Related Experiment Video
Updated: Jul 5, 2026
07:26
Metabolic Pathway Confirmation and Discovery Through 13C-labeling of Proteinogenic Amino Acids
Published on: January 26, 2012
Diel rhythmicity in amino acid uptake by Prochlorococcus
Isabelle Mary1, Laurence Garczarek, Glen A Tarran
1National Oceanography Centre, Southampton SO14 3ZH, UK.
Environmental Microbiology
|April 24, 2008
Summary
Marine Prochlorococcus, vital to ocean ecosystems, shows diel rhythms in amino acid uptake, increasing at dusk. This timing is linked to cell cycle stages, impacting protein synthesis and competition with other microbes.
Area of Science:
- Marine microbiology
- Oceanic biogeochemistry
- Phytoplankton physiology
Background:
- Prochlorococcus is the most abundant phototroph, dominating nitrogen-depleted gyres.
- This genus utilizes inorganic and organic nitrogen, including amino acids.
- Understanding organic nitrogen acquisition is crucial for marine food webs.
Purpose of the Study:
- Investigate diel rhythmicity in amino acid uptake by Prochlorococcus.
- Determine if amino acid uptake is linked to specific cell cycle stages.
- Assess the ecological implications of Prochlorococcus's nitrogen acquisition strategy.
Main Methods:
- Isotopic tracer techniques ((35)S-methionine, (3)H-leucine) were employed.
- Flow cytometric cell sorting identified different cell cycle stages (G1, S+G2).
- Cyclostat experiments with axenic Prochlorococcus cultures confirmed uptake patterns.
Main Results:
- Prochlorococcus exhibited significant diurnal rhythms in methionine uptake, unlike Synechococcus.
- Amino acid uptake rates were lower at dawn and higher at dusk.
- Cells in S+G2 stages showed higher leucine uptake (2.2x) than G1 cells.
- Uptake increased 3.5-fold from dawn to dusk in S+G2 cells for protein synthesis.
Conclusions:
- Prochlorococcus's amino acid uptake is strongly regulated by diel cycles and cell cycle progression.
- This diurnal regulation optimizes protein synthesis and prepares for cell division.
- Prochlorococcus exerts significant, diurnally variable competitive pressure on bacterioplankton for amino acids in nitrogen-limited waters.
Related Concept Videos
01:18Amino Acid Catabolism
Microorganisms rely on proteins as an essential carbon and energy source, particularly in environments with limited polysaccharides or lipids. However, proteins are too large to cross the plasma membrane unaided, necessitating enzymatic degradation. Microbes secrete extracellular proteases and peptidases that hydrolyze proteins into peptides, which can then be transported across the membrane. Once inside the cell, intracellular proteases degrade these peptides into free amino acids, which...
01:29Amino Acid Biosynthetic Pathways
Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which provide...
01:23Stringent Response in E. coli
Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
01:22Protein Transport to the Thylakoids
Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
01:15Metabolism of Chemolithotrophs
Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation. However, because inorganic electron donors...
01:18Deep Sea Microbial Ecology
The deep ocean and its underlying sediments represent vast, largely unexplored microbial habitats that extend far beyond the sunlit photic zone. The photic (euphotic) zone typically spans the upper ~100–200 meters of pelagic waters in the open ocean, but its depth varies geographically and seasonally, where sufficient light supports photosynthetic life. Below this lies the deep sea, spanning roughly 1000–6000 meters (bathypelagic to abyssal zones), with deeper hadal trenches extending beyond...