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Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T. pseudonana to clarify evolutionary origins, functional significance and ubiquity of these features throughout diatoms. In spite of the fact that the pennate and centric lineages have only been diverging for 90 million years, their genome structures are dramatically different and a substantial fraction of genes ( approximately 40%) are not shared by these representatives of the two lineages. Analysis of molecular divergence compared with yeasts and metazoans reveals rapid rates of gene diversification in diatoms. Contributing factors include selective gene family expansions, differential losses and gains of genes and introns, and differential mobilization of transposable elements. Most significantly, we document the presence of hundreds of genes from bacteria. More than 300 of these gene transfers are found in both diatoms, attesting to their ancient origins, and many are likely to provide novel possibilities for metabolite management and for perception of environmental signals. These findings go a long way towards explaining the incredible diversity and success of the diatoms in contemporary oceans.

Objective and Importance: Despite their predilection for sensory nerves, intracranial schwannomas have been reported in a number of mixed and purely motor cranial nerves, especially in association with Type 2 neurofibromatosis. We report the rare occurrence of a trochlear nerve schwannoma in a patient without neurofibromatosis and review 17 other case reports from the literature., Clinical Presentation: A 35-year-old woman presented with an 8-week history of evolving left hemiparesis, bilateral bulbar paresis, and out-of-character emotional lability., Intervention: She underwent a left temporal craniotomy and a subtemporal, transtentorial approach to the tentorial hiatus, with complete excision of a cisternal trochlear nerve schwannoma., Conclusion: Postoperative complications included temporary oculomotor and abducens nerve palsies and temporary right hemiparesis and mild expressive dysphasia, which were resolved at 23-month follow-up. Preoperative symptoms and signs completely resolved, but a postoperative complete trochlear nerve palsy required inferior oblique myectomy for correction of diplopia. A review of the literature showed no preoperative trochlear nerve involvement in at least 45% of cases. The tumor is isointense on T1- and T2-weighted magnetic resonance images and enhances brightly with gadolinium. The most frequently used approach for surgical excision is the subtemporal approach, and the tumor is almost always totally excised. Long-term follow-up suggests recovery of preoperative deficit, and persisting or new trochlear nerve palsy is the rule.