Fremyella diplosiphon
Classification
Domain: Prokaryota
Kingdom: Eubacteria
Group: Terrabacteria
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Nostocales
Family: Rivulariaceae
Genus: Microchaete
Species: Diplosiphon
Species
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NCBI: [1] |
Fremyella diplosiphon
Description and Significance
Fremyella diplosiphon is a filamentous chromatically adapting cyanobacterium (1) and was first isolated from a dried pool in Zacapa, Guatemala in 1939 by Paul Standley (2). Colonies can appear blue-green or red, and cells can appear as thicker brick-shaped filaments or as short and rounded under the microscope, depending on the conditions. It has been studied intensely for the past 40 years for its process known as "proteome remodeling" (3), where the organism adjusts the proteins produced in response to a nutrient limitation (light).
Fremyella diplosiphon is most well known for its chromatic adapting phototropism, the ability to adjust photosynthetic receptors in the presence or absence of different colors of light, and due to this ability, this species has been used to study the biochemical and physiological processes that allow microbes to sense and respond to their environment. Fremyella diplosiphon is capable of adjusting its photosynthetic antennae to harvest different colored light depending on the conditions, making it a key model organism in studying physiological response. Not only is Fremyella diplosiphon an excellent model for phototropism, but response to light differences are also very important in the metabolic process of photosynthesis, which is the necessary anchor of any ecosystem, making Fremyella diplosiphon a key member of its ecological community. Its ecological importance as a photosynthetic Cyanobacterium can also offer insight into the early evolution of ecosystems, as well as the evolution early life on Earth. The physiological processes that Fremyella diplosiphon possesses could also be utilized as in the development of bioenergy (3).
Genome Structure
Fremyella diplosiphon has one of the largest genomes of bacteria, containing around 9.9 million base pairs in a single circular chromosome. The complete genome sequence can be found at https://www.ncbi.nlm.nih.gov/genome/browse/. Because Fremyella diplosiphon is studied mostly for its proteome remodeling in its physiological response to light, much of the knowledge regarding its genome revolves around the proteins that participate in its light adaptations. One study found that F. diplosiphon's chromosome has a very high resistance to most nucleases, and is therefore able to resist cleavage to its chromosome (8).
Fremyella diplosiphon manipulates the composition of its phycobilisome, the light harvesting organelle, by activating and repressing different operons. The cpeBA operon and the cpeCD operon have been identified as coding for green-light harvesting proteins on the phycobilisome (4). Quantification of the various transcripts produced by F. diplosiphon in both red and green light have shown that, while some transcripts are conserved, many transcripts are expressed very highly in one color light over the other (5). IT has been found that one main light-responsive sensor kinase called RcaE may be responsible for the responses to different light pigments (6). Some genes in F. diplosiphon are found to be conserved across many Cyanobacteria but many of the genes responsible for its complementary chromatic adaptation are specific to this species.
Cell Structure, Metabolism and Life Cycle
Interesting features of cell structure; how it gains energy; what important molecules it produces.
