Cell wall organic matrix composition and biomineralization across reef-building coralline algae under global change

Crustose coralline algae (CCA) are one of the most important benthic substrate consolidators on coral reefs through their ability to deposit calcium carbonate on an organic matrix in their cell walls. Discrete polysaccharides have been recognized for their role in biomineralization, yet little is known about the carbohydrate composition of organic matrices across CCA taxa and whether they have the capacity to modulate their organic matrix constituents amidst environmental change, particularly the threats of ocean acidification (OA) and warming. We simulated elevated pCO₂ and temperature (IPCC RCP 8.5) and subjected four mid-shelf Great Barrier Reef species of CCA to 2 months of experimentation. To assess the variability in surficial monosaccharide composition and biomineralization across species and treatments, we determined the monosaccharide composition of the polysaccharides present in the cell walls of surficial algal tissue and quantified calcification. Our results revealed dissimilarity among species' monosaccharide constituents, which suggests that organic matrices are composed of different polysaccharides across CCA taxa. We also observed that species differentially modulate composition in response to ocean acidification and warming. Our findings suggest that both variability in composition and ability to modulate monosaccharide abundance may play a crucial role in surficial biomineralization dynamics under the stress of OA and global warming.     

Formation of the prismatic layer in the freshwater bivalve Hyriopsis cumingii: the feedback of crystal growth on organic matrix

The squeezing hypothesis and the organic frameworks preformation hypothesis propose two different mechanisms to explain the interaction between organic frameworks and crystals during biomineralization of the prismatic layer of the mollusk shell. In this study, we began to study Hyriopsis cumingii shell formation and discover that this species seemed to follow the squeezing hypothesis. During the formation of the aragonite prismatic layer in the freshwater bivalve H. cumingii, we found that crystal growth was involved in controlling initiation of formation of the interprismatic organic membranes. First, newly formed crystals were embedded in the periostracum. Next, the interprismatic organic membranes of the prismatic layer were produced via squeezing between neighboring crystals. The organic matrix secreted by the mantle continuously self‐assembled into the interprismatic organic membranes as the crystals grew. In the mature stage, the interprismatic organic membranes were shaped by crystal growth. These findings provide evidence to support the squeezing hypothesis and add to the existing knowledge about interactions that occur at the organic–inorganic interfaces during mollusk shell biomineralization.     

Aragonite infill in overgrown conceptacles of coralline Lithothamnion spp. (Hapalidiaceae,Hapalidiales, Rhodophyta): new insights in biomineralization and phylomineralogy

New empirical and quantitative data in the study of calcium carbonate biomineralization and an expanded coralline psbA framework for phylomineralogy are provided for crustose coralline red algae. Scanning electron microscopy (SEM) and energy dispersive spectrometry (SEM‐EDS) pinpointed the exact location of calcium carbonate crystals within overgrown reproductive conceptacles in rhodolith‐forming Lithothamnion species from the Gulf of Mexico and Pacific Panama. SEM‐EDS and X‐ray diffraction (XRD) analysis confirmed the elemental composition of these calcium carbonate crystals to be aragonite. After spore release, reproductive conceptacles apparently became overgrown by new vegetative growth, a strategy that may aid in sealing the empty conceptacle chamber, hence influencing the chemistry of the microenvironment and in turn promoting aragonite crystal growth. The possible relevance of various types of calcium carbonate polymorphs present in the complex internal structure and skeleton of crustose corallines is discussed. This is the first study to link SEM, SEM‐EDS, XRD, Microtomography and X‐ray microscopy data of aragonite infill in coralline algae with phylomineralogy. The study contributes to the growing body of literature characterizing and speculating about how the relative abundances of carbonate biominerals in corallines may vary in response to changes in atmospheric pCO₂, ocean acidification, and global warming.     

