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Volume 5, Number 1
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Teasing Out Microbial Secrets

By Erica Goldman

Ron Weiner in his office - photo by Sandy Rodgers
Photo by Sandy Rodgers

When Ronald Weiner logged his 10,000th grade assignment in 2001, he decided that it was time to shift the emphasis of his career. For more than 30 years, Weiner has taught microbiology to students at the University of Maryland, College Park (UMCP) with passion and humor. At times Weiner's teaching assistant would introduce him in the spirit of Johnny Carson. "Here's Ronny´┐Ż" would bring Weiner to the front of the lecture hall and he'd start each class with a brief monologue, jokes that he hoped were relevant to the subject at hand. "My first love has and will always be teaching," he says, but it was time, he decided, to focus on bringing closure to his prolific academic career.

Weiner's love for science rivals his zeal for teaching. For as long as he can remember, he has been interested in the world beyond the reaches of human perception. He was the first kid on his block with a microscope, the first to jab his finger and look at his blood up close.

Born from this youthful curiosity about the natural world, Weiner's career in science has led him down twisting paths to some important and unexpected discoveries. During his tenure at UMCP, he's made major contributions in two areas within microbiology. He's helped to unveil the biochemical secrets of mysterious microbial communities that create biofilms on boat bottoms and oyster bars. He's also found a species of bacteria that breaks down complex carbohydrates in the ocean, a discovery that helps to fill a key gap in our understanding of the marine carbon cycle. Of his journey, Weiner says, "It has been a good ride."

Forming Films

When Weiner first joined the faculty in Microbiology at UMCP in 1970, his scientific efforts focused on studying how cells differentiate and age, one of the fundamental questions in microbiology.

As a model for cellular aging, he used the bacteria Hyphomonas, whose two-phase life cycle made it ideal for studying life cycle transitions. But this microbe is also a primary colonizer in the marine environment, a fact that soon sent Weiner riding down an unanticipated road. Hyphomonas is one of the first organisms to form complex biofilms that stick to and foul the bottoms of ships, providing a fertile home for many marine creatures, a fact that drives boat owners to expensive haul outs for scraping and repainting jobs nearly every year. The U.S. Navy, owners of big boats like battleships and aircraft carriers, wanted a better understanding of ways to control biofilm buildup. Weiner soon had a new program underway, thanks to support from the Office of Naval Research.

Micrograph of Saccharophagus degradans - photo by Ronald Weiner
Culture flasks - one with underwater plants and one with no visible plants (bacteria digested them) - photo by Ronald Weiner
Micrograph of Hyphomonas adherans - photo by Ronald Weiner
During a long and distinguished career, Ronald Weiner has followed the path of two enigmatic microbes. Hyphomonas adherans (bottom left), a primary colonizer in microbial communities called biofilms, produces a sticky adhesive that allows it to adhere to surfaces with great force. The other, Saccharophagus degradans 2-40 (top), is a degrader-extraordinaire. It can break down hard-to-digest marine material, such as algae and chitin, and make underwater plants disappear, as shown in the flask above. Photos by Ronald Weiner.

Before long he made some unforeseen discoveries that had nothing to do with boats and a lot to do with oysters. Biofilms, as it turns out, strongly attract oyster larvae floating in the water and encourage them to circle down and settle into place. With support from Maryland Sea Grant, Weiner explored the biochemical basis of this attraction, identifying the compounds produced by the biofilm's bacteria that induce oyster larvae to initiate stereotypic swimming patterns. "The larvae would detect [these compounds], swim in a circle like a dog circling a fire hydrant, always in the same direction, and then settle down," Weiner describes.

From cellular aging to biofilms to oysters — out of this fundamental research, Weiner and his collaborators dug up some very practical applications. Weiner's oyster findings spawned the St. Georges Oyster Company, a commercial oyster hatchery down in St. Mary's County. The company validated Weiner's ideas that manipulating biochemical cues inducing larval settlement could increase oyster yield. A second company — the aptly named Adheron — seized on his findings about the adhesive power of biofilms. "If a bacterium [like Hyphomonas] can glue itself next to a ship's propeller in a turbid environment, that is one sticky bacterium," Weiner says. He tested the idea and found that these bacteria produce polymers with substantial adhesive strength that could set in salt water, a discovery with clear commercial potential.

