Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads?

We assessed the occurrence of algae in five species of tank-bromeliads found in contrasting environmental sites in a Neotropical, primary rainforest around the Nouragues Research Station, French Guiana. The distributions of both algal abundance and biomass were examined based on physical parameters, the morphological characteristics of bromeliad species and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved in all of the bromeliad species with mean densities ranging from ∼102 to 104 cells/mL. Their biomass was positively correlated to light exposure and bacterial biomass. Algae represented a tiny component of the detrital food web in shaded bromeliads but accounted for up to 30 percent of the living microbial carbon in the tanks of Catopsis berteroniana, located in a highly exposed area. Thus, while nutrient supplies are believed to originate from wind-borne particles and trapped insects (i.e., allochtonous organic matter), our results indicate that primary producers (i.e., autochtonous organic matter) are present in this insectivorous bromeliad. Using a 24-h incubation of size-fractionated and manipulated samples from this plant, we evaluated the impact of mosquito foraging on algae, other microorganisms and rotifers. The prey assemblages were greatly altered by the predation of mosquito larvae. Grazing losses indicated that the dominant algal taxon, Bumilleriopsis sp., like protozoa and rotifers, is a significant part of the diet of mosquito larvae. We conclude that algae are a relevant functional community of the aquatic food web in C. berteroniana and might form the basis of a complementary non-detrital food web

Is There a Seamount Effect on Microbial Community Structure and Biomass? The Case Study of Seine and Sedlo Seamounts (Northeast Atlantic)

Seamounts are considered to be “hotspots” of marine life but, their role in oceans primary productivity is still under discussion. We have studied the microbial community structure and biomass of the epipelagic zone (0–150 m) at two northeast Atlantic seamounts (Seine and Sedlo) and compared those with the surrounding ocean. Results from two cruises to Sedlo and three to Seine are presented. Main results show large temporal and spatial microbial community variability on both seamounts. Both Seine and Sedlo heterotrophic community (abundance and biomass) dominate during winter and summer months, representing 75% (Sedlo, July) to 86% (Seine, November) of the total plankton biomass. In Seine, during springtime the contribution to total plankton biomass is similar (47% autotrophic and 53% heterotrophic). Both seamounts present an autotrophic community structure dominated by small cells (nano and picophytoplankton). It is also during spring that a relatively important contribution (26%) of large cells to total autotrophic biomass is found. In some cases, a “seamount effect” is observed on Seine and Sedlo microbial community structure and biomass. In Seine this is only observed during spring through enhancement of large autotrophic cells at the summit and seamount stations. In Sedlo, and despite the observed low biomasses, some clear peaks of picoplankton at the summit or at stations within the seamount area are also observed during summer. Our results suggest that the dominance of heterotrophs is presumably related to the trapping effect of organic matter by seamounts. Nevertheless, the complex circulation around both seamounts with the presence of different sources of mesoscale variability (e.g. presence of meddies, intrusion of African upwelling water) may have contributed to the different patterns of distribution, abundances and also changes observed in the microbial community

The Sorcerer II Global Ocean Sampling Expedition: Metagenomic Characterization of Viruses within Aquatic Microbial Samples

