Tag Archives: genetics

Bacteria Can Transfer Genes to Other Bacteria

Microbiologists of the 1950’s did not appreciate the stunning extent to which bacteria swap genes… In 1959 Japanese hospitals experience outbreaks of multidrug-resistant bacterial dysentery. The shigella bacteria, which caused the outbreaks, were shrugging off four different classes of previously effective antibiotics: sulfonamides, streptomycins, chloramphenicols, and tetracyclines… In fact, the Japanese researches found it quite easy to transfer multidrug resistance from E. coli to shingella and back again simply by mixing resistant and susceptible strains together in a test tube.

Young Geneticists Making a Difference

After an early phase of discouragement, Johannes Krause was able to follow his long interest in genetics and even link it to another passion of his, paleoanthropology. Krause initially chose to study biochemistry at the University of Leipzig. But “I was almost about to quit” at the frustration of learning much more about basic chemistry than biology, he says. However, in the third year of his bachelor’s degree, he took some specialised courses in genetics as an Erasmus student at the University College Cork in Ireland that revived his interest for the field.

Back in Leipzig, a summer internship on comparing gene expression between humans and chimpanzees at the Max Planck Institute for Evolutionary Anthropology sparked Krause’s enthusiasm for good. He stayed on in the lab as a research assistant for 2 years before graduating in 2005. While there, Krause helped develop a biological method to read large pieces of ancient DNA, sequence the complete mitochondrial genome of the mammoth from fossil samples, and place it in the context of evolution. “Johannes has great technical skill and the judgment to distinguish a good project from a blind alley. Like few others he can see the interesting pattern that can hide in sometimes confusing data,” Svante PÃ¤Ã¤bo, his principal investigator, writes in an e-mail to Science Careers.

Amazing Science: Retroviruses

One of the great things about writing this blog is I find myself more focused on reading about interesting science. Retroviruses are very interesting and frankly amazing. Darwin’s Surprise by Michael Specter, The New Yorker:

A retrovirus stores its genetic information in a single-stranded molecule of RNA, instead of the more common double-stranded DNA. When it infects a cell, the virus deploys a special enzyme, called reverse transcriptase, that enables it to copy itself and then paste its own genes into the new cell’s DNA. It then becomes part of that cell forever; when the cell divides, the virus goes with it. Scientists have long suspected that if a retrovirus happens to infect a human sperm cell or egg, which is rare, and if that embryo survives – which is rarer still – the retrovirus could take its place in the blueprint of our species, passed from mother to child, and from one generation to the next, much like a gene for eye color or asthma.

When the sequence of the human genome was fully mapped, in 2003, researchers also discovered something they had not anticipated: our bodies are littered with the shards of such retroviruses, fragments of the chemical code from which all genetic material is made. It takes less than two per cent of our genome to create all the proteins necessary for us to live. Eight per cent, however, is composed of broken and disabled retroviruses, which, millions of years ago, managed to embed themselves in the DNA of our ancestors. They are called endogenous retroviruses, because once they infect the DNA of a species they become part of that species. One by one, though, after molecular battles that raged for thousands of generations, they have been defeated by evolution. Like dinosaur bones, these viral fragments are fossils. Instead of having been buried in sand, they reside within each of us, carrying a record that goes back millions of years. Because they no longer seem to serve a purpose or cause harm, these remnants have often been referred to as “junk DNA.” Many still manage to generate proteins, but scientists have never found one that functions properly in humans or that could make us sick.

How amazing is that? I mean really think about it: it is incredible. The whole article is great. Related: Old Viruses Resurrected Through DNA – DNA for once species found in another species’ Genes – New Understanding of Human DNA – Retrovirus overview (Tulane) – Cancer-Killing Virus
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One Species’ Genome Discovered Inside Another’s

Video describing genome inside genome Watch video of Professor Werren describing the genome-in-a-genome at the University of Rochester.

More incredible gene research. Scientists at the University of Rochester and the J. Craig Venter Institute have discovered a copy of the genome of a bacterial parasite residing inside the genome of its host species. The research, reported in today’s Science, also shows that lateral gene transfer—the movement of genes between unrelated species—may happen much more frequently between bacteria and multicellular organisms than scientists previously believed, posing dramatic implications for evolution.

Such large-scale heritable gene transfers may allow species to acquire new genes and functions extremely quickly, says Jack Werren, a principle investigator of the study. If such genes provide new abilities in species that cause or transmit disease, they could provide new targets for fighting these diseases.

The results also have serious repercussions for genome-sequencing projects. Bacterial DNA is routinely discarded when scientists are assembling invertebrate genomes, yet these genes may very well be part of the organism’s genome, and might even be responsible for functioning traits.

“This study establishes the widespread occurrence and high frequency of a process that we would have dismissed as science fiction until just a few years ago,” says W. Ford Doolittle, Canada Research Chair in Comparative Microbial Genomics at Dalhousie University, who is not connected to the study. “This is stunning evidence for increased frequency of gene transfer.”

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