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This Week in PNAS: Aug 16, 2016

In the early, online edition of the Proceedings of the National Academy of Sciences, a Johns Hopkins University-led team characterizes rare somatic mutations in genomic and mitochondrial DNA from normal human tissues using a massively parallel, barcoded sequencing method called the bottleneck sequencing system (BotSeqS), which involves a dilution step prior to DNA amplification. For their proof-of-principle analysis, the researchers applied the approach to 44 normal human tissue samples from 34 individuals, highlighting somatic mutation differences that coincided with age, tissue type, carcinogen exposure, and more. "This technology can provide insights into the number and nature of genetic alterations in normal tissues," they write, "and can be used to address a variety of fundamental questions about the genomes of diseased tissues."

Researchers from France and Australia search for signs of chromosomal DNA transfer in representatives from an early branching clade of smooth tubercle bacteria thought to be similar to its shared ancestor with strains in the tuberculosis-causing Mycobacterium tuberculosis complex. With the help of genome sequencing and fluorescence-assisted mating assays, the team examined representatives from the M. canettii clade, narrowing in on examples of horizontal gene transfer involving stretches of sequence ranging from 100 base pairs to around 118,000 base pairs. "Although the transfer frequency between M. canettii strains was low and no transfer could be observed among classical Mycobacterium tuberculosis complex strains," they note, "our study provides the proof of concept for genetic exchange in tubercle bacilli."

A study by a German-led team suggests coronaviruses similar to those causing respiratory infections in humans are ubiquitous in dromedary camels. The researchers started by screening nasal swabs from 1,033 dromedary camels in Kenya and Saudi Arabia, uncovering RNA resembling the human coronavirus HCoV-229E in almost 6 percent of camels by RT-PCR. They also tested fecal samples from nearly 400 Arabian dromedary camels and blood samples from 364 dromedaries tested in half a dozen countries between the early 1980s and 2014. After identifying HCoV-229E sequences in more than 86 percent of camels tested from the Middle East in 2013 and 2014, the investigators generated genome sequences for HCoV-229E isolates from four Saudi Arabian dromedaries and one dromedary camel from Kenya as part of a wider analyses of the dromedary camel coronaviruses and their potential risk to humans.