Discovery of the mineral brucite (magnesium hydroxide) in the tropical calcifying alga Polystrata dura (Peyssonneliales,Rhodophyta)

Red algae of the family Peyssonneliaceae typically form thin crusts impregnated with aragonite. Here, we report the first discovery of brucite in a thick red algal crust (~1 cm) formed by the peyssonnelioid species Polystrata dura from Papua New Guinea. Cells of P. dura were found to be infilled by the magnesium‐rich mineral brucite [Mg(OH)₂]; minor amounts of magnesite and calcite were also detected. We propose that cell infill may be associated with the development of thick (> ~5 mm) calcified red algal crusts, integral components of tropical biotic reefs. If brucite infill within the P. dura crust enhances resistance to dissolution similarly to crustose coralline algae that infill with dolomite, then these crusts would be more resilient to future ocean acidification than crusts without infill.     

Sequencing type material resolves the identity and distribution of the generitype Lithophyllum incrustans,and related European species L. hibernicum and L. bathyporum (Corallinales,Rhodophyta)

DNA sequences from type material in the nongeniculate coralline genus Lithophyllum were used to unambiguously link some European species names to field‐collected specimens, thus providing a great advance over morpho‐anatomical identifi‐cation. In particular, sequence comparisons of rbcL, COI and psbA genes from field‐collected specimens allowed the following conclusion: the generitype species, L. incrustans, occurs mostly as subtidal rhodoliths and crusts on both Atlantic and Mediterranean coasts, and not as the common, NE Atlantic, epilithic, intertidal crust reported in the literature. The heterotypic type material of L. hibernicum was narrowed to one rhodolith belonging in Lithophyllum. As well as occurring as a subtidal rhodolith, L. hibernicum is a common, epilithic and epizoic crust in the intertidal zone from Ireland south to Mediterranean France. A set of four features distinguished L. incrustans from L. hibernicum, including epithallial cell diameter, pore canal shape of sporangial conceptacles and sporangium height and diameter. An rbcL sequence of the lectotype of Lithophyllum bathyporum, which was recently proposed to accommodate Atlantic intertidal collections of L. incrustans, corresponded to a distinct taxon hitherto known only from Brittany as the subtidal, bisporangial, lectotype, but also occurs intertidally in Atlantic Spain. Specimens from Ireland and France morpho‐anatomically identified as L. fasciculatum and a specimen from Cornwall likewise identified as L. duckerae were resolved as L. incrustans and L. hibernicum, respectively.     

Formation and mosaicity of coccolith segment calcite of the marine algae Emiliania huxleyi

Coccolithophores belong to the most abundant calcium carbonate mineralizing organisms. Coccolithophore biomineralization is a complex and highly regulated process, resulting in a product that strongly differs in its intricate morphology from the abiogenically produced mineral equivalent. Moreover, unlike extracellularly formed biological carbonate hard tissues, coccolith calcite is neither a hybrid composite, nor is it distinguished by a hierarchical microstructure. This is remarkable as the key to optimizing crystalline biomaterials for mechanical strength and toughness lies in the composite nature of the biological hard tissue and the utilization of specific microstructures. To obtain insight into the pathway of biomineralization of Emiliania huxleyi coccoliths, we examine intracrystalline nanostructural features of the coccolith calcite in combination with cell ultrastructural observations related to the formation of the calcite in the coccolith vesicle within the cell. With TEM diffraction and annular dark‐field imaging, we prove the presence of planar imperfections in the calcite crystals such as planar mosaic block boundaries. As only minor misorientations occur, we attribute them to dislocation networks creating small‐angle boundaries. Intracrystalline occluded biopolymers are not observed. Hence, in E. huxleyi calcite mosaicity is not caused by occluded biopolymers, as it is the case in extracellularly formed hard tissues of marine invertebrates, but by planar defects and dislocations which are typical for crystals formed by classical ion‐by‐ion growth mechanisms. Using cryo‐preparation techniques for SEM and TEM, we found that the membrane of the coccolith vesicle and the outer membrane of the nuclear envelope are in tight proximity, with a well‐controlled constant gap of ~4 nm between them. We describe this conspicuous connection as a not yet described interorganelle junction, the “nuclear envelope junction”. The narrow gap of this junction likely facilitates transport of Ca²⁺ ions from the nuclear envelope to the coccolith vesicle. On the basis of our observations, we propose that formation of the coccolith utilizes the nuclear envelope–endoplasmic reticulum Ca²⁺‐store of the cell for the transport of Ca²⁺ ions from the external medium to the coccolith vesicle and that E. huxleyi calcite forms by ion‐by‐ion growth rather than by a nanoparticle accretion mechanism.     

