Edge Of Colony Research Articles

Dynamic motility selection drives population segregation in a bacterial swarm

Population expansion in space, or range expansion, is widespread in nature and in clinical settings. Space competition among heterogeneous subpopulations during range expansion is essential to population ecology, and it may involve the interplay of multiple factors, primarily growth and motility of individuals. Structured microbial communities provide model systems to study space competition during range expansion. Here we use bacterial swarms to investigate how single-cell motility contributes to space competition among heterogeneous bacterial populations during range expansion. Our results revealed that motility heterogeneity can promote the spatial segregation of subpopulations via a dynamic motility selection process. The dynamic motility selection is enabled by speed-dependent persistence time bias of single-cell motion, which presumably arises from physical interaction between cells in a densely packed swarm. We further showed that the dynamic motility selection may contribute to collective drug tolerance of swarming colonies by segregating subpopulations with transient drug tolerance to the colony edge. Our results illustrate that motility heterogeneity, or "motility fitness," can play a greater role than growth rate fitness in determining the short-term spatial structure of expanding populations.

Use of Purple Non-Sulfur Photosynthetic Bacteria (Rhodobacter sphaeroides) in Promoting Ciliated Protozoa Growth.

Photosynthetic bacterium (PSB) was isolated from sediment samples of Yamagawa Bay, Kagoshima, Japan. Phylogenetic analysis results of PSB isolate were closely related to Rhodobacter sphaeroides, purple non-sulfur photosynthetic bacteria (PNSB). Pink-colored smooth edges of single bacterial colonies were observed after 3-5 days of incubation period on Basic I medium agar plates. Rhodobacter sphaeroides microscopic examination showed a short rod cell (1-2 µm length) with round ends. Sediment and water samples used for ciliates cultivation were collected from Kuwano-ura Bay, Koshiki Island, Japan. Ciliates were cultivated using fish meal with radish leaves medium (MI), with sediment into MI (MII) and algae media (MIII). The use of the algae media (MIII) in cultivation mixture produced the highest total number of ciliates. Big size ciliates were identified as Euplotes minuta and Cyclidium varibonneti, while small size was identified as Micrometopion nutans, based on PCR-DGGE. When ciliates were cultured with the PSB isolate, Rhodobacter sphaeroides as a feed, ciliates grow to 2,081 individual ml-1 72 hrs later. These findings indicate that PNSB can be used to promote ciliates growth.

First Report of a Leaf Spot Caused by Botrytis cinerea on Peanut (Arachis hypogaea) in China

Botrytis cinerea (teleomorph: Botryotinia fuckeliana) is an airborne, necrotrophic ascomycete plant pathogen, which has been reported to infect over 200 crop hosts worldwide (Boddy 2016; Kim et al. 2016). B. cinerea can cause severe damage to plants, such as gray mold on leaves or rot on fruit, both pre- and postharvest (Dean et al. 2012). In September 2015, brown, irregular-shaped lesions were observed on peanut leaves from Jilin province in China. Disease incidence in approximately a 10-ha area in each of 15 examined fields was 20 to 30%. Symptoms were initially observed on the apex and/or margin of the older leaves, were not restricted by the leaf veins, and enlarged to result in leaf necrosis and defoliation. Symptomatic leaf samples were collected, surface sterilized (75% ethanol, 30 s; 3% NaClO, 2 min), rinsed in sterile water three times, and air dried; small sections were plated on potato dextrose agar (PDA) medium and incubated at 25 ± 1°C (12-h photoperiod). Colonies on PDA medium were initially gray and covered the entire plate with aerial mycelium in 2 days. Black sclerotia were first observed at the edge of colonies after 3 days and then formed unevenly among the colonies after 6 days. Conidia were transparent, elliptical or ovoid, and measured 4.4 to 8.6 µm long × 3.4 to 5.8 µm wide (n = 50). For pathogenicity tests, a conidial suspension (10⁵ conidia/ml) was sprayed onto leaves of peanut plants grown in five 16 × 12-cm pots with six plants per pot. A similar number of plants were inoculated with sterile water to serve as controls. Inoculated plants were incubated in a growth cabinet with a high relative humidity (80%) for 72 h at 25°C, followed by 60 to 70% relative humidity at 25°C with a 12-h photoperiod of dark and light. Symptoms on leaves emerged between 7 and 10 days and were similar to those described on the field-collected leaves, whereas no symptoms were observed on the control plants. The pathogen that was reisolated from the inoculated leaves using the same method described above had the same morphology on PDA medium as described above. As for molecular identification, the internal transcribed spacer (ITS) and three nuclear protein-coding genes (glyceraldehydes-3-phosphate dehydrogenase gene [G3PDH], heat-shock protein 60 gene [HSP60], and DNA-dependent RNA polymerase subunit gene [RPB2]) were amplified using primer pairs ITS1/ITS4 (White et al. 1990), G3PDH-F/G3PDH-R, HSP60-F/HSP60-R, and RPB2-F/RPB2-R (Staats et al. 2005), respectively. The sequences were submitted to GenBank (ITS, MN272329; G3PDH, MK791186; HSP60, MK791187; RPB2, MK791188). BLASTn analysis showed 500/501, 994/994, 1,120/1,120, and 1,240/1,240 base pairs matched with sequences of B. cinerea deposited for ITS (MH763647), G3PDH, (MH479930), HSP60 (MH796663), and RPB2 (MH713610), respectively. To our knowledge, this is the first report of B. cinerea found on peanut plant in China. B. cinerea usually causes soft rotting of aerial plant parts and postharvest rotting of vegetables, fruits, and flowers (Williamson et al. 2007). The threat of this pathogen to peanut pods needs to be further investigated, because it could potentially lower the peanut quality and may be a threat to human health.

