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Published on: August 28, 2018
A biological function for cadmium in marine diatoms
1Department of Geosciences, Princeton University, Princeton, NJ 08544-1003, USA. tlane@princeton.edu
Summary
Marine diatoms utilize cadmium (Cd) in a specific carbonic anhydrase (CA) enzyme when zinc (Zn) is scarce. This Cd-specific CA aids carbon acquisition, enhancing diatom growth in low-zinc environments.
Area of Science:
- Marine biology
- Biochemistry
- Oceanography
Background:
- Cadmium's oceanic distribution mirrors nutrient patterns, but its biological role is poorly understood.
- Cadmium is not typically considered essential for marine life.
- Marine diatoms are crucial primary producers in ocean ecosystems.
Purpose of the Study:
- To investigate the biological role of cadmium in the marine diatom Thalassiosira weissflogii.
- To explore cadmium's function under zinc-limited conditions.
- To understand cadmium's contribution to carbon acquisition in diatoms.
Main Methods:
- Culturing Thalassiosira weissflogii under varying zinc and CO2 conditions.
- Measuring growth rates and cellular carbonic anhydrase activity.
- Utilizing (109)Cd radiolabeling and native PAGE to identify cadmium-binding proteins.
- Purifying the cadmium-containing carbonic anhydrase.
Main Results:
- Cadmium addition enhanced growth rates in zinc-limited T. weissflogii cultures, especially at low pCO2.
- A cadmium-containing carbonic anhydrase (CA) distinct from the zinc-dependent TWCA1 was identified.
- This cadmium-specific CA showed activity modulated by CO2 levels, indicating a role in carbon acquisition.
- Purification isolated a 43 kDa cadmium-containing CA protein.
Conclusions:
- Thalassiosira weissflogii possesses a cadmium-specific carbonic anhydrase.
- This cadmium-dependent CA can substitute for the zinc-dependent enzyme (TWCA1) in the carbon-concentrating mechanism under zinc limitation.
- Cadmium plays a vital biological role in marine diatoms, particularly in low-zinc environments, impacting carbon fixation and primary productivity.
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