Phytoplankton blooms characterize temperate ocean margin zones in spring. We investigated the bacterioplankton response to a diatom bloom in the North Sea and observed a dynamic succession of populations at genus-level resolution. Taxonomically distinct expressions of carbohydrate-active enzymes (transporters; in particular, TonB-dependent transporters) and phosphate acquisition strategies were found, indicating that distinct populations of Bacteroidetes, Gammaproteobacteria, and Alphaproteobacteria are specialized for successive decomposition of algal-derived organic matter. Our results suggest that algal substrate availability provided a series of ecological niches in which specialized populations could bloom. This reveals how planktonic species, despite their seemingly homogeneous habitat, can evade extinction by direct competition.

http://science.sciencemag.org/content/sci/336/6081/608.full.pdf

Substrate-Controlled Succession of Marine Bacterioplankton Populations Induced by a Phytoplankton Bloom

Overview of microalgal extracellular polymeric substances (EPS) and their applications.

Soft-sediment habitats in intertidal and shallow subtidal marine ecosystems frequently support extensive populations of benthic microalgae (microphytobenthos). These algal assemblages are dominated by species of motile benthic diatoms and form biofilms, a matrix of cells, sediments and extracellular polymeric substances (EPS), that create a complex microhabitat and act to stabilise sediments. Diatom EPS consists of a relatively undefined complex mixture of proteins, proteoglycans and carbohydrates. This complexity causes problems in extracting and analysing EPS and in the intercomparison of studies. This chapter reviews our current knowledge on the production rates, patterns and composition of benthic diatom EPS in culture and field studies. Production patterns are dynamic, changing with cell growth phase, photosynthesis and irradiance, nutrient conditions, and are also linked to endogenous cell rhythms. Meta-analysis of published monosaccharide composition data identified at least four major types of EPS produced by benthic diatoms, with varying patterns of production and composition. It is clear that more detailed research on the structural and physical properties of EPS are needed to understand its role in the environment. The natural occurrence of EPS is closely linked to diatom biomass, a pattern consistent over both macro (km) and micro ( μ m) scales. EPS is lost from sediments by various routes, solubilisation and removal by overlying water, bacterial degradation and consumption by deposit-feeding invertebrates. Work is needed to quantify these pathways and clarify the importance of EPS in coastal carbon cycles. Diatom EPS is a widely cited mechanism for increasing sediment stability and stabilisation by biofilms is well described. However, data are not consistent and developments in our knowledge of the structure and function of EPS are needed to explain how EPS binds and interacts within the sediment- biofilm matrix and affects the theology of sediment.

The importance of extracellular carbohydrate productionby marine epipelic diatoms

In this paper we report on the effect of surface wettability on surface selection and adhesion properties of settled (adhered) spores of the biofouling marine alga Enteromorpha and cells of the diatom Amphora, through the use of patterned self-assembled monolayers (SAMs). The SAMs were formed from alkanethiols terminated with methyl (CH(3)) or hydroxyl (OH) groups, or mixtures of the two, creating a discontinuous gradient of wettability as measured by advancing water contact angle. In the case of Enteromorpha, primary adhesion, as measured by the transition from a motile spore to a settled, sessile organism, is strongly promoted by the hydrophobic surfaces. On the other hand, adhesion strength of the settled spores, as measured by resistance to detachment in a turbulent flow cell, is greatest on a hydrophilic surface. In the case of Amphora, there is little influence of surface wettability on the primary adhesion of this organism, but motility is inhibited at contact angles ≥60° and the cells are more strongly adhered to hydrophobic surfaces. Adhesion strength of Enteromorpha spores is also influenced by group size, spores in groups being more resistant to detachment than single spores.

/pdf/the-influence-of-surface-wettability-on-the-adhesion-1vl41en1ew.pdf

The influence of surface wettability on the adhesion strength of settled spores of the green alga enteromorpha and the diatom amphora.

