Gamaleya Research Centre of Epidemiology and Microbiology, Moscow, Russia.
Lomonosov Moscow State University, Moscow, Russia.
Appl Environ Microbiol. 2020 Sep 1;86(18). doi: 10.1128/AEM.01074-20.
Chronic infections are associated with the formation of nonattached biofilm-like aggregates. models of surface-attached biofilms do not always accurately mimic these processes. Here, we tested a new approach to create nonattached bacterial aggregates using the principle of magnetic levitation of biological objects placed into a magnetic field gradient. Bacteria grown under magnetic levitation conditions formed nonattached aggregates that were studied with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) and characterized quantitatively. Nonattached aggregates consisted of bacteria submerged into an extracellular matrix and demonstrated features characteristic of biofilms, such as a polymeric matrix that binds Ruby Red and Congo red dyes, a prerequisite of bacterial growth, and increased resistance to gentamicin. Three quantitative parameters were explored to characterize strain-specific potential to form nonattached aggregates: geometric sizes, relative quantities of aggregated and free-swimming bacteria, and Congo red binding. Among three tested strains, one strain formed nonattached aggregates poorly, and for this strain, all three of the considered parameters were different from those of the other two strains ( < 0.05). Further, we characterized biofilm formation on plastic and agar surfaces by these strains and found that good biofilm formation ability does not necessarily indicate good nonattached aggregate formation ability, and vice versa. The model and quantitative methods can be applied for studies of nonattached aggregates and modeling bacterial behavior in chronic infections, as it is important to increase our understanding of the role that nonattached bacterial aggregates play in the pathogenesis of chronic diseases. An increasing amount of evidence indicates that chronic infections are associated with nonattached biofilm-like aggregates formed by pathogenic bacteria. These aggregates differ from biofilms because they form under low-shear conditions within the volume of biological fluids and they do not attach to surfaces. Here, we describe an model that provides nonattached aggregate formation within the liquid volume due to magnetic levitation. Using this model, we demonstrated that despite morphological and functional similarities of nonattached aggregates and biofilms, strains that exhibit good biofilm formation might exhibit poor nonattached aggregate formation, suggesting that mechanisms underlying the formation of biofilms and nonattached aggregates are not identical. The magnetic levitation approach can be useful for studies of nonattached aggregate formation and simulation of bacterial behavior in chronic infections.
慢性感染与无附着生物膜样聚集物的形成有关。附着生物膜模型并不总是能准确模拟这些过程。在这里，我们测试了一种新的方法，即利用置于磁场梯度中的生物物体的磁悬浮原理来形成无附着细菌聚集体。在磁悬浮条件下生长的细菌形成了无附着的聚集物，并用共聚焦激光扫描显微镜 (CLSM) 和扫描电子显微镜 (SEM) 进行了研究，并进行了定量分析。无附着的聚集物由浸入细胞外基质中的细菌组成，并表现出生物膜的特征，例如结合 Ruby Red 和刚果红染料的聚合物基质，这是细菌生长的前提条件，并且对庆大霉素的抵抗力增加。探索了三个定量参数来表征菌株形成无附着聚集物的特定潜力：几何尺寸、聚集和自由游动细菌的相对数量以及刚果红结合。在三种测试的菌株中，一种菌株形成无附着聚集物的能力较差，对于这种菌株，这三个考虑的参数与其他两种菌株的参数都不同（<0.05）。此外，我们还通过这些菌株对塑料和琼脂表面上的生物膜形成进行了表征，发现良好的生物膜形成能力不一定表明良好的无附着聚集物形成能力，反之亦然。该模型和定量方法可用于无附着聚集物的研究和慢性感染中细菌行为的模拟，因为增加对无附着细菌聚集物在慢性疾病发病机制中作用的理解非常重要。越来越多的证据表明，慢性感染与由致病菌形成的无附着生物膜样聚集物有关。这些聚集物与生物膜不同，因为它们在生物液体体积内的低剪切条件下形成，并且不附着在表面上。在这里，我们描述了一种由于磁悬浮而在液体体积内形成无附着聚集物的模型。使用该模型，我们证明了尽管无附着聚集物和生物膜在形态和功能上相似，但表现出良好生物膜形成能力的菌株可能表现出较差的无附着聚集物形成能力，这表明形成生物膜和无附着聚集物的机制并不相同。磁悬浮方法可用于无附着聚集物形成的研究和慢性感染中细菌行为的模拟。
