Manipulation of the seagrass-associated microbiome reduces disease severity

Host-associated microbes influence host health and function and can be a first line of defence against infections. While research increasingly shows that terrestrial plant microbiomes contribute to bacterial, fungal, and oomycete disease resistance, no comparable experimental work has investigated marine plant microbiomes or more diverse disease agents. We test the hypothesis that the eelgrass (Zostera marina) leaf microbiome increases resistance to seagrass wasting disease. From field eelgrass with paired diseased and asymptomatic tissue, 16S rRNA gene amplicon sequencing revealed that bacterial composition and richness varied markedly between diseased and asymptomatic tissue in one of the two years. This suggests that the influence of disease on eelgrass microbial communities may vary with environmental conditions. We next experimentally reduced the eelgrass microbiome with antibiotics and bleach, then inoculated plants with Labyrinthula zosterae, the causative agent of wasting disease. We detected significantly higher disease severity in eelgrass with a native microbiome than an experimentally reduced microbiome. Our results over multiple experiments do not support a protective role of the eelgrass microbiome against L. zosterae. Further studies of these marine host–microbe–pathogen relationships may continue to show new relationships between plant microbiomes and diseases.     

Arctic ground squirrel neuronal progenitor cells resist oxygen and glucose deprivation-induced death

AIM: To investigate the influence of ischemia/reperfusion on arctic ground squirrel(AGS) neuronal progenitor cells(NPCs), we subjected these cultured cells to oxygen and glucose deprivation.METHODS: AGS NPCs were expanded and differentiated into NPCs and as an ischemia vulnerable control, commercially available human NPCs(hNPCs) were seeded from thawed NPCs. NPCs, identified by expression of TUJ1 were seen at 14-21 d in vitro(DIV). Cultures were exposed to control conditions, hypoxia, oxygen and glucose deprivation or glucose deprivation alone or following return to normal conditions to model reperfusion. Cell viability and death were assessed from loss of ATP as well as from measures of alamarB lue~ and lactate dehydrogenase in the media and from counts of TUJ1 positive cells using immunocytochemistry. Dividing cells were identified by expression of Ki67 and phenotyped by double labeling with GFAP, MAP2 ab or TUJ1. RESULTS: We report that when cultured in NeuraLife~(TM), AGS cells remain viable out to 21 DIV, continue to express TUJ1 and begin to express MAP2 ab. Viability of hN PCs assessed by fluorescence alamarB lue(arbitrary units) depends on both glucose and oxygen availability [viability of hNPCs after 24 h oxygen glucose deprivation(OGD) with return of oxygen and glucose decreased from 48151 ± 4551 in control cultures to 43481 ± 2413 after OGD, P 0.05]. By contrast, when AGS NPCs are exposed to the same OGD with reperfusion at 14 DIV, cell viability assessed by alamar Blue increased from 165305 ± 11719 in control cultures to 196054 ± 13977 after OGD. Likewise AGS NPCs recovered ATP(92766 ± 6089 in control and 92907 ± 4290 after modeled reperfusion; arbitrary luminescence units), and doubled in the ratio of TUJ1 expressing neurons to total dividing cells(0.11 ± 0.04 in control cultures vs 0.22 ± 0.2 after modeled reperfusion, P 0.05). Maintaining AGS NPCs for a longer time in culture lowered resistance to injury, however, did not impair proliferation of NPCs relative to other cell lineages after oxygen deprivation followed by re-oxygenation.CONCLUSION: Ischemic-like insults decrease viability and increase cell death in cultures of human NPCs. Similar conditions have less affect on cell death and promote proliferation in AGS NPCs.     

Experimental study of solute transport and extraction by a single root in soil

The fate of ¹⁴C-2,4,6-trinitrotoluene ([U-¹⁴C]TNT) in soil/plant systems was studied using onion (Allium cepa L.) plants with only a single root. It was found that the single roots grew exponentially and that the rate of water uptake of the onion plants increased exponentially, as well. The concentration of [U-¹⁴C] in the roots at first increased and then appeared to reach a steady state, while the [U-¹⁴C] concentration in the leaves was found to increase linearly with time. The [U-¹⁴C] concentration in the rhizosphere increased gradually, while in the bulk soil it decreased slowly. The accumulation of [U-¹⁴C] in the rhizosphere is likely to difference between movement into the rhizosphere (through advective mass flow of soil water by root uptake) and its uptake into the roots. The distribution of ¹⁴C in the soil/plant system was found to be 60–85% in the soil solid phase, 7–11% in the soil liquid phase, <1% in the soil air phase, <1% in the root compartment, and <0.01% in the leaf compartment. The maximum RCF (root concentration factor) value for TNT and its derivates was found to be about 20, and the maximum TSCF (transpiration stream concentration factor) was 0.18. These values can be changed by a variety of factors in soil-plant systems     

An integrated system for studying residue coevolution in proteins

Residue coevolution has recently emerged as an important concept, especially in the context of protein structures. While a multitude of different functions for quantifying it have been proposed, not much is known about their relative strengths and weaknesses. Also, subtle algorithmic details have discouraged implementing and comparing them. We addressed this issue by developing an integrated online system that enables comparative analyses with a comprehensive set of commonly used scoring functions, including Statistical Coupling Analysis (SCA), Explicit Likelihood of Subset Variation (ELSC), mutual information and correlation-based methods. A set of data preprocessing options are provided for improving the sensitivity and specificity of coevolution signal detection, including sequence weighting, residue grouping and the filtering of sequences, sites and site pairs. A total of more than 100 scoring variations are available. The system also provides facilities for studying the relationship between coevolution scores and inter-residue distances from a crystal structure if provided, which may help in understanding protein structures. AVAILABILITY: The system is available at http://coevolution.gersteinlab.org. The source code and JavaDoc API can also be downloaded from the web site.     

