Barlow Daniel E, Biffinger Justin C, Estrella Luis, Lu Qin, Hung Chia-Suei, Nadeau Lloyd J, Crouch Audra L, Russell John N, Crookes-Goodson Wendy J
Chemistry Division , US Naval Research Laboratory , Washington , District of Columbia 20375 , United States.
Chemistry Department , University of Dayton , 300 College Park , Dayton , Ohio 45469 , United States.
Langmuir. 2020 Feb 18;36(6):1596-1607. doi: 10.1021/acs.langmuir.9b03421. Epub 2020 Feb 6.
Painted environmental surfaces are prone to microbiological colonization with potential coating deterioration induced by the microorganisms. Accurate mechanistic models of these interactions require an understanding of the heterogeneity in which the deterioration processes proceed. Here, unsaturated biofilms (i.e., at air/solid interfaces) of the yeast were prepared on polyether polyurethane (PEUR) and polyester-polyether polyurethane (PEST-PEUR) coatings and incubated for up to 33 days at controlled temperature and humidity with no additional nutrients. Transmission micro-Fourier transform infrared microscopy (μFTIR) confirmed preferential hydrolysis of the ester component by the biofilm. Atomic force microscopy combined with infrared nanospectroscopy (AFM-IR) was used to analyze initial PEST-PEUR coating deterioration processes at the single-cell level, including underlying surfaces that became exposed following cell translocation. The results revealed distinct deterioration features that remained localized within ∼10 μm or less of the edges of individual cells and cell clusters. These features comprised depressions of up to ∼300 nm with locally reduced ester/urethane ratios. They are consistent with a formation process initiated by enzymatic ester hydrolysis followed by erosion from water condensation cycles. Further observations included particle accumulation in the broader biofilm vicinity. AFM-IR spectroscopy indicated these to be secondary microplastics consisting of urethane-rich oligomeric aggregates. Overall, multiple contributing factors have been identified that can facilitate differential deterioration rates across the PEST-PEUR surface. Effects of the imposed nutrient conditions on physiology were also apparent, with cells developing the characteristics of starvation response, despite the availability of polyester metabolites as a carbon source. The combined results provide new laboratory insights into field-relevant microbiological polymer deterioration mechanisms and biofilm physiology at polymer coating interfaces.
涂漆的环境表面容易受到微生物的定殖，微生物可能会导致涂层劣化。要准确建立这些相互作用的机理模型，需要了解劣化过程发生的异质性。在此，在聚醚聚氨酯（PEUR）和聚酯 - 聚醚聚氨酯（PEST - PEUR）涂层上制备了酵母的不饱和生物膜（即气/固界面处的生物膜），并在可控的温度和湿度下孵育长达33天，不添加额外营养物质。透射微傅里叶变换红外显微镜（μFTIR）证实生物膜对酯成分有优先水解作用。原子力显微镜结合红外纳米光谱（AFM - IR）用于在单细胞水平分析PEST - PEUR涂层的初始劣化过程，包括细胞移位后暴露的下层表面。结果揭示了不同的劣化特征，这些特征局限于单个细胞和细胞簇边缘约10μm或更小的范围内。这些特征包括深度达约300nm的凹陷，局部酯/聚氨酯比例降低。它们与由酶促酯水解引发，随后因水冷凝循环而侵蚀的形成过程一致。进一步的观察包括在更广泛的生物膜附近有颗粒积累。AFM - IR光谱表明这些是由富含聚氨酯的低聚物聚集体组成的次生微塑料。总体而言，已确定多种促成因素可导致PEST - PEUR表面劣化速率不同。施加的营养条件对酵母生理学的影响也很明显，尽管有聚酯代谢物作为碳源，但细胞仍表现出饥饿反应的特征。综合结果为聚合物涂层界面处与实际环境相关的微生物聚合物劣化机制和生物膜生理学提供了新的实验室见解。
