NEWS OF THE WEEK MICROMACHINES
GETTING BACTERIA TO DO THE WORK Microscale motor relies on yoked microbes to spin a rotor
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INDING BEAST TO MACHINE,
researchers injapanhave created a micromotor powered entirely by bacteria. It's a spinning device that successfully integrates inorganic materials with living bacteria (five. Natl. Acad. Sci. USA, DOL 10.1073/pnas.0604122103). The micromotor consists of three parts: a silicon circular track; a silicon dioxide rotor that fits in the track's groove; and Mycoplasma mobile, a species ofgliding bacteria that is covalently yoked to the rotor. M. mobile moves around the track at a speed of 2-5 jim/second, dragging the rotor along with it. "We had predicted this micromotor would work, theoretically,,, says author Yuichi Hiratsuka, of the National Institute ofAdvanced Industrial Science & Technology in Tsukuba. "But we were absolutely excited when we first saw it rotate." (See C&EN Online for a video clip of the rotating motor.) Hiratsuka says this type of micromotor might one day be used to drive a pump on a microchip or be used in electronic generator systems that are powered entirely by glucose, the bacteria's energy source. Standard semiconductor manufacturing techniques were used to build the mkiomachine. The tough part was creating the interface between the inorganic micromachine and the bacteria, Hiratsuka says. M. mobile won't budge on surfaces devoid of sialic arid-containing proteins, so the researchers deposited one such protein, fetuin, as a top layer on the track. To attach M. mobile to the rotor, the researchers connected a 20-nm flexible polyethylene linker to proteins on the bacteria's exterior surface. At the far end of the linker, WWW.CEN-0NLINE.ORG
they deposited biotin, an imidazole derivative. Biotin binds tightly to the protein streptavidin, which was coated on the rotor. Et voild, a micromachine set to swirl. William O. Hancock, a bioengineer at Pennsylvania State University, calls the research "elegant."
"It's a milestone along the way of proving the idea that you can have biomechanical systems powering engineered devices." He adds, "I think this work will have legs."
Hiratsuka's results join an eclectic body of research that uses living cells to power micromachinery. Last year, a Harvard University group used surface chemistry to attach polystyrene beads to swimming single-celled algae. The algae's movement is directed by light, and once they reached their destination, the beads could be removed through photochemistry (Proc. Natl. Acad. Sci. USA 2005,102,11963). Bioengineers at UCLA have also harnessed the beating power ofheart muscle cells to move a microdevice (Nat. Mater. 2005,4,180).-SARAH EVERTS
SPIN Schematic (above) and top view (image, left) of a six-sided, 20jLim-diameter rotor driven by bacteria.
AGROCHEMICALS
Bayer CropScience Cuts Jobs, Gets Sued
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n an effort to boost the performance of a key unit, Bayer is restructuring its Bayer CropScience business to save nearly $400 million annually. Bayer CropScience will shed 1,500 jobs through 2009, mostly in North America, out of about 19,000 positions worldwide. The move will be accompanied by plant closures. The company says it will reduce the number of sites from 50 in 2005 to 36 in 2009, with cuts coming both from formulation and active ingredient synthesis plants. Together with procurement optimization, these steps are intended to generate annual savings of $385 million by the time the restructuring is completed in 2009. Because of the actions, Bayer will take charges and write-downs of nearly $600 million over the next two years. The plan is in addition to a five-year program,
initiated in 2002, meant to cut costs by $900 million. Bayer CEO Werner Wenning told analysts last week that the unit has been performing well versus its peers but is facing tough times in North America and South America, particularly Brazil. Bayer CropScience had first-half 2006 sales of $3.3 billion and generated profit margins before taxes of 19%. The new cuts are meant to support a profit-margin target of 25%. Separately, Bayer is facing class-action lawsuits brought by rice farmers over a genetically modified rice strain recently discovered in the long-grain-rice supply (C&EN, Aug. 28, page 7). The suits allege that Bayer was negligent in allowing the strains to contaminate the market. They seek compensation for the drop in rice prices since the contamination with genetically modified rice was found.— ALEX TULLO
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