Breaking Down Complex Carbs

Weiner's scientific road soon took another turn. By the late 1980s, he had learned a great deal about how biofilms form, but realized that he knew little about how they are broken down. For that matter, he realized that little is known in general about how organic compounds in the marine environment degrade.

What happens, for example to giant kelp after it dies or to a massive algal bloom after its cells settle on the ocean floor? What about the shells of crabs, lobsters, zooplankton? Where do they go? These questions are central, he realized, to understanding how carbon flows through the marine environment. He began to steer his research program on this new course.

Complex carbohydrates (polysaccharides) do not readily break down into their carbon constituents. A significant amount of marine complex carbohydrates contain cellulose, but researchers had not specifically uncovered a marine cellulose degrader. We knew that carbon from the ocean was being released to the atmosphere, but didn't know how it was broken down, says Weiner.

When a huge die-off hit the Chesapeake Bay's cordgrass ( Spartina) population in 1989, Weiner's colleague, George Andrykovitch from George Mason University in Fairfax, Virginia, enlisted his help to examine the microbial degradation process of the grass. Together, the two looked for an organism that might be responsible for Spartina's breakdown. They recognized that one dominant microbe played a central role. Weiner called this bug, 2-40 — a name that refers simply to second batch, 40th colony.

As he studied this species of bacteria in greater detail, again with support from Maryland Sea Grant, Weiner and coworkers found that 2-40 produces a whole slew of enzymes specialized to break down not only the cell walls of plants but also chitin, the carbohydrate that makes up a crab's exoskeleton. The regulation of this enzyme production is complex, Weiner explains, but different steps in the process can be optimized to produce desired enzymes for commercial purposes. "The beauty of this is that it holds the record for degrading more complex carbohydrates than any bug ever detected," Weiner says.

With support from the Department of Energy, Weiner obtained the genome sequence of Saccharophagus degradans 2-40. The bacteria proved a "veritable goldmine of genes," he says. While the genome independently verified that this bug produces a lot of different enzymes that degrade complex carbohydrates, it also revealed some surprises. Weiner's group found that the 2-40 genome also codes for antibiotics and a molecule that blocks the function of protein-digesting enzymes, which scientists call a global protease inhibitor.

The microbe 2-40 proved very difficult to isolate on its own, leading Weiner to suspect that it forms close relationships with other organisms. He knows that some of its closest relatives can only function in true symbiotic relationships. The quest now, he explains, is to discover what this organism is actually doing in nature.

But regardless of how 2-40 operates in the environment, its unique properties have clear commercial potential. Weiner and co-workers have already secured 6 patents from 2-40 that encompass a range of its functions. They've patented a slurry from the bacteria which can be used to degrade marine biofilms and have secured a patent for the protease inhibitor. They are currently looking to patent 2-40's ability to break down lignin, a large carbohydrate molecule that helps give plants their mechanical strength. With 2-40's genome sequence in hand, this science is really getting interesting now, he says.

Bird's Eye View

Over its long road, Weiner's career has run the gamut. He has zoomed in on very basic questions in cell biology, such as cellular aging. And he has panned all the way out to functional applications, like oyster aquaculture and marine adhesives. Now, as he brings his work on 2-40 to fruition, Weiner also has the unique opportunity to view his field from a big-picture vantage point. He currently works at the National Science Foundation (NSF) as a Program Director within the division of Molecular and Cell Biosciences in the Biological Sciences Directorate. From this perspective he helps direct the flow of the peer review process, bringing him into contact with hundreds of grant proposals at the cutting edge of research in his field.

With the hindsight of a career's worth of experience in his discipline, Weiner finds that he now really enjoys the outlook on science that NSF provides. "You get a view of science that is different from what you've ever had before. You see it from different angles," he says. "You get to sometimes move it in a certain direction too."

While Weiner's enthusiasm for his life's work is unmistakable to those he encounters, the depth of it sometimes still comes as a surprise to him. "I found out something about myself when I got to NSF," he says. "I really love science."

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