Viruses are the most abundant biological entities on our planet. Interactions between viruses and their hosts impact several important biological processes in the world's oceans such as horizontal gene transfer, microbial diversity and biogeochemical cycling. Interrogation of microbial metagenomic sequence data collected as part of the Sorcerer II Global Ocean Expedition (GOS) revealed a high abundance of viral sequences, representing approximately 3% of the total predicted proteins. Cluster analyses of the viral sequences revealed hundreds to thousands of viral genes encoding various metabolic and cellular functions. Quantitative analyses of viral genes of host origin performed on the viral fraction of aquatic samples confirmed the viral nature of these sequences and suggested that significant portions of aquatic viral communities behave as reservoirs of such genetic material. Distributional and phylogenetic analyses of these host-derived viral sequences also suggested that viral acquisition of environmentally relevant genes of host origin is a more abundant and widespread phenomenon than previously appreciated. The predominant viral sequences identified within microbial fractions originated from tailed bacteriophages and exhibited varying global distributions according to viral family. Recruitment of GOS viral sequence fragments against 27 complete aquatic viral genomes revealed that only one reference bacteriophage genome was highly abundant and was closely related, but not identical, to the cyanomyovirus P-SSM4. The co-distribution across all sampling sites of P-SSM4-like sequences with the dominant ecotype of its host, Prochlorococcus supports the classification of the viral sequences as P-SSM4-like and suggests that this virus may influence the abundance, distribution and diversity of one of the most dominant components of picophytoplankton in oligotrophic oceans. In summary, the abundance and broad geographical distribution of viral sequences within microbial fractions, the prevalence of genes among viral sequences that encode microbial physiological function and their distinct phylogenetic distribution lend strong support to the notion that viral-mediated gene acquisition is a common and ongoing mechanism for generating microbial diversity in the marine environment

New mono and bimetallic chloroquine derivatives : synthesis and evaluation as antiparasitic agents

Includes bibliographical references.Several series of new ferrocenyl-quinoline antimalarial agents have been synthesised and fully characterised using standard spectroscopic and analytical techniques. The molecular structure of N-(7-Chloro-quinolin-4-yl)-N'-[2 -( N”,N""-dimethylaminomethyl)ferrocenylmethyl]-ethane-1.2-diamine has been determined by x-ray crystallography. N-(7-Chloro-quinolin-4-yl)-N'-[2-( N”, N""-dimethylaminomethyl)ferrocenylmethyl]-alkyl-1 ,n-diamine compounds were made where n = 2-6. These compounds contain a reactive secondary amine centre through which derivatisation to form aryl urea and aryl sulfonamide compounds was achieved. Complexes of the types: triphenylphosphine(L)gold(l) nitrate, pentafluorophenyl(L)gold(l) and chloro(cyclooctadiene)(L)rhodium(l) have been synthesised (where L = chloroquine, ferroquine, N-(7-chloro-quinolin-4-yl)-N'-[2-( N”, N""-dimethylaminomethyl)ferrocenyl methyl]-ethane-1 ,2-diamine, 3-benzyl-1-[2-(7-chloro-quinolin-4-ylamino)-ethyl]-1-[2-(N"",N""-dimethylaminomethyl)-ferrocenylmethyl]urea). All compounds have been evaluated against chloroquine sensitive and chloroquine resistant strains of Plasmodium falciparum. In most cases good activity was found in both strains of the parasite. N-(7-Chloro-quinol in-4-yl)-N'-[2 -( N”, N""-dimethylaminomethyl)ferrocenyl methyl]-alkyl-1, n-diamine compounds have been made where n = 2-6. It was found that in vitro efficacy against P. falciparum diminished with increasing spacer length. The introduction of the aryl urea moiety served to influence efficacy towards P. falciparum and toxicity towards mammalian cells. In some cases the toxicity was significantly reduced accompanied by an improvement in efficacy. The coordination complexes where L = chloroquine showed improved efficacy in the chloroquine resistant K1 strain of P. falciparum. In the heterobimetallic complexes, the ligand L showed equivalent or better in vitro efficacy than the coordination complexes of L against both chloroquine sensitive D10 and chloroquine resistant K1 strains of P. falciparum. Preliminary structure-activity studies were carried out on some of the prepared compounds. Phenylene analogues of some of the ferrocenyl compounds have been synthesized and it was found that the analogues show similar in vitro efficacy to each other in both chloroquine sensitive 3D7 and chloroquine resistant K1 strains of P. falciparum. The presence of a ferrocenyl moiety in the side chain of chloroquine analogues appears to have a synergistic or additive effect on in vitro efficacy