Vibrio parahaemolyticus cqsA controls production of quorum sensing signal molecule 3-hydroxyundecan-4-one and regulates colony morphology.

In order to adapt to different environments, Vibrio parahaemolyticus employed a complicated quorum sensing system to orchestrate gene expression and diverse colony morphology patterns. In this study, the function of the putative quorum sensing signal synthase gene cqsA (VPA0711 in V. Parahaemolyticus strain RIMD2210633 genome) was investigated. The cloning and expression of V. parahaemolyticus cqsA in Escherichia coli system induced the production of a new quorum sensing signal that was found in its culture supernatant. The signal was purified by high performance liquid chromatography methods and determined to be 3-hydroxyundecan- 4-one by indirect and direct mass spectra assays. The deletion of cqsA in RIMD2210633 changed V. parahaemolyticus colony morphology from the classical 'fried-egg' shape (thick and opaque in the center, while thin and translucent in the edge) of the wild-type colony to a 'pancake' shape (no significant difference between the centre and the edge) of the cqsA deleted colony. This morphological change could be restored by complementary experiment with cqsA gene or the signal extract. In addition, the expression of opaR, a well-known quorum sensing regulatory gene, could be up-regulated by cqsA deletion. Our results suggested that V. parahaemolyticus used cqsA to produce 3-hydroxyundecan-4-one signal and thereby regulated colony morphology and other quorum sensing-associated behaviors.

