User:Baertsch: Difference between revisions
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;Diatoms (Class Bacillariophyceae): Diatoms are among the most common and widely distributed groups of algae. The cells are golden-brown because of the presence of high levels of fucoxanthin, a photosynthetic accessory pigment.The main storage compounds of diatoms are lipids (TAGs) and a β-1,3-linked carbohydrate known as chrysolaminarin. | ;Diatoms (Class Bacillariophyceae): Diatoms are among the most common and widely distributed groups of algae. The cells are golden-brown because of the presence of high levels of fucoxanthin, a photosynthetic accessory pigment.The main storage compounds of diatoms are lipids (TAGs) and a β-1,3-linked carbohydrate known as chrysolaminarin. | ||
Several other xanthophylls are present at lower levels, as well as β-carotene, | Several other xanthophylls are present at lower levels, as well as β-carotene, | ||
chlorophyll a and chlorophyll c. | chlorophyll a and chlorophyll c. | ||
about 100,000 species are known. This group tends to | about 100,000 species are known. This group tends to | ||
dominate the phytoplankton of the oceans, but is commonly found in fresh- and | dominate the phytoplankton of the oceans, but is commonly found in fresh- and | ||
brackish-water habitats as well. | brackish-water habitats as well. | ||
distinguishing feature of diatoms is the presence of a cell wall that contains | Examples studied: | ||
* Chaetoceros muelleri (CHAET14) | |||
* Navicula (NAVIC1) | |||
* Cyclotella (CYCLO2) | |||
* Amphora (AMPHO1 and AMPHO2) | |||
NAVIC1 and CYCLO2 were actually collected from the Florida keys; the remaining strains were collected in Colorado and Utah. | |||
A distinguishing feature of diatoms is the presence of a cell wall that contains | |||
substantial quantities of polymerized Si. This has implications for media costs | substantial quantities of polymerized Si. This has implications for media costs | ||
in a commercial production facility, because silicate is a relatively expensive | in a commercial production facility, because silicate is a relatively expensive | ||
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difficult. As a consequence, diatom strain development programs must rely | difficult. As a consequence, diatom strain development programs must rely | ||
heavily on genetic engineering approaches. | heavily on genetic engineering approaches. | ||
;Golden-Brown Algae (Class Chrysophyceae): This group of algae, commonly referred to as chrysophytes, is similar to diatoms with respect to pigments and biochemical composition. | ;Golden-Brown Algae (Class Chrysophyceae): This group of algae, commonly referred to as chrysophytes, is similar to diatoms with respect to pigments and biochemical composition. | ||
Approximately 1,000 species are known, which are found primarily in freshwater habitats. Lipids and chrysolaminarin are considered to | Approximately 1,000 species are known, which are found primarily in freshwater habitats. Lipids and chrysolaminarin are considered to | ||
be the major carbon storage form in this group. Some chysophytes have lightly silicified cell walls. | be the major carbon storage form in this group. Some chysophytes have lightly silicified cell walls. | ||
;Green Algae (Class Chlorophyceae): Green algae, often referred to as chlorophytes, This group has chlorophyll a and chlorophyll b. These algae use starch as their primary storage component. | |||
;Green Algae (Class Chlorophyceae): Green algae, often referred to as chlorophytes, This group has chlorophyll a and chlorophyll b. These algae use starch as their primary storage component. | |||
approximately 8,000 species are estimated to be in existence. However, N-deficiency promotes the accumulation of lipids in | |||
certain species. Green algae are the evolutionary progenitors of higher plants, | certain species. Green algae are the evolutionary progenitors of higher plants, | ||
and, as such, have received more attention than other groups of algae. | and, as such, have received more attention than other groups of algae. | ||
Example studied: | |||
* chlorophyte Monoraphidium minutum (MONOR2) | |||
* Chlamydomonas reinhardtii | |||
has been studied very extensively, in part because of its ability to control sexual | has been studied very extensively, in part because of its ability to control sexual | ||
reproduction, thus allowing detailed genetic analysis. | reproduction, thus allowing detailed genetic analysis. | ||
was the first alga to be genetically transformed. However, it does not | Chlamydomonas was the first alga to be genetically transformed. However, it does not | ||
accumulate lipids, and thus was not considered for use in the ASP. Another | accumulate lipids, and thus was not considered for use in the ASP. Another | ||
common genus that has been studied fairly extensively is Chlorella | common genus that has been studied fairly extensively is Chlorella | ||
;Class Prymnesiophyceae: This group of algae, also known as the haptophytes, They are primarily marine organisms, and can account for a substantial proportion of the primary productivity of tropical oceans. | ;Class Prymnesiophyceae: This group of algae, also known as the haptophytes, They are primarily marine organisms, and can account for a substantial proportion of the primary productivity of tropical oceans. | ||
consistsof approximately 500 species. As with the diatoms and chrysophytes, fucoxanthin imparts a brown | consistsof approximately 500 species. As with the diatoms and chrysophytes, fucoxanthin imparts a brown |
Revision as of 13:25, 25 May 2006
Algae Research from Dept of Energy ASP Aquatic Species Program
http://www1.eere.energy.gov/biomass/pdfs/biodiesel_from_algae.pdf
There are several main groups of microalgae, which differ primarily in pigment composition, biochemical constituents, ultrastructure, and life cycle. Five groups were of primary importance to the ASP: diatoms (Class Bacillariophyceae), green algae (Class Chlorophyceae), goldenbrown algae (Class Chrysophyceae), prymnesiophytes (Class Prymnesiophyceae), and the eustigmatophytes (Class Eustigmatophyceae). The blue-green algae, or cyanobacteria (Class Cyanophyceae), were also represented in some of the collections. A brief description of these algal groups follows.
