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This Week in Science: Sep 19, 2014

In Science this week, a trio of researchers from the University of California, Santa Cruz, and Indiana University report new data pointing to the importance of histones and related enzymes for maintaining the patterns of gene expression and repression necessary for proper development across generations. While it is known that the histone H3K27me is modified by the PRC2 protein complex, and that the two work together to inactivate specific genes in many organisms, how this repressed state is passed from mother to daughter cells is unclear. Using a Caenorhabditis elegans model, the researchers show that both sperm and egg cells transmit memory of chromatin repression to embryos using modified histones. During DNA replication, these modified histones are passed to daughter chromatids to provide chromatin memory for a few cell divisions. Meanwhile, histone-modifying enzymes replenish histone modifications and provide long-term chromatin memory.

And in Science Translational Medicine, investigators from the National Institutes of Health and Pacific Biosciences describe the use of long-read genome sequencing to reveal how certain bacteria use plasmids to develop resistance to antibiotics such as carbapenem. Over the course of two years, the researchers collected environmental samples and surveillance cultures from more than 1,000 patients at the NIH's clinical center, identifying 10 patients with carbapenem-resistant bacteria. By analyzing the bacteria's plasmid genomes, they found that plasmid-carrying bacteria were exchanging antibiotic-resistant genes in the biofilms of sink drains. While they found no evidence that the bacteria were transferred from the sink to patients, and they noted that patients carrying the bacteria might not become sick, these individuals were still capable of passing the antibiotic-resistant germs to others. GenomeWeb Daily News has more on this study here.