ” associations of microbes with mineral and organic materials at nano- and microscale and the consequent effects on porosity usually destroyed under investigations.

The typical phases of conditioning film release, initial and stable adhesion mediated by appendages and EPS release, micro- and macrocolony formation until a mature biofilm development were observed. Morphological modifications of bacteria and the involvement of other components in the mentioned stages were also detected. The bacteria growth rate, the overall respiratory activity and its spatial distribution throughout the NS were recorded.

Hence, the tools here proposed can have high potentials in reproducing the spatial and temporal dynamics of microbial hotspots of activity typically present in the rhizosphere, the sphere of soil surrounding roots, which is of central importance for the entire soil ecosystem functioning. 

Similar 3D NS can also provide the opportunity of zooming in microbial lifestyle observing microbes at work, from the dynamics of interactions with organic matter and particle surfaces to their spatial distribution and colony formation, then linking biological processes to specific physical and chemical features of soil at different scales (from nm to mm).

How to cite: De Cesare, F., Di Mattia, E., and Macagnano, A.: Developing 3D polymer nanostructured fabric as a soil-like model for studying interactions between microorganisms and soil structure - The case of bacterial biofilm development, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19304, https://doi.org/10.5194/egusphere-egu2020-19304, 2020

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Presentation version 2 – uploaded on 06 May 2020
Version description: Added annotation about author's copyright retainment (author's rights reserved) and modifications of Conclusions[...]
  • AC1: Comment on EGU2020-19304, Fabrizio De Cesare, 06 May 2020

    A soil-like 3D nanostructured framework providing a more “natural” environment for soil microorganisms was here proposed permitting to zoom in the microbial lifestyle and phenotypical traits expressed by microbes at work in distinct contexts and related to specific microhabitat features at different scales (from mm down to nm) and fixing the basis for the development of innovative tools for various applications.

  • CC1: Comment on EGU2020-19304, Andreas Pohlmeier, 07 May 2020

    Hello Fabrizio,

    Interesting technique for disentanglement of complex soil structures!

    1) What type of polymer did you use. Is it hydrophilic or hydrophobic?

    2) does surface chemistry affect the biofilm growth/attachment?

    Cheers,

    Andreas Pohlmeier

    • AC2: Reply to CC1, Fabrizio De Cesare, 07 May 2020

      Hi Andreas,

      Thanks for your interest in my work.

      Going to your questions:

      1. I reported the polymer info in the session discussion. Anyway, it is polycaprolactone; basically, it is a hydrophobic polymer, but its hydrophobicity can change depending on the final structure it has. In our case, the initial hydrophobicity was strongly reduced after deposition by electrospinning and formation of the nanofibre-microbead structure. Additionally, when surface materials come in contact with bacteria (or vice-versa if you prefer) the surface properties of materials are modified due to the presence in the environment of organic compounds (also in water ecosystems) or that can be produced and released on purpose by bacterial species to facilitate the following adhesion of cells. In our case, the hydrophobicity changed into hydrophilicity because of the presence of a conditioning film on the nano-/microstructures.
      2. The answer depends on the previous one. Frequently, it is reported that surface chemistry of materials drives the following adhesion of bacteria and biofilm development, facilitating or hindering. However, most of these studies were performed in specific incubations in the lab in the absence of external organic compounds possibly generating a CF. These studies are then unreliable because unnatural, in my opinion. I haven't found yet a study where the organic matter in the media was present and where the original material chemistry resulted relevant for bacterial binding. Oppositely, other studies have reported that the presence of CF makes the original chemistry of surfaces irrelevant. Nevertheless, future studies could demonstrate that I’m wrong.

      I hope I fulfilled your requests.

      If you are interested, I provided my recent publications on this issue in the session discussion. If you missed them, please write to me again, I’ll be glad to supply you (maybe by email is better).

      Thanks,

      Fabrizio

Presentation version 1 – uploaded on 05 May 2020
  • AC1: Comment on EGU2020-19304, Fabrizio De Cesare, 05 May 2020

    A soil-like 3D nanostructured framework providing a more “natural” environment for soil microorganisms was here proposed permitting to zoom in the microbial lifestyle and phenotypical traits expressed by microbes at work in distinct contexts and related to specific microhabitat features at different scales (from mm down to nm) and fixing the basis for the development of tools for various applications.