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This Week in PLOS: Jan 11, 2016

In PLOS One, researchers from the National Oceanic and Atmospheric Administration and the University of Washington report on killer whale diet clues detected using DNA-based analyses of the animals' poop samples. The team pooled 175 fecal samples collected over the summers from 2006 to 2011 into 13 groups, which were compared with two control samples with known DNA compositions as well as sequence databases containing information for 19 fish that may fall prey to killer whales. Nearly 99 percent of the sequences generated stemmed from salmonid fish, the study's author found, with Chinook salmon appearing most often in early summer and Coho salmon sequences becoming more common later in the season.

A University of Vermont-led team detected cryptic brook trout populations using microsatellite DNA data. As they report in PLOS One, the researchers collected brook trout samples from western Maryland's Savage River watershed twice per year, in the summer and fall, between 2010 and 2013. Although there appeared to be few physical barriers to fish movement in this watershed, the investigators saw little in the way of genetic exchange between different brook trout populations, based on patterns at 13 microsatellite markers in 250 brook trout. "Our study highlights the importance of considering the possibility of multiple genetically distinct populations occurring within spatially contiguous habitats," they write, "and suggests the existence of a cryptic metapopulation: a spatially continuous distribution of organisms exhibiting metapopulation-like behaviors."

Harvard researchers reporting in PLOS Biology describe sporulation genes they detected in Bacillus subtilis with a transposon sequencing screens. Using a library designed to introduce more than 138,000 different insertions in the B. subtilis genome, the team uncovered almost 100 of the best known sporulation genes as well as 37 lesser known sporulation genes and two dozen genes not linked to sporulation in the past. In a series of follow-up imaging experiments, the study's authors examined the functions of the newfound sporulation genes, including two genes coding for proteins governing cell-to-cell signaling during the spore-formation process.