Biomineralization plasticity and environmental heterogeneity predict geographical resilience patterns of foundation species to future change

Although geographical patterns of species' sensitivity to environmental changes are defined by interacting multiple stressors, little is known about compensatory processes shaping regional differences in organismal vulnerability. Here, we examine large‐scale spatial variations in biomineralization under heterogeneous environmental gradients of temperature, salinity and food availability across a 30° latitudinal range (3,334 km), to test whether plasticity in calcareous shell production and composition, from juveniles to large adults, mediates geographical patterns of resilience to climate change in critical foundation species, the mussels Mytilus edulis and M. trossulus. We find shell calcification decreased towards high latitude, with mussels producing thinner shells with a higher organic content in polar than temperate regions. Salinity was the best predictor of within‐region differences in mussel shell deposition, mineral and organic composition. In polar, subpolar, and Baltic low‐salinity environments, mussels produced thin shells with a thicker external organic layer (periostracum), and an increased proportion of calcite (prismatic layer, as opposed to aragonite) and organic matrix, providing potentially higher resistance against dissolution in more corrosive waters. Conversely, in temperate, higher salinity regimes, thicker, more calcified shells with a higher aragonite (nacreous layer) proportion were deposited, which suggests enhanced protection under increased predation pressure. Interacting effects of salinity and food availability on mussel shell composition predict the deposition of a thicker periostracum and organic‐enriched prismatic layer under forecasted future environmental conditions, suggesting a capacity for increased protection of high‐latitude populations from ocean acidification. These findings support biomineralization plasticity as a potentially advantageous compensatory mechanism conferring Mytilus species a protective capacity for quantitative and qualitative trade‐offs in shell deposition as a response to regional alterations of abiotic and biotic conditions in future environments. Our work illustrates that compensatory mechanisms, driving plastic responses to the spatial structure of multiple stressors, can define geographical patterns of unanticipated species resilience to global environmental change.     

DNA sequencing,anatomy, and calcification patterns support a monophyletic,subarctic, carbonate reef‐forming Clathromorphum (Hapalidiaceae,Corallinales, Rhodophyta)

For the first time, morpho‐anatomical characters that were congruent with DNA sequence data were used to characterize several genera in Hapalidiaceae—the major eco‐engineers of Subarctic carbonate ecosystems. DNA sequencing of three genes (SSU, rbcL, ribulose‐1, 5‐bisphosphate carboxylase/oxygenase large subunit gene and psbA, photosystem II D1 protein gene), along with patterns of cell division, cell elongation, and calcification supported a monophyletic Clathromorphum. Two characters were diagnostic for this genus: (i) cell division, elongation, and primary calcification occurred only in intercalary meristematic cells and in a narrow vertical band (1–2 μm wide) resulting in a “meristem split” and (ii) a secondary calcification of interfilament crystals was also produced. Neopolyporolithon was resurrected for N. reclinatum, the generitype, and Clathromorphum loculosum was transferred to this genus. Like Clathromorphum, cell division, elongation, and calcification occurred only in intercalary meristematic cells, but in a wider vertical band (over 10–20 μm), and a “meristem split” was absent. Callilithophytum gen. nov. was proposed to accommodate Clathromorphum parcum, the obligate epiphyte of the northeast Pacific endemic geniculate coralline, Calliarthron. Diagnostic for this genus were epithallial cells terminating all cell filaments (no dorsi‐ventrality was present), and a distinct “foot” was embedded in the host. Leptophytum, based on its generitype, L. laeve, was shown to be a distinct genus more closely related to Clathromorphum than to Phymatolithon. All names of treated species were applied unequivocally by linking partial rbcL sequences from holotype, isotype, or epitype specimens with field‐collected material. Variation in rbcL and psbA sequences suggested that multiple species may be passing under each currently recognized species of Clathromorphum and Neopolyporolithon.     

