The Polygonal Cell Shape and Surface Protein Layer of Anaerobic Methane-Oxidizing Methylomirabilislanthanidiphila Bacteria

Methylomirabilis bacteria perform anaerobic methane oxidation coupled to nitrite reduction via an intra-aerobic pathway, producing carbon dioxide and dinitrogen gas. These diderm bacteria possess an unusual polygonal cell shape with sharp ridges that run along the cell body. Previously, a putative surface protein layer (S-layer) was observed as the outermost cell layer of these bacteria. We hypothesized that this S-layer is the determining factor for their polygonal cell shape. Therefore, we enriched the S-layer from M. lanthanidiphila cells and through LC-MS/MS identified a 31 kDa candidate S-layer protein, mela_00855, which had no homology to any other known protein. Antibodies were generated against a synthesized peptide derived from the mela_00855 protein sequence and used in immunogold localization to verify its identity and location. Both on thin sections of M. lanthanidiphila cells and in negative-stained enriched S-layer patches, the immunogold localization identified mela_00855 as the S-layer protein. Using electron cryo-tomography and sub-tomogram averaging of S-layer patches, we observed that the S-layer has a hexagonal symmetry. Cryo-tomography of whole cells showed that the S-layer and the outer membrane, but not the peptidoglycan layer and the cytoplasmic membrane, exhibited the polygonal shape. Moreover, the S-layer consisted of multiple rigid sheets that partially overlapped, most likely giving rise to the unique polygonal cell shape. These characteristics make the S-layer of M. lanthanidiphila a distinctive and intriguing case to study.

Ellipse packing in 2D cell tessellation: A theoretical explanation for Lewis’s law and Aboav-Weaire’s law

Background: To date, the theoretical bases of Lewis’s law and Aboav-Weaire’s law are still unclear. Methods: Software R with package Conicfit was used to fit ellipses based on geometric parameters of polygonal cells of red alga Pyropia haitanensis. Results: The average form deviation of vertexes from the fitted ellipse was 0 \(\pm\) 3.1 % (8,291 vertices in 1375 cells were examined). The area of polygonal cell was 0.9 \(\pm\)0.1 times of the area of the ellipse’s maximal inscribed polygon (EMIP). These results indicated that the polygonal cells could be considered as ellipse’s inscribed polygons (EIPs) and tended to form EMIPs. This phenomenon was named as ellipse packing. Based on the numbers of cell edges, cell area and geometries of fitted ellipses, we derived and verified the new relations of Lewis’s law and Aboav-Weaire’s law. Lewis’s law for a n-edged cell: \[cell\ area=0.5nab\sin\left(\frac{2\pi}{n}\right)\left(1-\frac{3}{n^2}\right)\] Aboav-Weaire’s law: \[average\ side\ number\ of\ neighboring\ cells=6+\frac{6-n}{n}\times \left(\frac{a}{b}+\frac{3}{n^2}\right)\] where \(a\) and \(b\) are the semi-major axis and the semi-minor axis of fitted ellipse, respectively. Conclusions: Ellipse packing is a short-range order which places restrictions on the direction of cell division and the turning angles of cell edges. The ellipse packing requires allometric growth of cell edges. Lewis’s law describes the effect of deformation from EMIP to EIP on area. Aboav-Weaire’s law mainly reflects the effect of deformation from circle to ellipse on number of neighboring cells, and the deformation from EMIP to EIP has only a minor effect. The results of this study could help to simulate the dynamics of cell topology during growth.

