River to river: First evidence of eel movement between distant rivers via the sea

Environmental Biology of Fishes - Eel movement patterns have been frequently studied to learn about their movements within the fresh- and brackish waters of the same river before their spawning...     

Correction to: River to river: First evidence of eel movement between distant rivers via the sea

Environmental Biology of Fishes - A Correction to this paper has been published: https://doi.org/10.1007/s10641-021-01108-5     

Emergence of scale-free leadership structure in social recommender systems

The study of the organization of social networks is important for the understanding of opinion formation, rumor spreading, and the emergence of trends and fashion. This paper reports empirical analysis of networks extracted from four leading sites with social functionality (Delicious, Flickr, Twitter and YouTube) and shows that they all display a scale-free leadership structure. To reproduce this feature, we propose an adaptive network model driven by social recommending. Artificial agent-based simulations of this model highlight a "good get richer" mechanism where users with broad interests and good judgments are likely to become popular leaders for the others. Simulations also indicate that the studied social recommendation mechanism can gradually improve the user experience by adapting to tastes of its users. Finally we outline implications for real online resource-sharing systems.     

Network-Driven Reputation in Online Scientific Communities

The ever-increasing quantity and complexity of scientific production have made it difficult for researchers to keep track of advances in their own fields. This, together with growing popularity of online scientific communities, calls for the development of effective information filtering tools. We propose here an algorithm which simultaneously computes reputation of users and fitness of papers in a bipartite network representing an online scientific community. Evaluation on artificially-generated data and real data from the Econophysics Forum is used to determine the method''s best-performing variants. We show that when the input data is extended to a multilayer network including users, papers and authors and the algorithm is correspondingly modified, the resulting performance improves on multiple levels. In particular, top papers have higher citation count and top authors have higher h-index than top papers and top authors chosen by other algorithms. We finally show that our algorithm is robust against persistent authors (spammers) which makes the method readily applicable to the existing online scientific communities.     

Mechanisms of peroxidase oxidation of o-dianisidine, 3,3',5,5'-tetramethylbenzidine, and o-phenylenediamine in the presence of sodium dodecyl sulfate

Peroxidase oxidation of o-dianisidine, 3,3',5,5'-tetramethylbenzidine, and o-phenylenediamine in the presence of sodium dodecyl sulfate (SDS), an anionic surfactant, was spectrophotometrically studied. It was found that 0.1-100 mM SDS concentrations stabilize intermediates formed in the peroxidase oxidation of these substrates. The cause of the stabilization is an electrostatic interaction between positively charged intermediates and negatively charged surfactant.     

Keratinophilic Fungi Isolated from Soils of Long-Term Fold-Grazed, Degraded Pastures in National Parks of Slovakia

A total of 939 isolates of 11 genera representing 15 species of keratinophilic fungi were isolated and identified from the soils of three long-term fold-grazed pastures in national parks of Slovakia (Pod Ploskou, Strungovy príslop, and Pod Ke?kou) and one non-fold-grazed pasture in sierra Stolicke vrchy (Diel) using the hair-baiting technique. Keratinophilic fungi were present in all soil samples with a prevalence of Trichophyton ajelloi and Paecilomyces lilacinus. These fungi were more abundant in soil from fold-grazed pasture (Strungovy príslop) compared to non-fold-grazed pasture (Diel). The occurrence of the other keratinophilic fungi was substantially lower, likely because of low pH in some soils.     

Soil myxobacteria as a potential source of polyketide-peptide substances

Myxobacteria, a group of antimicrobial producing bacteria, have been successfully cultured and characterized from ten soil samples collected from different parts of Slovakia. A total of 79 myxobacteria belonging to four genera (Myxococcus, Corallococcus, Sorangium, and Polyangium) were isolated based on aspects of their life cycle. Twenty-five of them were purified, fermented, and screened for antimicrobial activities against 11 test microorganisms. Results indicated that crude extracts showed more significant activities against Gram-positive than against Gram-negative bacteria or fungi. Based on a higher degree and broader range of antimicrobial production, the two most potential extracts (K9-5, V3-1) were selected for HPLC fractionation against Micrococcus luteus and Staphylococcus aureus and LC/MS analysis of potential antibiotic metabolites. The analysis resulted in the identification of polyketide-peptide antibiotics, namely corallopyronin A and B (K9-5) and myxalamid B and C (V3-1), which were responsible for important Gram-positive activity in the observed strains. A sequence similarity search through BLAST revealed that these strains showed the highest sequence similarity to Corallococcus coralloides (K9-5, NCBI accession number KX256198) and Myxococcus xanthus (V3-1, NCBI accession number KX256197). Although screening of myxobacteria is laborious, due to difficulties in isolating cultures, this research represented the first report covering the isolation and cultivation of this challenging bacterial group from Slovakian soils as well as the screening of their antimicrobial activity, cultural identification, and secondary metabolite identification.     