Why equalising trade-offs aren't always neutral

Equalising trade-offs, such as seed mass vs. number, have been invoked to reconcile neutral theory with observed differences between species. This is an appealing explanation for the dramatic seed size variation seen within guilds of otherwise similar plants: under size-symmetric competition, where resource capture is proportional to mass, the outcome of competition should be insensitive to whether species produce many small seeds or few large ones. However, under this assumption, stochastic variation in seed rain leads to exclusion of all but the smallest-seeded species. Thus stochasticity in seed arrivals, a process that was previously thought to generate drift, instead results in deterministic competitive exclusion. A neutral outcome is possible under one special case of a more general equalising framework, where seed mass affects survival but not competition. Further exploration of the feasibility of neutral trade-offs is needed to understand the respective roles of neutrality and niche structure in community dynamics.     

The trophic history of Myall Lakes,New South Wales,Australia: interpretations using δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N of the sedimentary record

In an attempt to determine the trophic history of the Myall Lakes complex (New South Wales, Australia) δ¹³C_org, δ¹⁵N and C_org:N profiles were determined for bulk organic matter of two short sediment cores from Bombah Broadwater and Myall Lake. ²¹⁰Pb profiles and sediment types indicate significantly different trophic trajectories during the time periods examined. δ¹³C_org and C_org:N indicate Bombah Broadwater has been dominated by increasing inputs of terrestrial organic material over the last century, thought to be related to watershed disturbance including agricultural activity. Primary production appears to be dominated by phytoplankton. δ¹⁵N remained relatively stable at around 1‰ until the mid–1970s when there was a sharp increase to 4.7‰, interpreted as an influx of sewage-derived material. These observations offer an insight into the recent trophic changes at the site. Sedimentation rates are noticeably lower in Myall Lake and the most recent sediment is a flocculent organic rich deposit overlying mineral clay. δ¹³C_org and C_org:N values indicate a transition from plankton to macrophyte dominated primary production around 1800AD. δ¹⁵N values become increasingly negative from approximately 1900AD. This is interpreted as being due to increasing reliance by macrophytes on nitrogen recycled from decomposing sediments driven by natural infilling and eutrophication in this basin. The contrasting sedimentation rates, sediment types and geochemical profiles suggest the different basins of this water body are subject to substantially different internal and external influences which should be considered in management decisions.     

A hemiacetalate complex of Ru(II)

Reaction of cis-Ru(bisox)₂Cl₂, where bisox is 4,4,4′,4′-tetramethyl-2,2′-bisoxazoline, with excess of pyridine-2-carboxaldehyde (py-2-al) in 1:1 (v/v) methanol-water mixture under nitrogen atmosphere and subsequent addition of excess of NH₄PF₆ give [Ru(bisox)₂(py-2-al)](PF₆)₂ · H₂O (1). Refluxing of 1 in dehydrated methanol in presence of triethylamine yields the corresponding hemiacetalate complex: [Ru(bisox)₂ (pyridine-2-(α-methoxymethanolato))]PF₆ · 1.5H₂O (2). Both the complexes have been characterised by single crystal X-ray crystallography, FTIR and NMR. In cyclic voltammetry in acetonitrile at a glassy carbon electrode, 2 displays a quasireversible Ru(II/III) couple at 1.08 V versus NHE which is not observed in 1. A tentative mechanism is proposed for the conversion of 1 to 2. DFT calculations with the LanL2DZ basis set have been performed to investigate these observations theoretically.     

Ligand effects in cis-Ru(N-N)2L2 species where N-N is a substituted 2,2′-bisoxazoline and L is monodentate

Starting from previously reported cis-Ru(MeL)₂Cl₂, where MeL is 4,4,4′,4′-tetramethyl-2,2′-bisoxazoline, cis-Ru(MeL)₂Br₂ (1), cis-Ru(MeL)₂I₂ (2), cis-Ru(MeL)₂(NCS)₂ · H₂O (3), cis-Ru(MeL)₂(N₃)₂ (4) and cis-[Ru(MeL)₂(MeCN)₂](PF₆)₂ · (CH₃)₂CO (5) are synthesised. The X-ray crystal structures of complexes 1, 2, 3 and 5 have been determined. All the five new complexes have been characterized by FTIR, ESIMS and ¹H NMR. In cyclic voltammetry in acetonitrile at a glassy carbon electrode, the complexes display a quasireversible Ru(II/III) couple in the range 0.32-1.71 V versus NHE. The Ru(II/III) potentials yield a satisfactorily linear correlation with Chatt’s ligand constants P_L for the monodantate ligands. From the intercept and by comparing the known situation in Ru(2,2′-bipyridine)₂L₂, it is concluded that MeL, a non-aromatic diimine, is significantly more π-acidic than 2,2′-bipyridine.