Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling

The resistance of charged polymers to biofouling was investigated by subjecting cationic (PDMAEMA), anionic (PSPMA), neutral (PHEMA-co-PEG₁₀MA), and zwitterionic (PSBMA) brushes to assays testing protein adsorption; attachment of the marine bacterium Cobetia marina; settlement and adhesion strength of zoospores of the green alga Ulva linza; settlement of barnacle (Balanus amphitrite and B. improvisus) cypris larvae; and field immersion tests. Several results go beyond the expected dependence on direct electrostatic attraction; PSPMA showed good resistance towards attachment of C. marina, low settlement and adhesion of U. linza zoospores, and significantly lower biofouling than on PHEMA-co-PEG₁₀MA or PSBMA after a field test for one week. PDMAEMA showed potential as a contact-active anti-algal coating due to its capacity to damage attached spores. However, after field testing for eight weeks, there were no significant differences in biofouling coverage among the surfaces. While charged polymers are unsuitable as antifouling coatings in the natural environment, they provide valuable insights into fouling processes, and are relevant for studies due to charging of nominally neutral surfaces.     

Functional polymer brushes via surface-initiated atom transfer radical graft polymerization for combating marine biofouling

Dense and uniform polymer brush coatings were developed to combat marine biofouling. Nonionic hydrophilic, nonionic hydrophobic, cationic, anionic and zwitterionic polymer brush coatings were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-hydroxyethyl methacrylate, 2,3,4,5,6-pentafluorostyrene, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 4-styrenesulfonic acid sodium and N,N′-dimethyl-(methylmethacryloyl ethyl) ammonium propanesulfonate, respectively. The functionalized surfaces had different efficacies in preventing adsorption of bovine serum albumin (BSA), adhesion of the Gram-negative bacterium Pseudomonas sp. NCIMB 2021 and the Gram-positive Staphylococcus aureus, and settlement of cyprids of the barnacle Amphibalanus amphitrite (=Balanus amphitrite). The nonionic hydrophilic, anionic and zwitterionic polymer brushes resisted BSA adsorption during a 2 h exposure period. The nonionic hydrophilic, cationic and zwitterionic brushes exhibited resistance to bacterial fouling (24 h exposure) and cyprid settlement (24 and 48 h incubation). The hydrophobic brushes moderately reduced protein adsorption, and bacteria and cyprid settlement. The anionic brushes were least effective in preventing attachment of bacteria and barnacle cyprids. Thus, the best approach to combat biofouling involves a combination of nonionic hydrophilic and zwitterionic polymer brush coatings on material surfaces.     

Streptomyces neyagawaensis as a control for the hazardous biomass of Microcystis aeruginosa (Cyanobacteria) in eutrophic freshwaters

An aquatic bacterium capable of eliminating the cyanobacterium Microcystis aeruginosa was isolated from the sediment of an eutrophic lake (Lake Juam, Korea). On the basis of 16S rDNA sequences and biochemical and morphological characteristics, the isolate was determined to be Streptomyces neyagawaensis. It grew optimally at 40 °C and pH 7. In the presence of this bacterium, the biomass of cyanobacterium M. aeruginosa NIES-298 was strongly suppressed, by up to 84.5% in abundance compared to the control. The antialgal activity of S. neyagawaensis depended on the growth phase of the cyanobacterium, but not of the antialgal bacterium. The antialgal activity of S. neyagawaensis was effective against a wide range of algae, including the green alga Chlorella sp., the diatoms Aulacoseira granulata and Stephanodiscus hantzschii, and four cyanobacteria, M. aeruginosa NIES-44, Anabaena cylindrica, Anabaena flos-aquae, and Oscillatoria sancta. S. neyagawaensis indirectly attacked M. aeruginosa by secretion of extracellular antialgal substances that were localized in the bacterial periplasm and had a specific activity of 7.7 U/μg. These results suggest that indigenous bacteria isolated from sediments may have potential application in controlling harmful cyanobacterial blooms in freshwaters.     

