About this Research Topic
Seaweeds are marine macroalgae found throughout the world’s oceans and seas. They can be delicate and small as Desmarestia or strong and large such as in kelp forests. In ecological terms, they are a fundamental part of coastal benthic ecosystems, providing food and refuge to many forms of life and contributing largely to overall photosynthesis. None are known to be poisonous and many are edible and some even considered as great delicacies. Several have industrial applications in cosmetics and food industries, and some can be used as fertilizers. More than 2 billion years of existence has allowed the evolution of close interactions with microorganisms like bacteria, fungi, microalgae and protozoa. Their surfaces are colonized by a diverse epiphytic bacterial community, mainly composed by Bacteroidetes and Proteobacteria (especially Alphaproteobacteria). Bacteria are dominant among the primary colonizers of algae to which contributes the heterogeneous chemical nature of their exudates and the different physical characteristics of substrates. Since the pioneer studies of Provasoli and Pintner in the sixties, the association of some seaweeds and bacteria was understood to be obligatory. Recent molecular developments made it possible to begin to unveil these still largely unexplored complex and highly dynamic communities. In recent years, information regarding the composition of bacterial communities on marine algae has begun to be obtained, as well as on temporal variability and interaction with algal hosts. Bacteria receive good protection and “fixed carbon meals”. Seaweeds receive vitamins, inorganic nutrients like fixed nitrogen, and growth regulators. Bacteria produce molecules like thallusin which is essential for normal ulvacean morphology. A substantial number of bacterial taxa have thus far been isolated from algal sources, however, only very few seaweeds out of the about ten thousand known species (1500 green, 1800 brown and 6500 red) have thus far been analyzed. By applying new technological methodologies and 'omics approaches, a better understanding will be achieved regarding (1) the symbiotic, pathological and opportunistic interactions between seaweeds and bacteria, (2) the biotic and abiotic factors that modulate the interactions within these communities, and (3) the underlying driving forces of temporal and geographical variation. In this Research Topic, we aim to focus on this poorly understood and virtually undescribed microbial world.
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