CARBOHYDRATE RELEASE BY A SUBTROPICAL STRAIN OF SPONDYLOSIUM PYGMAEUM (ZYGNEMATOPHYCEAE): INFLUENCE OF NITRATE AVAILABILITY AND CULTURE AGING1

Authors

  • Fernanda Reinhardt Piedras,

    1. Pós-graduação em Oceanografia Biológica, Instituto de Oceanografia, Universidade Federal de Rio Grande- FURG, Av. Italia, Km 8, Rio Grande, RS 96201-900, Brasil
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  • Paulo Roberto Martins Baisch,

    1. Laboratório de Oceanografia Geológica Instituto de Oceanografia, Universidade Federal de Rio Grande- FURG, Av. Italia, Km 8, Rio Grande, RS 96201-900, Brasil
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  • Maria Isabel Corrêa Da Silva Machado,

    1. Laboratório de Oceanografia Geológica Instituto de Oceanografia, Universidade Federal de Rio Grande- FURG, Av. Italia, Km 8, Rio Grande, RS 96201-900, Brasil
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  • Armando Augusto Henriques Vieira,

    1. Departamento de Botanica, Unversidade Federal de Sao Carlos, Via Washington Luis, Km 235, Sao Carlos, SP 13565-905, Brasil
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  • Danilo Giroldo

    1. Laboratório de Botânica Criptogâmica, Instituto de Ciências Biológicas, Universidade Federal de Rio Grande – FURG, Av. Italia, Km 8, Rio Grande, RS 96201-900, Brasil
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  • 1

    Received 25 June 2009. Accepted 18 November 2009.

Abstract

This paper describes the influence of nitrate availability on growth and release of dissolved free and combined carbohydrates (DFCHOs and DCCHOs) produced by Spondylosium pygmaeum (Cooke) W. West (Zygnematophyceae). This strain was isolated from a subtropical shallow pond, located at the extreme south of Brazil (Rio Grande, RS). Experiments were carried out in batch culture, comparing two initial nitrate levels (10/100 μM) in the medium. Growth was monitored by direct microscopic cell counts and chl a content. Nitrate consumption was determined by ion chromatography, while the production of extracellular carbohydrates was monitored by the phenol-sulfuric method. The monosaccharide compositions of DFCHOs and DCCHOs were determined in each growth phase by HPLC with pulse amperometric detection (HPLC-PAD). At the end of the experiment, the total composition of extracellular polysaccharide (EPS) molecules >12 kDa was determined by gas chromatography. Nitrate availability had no influence on S. pygmaeum cell density at any phase. On the other hand, chl a content decreased after a few days growth when the availability of nitrate was restricted, but continued to rise when nitrate was plentiful. Also, nitrate depletion was faster at 10 μM nitrate. No influence of the growth phase or nitrate availability on the total carbohydrates (TDCHOs) released per cell was observed. Only DCCHOs were released by S. pygmaeum, and the composition varied between growth phases, especially at lower nitrate availability. EPS molecules >12 kDa were composed mainly of xylose, fucose, and galactose, as for other desmids. However, a high N-acetyl-glucosamine content was found, uniquely among desmid EPSs.

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