Antimicrobial effects of esters and amides of 3-(5-nitro-2-furyl)acrylic acid

The effect of 18 newly synthesized esters and amides of 3-(5-nitro-2-furyl)acrylic acid on bacteria (Escherichia coli, Staphylococcus aureus), yeasts (Saccharomyces cerevisiae, Candida albicans), molds (Aspergillus niger, Penicillium cyclopium, Rhizopus oryzae) and algae (Chlorella pyrenoidosa, Euglena gracilis, Scenedesmus obliquus) was investigated. The MIC values revealed antimycotic, antialgal and antibacterial activity of the studied derivates. The antimycotic activity was found to decrease with increasing the length of the alkyl chain of esters and after introduction of amino nitrogen into the furylethylene backbone. The inhibitory effect on growth is caused by blocking bioenergetic processes, glycolysis in particular.     

Chemistry and Biology of the Genus Flourensia (Asteraceae)

Flourensia species are dominant plants that are adapted to semidesertic and desertic regions. It is believed that they are successful plants because they employ several protection mechanisms, including the formation of a waxy film on their aerial parts to protect them from dehydration. This waxy film contains chemical compounds that are capable of inhibiting the growth of other plants and of acting as allelopathic and herbicidal agents and as germination inhibitors. These plants also limit herbivory, and they exhibit insecticidal, insect antifeedant, antibacterial, antifungal, antialgal, and antitermite activities. Sesquiterpenes, flavonoids, benzofurans, chromenes, coumarins, lupan triterpenes, aliphatic lactones, and aromatic and acetilenic compounds have all been isolated from the organic extracts of Flourensia species. Monoterpenes, sesquiterpenes, and aliphatic hydrocarbons are the main constituents found in their essential oils. This review is an overview of the chemical constituents and of the biological activities of Flourensia species.     

Isolation and identification of antialgal substances produced byPseudomonas aeruginosa

Pseudomonas aeruginosa strongly inhibited the growth of green microalgae and cyanobacteria by the release of low molecular weight, thermoresistant factors. The antialgal substances were resistant to various enzymes and remained active in agar after a 3-months storage period at 4 °C in the absence of light. The results indicate that inhibition of algal growth was mediated by the phenazine pigments released by the bacterium. Pyocyanine and an unidentified pale blue pigment had no effect on algal growth, whereas 1-hydroxyphenazine and oxychlororaphine showed strong antialgal activity.Groupe de Recherche en Recyclage Biologique et AquicultureDépartement des Sciences et Technologie des Aliments     

Polymer brush controlled bioinspired calcium phosphate mineralization and bone cell growth

Polymer brushes on thiol-modified gold surfaces were synthesized by using terminal thiol groups for the surface-initiated free radical polymerization of methacrylic acid and dimethylaminoethyl methacrylate, respectively. Atomic force microscopy shows that the resulting poly(methacrylic acid) (PMAA) and poly(dimethylaminoethyl methacrylate) (PDMAEMA) brushes are homogeneous. Contact angle measurements show that the brushes are pH-responsive and can reversibly be protonated and deprotonated. Mineralization of the brushes with calcium phosphate at different pH yields homogeneously mineralized surfaces, and preosteoblastic cells proliferate on both the nonmineralized and mineralized surfaces. The number of living cells on the mineralized hybrid surfaces is ca. 3 times (PDMAEMA) and 10 times (PMAA) higher than on the corresponding nonmineralized brushes.     

Polyelectrolyte complexes between (cross-linked) N-carboxyethylchitosan and (quaternized) poly[2-(dimethylamino)ethyl methacrylate]: preparation, characterization, and antibacterial properties

Novel polyelectrolyte complexes (PECs) between N-carboxyethylchitosan (CECh) and well-defined (quaternized) poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) have been obtained. The modification of chitosan into CECh allows the preparation of PECs in a pH range in which chitosan cannot form complexes. The CECh/PDMAEMA complex is formed in a narrow pH range around 7. The quaternization of the tertiary amino groups of PDMAEMA enables complex formation with CECh both in neutral and in alkaline medium. Cross-linked CECh is also capable of forming complexes with (quaternized) PDMAEMA. The antibacterial activity of (cross-linked) CECh, (quaternized) PDMAEMA, and their complexes against Escherichia coli has been evaluated. In contrast to (quaternized) PDMAEMA, (cross-linked) CECh exhibits no antibacterial activity. The complex formation between cross-linked CECh and (quaternized) PDMAEMA results in a loss of the inherent antibacterial activity of the latter in neutral medium. In acidic medium, the complexes exhibit strong antibacterial activity due to complex disintegration and release of (quaternized) PDMAEMA.     

