Monthly Archives: May 2014

Public interest in climate change unshaken by scandal, but unstirred by science (Environ. Res. Lett.)

Public interest in climate change

Princeton University and University of Oxford researchers found that negative media reports seem to have only a passing effect on public opinion, but that positive stories don’t appear to possess much staying power, either. Measured by how often people worldwide scour the Internet for information related to climate change, overall public interest in the topic has steadily waned since 2007. To gauge public interest, the researchers used Google Trends to document the Internet search-engine activity for “global warming” (blue line) and “climate change” (red line) from 2004 to 2013. They examined activity both globally (top) and in the United States (bottom). The numbers on the left indicate how often people looked up each term based on its percentage of the maximum search volume at any given point in time. (Image courtesy of William Anderegg)

By Morgan Kelly, Office of Communications

The good news for any passionate supporter of climate-change science is that negative media reports seem to have only a passing effect on public opinion, according to Princeton University and University of Oxford researchers. The bad news is that positive stories don’t appear to possess much staying power, either. This dynamic suggests that climate scientists should reexamine how to effectively and more regularly engage the public, the researchers write.

Measured by how often people worldwide scour the Internet for information related to climate change, overall public interest in the topic has steadily waned since 2007, according to a report in the journal Environmental Research Letters. Yet, the downturn in public interest does not seem tied to any particular negative publicity regarding climate-change science, which is what the researchers primarily wanted to gauge.

First author William Anderegg, a postdoctoral research associate in the Princeton Environmental Institute who studies communication and climate change, and Gregory Goldsmith, a postdoctoral researcher at Oxford’s Environmental Change Institute, specifically looked into the effect on public interest and opinion of two widely reported, almost simultaneous events.

The first involved the November 2009 hacking of emails from the Climate Research Unit at the University of East Anglia in the United Kingdom, which has been a preeminent source of data confirming human-driven climate change. Known as “climategate,” this event was initially trumpeted as proving that dissenting scientific views related to climate change have been maliciously quashed. Thorough investigations later declared that no misconduct took place.

The second event was the revelation in late 2009 that an error in the 2007 Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) — an organization under the auspices of the United Nations that periodically evaluates the science and impacts of climate change — overestimated how quickly glaciers in the Himalayas would melt.

To first get a general sense of public interest in climate change, Anderegg and Goldsmith combed the freely available database Google Trends for “global warming,” “climate change” and all related terms that people around the world searched for between 2004 and 2013. The researchers documented search trends in English, Chinese and Spanish, which are the top three languages on the Internet. Google Trends receives more than 80 percent of the world’s Internet search-engine activity, and it is increasingly called upon for research in economics, political science and public health.

Internet searches related to climate change began to climb following the 2006 release of the documentary “An Inconvenient Truth” starring former vice president Al Gore, and continued its ascent with the release of the IPCC’s fourth report, the researchers found.

Anderegg and Goldsmith specifically viewed searches for “climategate” between Nov. 1 and Dec. 31, 2009. They found that the search trend had a six-day “half-life,” meaning that search frequency dropped by 50 percent every six days. After 22 days, the number of searches for climategate was a mere 10 percent of its peak. Information about climategate was most sought in the United States, Canada and Australia, while the cities with the most searchers were Toronto, London and Washington, D.C.

Searches for the phrase "global warming hoax" correlate with conservative political leanings

The researchers found that searchers for the phrase “global warming hoax” and related terms correlate in the United States with Republican or conservative political leanings. They compared the prevalence of searches for “global warming hoax” with the Cook Partisan Voting Index — which gauges how far toward Republicans or Democrats a congressional district leans — for 34 US states (above). They found that the more Republican/conservative the state (bottom measurement), the more frequently people in that state looked up related terms. The bottom graph shows how often a state votes Democrat (low numbers) versus Republican (high numbers). The numbers on the left indicate how often people looked up “global warming hoax” based on its percentage of the maximum search volume at any given point in time. (Image courtesy of William Anderegg)

The researchers tracked the popularity of the term “global warming hoax” to gauge the overall negative effect of climategate and the IPCC error on how the public perceives climate change. They found that searches for the term were actually higher the year before the events than during the year afterward.

“The search volume quickly returns to the same level as before the incident,” Goldsmith said. “This suggests no long-term change in the level of climate-change skepticism.

We found that intense media coverage of an event such as ‘climategate’ was followed by bursts of public interest, but these bursts were short-lived.”

