Photolithotrophs are divided between those that use water as their electron
donor (Cyanobacteria ... more Photolithotrophs are divided between those that use water as their electron donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a different electron donor (the anoxygenic photolithotrophs, all of themBacteria). Photolithotrophs with themost reduced genomes have more genes than do the corresponding chemoorganotrophs, and the fastest-growing photolithotrophs have significantly lower specific growth rates than the fastest-growing chemoorganotrophs. Slower growth results from diversion of resources into the photosynthetic apparatus, which accounts for about half of the cell protein. There are inherent dangers in (especially oxygenic) photosynthesis, including the formation of reactive oxygen species (ROS) and blue light sensitivity of the water spitting apparatus. The extent to which photolithotrophs incur greater DNA damage and repair, and faster protein turnover with increased rRNA requirement, needs further investigation. A related source of environmental damage is ultraviolet B (UVB) radiation (280–320 nm), whose flux at the Earth’s surface decreased as oxygen (and ozone) increased in the atmosphere. This oxygenation led to the requirements of defence againstROS, and decreasing availability to organisms of combined (non-dinitrogen) nitrogen and ferrous iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential codon usage in the genome and, especially, the proteome can lead to economies in the use of potentially growth-limiting elements
Atmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since... more Atmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since the beginning of industrialisation. A significant fraction of this increase can be attributed to the emissions from stationary sources such as thermal power plants and steel plants. While there has been an impetus in recent times towards sequestration of these greenhouse gases at source, current technologies are not commercially viable. In this context, microalgae-mediated CO2 capture and utilization has attracted attention, although several technological challenges remain to be addressed. Importantly, this process will require algal strains that grow fast and are tolerant to high light, temperature and flue gases. The majority of the reported algal strains fail in at least one of these requirements. On account of this, we have isolated two novel green algal strains, which have been identified as Asterarcys quadricellulare and Chlorella sorokiniana, from water bodies that are located in and around a steel plant in India. These are relatively fast-growing strains with specific growth rates of up to 0.06 h− 1 and 0.1 h− 1, respectively. Furthermore, these strains can tolerate high temperatures of up to 43 °C, high light intensity and high CO2 and NO levels. When exposed to high CO2 levels, 55–71% of the dry cell weight comprised of carbohydrates. Additionally, exposure to NO gas along with CO2 led to an enhanced lipid accumulation of 44%–46% of dry biomass. The high lipid content makes these strains valuable feedstock in biodiesel production, and the high carbohydrate content makes the lipid extracted biomass an attractive source of carbon for biochemical conversion to ethanol. We believe that these strains are promising and ready to be tested with real flue gases under outdoor conditions.
Abstract The importance of algae-derived biofuels has been
highlighted by the current problems as... more Abstract The importance of algae-derived biofuels has been highlighted by the current problems associated with fossil fuels. Considerable past research has shown that limiting nutrients such as nitrogen and phosphorus increases the cellular lipid content in microalgae. However, limiting the supply of nutrients results in decreased biomass, which in turn decreases the overall lipid productivity of cultures. Therefore, nutrient limitation has been a subject of dispute as to whether it will benefit biofuel production on an industrial scale. Our research explores the physiological changes a cell undergoes when exposed to nitrogen and phosphorus limitations, both individually and in combination, and also examines the biotechnological aspects of manipulating N and P in order to increase cellular lipids, by analyzing the lipid production. We show that nitrogen starvation and also nitrogen plus phosphorus starvation combined have a more profound effect on the physiology and macromolecular pools of Chlamydomonas reinhardtii than does phosphorus starvation alone. The photosynthetic performance of C. reinhardtii underwent drastic changes under nitrogen starvation, but remained relatively unaffected under phosphorus starvation. The neutral lipid concentration per cell was at least 2.4-fold higher in all the nutrient-starved groups than the nutrient-replete controls, but the protein level per cell was lower in the nitrogen-starved groups. Overall, nitrogen starvation has a more dramatic effect on the physiology and neutral lipids and protein levels of C. reinhardtii than phosphorus starvation. However, the level of total lipids per volume of culture obtained was similar among nutrient-replete and all of the nutrient-starved groups. We conclude that combined nitrogen and phosphorus starvation does not likely benefit biofuel production in terms of enhanced lipid or biomass production
Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a n... more Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a number of microalgae. Respiration rates, as determined by O 2 consumption, were enhanced (in all but one case) by 50–140% following pre-exposure to high photon flux ...
... However, the Lowry assay may overestimate (Berges et al. ... In most of the phytoplankton stu... more ... However, the Lowry assay may overestimate (Berges et al. ... In most of the phytoplankton studies cited here, the orcinol and Lowry methods were used ... a much greater range of RNA-specific protein synthesis rates than of growth rates in this interspecies comparison involving nine ...
Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a n... more Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a number of microalgae. Respiration rates, as determined by O 2 consumption, were enhanced (in all but one case) by 50–140% following pre-exposure to high photon flux ...
At least 95% of the organic carbon in cyanobacteria and algae has been fixed as CO2 by Rubisco. T... more At least 95% of the organic carbon in cyanobacteria and algae has been fixed as CO2 by Rubisco. The kinetic properties of Rubisco are such that even the genetic variants with the highest CO2:O2 selectivity would show limited CO2 fixation and significant oxygenase activity if CO2 and O2 fluxes into cells are driven solely by diffusion. This is especially the case for submerged algae with low gas diffusion coefficients relative to diffusion boundary layer thicknesses. There is evidence from gas exchange properties and intracellular inorganic concentration that inorganic carbon concentrating mechanisms (CCMs) function in all cyanobacteria and many algae. CCMs can, in theory, operate through three categories of mechanism: the first mechanism is active transport of HCO-3 and/or CO2 across membranes, the second is CO2 pumping by a biochemical mechanism analogous to C4 and CAM (Crassulacean Acid Metabolism) pathways in higher land plants, and the third mechanism involves active transport of H+ producing an acid compartment supplied with HCO-3, which generates a high (equilibrium) CO2 concentration that supplies CO2 to Rubisco in a nearby more alkaline compartment. Most evidence favors the first mechanism as being responsible for CCM activity in algae. The CO2 (and HCO-3) permeability of membranes is crucial in defining the extent of inorganic C leakage from CCMs, and the functioning of diffusive CO2 supply to Rubisco from the medium. Like carbonic anhydrases, CCMs, are probably polyphyletic.
Photolithotrophs are divided between those that use water as their electron
donor (Cyanobacteria ... more Photolithotrophs are divided between those that use water as their electron donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a different electron donor (the anoxygenic photolithotrophs, all of themBacteria). Photolithotrophs with themost reduced genomes have more genes than do the corresponding chemoorganotrophs, and the fastest-growing photolithotrophs have significantly lower specific growth rates than the fastest-growing chemoorganotrophs. Slower growth results from diversion of resources into the photosynthetic apparatus, which accounts for about half of the cell protein. There are inherent dangers in (especially oxygenic) photosynthesis, including the formation of reactive oxygen species (ROS) and blue light sensitivity of the water spitting apparatus. The extent to which photolithotrophs incur greater DNA damage and repair, and faster protein turnover with increased rRNA requirement, needs further investigation. A related source of environmental damage is ultraviolet B (UVB) radiation (280–320 nm), whose flux at the Earth’s surface decreased as oxygen (and ozone) increased in the atmosphere. This oxygenation led to the requirements of defence againstROS, and decreasing availability to organisms of combined (non-dinitrogen) nitrogen and ferrous iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential codon usage in the genome and, especially, the proteome can lead to economies in the use of potentially growth-limiting elements
Atmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since... more Atmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since the beginning of industrialisation. A significant fraction of this increase can be attributed to the emissions from stationary sources such as thermal power plants and steel plants. While there has been an impetus in recent times towards sequestration of these greenhouse gases at source, current technologies are not commercially viable. In this context, microalgae-mediated CO2 capture and utilization has attracted attention, although several technological challenges remain to be addressed. Importantly, this process will require algal strains that grow fast and are tolerant to high light, temperature and flue gases. The majority of the reported algal strains fail in at least one of these requirements. On account of this, we have isolated two novel green algal strains, which have been identified as Asterarcys quadricellulare and Chlorella sorokiniana, from water bodies that are located in and around a steel plant in India. These are relatively fast-growing strains with specific growth rates of up to 0.06 h− 1 and 0.1 h− 1, respectively. Furthermore, these strains can tolerate high temperatures of up to 43 °C, high light intensity and high CO2 and NO levels. When exposed to high CO2 levels, 55–71% of the dry cell weight comprised of carbohydrates. Additionally, exposure to NO gas along with CO2 led to an enhanced lipid accumulation of 44%–46% of dry biomass. The high lipid content makes these strains valuable feedstock in biodiesel production, and the high carbohydrate content makes the lipid extracted biomass an attractive source of carbon for biochemical conversion to ethanol. We believe that these strains are promising and ready to be tested with real flue gases under outdoor conditions.
