Increased Local Retention of Reef Coral Larvae as a Result of Ocean Warming

Climate change will alter many aspects of the ecology of organisms, including dispersal patterns and population connectivity. Understanding these changes is essential to predict future species distributions, estimate potential for adaptation, and design effective networks of protected areas. In marine environments, dispersal is often accomplished by larvae. At higher temperatures, larvae develop faster, but suffer higher mortality, making the effect of temperature on dispersal difficult to predict. Here, we experimentally calibrate the effect of temperature on larval survival and settlement in a dynamic model of coral dispersal. Our findings imply that most reefs globally will experience several-fold increases in local retention of larvae due to ocean warming. This increase will be particularly pronounced for reefs with mean water residence times comparable to the time required for species to become competent to settle. Higher local retention rates strengthen the link between abundance and recruitment at the reef scale, suggesting that populations will be more responsive to local conservation actions. Higher rates of local retention and mortality will weaken connectivity between populations, and thus potentially retard recovery following severe disturbances that substantially deplete local populations. Conversely, on isolated reefs that are dependent on replenishment from local broodstock, increases in local retention may hasten recovery

Genetically Engineered Alginate Lyase-PEG Conjugates Exhibit Enhanced Catalytic Function and Reduced Immunoreactivity

Alginate lyase enzymes represent prospective biotherapeutic agents for treating bacterial infections, particularly in the cystic fibrosis airway. To effectively deimmunize one therapeutic candidate while maintaining high level catalytic proficiency, a combined genetic engineering-PEGylation strategy was implemented. Rationally designed, site-specific PEGylation variants were constructed by orthogonal maleimide-thiol coupling chemistry. In contrast to random PEGylation of the enzyme by NHS-ester mediated chemistry, controlled mono-PEGylation of A1-III alginate lyase produced a conjugate that maintained wild type levels of activity towards a model substrate. Significantly, the PEGylated variant exhibited enhanced solution phase kinetics with bacterial alginate, the ultimate therapeutic target. The immunoreactivity of the PEGylated enzyme was compared to a wild type control using in vitro binding studies with both enzyme-specific antibodies, from immunized New Zealand white rabbits, and a single chain antibody library, derived from a human volunteer. In both cases, the PEGylated enzyme was found to be substantially less immunoreactive. Underscoring the enzyme's potential for practical utility, >90% of adherent, mucoid, Pseudomonas aeruginosa biofilms were removed from abiotic surfaces following a one hour treatment with the PEGylated variant, whereas the wild type enzyme removed only 75% of biofilms in parallel studies. In aggregate, these results demonstrate that site-specific mono-PEGylation of genetically engineered A1-III alginate lyase yielded an enzyme with enhanced performance relative to therapeutically relevant metrics.Cystic Fibrosis Foundation (Research Development Program)National Center for Research Resources (U.S.) (P20RR018787-06

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

Phenotypic Plasticity and Adaptation Potential to Salinity in Early Life Stages of the Tunicate, Ciona intestinalis spB

Species respond to environmental heterogeneity through a variety of mechanisms such as plasticity, genetic adaptation and phenotypic buffering. Determining how gene flow, scale of environmental heterogeneity and trait heritability influence these responses is important for understanding how these different mechanisms arise, which is a central task in the field of evolutionary biology. For many marine organisms salinity is an important driver of environmental heterogeneity and physiological stress. As with many stressors, salinity stress is often more severe for early life-history stages such as embryos and larvae. The main aim of this thesis was to investigate underlying mechanisms that allow species to cope with environmental heterogeneities in their natural environment. More specifically, I focused on strategies to manage salinity differences in early life-history stages of the tunicate Ciona intestinalis. This marine invertebrate has a large geographical distribution and is considered highly invasive in some parts of the world. Plasticity in important fitness related traits is generally considered to promote invasiveness even though there is evidence that local adaptation also could play an important role in range expansions of invasive species. Through investigations of population differences in larval performance, I wanted to understand what mechanisms allowed existing populations to inhabit different salinity regimes, focusing explicitly on the role of transgenerational phenotypic plasticity. Adult acclimation had a predominant effect on tolerance ranges of developing embryos and larvae, but there were also small signs of population differences that could be related to local adaptation and/or persistent environmental effects. To better understand the potential for adaptation of larval salinity tolerance I used quantitative genetic methods to assess the extent to which larval performance in different salinities is a heritable trait. Heritable variation proved to be extremely low, suggesting limited potential for local adaption in investigated populations. The potential for local adaptation can be strongly influenced by gene flow between populations that inhabit different environments. C. intestinalis has pelagic larvae, which could disperse over relatively large areas, thereby preventing local genetic differentiation. Through a population genetic study we found that gene flow at times was restricted at much smaller scales than suggested by the dispersal potential of larvae. Population structures implied that physical barriers, such as density differences between water masses, restricted larval dispersal. The study of sexual selection is an important field in evolutionary biology. Traditionally, it was assumed that sexual selection could not operate in sessile marine invertebrates with external fertilization. Today, however, there are many examples of mechanisms governing gamete interactions that allow eggs to "select" sperm. Our understanding of the underlying selective pressures, and indeed how these mechanisms affect fertilization success between individuals within a species, is however limited. I examined causes of variation in fertilization success in populations of C. intestinalis. I found significant variability in compatibility between parental genotypes, which indicated that this may be a way for individuals to avoid the negative effects of inbreeding

Distribution coefficients of dietary sugars in artificial Candida biofilms

Candida species are the most important fungal pathogens in humans and cause a variety of superficial and systemic diseases. Biofilm formation is a major virulence attribute contributing to Candida pathogenicity. Although the concentration and distribution of nutrients as well as antifungals across the biofilm thickness play a pivotal role in the development and persistence of Candida biofilms, only limited information is available on the latter aspects of Candida biofilms. Therefore, we attempted to characterize the diffusion coefficient (De) of common dietary sugars such as glucose, galactose, and sucrose in Candida albicans biofilms using horizontal attenuated total reflection-Fourier transform infrared spectroscopy (HATR-FTIR). Artificial Candida biofilms were formed using agarose polymers. De of three sugars tested, glucose, galactose, and sucrose in this artificial Candida biofilm model was found to be 4.08E-06 ± 3.63E-08, 4.08E-06 ± 3.70E-08, and 5.38E-06 ± 4.52E-08 cm2 s-1, respectively. We demonstrate here the utility of HATR-FTIR for the determination of diffusion of solutes such as dietary sugars across Candida biofilms