In mid-May 2008 a serious green tide caused mainly by floating Ulva prolifera(Mller) J.Agardh(Chlorophyta,Ulvales) thalli struck the coastal area of Qingdao,China.To understand the present physiological conditions of the floating alga,in this work both laboratory and field investigations were conducted on the floating U.prolifera thalli in comparison with the attached U.prolifera thalli collected from the area.The floating thalli of three distinctively different colors and attached thalli at three different stages of sporangium formation process were characterized under a microscope,while their photosynthetic parameters were determined with chlorophyll fluorescence technology.On the other hand,the sporangium formation status of the floating U.prolifera thalli was surveyed both in the laboratory and in the field.Comparisons showed that both of the paired morphological characteristics and the paired physiological parameters of the floating and attached U.prolifera thalli were consistent.Furthermore,some spores were confirmed in the field and some motile particles were found within the floating thalli.These results suggest that the floating U.prolifera thalli with different colors could be at different stages of sporangium formation.However,our results also showed that the floating alga thalli have only a limited reproductive potential.This might limit the duration and the further geographic expansion of the green algal bloom.
Apeng LinSongdong ShenGuangce WangQianqian YiHongjin QiaoJianfeng NiuGuanghua Pan
Using shotgun sequencing data, the complete sequences of chloroplast 16S rRNA and tufA genes were acquired from native specimens of Bryopsis hypnoides (Qingdao, China). There are two group I introns in the 16S rRNA gene, which is structurally similar to that of Caulerpa sertularioides (Bryopsidales, Chlorophyta). The chloroplast-encoded tufA gene sequence is 1 230 bp long, very AT-rich (61.5%), and is similar to previously published 16S rRNA sequences of bryopsidinean algae. Phylogenetic analyses based on chloroplast 16S rRNA and tufA gene sequence data support previous hypotheses that the Bryopsidineae, Halimedineae, and Ostreobidineae are three distinct lineages. These results also confirmed the exclusion of Avrainvillea from the family Udoteaceae. Phylogenetic analyses inferred that the genus Bryopsis as sister to Derbesia; however, this clade lacked robust nodal support. Moreover, the phylogenetic tree inferred from rbcL GenBank sequences, combined with the geographical distributions of Bryopsis species, identified a strongly supportive clade for three differently distributed Asian Bryopsis species. The preliminary results suggesting that these organisms are of distinct regional endemism.
Bryopsis hypnoides Lamouroux is a unique intertidal siphonous green alga whose extruded protoplasm can aggregate spontaneously in seawater to form numerous new cells that can develop into mature algal thalli.In this study,the photosynthetic responses during dehydration of both the thalli and protoplasts isolated from B.hypnoides were measured using a Dual-PAM(pulse amplitude modulation)-100 fluorometer.The results show that the photosynthetic rates of B.hypnoides thalli were maintained for an initial period,beyond which continued desiccation resulted in reduced rates of PSI and PSII.However,the photosynthetic performances of the isolated protoplasts dehydrated in air(CO2 concentration 600±700 mg/L) showed a slight increase of Y(II) at 20% water loss,but the rates decreased thereafter with declining water content.When protoplasts were dehydrated in CO2 deficient conditions(CO2 concentration 40±80 mg/L),the values of Y(II) declined steadily with increased dehydration without an initial rise.These results indicated that the thalli and isolated protoplasts of this alga can utilize CO2 in ambient air effectively,and the photosynthetic performances of the isolated protoplasts were significantly different from that of the thalli during dehydration.Thus the protoplasts may be an excellent system for the study of stress tolerance.
The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate (PHB) production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation (8.10±0.09 g/L) and PHB production (1.11±0.13 g/L and 14.62%±2.25% of the cell dry weight) were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH 4 + -N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration (7.65±0.05 g/L) was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB (5.03±0.18 g/L and 66.93%±1.69% of the cell dry weight) was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation (8.77±0.58 g/L) and PHB production (6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight) was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.