Recent demands for non-toxic antifouling technologies have led to increased interest in coatings based on silicone elastomers that 'release' macrofouling organisms when hydrodynamic conditions are sufficiently robust. However, these types of coatings accumulate diatom slimes, which are not released even from vessels operating at high speeds (>30 knots). In this study, adhesion strength and motility of three common fouling diatoms (Amphora coffeaeformis var. perpusilla (Grunow) Cleve, Craspedostauros australis Cox and Navicula perminuta Grunow) were measured on a poly-dimethylsiloxane elastomer (PDMSE) and acid-washed glass. Adhesion of the three species was stronger to PDMSE than to glass but the adhesion strengths varied. The wall shear stress required to remove 50% of cells from PDMSE was 17 Pa for Craspedostauros, 24 Pa for Amphora and >>53 Pa for Navicula; the corresponding values for glass were 3, 10 and 25 Pa. In contrast, the motility of the three species showed little or no correlation between the two surfaces. Craspedostauros moved equally well on glass and PDMSE, Amphora moved more on glass initially before movement ceased and Navicula moved more on PDMSE before movement ceased. The results show that fouling diatoms adhere more strongly to a hydrophobic PDMSE surface, and this feature may contribute to their successful colonization of low surface energy, foul-release coatings. The results also indicate that diatom motility is not related to adhesion strength, and motility does not appear to be a useful indicator of surface preference by diatoms.

Adhesion and motility of fouling diatoms on a silicone elastomer.

Extracellular adhesives from the diatoms Achnanthes longipes, Amphora coffeaeformis, Cymbella cistula, and Cymbella mexicana were characterized by monosaccharide and methylation analysis, lectin-fluorescein isothiocyanate localization, and cytochemical staining. Polysaccharide was the major component of adhesives formed during cell motility, synthesis of a basal pad, and/or production of a highly organized shaft. Hot water-insoluble/hot 0.5 M NaHCO3-soluble anionic polysaccharides from A. longipes and A. coffeaeformis adhesives were primarily composed of galactosyl (64-70%) and fucosyl (32-42%) residues. In A. longipes polymers, 2,3-, t-, 3-, and 4-linked/substituted galactosyl, t-, 3-, 4-, and 2-linked fucosyl, and t- and 2-linked glucuronic acid residues predominated. Adhesive polysaccharides from C. cistula were EDTA-soluble, sulfated, consisted of 83% galactosyl (4-, 4,6-, and 3,4-linked/substituted) and 13% xylosyl (t-, 4f/5p-, and 3p-linked/substituted) residues, and contained no uronosyl residues. Ulex europaeus agglutinin uniformly localized [alpha](1,2)-L-fucose units in C. cistula and Achnanthes adhesives formed during motility and in the pads of A. longipes. D-Galactose residues were localized throughout the shafts of C. cistula and capsules of A. coffeaeformis. D-Mannose and/or D-glucose, D-galactose, and [alpha](t)-L-fucose residues were uniformly localized in the outer layers of A. longipes shafts by Cancavalia ensiformis, Abrus precatorius, and Lotus tetragonolobus agglutinin, respectively. A model for diatom cell adhesive structure was developed from chemical characterization, localization, and microscopic observation of extracellular adhesive components formed during the diatom cell-attachment process.

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae) (I. A Model of Adhesives Based on Chemical Characterization and Localization of Polysaccharides from the Marine Diatom Achnanthes longipes and Other Diatoms)

B. A. Wustman

Papers

Extracellular Matrix Assembly in Diatoms (Bacillariophyceae) (I. A Model of Adhesives Based on Chemical Characterization and Localization of Polysaccharides from the Marine Diatom Achnanthes longipes and Other Diatoms)

Optimization of DNAI1 mRNA Constructs to Treat Primary Ciliary Dyskinesia

An mRNA-Based Therapy to Treat Primary Ciliary Dyskinesia: Aerosol Delivery, Biodistribution and Tolerability

Rescue of Ciliary Function in Cell-Based Primary Ciliary Dyskinesia Models Using Nebulized, Lipid Nanoparticle (LNP)-Formulated mRNA