A Bacterium That Acts Like a Toothbrush

Researchers have identified a new ally in the war against tooth decay: an enzyme produced by a mouth bacterium that prevents plaque formation. The finding could eventually lead to the development of toothpaste that harnesses the body's own plaque-fighting tools.

The human mouth is awash with bacteria. More than 700 species thrive in the hot, moist conditions, including Streptococcus mutans, one of the main components of plaque. Clinging to the teeth in thin layers called biofilms, S. mutans digests sugars and produces acids that can eat into enamel and cause cavities. Other bacteria are more gracious guests. In 2009, for example, scientists found that S. salivarius, a type of bacterium found on the tongue and other soft tissues in the mouth, decreases the buildup of S. mutans biofilms.

Hidenobu Senpuku, a biologist at the National Institute of Infectious Diseases in Tokyo, and colleagues wanted to know what substance conferred S. salivarius's cavity-fighting powers. Using chromatography, a method that divides the molecules in a mixture based on charge or size, they separated out individual proteins from samples of the microbe. The scientists then mixed each kind of protein with S. mutans cells and measured which cultures grew the smallest amount of biofilm on plates in the lab. The protein FruA, an enzyme that breaks apart complex sugars, was the most powerful biofilm blocker.

The researchers also found that a form of FruA, produced by the common fungus Aspergillus niger and available off-the-shelf, stymies plaque equally well. This commercial FruA worked despite the fact that its amino acid sequence is somewhat different from that of S. salivarius FruA. That might speed the development of toothpastes that include FruA, says Senpuku.

The findings, reported in Applied and Environmental Microbiology, are not a license to eat all the candy you want, however. When researchers increased the concentration of sucrose, a type of sugar, in mixtures containing S. salivarius FruA and S. mutans, the beneficial bacterium lost its ability to prevent biofilm formation. The authors write that this observation may help explain why a 1996 study found that FruA contributed to cavity formation in rats.

Mary Ellen Davey, a microbiologist at the Forsyth Institute in Cambridge, Massachusetts, agrees that the findings could spur the development of better toothpaste. But she says that won't be an easy task. Finding "the formulation that would 'guarantee' that the enzyme remained enzymatically active on the shelf of your favorite drug store is a big challenge," she says.

News Release : Scientists Find Part of New Zealand's Submerged "Pink Terraces"

They were called the Eighth Wonder of the World. Until the late 19^th century, New Zealand’s Pink and White Terraces along Lake Rotomahana on the North Island, attracted tourists from around the world, interested in seeing the beautiful natural formations created by a large geothermal system. But the eruption of Mt. Tarawera on June 10, 1886, buried the terraces in sediment and caused the lake basin to enlarge, engulfing the land where the terraces stood. For more than a century, people have speculated whether any part of the Pink and White Terraces survived the eruption.

This week, scientists from New Zealand’s GNS Science, one of several government laboratories, in collaboration with engineers and scientists from Woods Hole Oceanographic Institution (WHOI) and colleagues from Lamont-Doherty Earth Observatory of Columbia University and NOAA-PMEL, located portions of the long-lost Pink Terraces.

The research team, using autonomous underwater vehicles (AUVs) to map the bottom of Lake Rotomahana, are certain they have found the lower portions of the Pink Terraces on the lake floor. Project leader Cornel de Ronde, of GNS Science, said the team was elated by the discovery.

“The first sidescan sonar image gave a hint of a terraced structure so we scanned the area twice more and we are now 95 percent certain we are seeing the bottom two tiers of the Pink Terraces,” de Ronde said. 

Side-scan sonar and bathymetric data collected by two REMUS 100 AUVs clearly show crescent-shaped terraced structures in about 60 meters of water where the Pink Terraces were located prior to 1886. They are covered by a brownish lake sediment.

The free-swimming REMUS vehicles were developed by WHOI with funding from the US Navy and were operated by Amy Kukulya and Robin Littlefield of the WHOI Oceanographic Systems Laboratory (OSL) who travelled to New Zealand for the expedition.  Dan Fornari, a scientist with the WHOI Geology & Geophysics department, helped lead the expedition and, along with Marshall Swartz of the WHOI Physical Oceanography department, developed the underwater camera system used in the lake.