Detritus and Epibiota on Artificial Substrata: The Possible Role of Food in Structuring Hawaiian Epiphytal Amphipod Communities

Epiphytal amphipods prefer artificial substrata (bottle brushes) which accumulated epibiotic coatings while submerged in the sea for a period of up to 15 days. There is evidence that these amphipods eat epibiota on algae (predominately Padina japonica YAMADEA 1931 and Dictyota crenulata AGARDH 1847) and that food availability may be a factor which helps structure epiphytal amphipod communities.     

Functional polymer brushes via surface-initiated atom transfer radical graft polymerization for combating marine biofouling

Dense and uniform polymer brush coatings were developed to combat marine biofouling. Nonionic hydrophilic, nonionic hydrophobic, cationic, anionic and zwitterionic polymer brush coatings were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-hydroxyethyl methacrylate, 2,3,4,5,6-pentafluorostyrene, 2-(methacryloyloxy)ethyl trimethylammonium chloride, 4-styrenesulfonic acid sodium and N,N'-dimethyl-(methylmethacryloyl ethyl) ammonium propanesulfonate, respectively. The functionalized surfaces had different efficacies in preventing adsorption of bovine serum albumin (BSA), adhesion of the Gram-negative bacterium Pseudomonas sp. NCIMB 2021 and the Gram-positive Staphylococcus aureus, and settlement of cyprids of the barnacle Amphibalanus amphitrite (=Balanus amphitrite). The nonionic hydrophilic, anionic and zwitterionic polymer brushes resisted BSA adsorption during a 2?h exposure period. The nonionic hydrophilic, cationic and zwitterionic brushes exhibited resistance to bacterial fouling (24?h exposure) and cyprid settlement (24 and 48?h incubation). The hydrophobic brushes moderately reduced protein adsorption, and bacteria and cyprid settlement. The anionic brushes were least effective in preventing attachment of bacteria and barnacle cyprids. Thus, the best approach to combat biofouling involves a combination of nonionic hydrophilic and zwitterionic polymer brush coatings on material surfaces.     

Comparison of the carpal cleaning brush in two genera of hydrothermal vent shrimp (Crustacea,Decapoda, Bresiliidae)

Clusters of specialized serrate setae in patches called “carpal cleaning brushes,” or carpal-propodal brushes, are found on the distal margins of the chelipedal carpus in many species of caridean shrimps and other decapod crustaceans. These brushes, used to clean the antennal flagellum, occur in some bresiliid shrimp species associated with hydrothermal vents in the Pacific and Atlantic oceans, and recently their presence has been proposed as a distinguishing taxonomic character at the genus level. Occurrence of such brushes in shrimp that live near hydrothermal vents is of interest because of the high number of bacteria associated with these vents. These shrimp have the potential to be heavily fouled with bacteria, whereas at the same time preliminary studies suggest that they may depend upon these bacteria at least in part (or possibly exclusively) for food. We employ scanning electron microscopy to examine and describe the general morphology and location of carpal brushes on the chelipeds of all known species in two vent shrimp genera, Rimicaris Williams and Rona and Chorocaris Martin and Hessler. The brush is well developed and clearly delimited in all known species of Chorocaris, where it consists of a triangular field of serrate setae and a posterior blunt spine that possibly functions as a “stop” to keep the antennal flagellum in place during grooming. Rimicaris exoculata has no recognizable carpal cleaning brush or any serrate setae on the chelipedal carpus and thus appears derived relative to species of Chorocaris with regard to this feature. A newly described species, R. aurantiaca, is somewhat intermediate, having no carpal brush but with two serrate setae and a blunt spine in the region occupied by the brush in species of Chorocaris. Possible implications and comparisons to the genera Alvinocaris and Opapaele are discussed briefly. J. Morphol. 235:31–39, 1998. © 1998 Wiley-Liss, Inc.     

