April 15, 2019
Bacteria are sharing info amongst themselves. I wonder what they're so "chatty" about. Maybe scientists can shed some like on that for us.
Learn about this and more interesting stories from the scientific community in today's issue.
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*-- Bacteria in the human body are sharing genes, even across tissue boundaries --*
Microbes in the human body are swapping genes with one another, according to a new study. Some bacteria genes can even travel across tissue barriers without their microbial hosts.
Scientists were able to identify instances of "horizontal gene transfer" using a new molecular data-mining method.
"Horizontal gene transfer is a major force of exchange of genetic information on Earth," Gustavo Caetano-Anolles, a professor of crop sciences and genomic biology at the University of Illinois, said in a news release. "These exchanges allow microorganisms to adapt and thrive, but they are likely also important for human health. There are some bacteria that cannot live outside our bodies and some without which we cannot live."
Because horizontal gene transfer has enabled the proliferation of antibiotic resistance among pathogens, an improved understanding of the phenomenon has public health implications.
For the new study, scientists constructed family trees of the thousands of microbes that colonize the human body. Powerful computers and sophisticated algorithms helped scientists analyze the relationships among the different trees and differentiated between genes that were shared via inheritance and genes that were acquired via horizontal gene transfer.
"Most current methods for determining horizontal gene transfer compare DNA features or statistical similarity between genomes to identify foreign genes," said Arshan Nasir, researcher at COMSATS University in Pakistan. "This works fairly well for relatively recent gene transfers, but often fails to identify transfer events that occurred millions or billions of years ago."
The new analysis method allowed Caetano-Anolles and Nasir to overcome this problem. Their work -- detailed this week in the journal Scientific Reports -- showed microbes in the human body exchange genes very freely.
"The horizontal exchange between microbes in our bodies is about 30 percent higher than what you'll find on the rest of the planet," Caetano-Anolles said. "This implies that our bodies provide a niche that is unique and facilitates innovation at the microbe level."
Scientists determined the majority of gene transfer activity, 60 percent, occurs between microbes living in different parts of the body -- microbes in gut sharing genes with bacteria living in the blood, for example.
"Some of these could be very old gene transfer events that happened before the microbes colonized the human body," Nasir said. "It also could be that some bacteria colonize different human body sites at different time points in an individual's lifespan. The others could be the result of the transfer of bacterial DNA from one site to another, perhaps through the blood. We need further experimental evidence to test this tantalizing possibility."
By teasing out which portions of microbial genomes were inherited and which were transferred, scientists can gain new insights into the evolutionary histories of different bacteria strains, as well as their evolutionary relationships with the human body.
*-- Scientists prevent supercooled water from freezing --*
Scientists have discovered a way to keep water from freezing, even at extremely cold temperatures.
When water freezes, its molecules organize into a lattice pattern to form ice crystals. The molecules of liquid water remain disorganized, free-floating, allowing water to flow.
In the lab, scientists at the University of Zurich kept supercooled water in liquid form by trapping it inside a new kind of synthesized lipid.
Lipids are fat molecules. For the study, scientists developed a synthetic fat molecule called lipidic mesophase. The lipids self-assemble to form membranes that look and behave like natural fat molecules.
When the membranes aggregate, they form interconnected channels measuring less than a nanometer wide. The shape of the membrane assemblage depends on the temperature and water content.
In experiments, scientists determined water trapped inside the membrane's tiny channels can't freeze, even at subzero temperatures.
For one test, scientists used liquid helium to cool lipidic mesophase modified with monoacylglycerol to negative 263 degrees Celsius -- 10 degrees away from absolute zero. At the extreme subzero temp, the water became "glassy" but did not freeze.
The shape and the size of the channels formed by the self-assembling lipids depends on the water content, which is hard to control.
"What makes developing these lipids so tricky is their synthesis and purification," Ehud Landau, professor of chemistry at the University of Zurich, said in a news release.
Lipid molecules have one hydrophobic component, which repels water, and one hydrophilic component, which attracts water.
"This makes them extremely difficult to work with," Landau said.
To create the new class of lipids for their experiments, researchers modeled the synthetic fat molecules after the membranes of bacteria that can survive extremely cold temperatures.
"The novelty of our lipids is the introduction of highly strained three-membered rings into specific positions within the hydrophobic parts of the molecules," said Landau. "These enable the necessary curvature to produce such tiny water channels and prevent lipids to crystallize."
Scientists detailed their feat in the journal Nature Nanotechnology.
Authors of the new study expect their research to be utilized by other scientists. The lipids can be used to isolate, preserve and study large biomolecules, like proteins, in a membrane-like environment.
"Our research is paving the way for future projects to determine how proteins might be preserved in their original form and interact with lipid membranes at very low temperatures," said Zurich professor Raffaele Mezzenga.