Chemical characterization of exopolysaccharides from the marine fouling diatom amphora coffeaeformis

Amphora coffeaeformis cells were grown in batch cultures under continuous illumination at 18°C for 10 d. Algal cells were removed by centrifugation, lyophilized and used for the extraction of exopolysaccharides using either 0.05 M EDTA, 1 M NaOH or 1.5 M NaCl. The 1.5 M NaCl treatment removed most exopolysaccharides. Glucose (81%) was the most abundant monosaccharide in the exopolysaccharides. The chemical composition data suggest that the exopolymers were acidic sulphated polysaccharides containing high concentrations of pyruvate (22%) and uronic acids (18%). These polysaccharides may play an important role in metal complexation and protection from desiccation in A. coffeaeformis.     

Novel whole cell adhesion assays of three isolates of the fouling diatom Amphora coffeaeformis reveal diverse responses to surfaces of different wettability

Whole cell, strength of adhesion assays of three different isolates of the fouling diatom Amphora coffeaeformis were compared using a hydrophilic surface viz. acid washed glass (AWG), and a hydrophobic surface viz. a self assembled monolayer (SAM) of undecanethiol (UDT). Assays were performed using a newly designed turbulent flow channel that permits direct observation and recording of cell populations on a test surface. Exposure to continuous shear stress over 3?h revealed that the more motile isolate, WIL2, adhered much more strongly to both test surfaces compared to the other two strains. When the response of the isolates to shear stress after 3?h was compared, there was no significant difference in the percentage of cells removed, irrespective of surface wettability. Cells of the three isolates of A. coffeaeformis varied significantly in their response to different surfaces during initial adhesion, indicating the presence of a wide range of 'physiological races' within this species.     

Novel whole cell adhesion assays of three isolates of the fouling diatom Amphora coffeaeformis reveal diverse responses to surfaces of different wettability

Whole cell, strength of adhesion assays of three different isolates of the fouling diatom Amphora coffeaeformis were compared using a hydrophilic surface viz. acid washed glass (AWG), and a hydrophobic surface viz. a self assembled monolayer (SAM) of undecanethiol (UDT). Assays were performed using a newly designed turbulent flow channel that permits direct observation and recording of cell populations on a test surface. Exposure to continuous shear stress over 3 h revealed that the more motile isolate, WIL2, adhered much more strongly to both test surfaces compared to the other two strains. When the response of the isolates to shear stress after 3 h was compared, there was no significant difference in the percentage of cells removed, irrespective of surface wettability. Cells of the three isolates of A. coffeaeformis varied significantly in their response to different surfaces during initial adhesion, indicating the presence of a wide range of ‘physiological races’ within this species.     

Calcium is Necessary for Motility in the Diatom Amphora coffeaeformis

The marine diatom Amphora coffeaeformis required Ca²⁺ and bicarbonate for motility. Movement was inhibited by the Ca²⁺-blocking agents ruthenium red and α-isopropyl-α-[(N-methyl-N-homoveratryl)-α- aminopropyl]-3,4,5-trimethoxy phenyl acetonitrile and the metabolic energy uncoupler, carbonyl cyanide 3-chlorophenylhydrazone. 3-(3′,4-Dichlorophenyl)-1,1-Dimethyl urea was without effect on cells at a concentration that prevented O₂ production in the light. Although Sr²⁺ could replace Ca²⁺ in the attachment of cells to glass, it did not substitute for Ca²⁺ in motility.     

Mannose transport in Amphora coffeaeformis var. perpusilla (Bacillariophyceae).

Amphora coffeaeformis var. perpusilla is able to concentrate but not metabolize mannose. The sugar, which can be accumulated against a concentration gradient, is taken up only after a short lag. Preincubation with glucose allows immediate mannose uptake. Substances that reduce the ATP content of the diatom cells also inhibit mannose uptake as do sugars of similar stereochemical configuration. Mannose appears to act as a non-metabolizable analogue of glucose in these respects.     

On rhythmic movement of the diatom Amphora ovalis

The vertical migration, motility and cell division rhythms of the diatom Amphora ovalis Kütz from Lake Kinneret, Israel, have been studied under laboratory conditions and results compared with comparable rhythms of other unicellular algae. The vertical migration rhythm exhibits two peaks during the light period, both when the cells are kept in continuous light or continuous dark. There is a single peak of motility occurring in the first half of the natural light period and a single peak of cell division in the latter half of the dark period. Rephasing of the rhythm by means of delayed start up time is illustrated and the possible interaction of phototactic and geotactic rhythms discussed.     