Abstract The importance of algae-derived biofuels has been
highlighted by the current problems as... more Abstract The importance of algae-derived biofuels has been highlighted by the current problems associated with fossil fuels. Considerable past research has shown that limiting nutrients such as nitrogen and phosphorus increases the cellular lipid content in microalgae. However, limiting the supply of nutrients results in decreased biomass, which in turn decreases the overall lipid productivity of cultures. Therefore, nutrient limitation has been a subject of dispute as to whether it will benefit biofuel production on an industrial scale. Our research explores the physiological changes a cell undergoes when exposed to nitrogen and phosphorus limitations, both individually and in combination, and also examines the biotechnological aspects of manipulating N and P in order to increase cellular lipids, by analyzing the lipid production. We show that nitrogen starvation and also nitrogen plus phosphorus starvation combined have a more profound effect on the physiology and macromolecular pools of Chlamydomonas reinhardtii than does phosphorus starvation alone. The photosynthetic performance of C. reinhardtii underwent drastic changes under nitrogen starvation, but remained relatively unaffected under phosphorus starvation. The neutral lipid concentration per cell was at least 2.4-fold higher in all the nutrient-starved groups than the nutrient-replete controls, but the protein level per cell was lower in the nitrogen-starved groups. Overall, nitrogen starvation has a more dramatic effect on the physiology and neutral lipids and protein levels of C. reinhardtii than phosphorus starvation. However, the level of total lipids per volume of culture obtained was similar among nutrient-replete and all of the nutrient-starved groups. We conclude that combined nitrogen and phosphorus starvation does not likely benefit biofuel production in terms of enhanced lipid or biomass production
Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a n... more Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a number of microalgae. Respiration rates, as determined by O 2 consumption, were enhanced (in all but one case) by 50–140% following pre-exposure to high photon flux ...
... However, the Lowry assay may overestimate (Berges et al. ... In most of the phytoplankton stu... more ... However, the Lowry assay may overestimate (Berges et al. ... In most of the phytoplankton studies cited here, the orcinol and Lowry methods were used ... a much greater range of RNA-specific protein synthesis rates than of growth rates in this interspecies comparison involving nine ...
Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a n... more Abstract The extent of enhanced post-illumination respiration (EPIR) has been investigated in a number of microalgae. Respiration rates, as determined by O 2 consumption, were enhanced (in all but one case) by 50–140% following pre-exposure to high photon flux ...
At least 95% of the organic carbon in cyanobacteria and algae has been fixed as CO2 by Rubisco. T... more At least 95% of the organic carbon in cyanobacteria and algae has been fixed as CO2 by Rubisco. The kinetic properties of Rubisco are such that even the genetic variants with the highest CO2:O2 selectivity would show limited CO2 fixation and significant oxygenase activity if CO2 and O2 fluxes into cells are driven solely by diffusion. This is especially the case for submerged algae with low gas diffusion coefficients relative to diffusion boundary layer thicknesses. There is evidence from gas exchange properties and intracellular inorganic concentration that inorganic carbon concentrating mechanisms (CCMs) function in all cyanobacteria and many algae. CCMs can, in theory, operate through three categories of mechanism: the first mechanism is active transport of HCO-3 and/or CO2 across membranes, the second is CO2 pumping by a biochemical mechanism analogous to C4 and CAM (Crassulacean Acid Metabolism) pathways in higher land plants, and the third mechanism involves active transport of H+ producing an acid compartment supplied with HCO-3, which generates a high (equilibrium) CO2 concentration that supplies CO2 to Rubisco in a nearby more alkaline compartment. Most evidence favors the first mechanism as being responsible for CCM activity in algae. The CO2 (and HCO-3) permeability of membranes is crucial in defining the extent of inorganic C leakage from CCMs, and the functioning of diffusive CO2 supply to Rubisco from the medium. Like carbonic anhydrases, CCMs, are probably polyphyletic.
Uploads
Papers by john.beardall@monash.edu Beardall
donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a
different electron donor (the anoxygenic photolithotrophs, all of themBacteria).
Photolithotrophs with themost reduced genomes have more genes than do the
corresponding chemoorganotrophs, and the fastest-growing photolithotrophs
have significantly lower specific growth rates than the fastest-growing chemoorganotrophs.
Slower growth results from diversion of resources into the
photosynthetic apparatus, which accounts for about half of the cell protein.
There are inherent dangers in (especially oxygenic) photosynthesis, including
the formation of reactive oxygen species (ROS) and blue light sensitivity of the
water spitting apparatus. The extent to which photolithotrophs incur greater
DNA damage and repair, and faster protein turnover with increased rRNA
requirement, needs further investigation. A related source of environmental
damage is ultraviolet B (UVB) radiation (280–320 nm), whose flux at the
Earth’s surface decreased as oxygen (and ozone) increased in the atmosphere.
