Encounters at the microscale: Unraveling soil microbial interactions with nanoplastics
(2023)- Abstract
- Nanoplastics (NPs) originated from plastic residues can interact with soil microorganisms with potential negative effects to their functions. Therefore, I aimed to investigate soil microbial population dynamics when exposed to different NP polymers and concentrations. I used microfluidics technology to produce a soil micromodel – a soil chip - comprising basic pore geometries where microorganisms can live and interact with their surroundings.
First (Paper I), I analyzed the effect of different concentrations (0, 0.5, 2, and 10 mg/L) of engineered NP spheres on the bacterium Pseudomonas putida and the fungus Coprinopsis cinerea incubated in soil chips. I found that both species exhibited stress response, resulting in biomass... (More) - Nanoplastics (NPs) originated from plastic residues can interact with soil microorganisms with potential negative effects to their functions. Therefore, I aimed to investigate soil microbial population dynamics when exposed to different NP polymers and concentrations. I used microfluidics technology to produce a soil micromodel – a soil chip - comprising basic pore geometries where microorganisms can live and interact with their surroundings.
First (Paper I), I analyzed the effect of different concentrations (0, 0.5, 2, and 10 mg/L) of engineered NP spheres on the bacterium Pseudomonas putida and the fungus Coprinopsis cinerea incubated in soil chips. I found that both species exhibited stress response, resulting in biomass reduction. Remarkably, fungal hyphae adsorbed most of the nanospheres at the highest concentration, resulting in a decrease of NPs in the pore space. This led to a recovery of fungal growth at the end of the experiment.
Second (Paper II), I examined the suitability of soil chips for studying the population dynamics of major soil microbial groups (e.g. bacteria, protists and fungi). I investigated how varying physicochemical conditions – such as moisture content, nutrient availability, and pore configuration – influence microbial activity from a soil natural inoculum. I found that the colonization of soil bacteria and protists is highly dependent on liquid connectivity and much less on pore structure. Conversely, fungal colonization is highly influenced by pore structure. Furthermore, I showed that fungal dispersal promoted liquid filling in air-filled pore spaces, which increased bacterial and protist dispersal within these microenvironments.
Third (Paper III), after confirming a successful soil microbial colonization of the chips, I used engineered NPs (0, 0.5, 1, and 2mg/L) to analyze their effect on soil microbial communities. I found that all microbial groups interacted with the nanospheres, the particles either adhered to the cell surface, colonies, or entered the cells. Moreover, NPs and soil particles aggregated over time. The microbial communities behaved very dynamically and the nanospheres caused only temporary effects. Specifically, bacterial populations responded positively to increasing NP concentrations during the initial days. Protists’ populations were highly variable across all treatments, and fungal populations were overall scarce but exhibited a negative impact after four weeks of NP exposure.
Finally, (Paper IV), I examined if the soil model bacterium P. putida also exhibits a negative response when exposed to low doses (~2 mg/L) of nanoplastics (polystyrene – PS, polypropylene – PP, and polyethylene terephthalate – PET), produced by mechanical breakdown of daily plastic products. In parallel, I incubated the bacteria in wells to analyze their metabolic responses via transcriptomic analysis. I found that in the chips there was a reduction in bacterial biomass when exposed to PS and PP, but not to PET. Conversely, bacteria incubated in wells did not exhibit any negative response in growth or in gene expression, except for the PS treatment, which displayed a slight increase in bacterial growth and changes in gene expression potentially related to plastic degradation.
In conclusion, this thesis demonstrates that low NP doses can inhibit microbial growth, but this effect depends on microbial communities and nanoparticle interactions with the environment.
(Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/3769c2f1-a996-4876-b9ec-50606376662b
- author
- Mafla-Endara, P. Micaela LU
- supervisor
-
- Edith Hammer LU
- Pelle Ohlsson LU
- Martijn van Praagh LU
- Milda Pucetaite LU
- opponent
-
- Professor Y. Wick, Lukas, UFZ Leipzig
- organization
- publishing date
- 2023-10-23
- type
- Thesis
- publication status
- published
- subject
- keywords
- Microfluidic devices, Nanoplastics, Soil microorganisms, Toxicity
- pages
- 199 pages
- publisher
- Media-Tryck, Lund University, Sweden
- defense location
- Blå hallen
- defense date
- 2023-11-17 10:00:00
- ISBN
- 978-91-8039-855-8
- 978-91-8039-856-5
- language
- English
- LU publication?