Establishing temperate crustose early Holocene coralline algae as archives for palaeoenvironmental reconstructions of the shallow water habitats of the Mediterranean Sea

Over the past decades, coralline algae have increasingly been used as archives of palaeoclimate information due to their seasonal growth bands and their vast distribution from high latitudes to the tropics. Traditionally, these reconstructions have been performed mainly on high latitude species, limiting the geographical area of their potential use. Here we assess the use of temperate crustose fossil coralline algae from shallow water habitats for palaeoenvironmental reconstruction to generate records of past climate change. We determine the potential of three different species of coralline algae, Lithothamnion minervae, Lithophyllum stictaeforme and Mesophyllum philippii, with different growth patterns, as archives for pH (δ¹¹B) and temperature (Mg/Ca) reconstruction in the Mediterranean Sea. Mg concentration is driven by temperature but modulated by growth rate, which is controlled by species-specific and intraspecific growth patterns. L. minervae is a good temperature recorder, showing a moderate warming trend in specimens from 11.37 cal ka BP (from 14.2 ± 0.4°C to 14.9 ± 0.15°C) to today. In contrast to Mg, all genera showed consistent values of boron isotopes (δ¹¹B) suggesting a common control on boron incorporation. The recorded δ¹¹B in modern and fossil coralline specimens is in agreement with literature data about early Holocene pH, opening new perspectives of coralline-based, high-resolution pH reconstructions in deep time.     

Crusticorallina gen. nov., a nongeniculate genus in the subfamily Corallinoideae (Corallinales,Rhodophyta)

Molecular phylogenetic analyses of 18S rDNA (SSU) gene sequences confirm the placement of Crusticorallina gen. nov. in Corallinoideae, the first nongeniculate genus in an otherwise geniculate subfamily. Crusticorallina is distinguished from all other coralline genera by the following suite of morpho‐anatomical characters: (i) sunken, uniporate gametangial and bi/tetrasporangial conceptacles, (ii) cells linked by cell fusions, not secondary pit connections, (iii) an epithallus of 1 or 2 cell layers, (iv) a hypothallus that occupies 50% or more of the total thallus thickness, (v) elongate meristematic cells, and (vi) trichocytes absent. Four species are recognized based on rbcL, psbA and COI‐5P sequences, C. painei sp. nov., the generitype, C. adhaerens sp. nov., C. nootkana sp. nov. and C. muricata comb. nov., previously known as Pseudolithophyllum muricatum. Type material of Lithophyllum muricatum, basionym of C. muricata, in TRH comprises at least two taxa, and therefore we accept the previously designated lectotype specimen in UC that we sequenced to confirm its identity. Crusticorallina species are very difficult to distinguish using morpho‐anatomical and/or habitat characters, although at specific sites, some species may be distinguished by a combination of morpho‐anatomy, habitat and biogeography. The Northeast Pacific now boasts six coralline endemic genera, far more than any other region of the world.     

