Bioavailability of Mineral-Bound Iron to a Snow Algal-Bacterial Coculture and Implications for Albedo-Altering Snow Algal Blooms.

Snow algae can form large-scale blooms across the snowpack surface and near-surface environments. These pigmented blooms can decrease snow albedo and increase local melt rates, and they may impact the global heat budget and water cycle. Yet, the underlying causes for the geospatial occurrence of these blooms remain unconstrained. One possible factor contributing to snow algal blooms is the presence of mineral dust as a micronutrient source. We investigated the bioavailability of iron (Fe)-bearing minerals, including forsterite (Fo90, Mg1.8Fe0.2SiO4), goethite, smectite, and pyrite as Fe sources for a Chloromonas brevispina-bacterial coculture through laboratory-based experimentation. Fo90 was capable of stimulating snow algal growth and increased the algal growth rate in otherwise Fe-depleted cocultures. Fo90-bearing systems also exhibited a decrease in the ratio of bacteria to algae compared to those of Fe-depleted conditions, suggesting a shift in microbial community structure. The C. brevispina coculture also increased the rate of Fo90 dissolution relative to that of an abiotic control. Analysis of 16S rRNA genes in the coculture identified Gammaproteobacteria, Betaproteobacteria, and Sphingobacteria, all of which are commonly found in snow and ice environments. Archaea were not detected. Collimonas and Pseudomonas, which are known to enhance mineral weathering rates, comprised two of the top eight (>1%) operational taxonomic units (OTUs). These data provide unequivocal evidence that mineral dust can support elevated snow algal growth under otherwise Fe-depleted growth conditions and that snow algal microbial communities can enhance mineral dissolution under these conditions.IMPORTANCE Fe, a key micronutrient for photosynthetic growth, is necessary to support the formation of high-density snow algal blooms. The laboratory experiments described herein allow for a systematic investigation of the interactions of snow algae, bacteria, and minerals and their ability to mobilize and uptake mineral-bound Fe. Results provide unequivocal and comprehensive evidence that mineral-bound Fe in Fe-bearing Fo90 was bioavailable to Chloromonas brevispina snow algae within an algal-bacterial coculture. This evidence includes (i) an observed increase in snow algal density and growth rate, (ii) decreased ratios of bacteria to algae in Fo90-containing cultures relative to those of cultures grown under similarly Fe-depleted conditions with no mineral-bound Fe present, and (iii) increased Fo90 dissolution rates in the presence of algal-bacterial cocultures relative to those of abiotic mineral controls. These results have important implications for the role of mineral dust in supplying micronutrients to the snow microbiome, which may help support dense snow algal blooms capable of lowering snow albedo and increasing snow melt rates on regional, and possibly global, scales.

Perceptions of family-centred services in a paediatric rehabilitation programme: strengths and complexities from multiple stakeholders.

BACKGROUND: Family-centred services (FCS) are best practice in paediatric rehabilitation and describe philosophies and approaches to medical care that emphasize the partnership and involvement of parents. While evidence supports FCS, there are complexities to its successful implementation. This mixed-methods study aimed to measure the extent to which parents and the healthcare provider (HCP) perceive service provision as being family centred, and to describe barriers and facilitators to the delivery of FCS. METHODS: Parents of children participating in a rehabilitation programme and HCPs providing services participated in this study. Parents completed the measure of processes of care-20 and participated in interviews, while HCPs completed the measure of processes of care-service providers and participated in a focus group. RESULTS: Quantitative analysis revealed that parents were mostly satisfied with features of FCS, which included communication and support between parents and HCPs, respect of diversity and parental collaboration and participation. Parents identified communication methods and psychosocial needs as areas that facilitated but sometimes detracted from FCS. Institutional barriers led to the identification of areas for improvement identified by multiple stakeholders. HCPs identified more areas for improvement than parents. CONCLUSION: When considering these barriers, it is evident that implementation is a complex process, impacted by institutional barriers. FCS needs to be investigated further, and systemic interventions should be used to facilitate its implementation.