All of this is to say that moments of great consternation for climate scientists seem to barely register in the public consciousness, Anderegg said. The study notes that independent polling data also indicate that these events had very little effect on American public opinion. “There’s a lot of handwringing among scientists, and a belief that these events permanently damaged public trust. What these results suggest is that that’s just not true,” Anderegg said.

While that’s good in a sense, Anderegg said, his and Goldsmith’s results also suggest that climate change as a whole does not top the list of gripping public topics. For instance, he said, climategate had the same Internet half-life as the public fallout from pro-golfer Tiger Woods’ extramarital affair, which happened around the same time (but received far more searches).

A public with little interest in climate change is unlikely to push for policies that actually address the problem, Anderegg said. He and Goldsmith suggest communicating in terms familiar to the public rather than to scientists. For example, their findings suggest that most people still identify with the term “global warming” instead of “climate change,” though the shift toward embracing the more scientific term is clear.

“If public interest in climate change is falling, it may be more difficult to muster public concern to address climate change,” Anderegg said. “This long-term trend of declining interest is worrying and something I hope we can address soon.”

One outcome of the research might be to shift scientists’ focus away from battling short-lived, so-called scandals, said Michael Oppenheimer, Princeton’s Albert G. Milbank Professor of Geosciences and International Affairs. The study should remind climate scientists that every little misstep or controversy does not make or break the public’s confidence in their work, he said. Oppenheimer, who was not involved in the study, is a long-time participant in the IPCC and an author of the Fifth Assessment Report being released this year in sections.

“This is an important study because it puts scientists’ concerns about climate skepticism in perspective,” Oppenheimer said. “While scientists should maintain the aspirational goal of their work being error-free, they should be less distracted by concerns that a few missteps will seriously influence attitudes in the general public, which by-and-large has never heard of these episodes.”

Read the article.

Anderegg, William R. L., Gregory R. Goldsmith. 2014. Public interest in climate change over the past decade and the effects of the ‘climategate’ media event. Environmental Research Letters 9 054005. doi:10.1088/1748-9326/9/5/054005 Article published online May 20, 2014.

Unlocking the potential of bacterial gene clusters to discover new antibiotics (Proc. Natl. Acad. Sci.)

High-throughput screening for the discovery of small molecules that activate silent bacterial gene clusters

High-throughput screening for the discovery of small molecules that activate silent bacterial gene clusters. Image courtesy of Mohammad Seyedsayamdost.

by Tien Nguyen, Department of Chemistry

Resistance to antibiotics has been steadily rising and poses a serious threat to the stronghold of existing treatments. Now, a method from Mohammad Seyedsayamdost, an assistant professor of chemistry at Princeton University, may open the door to the discovery of a host of potential drug candidates.

The vast majority of anti-infectives on the market today are bacterial natural products, made by biosynthetic gene clusters. Genome sequencing of bacteria has revealed that these active gene clusters are outnumbered approximately ten times by so-called silent gene clusters.

“Turning these clusters on would really expand our available chemical space to search for new antibiotic or otherwise therapeutically useful molecules,” Seyedsayamdost said.

In an article published last week in the journal Proceedings of the National Academy of Sciences, Seyedsayamdost reported a strategy to quickly screen whole libraries of compounds to find elicitors, small molecules that can turn on a specific gene cluster. He used a genetic reporter that fluoresces or generates a color when the gene cluster is activated to easily identify positive hits. Using this method, two silent gene clusters were successfully activated and a new metabolite was discovered.

Application of this work promises to uncover new bacterial natural products and provide insights into the regulatory networks that control silent gene clusters.

Read the abstract.

Seyedsayamdost, M. R. “High-throughput platform for the discovery of elicitors of silent bacterial gene clusters.” Proc. Natl. Acad. Sci. 2014, Early edition.

Why a bacterium got its curve — and why biologists should know (Nature Communications)

Art by Laura Ancona

Princeton University researchers found that the banana-like curve of the bacteria Caulobacter crescentus provides stability and helps them flourish as a group in the moving water they experience in nature. The findings suggest a new way of studying the evolution of bacteria that emphasizes using naturalistic settings. The illustration shows how C. crescentus divides asymmetrically into a “stalked” mother cell that anchors to a bacterium’s home surface, and an upper unattached portion that forms a new, juvenile cell known as a “swarmer.” Swarmer cells later morph into stalked cells and lay down roots nearby. They repeat the life cycle with their own swarmer cell and the bacterial colony grows. The Princeton researchers found that in moving water, curvature points the swarmer cell toward the surface to which it needs to attach. This ensures that the bacteria’s next generation does not stray too far from its progenitors. (Image by Laura Ancona)

By Morgan Kelly, Office of Communications

Drawing from his engineering background, Princeton University researcher Alexandre Persat had a notion as to why the bacteria Caulobacter crescentus are curved — a hunch that now could lead to a new way of studying the evolution of bacteria, according to research published in the journal Nature Communications.

