Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study
Bivalent cations are known to affect the structural and mechanical properties of biofilms. In order to reveal the impact of Fe<sup>2+</sup> ions within the cultivation medium on biofilm development, structure and stability, <i>Bacillus subtilis</i> biofilms were cultivated in...
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MDPI AG
2022-11-01
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| Series: | Microorganisms |
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| Online Access: | https://www.mdpi.com/2076-2607/10/11/2234 |
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| author | Luisa Gierl Harald Horn Michael Wagner |
| author_facet | Luisa Gierl Harald Horn Michael Wagner |
| author_sort | Luisa Gierl |
| collection | DOAJ |
| description | Bivalent cations are known to affect the structural and mechanical properties of biofilms. In order to reveal the impact of Fe<sup>2+</sup> ions within the cultivation medium on biofilm development, structure and stability, <i>Bacillus subtilis</i> biofilms were cultivated in mini-fluidic flow cells. Two different Fe<sup>2+</sup> inflow concentrations (0.25 and 2.5 mg/L, respectively) and wall shear stress levels (0.05 and 0.27 Pa, respectively) were tested. Mesoscopic biofilm structure was determined daily in situ and non-invasively by means of optical coherence tomography. A set of ten structural parameters was used to quantify biofilm structure, its development and change. The study focused on characterizing biofilm structure and development at the mesoscale (mm-range). Therefore, biofilm replicates (<i>n</i> = 10) were cultivated and analyzed. Three hypotheses were defined in order to estimate the effect of Fe<sup>2+</sup> inflow concentration and/or wall shear stress on biofilm development and structure, respectively. It was not the intention to investigate and describe the underlying mechanisms of iron incorporation as this would require a different set of tools applied at microscopic levels as well as the use of, i.e., omic approaches. Fe<sup>2+</sup> addition influenced biofilm development (e.g., biofilm accumulation) and structure markedly. Experiments revealed the accumulation of FeO(OH) within the biofilm matrix and a positive correlation of Fe<sup>2+</sup> inflow concentration and biofilm accumulation. In more detail, independent of the wall shear stress applied during cultivation, biofilms grew approximately four times thicker at 2.5 mg Fe<sup>2+</sup>/L (44.8 µmol/L; high inflow concentration) compared to the low Fe<sup>2+</sup> inflow concentration of 0.25 mg Fe<sup>2+</sup>/L (4.48 µmol/L). This finding was statistically verified (Scheirer–Ray–Hare test, ANOVA) and hints at a higher stability of <i>Bacillus subtilis</i> biofilms (e.g., elevated cohesive and adhesive strength) when grown at elevated Fe<sup>2+</sup> inflow concentrations. |
| first_indexed | 2024-03-09T18:08:09Z |
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| institution | Directory Open Access Journal |
| issn | 2076-2607 |
| language | English |
| last_indexed | 2024-03-09T18:08:09Z |
| publishDate | 2022-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Microorganisms |
| spelling | doaj.art-9cf1fdf3d5ba4887a87236f78b783b492023-11-24T09:16:57ZengMDPI AGMicroorganisms2076-26072022-11-011011223410.3390/microorganisms10112234Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case StudyLuisa Gierl0Harald Horn1Michael Wagner2Water Chemistry and Water Technology, Engler-Bunte-Institut, Karlsruhe Institute of Technology, Engler-Bunte-Ring 9a, 76131 Karlsruhe, GermanyWater Chemistry and Water Technology, Engler-Bunte-Institut, Karlsruhe Institute of Technology, Engler-Bunte-Ring 9a, 76131 Karlsruhe, GermanyWater Chemistry and Water Technology, Engler-Bunte-Institut, Karlsruhe Institute of Technology, Engler-Bunte-Ring 9a, 76131 Karlsruhe, GermanyBivalent cations are known to affect the structural and mechanical properties of biofilms. In order to reveal the impact of Fe<sup>2+</sup> ions within the cultivation medium on biofilm development, structure and stability, <i>Bacillus subtilis</i> biofilms were cultivated in mini-fluidic flow cells. Two different Fe<sup>2+</sup> inflow concentrations (0.25 and 2.5 mg/L, respectively) and wall shear stress levels (0.05 and 0.27 Pa, respectively) were tested. Mesoscopic biofilm structure was determined daily in situ and non-invasively by means of optical coherence tomography. A set of ten structural parameters was used to quantify biofilm structure, its development and change. The study focused on characterizing biofilm structure and development at the mesoscale (mm-range). Therefore, biofilm replicates (<i>n</i> = 10) were cultivated and analyzed. Three hypotheses were defined in order to estimate the effect of Fe<sup>2+</sup> inflow concentration and/or wall shear stress on biofilm development and structure, respectively. It was not the intention to investigate and describe the underlying mechanisms of iron incorporation as this would require a different set of tools applied at microscopic levels as well as the use of, i.e., omic approaches. Fe<sup>2+</sup> addition influenced biofilm development (e.g., biofilm accumulation) and structure markedly. Experiments revealed the accumulation of FeO(OH) within the biofilm matrix and a positive correlation of Fe<sup>2+</sup> inflow concentration and biofilm accumulation. In more detail, independent of the wall shear stress applied during cultivation, biofilms grew approximately four times thicker at 2.5 mg Fe<sup>2+</sup>/L (44.8 µmol/L; high inflow concentration) compared to the low Fe<sup>2+</sup> inflow concentration of 0.25 mg Fe<sup>2+</sup>/L (4.48 µmol/L). This finding was statistically verified (Scheirer–Ray–Hare test, ANOVA) and hints at a higher stability of <i>Bacillus subtilis</i> biofilms (e.g., elevated cohesive and adhesive strength) when grown at elevated Fe<sup>2+</sup> inflow concentrations.https://www.mdpi.com/2076-2607/10/11/2234<i>Bacillus subtilis</i> biofilmsbiofilm structurebiofilm developmentbiofilm stabilityoptical coherence tomographyiron |
| spellingShingle | Luisa Gierl Harald Horn Michael Wagner Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study Microorganisms <i>Bacillus subtilis</i> biofilms biofilm structure biofilm development biofilm stability optical coherence tomography iron |
| title | Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study |
| title_full | Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study |
| title_fullStr | Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study |
| title_full_unstemmed | Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study |
| title_short | Impact of Fe<sup>2+</sup> and Shear Stress on the Development and Mesoscopic Structure of Biofilms—A <i>Bacillus subtilis</i> Case Study |
| title_sort | impact of fe sup 2 sup and shear stress on the development and mesoscopic structure of biofilms a i bacillus subtilis i case study |
| topic | <i>Bacillus subtilis</i> biofilms biofilm structure biofilm development biofilm stability optical coherence tomography iron |
| url | https://www.mdpi.com/2076-2607/10/11/2234 |
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