Ferritin is used for iron storage in bloom-forming marine pennate diatoms.

Primary productivity in 30-40% of the world's oceans is limited by availability of the micronutrient iron. Regions with chronically low iron concentrations are sporadically pulsed with new iron inputs by way of dust or lateral advection from continental margins. Addition of iron to surface waters in these areas induces massive phytoplankton blooms dominated primarily by pennate diatoms. Here we provide evidence that the bloom-forming pennate diatoms Pseudo-nitzschia and Fragilariopsis use the iron-concentrating protein, ferritin, to safely store iron. Ferritin has not been reported previously in any member of the Stramenopiles, a diverse eukaryotic lineage that includes unicellular algae, macroalgae and plant parasites. Phylogenetic analyses suggest that ferritin may have arisen in this small subset of diatoms through a lateral gene transfer. The crystal structure and functional assays of recombinant ferritin derived from Pseudo-nitzschia multiseries reveal a maxi-ferritin that exhibits ferroxidase activity and binds iron. The protein is predicted to be targeted to the chloroplast to control the distribution and storage of iron for proper functioning of the photosynthetic machinery. Abundance of Pseudo-nitzschia ferritin transcripts is regulated by iron nutritional status, and is closely tied to the loss and recovery of photosynthetic competence. Enhanced iron storage with ferritin allows the oceanic diatom Pseudo-nitzschia granii to undergo several more cell divisions in the absence of iron than the comparably sized, oceanic centric diatom Thalassiosira oceanica. Ferritin in pennate diatoms probably contributes to their success in chronically low-iron regions that receive intermittent iron inputs, and provides an explanation for the importance of these organisms in regulating oceanic CO(2) over geological timescales.

Antibiotic exposure in hospitalized pediatric patients in the United States: prevalence and length of stay.

BACKGROUND: Hospital antibiotic use is rising. We aimed to evaluate the antibiotic-use prevalence and length of stay. METHODS: We conducted a single-center retrospective study of patients < 18-years-old admitted to general pediatric services who received ≥ 1 antibiotic over six months. Demographics, culture results and antibiotic details were collected. The primary outcome was to identify the total number and classes of antibiotics prescribed during the admission. Secondary outcomes included length of stay (LOS), culture results, and the most commonly used antibiotics. RESULTS: Forty-eight percent of patients received monotherapy (single class antibiotic). Cephalosporins (55%), vancomycin (35%), and clindamycin (22%) were prescribed more commonly than other antibiotic classes. Children were exposed up to 4 classes of antibiotics (range 1-4). A moderate correlation existed between the length of stay and the number of antibiotic classes used (R2 = 0.38). Two or more classes of antibiotic use prolonged the length of stay. Cephalosporin use was associated with 35% reduced LOS (95 CI, 21%-57%), and penicillin use correlated with 38% more prolonged LOS (95 CI, 22%-66%). CONCLUSIONS: Antibiotic use in pediatric hospitals was high, and children received multiple classes of antibiotics. Inappropriate antibiotic use and culture results may have an untoward effect on hospital length of stay.

Metapopulation Structure in the Planktonic Diatom Ditylum brightwellii (Bacillariophyceae).

Approximately 200,000 diatom species are thought to exist and yet the underlying processes of speciation in diatoms are unknown. Because genetic subdivision within species can reveal potential speciation mechanisms, we examined genetic differentiation and patterns of gene flow among four populations of the diatom Ditylum brightwellii. Single-cell isolates were examined at two microsatellite markers and two rDNA loci (18S and internal transcribed spacer region I (ITSI)). Among isolates, rDNA sequences varied by 0.08+/-0.04% (18S) and 0.7+/-0.3% (ITSI) and there were no compensatory base pair changes in the predicted ITSI secondary structure, all suggesting that a single species was represented. Two numerically dominant ITSI sequence types were detected and their distribution among isolates from genetically distinct populations was significantly different. Two populations shared ITSI sequence type 1 and two shared ITSI sequence type 2, indicating differences in relatedness among populations. The signature of unequal gene flow among populations suggested that D. brightwellii exhibited a metapopulation structure: the species was subdivided into populations of populations. The identification of metapopulations suggests a possible mechanism of speciation through reduced levels of gene flow, providing newly evolved taxa with a large repository of genetic and physiological diversity and perhaps significant adaptive potential.

Clostridium difficile Infection and Proton Pump Inhibitor Use in Hospitalized Pediatric Cystic Fibrosis Patients.

Children with cystic fibrosis (CF) often take proton pump inhibitors (PPIs), which helps improve efficacy of fat absorption with pancreatic enzyme replacement therapy. However, PPI use is known to be associated with Clostridium difficile-(C. diff-) associated diarrhea (CDAD). We retrospectively evaluated the incidence of C. diff infection from all pediatric hospital admissions over a 5-year period at a single tertiary children's hospital. We found significantly more C. diff-positive stool tests in hospitalized patients with CF compared to patients with no diagnosis of CF. However, use of a PPI was not associated with an increased risk of CDAD in hospitalized CF patients. In summary, C. diff infection is more common in hospitalized pediatric CF patients although PPI use may not be a risk factor for CDAD development in this patient population.