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How old is Prochlorococcus?
Chisholm estimates that Prochlorococcus is responsible for about 5 to 10% of the photosynthesis on Earth today. She traces its origins back 3.5 billion years to cells with mutations that resulted in the release of oxygen into the atmosphere.
How many Prochlorococcus are there?
These waters contain an estimated 3 billion billion billion Prochlorococcus cells, collectively weighing as much as 220 million Volkswagen Beetles. That abundance makes the microbe a heavyweight in ocean food webs and climate.
What does Prochlorococcus need to survive?
Moreover, Prochlorococcus have adapted to use sulfolipids instead of phospholipids in their membranes to survive in phosphate deprived environments. This adaptation allows them to avoid competition with heterotrophs that are dependent on phosphate for survival.
What is the importance of Prochlorococcus?
Prochlorococcus is a key component in the transfer of carbon and energy through open ocean food webs (Flombaum et al., 2013; Biller et al., 2015).
Who discovered Prochlorococcus marinus?
PalenikThe first Prochlorococcus strain was isolated by Palenik in May 1988 from the bottom of the euphotic zone in the Sargasso Sea (depth, 120 m).
How big are Prochlorococcus?
Their tiny cell sizes (0.5–0.7 μm) make Prochlorococcus spp. the smallest photosynthetic organisms known to date.
Is Prochlorococcus a cyanobacterium?
The marine unicellular cyanobacterium Prochlorococcus is the most abundant photosynthetic organism on Earth. Members of this genus are classically thought to be adapted to high-oxygen and nutrient-poor ocean conditions, with a principle divergence between high-light and low-light ecotypes.
How do you grow Prochlorococcus?
Prochlorococcus grows robustly at low cell concentrations, in liquid or on solid medium, when cocultured with marine heterotrophic bacteria. Once the Prochlorococcus cell concentration surpasses a critical threshold, the "helper" heterotrophs can be eliminated with antibiotics to produce axenic cultures.
Why are Phytoplanktons dying?
Indeed, Worm's team estimates that phytoplankton numbers have plummeted 40% since 1950. What's more, the team found that phytoplankton numbers were more likely to dwindle in areas of the ocean that were warming, suggesting that climate change is responsible for the drop.
How does Prochlorococcus survive?
The ability of Prochlorococcus to thrive under conditions of extreme nutrient limitation is often explained by their small cell size (increasing their biomass-specific diffusion), their generally low nutrient requirements, and their specific metabolic strategies to minimize the per-cell elemental quotas (53–55).
What are two differences between Synechococcus and Prochlorococcus?
Members of the marine Synechococcus genus are ubiquitously distributed and are most abundant in coastal regions and mesotrophic open ocean surface waters (Partensky et al., 1999a; Zwirglmaier et al., 2008), whereas Prochlorococcus preferentially thrives in warm, stratified, oligotrophic tropical, and subtropical marine ...
What produces the world's oxygen?
oceanic planktonScientists estimate that 50-80% of the oxygen production on Earth comes from the ocean. The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize. One particular species, Prochlorococcus, is the smallest photosynthetic organism on Earth.
How many Phytoplanktons are there?
There are more than 20,000 species of phytoplankton distributed among eight major taxonomic groups. They range in size from less than 1 µm to greater than 100 µm. The distinct phytoplankton groups have different primary functions in the ecosystem.
How much 02 is created by the ocean?
50-80%At least half of Earth's oxygen comes from the ocean. Though they're invisible to the naked eye, they produce more oxygen than the largest redwoods. Scientists estimate that 50-80% of the oxygen production on Earth comes from the ocean.
What are two differences between Synechococcus and Prochlorococcus?
Members of the marine Synechococcus genus are ubiquitously distributed and are most abundant in coastal regions and mesotrophic open ocean surface waters (Partensky et al., 1999a; Zwirglmaier et al., 2008), whereas Prochlorococcus preferentially thrives in warm, stratified, oligotrophic tropical, and subtropical marine ...
Is Prochlorococcus a cyanobacterium?
The marine unicellular cyanobacterium Prochlorococcus is the most abundant photosynthetic organism on Earth. Members of this genus are classically thought to be adapted to high-oxygen and nutrient-poor ocean conditions, with a principle divergence between high-light and low-light ecotypes.
What are the two genera of picoplanktonic cyanobacteria?
