Comparing physiological responses to hot and cold stress in a cnidarian–algal holobiont, \u3ci\u3eExaiptasia diaphana\u3c/i\u3e

Coral bleaching—the breakdown of the cnidarian–algal symbiosis—is a major cause of reef decline. The sea anemone Exaiptasia diaphana, commonly known as Aiptasia, is used as a model to study cnidarian-algal symbiosis in laboratory settings. Aiptasia can live with or without symbionts, which allows scientists to study the host combined and separate from the influence of the symbionts. Scientists are able to trigger the breakdown of the symbiosis using heat or cold stress. Cold stress is more commonly used to render aposymbiotic Aiptasia because it seems to be less harmful to the host than bleaching under heat stress. Is cold really less harmful than heat stress? We compared hot and cold stress responses to different stress regiments: a gradual temperature change, a gradual temperature change followed by a sudden temperature change, and a sudden temperature change from ambient conditions. We explored multiple physiological responses of the anemones to determine their level of stress response. We measured mortality and algal density in the host, as well as carbohydrate in the host and symbiont fractions. We also measured peroxide production in algal cultures exposed to the same treatment regimes. After repeating the experiment twice, we found that anemones had different responses, which emphasizes the necessity for repeated experiments in research conducted with live subjects

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead