In this study,the responses of Porphyridium sp.cells with salt-elevated bound polysaccharide to t... more In this study,the responses of Porphyridium sp.cells with salt-elevated bound polysaccharide to the stress of high proton flux density (HPFD) or chilling temperature (4 ℃) was studied in order to evaluate possible biological roles of the induced polysaccharides under environmental stresses. Addition of 0.05% polysaccharides to the Porphyridium sp.culture caused the photosynthetic activity decreased under HPFD but increased under chilling temperature (4 ℃) compared to control (culture without external addition of polysaccharide). The PSⅡ efficiency (Fv/Fm) decline was not significantly affected with the exogenous polysaccharide. Within 48 h after removal of salt from the cultures,both photosynthetic activity of the salt pre-treated cells measured under HPFD and chilling temperature (4 ℃) and bound polysaccharide content returned to the levels of un-treated cells. However,the PSⅡ efficiency of the recovery cultures measured under HPFD still kept at a higher level,especially after 6 hours,compared with control and salt treated cultures,suggesting that the high polysaccharide content induced by the salt stress may enhance PSⅡ tolerance to high photon flux density.
Algal physiology and biochemistry have been reviewed and discussed quite extensively in the last ... more Algal physiology and biochemistry have been reviewed and discussed quite extensively in the last decades. The excellent contributions by Lewin (1962), Fogg (1975) and Carr and Whitton (1973) are just a few examples of textbooks which cover a wide range of topics related to algal physiology and biochemistry. The aim of this chapter is to point out relevant areas in which Spirulina has been used as a model organism or studies whose data can be of significant importance in further understanding the growth, physiology and biochemistry of Spirulina, especially when grown in outdoor conditions.
Abstract: Light is one of the most important factors affecting photosynthesis and growth of micro... more Abstract: Light is one of the most important factors affecting photosynthesis and growth of microalgal cultures. Photosynthetic responses to light change with the stage of the culture; however, little is known about how changes in the photosynthetic capacity with the duration of batch culture affect growth at the end (final harvest day) of the culture. Accordingly, we studied the photosynthetic performance and growth of Nannochloropsis oculata in the exponential phase (day 4), the linear phase of growth (day 8) and stationary phase (day 15) of batch cultures grown under a range of light intensities from 20 to 200 μmol photons m−2 s−1. Nannochloropsis oculata showed a high ability to acclimate to changing light conditions; cells almost doubled their cellular Chl a concentration under low light conditions and increased their photosynthetic oxygen evolution capacity, which allowed this alga to maintain a stable photosynthetic efficiency in the three stages of the culture studied. Changes in the Chl a per cell under different light conditions were not paralleled by changes in antenna size, which suggests that N. oculata uses an alternative strategy to acclimate to changing light levels. Finally, increasing photosynthetic capacity in cells growing under 20 μmol photons m−2 s−1 did not avoid light limitation and decreasing exponential growth rate. However, the lack of differences in final cell density achieved between 20 and 200 μmol photons m−2 s−1 treatments suggests that bicarbonate limitation started to affect photosynthesis and growth at the higher light treatments, from the linear phase of growth onwards. Understanding of the photosynthetic and growth responses of N. oculata under changing light conditions, where the heterogeneity of light distribution in the cultures substantially affects growth, is crucial to optimisation of the photosynthetic efficiency and growth of microalgal cultures.
Evidence is presented to support the hypothesis that the increase in the cellular DNA content in ... more Evidence is presented to support the hypothesis that the increase in the cellular DNA content in Anacystis nidulans, which occurs in association with an increase in growth rate, indicates an increase in the number of genomes in the cell. The extent of killing and mutant reversion effected by the mutagen nitrosoguanidine was far greater in a slow-growing culture than in a fast-growing one. And, when DNA synthesis was inhibited by mitomycin C, the number of division cycles taking place before growth ceased was larger in fast-growing cultures than in slow-growing ones.
Publisher Summary This chapter discusses laboratory growth techniques and outdoor biomass product... more Publisher Summary This chapter discusses laboratory growth techniques and outdoor biomass production of micro- algae. Algal culturing techniques can be divided into two categories: the first applies to laboratory conditions and a controlled environment and the second to outdoor conditions for the larger scale production of biomass. This chapter highlights basic techniques and concepts of algal culture and presents a state-of-the-art report on algal biomass production, its problems, and achievements. Algae growing in brackish or saline water in ponds are often faced with the problem of the increasing salinity caused by evaporation. Thus, when the water source is brackish or saline the organism of choice will be capable of growing successfully in a wide range of saline conditions and thus of adapting rapidly to changes in salinity.
