avigad vonshak | Ben Gurion University (original) (raw)
Papers by avigad vonshak
Guangxi Zhiwu, 2004
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.
Functional Plant Biology, 1999
CRC Press eBooks, May 21, 1997
CRC Press eBooks, May 21, 1997
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.
Phycologia, Sep 1, 2018
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.
Springer eBooks, 1985
The effects of environmental conditions (solar irradiance and temperature) and population density... more The effects of environmental conditions (solar irradiance and temperature) and population density on the production of Spirulina biomass with brackish water are reported for cultures grown in outdoor ponds. Higher specific growth rates were observed at lower population densities. Lower growth rates were associated with limitation by light in dense cultures under optimum conditions in the summer. Seasonal variation in productivity was observed. In summer, light was the limiting factor, whereas in winter the low daytime temperature appeared to constitute the major limitation. The oxygen concentration in the culture can serve as a useful indicator of limiting factors and can also be used to estimate the extent of such limitations.
Biomass, 1988
Progress has been made in the past decade in developing appropriate technology for microalgal mas... more Progress has been made in the past decade in developing appropriate technology for microalgal mass cultivation. This review details basic requirements required in order to achieve high productivity and low cost of production. There is a need for a wide variety of algal species and strains that will favorably respond to the varying environmental conditions existing outdoors. Another essential requirement is for better bioreactors, either by improving existing open raceway types or developing tubular closed systems. The latter solution seems more promising. These developments must overcome the main limitation confronting the industry today which is the overall low areal yields which fall too short of the theoretical maximum and which are associated with scaling up microalgal culture to commercial size.
Plant and Cell Physiology, Dec 1, 1981
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.
Elsevier eBooks, 1985
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.
John Wiley & Sons, Ltd eBooks, Apr 12, 2013
When dealing with a photoautotrophic growth system, the biological process that drives growth and... more When dealing with a photoautotrophic growth system, the biological process that drives growth and productivity is the ability of the cells via their photosynthetic apparatus to capture light and convert it efficiently to chemical energy. This chapter examines the basic principles of algal photosynthesis and growth physiology in order to provide the reader with the necessary background for a more comprehensive understanding of the effect of stress on algal photosynthesis and growth. Particular emphasis has been put on the light acclimation process of outdoor microalgae cultures and on the synergistic effect of light and other environmental stress such as low temperature, salinity, and high oxygen concentrations on algal photosynthesis and productivity. Chlorophyll fluorescence measurement has been suggested as a powerful tool to rapidly monitor the effect of stress on algal photosynthesis and growth. We strongly believe that the future of algal biotechnology highly depends on the ability to better understand its biological limitations and what needs to be overcome in order to significantly improve productivity.
Microbiological Research, Apr 1, 2000
The effects of temperature, Mg2+, EDTA concentration and rinsing on extra-and intra-cellular DNas... more The effects of temperature, Mg2+, EDTA concentration and rinsing on extra-and intra-cellular DNase activity of Spirulina platensis strain SSP-14, were investigated. The results indicate that the tested strain contains very high extra-and intracellular DNase activity, which actually hinders the transfer of foreign gene(s) to S. platensis, a cyanobacterium with multiple economic potentials. The extracellular DNase activity could easily be removed by rinsing the cells with Zarrouk medium more than once. The intracellular DNase activity could also be inhibited by (1) removal of Mg2+, (2) maintaining EDTA concentration above I mmol I-I, and (3) manipulating below 0-4°C, during all the incubation procedures. We suggest that, by using one or more of, or combining, all those experimental conditions, the chances of foreign DNA attempted to be introduced into S. platensis without being digested would be increased.
Photochemical and Photobiological Sciences, Sep 8, 2022
The photosynthetic apparatus is a major reactive oxygen species (ROS) proliferator, especially in... more The photosynthetic apparatus is a major reactive oxygen species (ROS) proliferator, especially in highlight environments. The role of ROS in photoinhibition and photoacclimation mechanisms has been extensively explored, primarily in model plant species. However, little work has been performed on the topic in non-Archaeplastida organisms, such as the model heterokont species Nannochloropsis oceanica. To investigate the photoacclimation and damaging impact of singlet oxygen and superoxide anions on the photosynthetic apparatus of N. oceanica, we subjected cells to two doses of methyl viologen and rose bengal. Significant findings: Rose bengal (a singlet-oxygen photosensitizer) induced changes to the photosynthetic apparatus and PSII photochemistry mirroring highlight -acclimated cells, suggesting that singlet-oxygen signaling plays a role in the highlight acclimation of PSII. We further suggest that this singlet-oxygen pathway is mediated outside the plastid, given that rose bengal caused no detectable damage to the photosynthetic apparatus. Methyl viologen (a superoxide-anion sensitizer) induced an enhanced non-photochemical quenching response, similar to what occurs in highlight -acclimated cells. We propose that superoxide anions produced inside the plastid help regulate the highlight acclimation of photoprotective pathways.
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
European Journal of Phycology
Science, 2010
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.
Plant Physiology, Aug 1, 1981
Anacystis nidulans cultures growing photoautotrophically in a minimal medium were exposed to diff... more Anacystis nidulans cultures growing photoautotrophically in a minimal medium were exposed to different concentrations of NaCI, up to 0.4 molar. Initially, a marked decrease in photosynthetic activity took place, which was in direct relation to the salt concentration and which was not associated with a change in endogenous respiratory activity. After a period of exposure to salinity, a process of adaptation became apparent, being manifested in a partial reversal of the decline in photosynthesis and a marked increase in endogenous respiration.
