Iron is an essential limiting factor for primary production in many marine systems. The present study investigated differential regulation of protein expression in marine phytoplankton Prymnesium parvum under low Fe concentration. The phytoplankton was grown in f/2 culture medium in artificial seawater with low (0.0025 μM) and high (0.05 μM) Fe concentrations. Two-dimensional differential gel electrophoresis and matrix-assisted laser desorption-ionization-time of flight-mass spectrometer analysis were performed for protein identification and characterization. The growth of the alga declined substantially under the low Fe compared to the high Fe concentration. Under low Fe conditions, P. parvum upregulated 10 proteins including chloroplastic ATP synthase subunit b, D2 protein of PSII, D1 protein of PSII reaction centre, and light harvesting complex II protein, most of which are associated with photosynthetic activities in PSII. The results suggest that the marine alga P. parvum altered the biosynthesis of several photosynthetic proteins in order to cope with low Fe conditions., M. M. Rahman, M. A. Rahman, T. Maki, T. Nishiuchi, T. Asano, H. Hasegawa., and Obsahuje bibliografii
This study investigated the effect of solar ultraviolet radiation (UVR) and temperature on a chain length and photosynthetic performance of diatom Chaetorceros curvisetus. The cells were cultured in large quartz tubes and exposed to PAR, PAR + UV-A (PA), or PAR + UV-A + UV-B (PAB) radiation at 20°C and 28°C for six days, respectively. After recovery for 1 h, the cells were exposed again to three different radiations for 1 h. Then, a change in the photochemical efficiency (FPSII) was examined and UVR-induced photoinhibition was calculated. The percentage of long chains (more than five single cells per chain) in C. curvisetus significantly increased from 8.2% (PAR) to 38.9% (PAB) at 20°C; while it was not notably affected at 28°C. Mycosporine-like amino acids (MAAs) concentration obviously increased by irradiance increment from PAR to PAB at 20°C. Chlorophyll (Chl) a concentration significantly declined with increasing irradiance at 20°C. Both MAAs and Chl a concentrations were not obviously changed by irradiance at 28°C. Before and after reexposure, FPSII was significantly reduced both at 20°C and 28°C. UVR-induced photoinhibition at 20°C (39%) was higher than that at 28°C (30.9%). Solar UV radiation, especially UV-B, could significantly influence the percentage of long chains of C. curvisetus, especially at low temperature. UVR-induced photoinhibition can be alleviated by higher temperatures., W. Guan, X. Peng, S. Lu., and Obsahuje seznam literatury
The recognition of aquatic organisms plays a crucial role in the monitoring of the pollution and for the adoption of rapid preventive actions. A compact microscopic optical imaging system is proposed in order to acquire and treat the multibands fluorescence of several pigments in phytoplankton organisms. Two algorithms for automatic recognition of phytoplankton were proposed with a minimum number of calibration parameters. The first algorithm provides a morphological recognition based on "watershed" segmentation and Fourier descriptors, while the second one builds fluorescence pigment images by "k-means" partition of intensity ratios. The operation of these algorithms was illustrated by the study of two different organisms: a cyanobacteria (Dolichospermum sp.) and an alga (Cladophora sp.). The family and the genus of these organisms were then classified into a database which is independent of the size, the orientation and the position of the specimens in the images., M. Lauffer, F. Genty, S. Margueron, J. L. Collette., and Obsahuje bibliografii
We investigated photoacclimation of Dunaliella tertiolecta (Butcher) in irradiance (I) regimes simulating mixed layer conditions of turbid estuarine waters or lakes. D. tertiolecta was exposed to a range of fixed I regimes to establish baseline physiology-I relationships that were compared with subsequent photoacclimation to a simulated mixed layer. Measured indices of photoacclimation included cellular pigmentation, chlorophyll variable fluorescence, and effective photosystem 2 antenna size. While D. tertiolecta grown under fluctuating I maintained division rates comparable to cells grown at high I, the cells exhibited characteristics of photoacclimation consistent with cells grown under a stable regimes at irradiances considerably lower than the average I of the simulated mixed layer. and H. Havelková-Doušová, O. Prášil, M. J. Behrenfeld.