Ecological connectivity analysis based on the fish community in Jeongan Stream

This study focused on the longitudinal connectivity analysis, based on fish communities in the aspect of spatial variations of 34 sites from upstream to downstream. The Fish Assessment Index (FAI), based on ecological guilds and species composition, was applied to compare the ecological health among the sampling sites. The total number of 35 fish species, were sampled during the study period with dominant species of Zacco platypus (35.4%) and Zacco koreanus (11.8%). Cluster analysis showed that all sites were categorized as 4 distinct group communities (A, B, C, D). Non-metric multidimensional scaling analysis showed distinct difference between upstream (A, B) and downstream groups (C, D). Indicator Value Analysis (IndVal method), conducted to identify indicator species within each group, indicated that the species favoring upstream environments Rhynchocypris oxycephalus for the Group A and Iksookimia koreensis for the Group B. In contrast, the analysis indicated that the species with a preference for downstream habitats Pseudogobio esocinus for the Group C and Carassius auratus for the Group D. Ecological health, based on the FAI scores, showed a declining pattern toward the downstream, along with an increasing proportion of tolerant species and omnivores within the fish community. Overall these findings suggest the compositions of fish communities, as four groups, were modified by the weir structures and organic matter, nutrient pollutions

The Antibacterial Assay of Tectorigenin with Detergents or ATPase Inhibitors against Methicillin-Resistant Staphylococcus aureus

Tectorigenin (TTR) is an O-methylated isoflavone derived from the rhizome of Belamacanda chinensis (L.) DC. It is known to perform a wide spectrum of biological activities such as antioxidant, anti-inflammatory, anti-tumor. The aim of this study is to examine the mechanism of antibacterial activity of TTR against methicillin-resistant Staphylococcus aureus (MRSA). The anti-MRSA activity of TTR was analyzed in combination assays with detergent, ATPase inhibitors, and peptidoglycan (PGN) derived from S. aureus. Transmission electron microscopy (TEM) was used to monitor survival characteristics and changes in S. aureus morphology. The MIC values of TTR against all the tested strains were 125 μg/mL. The OD(600) of each suspension treated with a combination of Triton X-100, DCCD, and NaN3 with TTR (1/10 × MIC) had been reduced from 68% to 80%, compared to the TTR alone. At a concentration of 125 μg/mL, PGN blocked antibacterial activity of TTR. This study indicates that anti-MRSA action of TTR is closely related to cytoplasmic membrane permeability and ABC transporter, and PGN at 125 μg/mL directly bind to and inhibit TTR at 62.5 μg/mL. These results can be important indication in study on antimicrobial activity mechanism against multidrug resistant strains

Spatiotemporal Variation Analyses of Water Quality, Fish Ecological Guilds, and the Longitudinal Connectivity in Musim Stream

The main objectives of this study were to analyze the spatiotemporal variations of water quality, fish ecological guilds and longitudinal connectivity in the weirs of Musim Stream. Fish were collected at 44 sites during spring and fall seasons for the analysis of trophic guilds, tolerance guilds, and the ecological stream health, based on FAI model. Total 33 species were observed in the stream and the dominant species were Zacco platypus and Squalidus qracilis majimae. Mean values of BOD and COD, as an indicator of organic matter pollution, showed high in the drought spring and low in fall (post-monsoon season). Also, TP showed same pattern with the BOD and COD pattern. The hierarchical clustering, based on the fish compositions, classified as three groups (up-stream, mid-stream and the down-stream). Based on the NMDS (Non-metric Multidimensional Scaling) analysis of fish abundance, high similarity was observed between S1-S5 sites, which were consistent with the results of hierarchical cluster analysis. Fish ecological guilds in the upper stream showed a high similarity between the insectivore and sensitive species, while in the middle and lower reaches, high similarity was found between the omnivore and intermediate species. Evaluations of longitudinal connectivity, based on the structural and hydrological characteristics of the weir, indicated all disconnections by the weirs, except for S15, in the spring. Stream ecological health, based on the FAI model, was significantly (p < 0.05, n=37) influenced by the height of overflow (Hu1). Overall, our study suggests that the longitudinal connectivity, based on the weir structures, flow regime and fish swimming capacity, were blocked off by the weirs in the stream. The results provide valuable insights for securing river management strategies and served as the fundamental data for stream restoration in the future

Combination Therapy of Sophoraflavanone B against MRSA: In Vitro Synergy Testing

Sophoraflavanone B (SPF-B), a known prenylated flavonoid, was isolated from the roots of Desmodium caudatum. The aim of this study was to determine the antimicrobial synergism of SPF-B combined with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). MRSA, a multidrug-resistant pathogen, causes both hospital- and community-acquired infections worldwide. The antimicrobial activity of SPF-B was assessed by the broth microdilution method, checkerboard dilution test, and time-kill curve assay. The MIC of SPF-B for 7 strains of S. aureus ranges from 15.6 to 31.25 μg/mL determined. In the checkerboard method, the combinations of SPF-B with antibiotics had a synergistic effect; SPF-B markedly reduced the MICs of the β-lactam antibiotics: ampicillin (AMP) and oxacillin (OXI); aminoglycosides gentamicin (GET); quinolones ciprofloxacin (CIP) and norfloxacin (NOR) against MRSA. The time-kill curves assay showed that a combined SPF-B and selected antibiotics treatment reduced the bacterial counts below the lowest detectable limit after 24 h. These data suggest that the antibacterial activity of SPF-B against MRSA can be effectively increased through its combination with three groups of antibiotics (β-lactams, aminoglycosides, and quinolones). Our research can be a valuable and significant source for the development of a new antibacterial drug with low MRSA resistance