First Report of Curvularia oryzae Causing Leaf Spot of Coconut Seedling in China

Coconut (Cocos nucifera L.) is one of the most important perennial tropical crops of southern China. In June 2018, a new leaf spot disease was detected in nearly 100% of 1-year-old golden coconut seedlings at the nursery base in Qionghai, Hainan. At the beginning of the disease, the leaves exhibited water-stained chlorotic spots; as the symptom progressed, the edges of the lesions appeared orange-yellow to pale yellow-brown. Lesions were long oval, almost round, and sometimes irregular with dark brown center and distinct yellow halos. As the lesions continued to expand, several lesions coalesced forming a taupe irregular large spot. The center of the lesion was grayish white, and distinct dark brown necrotic lines were observed at the edges. Under high humidity conditions, thin gray-white mycelia were observed. Overall, 10 leaves with typical symptoms were randomly collected. Small tissue sections (5 × 5 mm) were cut from the lesion margin and surface sterilized in 75% ethanol for 30 s, following which the tissue surface was disinfected with 0.1% HgCl₂ for 2 min, washed thrice with sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 28°C. Five days after incubation, fast-growing fungal colonies with gray-white mycelia were observed, which then changed to dark green with a neat colony edge on PDA medium. Conidiophores were terete, straight or slightly curved, unbranched, often nodular, dilated, and light-to-moderately brown with smooth outer walls. Conidia were 27.1 to 43.3 × 19.0 to 23.4 µm (average 38.1 × 20.1 µm, n = 100), terminal, ovoid, obclavate, and three-distoseptate. The second cell at the base was the largest, taupe to dark brown in color, and often swollen; cells at both ends were slightly smaller and light in color. Based on morphological characteristics, the fungal isolates were preliminarily identified as Curvularia oryzae (Sivanesan 1987). Single-spore isolates were cultured on the PDA medium, and three representative strains were selected for DNA extraction. The identity of the isolates was confirmed via sequence analysis of the internal transcribed spacer (ITS) gene amplified using primers ITS1/ITS4 (White et al. 1990), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene amplified using gpd1/gpd2 (Berbee et al. 1999), and translation elongation factor 1-alpha (EF1a) gene amplified using 983F/2218R (Schoch et al. 2009); sequence data were deposited in GenBank (MN180224, MN180225, and MN481482). BLAST analysis demonstrated that these sequences were 99 to 100% similar to the ITS (MG238513), GAPDH (HG779156), and EF1a (KM196590) sequences of C. oryzae. Moreover, phylogenetic tree analysis using ClustalX and MEGA 7.0 software with the maximum likelihood method placed the isolates in the clade of C. oryzae (CBS169.53) with 98% bootstrap support. Based on the morphology, sequence data, and phylogenetic analysis, these isolates were determined as C. oryzae. To validate the results a pathogenicity test was performed. Twenty leaves were divided into two groups; the first group was sprayed with spore suspension (1 × 10⁶/ml) of the isolate, whereas the other group was sprayed with sterile water as a control. All plants were incubated at 28 ± 2°C and 100% relative humidity. Ten days after inoculation, leaves sprayed with the spore suspension exhibited the typical symptoms with 100% of leaf spot similar to the original samples, whereas leaves sprayed with sterile water showed no symptoms. Further, C. oryzae was reisolated from the leaf spot. Pathogenicity tests were repeated thrice with the same results. Koch’s postulates were achieved by the reisolation of C. oryzae from the inoculated leaves. C. oryzae has previously been reported to cause leaf spot of oil palm seedlings in Thailand (Sunpapao et al. 2014). To the best of our knowledge, this is the first report of leaf spot of coconut seedlings caused by C. oryzae.

When the "selfish herd" becomes the "frozen herd": spatial dynamics and population persistence in a colonial seabird.

Aggregations are common in ecological systems at a range of scales and may be driven by exogenous constraints such as environmental heterogeneity and resource availability or by "self-organizing" interactions among individuals. One mechanism leading to self-organized animal aggregations is captured by Hamilton's "selfish herd" hypothesis, which suggests that aggregations may be driven by an individual's effort to minimize their risk of predation by surrounding themselves with conspecifics. We demonstrate that aggregations observed in Adélie Penguin (Pygoscelis adeliae) colonies are a convolution of both self-organized dynamics and external forcing arising from landscape terrain. In fluid, highly mobile aggregations, individuals are constantly moving in response to changing environmental conditions, the locations of predators, or the movements of conspecifics. However, when the ability to rearrange is limited and spatial reconfiguration occurs on slower time scales than changes in population size, systems may become trapped in suboptimal arrangements. We use simulated annealing to demonstrate that Adélie Penguin colonies are frozen in suboptimal spatial arrangements, and employ an individual-based modeling approach to demonstrate that this suboptimal spatial configuration is driven by a convolution of nest site fidelity and stochastic events at the level of individual nests. The resulting spatial dynamics are responsible for a hysteretic response to long-term changes in abundance. We find that declining abundance leads to fragmentation even in a homogeneous environment, which has population-level consequences for reproductive success because predation is biased towards colony edges. Strong edge effects from heterogeneous predation coupled with fragmentation in response to population declines create a positive feedback cycle that can accelerate population decline. This work provides a mechanistic understanding of complex spatial structuring in penguin colonies, provides a link between current spatial patterning and past dynamics, and suggests the possibility of critical collapse in seabird populations.