Authigenic anatase within 1 billion‐year‐old cells

The siliciclastic ~1 Ga‐old strata of the Torridon Group, Scotland, contain some of the most exquisitely preserved three‐dimensional organic‐walled microfossils (OWMs) of the Precambrian. A very diverse microfossil assemblage is hosted in a dominantly phosphatic and clay mineral matrix, within the Diabaig and the Cailleach Head (CH) Formations. In this study, we report on several microfossil taxa within the CH Formation (Leiosphaeridia minutissima, Leiosphaeridia crassa, Synsphaeridium spp. and Myxococcoides spp.) that include populations of cells containing an optically transparent and highly refringent mineral, here identified using electron microscopy as anatase (TiO₂). Most anatase crystals occur entirely within individual cells, surrounded by unbroken carbonaceous walls. Rarely, an anatase crystal may protrude outside a cell, interpreted to correspond to zones where the cell wall had broken down prior to anatase precipitation. Where an anatase crystal entombs an organic intracellular inclusion (ICI), the ICI is large and well preserved. These combined observations indicate that the intracellular anatase is an authigenic sedimentary phase, making this the first report of in situ precipitated anatase intimately associated with microfossils. The ability of anatase to preserve relatively large volumes of intracellular and cell wall organic material in these cells suggests that the crystallisation of anatase entombed cellular contents particularly quickly, soon after the death of the cell. This is consistent with the strong affinity of Ti for organic material, the low solubility of TiO₂, and reports of Ti occurring in living organisms. With the data currently available, we propose a mineralisation pathway for anatase involving Ti complexation with organic ligands within specific cells, leading to localised post‐mortem anatase nucleation inside these cells as the complexes broke down. Further overgrowth of the anatase crystals was likely fuelled by very early diagenetic mobilisation of Ti that had been bound to more labile organic material nearby in the sediments.     

Influences of salinity on the physiology and distribution of the Arctic coralline algae,Lithothamnion glaciale (Corallinales,Rhodophyta)

In Greenland, free‐living red coralline algae contribute to and dominate marine habitats along the coastline. Lithothamnion glaciale dominates coralline algae beds in many regions of the Arctic, but never in Godthåbsfjord, Greenland, where Clathromorphum sp. is dominant. To investigate environmental impacts on coralline algae distribution, calcification and primary productivity were measured in situ during summers of 2015 and 2016, and annual patterns of productivity in L. glaciale were monitored in laboratory‐based mesocosm experiments where temperature and salinity were manipulated to mimic high glacial melt. The results of field and cold‐room measurements indicate that both L. glaciale and Clathromorphum sp. had low calcification and photosynthetic rates during the Greenland summer (2015 and 2016), with maximum of 1.225 ± 0.17 or 0.002 ± 0.023 μmol CaCO ₃ · g^?1 · h^?1 and ?0.007 ±0.003 or ?0.004 ± 0.001 mg O₂ · L^?1 · h^?1 in each species respectively. Mesocosm experiments indicate L. glaciale is a seasonal responder; photosynthetic and calcification rates increase with annual light cycles. Furthermore, metabolic processes in L. glaciale were negatively influenced by low salinity; positive growth rates only occurred in marine treatments where individuals accumulated an average of 1.85 ± 1.73 mg · d^?1 of biomass through summer. These results indicate high freshwater input to the Godthåbsfjord region may drive the low abundance of L . glaciale , and could decrease species distribution as climate change increases freshwater input to the Arctic marine system via enhanced ice sheet runoff and glacier calving.     

The Role of Encrusting Coralline Algae in the Diets of Selected Intertidal Herbivores

