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This Week in Science: Jul 5, 2013

In Science this week, a multi-institute team of researchers describe the use of a new sequencing technique for analyzing human gut microbes, which enabled them to evaluate the long-term stability of these bacterial communities. With the method, called LEA-seq, the investigators sampled the fecal microbial community of 37 people, four of whom were participating in a 32-week liquid diet. They found that 60 percent of the bacterial strains sampled from the individuals remained steady for up to five years, with some believed to have persisted for decades. They also found that weight loss has a significant effect on microbial strain composition, indicating that changes in microbiome can potentially serve as a tool for evaluating host health.

Also in Science, scientists led by investigators from the Salk Institute for Biological Studies report the genome-wide composition, patterning, cell specificity, and dynamics of DNA methylation at single-base resolution in the brains of both humans and mice. By examining neurons at different stages of development — fetal, early postnatal, and adult — they mapped modifications resulting from specific types of DNA methylation. They were then able to use this map to uncover several features of methylation in the brain, such as the accumulation of highly conserved non-CG methylation in neurons. Overall, the work helps improves the understanding of how epigenetic modifications in the brain lead to a fully differentiated nervous system.