Peer pressure from a Proteus mirabilis self-recognition system controls participation in cooperative swarm motility.

Colonies of the opportunistic pathogen Proteus mirabilis can distinguish self from non-self: in swarming colonies of two different strains, one strain excludes the other from the expanding colony edge. Predominant models characterize bacterial kin discrimination as immediate antagonism towards non-kin cells, typically through delivery of toxin effector molecules from one cell into its neighbor. Upon effector delivery, receiving cells must either neutralize it by presenting a cognate anti-toxin as would a clonal sibling, or suffer cell death or irreversible growth inhibition as would a non-kin cell. Here we expand this paradigm to explain the non-lethal Ids self-recognition system, which stops access to a social behavior in P. mirabilis by selectively and transiently inducing non-self cells into a growth-arrested lifestyle incompatible with cooperative swarming. This state is characterized by reduced expression of genes associated with protein synthesis, virulence, and motility, and also causes non-self cells to tolerate previously lethal concentrations of antibiotics. We show that temporary activation of the stringent response is necessary for entry into this state, ultimately resulting in the iterative exclusion of non-self cells as a swarm colony migrates outwards. These data clarify the intricate connection between non-lethal recognition and the lifecycle of P. mirabilis swarm colonies.

Microbial Range Expansions on Liquid Substrates

Despite the importance that fluid flow plays in transporting and organizing populations, few laboratory systems exist to systematically investigate the impact of advection on their spatial evolutionary dynamics. To address this problem, we study the morphology and genetic spatial structure of microbial colonies growing on the surface of a nutrient-laden fluid $10^4$ to $10^5$ times more viscous than water in Petri dishes, the extreme but finite viscosity inhibits undesired thermal convection and allows populations to effectively live at the air-liquid interface due to capillary forces. We discover that S. cerevisiae (baker's yeast) growing on a viscous liquid behave like "active matter": they metabolically generate fluid flows many times larger than their unperturbed colony expansion speed, and that flow, in return, can dramatically impact their colony morphology and spatial population genetics. We show that yeast cells generate fluid flows by consuming surrounding nutrients and decreasing the local substrate density, leading to misaligned fluid pressure and density contours, which ultimately generates vorticity via a thresholdless baroclinic instability. Numerical simulations demonstrate that an intense vortex ring is produced below the colony's edge and quantitatively predict the observed flow. As the viscosity of the substrate is lowered and the self-induced flow intensifies, we observe three distinct morphologies: at the highest viscosity,compact circular colonies similar to those grown on hard agar plates except with a stretched regime of exponential expansion, intermediate viscosities give rise to compact colonies with "fingers" that are ripped away to break into smaller cell clusters, and at the lowest viscosity, the expanding colony breaks up into many genetically-diverse, mutually repelling, island-like fragments of yeast colonies.

Threshold responses of grassland and sagebrush birds to patterns of disturbance created by an ecosystem engineer

Burrowing mammals play a role in rangeland disturbance worldwide, enhancing habitat for certain species while negatively affecting others. However, little is known concerning effects of disturbance spatial pattern on co-occuring fauna. In the North American Great Plains, colonial black-tailed prairie dogs (Cynomys ludovicianus) may enhance habitat for one suite of birds while degrading habitat for others. We examined the influence of prairie dogs on birds in a mosaic grassland–shrubland landscape. We evaluated how birds associated with shortgrass, midgrass, and sagebrush (Artemisia spp.) plant communities respond to spatial pattern of prairie dog disturbance and identified thresholds where abundance changes. We surveyed bird abundance on prairie dog colonies of varying sizes and shapes, across colony edges into undisturbed habitat, and within undisturbed sagebrush in northeastern Wyoming. We modeled species responses to colony presence, distance to colony edge, and total area and edge density of colonies at four spatial scales (100 m, 225 m, 500 m, 1000 m). Sagebrush specialists like Brewer’s sparrow (Spizella breweri) and sage thrasher (Oreoscoptes montanus) were 4.5 times more abundant in undisturbed shrublands. Conversely, the shortgrass-specialist mountain plover (Charadrius montanus) was abundant on colonies but showed a non-linear response to colony edge, increasing in abundance up to 600 m from edges then declining further towards colony cores. While some species may be broadly intolerant to disturbance, disturbance-dependent birds can display a “goldilocks syndrome” relative to disturbance size. As such, management for multiple species of conservation concern can be optimized relative to other goals by identifying thresholds associated with the effect of disturbance.

