Asymmetric cell division and its role in cell fate determination in the green alga Tetraselmis indica.

The prasinophytes (early diverging Chlorophyta), consisting of simple unicellular green algae, occupy a critical position at the base of the green algal tree of life, with some of its representatives viewed as the cell form most similar to the first green alga, the ‘ancestral green flagellate’. Relatively large-celled unicellular eukaryotic phytoflagellates (such as Tetraselmis and Scherffelia), traditionally placed in Prasinophyceae but now considered as members of Chlorodendrophyceae (core Chlorophyta), have retained some primitive characteristics of prasinophytes. These organisms share several ultrastructural features with the other core chlorophytes (Trebouxiophyceae, Ulvophyceae and Chlorophyceae). However, the role of Chlorodendrophycean algae as the evolutionary link between cellular individuality and cellular cooperation has been largely unstudied. Here, we show that clonal populations of a unicellular chlorophyte, Tetraselmis indica, consist of morphologically and ultrastructurally variant cells which arise through asymmetric cell division. These cells also differ in their physiological properties. The structural and physiological differences in the clonal cell population correlate to a certain extent with the longevity and function of cells.

Effect of Microalgal Extracts of Tetraselmis suecica against UVB-Induced Photoaging in Human Skin Fibroblasts

Exposure of cells to ultraviolet B (UVB) radiation can induce production of free radicals and reactive oxygen species (ROS), which damage cellular components. In addition, these agents can stimulate the expression of matrix metalloproteinase (MMP) and decrease collagen synthesis in human skin cells. In this study, we examined the anti-photoaging effects of extracts of Tetraselmis suecica (W-TS). W-TS showed the strongest scavenging activity against 2,2-difenyl-1-picrylhydrazyl (DPPH) and peroxyl radicals, followed by superoxide anions from the xanthine/xanthine oxidase system. We observed that the levels of both intracellular ROS and lipid peroxidation significantly increased in UVB-irradiated human skin fibroblast cells. Furthermore, the activities of enzymatic antioxidants (e.g., superoxide dismutase) and the levels of non-enzymatic antioxidants (e.g., glutathione) significantly decreased in cells. However, W-TS pretreatment, at the maximum tested concentration, significantly decreased intracellular ROS and malondialdehyde (MDA) levels, and increased superoxide dismutase and glutathione levels in the cells. At this same concentration, W-TS did not show cytotoxicity. Type 1 procollagen and MMP-1 released were quantified using RT-PCR techniques. The results showed that W-TS protected type 1 procollagen against UVB-induced depletion in fibroblast cells in a dose-dependent manner via inhibition of UVB-induced MMP-1. Taken together, the results of the study suggest that W-TS effectively inhibits UVB-induced photoaging in skin fibroblasts by its strong anti-oxidant ability.

Chemical compositon of three microalgae species for possible use in mariculture

The purpose of this study was to determine the chemical composition of Chaetoceros gracilis, Cylindrotheca closterium and Tetraselmis gracilis, species frequently used as food for aquaculture in the northeast of Brazil. The species were grown in f/2 medium, in carboys, aerated from one liter, with constant illumination and analyses were made in late exponential growth phase. Cellular density (8,447 x 10 6 cell.L-1), soluble carbohydrates (0.10±0.01 mg.L-1) and magnesium (14.78±0.08 mg.L-1) were the highest in C. gracilis. C . closterium had the highest amount of chlorophyll a (13.76±1.11 mg.L-1), soluble proteins (0.62±0.04 mg.L-1), total amino acids (23.82±0.84 mg .L-1), nitrate (0.36±0.02 mg.L-1), sodium (0.46±0.05 mg.L-1) and phosphorus (2.80±0.38 mg.L-1). Both the species had potassium levels of 0.02 mg.L-1 and sulfur levels of 0.03 mg.L-1. T. gracilis had the lowest values in almost all the analyzed variables, except for chlorophyll a. Therefore, among the analyzed species and tested conditions, C. closterium represented the best nutritional option for aquaculture projects.

Este trabalho objetivou a determinação da composição química de Chaetoceros gracilis, Cylindrotheca closterium e Tetraselmis gracilis, espécies de freqüente uso na aqüicultura no Nordeste do Brasil. As espécies foram cultivadas em meio f/2-Guillard, em garrafão de vidro, aeradas a partir de um litro, com iluminação constante e as análises foram realizadas no final da fase exponencial. C. gracilis apresentou maior densidade celular, chegando a 8.442x10(6) cel.L-1, o maior valor para carboidratos solúveis (0,10 ± 0,01 mg.L-1) e magnésio (14,78 ± 0,08 mg.L-1). C. closterium apresentou a maior concentração para clorofila a (13,76 ± 1,11 mg.L-1), proteína solúvel (0,62 ± 0,04 mg.L-1), aminoácidos totais livres (23,82 ± 0,84 mg.L-1), nitrato (0,36 ± 0,02 mg.L-1), sódio (0,46 ± 0,05 mg.L-1) e fósforo (2,80 ± 0,38 mg.L-1). Os teores de potássio (0,02 mg.L-1) e enxofre (0,03 mg.L-1) foram iguais para C. gracilis e C. closterium. A espécie T. gracilis apresentou os menores valores nas variáveis analisadas, exceto para clorofila a. Apresentando-se, portanto, entre as três espécies analisadas, C. closterium como a melhor opção nutricional, dentre as condições observadas, para projetos em aqüicultura.