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This prospective, randomized, multicenter study demonstrated that quantitative clinical outcome measures following lumbar total disc replacement with the CHARITE artificial disc are at least equivalent to clinical outcomes with anterior lumbar interbody fusion. These results support earlier reports in the literature that total disc replacement with the CHARITE artificial disc is a safe and effective alternative to fusion for the surgical treatment of symptomatic disc degeneration in properly indicated patients. The CHARITE artificial disc group demonstrated statistically significant superiority in two major economic areas, a 1-day shorter hospitalization, and a lower rate of reoperations (5.4% compared with 9.1%). At 24 months, the investigational group had a significantly higher rate of satisfaction (73.7%) than the 53.1% rate of satisfaction in the control group (P = 0.0011). This prospective randomized multicenter study also demonstrated an increase in employment of 9.1% in the investigational group and 7.2% in the control group.

T he late Nobel laureate Richard Smalley often said that "energy is the single greatest challenge facing humanity." Energy needs in the U.S. and the world continue to increase, driving demand at an unsustainable pace. Possible options are carbon-based alternatives to oil, such as methane hydrates and the conversion of coal into methane gas, and the use of less readily available oil reservoirs and oil shale. But do we really want to use these fuels? Climate change is being driven by the atmospheric release of greenhouse gases like CO 2 (1), and an impending global energy crisis is coming at a time when we can least afford to release additional stored carbon. Nuclear power offers a carbon-free approach to energy generation, but no good solutions for nuclear waste exist. Perhaps Smalley should have said that energy is the single greatest environmental challenge facing humanity.

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Comparative 16S rRNA sequencing was used to evaluate phylogenetic relationships among selected strains of ammonia-and nitrite-oxidizing bacteria. All characterized strains were shown to be affiliated with the proteobacteria. The study extended recent 16S rRNA-based studies of phylogenetic diversity among nitrifiers by the comparison of eight strains of the genus Nitrobacter and representatives of the genera Nitrospira and Nitrospina. The later genera were shown to be affiliated with the delta subdivision of the proteobacteria but did not share a specific relationship to each other or to other members of the delta subdivision. All characterized Nitrobacter strains constituted a closely related assemblage within the alpha subdivision of the proteobacteria. As previously observed, all ammonia-oxidizing genera except Nitrosococcus oceanus constitute a monophyletic assemblage within the beta subdivision of the proteobacteria. Errors in the 16S rRNA sequences for two strains previously deposited in the databases by other investigators (Nitrosolobus multiformis C-71 and Nitrospira briensis C-128) were corrected. Consideration of physiology and phylogenetic distribution suggested that nitrite-oxidizing bacteria of the alpha and gamma subdivisions are derived from immediate photosynthetic ancestry. Each nitrifier retains the general structural features of the specific ancestor's photosynthetic membrane complex. Thus, the nitrifiers, as a group, apparently are not derived from an ancestral nitrifying phenotype.Biologists have been asking questions concerning the evolutionary origins of, and phylogenetic relationships among, chemolithotrophic microorganisms for well over a century. However, it has been only in the last decade that comparative molecular studies have provided the basis to shape an understanding of their phylogeny. Most notably, the use of comparative rRNA sequencing has provided an all-encompassing phylogenetic framework within which all the chemolithotrophs can be placed. The emerging phylogeny has, in turn, provided insights into their antiquity and the origins of lithotrophic metabolism. For example, sulfur oxidation and iron oxidation appear to be evolutionarily early and widespread metabolic modes that are not confined to a single phylogenetic assemblage of bacteria (27). An University, Evanston, with secondary consideration of cell shape and the highly characteristic cytoplasmic membrane structures (46). All known ammonia-oxidizing bacteria are obligate chemolithoautotrophs. In contrast, some nitrite-oxidizing bacteria are mixotrophs and also can grow heterotrophically (4, 26). Although the existing taxonomy assigns these bacteria to a single family, accumulating biochemical and molecular data do not support their phylogenetic coherence.Physiological and enzymatic data argue against a close relatedness between ammonia and nitrite oxidizers. They employ two very different key enzyme systems for the energygaining oxidation of ammonia and nitrite (5). Comparative sequencing studies based on 16S rRNA oli...