Isolation and Identification of Hydrocarbon Degradation Bacteria and Phosphate Solubilizing Bacteria in Oil Contaminated Soil in Bojonegoro, East Java, Indonesia

Petroleum is a mixture of hydrocarbon complexes with organic compounds from sulfur, oxygen, nitrogen and metal-containing compounds. These organic compounds can be used as substrate for bacterial growth. This study aimed to isolate and identify hydrocarbon degrading bacteria and phosphate solubilizing bacteria in oil-contaminated soil in Bojonegoro. This study used an exploration method to find each of the two types of hydrocarbon degrading bacteria and phosphate solubilizing bacteria from soil samples in Bojonegoro that contaminated by oil. Identification of isolates bacterial included macroscopic observations of bacteria, gram staining on bacterial cells and physiological tests. Macroscopic observations include the form of colonies, colony diameter, colony color, colony edge, and elevation. The physiological test using Microbact Identification System to determine the physiological characteristics of bacteria so that genera and types of bacteria can be known. The identification of organisms was based on changes in pH and use of the substrate. The results of data analysis were obtained from five types of bacteria from soil samples that contaminated by oil which were successfully isolated. After identification of species was done, four species of bacteria were obtained, namely Pseudomonas pseudomallei, Pseudomonas fluorescens-25, Flavobacterium odoratum, and Enterococcus sp.

Isolation and Characteristics of Corn-Based Cellulolytic Fungi as Fibrous Feed Bioactivators

Microbes live in nature freely in water, air, or soil. One type of microbe is fungi. Fungi are microorganisms that are able to degrade fiber. This study aims to isolate fungi from corn waste and test the degradation ability of the best corn waste fungi fiber as a fibrous feed bioactivator. This research was carried out at the Laboratory of Animal Production, Faculty of Agriculture, Animal Husbandry Study Program, University of North Sumatra, in March 2018 - June 2018. This study used corn waste (corn cobs, corn straw, corn husk, corn flowers and corn roots). Parameters observed were macroscopic morphology (colony size, colony shape, clony color, colony elevation, colony edge), microscopic morphology (form of hyphae, conidial shape, and conidiophoric surface) and the ability to degrade fiber in fungi. Conclusions from the results of research on corn waste exploration obtained 6 fungi isolates, 4 of which were cellulolytic fungi that were able to degrade fibrous feed, namely two strains of Aspergillus sp., Fusarium sp., And Rizoctonia sp. Isolates which have a potential to degrade fiber are JE isolates (Rizoctonia sp. fungi) with a cellulolytic index of 1,178.

A model for target acquisition and edge detection under complex scenes

For the needs of target acquisition and edge extraction under complex scenes, a method based on layer by layer segmentation is proposed. First of all, morphological reconstruction technology is combined with ant colony edge detection method to execute pre-segmentation to get the foreground that targets locate. Secondly, line scanning technique is used to divide foreground into several parts for further segmentation. And then, mean difference characteristic is adopted to determine seed point, with which region growing algorithm is applied to find true targets. Finally, active contour method is used to find out the edge of targets. The experimental results show that our method is effective in finding the target and extracting its edge under complex scenes.

Internal structure and photosynthetic performance of Nostoc sp. colonies in the high Arctic

The physiological performance of <em>Nostoc</em> sp. colonies in the high Arctic was investigated based on their structure and function. To investigate the internal colony structure, a method based on vertical stacking of individual light microscopy images was tested under the conditions at a polar field station. The physiological state of sun-exposed and shaded surfaces of the colonies was assessed using variable chlorophyll fluorescence imaging under two distinct low- and high-light conditions. The 3D image of the internal structure of the colonies revealed a high number of cells in the central part of the colony. Two peaks of maximum cell density were observed, probably caused by two overlapping colony lobes or subcolonies. Light was the driving factor of photosynthetic activity, and the colony structure played a role in the rate of response to incoming light. Fluorescence imaging revealed heterogeneity of the photosynthetic activity in the colonies, with the maximum photosynthetic activity at the colony edge due to better access to nutrients. The differences between exposed and shaded surfaces were not as pronounced as was expected, either due to good photoacclimation to a broad range of light conditions, light distribution through translucent extracellular matrixes, or integration of fluorescence signals throughout the colonies. The slightly better photosynthetic performance under high light conditions may indicate photoacclimation of <em>Nostoc</em> sp. to a broad range of light conditions encountered in the field.

