Species richness and interacting factors control invasibility of a marine community

Anthropogenic vectors have moved marine species around the world leading to increased invasions and expanded species'' ranges. The biotic resistance hypothesis of Elton (in The ecology of invasions by animals and plants, 1958) predicts that more diverse communities should have greater resistance to invasions, but experiments have been equivocal. We hypothesized that species richness interacts with other factors to determine experimental outcomes. We manipulated species richness, species composition (native and introduced) and availability of bare space in invertebrate assemblages in a marina in Monterey, CA. Increased species richness significantly interacted with both initial cover of native species and of all organisms to collectively decrease recruitment. Although native species decreased recruitment, introduced species had a similar effect, and we concluded that biotic resistance is conferred by total species richness. We suggest that contradictory conclusions in previous studies about the role of diversity in regulating invasions reflect uncontrolled variables in those experiments that modified the effect of species richness. Our results suggest that patches of low diversity and abundance may facilitate invasions, and that such patches, once colonized by non-indigenous species, can resist both native and non-indigenous species recruitment.     

Complementary approaches to diagnosing marine diseases: a union of the modern and the classic

Linking marine epizootics to a specific aetiology is notoriously difficult. Recent diagnostic successes show that marine disease diagnosis requires both modern, cutting-edge technology (e.g. metagenomics, quantitative real-time PCR) and more classic methods (e.g. transect surveys, histopathology and cell culture). Here, we discuss how this combination of traditional and modern approaches is necessary for rapid and accurate identification of marine diseases, and emphasize how sole reliance on any one technology or technique may lead disease investigations astray. We present diagnostic approaches at different scales, from the macro (environment, community, population and organismal scales) to the micro (tissue, organ, cell and genomic scales). We use disease case studies from a broad range of taxa to illustrate diagnostic successes from combining traditional and modern diagnostic methods. Finally, we recognize the need for increased capacity of centralized databases, networks, data repositories and contingency plans for diagnosis and management of marine disease.     

Cloning and Characterization of Extracellular Metal Protease Gene of the Algicidal Marine Bacterium Pseudoalteromonas sp. Strain A28

The gene (empI) encoding an extracellular metal protease was isolated from a Pseudoalteromonas sp. strain A28 DNA library. The recombinant EmpI protein was expressed in E. coli and purified. Paper-disk assays showed that the purified protease had potent algicidal activity. A skim milk-polyacrylamide gel electrophoresis protease assay showed that the 38-kDa band of protease activity, which co-migrated with purified EmpI and was sensitive to 1,10-phenathroline, was detected in the extracellular supernatant of A28.     

Marine Sediments Illuminate Chlamydiae Diversity and Evolution

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Intertidal and Subtidal Fouling Assemblages in a Patagonian Harbour (Argentina, Southwest Atlantic)

The composition of the early stages of intertidal and subtidal fouling assemblages in Comodoro Rivadavia harbour (Argentina, 45°52′ S, 67°28′ W) and the influence of shore level and season on their structure were analysed. At the beginning of each season, stones were glued to the substratum with epoxy putty and distributed along 4 vertical transects at intervals of 20 m, at 3 levels: upper intertidal, middle intertidal, and subtidal. Substrata remained in the field for 84–100 days. A total of 48 samples (4 seasons × 3 levels × 4 replicates) were analysed. Species richness increased with depth, with 6 taxa in the upper intertidal, 23 in the middle intertidal and 31 in the subtidal. Seasonal differences in richness were less distinct. Green, red and brown algae were the dominant groups. Invertebrates were mainly represented by filter-feeding, sessile organisms, such as cheilostome bryozoans, spirorbid polychaetes and acorn barnacles. The barnacle Balanus glandula and the bryozoan Cryptosula pallasiana were the only non-indigenous species found in this study. Highly significant differences in structure among shore levels and seasons were evidenced by a two-way ANOSIM test. The upper intertidal is characterized by the filamentous green algae Urospora penicilliformis and Ulothrix flacca. The barnacle Balanus glandula is the most abundant species in the middle intertidal. The subtidal is defined mainly by the presence of the spirorbid polychaetes Paralaeospira levinseni and Romanchella perrieri, and the keyhole limpet Fissurella radiosa. Ordination of samples by season was less clear than by shore level.     

Analysis of the ergosterol biosynthesis pathway cloning,molecular characterization and phylogeny of lanosterol 14 α-demethylase (ERG11) gene of Moniliophthora perniciosa

The phytopathogenic fungus Moniliophthora perniciosa (Stahel) Aime & Philips-Mora, causal agent of witches’ broom disease of cocoa, causes countless damage to cocoa production in Brazil. Molecular studies have attempted to identify genes that play important roles in fungal survival and virulence. In this study, sequences deposited in the M. perniciosa Genome Sequencing Project database were analyzed to identify potential biological targets. For the first time, the ergosterol biosynthetic pathway in M. perniciosa was studied and the lanosterol 14α-demethylase gene (ERG11) that encodes the main enzyme of this pathway and is a target for fungicides was cloned, characterized molecularly and its phylogeny analyzed. ERG11 genomic DNA and cDNA were characterized and sequence analysis of the ERG11 protein identified highly conserved domains typical of this enzyme, such as SRS1, SRS4, EXXR and the heme-binding region (HBR). Comparison of the protein sequences and phylogenetic analysis revealed that the M. perniciosa enzyme was most closely related to that of Coprinopsis cinerea.     

Cytochalasins from mangrove endophytic fungi Phomopsis spp. xy21 and xy22

Chemical investigation of the mangrove fungal endophytes, Phomopsis spp. xy21 and xy22, afforded four new cytochalasins, named phomopsichalasins D-G, along with six known analogues. The structures of these cytochalasins were elucidated on the basis of HRESIMS and extensive NMR spectroscopic data. Phomopsichalasins D (1) and E (2) represent the first two 10-phenyl[11]-cytochalasans containing a 12-carboxyl function. All of the isolates were evaluated for their cytotoxicities against eight human cancer cell lines by the MTT method. Phomopsichalasin G (4) exhibited inhibitory activities against HCT-8, HCT-8/T, A549, MDA-MB-231, and A2780 cancer cell lines with IC₅₀ values of 7.5, 8.6, 6.4, 3.4, and 7.1 μM, respectively.