Wild-type cyanobacteria of the genus Ana- baena are capable of oxygenic photosynthesis, different... more Wild-type cyanobacteria of the genus Ana- baena are capable of oxygenic photosynthesis, differentiation of cells called heterocysts at semiregular intervals along the cyanobacterial filaments, and aerobic nitrogen fixation by the heterocysts. To foster analysis of the physiological processes characteristic of these cyanobacteria, we have constructed a family of shuttle vectors capable of replication and selection in Escherichia coli and, in unaltered form, in several strains of Anabaena. Highly efficient conjugative transfer of these vec- tors from E. coli to Anabaena is dependent upon the presence of broad host-range plasmid RP-4 and of helper plasmids. The shuttle vectors contain portions of plasmid pBR322 required for replication and mobilization, with sites for Anabaena re- striction enzymes deleted; cyanobacterial replicon pDUl, which lacks such sites; and determinants for resistance to chloramphenicol, streptomycin, neomycin, and erythromycin. Many filamentous cyanobacteria fix dinitrogen aerobically within specialized cells called heterocysts that differentiate at semiregular intervals along the filaments. All cyanobac- teria are capable of oxygenic photosynthesis. Genetic meth- ods usable for study of nitrogen fixation, differentiation, pat- tern formation, and photosynthesis in these organisms have long been sought. Several unicellular cyanobacteria can be transformed by DNA in the growth medium (1-3). Shuttle vectors, plasmids able to replicate in Escherichia coli and in an alternative host, have been constructed for two such strains, Anacystis nidulans strain R2 and Agmenellum quadruplicatum PR-6 (4-6). An Anacystis gene cloned in a shuttle vector in E. coli was returned to the cyanobacterium by transformation (7). To date, no reproducible transformation system is known for filamentous cyanobacteria. Conjugation provides an alternative approach to transfer of cloned DNA. RP-4 and related plasmids can transfer themselves or derivatives of themselves into a wide range of Gram-negative bacteria (8-10). Cyanobacteria have the structure and wall composition of Gram-negative bacteria
Population growth, arable land and fresh water limits, and climate change have profound implicati... more Population growth, arable land and fresh water limits, and climate change have profound implications for the ability of agriculture to meet this century’s demands for food, feed, fiber, and fuel while reducing the environmental impact of their production. Success depends on the acceptance and use of contemporary molecular techniques, as well as the increasing development of farming systems that use saline water and integrate nutrient flows.
In this study,the responses of Porphyridium sp.cells with salt-elevated bound polysaccharide to t... more In this study,the responses of Porphyridium sp.cells with salt-elevated bound polysaccharide to the stress of high proton flux density (HPFD) or chilling temperature (4 ℃) was studied in order to evaluate possible biological roles of the induced polysaccharides under environmental stresses. Addition of 0.05% polysaccharides to the Porphyridium sp.culture caused the photosynthetic activity decreased under HPFD but increased under chilling temperature (4 ℃) compared to control (culture without external addition of polysaccharide). The PSⅡ efficiency (Fv/Fm) decline was not significantly affected with the exogenous polysaccharide. Within 48 h after removal of salt from the cultures,both photosynthetic activity of the salt pre-treated cells measured under HPFD and chilling temperature (4 ℃) and bound polysaccharide content returned to the levels of un-treated cells. However,the PSⅡ efficiency of the recovery cultures measured under HPFD still kept at a higher level,especially after 6 hours,compared with control and salt treated cultures,suggesting that the high polysaccharide content induced by the salt stress may enhance PSⅡ tolerance to high photon flux density.
Algal physiology and biochemistry have been reviewed and discussed quite extensively in the last ... more Algal physiology and biochemistry have been reviewed and discussed quite extensively in the last decades. The excellent contributions by Lewin (1962), Fogg (1975) and Carr and Whitton (1973) are just a few examples of textbooks which cover a wide range of topics related to algal physiology and biochemistry. The aim of this chapter is to point out relevant areas in which Spirulina has been used as a model organism or studies whose data can be of significant importance in further understanding the growth, physiology and biochemistry of Spirulina, especially when grown in outdoor conditions.
