已知二价阳离子影响生物膜的结构和机械性质。为了揭示培养基中Fe2+离子对生物膜发育的影响,结构和稳定性，枯草芽孢杆菌生物膜在微型流体流动池中培养。两种不同的Fe2流入浓度（0.25和2.5mg/L，分别)和墙体剪应力水平(0.05和0.27Pa，分别)进行了测试。通过光学相干断层扫描每天原位和非侵入性地确定介观生物膜结构。一组十个结构参数用于量化生物膜结构，它的发展和变化。该研究集中于表征中尺度（毫米范围）的生物膜结构和发育。因此,培养和分析生物膜重复(n=10)。定义了三个假设，以估计Fe2流入浓度和/或壁剪切应力对生物膜发育和结构的影响，分别。这并不打算调查和描述铁掺入的潜在机制，因为这将需要一套不同的工具在微观水平上应用，以及使用，即，总体方法。Fe2+添加影响了生物膜的发育(例如，生物膜积累）和结构明显。实验表明，FeO（OH）在生物膜基质内积累，并且Fe2流入浓度与生物膜积累呈正相关。更详细地说,与培养过程中施加的壁剪切应力无关，与0.25mgFe2/L（4.48µmol/L）的低Fe2流入浓度相比，生物膜在2.5mgFe2/L（44.8µmol/L；高流入浓度）时增长了大约四倍。这一发现得到了统计验证(Scheirer-Ray-Hare检验，方差分析)和暗示枯草芽孢杆菌生物膜的更高稳定性(例如，在升高的Fe2流入浓度下生长时，内聚和粘合强度提高）。
Bivalent cations are known to affect the structural and mechanical properties of biofilms. In order to reveal the impact of Fe2+ ions within the cultivation medium on biofilm development, structure and stability, Bacillus subtilis biofilms were cultivated in mini-fluidic flow cells. Two different Fe2+ 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 (n = 10) were cultivated and analyzed. Three hypotheses were defined in order to estimate the effect of Fe2+ 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. Fe2+ 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 Fe2+ 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 Fe2+/L (44.8 µmol/L; high inflow concentration) compared to the low Fe2+ inflow concentration of 0.25 mg Fe2+/L (4.48 µmol/L). This finding was statistically verified (Scheirer-Ray-Hare test, ANOVA) and hints at a higher stability of Bacillus subtilis biofilms (e.g., elevated cohesive and adhesive strength) when grown at elevated Fe2+ inflow concentrations.