Guangxi Zhiwu, 2004
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.
Functional Plant Biology, 1999
CRC Press eBooks, May 21, 1997
CRC Press eBooks, May 21, 1997
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.
Phycologia, Sep 1, 2018
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.
Springer eBooks, 1985
The effects of environmental conditions (solar irradiance and temperature) and population density... more The effects of environmental conditions (solar irradiance and temperature) and population density on the production of Spirulina biomass with brackish water are reported for cultures grown in outdoor ponds. Higher specific growth rates were observed at lower population densities. Lower growth rates were associated with limitation by light in dense cultures under optimum conditions in the summer. Seasonal variation in productivity was observed. In summer, light was the limiting factor, whereas in winter the low daytime temperature appeared to constitute the major limitation. The oxygen concentration in the culture can serve as a useful indicator of limiting factors and can also be used to estimate the extent of such limitations.
Biomass, 1988
Progress has been made in the past decade in developing appropriate technology for microalgal mas... more Progress has been made in the past decade in developing appropriate technology for microalgal mass cultivation. This review details basic requirements required in order to achieve high productivity and low cost of production. There is a need for a wide variety of algal species and strains that will favorably respond to the varying environmental conditions existing outdoors. Another essential requirement is for better bioreactors, either by improving existing open raceway types or developing tubular closed systems. The latter solution seems more promising. These developments must overcome the main limitation confronting the industry today which is the overall low areal yields which fall too short of the theoretical maximum and which are associated with scaling up microalgal culture to commercial size.
Plant and Cell Physiology, Dec 1, 1981
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.
Elsevier eBooks, 1985
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.
John Wiley & Sons, Ltd eBooks, Apr 12, 2013
When dealing with a photoautotrophic growth system, the biological process that drives growth and... more When dealing with a photoautotrophic growth system, the biological process that drives growth and productivity is the ability of the cells via their photosynthetic apparatus to capture light and convert it efficiently to chemical energy. This chapter examines the basic principles of algal photosynthesis and growth physiology in order to provide the reader with the necessary background for a more comprehensive understanding of the effect of stress on algal photosynthesis and growth. Particular emphasis has been put on the light acclimation process of outdoor microalgae cultures and on the synergistic effect of light and other environmental stress such as low temperature, salinity, and high oxygen concentrations on algal photosynthesis and productivity. Chlorophyll fluorescence measurement has been suggested as a powerful tool to rapidly monitor the effect of stress on algal photosynthesis and growth. We strongly believe that the future of algal biotechnology highly depends on the ability to better understand its biological limitations and what needs to be overcome in order to significantly improve productivity.
Microbiological Research, Apr 1, 2000
The effects of temperature, Mg2+, EDTA concentration and rinsing on extra-and intra-cellular DNas... more The effects of temperature, Mg2+, EDTA concentration and rinsing on extra-and intra-cellular DNase activity of Spirulina platensis strain SSP-14, were investigated. The results indicate that the tested strain contains very high extra-and intracellular DNase activity, which actually hinders the transfer of foreign gene(s) to S. platensis, a cyanobacterium with multiple economic potentials. The extracellular DNase activity could easily be removed by rinsing the cells with Zarrouk medium more than once. The intracellular DNase activity could also be inhibited by (1) removal of Mg2+, (2) maintaining EDTA concentration above I mmol I-I, and (3) manipulating below 0-4°C, during all the incubation procedures. We suggest that, by using one or more of, or combining, all those experimental conditions, the chances of foreign DNA attempted to be introduced into S. platensis without being digested would be increased.
Photochemical and Photobiological Sciences, Sep 8, 2022
The photosynthetic apparatus is a major reactive oxygen species (ROS) proliferator, especially in... more The photosynthetic apparatus is a major reactive oxygen species (ROS) proliferator, especially in highlight environments. The role of ROS in photoinhibition and photoacclimation mechanisms has been extensively explored, primarily in model plant species. However, little work has been performed on the topic in non-Archaeplastida organisms, such as the model heterokont species Nannochloropsis oceanica. To investigate the photoacclimation and damaging impact of singlet oxygen and superoxide anions on the photosynthetic apparatus of N. oceanica, we subjected cells to two doses of methyl viologen and rose bengal. Significant findings: Rose bengal (a singlet-oxygen photosensitizer) induced changes to the photosynthetic apparatus and PSII photochemistry mirroring highlight -acclimated cells, suggesting that singlet-oxygen signaling plays a role in the highlight acclimation of PSII. We further suggest that this singlet-oxygen pathway is mediated outside the plastid, given that rose bengal caused no detectable damage to the photosynthetic apparatus. Methyl viologen (a superoxide-anion sensitizer) induced an enhanced non-photochemical quenching response, similar to what occurs in highlight -acclimated cells. We propose that superoxide anions produced inside the plastid help regulate the highlight acclimation of photoprotective pathways.
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
European Journal of Phycology
Science, 2010
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.
Plant Physiology, Aug 1, 1981
Anacystis nidulans cultures growing photoautotrophically in a minimal medium were exposed to diff... more Anacystis nidulans cultures growing photoautotrophically in a minimal medium were exposed to different concentrations of NaCI, up to 0.4 molar. Initially, a marked decrease in photosynthetic activity took place, which was in direct relation to the salt concentration and which was not associated with a change in endogenous respiratory activity. After a period of exposure to salinity, a process of adaptation became apparent, being manifested in a partial reversal of the decline in photosynthesis and a marked increase in endogenous respiration.