Most species of picoplanktonic marine cyanobacteria currently identified belong to two genera, Synechococcus and Prochlorococcus. Together, these groups are thought to comprise 20–40% of chlorophyll biomass and carbon fixation in the oceans ( Partensky et al., 1999 ). Genomic analyses of Proc hlorococcus ( Dufresne et al., 2003, Rocap et al., 2003) and Synechococcus ( Palenik et al., 2003) have revealed an extensive array of information on N utilization by these important genera and provide an excellent example of how genomic analysis can yield insights into ecological capabilities. Examining their genetic capabilities, Synechococcus strain WH8102 can use NH 4+, NO 2−, NO 3−, urea, cyanate, amino acids and peptides; Prochlorococccus MIT9313 can use all except NO 3− and cyanate; Prochlorococccus MED4 only NH 4+, urea, cyanate and peptides; and Prochlorococccus SS120 only NH 4+ and amino acids ( Dufresne et al., 2003; Fuhrman, 2003; Palenik et al., 2003; Rocap et al., 2003 ). Virtually all isolated marine Synechococcus strains except Synechococcus sp. MIT9220, isolated from the equatorial Pacific, are capable of using NO 3− as an N source for growth ( Scanlan and West, 2002 ). Even the strain that can't use NO 3− as an N source can use NO 2−, NH 4+ and urea as N sources. It appears that during the evolution of Prochlorococcus, genes for NO 3− / NO 2− transport and reduction (NR and NiR) were lost while the genes for nitrite reductase were retained or reacquired in some cases and lost in others ( Dufresne et al., 2003; Garcia-Fernandez et al., 2004; Rocap et al., 2003 ).
What are the two chromophores of Synechococcus phycoerythrin?
These different clades of Synechococcus phycoerythrin are the result of variation in the two chromophores, that is, phycoerythrobilin (PEB) and phycourobilin (PUB), which attach to the light-harvesting pigment phycoery thrin ( Glazer, 1985 ).
What is the dominant community in marine cyanobacteria?
3.2.1 Prochlorococcus and Synechococcus. The dominant community in marine cyanobacteria mainly comprises Prochlorococcus, Synechococcus, and Trichodesmium sp. in the Indian Ocean, with each significantly playing a role in the marine ecosystem.
What is the Proportal database?
ProPortal ( http://proportal.mit.edu/) is an online database of genomic, metagenomic, and transcriptomic data for the marine cyanobacterium Prochlorococcus. Its objective is to provide a repository of cross-referenced data from the genome to the ecosystem. ProPortal holds the diversity of ecotypic variation within this microbial taxon, its sister group Synechococcus, and phage that infect them. Currently, this database stores genomes of 13 Prochlorococcus strains, 11 Synechococcus strains, and 28 cyanophage strains that infect these groups. Cyanobacterial and cyanophage orthologous gene clusters can be accessed by keyword-based search or through a genome browser. Users can identify up- and downregulated genes in response to environmental stress by using gene expression data for Prochlorococcus ecotypes MED4 and MIT9313. Also, the database includes transcriptome in synchronized cells grown on a 24-h light–dark cycle. Metagenomic sequences from Prochlorococcus, Synechococcus, and phage genomes help users to explore the differences between populations from diverse habitats ( Kelly et al., 2012 ).
What is a microalgae?
We use the term microalgae to cover a heterogeneous group of single-celled photosynthetic organisms, including photosynthetic eukaryotes and photosynthetic prokaryotes like Prochlorococcus and Synechococcus, which are of major global importance and considered as key players among phytoplanktonic organisms in oligotrophic oceanic areas. It would be vastly overambitious to attempt to cover the biotechnological potential of the entire aquatic photosynthetic world in one book chapter, so this review will address only the genomics and biotechnology of eukaryotic microalgae.
Which ecotype uses the N species?
It has been hypothesized that each Prochlorococcus ecotype uses the N species that is most prevalent at the light levels to which they are adapted; NH 4+ in the surface waters and NO 2− at depth ( Rocap et al., 2003 ). Synechococcus on the other hand has retained NR and so is able to bloom during NO 3− upwelling events ( Dufresne et al., 2003; Glover et al., 1988; Rocap et al., 2003) and this may contribute to its relative abundance in coastal systems. For example, Synechococcus is usually less abundant than Prochlorococcus in extremely oligotrophic environments, where NO 3− concentrations are generally below the limits of analytical detection, but has a broader global distribution ( Palenik et al., 2003; Scanlon and West, 2002). Prochlorococcus strains also appear less versatile in their ability to use DON than Synechococcus ( Palenik et al., 2003; Rocap et al., 2003 ). The Synechococcus genome also contains amino acid and oligopeptide transporters as well as cyanate transporters and cyanase (degradation enzyme) suggesting that these can also be used as N sources. In fact, Synechococcus strain WH8102 can grow in culture on cyanate as a sole N source although cyanate use in nature has not been characterized ( Palenik et al., 2003 ).