Variability in virulence of Beauveria spp. soil isolates against Ostrinia nubilalis

European corn borer (Ostrinia nubilalis) is an important maize pest which is treated mainly by synthetic pesticides with many negative effects for ecosystem and human health. Soil borne entomopathogenic fungi of species belonging to Beauveria genus may provide an alternative strategy for biological control of this pest. In this article, we report results of virulence testing of 46 soil isolates of Beauveria spp. against O. nubilalis in relation to isolates origin and haplotype. All strains were collected from soil using Galleria mellonella bait method. Conidia suspension with concentration 10⁷ conidia in ml was used for virulence test against 4th instar larvae of O. nubilalis at temperature 25°C. After 14 days, mortality of larvae was in the range 34%–96%. Median lethal time LT50 was estimated to 5.5–21.3 days. Mortality was not in relation to habitat or any other environmental parameter of sites where isolates came from. Differences among species were insignificant. Isolates were divided into 8 genetic lineages and 14 haplotypes using sequencing of ITS and Bloc nuclear regions. None of the lineages showed higher mortality than others. Despite more or less virulent isolates being found in each lineage, the three most virulent isolates belonged to the same lineage Beauveria bassiana A3. The four most virulent isolates were compared to commercial isolate GHA to assess medium lethal concentration. LC50 were estimated in range 7.5 × 10⁴ to 9.5 × 10⁵. Three of the four isolates showed equal or greater efficiency than strain GHA.     

Studies in African Cyperaceae 27. Miscellaneous new taxa and combinations

One new form of Fuirena Rottb., one new subspecies of Schoenoplectus Palla and one new variety of Carex L. are described from East Africa, viz. Fuirena leptostachya Oliv. f. nudiflora Lye, Schoenoplectus lateriflorus (Gmel.) Lye ssp. laevinux Lye and Carex bequaertii De Wild. var. maxima Lye. In addition, the following new combinations are made: Fuirena ciliaris (L.) Roxb. f. apetala (Wingfield) Lye, F. stricta Steudel ssp. chlorocarpa (Ridley) Lye, Schoenoplectus rhodesicus (Podlech) Lye, 5. corymbosus (Roem. & Schult.) J. Rayn. var. brachyceras (A. Rich.) Lye, S. confusus (N.E. Br.) Lye var. rogersii (N.E. Br.) Lye, S. erectus (Poiret) J. Rayn, ssp. raynalii (Schuyler) Lye, S. erectus (Poiret) J. Rayn. ssp. sinuatus (Schuyler) Lye, Eleocharis retroflexa (Poiret) Urban ssp. subtilissima (Nelmes) Lye, Machaerina Vahl subgen. Baumea (Gaud.) Lye, Machaerina flexuosa (Bock.) Kern ssp. laevinux (J. Rayn.) Lye, M. montana (J. Rayn.) Lye, M. flexuosa (Böck.) Kern ssp. polyanthemum (Kük.) Lye, Scleria lagoënsis Böck. ssp. canaliculato–triquetra (Böck.) Lye, 5. distans Poiret var. glomerulata (Oliv.) Lye, S. distans Poiret var. chondrocarpa (Nelmes) Lye, S. melanotricha A. Rich. var. grata (Nelmes) Lye, Carex echinochloë Kunze ssp. nyasensis (C. B. Clarke) Lye, C. conferta A. Rich. var. lycurus (K. Schum.) Lye, C. cognata Kunth var. abyssinica (Chiov.) Lye and C. cognata Kunth var. congolensis (Turrill) Lye.