Transovarial transmission of a core virome in the Chagas disease vector Rhodnius prolixus

Triatomine assassin bugs comprise hematophagous insect vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Although the microbiome of these species has been investigated to some extent, only one virus infecting Triatoma infestans has been identified to date. Here, we describe for the first time seven (+) single-strand RNA viruses (RpV1-7) infecting Rhodnius prolixus, a primary vector of Chagas disease in Central and South America. We show that the RpVs belong to the Iflaviridae, Permutotetraviridae and Solemoviridae and are vertically transmitted from the mothers to the progeny via transovarial transmission. Consistent with this, all the RpVs, except RpV2 that is related to the entomopathogenic Slow bee paralysis virus, established persistent infections in our R. prolixus colony. Furthermore, we show that R. prolixus ovaries express 22-nucleotide viral siRNAs (vsiRNAs), but not viral piRNAs, that originate from the processing of dsRNA intermediates during viral replication of the RpVs. Interestingly, the permutotetraviruses and sobemoviruses display shared pools of vsiRNAs that might provide the basis for a cross-immunity system. The vsiRNAs are maternally deposited in the eggs, where they likely contribute to reduce the viral load and protect the developing embryos. Our results unveil for the first time a complex core virome in R. prolixus and begin to shed light on the RNAi-based antiviral defenses in triatomines.     

Summer coastal zooplankton biomass and copepod community structure near the Italian Terra Nova Base (Terra Nova Bay, Ross Sea, Antarctica)

The structure of the zooplankton biotic community and of copepodpopulation in the coastal area of Terra Nova Bay (Ross Sea,Antarctica) was investigated during the 10th Italian AntarcticExpedition (1994/1995). Zooplankton biotic community consistedmainly of pteropods (Limacina helicina and Clione antarctica),Cyclopoid (Oithona similis), Poecilostomatoid (Oncaea curvata)and Calanoid (Ctenocalanus vanus, Paraeuchaeta antarctica, Metridiagerlachei and Stephos longipes) copepods, ostracods, larvalpolychaetes and larval euphausiids. Zooplankton abundance rangedfrom 48.1 ind m^–3 to 5968.9 ind m^–3, and copepodabundance ranged from 45.2 ind m^–3 to 3965.3 ind m^–3.The highest peak of zooplankton abundance was observed between25 m and the surface and was mainly due to the contributionof O. similis, O. curvata and C. vanus. Zooplankton biomassranged from 5.28 mg m^–3 to 13.04 mg m^–3 dry weight;the maximum value was observed between 25 m and the surface.Total lipid content varied from 216.44 to 460.73 mg g^–1dry weight.     

Characterization of Ni transport into brush border membrane vesicles (BBMVs) isolated from the kidney of the freshwater rainbow trout (Oncorhynchus mykiss)

The transport of nickel (Ni) across the renal brush border membrane of the rainbow trout was examined in vitro using brush border membrane vesicles (BBMVs). Both transmembrane transport of Ni into an osmotically active intravesicular space, and binding of Ni to the brush border membrane itself, were confirmed. Nickel (Ni) uptake fitted a two component kinetic model. Saturable, temperature-dependent transport dominated at lower Ni concentrations, with a moderate linear diffusive component of Ni transport apparent at higher Ni concentrations. An affinity constant (K_m) for Ni transport within the specifically described vesicular media was calculated as 17.9 ± 1.9 μM, the maximal rate of transport (J_max) was calculated as 108.3 ± 3.7 nmol mg protein⁻¹ min⁻¹, and the slope of the linear diffusive component was calculated as 0.049 ± 0.005 nmol mg protein⁻¹ min⁻¹ per μM of Ni. Efflux of Ni from BBMVs was fitted to an exponential decay curve with a half-time (T_1/2) of 125.2 ± 7.3 s. Ni uptake into renal BBMVs was inhibited by magnesium at a 100:1 Mg to Ni molar ratio, and by magnesium and calcium at a 1000:1 molar ratio. In the presence of histidine at a 100:1 histidine to Ni ratio, Ni uptake was almost completely abolished. At a 1:1 molar ratio, histidine inhibited Ni uptake by approximately 50%. Ni-histidine complexation was rapid, with a T_1/2 of 12.2 s describing the Ni-histidine equilibration time needed to inhibit Ni uptake into renal BBMVs by 50%. Characterization of Ni transport across cellular membranes is an important step in understanding both the processes underlying homeostatic regulation of Ni, and the toxicological implications of excessive Ni exposure in aquatic ecosystems.     

Persistence of adhesive properties in Vibrio cholerae after long-term exposure to sea water

The effect of exposure to artificial sea water (ASW) on the ability of classical Vibrio cholerae O1 cells to interact with chitin-containing substrates and human intestinal cells was studied. Incubation of vibrios in ASW at 5 degrees C and 18 degrees C resulted in two kinds of cell responses: the viable but non-culturable (VBNC) state (i.e. <0.1 colony forming unit ml-1) at 5 degrees C, and starvation (i.e. maintenance of culturability of the population) at 18 degrees C. The latter remained rod shaped and, after 40 days' incubation, presented a 47-58% reduction in the number of cells attached to chitin, a 48-53% reduction in the number of bacteria adhering to copepods, and a 48-54% reduction in the number of bacteria adhering to human cultured intestinal cells, compared to control cells not suspended in ASW. Bacteria suspended in ASW at 5 degrees C became coccoid and, after 40 days, showed 34-42% fewer cells attached to chitin, 52-55% fewer adhering to copep-ods, and 45-48% fewer cells adhering to intestinal cell monolayers, compared to controls. Sarkosyl-insoluble membrane proteins that bind chitin particles were isolated and analysed by SDS-PAGE. After 40 days incubation in ASW at both 5 degrees C and 18 degrees C vibrios expressed chitin-binding ligands similar to bacteria harvested in the stationary growth phase. It is concluded that as vibrios do not lose adhesive properties after long-term exposure to ASW, it is important to include methods for VBNC bacteria when testing environmental and clinical samples for purposes of public health safety.