Commonly used in labs to study cell division, C. crescentus naturally take on a banana-like curve, but they also can undergo a mutation in which they grow to be perfectly straight. The problem was that in a laboratory there was no apparent functional difference between the two shapes. So a question among biologists was, why would nature bother?

Then Persat, who is a postdoctoral researcher in the group of Associate Professor of Molecular Biology Zemer Gitai, considered that the bacteria dwell in large groups attached to surfaces in lakes, ponds and streams. That means that their curvature could be an adaptation that allows C. crescentus to better develop in the water currents the organisms experience in nature.

In the new paper, first author Persat, corresponding author Gitai and Howard Stone, Princeton’s Donald R. Dixon ’69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering, report that curvature does more than just help C. crescentus hold their ground in moving fluid. The researchers monitored C. crescentus growth on surfaces in flow and found that the bacteria’s arched anatomy is crucial to flourishing as a group.

“It didn’t take a long time to figure out how flow brought out the advantages of curvature,” Persat said. “The obvious thing to me as someone with a fluid-dynamics background was that this shape had something to do with fluid flow.”

The findings emphasize the need to study bacteria in a naturalistic setting, said Gitai, whose group focuses on how bacterial shapes are genetically determined. While a petri dish generally suffices for this line of study, the functionality of bacterial genes and anatomy can be elusive in most lab settings, he said. For instance, he said, 80 percent of the genes in C. crescentus are seemingly disposable — but they might not be in nature.

“We now see there can be benefits to bacterial shapes that are only seen in a growth environment that is close to the bacteria’s natural environment,” Gitai said.

“For C. crescentus, the ecology was telling us there is an advantage to being curved, but nothing we previously did in the lab could detect what that was,” he said. “We need to not only think of the chemical environment of the bacteria — we also need to think of the physical environment. I think of this research as opening a whole new axis of studying bacteria.”

While most bacteria grow and divide as two identical “daughter” cells, C. crescentus divides asymmetrically. A “stalked” mother cell anchors to a bacterium’s home surface while the upper unattached portion forms a new, juvenile version of the stalked cell known as a “swarmer” cell. The swarmer cells later morph into stalked cells then eventually detach before laying down roots nearby. They repeat the life cycle with their own swarmer cell and the bacterial colony grows.

The Princeton researchers found that in moving water, curvature points the swarmer cell toward the surface to which it needs to attach. This ensures that the bacteria’s next generation does not stray too far from its progenitors, as well as from the nutrients that prompted cell division in the first place, Gitai said. On the other hand, the upper cells of straight bacteria — which are comparatively higher from the ground — are more likely to be carried far away as they are to stay near home.

But the advantage of curvature only goes so far. The researchers found that when the water current was too strong, both curved and straight bacteria were pressed flat against the surface, eliminating the curved cells’ colonization advantage.

These findings put some interesting boundaries on what is known about C. crescentus, starting with the upper limits of the current in which the organism can thrive, Gitai said. He and Persat also plan to pursue whether the bacteria are able to straighten out and cast offspring downstream when the home colony faces a decline in available nutrients.

At the same time, understanding why C. crescentus got its curve helps in figuring out the evolution of other bacteria, he said. Close relatives of the bacteria, for example, are not curved — could it have to do with the severity of their natural environment, such as the powerful turbulence of an ocean? Harmful bacteria such as Vibrio cholerae, strains of which cause cholera, are curved, though the reason is unclear. It’s possible this shape could be related to the organism’s environment in a way that might help treat those infected by it, Gitai said.

Whatever the reason for a specific bacteria’s shape, the Princeton research shows that exploring the influence of its natural habitat could be worthwhile, Gitai said.

“It was clear with C. crescentus that we needed to try something different,” Gitai said. “People didn’t really think of flow as a major driver of this bacteria’s evolution. That really is a new idea.”

Read the article..

Persat, Alexandre, Howard A. Stone, Zemer Gitai. 2014. The curved shape of Caulobacter crescentus enhances surface colonization in flow. Nature Communications. Article published online May 8, 2014. DOI: 10.1038/ncomms4824

The work was supported by the Gordon and Betty Moore Foundation (grant no. GBMF 2550.02), the National Science Foundation (grant no. CBET-1234500), and the National Institutes of Health Director’s New Investigator Innovator Award (grant no. 1DP2OD004389).