Week in Review: February 22–26

Questions about how E. coli evolves; spermatids in a dish; fighting bacteria with virus-like molecule; what drives metastasis; antibodies fight Ebola in monkeys

By | February 26, 2016

Long-time evolution experiment questioned

WIKIMEDIA; BRIAN BAER, NEERJA HAJELAFor more than 30 years, Richard Lenski and his team at Michigan State University have been propagating the same 12 cultures of E. coli, transferring the cells to new media every day. The experiment has allowed the researchers to see how the bacteria evolve, and in 2008 they published results suggesting that some of the cultures had begun to use citrate as a carbon source. But it took 15 years for such citrate-eating microbes to arise—a delay Lenski and colleagues attributed to “historical contingency,” or the slow accumulation of mutations required for the adaptation.

This month (February 1), however, researchers publishing in the Journal of Bacteriology suggested that perhaps the exciting development was simply a result of the experimental conditions, and showed that making certain tweaks to the culture environment could elicit such citrate-eating mutants much sooner than in Lenski’s long-running study. “We’re showing that there’s a simple genetic explanation for the acquisition of citrate mutants in the long-term evolution experiments—that there’s no historical contingency required,” the University of Idaho’s Scott Minnich, a fellow of the Seattle-based nonprofit Discovery Institute, told The Scientist.

“What the new experiment has told us is [that] actually these phenotypes can evolve much more readily than we initially thought,” said Rees Kassen, who was not involved in the research. “To me [this] suggests that if we’re going to make inferences about a species itself evolves over long periods of time, we have to be very careful about the ecology of how we do our experiments.”

Lab-made sperm on the horizon?

WIKIMEDIA, L.A. DAWSONResearchers in China have created sperm precursors called round spermatids in vitro using mouse embryonic cells, possibly paving the way for stem cell–based treatments for infertility, according to a study published this week (February 25) in Cell Stem Cell

“It’s a good piece of work that really sets the stage for so many different fields by putting together pieces necessary to de novo derive germ cells and use them for reproductive purposes,” said Brian Hermann, a reproductive biologist and stem cell researcher at the University of Texas, San Antonio, who was not involved in the work. “The fact they were able to complete meiosis in vitro from germ cells derived from pluripotent stem cells is really a major advance.”

Mimicking a virus to fight bacteria

WIKIMEDIA, CDC/MIKE MILLERA molecule that mimics murine norovirus can protect antibiotic-treated mice from opportunistic, pathogenic bacteria, such as Vancomycin-resistant Enterococcus faecium (VRE), according to a study published this week (February 24) in Science Translational Medicine.

“They showed not only that this [norovirus] is protective against VRE—which is a very serious, hospital-acquired pathogen—but that they could also mimic the effect of the virus using a drug,” said Kenneth Cadwell, an assistant professor of microbiology at New York University’s Skirball Institute of Biomolecular Medicine who was not involved in the research. “That’s pretty amazing.”

Immune changes, not mutations, tied to metastasis

WIKIMEDIA, PATHOWhile genetic mutations are known to influence a cancer’s ability to progress, they do not appear to drive metastasis, according to a study of hundreds of colorectal cancer patients published in Science Translational Medicine this week (February 24). Rather, the researchers found several immune-related changes, including decreased abundance of cytotoxic T cells, in metastatic tumors, and mice with depleted levels of these lymphocytes had faster-growing tumors.

“It certainly confirms what this group and others have shown previously—that the adaptive immune response seems to be very important,” Edgar Engleman, who researches immunoncology at Stanford University but was not part of this study, told The Scientist. “[It also] takes away a fair amount of air over the importance of driver mutations.”

Antibody treats Ebola in macaques

FLICKR, NIAIDTwo monoclonal antibodies produced by a survivor of the 1995 Ebola outbreak in the Democratic Republic of Congo protected macaques from lethal doses of the virus, according to a study published this week (February 25) in Science. One of the antibodies was even effective up to five days after infection.

“There’s been a lot of activity in the past year isolating monoclonal antibodies from human subjects,” said James Crowe, an immunologist at Vanderbilt University in Nashville. “Most of the antibodies that have been tested in the past have allowed virus breakthrough.”

Other news in life science:

Genome Digest
A round-up of recent discoveries in genomics

FDA Head Confirmed
The US Senate approves the Obama administration’s nominee, Robert Califf, as the next commissioner of the Food and Drug Administration.

No Strong Zika-GBS Link in Pacific Islands
Past outbreaks of the viral infection did not result in an increase in Guillain-Barré syndrome among children in the Pacific, according to a study; plus, more sexually transmitted Zika cases reported

iPSCs and Cancer Risk
Reprogramming adult human cells into stem cells in vitro does not generate harmful mutations, scientists report.

Author Nets Seven Retractions
Biochemical Pharmacology pulls papers coauthored by a scientist whose work has been under investigation at MD Anderson Cancer Center.

Insulin-Producing Mini Stomachs
Scientists grow gastric organs in vitro that can restore insulin production when transplanted into mice.

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