Ellipse packing in 2D cell tessellation: A theoretical explanation for Lewis’s law and Aboav-Weaire’s law

Background: To date, the theoretical bases of Lewis’s law and Aboav-Weaire’s law are still unclear. Methods: Software R with package Conicfit was used to fit ellipses based on geometric parameters of polygonal cells of red alga Pyropia haitanensis. Results: The average form deviation of vertexes from the fitted ellipse was 0±3.1 % (8,291 vertices in 1375 cells were examined). Area of the polygonal cell was 0.9±0.1 times of area of the ellipse’s maximal inscribed polygon (EMIP). These results indicated that the polygonal cells can be considered as ellipse’s inscribed polygons (EIPs) and tended to form EMIPs. This phenomenon was named as ellipse packing. Then, an improved relation of Lewis’s law for a n-edged cell was derived \[cell\ area=0.5nab\sin(\frac{2\pi}{n})(1-\frac{3}{n^2})\] where, a and b are the semi-major axis and the semi-minor axis of fitted ellipse, respectively. This study also improved the relation of Aboav-Weaire’s law \[number\ of\ neighboring\ cells=6+\frac{6-n}{n}(\frac{a}{b}+\frac{3}{n^2})\] Conclusions: Ellipse packing is a short-range order which places restrictions on the direction of cell division and the turning angles of cell edges. The ellipse packing requires allometric growth of cell edges. Lewis’s law describes the effect of deformation from EMIP to EIP on area. Aboav-Weaire’s law mainly reflects the effect of deformation from circle to ellipse on number of neighboring cells, and the deformation from EMIP to EIP has only a minor effect. The results of this study could help to simulate the dynamics of cell topology during growth.

FREE AND FORCED VIBRATION ANALYSIS USING THE n-SIDED POLYGONAL CELL-BASED SMOOTHED FINITE ELEMENT METHOD (nCS-FEM)

A n-sided polygonal cell-based smoothed finite element method (nCS-FEM) was recently proposed to analyze the elastic solid mechanics problems, in which the problem domain can be discretized by a set of polygons with an arbitrary number of sides. In this paper, the nCS-FEM is further extended to the free and forced vibration analyses of two-dimensional (2D) dynamic problems. A simple lump mass matrix is proposed and hence the complicated integrations related to computing the consistent mass matrix can be avoided in the nCS-FEM. Several numerical examples are investigated and the results found of the nCS-FEM agree well with exact solutions and with those of others FEM.

A Statically Balanced Shape Shifting Surface

This paper presents a concept for producing a Statically Balanced Shape-Shifting Surface (SB-SSS). In this context, an SB-SSS is a surface that can require near-zero magnitude force changes to accomplish a change in shape while retaining effectiveness as a physical barrier. This paper focuses on how to statically balance a specifically-designed compliant mechanism and how to incorporate this mechanism into a polygonal cell. The mechanism consists of a compliant Peaucellier-Lipkin linkage layered with a pre-stressed link as the balancer. Prior art is presented that can show how a polygonal cell can be incorporated into a surface via a tiling array. Specifically shaped overlapping thin plates are used to retain the physical barrier requirement. The demonstration of a virtually zero-force Shape-Shifting Surface (SSS) suggests that SSS’s can be designed with a wide range of force-displacement properties, i.e. ranging from that of a square of the parent material to the zero-force mechanism presented here. Applications for an SB-SSS may be macro-scale or micro-scale and may include sensors, biomedical applications, defense applications, and variable stiffness materials.

Arreglo de los polígonos del exocorion de huevos eclosionados de algunas especies de los géneros Triatoma Laporte, Meccus Stal y Nesotriatoma Usinger (Heteroptera: Reduviidae).

