Prochlorococcus marinus: Difference between revisions

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Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.


==Pathology==
 
How does this organism cause disease?  Human, animal, plant hosts?  Virulence factors, as well as patient symptoms.


==Application to Biotechnology==
==Application to Biotechnology==

Revision as of 18:45, 29 August 2007

A Microbial Biorealm page on the genus Prochlorococcus marinus

Classification

P. marinus Image used with permission of http://www.genoscope.cns.fr

Higher order taxa

Bacteria (Domain); Cyanobacteria (Phylum); No Class Listed; Prochlorales (Order); Prochlorococcaceae (Family); Prochlorococcus (Genus)

NCBI: Taxonomy

Species

Prochlorococcus marinus

NCBI: Complete strain MIT9313 genome

Description and significance

Prochlorococcus marinus was fist discovered and classified by Sallie W. Chrisholm in 1988.

Prochlorococcus marinus is the dominate photosynthetic organism in the ocean. It accounts for up to 60% of the ocean’s chlorophyll in many regions such as the subtropical Pacific and is vastly numerous, often occurring at 10^5 cells/ml, abundant over the range of 40 °N to 40 °S The primary production and carbon sequestering capabilities in the open, oligotrophic, ocean are performed by these tinniest of cyanobacteria. P.marinus ranges in size from .6 to .eight um and have genomes of range l.6 to 2.6 Mbp. Most strains however, have genomes sized around 1.7 or 2.4 Mbp. Many experts understand such a condensed genome to be representative of the minimal genomic requirements for photosynthetic microbes.

P. marinus utilizes divinyl chlorophyll b and a2 as its light harvesting photochemicals. Its identification is still greatly in flux as many potential systems (subspecies, ecotypes, multiple gene sequence comparisons…) of classification have merit and support for varying taxonomy. The primary and predominate distinction between types of Phroclorococcus marinus is the ratio of their chl b to chl a2. Strains fall into 2 categories: High B/A isolates that have adapted to low iridescence light levels and low B/A isolates which flourish under high iridescences of light.


Genome structure

Relationships between Prochlorococcus and other cyanobacteria inferred using 16S-23S rRNA and the internal transcribed spacer (ITS) region between 16S-23S rRNA. Used with permision of Gabrielle Rocap, University of Washington

The strains of P.marinus all have circular DNA. Genome size ranges from l.6 to 2.7Mbp. Most strains however, have genomes sized around 1.7 or 2.4 Mbp. Many strains of Prochlorococcus have been sequenced. Its small genome and abundance in the accessible open ocean allow many studies to be done on its genome.

All isolated strains are either low light adapted or high light adapted which corresponds to a high chl b to chl a2 ratio and a low ratio, respectively. The high B/A ratio, low light strains and the low B/A ratio, high light strains have do not have distinct genome sizes: all prochlorococcus have ~1.7 or 2.4 Mbp but this division does not always fall along the niche divide. The high light clade can be fairly divided into to subgroups based on size of genome. Members of the high light clade are very similar genetically. The divisions are less clear and diversity is more multifaceted in the low light clade. MED4 is often used as a reperesentitive high light strain with l.66 Mbp, 1,716 coding genes and a 30.8 G+C%. MIT9313 is most cited low light strain with 2.41 Mbp, 2,275 coding genes and a 50.6 G+C%.

The 16S rDNA sequences of the Prochlorococcus ecotypes correlate with their physiology. Strains of the low-B/A ecotype are phylogenetically very closely related (99% identity in 16SrDNA sequence). Strains of the high-B/A ecotype have a lower degree of identity in their 16S rDNA sequence (97 to98%) High-B/A Prochlorococcus strains also have a higher degree of sequence identity to Synechococcus ( a member of the same phylum and Prochlorococcus’ closest relative) than the low-B/A ecotype. Some high-B/A Prochlorococcusstrains and marine cluster A Synechococcus strains are not well resolved using 16S rDNA sequences. Thus, the sequences of the internal transcribed spacer (ITS) region between 16S-23S rRNA is utilized to further characterize these isolates.

Genomic data supports the evolutionary model describing a common ancestor of Cyanobacteria leading to organisms with differing light harvesting methods(the major difference between Prochlorococcus and Synechococcus) From there, high light and low light clades evolved by a mix of riding themselves of unnecessary genes, and adapting to their niches.In both MED4 and MIT9313 over 30% of the genes have hypothetical or unknown function.

Cell structure and metabolism

P. marinus Strain SS120 Structure and Metabolism. Used with premision from Alexis Dufresne of Centre National de la Recherche Scientifique et Universite´ Paris

All Prochlorococcus utilize divinyl chlorophyll b and a2 in their light harvesting. All strains have shown a particularly active response to blue light over other wavelengths.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.


Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

1. Chisholm, S. W. et al. A novel free-living prochlorophyte abundant in the oceanic euphotic zone. Nature 334, 340–343 (1988): [1]

2. Rocap, G et al. Genome divergence in two Prochlorococcus ecotypes reflects oceanic niche differentiation Nature 424: 1042-1047. (2003) [2]

3. Gabrielle Rocap 2000 Genentic Diverstiy in the Marien Cyano Bacteria Prochlorococcus and Synechococcus. Ph. Thesis, Massachusetts Institute of Technology

4.Dufresne, A. et all. Genome sequence of the cyanobacterium Prochlorococcus marinus SS120, a nearly minimal oxyphototrophic genome. PNAS August 19, 2003 vol. 100 no. 17 p10020–10025: [3]

5. Chisholm, S.W. et al. Genome-Wide Analysis of Light Sensing in Prochlorococcus JOURNAL OF BACTERIOLOGY, Nov. 2006, p. 7796–7806




Edited by Stephen Hubbard, student of Rachel Larsen [Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.