Pronounced summer to winter differences and higher wintertime richness in coastal Antarctic marine bacterioplankton.

Marine bacterioplankton studies over the annual cycle in polar systems are limited due to logistic constraints in site access and support. Here, we conducted a comparative study of marine bacterioplankton sampled at several time points over the annual cycle (12 occasions each) at sub-Antarctic Kerguelen Islands (KI) and Antarctic Peninsula (AP) coastal sites in order to establish a better understanding of the extent and nature of variation in diversity and community structure at these different latitudes (49-64S). Molecular methods targeting the 16S rRNA gene (DGGE, CE-SSCP and tag pyrosequencing) suggest a strong seasonal pattern with higher richness in winter and a clear influence of phytoplankton bloom events on bacterioplankton community structure and diversity in both locations. The distribution of sequence tags within Gammaproteobacteria, Alphaproteobacteria and Bacteriodetes differed between the two regions. At both sites, several abundant Rhodobacteraceae, uncultivated Gammaproteobacteria and Bacteriodetes-associated tags displayed intense seasonal variation often with similar trends at both sites. This enhanced understanding of variability in dominant groups of bacterioplankton over the annual cycle contributes to an expanding baseline to understand climate change impacts in the coastal zone of polar oceans and provides a foundation for comparison with open ocean polar systems.

The origin recognition complex, SIR1, and the S phase requirement for silencing.

Silencing of transcription in Saccharomyces cerevisiae has several links to DNA replication, including a role for the origin recognition complex (ORC), the DNA replication initiator, in both processes. In addition, the establishment of silencing at the HML and HMR loci requires cells to pass through the S phase of the cell cycle. Passage through S phase was required for silencing of HMR even under conditions in which ORC itself was no longer required. The requirement for ORC in silencing of HMR could be bypassed by tethering the Sir1 protein to the HMR-E silencer. However, ORC had a Sir1-independent role in transcriptional silencing at telomeres. Thus, the role of ORC in silencing was separable from its role in initiation, and the role of S phase in silencing was independent of replication initiation at the silencers.

Separation of origin recognition complex functions by cross-species complementation.

Transcriptional silencing at the HMRa locus of Saccharomyces cerevisiae requires the function of the origin recognition complex (ORC), the replication initiator of yeast. Expression of a Drosophila melanogaster Orc2 complementary DNA in the yeast orc2-1 strain, which is defective for replication and silencing, complemented the silencing defect but not the replication defect; this result indicated that the replication and silencing functions of ORC were separable. The orc2-1 mutation mapped to the region of greatest homology between the Drosophila and yeast proteins. The silent state mediated by DmOrc2 was epigenetic; it was propagated during mitotic divisions in a relatively stable way, whereas the nonsilent state was metastable. In contrast, the silent state was erased during meiosis.

Cross-disciplinarity in the advance of Antarctic ecosystem research.

The biodiversity, ecosystem services and climate variability of the Antarctic continent and the Southern Ocean are major components of the whole Earth system. Antarctic ecosystems are driven more strongly by the physical environment than many other marine and terrestrial ecosystems. As a consequence, to understand ecological functioning, cross-disciplinary studies are especially important in Antarctic research. The conceptual study presented here is based on a workshop initiated by the Research Programme Antarctic Thresholds - Ecosystem Resilience and Adaptation of the Scientific Committee on Antarctic Research, which focussed on challenges in identifying and applying cross-disciplinary approaches in the Antarctic. Novel ideas and first steps in their implementation were clustered into eight themes. These ranged from scale problems, through risk maps, and organism/ecosystem responses to multiple environmental changes and evolutionary processes. Scaling models and data across different spatial and temporal scales were identified as an overarching challenge. Approaches to bridge gaps in Antarctic research programmes included multi-disciplinary monitoring, linking biomolecular findings and simulated physical environments, as well as integrative ecological modelling. The results of advanced cross-disciplinary approaches can contribute significantly to our knowledge of Antarctic and global ecosystem functioning, the consequences of climate change, and to global assessments that ultimately benefit humankind.