Inhibition of methicillin-resistant Staphylococcus aureus (MRSA) biofilm by cationic poly (D,L-lactide-co-glycolide) nanoparticles

Abstract

The emergent need for new treatment methods for multi-drug resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) has focused attention on novel potential tools like nanoparticles (NPs). In the present study, a drug-free cationic nanoparticles (CNPs) system was developed and its anti-MRSA effects were firstly investigated. The results showed that CNPs (261.7?nm, 26.1?mv) showed time- and concentration-dependent activity against MRSA growth, killing ～ 90% of planktonic bacterial cells in 3?h at 400?μg ml^?1, and completely inhibiting biofilm formation at 1000?μg ml^?1. Moreover, CNPs at 400?μg ml^?1 reduced the minimum inhibitory concentration (MIC) of vancomycin on inhibition of planktonic MRSA growth (～ 25%) and biofilm formation (～ 50%). The CNPs–bacteria interaction force was up to 22 nN. Overall, these data suggest that CNPs have a good potential in clinical applications for the prevention and treatment of MRSA infection.     

ANTIALGAL ACTIVITY OF SOME SIMPLE PHENOLS1

The antialgal activity of a number of simple phenols was examined for their effect on the growth of 7 species of unicellular marine algae. The 3 knoiun algal phenols, 5-bromo-3,4-dihydroxybenzaldehyde; 2,3-dibromo-4,5-dihydroxybenzylalcohol, and 3,4-dihy-droxyphenylethylamine, were highly toxic as were other ortho dihydroxy compounds. Monohydroxy compounds were notably less toxic. Skeletonema costatum and Olisthodiscus sp. were the most sensitive organisms examined and Dunaliella tertiolecta was the most resistant. Possible ecological implications of these results are discussed.     

Barley straw as an inhibitor of algal growth III: the role of fungal decomposition

Rotting barley straw, which is known to inhibit algal growth, has been subjected to mycological examination. A wide range of fungi was isolated from submerged, aerated decomposing straw and tested for antialgal effects againstChlorella on agar plates. Three species, each the dominant isolate from different batches of straw, inhibited the alga. However, the general antialgal effects of decomposing straw are unlikely to be explained by antialgal properties of specific fungi.author for correspondence     

Poly(2-dimethylamino ethylmethacrylate)-based polymers to camouflage red blood cell antigens

Poly(2-dimethylamino-ethylmethacrylate) (PDMAEMA) is a cationic polymer when dissolved in a 7.4 pH fluid. Owing to its ionic nature, this polycation interacts with the negatively charged cell membrane surface of red blood cells (RBCs). The electrostatic self-assembly of PDMAEMA on RBCs membrane can be employed for inducing the formation of a polymeric shield camouflaging blood group antigens on RBCs as a valuable strategy for developing "universal RBCs" for blood transfusion. The purpose of this research was to evaluate the camouflaging ability of PDMAEMA homopolymers and PDMAEMA-co-poly(ethylene glycol) copolymers differing in molecular weight and architecture. Surprisingly, the PDMAEMAs caused a partially masking, no masking, and sensitization of the same RBCs population. The MW and architecture of the polymers as well as temperature of PDMAEMA-RBCs treatment influenced the results observed. Herein, the very particular reactivity of PDMAEMAs and RBCs is analyzed and discussed.     

