Nanoscale exploration of microbial surfaces using the atomic force microscope

Application of atomic force microscopy in the characterization of fruits and vegetables and associated substances toward improvement in quality, preservation, and processing: nanoscale structure and mechanics perspectives

Fruits and vegetables are essential horticultural crops for humans. The quality of fruits and vegetables is critical in determining their nutritional value and edibility, which are decisive to their commercial value. Besides, it is also important to understand the changes in key substances involved in the preservation and processing of fruits and vegetables. Atomic force microscopy (AFM), a powerful technique for investigating biological surfaces, has been widely used to characterize the quality of fruits and vegetables and the substances involved in their preservation and processing from the perspective of nanoscale structure and mechanics. This review summarizes the applications of AFM to investigate the texture, appearance, and nutrients of fruits and vegetables based on structural imaging and force measurements. Additionally, the review highlights the application of AFM in characterizing the morphological and mechanical properties of nanomaterials involved in preserving and processing fruits and vegetables, including films and coatings for preservation, bioactive compounds for processing purposes, nanofiltration membrane for concentration, and nanoencapsulation for delivery of bioactive compounds. Furthermore, the strengths and weaknesses of AFM for characterizing the quality of fruits and vegetables and the substances involved in their preservation and processing are examined, followed by a discussion on the prospects of AFM in this field.

Tissue characterization of the medical fungus Hericium coralloides by focus-variation microscopy

In this study, the potential of focus-variation microscopic imaging was evaluated in a study of morphological patterns of the potential medicinal fungus Hericium coralloides (Basidiomycota). We created three-dimensional reconstructions and visualizations using the imaging technique on a fresh H. coralloides basidioma. The aim was to approximate the spore dispersal efficiency of this basidiomata type regarding the investment of tissue biomass and its reproductive output (production of basidiospores). Results were correlated with published data gained from magnetic resonance imaging and micro-computed tomography. It is demonstrated that focus-variation microscopic imaging results in a more distinct picture of the morphology of the edible and potentially medicinal H. coralloides basidiomata. However, a direct measurement of spore production was not possible. Spore production could only be estimated in combination with a mathematical model because the surface was not directly measurable due to the cellular heterogeneity. However, focus-variation microscopic imaging allows a better and faster estimation of spore production compared with the published methods. Furthermore, it was found that a scanning resolution of 5× is sufficient for determining the fungal surface precisely because at a higher resolution artifacts occur, resulting in adulteration of the image.

In situ imaging of multiphase bio-interfaces at the micro-/nanoscale

The multiphase bio-interfacial system constituted by biological surfaces and their surrounding environment is usually considered to be an essential clue for exploring the mysterious relationship between surface architecture and function. As a visualizing method to understand these systems, in situ imaging of multiphase interfaces (e.g., air/liquid/solid and oil/water/solid systems) at the micro-/nanoscale, still remains a huge challenge, as a result of their heterogeneity and complexity. Here, recent progress on real-space micro-/nanoscale imaging of multiphase bio-interfacial systems is reviewed; this includes several techniques and imaging results on bio-interfaces, such as the lotus leaf, fish scale, living cell's surface, and fresh tissue surface. The results evidently show that interfacial structures have a significant impact on the state of the microscopic multiphase interface, further influencing specific functions. Based on this research, technical innovations, some more complicated multiphase interface systems, and structure-function coupling mechanism are proposed.

Nanoimaging for protein misfolding diseases

Misfolding and aggregation of proteins are widespread phenomena leading to the development of numerous neurodegenerative disorders such as Parkinson's, Alzheimer's, and Huntington's diseases. Each of these diseases is linked to structural misfolding and aggregation of a particular protein. The aggregated forms of the protein induce the development of a particular disease at all levels, leading to neuronal dysfunction and loss. Because protein refolding is frequently accompanied by transient association of partially folded intermediates, the propensity to aggregate is considered a general characteristic of the majority of proteins. X-ray crystallography, nuclear magnetic resonance, electron microscopy, and atomic force microscopy have provided important information on the structure of aggregates. However, fundamental questions, such as why the misfolded conformation of the protein is formed, and why this state is important for self-assembly, remain unanswered. Although it is well known that the same protein under pathological conditions can lead to the formation of aggregates with diverse biological consequences, the conditions leading to misfolding and the formation of the disease prone complexes are unclear, complicating any development of efficient prevention of the diseases. Misfolded states exist transiently, so answering these questions requires the use of novel approaches and methods. Progress has been made during the past few years, when recently developed ensemble methods and single-molecule biophysics techniques were applied to the problem of the protein misfolding. In this review, the impacts of these studies on the understanding of the mechanisms of the protein self-assembly into aggregates and on the development of treatments of the diseases are discussed.

Microbial structuring of marine ecosystems

Despite the impressive advances that have been made in assessing the diversity of marine microorganisms, the mechanisms that underlie the participation of microorganisms in marine food webs and biogeochemical cycles are poorly understood. Here, we stress the need to examine the biochemical interactions of microorganisms with ocean systems at the nanometre to millimetre scale--a scale that is relevant to microbial activities. The local impact of microorganisms on biogeochemical cycles must then be scaled up to make useful predictions of how marine ecosystems in the whole ocean might respond to global change. This approach to microbial oceanography is not only helpful, but is in fact indispensable.