Widespread Distribution and Expression of Gamma A (UMB), an Uncultured, Diazotrophic, γ-Proteobacterial nifH Phylotype

Marine dinitrogen (N2) fixation studies have focused nearly exclusively on cyanobacterial diazotrophs; however γ-proteobacteria are an abundant component of the marine community and have been largely overlooked until recently. Here we present a phylogenetic analysis of all nifH γ-proteobacterial sequences available in public databases and qPCR data of a γ-proteobacterial phylotype, Gamma A (UMB), obtained during several research cruises. Our analysis revealed a complex diversity of diazotrophic γ-proteobacteria. One phylotype in particular, Gamma A, was described in several traditional and quantitative PCR studies. Though several γ-proteobacterial nifH sequences have been described as laboratory contaminants, Gamma A is part of a large cluster of sequences isolated from marine environments and distantly related to the clade of contaminants. Using a TaqMan probe and primer set, Gamma A nifH DNA abundance and expression were analyzed in nearly 1000 samples collected during 15 cruises to the Atlantic and Pacific Oceans. The data showed that Gamma A is an active, cosmopolitan diazotroph found throughout oxygenated, oligotrophic waters reaching maximum abundances of 8 × 104 nifH DNA copies l-1 and 5 × 105 nifH transcript copies l-1. Gamma A nifH transcript abundances were on average 3 fold higher than nifH DNA abundances. The widespread distribution and activity of Gamma A indicate that it has potential to be a globally important N2 fixing organism

Race and Surgical Mortality in the United States

OBJECTIVE: This study describes racial differences in postoperative mortality following 8 cardiovascular and cancer procedures and assesses possible explanations for these differences. SUMMARY BACKGROUND DATA: Although racial disparities in the use of surgical procedures are well established, relationships between race and operative mortality have not been assessed systematically. METHODS: We used national Medicare data to identify all patients undergoing one of 8 cardiovascular and cancer procedures between 1994 and 1999. We used multiple logistic regression to assess differences in operative mortality (death within 30 days or before discharge) between black patients and white patients, controlling for patient characteristics. Adding hospital indicators to these models, we then assessed the extent to which racial differences in operative mortality could be accounted for by the hospital in which patients were cared for. RESULTS: Black patients had higher crude mortality rates than white patients for 7 of the 8 operations, including coronary artery bypass, aortic valve replacement, abdominal aortic aneurysm repair, carotid endarterectomy, radical cystectomy, pancreatic resection, and esophagectomy. Among these 7 procedures, odds ratios of mortality (black versus white) ranged from 1.23 (95% confidence interval, 1.18–1.29) for CABG to 1.61 (95% confidence interval, 1.28–2.03) for esophagectomy. Adjusting for patient characteristics had modest or no effect on odds ratios of mortality by race. However, there remained few clinically or statistically significant differences in mortality by race after we accounted for hospital. Hospitals that treated a large proportion of black patients had higher mortality rates for all 8 procedures, for white as well as black patients. CONCLUSIONS: Black patients have higher operative mortality risks across a wide range of surgical procedures, in large part because of higher mortality rates at the hospitals they attend