Kalk Bay, South Africa, has a typical south coast zonation pattern with a band of seaweed dominating the mid-eulittoral and between two molluscan-herbivore dominated upper and lower eulittoral zones. Encrusting coralline algae were very obvious features of these zones. The most abundant herbivores in the upper eulittoral were the limpet, Cymbula oculus (10.4 ± 1.6 individuals m⁻²; 201.65 ± 32.68 g.m⁻²) and the false limpet, Siphonaria capensis (97.07± 19.92 individuals m⁻²; 77.93 16.02 g.m⁻²). The territorial gardening limpet, Scutellastra cochlear, dominated the lower eulittoral zone, achieving very high densities (545.27 ± 84.35 m⁻²) and biomass (4630.17 ± 556.13 g.m⁻²), and excluded all other herbivores and most seaweeds, except for its garden alga and the encrusting coralline alga, Spongites yendoi (35.93 ± 2.26% cover). In the upper eulittoral zone, encrusting coralline algae were only present in the guts of the chiton Acanthochiton garnoti (30.5 ± 1.33%) and the limpet C. oculus (2.9 ± 0.34%). The lower eulittoral zone limpet, Scutellastra cochlear also had a large percentage of encrusting coralline algae in its gut with limpets lacking gardens having higher (45.1 ± 1.68%) proportions of coralline algae in their guts than those with gardens (25.6 ± 0.8%). Encrusting coralline algae had high organic contents, similar to those of other encrusting and turf-forming algae, but higher organic contents than foliose algae. Radula structure, grazing frequencies as a percentage of the area grazed (upper eulittoral 73.25 ± 3.60% d⁻¹; lower eulittoral 46.0 ± 3.29% d⁻¹), and algal organic content provided evidence to support the dietary habits of the above herbivores. The data show that many intertidal molluscs are actively consuming encrusting coralline algae and that these seaweeds should be seen as an important food source.     

Morphology of the crustose coralline alga Pseudolithophyllum muricatum (Corallinales,Rhodophyta) responds to 30 years of ocean acidification in the Northeast Pacific

As the process of ocean acidification alters seawater carbon chemistry, physiological processes such as skeletal accretion are expected to become more difficult for calcifying organisms. The crustose coralline red algae (Corallinales, Rhodophyta) form an important guild of calcifying primary producers in the temperate Northeast Pacific. The morphology of important ecological traits, namely, skeletal density and thallus thickness near the growing edge, was evaluated in Pseudolithophyllum muricatum (Foslie) Steneck & R.T. Paine, the competitively dominant alga within this guild. P. muricatum shows a morphological response to increased ocean acidification in the temperate Northeast Pacific. Comparing historical (1981–1997) and modern (2012) samples from the field, crust thickness near the growing edge was approximately half as thick in modern samples compared with historical samples, while crust calcite density showed no significant change between the two sample groups. Morphological changes at the growing edge have important consequences for mediating competitive interactions within this guild of algae, and may affect the role of crustose coralline algal beds as hosts to infaunal communities and facilitators of recruitment in many invertebrate and macroalgal species.     

Ocean acidification weakens the structural integrity of coralline algae

The uptake of anthropogenic emission of carbon dioxide is resulting in a lowering of the carbonate saturation state and a drop in ocean pH. Understanding how marine calcifying organisms such as coralline algae may acclimatize to ocean acidification is important to understand their survival over the coming century. We present the first long‐term perturbation experiment on the cold‐water coralline algae, which are important marine calcifiers in the benthic ecosystems particularly at the higher latitudes. Lithothamnion glaciale, after three months incubation, continued to calcify even in undersaturated conditions with a significant trend towards lower growth rates with increasing pCO₂. However, the major changes in the ultra‐structure occur by 589 μatm (i.e. in saturated waters). Finite element models of the algae grown at these heightened levels show an increase in the total strain energy of nearly an order of magnitude and an uneven distribution of the stress inside the skeleton when subjected to similar loads as algae grown at ambient levels. This weakening of the structure is likely to reduce the ability of the alga to resist boring by predators and wave energy with severe consequences to the benthic community structure in the immediate future (50 years).     

Ecological eustress? Nutrient supply,bloom stimulation and competition determine dominance of the diatom Didymosphenia geminata

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One‐year experiment on the physiological response of the Mediterranean crustose coralline alga,Lithophyllum cabiochae,to elevated pCO2 and temperature