What is the diameter of a spherical coccus?
spherical (ovoid) ( coccus, e.g., Micrococcus sp., diameter of ∼0.2 μm, Prochlorococcus, diameter of ∼0.5 μm, Synechococcus sp., spheroid with the largest dimension on the order of 1 μm),
What is the name of the microbe that scatters light according to its size?
What is Prochlorococcus ? Take a syringe of seawater from almost anywhere in tropical or sub-tropical oceans and inject it into a flow cytometer. As the indigenous microbes pass through the focused laser beam, they will scatter light according to their size, and autofluoresce according to their pigments. The smallest cells that emit red chlorophyll fluorescence are Prochlorococcus ( Figure 1 ), and this is precisely how they were discovered 30 years ago. We now know that there are 100 million of these tiny powerhouses in each liter of seawater over vast ocean regions.
What is the name of the cyanobacterium that does photosynthesis?
Prochlorococcus is a cyanobacterium — a bacterium that does oxygenic photosynthesis — and its name is actually a historical misnomer. Prochlorococcus contains chlorophyll b, rather than the phycobilisomes that are typical of most other cyanobacteria.
What is it like to be a prochlorococcus cell?
What’s it like to be a Prochlorococcus cell? Life is simple and your world is dilute! Although you are surrounded by other Prochlorococcus cells, they are 100 body lengths away, and the atoms of trace metals you must acquire are 2–4 body lengths away. As the sun comes up you photosynthesize and grow. By late afternoon you begin to replicate your chromosome, and as night falls you are ready to divide into two daughter cells. You passively drift away from your sister and are tens of meters away within an hour and kilometers away within a week. Odds are that one of you will die within two days of being born, likely through phage infection or becoming a meal for a small protist. Thus, day in and day out the total number of Prochlorococcus cells stays roughly the same, because reproduction balances the losses.
What is the name of the messenger from the sea?
Figure 1 Prochlorococcus — a messenger from the sea.
What are the roles of phages in the cell cycle?
Furthermore, phage appear to help maintain diversity through their so-called ‘kill-the-winner’ infection dynamics. Finally, many of the phage that infect Prochlorococcus carry genes with homology to host metabolic genes — for example, those related to phosphorus acquisition or even photosynthesis — that they use to redirect host metabolism to their own ends. It appears that these genes can be swapped in and out of host genomes, evolving under different selective pressures whilst in the phage. Thus, phage can be an incubator for generating gene diversity and a shuttle service for moving genes around.
What are some examples of limiting factors in the ocean?
Take nitrogen, for example. The availability of nitrogen is an important limiting factor in the oceans; add nitrate to seawater and you can cause a phytoplankton bloom. Yet the earliest cultures of Prochlorococcus lacked the genes necessary to assimilate nitrate; they required reduced forms of nitrogen, such as ammonia or nitrite, and some could not even use nitrite. This was a sobering finding because the models of ocean productivity used to feed into global climate models assumed that all phytoplankton could use nitrate. Then along came Prochlorococcus, shattering the status quo. Eventually, however, we found some Prochlorococcus that could use nitrate, adding yet another layer to its diversity. Our challenge now is to figure out what selective pressures drove this diversification.
What is the smallest photosynthesis cell on Earth?
OK, so what’s so special about Prochlorococcus? Why all the fuss? It’s the smallest and most abundant photosynthetic cell on Earth. There are an estimated 3 x 10 27 of them in the global oceans, collectively weighing twice as much as all humans, and sporting a surface area 100 times that of the Earth. They constitute half of the chlorophyll over vast ocean ecosystems, single-handedly supplying significant amounts of organic carbon to the rest of the microbial food web. About the size of the wavelengths of light they absorb, they are extremely efficient photosynthetic machines, and their genomes represent one of the most streamlined blueprints for life. With a lower bound of 1,800 genes, they synthesize biomass using only solar energy, CO 2 and inorganic compounds. That’s minimal life. That’s impressive!
How do AMGs help with photosynthesis?
