In situ quantification of fish‐cage fouling by underwater photography and image analysis

Close‐up underwater photography and image analysis were used to quantify mesh occlusion by biofouling of salmon‐cage netting. This technique allows fast, non‐destructive sampling of cages in situ for the determination of temporal and spatial changes in fouling. The area of net blockage can be easily determined, allowing rapid evaluation of cleaning or antifouling performance.     

Association of 25-Hydroxyvitamin D status and genetic variation in the vitamin D metabolic pathway with FEV1 in the Framingham Heart Study

Background

Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.

Methods

We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV₁) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV₁ in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV₁ in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.

Results

We found a positive cross-sectional association between 25(OH)D and FEV₁ in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV₁ in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV₁ (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV₁ in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).

Conclusions

Serum 25(OH)D status was associated with cross-sectional FEV₁, but not longitudinal change in FEV₁. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV₁ and is a promising candidate gene for further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users.     

Occurrence and Characterization of a Phosphoenolpyruvate: Glucose Phosphotransferase System in a Marine Bacterium, Serratia marinorubra

The mechanism of d-glucose transport in the marine bacterium Serratia marinorubra was investigated. Uptake is mediated by a single, constitutive phosphoenolpyruvate:sugar phosphotransferase system (PTS), resulting in phosphorylation of d-glucose to d-glucose phosphate during transport. The system is saturable (K(m) = 6.4 x 10 M) and highly temperature dependent, with a Q(10) of 3.5 between 5 and 15 degrees C. The system is highly specific for d-glucose; structurally related sugars and sugar alcohols did not significantly compete with d-glucose for transport. The PTS requires Mg (K(m) = 2.5 x 10 M), but its activity is otherwise unaffected by salinity changes over the range tested (0 to 35 per thousand). S. marinorubra differs from other gram-negative organisms (Escherichia coli and Salmonella typhimurium) in that its glycerol (non-PTS substrate) permease is not regulated by the presence of glucose (PTS substrate).     

Adaptation of model genetically engineered microorganisms to lake water: growth rate enhancements and plasmid loss.

When a genetically engineered microorganism (GEM) is released into a natural ecosystem, its survival, and hence its potential environmental impact, depends on its genetic stability and potential for growth under highly oligotrophic conditions. In this study, we compared plasmid stability and potential for growth on low concentrations of organic nutrients of strains of Pseudomonas putida serving as model GEMs. Plasmid-free and plasmid-bearing (NAH7) prototrophic isogenic strains and two amino-acid auxotrophs, all containing antibiotic resistance markers, were held physically separate from but in chemical contact with lake water containing the natural bacterium-sized microbial populations. Cells were reisolated at intervals over a 2-month period to determine the percent retaining the plasmid and the specific growth rate on various media. Plasmid stability in lake water was strongly strain specific; the NAH7 plasmid was stably maintained by the prototrophic strain for the duration of the test but was lost within 24 h by both of the auxotrophs. Specific growth rates of reisolates, compared with those of the corresponding non-lake water-exposed strains (i.e., parental strains), were not different when measured in rich medium (Luria-Bertani broth). However, specific growth rates were 42, 55, and 63% higher in reisolates of auxotrophs and the plasmid-free prototroph, respectively, when measured in 10-fold-diluted medium after exposure of 15 days or longer to lake water. Moreover, lake water-exposed strains grew actively when reintroduced into sterile lake water (28- to 33-fold increase in numbers over 7 days), while the corresponding unadapted parental strains exhibited no growth over the same period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Annual Cycle of Bacterial Secondary Production in Five Aquatic Habitats of the Okefenokee Swamp Ecosystem

Rates of bacterial secondary production by free-living bacterioplankton in the Okefenokee Swamp are high and comparable to reported values for a wide variety of marine and freshwater ecosystems. Bacterial production in the water column of five aquatic habitats of the Okefenokee Swamp was substantial despite the acidic (pH 3.7), low-nutrient, peat-accumulating character of the environment. Incorporation of [³H]thymidine into cold-trichloroacetic acid-insoluble material ranged from 0.03 to 2.93 nmol liter⁻¹ day⁻¹) and corresponded to rates of bacterial secondary production of 3.4 to 342.2 μg of carbon liter⁻¹ day⁻¹ (mean, 87.8 μg of carbon liter⁻¹ day⁻¹). Bacterial production was strongly seasonal and appeared to be coupled to annual changes in temperature and primary production. Bacterial doubling times ranged from 5 h to 15 days and were fastest during the warm months of the year, when the biomass of aquatic macrophytes was high, and slowest during the winter, when the plant biomass was reduced. The high rates of bacterial turnover in Okefenokee waters suggest that bacterial growth is an important mechanism in the transformation of dissolved organic carbon into the nutrient-rich bacterial biomass which is utilized by microconsumers.     

Regulation of the respiratory burst by cyclic 3',5'-AMP, an association with inhibition of arachidonic acid release.

The mechanism of cAMP regulation of the respiratory burst was studied with HL-60 cells that had been DMSO-differentiated to a neutrophil-like cell. To evaluate the effects of known cAMP concentrations, cells were permeabilized with streptolysin-O. Chemotactic peptide (FMLP)-stimulated NADPH oxidase activity was inhibited by cAMP at concentrations higher than 3 microM. Because intracellular calcium was buffered, inhibitory actions of cAMP were not mediated by modulation of calcium concentration. Effects of cAMP on chemotactic peptide signal transduction mediated by phospholipase C, phospholipase D, and phospholipase A2 were then determined. Neither inositol phosphate generation (phospholipase C) nor phosphatidylethanol generation (phospholipase D activity in presence of 1.6% ethanol) induced by FMLP were significantly affected by cAMP. In contrast, cAMP potently inhibited FMLP-induced arachidonic acid mobilization (phospholipase A2). NADPH oxidase activity induced by exogenous arachidonic acid was not inhibited by cAMP. These results indicate that cAMP-mediated inhibition of arachidonic acid mobilization may be important in regulation of the respiratory burst.     