The role of the plasmalemma in metal tolerance in angiosperms

Evidence for the role of the plasmalemma in metal tolerance of metal resistant ecotypes, cultivars and clones is presented. A range of tolerance mechanisms involving the plasmalemma are discussed including alterations to protein carrier and channel function and synthesis, efflux pumps and maintenance of plasmalemma integrity. Specific examples of such alterations from the literature on Al, As and Cu tolerance, where the plasmalemma has been shown to have a role in tolerance are considered. Tolerance by alterations to plasmalemma function in tolerant ecotypes may also rely on internal metal detoxification mechanisms constitutive in tolerant and non-tolerant plants.     

Extracellular polymeric substances of the marine fouling diatom amphora rostrata Wm.Sm

Amphora rostrata was grown under continuous illumination at 27°C in batch cultures using f/2 medium. Cell biomass (measured as chllorophyll a and cell counts) reached a maximum on day 7. Thereafter, cell biomass as chl a showed a small decrease. Planktonic('free') and biofilm extracellular polymeric substances (EPS) from the adherent cells of A. rostrata were studied. Both types of EPS were produced during the logarithmic phase of growth. However, production was higher during the stationary growth phase. Enhanced EPS production was associated with nutrient deficient conditions. Planktonic and biofilm EPS were purified by gel filtration using Sephadex G‐200 and ion exchange chromatography using DEAE‐cellulose. Both polymers showed the presence of a single peak. Capillary gas Chromatographie analysis of both planktonic and biofilm EPS showed that fucose (36.7%) and galactose (27.6%) were the most abundant monosaccharides, with small quantities of rhamnose, xylose, arabinose, mannose and glucose. Other chemical analysis showed the presence of sulphate, uronic acids, hexoamines, pyruvate and proteins in both the planktonic and bio‐film EPS. Uronic acid, pyruvate and sulphate together were found to contribute ～50 to 60% (W/W) to the EPS of A. rostrata. Such a high content of non‐sugar components indicates their importance to the diatom in metal binding, desiccation prevention and flexibility.     

The role of the root cell wall in the heavy metal tolerance ofAthyrium yokoscense

Cells of the roots ofA. yokoscense growing on metalliferous habitats were fractionated into their cell wall and cytoplasmic components. About 70–90% of the total copper, zinc and cadmium was located in the cell wall. Copper had a markedly greater affinity for the cell wall than zinc and cadmium, and was prevented from entering the cytoplasm. A large proportion of these heavy metals in the cell wall were exchanged as ions. The capacity of the cell wall for exchanging metal ions inA. yokoscense was higher than in other plants growing on metalliferous habitats. However, compared with different ferns unable to grow on metalliferous habitats, this capacity was not unique toA. yokoscense. Consequetly, the root cell wall ofA. yokoscense is considered to be an important site of metal ion storage and may play the role of an excretory organ for heavy metals. On the other hand, as proportion of the heavy metls was transported to the cytoplasm, where the metal content was much higher than the average for normal ferns. This would suggest thatA. yokoscense has another metabolic mechanism related to metal tolerance.     

金属硫蛋白和植物螯合肽在植物重金属耐性中的作用

植物螯合肽和金属硫蛋白广泛存在于植物界中,它们对植物耐重金属特别重要,能够与重金属形成复合物,以缓解重金属对植物的危害。本文就这两种金属螯合蛋白的结构、生物合成和基因调控,以及在植物体内缓解重金属毒害的作用方面作了简要介绍。     

The effect of bacteria on the solubilization of silica in diatom frustules

P atrick , S heila & H olding , A.J. 1985. The effect of bacteria on the solubilization of silica in diatom frustules. Journal of Applied Bacteriology 59 , 7–16.
Natural bacterial populations in samples of water from Loch Leven and Lough Neagh increased the rate of solubilization of frustule silica from an axenic Cyclotella meneghiniana culture, compared with sterile autolysis, at 25C. In the inoculated cultures 50–60% of the silica was solubilized over a period of 30 d. Bacterial populations in Loch Leven water also enhanced the solubilization of silica from non-axenic cultures of Asterionella formosa, Tabellaria flocculosa, Navicula pellicu-losa and C. meneghiniana , compared with control cultures sterilized with mercuric chloride. Similar results were obtained with Lough Neagh populations incubated with A. formosa . In comparison with untreated cells, the treatment of diatom cells with ultra-sonication did not increase the release of silica. Pure cultures of bacteria from Loch Leven water enhanced the release of silica from non-axenic A. formosa and axenic C. meneghiniana compared with sterile control treatments. The variation in the ability of cultures to solubilize the frustule silica appeared to be related to their potential to produce hydrolytic enzymes. Natural populations of Loch Leven and Lough Neagh water bacteria and certain bacterial cultures caused the diatoms to aggregate, which did not enhance the release of silica.     