Chemodenitrification in the cryoecosystem of Lake Vida, Victoria Valley, Antarctica.

Lake Vida, in the Victoria Valley of East Antarctica, is frozen, yet harbors liquid brine (~20% salt, >6 times seawater) intercalated in the ice below 16 m. The brine has been isolated from the surface for several thousand years. The brine conditions (permanently dark, -13.4 °C, lack of O2 , and pH of 6.2) and geochemistry are highly unusual. For example, nitrous oxide (N2 O) is present at a concentration among the highest reported for an aquatic environment. Only a minor 17 O anomaly was observed in N2 O, indicating that this gas was predominantly formed in the lake. In contrast, the 17 O anomaly in nitrate (NO3-) in Lake Vida brine indicates that approximately half or more of the NO3- present is derived from atmospheric deposition. Lake Vida brine was incubated in the presence of 15 N-enriched substrates for 40 days. We did not detect microbial nitrification, dissimilatory reduction of NO3- to ammonium (NH4+), anaerobic ammonium oxidation, or denitrification of N2 O under the conditions tested. In the presence of 15 N-enriched nitrite (NO2-), both N2 and N2 O exhibited substantial 15 N enrichments; however, isotopic enrichment declined with time, which is unexpected. Additions of 15 N-NO2- alone and in the presence of HgCl2 and ZnCl2 to aged brine at -13 °C resulted in linear increases in the δ15 N of N2 O with time. As HgCl2 and ZnCl2 are effective biocides, we interpret N2 O production in the aged brine to be the result of chemodenitrification. With this understanding, we interpret our results from the field incubations as the result of chemodenitrification stimulated by the addition of 15 N-enriched NO2- and ZnCl2 and determined rates of N2 O and N2 production of 4.11-41.18 and 0.55-1.75 nmol L-1  day-1 , respectively. If these rates are representative of natural production, the current concentration of N2 O in Lake Vida could have been reached between 6 and 465 years. Thus, chemodenitrification alone is sufficient to explain the high levels of N2 O present in Lake Vida.

The role of Sas2, an acetyltransferase homologue of Saccharomyces cerevisiae, in silencing and ORC function.

Silencing at the cryptic mating-type loci HML and HMR of Saccharomyces cerevisiae requires regulatory sites called silencers. Mutations in the Rap1 and Abf1 binding sites of the HMR-E silencer (HMRa-e**) cause the silencer to be nonfunctional, and hence, cause derepression of HMR. Here, we have isolated and characterized mutations in SAS2 as second-site suppressors of the silencing defect of HMRa-e**. Silencing conferred by the removal of SAS2 (sas2 delta) depended upon the integrity of the ARS consensus sequence of the HMR-E silencer, thus arguing for an involvement of the origin recognition complex (ORC). Restoration of silencing by sas2 delta required ORC2 and ORC5, but not SIR1 or RAP1. Furthermore, sas2 delta suppressed the temperature sensitivity, but not the silencing defect of orc2-1 and orc5-1. Moreover, sas2 delta had opposing effects on silencing of HML and HMR. The putative Sas2 protein bears similarities to known protein acetyltransferases. Several models for the role of Sas2 in silencing are discussed.

A role for the replication proteins PCNA, RF-C, polymerase epsilon and Cdc45 in transcriptional silencing in Saccharomyces cerevisiae.