Collective motion conceals fitness differences in crowded cellular populations.

Many cellular populations are tightly-packed, such as microbial colonies and biofilms, or tissues and tumors in multicellular organisms. Movement of one cell in those crowded assemblages requires motion of others, so that cell displacements are correlated over many cell diameters. Whenever movement is important for survival or growth, these correlated rearrangements could couple the evolutionary fate of different lineages. Yet, little is known about the interplay between mechanical forces and evolution in dense cellular populations. Here, by tracking slower-growing clones at the expanding edge of yeast colonies, we show that the collective motion of cells prevents costly mutations from being weeded out rapidly. Joint pushing by neighboring cells generates correlated movements that suppress the differential displacements required for selection to act. This mechanical screening of fitness differences allows slower-growing mutants to leave more descendants than expected under non-mechanical models, thereby increasing their chance for evolutionary rescue. Our work suggests that, in crowded populations, cells cooperate with surrounding neighbors through inevitable mechanical interactions. This effect has to be considered when predicting evolutionary outcomes, such as the emergence of drug resistance or cancer evolution.

Central–periphery gradient of individual quality within a colony of Black‐headed Gulls

Central nesting sites within avian colonies are often more profitable in terms of fitness, as they can offer better protection against predators compared with colony edges. Thus, central sites are expected to attract high‐quality individuals, which should produce a clear central–periphery gradient in the phenotypic quality of nesting individuals and reproductive output within colonies. The aim of this study was to assess spatial patterns of individual quality within a colony of a common larid, the Black‐headed GullChroicocephalus ridibundus. We found that laying was advanced in the central zone of the colony when compared with the periphery, and central pairs tended to lay larger eggs and had higher hatching success than peripheral pairs. Centrally nesting individuals had higher blood haemoglobin concentrations, size‐corrected body mass and heterozygosity (males only), indicating their better condition and higher genetic quality. In contrast, central females had lower plasma albumin concentration, which could possibly be attributed to their greater investment in egg production. Finally, pairs breeding in the central zone of the colony had an elevated heterophil/lymphocyte ratio, suggesting that social stress can be recognized as an important cost of nesting in dense aggregations. The results provide empirical support for central–periphery gradients in the individual quality of colonially nesting Black‐headed Gulls, indicating that spatial gradients in pair quality should be carefully taken into account when conducting research on colonial birds.

Substrate elasticity dependent colony formation and cardiac differentiation of human induced pluripotent stem cells

Substrate elasticity regulates cell functions including cell aggregation and stem cell differentiation. The ability to manufacture substrates of desired elasticity over a broad range is therefore crucial for both fundamental research and advanced applications. In this work, we developed a method to fabricate dense elastomer pillars of different heights on a rigid substrate, providing an effective elasticity ranging from 3 to 168 kPa. Assisted with an elastomer stencil of honeycomb pattern for cell seeding, we obtained uniform colonies of human induced pluripotent stem cells (hiPSCs) and differentiated cardiomyocytes on the pillar substrates of different modulus. Our results showed that the elasticity of substrates significantly affected the cell colony formation via governing the colony edge propagation. More importantly, the results demonstrated that an intermediate substrate elasticity of about 9 kPa is preferable to reach an embryoid-like aggregation and optimal for cardiac differentiation of hiPSCs. Overall, this work sheds new insights on the importance of substrate modulus on cell aggregation and stem cell differentiation as well as the manufacturing of culture substrates with desired elasticity.