This oxygenation led to the requirements of defence againstROS, and decreasing
availability to organisms of combined (non-dinitrogen) nitrogen and ferrous
iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential
codon usage in the genome and, especially, the proteome can lead to economies
in the use of potentially growth-limiting elements
highlighted by the current problems associated with fossil
fuels. Considerable past research has shown that limiting nutrients
such as nitrogen and phosphorus increases the cellular
lipid content in microalgae. However, limiting the supply of
nutrients results in decreased biomass, which in turn decreases
the overall lipid productivity of cultures. Therefore, nutrient
limitation has been a subject of dispute as to whether it will
benefit biofuel production on an industrial scale. Our research
explores the physiological changes a cell undergoes when
exposed to nitrogen and phosphorus limitations, both individually
and in combination, and also examines the biotechnological
aspects of manipulating N and P in order to increase
cellular lipids, by analyzing the lipid production. We show
that nitrogen starvation and also nitrogen plus phosphorus
starvation combined have a more profound effect on the physiology
and macromolecular pools of Chlamydomonas
reinhardtii than does phosphorus starvation alone. The photosynthetic
performance of C. reinhardtii underwent drastic
changes under nitrogen starvation, but remained relatively unaffected
under phosphorus starvation. The neutral lipid concentration
per cell was at least 2.4-fold higher in all the
nutrient-starved groups than the nutrient-replete controls, but
the protein level per cell was lower in the nitrogen-starved
groups. Overall, nitrogen starvation has a more dramatic effect
on the physiology and neutral lipids and protein levels of
C. reinhardtii than phosphorus starvation. However, the level
of total lipids per volume of culture obtained was similar
among nutrient-replete and all of the nutrient-starved groups.
We conclude that combined nitrogen and phosphorus starvation
does not likely benefit biofuel production in terms of
enhanced lipid or biomass production
donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a
different electron donor (the anoxygenic photolithotrophs, all of themBacteria).
Photolithotrophs with themost reduced genomes have more genes than do the
corresponding chemoorganotrophs, and the fastest-growing photolithotrophs
have significantly lower specific growth rates than the fastest-growing chemoorganotrophs.
Slower growth results from diversion of resources into the
photosynthetic apparatus, which accounts for about half of the cell protein.
There are inherent dangers in (especially oxygenic) photosynthesis, including
the formation of reactive oxygen species (ROS) and blue light sensitivity of the
water spitting apparatus. The extent to which photolithotrophs incur greater
DNA damage and repair, and faster protein turnover with increased rRNA
requirement, needs further investigation. A related source of environmental
damage is ultraviolet B (UVB) radiation (280–320 nm), whose flux at the
Earth’s surface decreased as oxygen (and ozone) increased in the atmosphere.
This oxygenation led to the requirements of defence againstROS, and decreasing
availability to organisms of combined (non-dinitrogen) nitrogen and ferrous
iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential
codon usage in the genome and, especially, the proteome can lead to economies
in the use of potentially growth-limiting elements
highlighted by the current problems associated with fossil
fuels. Considerable past research has shown that limiting nutrients
such as nitrogen and phosphorus increases the cellular
lipid content in microalgae. However, limiting the supply of
nutrients results in decreased biomass, which in turn decreases
the overall lipid productivity of cultures. Therefore, nutrient
limitation has been a subject of dispute as to whether it will
benefit biofuel production on an industrial scale. Our research
explores the physiological changes a cell undergoes when
exposed to nitrogen and phosphorus limitations, both individually
and in combination, and also examines the biotechnological
aspects of manipulating N and P in order to increase
cellular lipids, by analyzing the lipid production. We show
that nitrogen starvation and also nitrogen plus phosphorus
starvation combined have a more profound effect on the physiology
and macromolecular pools of Chlamydomonas
reinhardtii than does phosphorus starvation alone. The photosynthetic
performance of C. reinhardtii underwent drastic
changes under nitrogen starvation, but remained relatively unaffected
under phosphorus starvation. The neutral lipid concentration
per cell was at least 2.4-fold higher in all the
nutrient-starved groups than the nutrient-replete controls, but
the protein level per cell was lower in the nitrogen-starved
groups. Overall, nitrogen starvation has a more dramatic effect
on the physiology and neutral lipids and protein levels of
C. reinhardtii than phosphorus starvation. However, the level
of total lipids per volume of culture obtained was similar
among nutrient-replete and all of the nutrient-starved groups.
We conclude that combined nitrogen and phosphorus starvation
does not likely benefit biofuel production in terms of
enhanced lipid or biomass production