Resumen. En este trabajo se estudiaron estructural y cuantitativamente las celdas exocoriales de huevos eclosionados de Triatoma infestans (Klug), Triatoma lenti Sherlock & Serafim, Triatoma maculata (Erichson), Triatoma sordida (Stal), Meccus picturatus (Usinger), Meccus longipennis (Usinger), Meccus pallidipennis (Stal) and Nesotriatoma flavida (Neiva). Los huevos se analizaron por regiones: caudal, media y cefálica. Se encontró que el hexágono fue el polígono más abundante en todas las regiones del huevo y en todas las especies, seguido del pentágono y del heptágono; se encontraron diferencias estadísticamente significativas en el número tanto de hexágonos y pentágonos entre regiones de una misma especie y entre la misma región de las diferentes especies, sin embargo, el número promedio de heptágonos no varió al comparar la región media entre las diferentes especies y al comparar las diferentes regiones en una misma especie. No se encontraron diferencias estadísticamente significativas en el promedio de polígonos, segmentos totales, heptágonos, hexágonos y pentágonos, al comparar las especies examinadas del género Meccus. Se propone un protocolo de identificación y análisis de teselaciones, con el cual se encontró que en 108 campos examinados de 385.000 µm2 cada uno, se identificaron teselaciones compartidas en los 108 campos observados con determinadas combinaciones de heptágonos, hexágonos y pentágonos, y se observaron teselaciones no compartidas en la totalidad de los campos, con combinaciones de polígonos de cuatro a nueve lados, y cada teselación se representó por un grafo. Se discuten las implicaciones taxonómicas, funcionales, filogenéticas y construccionales de los arreglos poligonales descritos. Arragement of exochorial polygons of hatched eggs in several species of the genera Triatoma Laporte, Meccus Stal y Nesotriatoma Usinger (Heteroptera: Reduviidae). Abstract. In this study a structural and quantitative analysis of the exochorial polygonal cells of hatched eggs of Triatoma infestans (Klug), Triatoma lenti Sherlock & Serafim, Triatoma maculata (Erichson), Triatoma sordida (Stal), Meccus picturatus (Usinger), Meccus longipennis (Usinger), Meccus pallidipennis (Stal) and Nesotriatoma flavida (Neiva) was performed; cephalic, median and caudal egg regions were compared. It was found that cells with hexagonal shape were more abundant among all egg regions and studied species, followed by pentagonal and heptagonal polygons respectively. The average number of hexagonal and pentagonal polygons was significantly different among the three egg regions for each species, and when comparing the median, cephalic and caudal egg regions among different species. However, the average number of heptagons did not differ among the three egg regions for each species. The average number of heptagons did not differ when comparing the median egg region, but differed when comparing the cephalic and caudal egg regions, among different species. The average number of hexagons, pentagons, heptagons, total polygons, and total segments did not differ among the different species eggs of Meccus genus. A group of 108 micrographies (380,000 μm2 each one) were studied using tessellation methods. Shared tilings and unshared tilings were found in all the micrographies observed. Shared tilings were conformed by combinations of heptagons, hexagons and pentagons, and unshared tilings by combinations of polygons from four to nine sides. Finally, each tiling arrangement was represented as a graph. Taxonomic, functional and phylogenetic implications of the polygonal cell arrangement described here are discussed.

Inducible Expression of Chimeric EWS/ETS Proteins Confers Ewing's Family Tumor-Like Phenotypes to Human Mesenchymal Progenitor Cells

ABSTRACT Ewing's family tumor (EFT) is a rare pediatric tumor of unclear origin that occurs in bone and soft tissue. Specific chromosomal translocations found in EFT cause EWS to fuse to a subset of ets transcription factor genes (ETS), generating chimeric EWS/ETS proteins. These proteins are believed to play a crucial role in the onset and progression of EFT. However, the mechanisms responsible for the EWS/ETS-mediated onset remain unclear. Here we report the establishment of a tetracycline-controlled EWS/ETS-inducible system in human bone marrow-derived mesenchymal progenitor cells (MPCs). Ectopic expression of both EWS/FLI1 and EWS/ERG proteins resulted in a dramatic change of morphology, i.e., from a mesenchymal spindle shape to a small round-to-polygonal cell, one of the characteristics of EFT. EWS/ETS also induced immunophenotypic changes in MPCs, including the disappearance of the mesenchyme-positive markers CD10 and CD13 and the up-regulation of the EFT-positive markers CD54, CD99, CD117, and CD271. Furthermore, a prominent shift from the gene expression profile of MPCs to that of EFT was observed in the presence of EWS/ETS. Together with the observation that EWS/ETS enhances the ability of cells to invade Matrigel, these results suggest that EWS/ETS proteins contribute to alterations of cellular features and confer an EFT-like phenotype to human MPCs.