First Report of Common Bean (Phaseolus vulgaris) Root Rot Caused by Plectosphaerella cucumerina in China

HomePlant DiseaseVol. 102, No. 9First Report of Common Bean (Phaseolus vulgaris) Root Rot Caused by Plectosphaerella cucumerina in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Common Bean (Phaseolus vulgaris) Root Rot Caused by Plectosphaerella cucumerina in ChinaL. Yang, X. H. Lu, S. D. Li, and B. M. WuL. Yanghttp://orcid.org/0000-0002-7673-679XSearch for more papers by this author, X. H. LuSearch for more papers by this author, S. D. Li†Corresponding authors: S. D. Li, E-mail: E-mail Address: [email protected]; and B. M. Wu, E-mail: E-mail Address: [email protected]Search for more papers by this author, and B. M. Wu†Corresponding authors: S. D. Li, E-mail: E-mail Address: [email protected]; and B. M. Wu, E-mail: E-mail Address: [email protected]Search for more papers by this authorAffiliationsAuthors and Affiliations L. Yang , Department of Plant Pathology, China Agricultural University, Beijing 100193, China X. H. Lu S. D. Li † , Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193 B. M. Wu † , Department of Plant Pathology, China Agricultural University, Beijing 100193. Published Online:21 Jun 2018https://doi.org/10.1094/PDIS-10-17-1659-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In March 2016, root rot was observed on common bean (Phaseolus vulgaris L.) samples (cultivar Shuangqing 38) collected from a commercial farm in Sanya City, Hainan Province, China. The incidence of this disease in the field was about 30%. The symptoms of infected plants included dwarf and yellowing aboveground; irregular, scaled, black-brown lesions on roots; and lack of lateral roots. Symptomatic root tissues were excised from four plants, cut into 1-cm pieces, surface sterilized with 1% NaClO for 2 min, rinsed in sterilized distilled water three times, and then placed on potato dextrose agar (PDA) plates. After incubation at 25°C for 7 days, hyphal tips from the colony edge were transferred to a fresh PDA plate, and a total of 13 isolates were obtained. Morphological and molecular identification indicated that 11 of these isolates from four plants were fungal species previously reported on common bean, and the other two from two individual plants were Plectosphaerella cucumerina. The colonies of these two isolates were pink and moist with appressed and slimy mycelium. Hyphae were transparent and branched. Numerous hyphae anastomosed frequently and formed hyphal coils. Conidiogenous cells were monophialides. Conidia were hyaline, measured 4.0 to 9.8 × 2.0 to 4.3 μm, 0 to 1 septate, ellipsoid or long ellipsoid dwindling gradually from the middle toward the apex, gathering together to form a capitulum (Palm et al. 1995). The internal transcribed spacer (ITS) regions of ribosomal DNA were amplified from the two isolates with the primer pair ITS1/ITS4 (White et al. 1990) and then sequenced. The sequences of the two isolates were identical (accession no. MF669723) and showed 99% identity to sequence KP407871 of P. cucumerina (strain KX37). To test the pathogenicity of these isolates, seeds of common bean (cultivar Baifeng) were sown in 4 × 3-cm plastic pots with sterilized nursery soil and were inoculated with a wheat kernel colonized with the fungi placed adjacent to each seed. Seeds sown with sterilized, noncolonized wheat kernels were used as controls. Three replicates with a total of 15 plants for each isolate were included. The trays were then maintained in a greenhouse with a 12-h photoperiod at 25°C. No symptoms developed on the aboveground parts in 10 days, but the roots of all plants inoculated showed black lesions similar to those originally observed in the field. Using the same methods described above, P. cucumerina was reisolated from these lesions. Control plants remained healthy, and no P. cucumerina was reisolated. In 2017, P. cucumerina was also isolated from common bean roots (cultivar English Red) with similar symptoms in two fields in Kelan County, Shanxi Province, China. To our knowledge, this is the first report of P. cucumerina causing root rot of common bean in China, although it has been reported on other crops (Gao et al. 2016; Li et al. 2017; Yan et al. 2016). It is important to study the impacts of this new disease on common bean production in China for the potential infestation of the pathogen.