Transcriptional silencing in the budding yeast Saccharomyces cerevisiae may be linked to DNA replication and cell cycle progression. In this study, we have surveyed the effect of 41 mutations in genes with a role in replication, the cell cycle, and DNA repair on silencing at HMR. Mutations in PCNA (POL30), RF-C (CDC44), polymerase epsilon (POL2, DPB2, DPB11), and CDC45 were found to restore silencing at a mutant HMR silencer allele that was still a chromosomal origin of replication. Replication timing experiments indicated that the mutant HMR locus was replicated late in S-phase, at the same time as wild-type HMR. Restoration of silencing by PCNA and CDC45 mutations required the origin recognition complex binding site of the HMR-E silencer. Several models for the precise role of these replication proteins in silencing are discussed.

Handwashing in the intensive care unit: a big measure with modest effects.

Handwashing is widely accepted as the cornerstone of infection control in the intensive care unit. Nosocomial infections are frequently viewed as an indicator of poor compliance of handwashing. The aim of this review is to evaluate the effectiveness of handwashing on infection rates in the intensive care unit, and to analyse the failure of handwashing. A literature search identified nine studies that evaluated the impact of handwashing or hand hygiene on infection rates, and demonstrated a low level of evidence for the efforts to control infection with handwashing. Poor compliance cannot be blamed as the only reason for the failure of handwashing to control infection. Handwashing on its own does not abolish, but only reduces transmission, as it is dependent on the bacterial load on the hand of healthcare workers. Finally, recent studies, using surveillance cultures of throat and rectum, have shown that, under ideal circumstances, handwashing can only influence 40% of all intensive care unit infections. A randomised clinical trial with the intensive care as randomisation unit is required to support handwashing as the cornerstone of infection control.

Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska.

The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH4 production experiments, and copy number of a methanogenic pathway-specific gene (mcrA) indicated the existence of different sources of CH4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH4 production in Siqlukaq at moderate levels, while the very low levels of CH4 detected in Sukok had a mixed origin, with little to no biological CH4 production. Furthermore, methanogenic archaea exhibited temperature-dependent use of in situ substrates for methanogenesis, and the amount of CH4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH4 from thermokarst lakes on the coastal plain of Alaska to the current CH4 budgets.

Blood transfusion-associated Pseudomonas fluorescens septicaemia: is this an increasing problem?

Pseudomonas fluorescens transfusion-related septicaemia (TRS) is rare. We present the first description in the UK of two cases of TRS caused by this organism.

Mycoplasma hominis as a respiratory pathogen in X-linked hypogammaglobulinaemia.

We report a case of lower respiratory tract infection with Mycoplasma hominis in a patient with X-linked hypogammaglobulinaemia.

A review of Campylobacter pylori in upper gastrointestinal disease.

The organism Campylobacter pylori is frequently found in association with gastritis and peptic ulcer disease. Whether it is the cause, a contributory factor or a simple commensal is not known but there is evidence to support a pathological role. Current research may alter our understanding of the causes of upper gastrointestinal disease and have important implications for treatment.

Relationship between Photoconvertible and Nonphotoconvertible Protochlorophyllides.

Two forms of protochlorophyllide are found in dark-grown bean (Phaseolus vulgaris, var. Black Velentine) leaves, one (protochlorophyllide(650)) which is directly photoconvertible to chlorophyllide and another (protochlorophyllide(632)) which is not. Dark-grown leaves placed in solutions of delta-aminolevulinic acid accumulate protochlorophyllide(632). Protochlorophyllide(650) and protochlorophyllide(632) can be partially separated on sucrose density gradients. A nitrogen atmosphere blocks chlorophyll synthesis in light or the regeneration of protochlorophyllide(650) in the dark, even in the presence of excess delta-aminolevulinic acid, except when a stockpile of protochlorophyllide(632) is present in the leaf. Under the latter conditions chlorophyll synthesis or protochlorophyllide(650) regeneration is accompanied by a decrease in protochlorophyllide(632). These experiments suggest that protochlorophyllide(632) may be converted to protochlorophyllide(650).Cycloheximide inhibited greening only after an "action-dependent" delay, requiring a predictable minimal period of illumination. This inhibition could be relieved for a time by feeding delta-aminolevulinic acid.