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We address the question of whether seaweed zonation can be characterized in terms of light absorption, pigmentation, photosynthetic parameters, photoinhibition, and thallus structure. Based on 32 seaweed species from the Pacific coast of southern Chile, intertidal assemblages exhibited higher light requirements for photosynthesis (Ek) and lower thallus light absorptances than subtidal algae. Ek values were lower than the highest measured irradiances at the corresponding natural depths, suggesting that photosynthesis in these organisms could potentially occur at lower depths. During summer, 1% of photosynthetically active radiation (PAR) reached a depth of 23 m, while UVB and UV-A wavelengths were completely attenuated at <3 and 6 m, respectively. Overall, the photobiological adaptations were associated with depth, morphology, and taxonomic group. Photoinhibition was similar in algae from different depths, although recovery was higher in upper littoral algae than in infra- and sublittoral species. The characteristics conferring competitive abilities in light use and light stress tolerance were not, or only partially, related to the classical Littler form-function model. The filamentous and foliose forms were able to acclimate rapidly to changing light and physical stress in the supralittoral zone. For infralittoral kelps living in a highly dynamic environment, higher cross-sectional area and enhanced in vivo light absorption were coupled with morphological features (e.g. massive thallus) that are advantageous in withstanding e.g. water movement. By contrast, the rapid physiological adjustments that allow algae to endure solar stress (e.g. photochemical down-regulation) were strongly dependent on the position on the shore but not on gross morphology.

Molecular biotechnology of marine algae is referred to as the biotechnology on the identification, modification, production and utilization of marine algal molecules. It involves not only the manipulation of macromolecules such as DNA, RNA and proteins, but also deals with low molecular weight compounds such as secondary metabolites.

In the last decade, molecular systematic researches to investigate the relationship and to examine the evolutionary divergence among Chinese marine algae have been carried out by Chinese scientists. For example, RAPD has been widely used in several laboratories to elucidate genetic variations of the reds, such as Porphyra, Gracilaria, Grateloupia and the greens such as VIva and Enteromorpha. Some important data have been obtained. The study on molecular genetic markers for strain improvement is now in progress.

In 1990s, genetic engineering of economic seaweeds such as Laminaria, Vndaria, Porphyra, Gracilaria and Grateloupia has been studied in China. For Laminariajaponica, the successfully cultivated kelp in China, a model transformation system has been set up based on the application of plant genetic techniques and knowledge of the algal life history. Progress has been made recently in incorporating a vaccine gene into kelp genome. Evidence has been provided showing the expression of gene products as detectable vaccines.

In the present paper, the progress of molecular biotechnological studies of marine algae in China, especially researches on elucidating and manipulating nucleic acids of marine algae, are reviewed.

Polysialic acid (polySia) and polySia glycomimetic molecules support nerve cell regeneration, differentiation, and neuronal plasticity. With a combination of biophysical and biochemical methods, as well as data mining and molecular modeling techniques, it is possible to correlate specific ligand–receptor interactions with biochemical processes and in vivo studies that focus on the potential therapeutic impact of polySia, polySia glycomimetics, and sulfated polysaccharides in neuronal diseases. With this strategy, the receptor interactions of polySia and polySia mimetics can be understood on a submolecular level. As the HNK-1 glycan also enhances neuronal functions, we tested whether similar sulfated oligo- and polysaccharides from seaweed could be suitable, in addition to polySia, for finding potential new routes into patient care focusing on an improved cure for various neuronal diseases. The knowledge obtained here on the structural interplay between polySia or sulfated polysaccharides and their receptors can be exploited to develop new drugs and application routes for the treatment of neurological diseases and dysfunctions.

Background: The red macroalgae Asparagopsis taxiformisis a potent natural supplement for reducing methane production from cattle. A. taxiformiscontains several anti-methanogenic compounds including bromoform that inhibits directly methanogenesis. The positive and adverse effects of A. taxiformison the rumen microbiota are dose-dependent and operate in a dynamic fashion. It is therefore key to characterize the dynamic response of the rumen microbial fermentation for identifying optimal conditions on the use of A. taxiformisas a dietary supplement for methane mitigation. Accordingly, the objective of this work was to model the effect of A. taxiformissupplementation on the rumen microbial fermentation under in vitroconditions. We adapted apublished mathematical model of rumen microbial fermentationto account for A. taxiformissupplementation. We modelled the impact of A. taxiformison the fermentationand methane production by two mechanisms, namely (i) direct inhibition of the growth rate of methanogens by bromoform and (ii) hydrogen control on sugars utilization and on the flux allocation towards volatile fatty acids production.We calibrated our model using a multi-experiment estimation approach that integrated experimental datawith six macroalgae supplementation levels from a published in vitrostudy assessing the dose-response impact of A. taxiformison rumen fermentation. Results:our model captured satisfactorily the effect of A. taxiformison the dynamic profile of rumen microbial fermentation for the six supplementation levels of A. taxiformiswith an average determination coefficient of 0.88 and an average coefficient of variation of the root mean squared error of 15.2%for acetate, butyrate, propionate, ammonia and methane. Conclusions:our results indicated the potential of our model as prediction tool for assessing the impact of additives such as seaweeds on the rumen microbial fermentationand methane production in vitro.Additional dynamic data on hydrogen and bromoform are required to validate our model structure and look for model structure improvements. We expect this model development can be useful to help the design of sustainable nutritional strategies promoting healthy rumen function and low environmental footprint.