After detecting areas of interest with the AUV’s sonar systems, the team used the underwater camera system, developed with funds from the U.S. National Science Foundation, to capture images of the lake floor where they were able to photograph some of the stepped terrace edges.

Dr. de Ronde said the rest of the Pink Terraces were either destroyed during the eruption, or are still concealed under thick sediment not able to be penetrated by high-frequency AUV sonars.

The scientists found no sign of the larger White Terraces in the part of the lake that matched their location prior to 1886. The two terraces, part of a very large on-land geothermal system, were separated by several hundred meters prior to the eruption.  

There are very few examples of large land-based geothermal systems that have been torn apart by an eruption and become inundated in this way. Scientists hope the data collected during this expedition will help them better understand how geothermal systems respond to disruptions of this kind.

“It was very gratifying to take the tools and knowledge we’ve developed for ocean research and apply them to work in the lake, especially for a scientific project with so much Maori cultural significance.”

In 2009, WHOI signed a memorandum of understanding with GNS and New Zealand’s National Institute for Water and Atmospheric Research (NIWA) to expand research and technology development collaborations across the scientific disciplines in the southwest Pacific and within New Zealand territorial waters.  In addition to the work in Lake Rotomahana, the organizations are also collaborating on deep ocean research on the Kermadec Seamounts north of New Zealand’s North Island using the Sentry AUV and TowCam deep-sea imaging system.

“We hope the success in Lake Rotomahana is the first of many scientific collaborations in this part of the world where there are many interesting research problems to investigate.”

The project was a collaboration involving GNS Science, Woods Hole Oceanographic Institution in Massachusetts, Lamont-Doherty Earth Observatory at Columbia University in New York, the National Oceanic and Atmospheric Administration in Seattle, and the University of Waikato.

After this week’s discovery, de Ronde paid tribute to colleagues from WHOI, saying “This result would not have been possible without the team from Woods Hole Oceanographic Institution and their American colleagues. Their contribution has been huge.”

As the Seasons Change, Will the Plankton?

Antonio Mannino had been at sea for more than a week, collecting samples of seawater and plankton and measuring the conditions in the North Atlantic Ocean. It was not exactly a luxury cruise, but to understand the planet’s biggest food source—phytoplankton—and perhaps its most important sink for carbon dioxide, you’ve got to get out on the water.

As is common in late autumn—when cold north winds of winter battle for supremacy of the North Atlantic against the lingering warm fronts of summer—the weather grew messy. Seas churned with waves rising seven to fourteen feet, and Mannino and colleagues struggled to cast water samplers and nets over the sides of the Delaware IIresearch vessel. After several days, the foul weather made it impossible to work, and the captain began steaming back from Georges Bank toward Provincetown, Massachusetts. He planned to lay anchor in the (hopefully) calmer waters of Cape Cod Bay and ride out the storm.

Mannino, an oceanographer from NASA’s Goddard Space Flight Center, was sitting in the ship’s galley, while graduate student Dave Munro dozed on a nearby couch. It was Friday the 13th.

Thud. Splash. Slosh.

A wave crashed through the porthole window, knocking out the glass and dousing Munro in a bath of seawater. A few tens of gallons sloshed around on the galley floor as the crew sealed the porthole hatch. No one was injured, and the ship was never in serious danger, but it was enough to send them back to port in Woods Hole.

The 155-foot Fisheries Survey Vessel Delaware II, operated by the National Oceanic and Atmospheric Administration (NOAA), is a 40-year-old workhorse. Spare parts are not exactly lying around on a shelf. So the crew did what seamen do: they bolted steel plates over the porthole, soldered things shut, and got back out to sea. There was research to be done, and time spent in port is time and money lost.

The 155-foot survey vessel Delaware II is operated by the U.S. National Marine Fisheries Service for studies of fish stocks and for support of basic research like CliVEC. (Photo courtesy Charles Byrne, NOAA.)

Mannino and colleagues from NASA, NOAA, and Old Dominion University headed back out into the North Atlantic for another week, sharing cramped quarters, cozy labs, and choppy autumn seas to see how those turbulent waters influence the tiniest and most important ocean life forms.