These photosynthesis-related AMG s play central roles in ensuring energy for viral reproduction, by sustaining host photosynthetic activity after the shutoff of host metabolism during their infection processes ( Clokie et al., 2006; Lindell et al., 2005; Mann, Cook, Millard, Bailey, & Clokie, 2003 ). Furthermore, to provide ATP and NADPH for viral genome replication, the pentose phosphate pathway is augmented while the Calvin cycle activity level decreases during viral infection ( Thompson, Zeng, & Chisholm, 2016; Thompson et al., 2011 ). Thus, marine Synechococcus and Prochlorococcus viruses maintain host photosynthetic activity and redirect carbon flux from the Calvin cycle to the pentose phosphate pathway, using AMGs after the shutoff of host metabolisms for efficient viral reproduction ( Clokie et al., 2006; Lindell et al., 2005; Sullivan et al., 2006; Thompson et al., 2011 ), with the exception of a few cyanoviruses showing a short latent period ( Sullivan et al., 2010, 2006 ). As reflecting these genomic features, the gene expression of cyanoviruses reached peak levels linked to the host's photosynthetic activity, when the ATP level is the highest ( Welkie et al., 2019 ), in the afternoon/dusk. This is followed by an increase in viral DNA in the free virions during the night ( Aylward et al., 2017; Liu, Liu, Chen, Zhan, & Zeng, 2019; Yoshida et al., 2018 ). Furthermore, cyanoviruses are known to show light-dependent adsorption ( Cséke & Farkas, 1979; Jia, Shan, Millard, Clokie, & Mann, 2010; Kao, Green, Stein, & Golden, 2005; Liu, Liu, et al., 2019) due to conformational changes in host receptors and/or viral tail fibers that can only be induced in the light ( Jia et al., 2010 ). The other cyanoviruses with distinct genomic features (e.g., bloom-forming cyanobacterial viruses) show similar diel periodicity to that of marine cyanoviruses ( Kimura et al., 2012; Morimoto et al., 2019; Morimoto, Kimura, Sako, & Yoshida, 2018 ). Thus, cyanoviruses form daily biological rhythms linked with light-utilizing host lifestyle.
What is the size of phycobilisomes?
The phycobilisomes, used by most cyanobacteria as light-harvesting structures, can be distinguished in electron microscopic preparations as rows of particles ∼50 nm in diameter on the cytoplasmatic side of the thylakoids ( Figure 4 (e) ).
How big are cyanobacteria?
Cyanobacterial cells range in width between 0.5 μm ( e.g., Prochlorococcus) and 50–100 μm (e.g., some ‘ Chroococcus ’ and some Oscillatoria ); the modal size of the described species is significantly larger than that of most other bacteria and archaea (∼4 μm). In unicellular and colonial forms, cells may be spherical, bacilloid, or fusiform, and some strains present considerable pleiomorphism. Cells of filamentous cyanobacteria may range from discoid to barrel-shaped, and the trichomes often attain lengths on the order of millimeters. The filamentous genus Starria has triradiate cells. Several types of cells may be present in morphologically complex cyanobacteria. The cells of most cyanobacteria are surrounded by a more or less-defined exopolysaccharide investment. In some species this may form a distinct, structured capsule or sheath, where the steric constrictions to cell growth imposed by the presence of mechanically strong capsules or sheaths may even dictate cellular shape ( Figure 3 (p)). Several ultrastructural features are typical for cyanobacteria. The cell envelope is of a Gram-negative type but may attain a considerable thickness in the peptidoglycan layer (from several to 200 nm). Pores of different sizes, whether or not orderly arranged, perforate the cyanobacterial cell wall. Pore pits may allow close contact of the cytoplasmatic membrane with the lipopolysaccharide outer membrane. The photosynthetic machinery of cyanobacteria resides on intracellular membranes (thylakoids). Each thylakoid consists of a double-unit membrane enclosing an intrathylakoidal space (Figure 4 (d) ). Thylakoids may be arranged parallel to the cell membrane, radially, or in small disorderly stacks, depending on species ( Figure 4 ). They may be single or stacked, usually depending on illumination conditions. Gloeobacter has no thylakoids and the photosynthetic apparatus resides in the plasma membrane. The phycobilisomes, used by most cyanobacteria as light-harvesting structures, can be distinguished in electron microscopic preparations as rows of particles ∼50 nm in diameter on the cytoplasmatic side of the thylakoids ( Figure 4 (e) ). These are obviously absent from chlorophyll b -containing, phycobiliprotein-lacking species ( Prochlorococcus, Prochloron, and Prochlorothrix ). A central electron-clear region in the cell, the nucleoplasm, or the centroplasm, hosts the cellular DNA. Several intracellular nonmembrane-bound granules typically correspond to polymeric reserve materials, such as glycogen (polyglucose, usually present in the intrathylakoidal space), polyphosphate, poly-β-hydroxyalkanoates, and lipid droplets found in the cytoplasm proper, which are also common in other bacteria ( Figure 4 ). Cyanophycin (multi- l -arginyl-poly ( l-aspartic acid)) is a cytoplasmatic, exclusively cyanobacterial nitrogen reserve polymer. Carboxysomes (or polyhedral bodies) are commonly seen as membrane-bound intracellular inclusions, and they consist of accumulations of the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO), responsible for the initial carboxylation step in the Calvin cycle (see ‘Dark reactions of photosynthesis: carbon fixation and uptake’), bound by a proteinaceous, viral-capside-like case (Figure 4 (e)). Gas vesicles are air-filled, cylindrical proteinaceous structures present in many planktonic species and in the dispersal stages of benthic forms; they provide buoyancy to the organisms. A large variety of ultrastructural inclusions of restricted occurrence are also known from particular species or strains.
