NEWS OF TH E WEEK
CUTTING OFF BACTERIAL CHATTER MICROBIOLOGY: Targeting quorum sensing may lead to hardier antibiotics
O MATTER HOW innovative the antibiotic,
N
eventually, bacteria evolve to resist it. But a new study in cells suggests that by targeting certain bacterial networking behaviors, including the chemical communication known as quorum sensing, scientists might slow development of resistance (ACS Chem. Biol. 2014, DOI: 10.1021/cb5004288). Traditional antibiotics wipe out large swaths of bacteria, leaving the playing field open for one or two resistant microbes to dominate. Researchers developing quorum-sensing inhibitors would like some reassurance that the resistance problem won’t hinder their efforts, says Helen E. Blackwell of the University of Wisconsin, Madison. Her graduate student Joseph P. Gerdt set up a competition between two strains of Pseudomonas aeruginosa, a notoriously antibioticACS CHEM. BIOL.
One colony of resistant bacteria (dark spot) is able to digest a fluorescent nutrient to produce a light-blue halo. Regular microbes (light spots) that are close by can grab enough of the nutrient to survive.
FALLOUT CONTINUES FROM TAIWAN BLAST PETROCHEMICALS: Dengue fever outbreak follows July 31 explosion
T
that cases of dengue fever are surging in the southern city of Kaohsiung, where a chemical explosion last month killed 30 people and injured hundreds of others. The outbreak is adding both to the city’s hardship following the blast and to the troubles of the area’s chemical industry. The parts of the city that are closest to the blast site are hardest hit by the fever, according to Kaohsiung’s Department of Health. Heavy rains in the days following the disaster caused pools of water, which aren’t draining as they should because the explosion damaged the drainage system, the agency says. The country has ordered its HE JU NCHANG/XINHUA PRESS/CORBIS
Workers clear debris at the Kaohsiung explosion site.
AIWAN’S Centers for Disease Control reports
CEN.ACS.ORG
6
resistant pathogen. One strain had its quorum-sensing system genetically inactivated to mimic what would happen with a potent quorum-sensing inhibitor. The other strain mimicked bacteria that are resistant to quorum-sensing inhibitors. Gerdt then placed the strains in situations where they’d need an active quorum-sensing system to process nutrients. But when “resistant” microbes made up 1% or less of the total population, they failed to become the dominant strain. Blackwell suggests two possible reasons for this. One is that low levels of resistant microbes give off low levels of quorum-sensing signals. Without the necessary quorum to turn on nutrient-digesting genes, resistant microbes never gain an advantage. The second reason is that when resistant microbes do manage to break down nutrients, regular microbes can nab enough nutrients in cell cultures to survive, a behavior microbiologists call “cheating.” “These types of experiments are critical as we move forward in trying to develop practical applications of quorum sensing,” says University of Washington microbiologist E. Peter Greenberg. However, despite many teams’ efforts, he notes, no quorum-sensing inhibitor is yet potent enough or specific enough to be a drug. Blackwell says her team has recently developed its best quorum-sensing inhibitors yet and plans to run them through further tests before eventually attempting animal studies.—CARMEN DRAHL
military to assist Kaohsiung in controlling the disease. As of Aug. 18, Taiwan’s CDC had recorded 878 cases this year of dengue fever nationwide. The 171 new cases reported in the week before were almost all in Kaohsiung. By comparison, Taiwan registered fewer than 200 cases of the illness between January and October 2013. Dengue is a mosquito-borne disease that causes fever as well as muscle and joint pain. It is sometimes fatal. The July 31 accident will likely cloud the future of Taiwan’s petrochemical industry for years to come. The explosion was caused by a leak in a pipeline, buried under a densely populated neighborhood, that was delivering propylene gas to LCY Chemical, a Taiwanese producer of industrial chemicals. For residents of Kaohsiung, it was an unwelcome cap to what activists say have been decades of industrial accidents, spills, and ground contamination caused by the local petrochemical industry. After the blast, Taiwan’s government promised that it will rethink the future of the island’s petrochemical industry, which is disproportionately based in or near Kaohsiung. In particular, the government said it may encourage the relocation of some facilities in Kaohsiung to Dalinpu and Fenglingtou, two seaside communities in southern Taiwan. But, claiming that the petrochemical industry poses extreme danger, environmental groups and residents from the two locations organized a protest as soon as they learned of the plan.—JEAN-FRANÇOIS TREMBLAY
AUGUST 25, 2014
