Alterations in HIV-1 LTR promoter activity during AIDS progression

AbstractHIV-1 variants evolving in AIDS patients frequently show increased replicative capacity compared to those present during early asymptomatic infection. It is known that late stage HIV-1 variants often show an expanded coreceptor tropism and altered Nef function. In the present study we investigated whether enhanced HIV-1 LTR promoter activity might also evolve during disease progression. Our results demonstrate increased LTR promoter activity after AIDS progression in 3 of 12 HIV-1-infected individuals studied. Further analysis revealed that multiple alterations in the U3 core-enhancer and in the transactivation-response (TAR) region seem to be responsible for the enhanced functional activity. Our findings show that in a subset of HIV-1-infected individuals enhanced LTR transcription contributes to the increased replicative potential of late stage virus isolates and might accelerate disease progression

The influence of temperature and seawater carbonate saturation state on 13C–18O bond ordering in bivalve mollusks

© The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 10 (2013): 4591-4606, doi:10.5194/bg-10-4591-2013.The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ18O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of 13C–18O bond abundance, denoted by the measured parameter Δ47, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a range in water temperatures of 5 to 25 °C, and field collected specimens spanning a range of −1 to 29 °C. In addition we investigate the potential influence of carbonate saturation state on bivalve stable isotope compositions by making measurements on both calcitic and aragonitic specimens that have been cultured in seawater that is either supersaturated or undersaturated with respect to aragonite. We find a robust relationship between Δ47 and growth temperature. We also find that the slope of a linear regression through all the Δ47 data for bivalves plotted against seawater temperature is significantly shallower than previously published inorganic and biogenic carbonate calibration studies produced in our laboratory and go on to discuss the possible sources of this difference. We find that changing seawater saturation state does not have significant effect on the Δ47 of bivalve shell carbonate in two taxa that we examined, and we do not observe significant differences between Δ47-temperature relationships between calcitic and aragonitic taxa.This work was funded by National Science Foundation grants ARC-1215551 to R. A. Eagle and A. K. Tripati, EAR-1024929 to R. A. Eagle and J. M. Eiler, and EAR-0949191 to A. K. Tripati. A. K. Tripati is also supported by the Hellman Fellowship program. Culture of bivalves in Kiel, Germany, was funded by the German Science Foundation (DFG Ei272/21-1, to Anton Eisenhauer) and the European Science Foundation (ESF) Collaborative Research Project CASIOPEIA (04 ECLIM FP08). Determination of bivalve mineralogy by J. B. Ries was funded by National Science Foundation grant OCE-1031995

Decreased depth distribution of Fucus vesiculosus (Phaeophyceae) in the Western Baltic: effects of light deficiency and epibionts on growth and photosynthesis

For many coastal areas of the world, a decrease in abundance and depth penetration of perennial macroalgae and seagrasses has been documented and attributed to eutrophication. A surplus of nutrients impairs perennial seaweeds in at least two ways: increased phytoplankton densities reduce the depth penetration of light and in addition filamentous seaweeds and microalgae growing epiphytically shade their perennial hosts. A reduction of depth limit and total abundance has also been observed for the brown seaweed Fucus vesiculosus at many sites in the Baltic Sea. However, in most cases the mechanistic reason for the loss of Fucus has been deduced from observations rather than from experimental evidence. Here, we present results of a two-factorial (water depth/light supply and epibionts) experiment that was run in the Kiel Fjord, western Baltic, from August to October 2005. Performance of F. vesiculosus was recorded by growth and chlorophyll measurements, PI-curves and in situ measurements of the photosynthetic activity as the relative rate of electron transport (rETR). rETR and growth decreased with water depth. Chlorophyll a concentrations increased with reduced light intensities, but this apparently could not compensate for the light deficiency. Epibionts enhanced the negative effect of reduced light conditions on growth. According to these findings we estimated the physiological depth limit of F. vesiculosus in the Kiel Fjord to lie between 4 and 6 m water depth

Physiological responses to ocean acidification and warming synergistically reduce condition of the common cockle Cerastoderma edule

The combined effect of ocean acidification and warming on the common cockle Cerastoderma edule was investigated in a fully crossed laboratory experiment. Survival of the examined adult organisms remained high and was not affected by elevated temperature (+3 °C) or lowered pH (−0.3 units). However, the morphometric condition index of the cockles incubated under high pCO2 conditions (i.e. combined warming and acidification) was significantly reduced after six weeks of incubation. Respiration rates increased significantly under low pH, with highest rates measured under combined warm and low pH conditions. Calcification decreased significantly under low pH while clearance rates increased significantly under warm conditions and were generally lower in low pH treatments. The observed physiological responses suggest that the reduced food intake under hypercapnia is insufficient to support the higher energy requirements to compensate for the higher costs for basal maintenance and growth in future high pCO2

Patterns of diversity along experimental gradients of disturbance and nutrient supply - the confounding assumptions of the Intermediate Disturbance Hypothesis.

A model of the interactive effects of disturbance and productivity on diversity predicts peak diversity to shift towards higher disturbance regimes as productivity increases, confining the Intermediate Disturbance Hypothesis to intermediate productivity levels. We conducted a two-factorial (disturbance, nutrients) field experiment to test the validity of this model for two subtropical intertidal rocky shores. Treatment responses varied between distinct community types at two sites. Intensified disturbance increased evenness, and under high nutrient enrichment decreased species richness of communities dominated by encrusting algae, whereas turf-dominated communities remained unaffected. Nutrient additions increased biomass and modulated community composition at both sites, in addition to increasing species richness in encrusting-algal and decreasing evenness of turf-forming assemblages. Thus, only highly enriched encrusting-algal communities followed the model predictions. Different mechanisms appear to control species coexistence in different types of communities, some violating the assumptions of the tested model, i.e. resource limitation and competitive exclusion

Salinity driven selection and local adaptation in Baltic Sea Mytilid mussels

Baltic blue mussels can colonise and dominate habitats with far lower salinity (<10 psu) than other Mytilus congeners. Pervasive gene flow was observed between Western Baltic Mytilus edulis living at high salinity conditions and Eastern Baltic M. trossulus living at lower salinites, with highest admixture proportions within a genetic transition zone located at intermediate salinities (Darss Sill area). Yet, we do not understand the impacts of low salinity on larval performance, and how salinity may act as an early selective pressure during passive larval drift across salinity gradients. This study tested whether larvae originating from two different populations along the natural salinity cline in the Baltic Sea have highest fitness at their native salinities. Our results suggest that Eastern Baltic M. trossulus (Usedom, 7 psu) and Western Baltic M. edulis (Kiel, 16 psu) larvae display better performance (fitness components: growth, mortality, settlement success) when reared at their respective native salinities. This suggests that these populations are adapted to their local environment. Additionally, species diagnostic markers were used for genetic analyses of transition zone (Ahrenshoop, 11 psu) mussel larvae exposed to low salinity. This revealed that low salinity selection resulted in a shift towards allele frequencies more typical for Eastern Baltic M. trossulus. Thus, salinity acts as a selective pressure during the pre-settlement phase and can shape the genetic composition of Baltic mussel populations driving local adaptation to low salinity. Future climate change driven desalination, therefore, has the potential to shift the Baltic Sea hybrid gradient westward with consequences for benthic ecosystem structure