Which bacteria uses chlorophyll a and b instead of phycobilisomes?
Prochlorococcus. Prochlorococcus uses chlorophyll a and b instead of phycobilisomes [67] and has a PSII/PSI ratio that is significantly higher than other cyanobacteria [137,219,220], making its photosynthetic machinery rather more like that of green chloroplasts than other cyanobacteria [73].
What is the shape of a cell in cyanobacteria?
Cells of filamentous cyanobacteria may range from discoid to barrel-shaped, and the trichomes often attain lengths on the order of millimeters.
Where does the photosynthetic machinery of cyanobacteria reside?
The photosynthetic machinery of cyanobacteria resides on intracellular membranes (thylakoids). Each thylakoid consists of a double-unit membrane enclosing an intrathylakoidal space (Figure 4 (d) ). Thylakoids may be arranged parallel to the cell membrane, radially, or in small disorderly stacks, depending on species ( Figure 4 ).
What is the tail hub of epsilon15?
For epsilon15 phage bound to its Salmonella host ( Chang et al., 2010 ), a unique structure was observed—a tubular extension of the tail hub spanning the outer cell wall, the periplasm, and the cell membrane. It is tempting to speculate that this structure is the guide for DNA injection into the cell.
Penny Chisholm has spent decades revealing the secrets of the marine microbe Prochlorococcus
Penny Chisholm has had a 35-year love affair—with a microbe. For her, it's been the perfect partner—elusive during courting, a source of intellectual fulfillment, and still full of mystery decades after their introduction during an ocean cruise.
A microbe's vital stats
Chisholm says that as a woman of her times, she went to college in the 1960s mainly "to find a husband." Nevertheless, as an undergrad, she explored the chemistry of lakes, and—after a professor pushed her—decided to pursue a Ph.D.
The sea's invisible pasture
Drawing on ocean and marine microbe data collected by Massachusetts Institute of Technology researchers, this model depicts the most dominant types of phytoplankton in the world's oceans, with Prochlorococcus ruling much of the globe and bigger diatoms dominating nearer the poles.
About the author
Liz is a senior correspondent covering many aspects of biology for Science.
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Abstract
Prochlorococcus is the numerically dominant photosynthetic organism throughout much of the world’s oceans, yet little is known about the ecology and genetic diversity of populations inhabiting tropical waters.
Introduction
The unicellular cyanobacterium Prochlorococcus has a profound impact on marine carbon cycling because of its high abundance in tropical and subtropical oceans ( Partensky et al., 1999 ).
Materials and methods
Samples for single-cell genomics, qPCR and flow cytometry were collected from four depths (15, 45, 100 and 150 m) at eight locations in April 2007 during the CMORE-BULA cruise from Fiji to Hawaii ( Hewson et al., 2009 ).
Results and discussion
To examine the phylogenetic diversity and genetic makeup of Prochlorococcus at a site in the equatorial Pacific, we flow sorted hundreds of individual Prochlorococcus cells from a 15 m sample at station 2 along the CMORE-BULA transect ( Figure 1a) and subjected them to whole-genome amplification.
Acknowledgements
We thank Doug Rusch and Nyree West for providing sequence data, and C Mark Moore and Malcolm Woodward for providing nutrient data for the Atlantic Meridional Transect 17. Greg Kettler assisted with identifying genomic islands in Prochlorococcus MIT9202.
Author information
Rex R Malmstrom and Sébastien Rodrigue: These authors contributed equally to this work.
Additional information
Supplementary Information accompanies the paper on The ISME Journal website