- Diatoms (Class Bacillariophyceae)
- Diatoms are among the most common and widely distributed groups of algae. The cells are golden-brown because of the presence of high levels of fucoxanthin, a photosynthetic accessory pigment.The main storage compounds of diatoms are lipids (TAGs) and a β-1,3-linked carbohydrate known as chrysolaminarin.
Several other xanthophylls are present at lower levels, as well as β-carotene, chlorophyll a and chlorophyll c. about 100,000 species are known. This group tends to dominate the phytoplankton of the oceans, but is commonly found in fresh- and brackish-water habitats as well. Examples studied:
- Chaetoceros muelleri (CHAET14)
- Navicula (NAVIC1)
- Cyclotella (CYCLO2)
- Amphora (AMPHO1 and AMPHO2)
NAVIC1 and CYCLO2 were actually collected from the Florida keys; the remaining strains were collected in Colorado and Utah. A distinguishing feature of diatoms is the presence of a cell wall that contains substantial quantities of polymerized Si. This has implications for media costs in a commercial production facility, because silicate is a relatively expensive chemical. On the other hand, Si deficiency is known to promote storage lipid accumulation in diatoms, and thus could provide a controllable means to induce lipid synthesis in a two-stage production process. Another characteristic of diatoms that distinguishes them from most other algal groups is that they are diploid (having two copies of each chromosome) during vegetative growth; most algae are haploid (with one copy of each chromosome) except for brief periods when the cells are reproducing sexually. The main ramification of this from a strain development perspective is that it makes producing improved strains via classical mutagenesis and selection/screening substantially more difficult. As a consequence, diatom strain development programs must rely heavily on genetic engineering approaches.
- Golden-Brown Algae (Class Chrysophyceae)
- This group of algae, commonly referred to as chrysophytes, is similar to diatoms with respect to pigments and biochemical composition.
Approximately 1,000 species are known, which are found primarily in freshwater habitats. Lipids and chrysolaminarin are considered to be the major carbon storage form in this group. Some chysophytes have lightly silicified cell walls.
- Green Algae (Class Chlorophyceae)
- Green algae, often referred to as chlorophytes, This group has chlorophyll a and chlorophyll b. These algae use starch as their primary storage component.
approximately 8,000 species are estimated to be in existence. However, N-deficiency promotes the accumulation of lipids in certain species. Green algae are the evolutionary progenitors of higher plants, and, as such, have received more attention than other groups of algae. Example studied:
- chlorophyte Monoraphidium minutum (MONOR2)
- Chlamydomonas reinhardtii
has been studied very extensively, in part because of its ability to control sexual reproduction, thus allowing detailed genetic analysis. Chlamydomonas was the first alga to be genetically transformed. However, it does not accumulate lipids, and thus was not considered for use in the ASP. Another common genus that has been studied fairly extensively is Chlorella
- Class Prymnesiophyceae
- This group of algae, also known as the haptophytes, They are primarily marine organisms, and can account for a substantial proportion of the primary productivity of tropical oceans.
consistsof approximately 500 species. As with the diatoms and chrysophytes, fucoxanthin imparts a brown color to the cells, and lipids and chrysolaminarin are the major storage products. This group includes the coccolithophorids, which are distinguished by calcareous scales surrounding the cell wall.
- Eustigmatophytes
- This group represents an important component of the “picoplankton”, which are very small cells (2-4 μm in diameter).
The genus Nannochloropsis is one of the few marine species in this class, and is common in the world’s oceans. Chlorophyll a is the only chlorophyll present in the cells, although several xanthophylls serve as accessory photosynthetic pigments.
- Cyanobacteria (Class Cyanophyceae)
- Bacteria, They contain no nucleus, no chloroplasts, and have a different gene structure.
This group is prokaryotic, and therefore very different from all other groups of microalgae. There are approximately 2,000 species of cyanobacteria, which occur in many habitats. Although this group is distinguished by having members that can assimilate atmospheric N (thus eliminating the need to provide fixed N to the cells), no member of this class produces significant quantities of storage lipid; therefore, this group was not deemed useful to the ASP.