[Proceedings of the National Academy of Sciences | 3.3.08]
Research efforts led by the BioTechnology Institute’s Daniel Bond and Jeffrey Gralnick have resulted in a key finding about how bacteria convert organic compounds into electricity. The researchers discovered that riboflavin (commonly known as vitamin B-2) is responsible for much of the energy produced by Shewanella bacteria.
“This is very exciting because it solves a fundamental biological puzzle,” Bond says. “Scientists have known for years that Shewanella produce electricity. Now we know how they do it.”
Shewanella, commonly found in water and soil, can convert simple organic compounds into electricity. The discovery means Shewanella can produce more power simply by increasing riboflavin levels. The finding also opens up multiple possibilities for innovations in renewable energy and environmental clean-up.
The interdisciplinary research team, which included several students, showed that bacteria growing on electrodes naturally produced riboflavin. Because riboflavin was able to carry electrons from the living cells to the electrodes, rates of electricity production increased by 370 percent as riboflavin accumulated.
Scaled-up “microbial fuel cells” using similar bacteria could generate enough electricity to clean up wastewater or power remote sensors on the ocean floor. But more ambitious applications, such as electricity for transportation, homes or businesses, will require further advances in biology and in the cost-effectiveness of fuel cell materials.
[Proceedings of the National Academy of Sciences | 12.07]
A common bacterium found in soil and water can be used to convert a chemical into nanotubes that conduct electricity and light. The environmentally friendly nanotubes have a variety of potential uses in electronics.
The discovery was made by a multinational team of scientists, including Michael Sadowsky, of the BioTechnology Institute. The bacterium, Shewanella sp. strain HN-41, has the unique ability to convert arsenate into arsenic sulfide nanotubes. This is the first time these specialized nanotubes have been produced by biological rather than chemical means.
“Nanotubes can be used to make fuel cells, batteries, biosensors, and a variety of other devices, such as novel semiconductors that could not be made by other means, Sadowsky says. “This is a very exciting discovery.”
The study’s lead author, Hor-Gil Hur, from Gwangju Institute of Science and Technology in South Korea, is spending this academic year as a visiting scholar at the University of Minnesota.
[Proceedings of the National Academy of Sciences | 1.7.08]
Kate VandenBosch, professor and head of plant biology, and colleagues at the Massachusetts Institute of Technology have discovered a molecular pass code that allows helpful bacteria to infect the roots of legumes, a relationship that benefits both partners. (The roots sustain the bacteria, and in exchange the bacteria provide nitrogen, a nutrient essential for plant growth.)
Recent research suggests that plants scan surface molecules to determine whether bacteria are friendly or harmful. The researchers examined plant gene expression as a measure of the plants’ response to the symbiotic bacteria. They found that if the bacteria lacked a surface polysaccharide called succinoglycan, the plant responded by turning off defense genes. This showed that plants sense the presence of succinoglycan, which serves as a pass code to allow these beneficial bacteria to infect the plant.
[Nature.com | 2.08]
Hiroshi Matsuo and Reuben Harris, assistant professors in the Department of Biochemistry, Molecular Biology and Biophysics, have determined the molecular structure of APOBEC3G—a protein that inhibits the AIDS virus, HIV. The landmark discovery will help researchers engineer APOBEC3G to develop new treatments for HIV and AIDS.
[Current Biology | 12.19.07]
Female chimpanzees and female humans stop reproducing at about the same age, but only human females go through menopause and continue to live for an extended period. Female chimpanzees tend to survive only as long as they are fertile. Only very fit chimpanzees who maintain high birth rates late into life have long lives.
Anne Pusey, director of the University of Minnesota’s Jane Goodall Institute’s Center for Primate Studies, co-authored the study reporting these findings. Melissa Thompson, a former student of Pusey’s now at Harvard University, was lead author.
Human menopause appears to be unique because the reproductive system declines much faster than other systems, leaving an extended post-reproductive period for many women. To gain insights into human menopause, Thompson teamed up with researchers from six chimpanzee research sites across Africa, including Gombe National Park, where Jane Goodall began her pioneering work in 1960.
The group found that chimpanzee and human birth rates show similar patterns of decline after the age of 40, suggesting that the “biological clock” has been relatively conserved over the course of human evolution. Other studies have shown that gorillas and apes do not experience an extended post-reproductive lifespan either. But the adaptive reason for human menopause remains unclear.
[Anticancer Research | 8.21.07]
While prostate cancer appears to be more aggressive in black men than in white men, a study conducted by Akhouri Sinha, professor of genetics, cell biology and development, does not support that notion. In fact, what appears to be greater aggressiveness is likely the result of inferior treatment.
In previous studies, prostate tumors in black patients tended to be larger and more advanced, and black men had higher blood levels of prostate specific antigen (PSA), a substance produced by the prostate that, at high levels, points to the possibility of prostate cancer. But, according to the study, all these criteria are interrelated and could be the result of delayed diagnosis or medical care.
“Our data shows that among patients receiving similar treatment, African-Americans did not follow up with their doctors as consistently as Caucasians.” Sinha says. “In addition, Caucasian patients were four times as likely to receive additional treatment after prostatectomy.”
[Molecular Biology of the Cell | 10.07]
CBS researchers have found a new molecular target that has potential for treating cancer.
Assistant Professor Anja-Katrin Bielinsky and graduate student Sharbani Chattopadhyay, both in the Department of Biochemistry, Molecular Biology and Biophysics, have discovered a protein (Mcm10), which regulates a subunit of DNA Polymerase that prevents DNA damage during replication. Depletion of Mcm10 in human tissue culture leads to massive DNA damage and induces apoptosis (cell death).
The researchers believe Mcm10 could be used as a drug target for treating cancer because downregulating production of Mcm10 causes cells to die.
[Nature | 2.7.08]
The number of plant species worldwide may be dwindling from the effects of chronic low levels of nitrogen on terrestrial ecosystems, according to a study by Christopher Clark, a former graduate student, and David Tilman, Regents Professor of Ecology.
Research was carried out at Cedar Creek Ecosystem Science Reserve. “Even at low levels, comparable to nitrogen deposition over many industrialized nations, we lost about one plant species in six at our test site [17 percent over 23 years],” Clark says. But Clark and Tilman also discovered some good news—that the loss of species can be reversed. Thirteen years after addition of nitrogen was stopped, species numbers had recovered.
