Water Pollution: a cyanobacterium dangerous often found in lakes "lighter" genes acting estrogen on fish.
algal blooms could not only be toxic but have estrogenic effects according to researchers.
runoff of agricultural fertilizers can fuel blooms toxic algae that can be fatal to pets and livestock. And as if that were not sufficiently alarming new research scientists are proposing for the first time that the blooms could also disturb the breeding grounds for aquatic life by mimicking the hormone estrogen. 
To date, most studies on Microcystis aeruginosa, a cyanobacterium most often implicated in algal blooms (blooms), have concentrated on the 80 toxins microcystins by Ted Henry, a toxicologist at the University of Plymouth in Great Britain. The toxins can cause severe internal bleeding and liver damage in mammals and fish. 
To find these genes, a group of scientists expounded fry Danio rerio has the microcystin-LR toxin microcystin most toxic, and exposed another group of fry to cells of Microcystis dried and reconstituted, which are more convenient to handle than live cells in experiments. They then measured the intensity of the reactions in the genes of fish. As might be expected, microcystin-LR increases the responses of genes in the liver to detoxify. But the big surprise was to find that fish exposed to Microcystis cells were 19 to 100 times more feedback in the vitellogenin gene in fish exposed compared with others.
Stimulated by estrogen, vitellogenin is a protein that is produced by mature female fish for its egg yolks. Usually when the fry produce vitellogenin, scientists assume that it is a sign of estrogen pollution in the environment. Scientists usually attribute the pollution source as human or animal hormones from sewage or agricultural runoff. Mr. Henry said that the estrogen in the environment may affect reproduction in fish and possibly a decline in population in the long term.
Mr. Henry and his team concluded that the cause of the production of vitellogenin was not the toxin microcystin, because the only fish exposed to the toxin showed no change in gene expression. Charles Tyler, a toxicologist at the University of Exeter in Britain, said that the microbes could produce chemicals called phytoestrogens mimics hormones, like plants and fungi can. But Mr. Tyler wondered how far the reaction Microcystis causes estrogen in fish in the field, because the study employed cells and reconstituted dried and not live.
By cons, Allen Place, a biochemist at the Center for Environmental Science, University of Maryland, believes the study will consider other researchers and will focus their attention on molecules rather than just natural human pollution as a source of estrogen in the environment .
Personal note: may well be that this source "natural" estrogen in the environment is produced by algae "natural", but it must be remembered that the algae blooms in our waterways are often caused by pollution that it is far from "natural"!
Toxic Algae May
Add To Estrogen Water Pollution
Pollution: A hazardous cyanobacterium common in lakes turns on estrogen-related genes in fish
Janet Pelley
ESTROGEN BLOOMS? Researchers think that Microcystis is not only toxic but estrogenic.
Fertilizer runoff from farms can feed blooms of toxic cyanobacteria, which are deadly to pets and livestock. As if that weren't enough to worry about, new research suggests for the first time that the blooms also could disrupt reproduction in aquatic wildlife through estrogenic effects (Environ. Sci. Technol., DOI: 10.1021/es103538b).
Until now, most studies of Microcystis aeruginosa, the most common bloom-forming cyanobacterium, have focused on the bacterium's 80 or so microcystin toxins, says Ted Henry, an ecotoxicologist at the University of Plymouth, in the U.K. The toxins can cause massive internal bleeding and liver damage in mammals and fish. Henry, Emily Rogers of the University of Tennessee, Knoxville, and their colleagues stumbled on the estrogenic actions when they were looking for genes that turn on when fish encounter Microcystis. They hoped that these genes could serve as biomarkers for bloom events in lakes when biologists observe fish die offs. "We wanted to develop a short list of genes that would determine whether a fish had been exposed to Microcystis or not," Henry says.
To find the genes, the scientists treated one group of larval zebrafish (Danio rerio) with microcystin-LR, the most toxic microcystin toxin, and treated another group with dried and reconstituted Microcystis cells, which are more convenient than live cells to use in experiments. They then measured gene expression levels in the fish.
Not surprisingly, the microcystin-LR boosted the expression of genes that the liver uses to detoxify itself. But the big surprise was that fish exposed to Microcystis cells had 19 to 100 times greater expression levels of the vitellogenin gene than unexposed fish did.
Kick-started by estrogen, vitellogenin is a protein that mature female fish produce for their egg yolks. Usually, when larval fish produce vitellogenin, scientists take it as a sign of estrogen pollution in the environment. Scientists often attribute this pollution to human or animal hormones released by sewage and farm runoff. Henry says that estrogens in the environment can disrupt fish reproduction and possibly lead to population decline.
Henry and his team concluded that the cause of vitellogenin production wasn't the microcystin toxin, because fish exposed to the toxin alone showed no change in the gene's expression. Charles Tyler, an ecotoxicologist at the University of Exeter, in the U.K., says that the microbes might release estrogen-like chemicals called phytoestrogens, just as plants and fungi do. But Tyler wonders to what extent Microcystis induces an estrogenic response in fish in the wild, because the study used dried and reconstituted cells, not live ones.
Still, Allen Place, a biochemist of the University of Maryland's Center for Environmental Science, thinks that the study will make other researchers pause and consider naturally occurring molecules, rather than only manmade pollution, as the source of estrogens in the environment.
Chemical & Engineering News
Link:
http://pubs.acs.org/cen/news/89/i07/8907scene1.html
Maybe this newly discovered source of estrogen in our lakes is "natural" because it comes from algae, but one must remember that often, algae blooms are caused by "unnatural" pollution!
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