Direct visualization of mucus production by the cold-water coral <i>Lophelia pertusa</i> with digital holographic microscopy

<i>Lophelia pertusa</i> is the dominant reef-building organism of cold-water coral reefs, and is known to produce significant amounts of mucus, which could involve an important metabolic cost. Mucus is involved in particle removal and feeding processes, yet the triggers and dynamics of mucus production are currently still poorly described because the existing tools to study these processes are not appropriate. Using a novel microscopic technique—digital holographic microscopy (DHM)–we studied the mucus release of <i>L</i>. <i>pertusa</i> under various experimental conditions. DHM technology permits µm-scale observations and allows the visualization of transparent mucoid substances in real time without staining. Fragments of <i>L</i>. <i>pertusa</i> were first maintained in flow-through chambers without stressors and imaged with DHM, then exposed to various stressors (suspended particles, particulate food and air exposure) and re-imaged. Under non-stressed conditions no release of mucus was observed, whilst mucus strings and sheaths were produced in response to suspended particles (activated charcoal and drill cuttings sediment) i.e. in a stressed condition. Mucus strings and so-called ‘string balls’ were also observed in response to exposure to particulate food (brine shrimp <i>Artemia salina</i>). Upon air-exposure, mucus production was clearly visible once the fragments were returned to the flow chamber. Distinct optical properties such as optical path length difference (OPD) were measured with DHM in response to the various stimuli suggesting that different mucus types are produced by <i>L</i>. <i>pertusa</i>. Mucus produced to reject particles is similar in refractive index to the surrounding seawater, suggesting that the energy content of this mucus is low. In contrast, mucus produced in response to either food particle addition or air exposure had a higher refractive index, suggesting a higher metabolic investment in the production of these mucoid substances. This paper shows for the first time the potential of DHM technology for the detection, characterization and quantification of mucus production through OPD measurements in <i>L</i>. <i>pertusa</i>

Relating biomarkers to whole-organism effects using species sensitivity distributions : A pilot study for marine species exposed to oil

Biomarkers are widely used to measure environmental impacts on marine species. For many biomarkers, it is not clear how the signal levels relate to effects on the whole organism. This paper shows how species sensitivity distributions (SSDs) can be applied to evaluate multiple biomarker responses in species assemblages. To our knowledge, the present study compared for the first time SSDs based on biomarker response levels for marine species to a SSD for whole-organism responses. The comparison indicates that for exposure to dispersed oil in the marine environment, the selected biomarkers were, on average, 35- to 50-fold more sensitive than the whole-organism effect. At the 5% hazardous concentration derived from the SSD for whole-organism effects, which is a conservative threshold level, the potentially affected fraction of species showing biomarker response corresponds to approximately 80%. Variation in species sensitivity, expressed either as biomarker or as whole-organism response levels, were similar. Although uncertainties exist, the link between biomarkers and risk assessment presented here provides a preliminary guideline for deciding when biomarker responses likely are hazardous and, therefore, require further investigation. © 2009 SETAC

OmpA targets dendritic cells, induces their maturation and delivers antigen into the MHC class I presentation pathway

We analyzed the interaction between a bacterial cell wall protein and dendritic cells (DCs). Outer membrane protein A from Klebsiella pneumoniae (kpOmpA) specifically bound to professional antigen presenting cells and was endocytosed by immature DCs via a receptor-dependent mechanism. kpOmpA signaled through Toll-like receptor 2, induced DCs to produce interleukin 12 and induced maturation of DCs. Whole antigen that was coupled to kpOmpA and injected into mice was taken up by DCs and delivered to the conventional cytosolic MHC class I presentation pathway. kpOmpA also primed antigen-specific CD8+ CTLs in the absence of CD4+ T cell help or adjuvant and elicited therapeutic immunity to antigen-expressing tumors. Thus, OmpA belongs to a class of proteins that are able to elicit CTL responses to exogenous antigen