- yes
- id
- 3769c2f1-a996-4876-b9ec-50606376662b
- date added to LUP
- 2023-10-26 11:11:51
- date last changed
- 2023-10-30 08:36:05
@phdthesis{3769c2f1-a996-4876-b9ec-50606376662b,
abstract = {{Nanoplastics (NPs) originated from plastic residues can interact with soil microorganisms with potential negative effects to their functions. Therefore, I aimed to investigate soil microbial population dynamics when exposed to different NP polymers and concentrations. I used microfluidics technology to produce a soil micromodel – a soil chip - comprising basic pore geometries where microorganisms can live and interact with their surroundings. <br/><br/>First (Paper I), I analyzed the effect of different concentrations (0, 0.5, 2, and 10 mg/L) of engineered NP spheres on the bacterium Pseudomonas putida and the fungus Coprinopsis cinerea incubated in soil chips. I found that both species exhibited stress response, resulting in biomass reduction. Remarkably, fungal hyphae adsorbed most of the nanospheres at the highest concentration, resulting in a decrease of NPs in the pore space. This led to a recovery of fungal growth at the end of the experiment. <br/><br/>Second (Paper II), I examined the suitability of soil chips for studying the population dynamics of major soil microbial groups (e.g. bacteria, protists and fungi). I investigated how varying physicochemical conditions – such as moisture content, nutrient availability, and pore configuration – influence microbial activity from a soil natural inoculum. I found that the colonization of soil bacteria and protists is highly dependent on liquid connectivity and much less on pore structure. Conversely, fungal colonization is highly influenced by pore structure. Furthermore, I showed that fungal dispersal promoted liquid filling in air-filled pore spaces, which increased bacterial and protist dispersal within these microenvironments. <br/><br/>Third (Paper III), after confirming a successful soil microbial colonization of the chips, I used engineered NPs (0, 0.5, 1, and 2mg/L) to analyze their effect on soil microbial communities. I found that all microbial groups interacted with the nanospheres, the particles either adhered to the cell surface, colonies, or entered the cells. Moreover, NPs and soil particles aggregated over time. The microbial communities behaved very dynamically and the nanospheres caused only temporary effects. Specifically, bacterial populations responded positively to increasing NP concentrations during the initial days. Protists’ populations were highly variable across all treatments, and fungal populations were overall scarce but exhibited a negative impact after four weeks of NP exposure. <br/><br/>Finally, (Paper IV), I examined if the soil model bacterium P. putida also exhibits a negative response when exposed to low doses (~2 mg/L) of nanoplastics (polystyrene – PS, polypropylene – PP, and polyethylene terephthalate – PET), produced by mechanical breakdown of daily plastic products. In parallel, I incubated the bacteria in wells to analyze their metabolic responses via transcriptomic analysis. I found that in the chips there was a reduction in bacterial biomass when exposed to PS and PP, but not to PET. Conversely, bacteria incubated in wells did not exhibit any negative response in growth or in gene expression, except for the PS treatment, which displayed a slight increase in bacterial growth and changes in gene expression potentially related to plastic degradation. <br/>In conclusion, this thesis demonstrates that low NP doses can inhibit microbial growth, but this effect depends on microbial communities and nanoparticle interactions with the environment. <br/>}},
author = {{Mafla-Endara, P. Micaela}},
isbn = {{978-91-8039-855-8}},
keywords = {{Microfluidic devices; Nanoplastics; Soil microorganisms; Toxicity}},
language = {{eng}},
month = {{10}},
publisher = {{Media-Tryck, Lund University, Sweden}},
school = {{Lund University}},
title = {{Encounters at the microscale: Unraveling soil microbial interactions with nanoplastics}},
year = {{2023}},
}