Assessing the role of endophytic bacteria in the halophyte Arthrocnemum macrostachyum salt tolerance

• There is an increasing interest to use halophytes for revegetation of salt affected ecosystems, as well as in understanding their mechanisms of salt tolerance. We hypothesized that bacteria from the phyllosphere of these plants might play a key role in its high tolerance to excessive salinity.
• Eight endophytic bacteria belonging to Bacillus and closely related genera were isolated from phyllosphere of the halophyte Arthrocnemum macrostachyum growing in salty agricultural soils. The presence of plant‐growth promoting (PGP) properties, enzymatic activities and tolerance towards NaCl was determined. Effects of inoculation on seeds germination and adult plant growth under experimental NaCl treatments (0, 510 and 1030 mM NaCl) were studied.
• Inoculation with a consortium including the best performing bacteria improved considerably the kinetics of germination and the final germination percentage of A. macrostachyum seeds. At high NaCl concentrations (1030 mM), inoculation of plants mitigated the effects of high salinity on plant growth and physiological performance and, in addition, this consortium appears to have increased the potential of A. macrostachyum to accumulate Na⁺ in its shoots, thus improving sodium phytoextraction capacity.
• Bacteria isolated from A. macrostachyum phyllosphere seem to play an important role in plant salt tolerance under stressing salt concentrations. The combined use of A. macrostachyum and its microbiome can be an adequate tool to enhance plant adaptation and sodium phytoextraction during restoration of salt degraded soils.

     

Association of metal tolerance with multiple antibiotic resistance of bacteria isolated from drinking water.

Bacterial isolates from the drinking water system of an Oregon coastal community were examined to assess the association of metal tolerance with multiple antibiotic resistance. Positive correlations between tolerance to high levels of Cu2+, Pb2+, and Zn2+ and multiple antibiotic resistance were noted among bacteria from distribution waters but not among bacteria from raw waters. Tolerances to higher levels of Al3+ and Sn2+ were demonstrated more often by raw water isolates which were not typically multiple antibiotic resistant. A similar incidence of tolerance to Cd2+ was demonstrated by isolates of both water types and was not associated with multiple antibiotic resistance. These results suggest that simultaneous selection phenomena occurred in distribution water for bacteria which exhibited unique patterns of tolerance to Cu2+, Pb2+, and Zn2+ and antibiotic resistance.     

Purification of fucoxanthin from the diatom Amphora capitellata by preparative chromatography after its enhanced productivity via oxidative stress

Journal of Applied Phycology - Microalgae with high growth rates represent a potential source of carotenoids including fucoxanthin. For commercial fucoxanthin production, choosing the cultivation...     

The auxospore wall of the marine diatom Melosira nummuloides (Dillw.) C. Ag. and related species

The auxospore wall of Melosira nummuloides C. A. Agardh is composed of two distinct parts, an organic layer and a layer of siliceous scales. Similar scales are reported from other species of the genus and their mode of formation is described. The possible phylogenetic significance of the two wall layers is discussed with respect to the two main groups of diatoms.     

Seasonal variations in the fouling diatom community structure from a monsoon influenced tropical estuary

Seasonal variations in the fouling diatom community from a monsoon influenced tropical estuary were investigated. The community composition did not differ significantly between stainless steel and polystyrene substrata due to dominance by Navicula spp. The experimental evidence suggests that Amphora, which is a dominant fouling diatom in temperate waters, ultimately dominates the community in tropical regions when conditions are favourable. These observations reveal that a faster onset of macrofouling interferes with the microfouling community wherein the faster recruiters that have a higher abundance in ambient waters, dominate the community. Seasonal variations were observed in the fouling diatom community. Navicula delicatula dominated during the post-monsoon and tychopelagic diatoms (Melosira and Odontella) were observed during the monsoon. Low diatom abundance was recorded during the pre-monsoon season. The results indicate that although the fouling diatom community composition does not vary between substrata, there is a seasonal change in the community depending on the physical, chemical and biological interactions.