Endocrine parameters associated with disruption of parturition after bilateral pelvic neurectomy.

Bilateral lesions of the pelvic nerve (BLPN) result in dystocia, but the processes which control this effect are not fully understood. Plasma progesterone, relaxin, and luteinizing hormone (LH) concentrations were measured in blood samples taken in the morning (AM) and evening (PM) of Days 20-23 of gestation from rats with BLPN or sham neurectomy. Ten of 11 sham-operated control animals delivered their entire litters by Day 23 of gestation, but animals with BLPN did not complete parturition by Day 23 when they were sacrificed. Progesterone concentrations were greater in rats with BLPN than in sham-operated rats on Day 20 PM and Day 21 AM, but hormone concentrations declined to minimal values by Day 22 in both groups. Relaxin concentrations were greater in rats with BLPN than in sham-operated rats on Day 21 PM. Thereafter, relaxin concentrations decreased to reach minimum values on Day 23 in both groups. LH concentrations were low throughout the period of study in rats with BLPN; however, a postpartum LH surge was detected in all sham-operated animals. Data from this study indicate that the pelvic nerve does not control parturition by modulating serum relaxin and progesterone concentrations; however, these data suggest that impulses carried by the pelvic nerve influence ovarian secretion of these hormones. In addition, these data indicate that the pelvic nerve transmits stimuli from the cervix to the hypothalamus to facilitate the postpartum LH surge.     

The effects of the interaction between salinity and nitrogen limitation in Agrostis stolonifera L.

Salt-tolerant Agrostis stolonifera ecotypes commonly grow on upper salt marshes, environments regarded as having a limited nitrogen supply. The interaction between salinity and nitrate supply limitation was studied in two ecotypes of A. stolonifera, one isolated from an upper salt marsh and one from an inland habitat. The ion, amino acid, glycine betaine and sugar contents of the two ecotypes were determined over a range of external salt concentrations and levels of nitrate supply. In vivo nitrate reductase activity was also measured. Several low molecular weight nitrogenous compounds accumulated in the salt-stressed plants. Nitrogen supply limitation had a great effect on the way in which the plants responded to salt stress. In particular, the concentrations of the soluble organic nitrogenous compounds were reduced. The results are discussed with respect to the salt marsh environment, and possible models for cytoplasmic osmoregulation are presented.Acknowledgements: One of us (MJH) gratefully acknowledges the receipt of a research studentship from the Science Research Council, U.K. We would also like to thank Mrs E. E. Griffiths for skilled technical assistance, and Dr I. Ahmad for help with the amino acid analysis.     

Aluminium/silicon interactions in barley (Hordeum vulgare L.) seedlings

The response of seedlings of the monocot Hordeum vulgare L. cv. Bronze to 0,25 and 50 M aluminium in factorial combination with 0, 1.4, 2.0 and 2.8 mM Si was tested in hydroponic culture at pH 4.5. Nutrient solution (500 M calcium nitrate) and Al/Si treatments were designed to avoid the precipitation of Al from solution. Silicon treatments gave significant amelioration of the toxic effects of Al on root and shoot growth and restored calcium levels in roots and shoots at harvest to levels approaching those of control plants. Aluminium uptake by roots was also significantly diminished in the presence of Si. Silicon alone gave a slight stimulation of growth, insufficient to explain its ameliorative effect on Al toxicity. The mechanism of the Si effect on Al toxicity in monocotyledons awaits further investigation.Abbreviations ICP inductively coupled plasma     

Taxon interactions control the distributions of cryoconite bacteria colonizing a High Arctic ice cap

Microbial colonization of glacial ice surfaces incurs feedbacks which affect the melting rate of the ice surface. Ecosystems formed as microbe–mineral aggregates termed cryoconite locally reduce ice surface albedo and represent foci of biodiversity and biogeochemical cycling. Consequently, greater understanding the ecological processes in the formation of functional cryoconite ecosystems upon glacier surfaces is sought. Here, we present the first bacterial biogeography of an ice cap, evaluating the respective roles of dispersal, environmental and biotic filtration occurring at local scales in the assembly of cryoconite microbiota. 16S rRNA gene amplicon semiconductor sequencing of cryoconite colonizing a Svalbard ice cap coupled with digital elevation modelling of physical parameters reveals the bacterial community is dominated by a ubiquitous core of generalist taxa, with evidence for a moderate pairwise distance–decay relationship. While geographic position and melt season duration are prominent among environmental predictors of community structure, the core population of taxa appears highly influential in structuring the bacterial community. Taxon co‐occurrence network analysis reveals a highly modular community structured by positive interactions with bottleneck taxa, predominantly Actinobacteria affiliated to isolates from soil humus. In contrast, the filamentous cyanobacterial taxon (assigned to Leptolyngbya/Phormidesmis pristleyi) which dominates the community and binds together granular cryoconite are poorly connected to other taxa. While our study targeted one ice cap, the prominent role of generalist core taxa with close environmental relatives across the global cryosphere indicate discrete roles for cosmopolitan Actinobacteria and Cyanobacteria as respective keystone taxa and ecosystem engineers of cryoconite ecosystems colonizing ice caps.