Abstract: Light is one of the most important factors affecting photosynthesis and growth of micro... more Abstract: Light is one of the most important factors affecting photosynthesis and growth of microalgal cultures. Photosynthetic responses to light change with the stage of the culture; however, little is known about how changes in the photosynthetic capacity with the duration of batch culture affect growth at the end (final harvest day) of the culture. Accordingly, we studied the photosynthetic performance and growth of Nannochloropsis oculata in the exponential phase (day 4), the linear phase of growth (day 8) and stationary phase (day 15) of batch cultures grown under a range of light intensities from 20 to 200 μmol photons m−2 s−1. Nannochloropsis oculata showed a high ability to acclimate to changing light conditions; cells almost doubled their cellular Chl a concentration under low light conditions and increased their photosynthetic oxygen evolution capacity, which allowed this alga to maintain a stable photosynthetic efficiency in the three stages of the culture studied. Changes in the Chl a per cell under different light conditions were not paralleled by changes in antenna size, which suggests that N. oculata uses an alternative strategy to acclimate to changing light levels. Finally, increasing photosynthetic capacity in cells growing under 20 μmol photons m−2 s−1 did not avoid light limitation and decreasing exponential growth rate. However, the lack of differences in final cell density achieved between 20 and 200 μmol photons m−2 s−1 treatments suggests that bicarbonate limitation started to affect photosynthesis and growth at the higher light treatments, from the linear phase of growth onwards. Understanding of the photosynthetic and growth responses of N. oculata under changing light conditions, where the heterogeneity of light distribution in the cultures substantially affects growth, is crucial to optimisation of the photosynthetic efficiency and growth of microalgal cultures.
Evidence is presented to support the hypothesis that the increase in the cellular DNA content in ... more Evidence is presented to support the hypothesis that the increase in the cellular DNA content in Anacystis nidulans, which occurs in association with an increase in growth rate, indicates an increase in the number of genomes in the cell. The extent of killing and mutant reversion effected by the mutagen nitrosoguanidine was far greater in a slow-growing culture than in a fast-growing one. And, when DNA synthesis was inhibited by mitomycin C, the number of division cycles taking place before growth ceased was larger in fast-growing cultures than in slow-growing ones.
Publisher Summary This chapter discusses laboratory growth techniques and outdoor biomass product... more Publisher Summary This chapter discusses laboratory growth techniques and outdoor biomass production of micro- algae. Algal culturing techniques can be divided into two categories: the first applies to laboratory conditions and a controlled environment and the second to outdoor conditions for the larger scale production of biomass. This chapter highlights basic techniques and concepts of algal culture and presents a state-of-the-art report on algal biomass production, its problems, and achievements. Algae growing in brackish or saline water in ponds are often faced with the problem of the increasing salinity caused by evaporation. Thus, when the water source is brackish or saline the organism of choice will be capable of growing successfully in a wide range of saline conditions and thus of adapting rapidly to changes in salinity.
Wild-type cyanobacteria of the genus Ana- baena are capable of oxygenic photosynthesis, different... more Wild-type cyanobacteria of the genus Ana- baena are capable of oxygenic photosynthesis, differentiation of cells called heterocysts at semiregular intervals along the cyanobacterial filaments, and aerobic nitrogen fixation by the heterocysts. To foster analysis of the physiological processes characteristic of these cyanobacteria, we have constructed a family of shuttle vectors capable of replication and selection in Escherichia coli and, in unaltered form, in several strains of Anabaena. Highly efficient conjugative transfer of these vec- tors from E. coli to Anabaena is dependent upon the presence of broad host-range plasmid RP-4 and of helper plasmids. The shuttle vectors contain portions of plasmid pBR322 required for replication and mobilization, with sites for Anabaena re- striction enzymes deleted; cyanobacterial replicon pDUl, which lacks such sites; and determinants for resistance to chloramphenicol, streptomycin, neomycin, and erythromycin. Many filamentous cyanobacteria fix dinitrogen aerobically within specialized cells called heterocysts that differentiate at semiregular intervals along the filaments. All cyanobac- teria are capable of oxygenic photosynthesis. Genetic meth- ods usable for study of nitrogen fixation, differentiation, pat- tern formation, and photosynthesis in these organisms have long been sought. Several unicellular cyanobacteria can be transformed by DNA in the growth medium (1-3). Shuttle vectors, plasmids able to replicate in Escherichia coli and in an alternative host, have been constructed for two such strains, Anacystis nidulans strain R2 and Agmenellum quadruplicatum PR-6 (4-6). An Anacystis gene cloned in a shuttle vector in E. coli was returned to the cyanobacterium by transformation (7). To date, no reproducible transformation system is known for filamentous cyanobacteria. Conjugation provides an alternative approach to transfer of cloned DNA. RP-4 and related plasmids can transfer themselves or derivatives of themselves into a wide range of Gram-negative bacteria (8-10). Cyanobacteria have the structure and wall composition of Gram-negative bacteria
Population growth, arable land and fresh water limits, and climate change have profound implicati... more Population growth, arable land and fresh water limits, and climate change have profound implications for the ability of agriculture to meet this century’s demands for food, feed, fiber, and fuel while reducing the environmental impact of their production. Success depends on the acceptance and use of contemporary molecular techniques, as well as the increasing development of farming systems that use saline water and integrate nutrient flows.
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