Large-scale climatic phenomena drive fluctuations in macroinvertebrate assemblages in lowland tropical streams, Costa Rica: The importance of ENSO events in determining long-term (15y) patterns

Understanding how environmental variables influence the distribution and density of organisms over relatively long temporal scales is a central question in ecology given increased climatic variability (e.g., precipitation, ENSO events). The primary goal of our study was to evaluate long-term (15y time span) patterns of climate, as well as environmental parameters in two Neotropical streams in lowland Costa Rica, to assess potential effects on aquatic macroinvertebrates. We also examined the relative effects of an 8y whole-stream P-enrichment experiment on macroinvertebrate assemblages against the backdrop of this long-term study. Climate, environmental variables and macroinvertebrate samples were measured monthly for 7y and then quarterly for an additional 8y in each stream. Temporal patterns in climatic and environmental variables showed high variability over time, without clear inter-annual or intra-annual patterns. Macroinvertebrate richness and abundance decreased with increasing discharge and was positively related to the number of days since the last high discharge event. Findings show that fluctuations in stream physicochemistry and macroinvertebrate assemblage structure are ultimately the result of large-scale climatic phenomena, such as ENSO events, while the 8y P-enrichment did not appear to affect macroinvertebrates. Our study demonstrates that Neotropical lowland streams are highly dynamic and not as stable as is commonly presumed, with high intra- and inter-annual variability in environmental parameters that change the structure and composition of freshwater macroinvertebrate assemblages.This study was financed by National Science Foundation (DEB 1122389) to Catherine M. Pringle. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR

Rhamnolipids as an alternative fungicide against plant pathogens.

Rhamnolipids are potent natural glycolipid biosurfactants often biosynthesized by Pseudomonas aeruginosa strains through the fermentation process. As biologically produced molecules, Rhamnolipids are generally reported to have less impact on the environment than conventional surfactants, are usually much better biodegradable and show less toxicity than synthetic surfactants. Rhamnolipids are consisted by one or two L-rhamnose molecules as the hydrophilic portion (Monorhamnolipids (Rha-C10? C10) and Dirhamnolipids (Rha-Rha-C10?C10)) and by a fatty acid moiety, saturaded or insaturated, with range between C8 and C12[1] as the hydrophobic portion. Many Rhamnolipids have been established as an effective source against Gram-negative, Gram-positive bacteria, fungi [1] and insects [2]. Pseudomonas sp. LPNMS 012 showed an antifungal activity on antagonism and antibiosis bioassay against Colletotrichum gloeosporioides (Figure A-B). Pseudomonas sp. LPNMS 012 was fermented for five days on PD medium, at 200 rpm and 28 ºC. After that, the culture medium was submitted to solid phase extraction at C18 resin and extracted with methanol. The crude extract generated was analyzed by High Performance Liquid Chromatography coupled with Tandem Mass Spectrometry (Acquity Xevo TQ-S, Waters) in both ESI+ and ESI- modes. The mass spectra (Figure C) displayed an arrangement of peaks appointed to Dirhamnolipid (Figure B) (m/z 673 [M+Na+]+ and m/z 649 [M-H+]-). The chromatogram also displayed a pattern of separation of Monorhamnolipids (527 m/z) and Dirhamnolipid (673 m/z) in ESI+ mode (Figure D)

Biological screening to identify antifungal agents produced by Streptomyces sp. isolated from the Caatinga Biome.

Microbial secondary metabolites have been considered a promising natural source to disclose biologically active compounds, which can be applied in the pharmaceutical and agroindustrial sectors. Actinobacterias have played an important role in the historical advances of antibiotics and antifungals development1,2. Besides the wide application in the medicinal field as an antifungal agent, it can be also used as a natural alternative to inhibit the pathogenic microorganism?s growth in agriculture. On the other hand, now concerning the citrus fruits market, an inefficient fungi infection control results in a significant profit loss. This study shows the antibiosis screening assays of 196 microorganism?s crude extracts in order to identify antifungal activity against Colletotrichum gloeosporioides fungi. The Streptomyces sp. Caat 5-35 crude extract presented the highest antifungal activity (Figure 1-A). Mass spectrometry (MS) is an important dereplication process tool of these metabolites in the crude extract. It allows fast and sensitive analysis and provides valuable structural information. The active crude extract was fractionated in a preparative HPLC method and bioassays were performed in all the fractions in order to identify the active fraction. The Fr16 fraction exhibited notable antimicrobial activity by disk diffusion method assay. The chromatogram LC-MS/MS for the active fraction presented only one peak at 5.16 minutes, which corresponds to the ionic species [M+H]+ of m/z 521.2. Spectroscopic UV, NMR 1D and 2D data confirm that the active compound is the Albofungin3