Science Concentrates FOOD experimental high-throughput screening method that involves studying the effects of chemical mixtures on cyanobacteria, a group of microorganisms found abundantly in water systems (Sci. Adv. 2016, DOI: 10.1126/sciadv.1601272). The team created 180 mixtures of 16 pharmaceutical and personal care product chemicals at nanogram to microgram levels. The researchers modified the cyanobacteria so that they would be bioluminescent and then tracked the toxicity impact of the mixtures by measuring light intensity. For example, the bacteria produce fewer bioluminescent proteins, and thus emit less light, when they are struggling with the toxicity of specific drug mixtures.—SARAH EVERTS
Beer yeast adapted to life with humans
MICROBIOME
▸ Microbial communities thrive in fracking wells Some hardy microorganisms can survive the harsh underground conditions created by the oil and natural gas extraction method known as hydraulic fracturing. New revelations about the microbes come from a team led by microbiologist Kelly C. Wrighton of Ohio State University, which has used metagenomics CH3 and metabolite analyses O +N CH3 to characterize microbial –O CH3 communities deep inside the Marcellus and Utica Glycine betaine shale formations of the northeastern U.S. (Nat. Microbiol. 2016, DOI: 10.1038/nmicrobiol.2016.146). The researchers collected samples from a week to months after initial fracking when oil and gas were flowing from the wells. From metagenomics data, they reconstructed 31 microbial genomes, finding one organism that seems to be unique to shale formations, which they have named Candidatus Frackibacter. Overall, the microbes have interdependent metabolisms. For example, some microbes make glycine betaine, a compound that protects cells against osmotic stress that results from the high salt content of the shale. Other organisms take up that glycine betaine and metabolize it to form trimethylamine, which can be used by still other organisms to produce methane. The researchers also identified microbes that are likely culprits in producing sulfides that can lead to equipment corrosion and oil and gas reservoir souring. They further
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observed that the microbes persisted and even thrived despite added biocides and the high temperatures of fracking wells.—CELIA ARNAUD
SYNTHESIS
▸ Flow reaction reduces aryl diazonium safety risk The Balz-Schiemann reaction is a versatile means for synthesizing aryl fluorides from anilines. But there’s a catch: The procedure involves preparing and isolating intermediate aryl diazonium salts or generating them in situ under batch conditions. Both routes present a safety hazard because diazonium salts have the potential to spontaneously undergo violent decomposition,
R
NH2 Anilines
CF3CO2H, (CH3)3CONO, LiBF4, H3C(CH2)3CO2CH3
which has limited the scalability and utility of the reaction. Nathaniel H. Park, Timothy J. Senter, and Stephen L. Buchwald of Massachusetts Institute of Technology have addressed this problem by devising a continuous-flow process to prepare aryl diazonium salts that eliminates the need to handle them directly (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201606601). The researchers were challenged to find reagents and conditions for their flow reactor that avoid side reactions that sometimes plague the Balz-Schiemann reaction and still lead to the desired aryl diazonium salts. Using the streamlined diazonium preparation shown, they fed the intermediate into a stirred batch reactor for the final dediazotization step to prevent precipitated salt from clogging the reactor channel. The approach enabled the MIT team to quickly and safely produce gram amounts of aryl and heteroaryl fluorides.—STEVE
RITTER R
Continuous-flow generation of aryl diazonium salts
N2+X–
F
R Aryl fluorides
C R E D I T: S H UT T E RSTO C K ( BE E R )
Long before scientists discovered the existence of microorganisms, humans domesticated yeast, coaxing the organism to make palatable beer in exchange for a reliable supply of food and a stable existence. A comprehensive genetic and phenotypic analysis of 157 Saccharomyces cerevisiae yeast strains used in fermentation industries Beer-making yeast has reveals that beer-making yeasts originate from a cozy life with humans. a few common ancestors that quickly evolved ways to satisfy their brewmasters (Cell 2016, DOI: 10.1016/j.cell.2016.08.020). A team led by Kevin J. Verstrepen and Steven Maere of the Flemish Institute for Biotechnology found that, compared with wild yeast, beer yeast has duplicated genes that help the organism break down maltotriose, a sugar found in beer mash. Many beer yeast strains have also evolved CH3O mutations that prevent production of 4-vinylguaiacol, an off-flavor in many beers. Meanwhile, because beer yeast HO is used continuously from one batch to another, it has lost the ability to reproduce sexually, the researchers found, a 4-Vinylguaiacol skill the organisms would need to survive and to adapt to stressful environments in the wild. By comparison, the team found that wine yeast still retains the ability to reproduce sexually, probably because wine making occurs only in autumn, leaving the yeast to fend for themselves during the rest of the year.—SARAH EVERTS