The response of respiration, photosynthesis, and calcification to elevated pCO₂ and temperature was investigated in isolation and in combination in the Mediterranean crustose coralline alga Lithophyllum cabiochae. Algae were maintained in aquaria during 1 year at near‐ambient conditions of irradiance, at ambient or elevated temperature (+3°C), and at ambient (ca. 400 μatm) or elevated pCO₂ (ca. 700 μatm). Respiration, photosynthesis, and net calcification showed a strong seasonal pattern following the seasonal variations of temperature and irradiance, with higher rates in summer than in winter. Respiration was unaffected by pCO₂ but showed a general trend of increase at elevated temperature at all seasons, except in summer under elevated pCO₂. Conversely, photosynthesis was strongly affected by pCO₂ with a decline under elevated pCO₂ in summer, autumn, and winter. In particular, photosynthetic efficiency was reduced under elevated pCO₂. Net calcification showed different responses depending on the season. In summer, net calcification increased with rising temperature under ambient pCO₂ but decreased with rising temperature under elevated pCO₂. Surprisingly, the highest rates in summer were found under elevated pCO₂ and ambient temperature. In autumn, winter, and spring, net calcification exhibited a positive or no response at elevated temperature but was unaffected by pCO₂. The rate of calcification of L. cabiochae was thus maintained or even enhanced under increased pCO₂. However, there is likely a trade‐off with other physiological processes. For example, photosynthesis declines in response to increased pCO₂ under ambient irradiance. The present study reports only on the physiological response of healthy specimens to ocean warming and acidification, however, these environmental changes may affect the vulnerability of coralline algae to other stresses such as pathogens and necroses that can cause major dissolution, which would have critical consequence for the sustainability of coralligenous habitats and the budgets of carbon and calcium carbonate in coastal Mediterranean ecosystems.     

Persistence of Escherichia coli introduced into streambed sediments with goose,deer and bovine animal waste

Aims:  The focus of this work was to compare the survival of Escherichia coli introduced into streambed sediments from goose, deer and bovine faeces vs indigenous E. coli. Methods and Results:  The survival experiments were conducted in flow‐through chambers for 32 days using two sediments (mineral and organic) obtained from a first‐order creek in Maryland. Bovine, goose and deer faeces were collected fresh and diluted or enriched so that added E. coli and indigenous populations were equivalent. Escherichia coli and total coliforms were enumerated using the Colilert‐18 Quanti‐Tray system. Patterns of E. coli survival and inactivation rates were virtually identical for indigenous strains in both mineral and organic sediments. The addition of E. coli strains from bovine, goose or deer faeces had relatively little impact on final E. coli concentrations, with the exception of deer‐borne E. coli populations in the organic sediment. Conclusion:  These results indicate that indigenous sediment‐borne E. coli strains are generally, or more, persistent than those deposited into sediments, including wildlife. Significance and Impact of the Study:  This is the first study on the survival of E. coli originating from wildlife faeces, in sediments, as opposed to bovine faeces or laboratory‐cultured strains. As wildlife are likely to be the primary source of E. coli in most non agricultural watersheds, an understanding of the persistence of these strains is important to understanding microbial water quality.     

Epitope detection chromatography: a method to dissect the structural heterogeneity and inter‐connections of plant cell‐wall matrix glycans

Plant cell walls are complex, multi‐macromolecular assemblies of glycans and other molecules and their compositions and molecular architectures vary extensively. Even though the chemistry of cell‐wall glycans is now well understood, it remains a challenge to understand the diversity of glycan configurations and interactions in muro, and how these relate to changes in the biological and mechanical properties of cell walls. Here we describe in detail a method called epitope detection chromatography analysis of cell‐wall matrix glycan sub‐populations and inter‐connections. The method combines chromatographic separations with use of glycan‐directed monoclonal antibodies as detection tools. The high discrimination capacity and high sensitivity for the detection of glycan structural features (epitopes) provided by use of established monoclonal antibodies allows the study of oligosaccharide motifs on sets of cell‐wall glycans in small amounts of plant materials such as a single organ of Arabidopsis thaliana without the need for extensive purification procedures. We describe the use of epitope detection chromatography to assess the heterogeneity of xyloglucan and pectic rhamnogalacturonan I sub‐populations and their modulation in A. thaliana organs.