A non‐colony‐forming axenic strain of Phaeocystis globosa (Harlot) Lagerheim was shown to produce a water‐soluble β‐d‐glucan. This glucan consisted of about 20 glucose units, mainly (l→3)‐linked, with branching at position 6. Therefore, it can be classified as a chrysolaminaran. Glucan production occurred mainly during the stationary growth phase and resulted in concentrations as high as 76 pg glucose per cell. When cultures were deprived of light the glucans were consumed, which supports their possible role as compounds used for temporary storage of energy.
A possible coupling between UV radiation (UVR; 280 to 400 nm) induced stress and the production of dimethylsulfoniopropionate (DMSP), the precursor of the climate-regulating gas dimethylsulfide (DMS), was investigated in the marine prymnesiophyte Emiliania huxleyi. To this end, axenic cultures of E. huxleyi were exposed to a range of UVR doses for 2 consecutive days. During and after these treatments, growth, photosynthetic activity, cell size, DNA damage, sugar accumulation and DMSP concentrations were followed. The vulnerability of E. huxleyi for relatively low UVR doses was demonstrated by the inhibition of growth and the simultaneous occurrence of DNA damage. Also, mean cell size increased and sugars accumulated as a result of the UVR treatments. In contrast, no effect was observed on the optimal quantum yield of Photosystem II (PSII), a measure of the efficiency of photosynthesis. With increasing UVR dose, cellular DMSP content increased. However, the intracellular DMSP concentrations remained constant at the level typical for the applied temperature and salinity conditions, due to accompanying increase in cell size. The increased cellular DMSP content did not compensate, therefore, for the decreased growth rates, resulting in an overall decrease in the total amount of DMSP produced in the cultures. The UVR effects as induced in this study are assumed to be severe as compared with natural solar conditions, especially because high in situ UVAR (315 to 400 nm) may ameliorate UVBR damage by activation of photorepair. Yet the presented results imply that when (increased) UV(B)R causes growth rate reduction of E. huxleyi in situ, DMSP fluxes are likely to be reduced too.KEY WORDS: UV radiation · Phytoplankton · Emiliania huxleyi · Cyclobutane pyrimidine dimers · DNA · Thymine dimers · Dimethylsulfide · Dimethylsulfoniopropionate · Salinity · F v /F m Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 28: [167][168][169][170][171][172][173][174] 2002 amino acids. In addition, Stefels (2000) postulated that DMSP could be used as an overflow of carbon when carbohydrate production exceeds cellular carbon requirements. Additions of methionine to Tetraselmis subcordiformis and Wollastonia biflora resulted in an increased DMSP production (Gröne & Kirst 1992, Hanson et al. 1994.It is indisputable that solar UV radiation (UVR; 280 to 400 nm) negatively affects marine microalgae, judging from the many field experiments that have demonstrated UVBR-related decreases in primary production (Smith et al. 1992, Helbling et al. 1994, Neale et al. 1994, 1998, Boucher & Prezelin 1996, McMinn et al. 1999. Inside the cell, UVBR can affect Photosystem II (PSII) efficiency (Kroon et al. 1994, Schofield et al. 1995 or the ribulose 1, 5-bisphosphate carboxylase/oxygenase (RUBISCO) pool (Lesser et al. 1996). In addition, UVBR induces DNA damage, notably cyclobutane pyrimidine dimers (CPDs) (Karentz et al. 1991, Karentz 1994, Buma et al. 1996 that may arrest the cell cycle in the ...
Acrylate produced from dimethylsulphoniopropionate (DMSP) by Phaeocystls has been claimed to inhib~t bactenal growth However, the concentrations of acrylate measured In seawater dunng Phaeocystls blooms are not high enough to expect i n h~b i t~o n of bactenal growth In this study, the total acrylate m Phaeocyshs cultures free from bacteria was measured The concentration found m the exponenbal phase of growth was similar (0 1 to 1 0 PM) to earher field reports, but the amount found in the stationary phase of growth was much higher (1 to 4 pM) Acrylate in cultures, as well as in field samples, was found to be located in the mucous layer of the colony 'Microscale' concentrations in that layer were more than 1000-fold higher (1 3 to 6 5 mlvl) than the total concentration found in the unfractionated culture Such h~g h concentrations could have a n antimicrobial effect However, acrylate appears to be adsorbed to the mucus and may be inaccessible to bactena including those that consume acrylate As soon as the colonies started to decay, acrylate was released ~n t o the surrounding envlronment, and since it is not detected In bloom samples, ~t is apparently consumed by bactena
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.