Cytotoxicity of Clostridium perfringens enterotoxin depends on the conditions of claudin-4 in ovarian carcinoma cells

Currently, Clostridium perfringens enterotoxin (CPE) is being investigated as an anti-cancer drug for tumors expressing the tight junction (TJ) transmembrane proteins claudin-3 and/or claudin-4. However, the optimal conditions for CPE cytotoxicity are still unclear. Our objectives were to determine the optimal conditions for CPE as an anti-cancer drug for treating ovarian cancer in vitro and in vivo. In our experiments, cells at low culture density showed higher sensitivity to CPE, suggesting that claudins at TJs were poorly accessible to CPE compared with those at the edge of cell colonies. Ovarian cancer cells cultured under calcium-depleted pretreatment conditions to disrupt TJs and to knock-down TJ proteins and E-cadherin production altered CPE cytotoxicity, which was mainly dependent on claudin-4 expression. These results suggest that the condition of claudin-4 at the cell surface is important for CPE cytotoxicity. Our in vivo experiments showed that a high dose of CPE is required for the effective treatment of peritoneal dissemination of ovarian cancer cells. Here, we suggest that the accessibility of CPE to claudins is important for its cytotoxicity and depends on the conditions of claudin-4 in vitro. In addition, E-cadherin expression in ovarian cancer cells affects the efficiency of CPE in vivo.

A new edge detection approach via neutrosophy based on maximum norm entropy

It is a quite important step to find object edges in applications such as object recognition, classification and segmentation. Therefore, the edge detection algorithm to be used directly influences the performance of these applications. In this study, a new edge detection method based on Neutrosophic Set (NS) structure via using maximum norm entropy (EDA-NMNE) is proposed. Many experts and intelligence systems, including the fuzzy system, do not satisfactorily succeed in resolving indeterminacies and deficiencies. However, in the NS approach, problems are solved by dividing them into True (T), False (F) and Indeterminacy (I) subsets. In addition, because the approach has a powerful algorithmic structure, NS's conditions with indeterminate and missing situations can be solved successfully. In this study, object edges can be found successfully with the proposed approach because edges of the object are considered as indeterminate. Thus, using the proposed EDA-NMNE, a strong intelligent expert system-based edge finding software was designed. In our study, 5 different object edge detection results were obtained by converting 5 different types of entropy into NS-based edge detection software. Thus, edge detection analysis has been performed by experimenting many types of entropy that have not been previously used for NS edge detection. The Metric Figure of Merit (FOM), Peak Signal-to-Noise Ratio (PSNR) analysis, mean square error (MSE) were used in this experimental study. Based on these results, highest FOM and PSNR values are obtained by using NORM entropy. In addition, the proposed edge detection approach were compared with Edge Detection Approach via Canny (EDA-C), Edge Detection Approach via Sobel (EDA-S), Edge Detection Approach via Variation-Adaptive Ant Colony Optimization (EDA-VAACO) and Edge Detection Approach via Active Contour without Edge (EDA-ACWE). FOM and PSNR tests have been used to evaluate the edge detection results obtained via 5 different methods. The findings demonstrated that the performance of the proposed edge detection approach is more successful compared to other methods.

Spatial Proliferation of Epithelial Cells Is Regulated by E-Cadherin Force

Cell proliferation and contact inhibition play a major role in maintaining epithelial cell homeostasis. Prior experiments have shown that externally applied forces, such as stretch, result in increased proliferation in an E-cadherin force-dependent manner. In this study, the spatial regulation of cell proliferation in large epithelial colonies was examined. Surprisingly, cells at the center of the colony still had increased proliferation as compared to cells in confluent monolayers. E-cadherin forces were found to be elevated for both cells at the edge and center of these larger colonies when compared to confluent monolayers. To determine if high levels of E-cadherin force were necessary to induce proliferation at the center of the colony, a lower-force mutant of E-cadherin was developed. Cells with lower E-cadherin force had significantly reduced proliferation for cells at the center of the colony but minimal differences for cells at the edges of the colony. Similarly, increasing substrate stiffness was found to increase E-cadherin force and increase the proliferation rate across the colony. Taken together, these results show that forces through cell-cell junctions regulate proliferation across large groups of epithelial cells. In addition, an important finding of this study is that junction forces are dynamic and modulate cellular function even in the absence of externally applied loads.