An inventory of factors that affect polysaccharide production by Phaeocystis globosa

Kong

Ann. Limnol. - Int. J. Lim.

et al. 2009

-Colonial Microcystis aeruginosa were obtained when the unicellular algae were exposed to flagellate Ochromonas sp. filtrate. To investigate the benefit of this morphological change, flagellates were added into cultures of unicellular and colonial M. aeruginosa, respectively. The clearance rates of flagellates on algae were markedly decreased when they were cultivated with induced colonial M. aeruginosa. This result indicated that colony formation in M. aeruginosa was a predator-induced defense, which could reduce predation risk from flagellate. The increased content of soluble extracellular polysaccharide (sEPS) and bound extracellular polysaccharide (bEPS) may play an important role in adhering M. aeruginosa cells together to form colonies. The decrease of WPS II and the increase of sinking rates of induced colonial M. aeruginosa showed that the costs of grazed-induced colony formation in M. aeruginosa may reflect in the photosystem II efficiency, and in the sinking rates.

Section: Discussionsupporting

confidence: 49%

Benefits and costs of the grazer-induced colony formation inMicrocystis aeruginosa

Kong

Ann. Limnol. - Int. J. Lim.

et al. 2009

“…No data are available for other species of Phaeocystis, including P. antarctica. In five different strains of P. globosa differences in the ratio of non-glucose constituents were small (Van Rijssel et al 2000). Nutrient status of the cells does not seem to influence the ratio, as was shown in a batch culture of P. globosa (Van Rijssel et al 2000) or in bloom samples taken at different stages of a bloom (Janse et al 1996a).…”

Section: Mucopolysaccharidesmentioning

confidence: 81%

“…Energy and carbon produced during overflow metabolism in Phaeocystis can be channeled towards both glucan and mucopolysaccharides. During the stationary phase of a P. pouchetii bloom in mesocosms the ratio glucan/mucopolysaccharides increased (Alderkamp et al 2006a), whereas it decreased during the stationary phase of cultures of colonial P. globosa (Van Rijssel et al 2000).…”

Section: Storage Glucanmentioning

confidence: 94%

“…Laminarin from the brown seaweed Laminaria digitata was digested to monosaccharides by this enzyme preparation. In colony-forming strains of P. globosa, however, no more than 40-70% of glucose polymers were digested (Van Rijssel et al 2000;Alderkamp et al 2006a). The reason for this partial digestion may be differences in the type of chrysolaminaran produced by single cells and colonial cells, e.g., with respect to polymer size or number of branches.…”

Section: Storage Glucanmentioning

confidence: 99%

“…Carbohydrate accumulation has been observed during the stationary growth phase of a single cell culture (Janse et al 1996b), colonial cultures (Van Rijssel et al 2000), and a bloom of P. globosa (Veldhuis et al 1986a), and at the end of P. pouchetii blooms in mesocosms (Alderkamp et al 2006a). This so-called overflow metabolism under nutrient limitation is common in phytoplankton (Myklestad 1974(Myklestad , 1988.…”

Section: Storage Glucanmentioning

confidence: 99%

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The carbohydrates of Phaeocystis and their degradation in the microbial food web

2007

The ubiquity and high productivity associated with blooms of colonial Phaeocystis makes it an important contributor to the global carbon cycle. During blooms organic matter that is rich in carbohydrates is produced. We distinguish five different pools of carbohydrates produced by Phaeocystis. Like all plants and algal cells, both solitary and colonial cells produce (1) structural carbohydrates, (hetero) polysaccharides that are mainly part of the cell wall, (2) mono-and oligosaccharides, which are present as intermediates in the synthesis and catabolism of cell components, and (3) intracellular storage glucan. Colonial cells of Phaeocystis excrete (4) mucopolysaccharides, heteropolysaccharides that are the main constituent of the mucous colony matrix and (5) dissolved organic matter (DOM) rich in carbohydrates, which is mainly excreted by colonial cells. In this review the characteristics of these pools are discussed and quantitative data are summarized. During the exponential growth phase, the ratio of carbohydrate-carbon (C) to particulate organic carbon (POC) is approximately 0.1. When nutrients are limited, Phaeocystis blooms reach a stationary growth phase, during which excess energy is stored as carbohydrates. This so-called overflow metabolism increases the ratio of carbohydrate-C to POC to 0.4-0.6 during the stationary phase, leading to an increase in the C/N and C/P ratios of Phaeocystis organic matter. Overflow metabolism can be channeled towards both glucan and mucopolysaccharides. Summarizing the available data reveals that during the stationary phase of a bloom glucan contributes 0-51% to POC, whereas mucopolysaccharides contribute 5-60%. At the end of a bloom, lysis of Phaeocystis cells and deterioration of colonies leads to a massive release of DOM rich in glucan and mucopolysaccharides. Laboratory studies have revealed that this organic matter is potentially readily degradable by heterotrophic bacteria. However, observations in the field of accumulation of DOM and foam indicate that microbial degradation is hampered. The high C/N and C/P ratios of Phaeocystis organic matter may lead to nutrient limitation of microbial degradation, thereby prolonging degradation times. Over time polysaccharides tend to self-assemble into hydrogels. This may have a profound effect on carbon cycling, since hydrogels provide a vehicle to move DOM up the size spectrum to sizes subject to sedimentation. In

Effects of Daphnia ‐Associated Infochemicals on the Morphology, Polysaccharides Content and PSII‐Efficiency in Scenedesmus obliquus

International Review of Hydrobiology

Kong

Shi

et al. 2007

We investigated the effects of infochemicals from Daphnia carinata on the morphology, polysaccharides yield and PSII-efficiency in Scenedesmus obliquus. Infochemicals released from D. carinata induced colony formation in S. obliquus. The contents of soluble extracellular polysaccharides, bounded extracellular polysaccharides, and the total polysaccharides per cell in the induced colonies of S. obliquus increased significantly relative to those of the unicells, which indicated that Daphnia-associated infochemicals could also stimulate S. obliquus to increase the synthesis of extracellular polysaccharides. The increased extracellular polysaccharides may play an important role in cementing S. obliquus cells together to form colonies. In addition, no significant differences in growth, the maximal efficiency of PSII photochemistry (F v /F m ), and the effective quantum yields of PSII (Φ PSII ) were detected between unicellular and induced colonial populations, which showed that the cost of induced colony formation was not reflected on these indices.