Minimum requirements of hydrophobic and hydrophilic features in cationic peptide antibiotics (CPAs): pharmacophore generation and validation with cationic steroid antibiotics (CSAs)

Cationic peptide antibiotics (CPAs) are known to possess amphiphilic structure, by virtue of which they display lytic activity against bacterial cell membranes. Naturally occurring antimicrobial peptides contain a large number of amino acid residues, which limits their clinical applicability. Recent studies indicate that it is possible to decrease the chain-length of these peptides without loss of activity, and suggest that a minimum of two positive ionizable (hydrophilic) and two bulky groups (hydrophobic) are required for antimicrobial activity. By employing the HipHop module of the software package CATALYST, we have translated these experimental findings into 3-D pharmacophore models by finding common features among active peptides. Positively ionizable (PI) and hydrophobic (HYD) features are the important characteristics of compounds used for pharmacophore model development. Based on the highest score and the presence of amphiphilic structure, two separate hypothesis, Ec-2 and Sa-6 for Escherichia coli and Staphylococcus aureus, respectively, were selected for mapping analysis of active and inactive peptides against these organisms. The resulting models not only provided information on the minimum requirement of PI and HYD features but also indicated the importance of their relative arrangement in space. The minimum requirement for PI features was two in both cases but the number of HYD features required in the case of E. coli was four while for S. aureus it was found to be three. These hypotheses were able to differentiate between active and inactive CPAs against both organisms and were able to explain the experimental results. The hypotheses were further validated using cationic steroid antibiotics (CSAs), a different class of facial amphiphiles with same mechanism of antimicrobial action as that of CPAs. The results showed that CSAs also require similar minimum features to be active against both E. coli and S. aureus. These studies also indicate that the minimum feature requirements may be conserved for different strains of the same organism. Figure shows the mapping of an active cationic peptide antibiotic (CPA) mapped to the most acceptable hypothesis Sa6 against S. aureus     

STRATEGIES AND RATES OF PHOTOACCLIMATION IN TWO MAJOR SOUTHERN OCEAN PHYTOPLANKTON TAXA: PHAEOCYSTIS ANTARCTICA (HAPTOPHYTA) AND FRAGILARIOPSIS CYLINDRUS (BACILLARIOPHYCEAE)1

We investigated rates and mechanisms of photoacclimation in cultures of Phaeocystis antarctica G. Karst. and Fragilariopsis cylindrus (Grunow) Willi Krieg, phytoplankton taxa that each dominate distinct areas of the Ross Sea, Antarctica. Both P. antarctica and F. cylindrus acclimated to increases in irradiance by reducing the effective size of the pigment antenna (σPSII) via xanthophyll‐cycle activity and reductions in chl. While enhanced photoprotection facilitated increases in specific growth rate and eventually led to higher light‐saturated photosynthetic rates (P^cell_m) in P. antarctica, increases in those variables were much smaller in F. cylindrus. In response to a lower irradiance, relaxation of xanthophyll‐cycle activity led to an increase in σPSII in both taxa, which occurred much more slowly in F. cylindrus. A surprising increase in specific growth rate over the first 36 h of acclimation in P. antarctica may have facilitated the significant reductions in P^cell_m observed in that taxon. In general, P. antarctica acclimated more quickly to changes in irradiance than F. cylindrus, exhibited a wider range in photosynthetic rates, but was more susceptible to photoinhibition. This acclimation strategy is consistent with growth in deeply mixed water columns with variations in irradiance that allow time for repair. In contrast, the slower acclimation rates, extensive photoprotection, and low photoinhibition exhibited by F. cylindrus suggest that it does not require the same period for repair as P. antarctica and is best suited for growth in habitats with relatively uniform irradiance, such as shallow mixed layers or sea ice.     

Effect of low-molecular-weight proteins on protein (lysozyme) binding to isolated brush-border membranes of rat kidney

Filtered proteins including the low-molecular-weight protein lysozyme are reabsorbed by the proximal tubule via adsorptive endocytosis. This process starts with binding of the protein to the brush-border membrane. The binding of ¹²⁵I-labelled egg-white lysozyme (EC 3.2.1.17) to isolated brush-border membranes of rat kidney and the effect of several low-molecular weight proteins on that binding was determined. The Scatchard plot revealed a one-component binding type with a dissociation constant of 5.3 μM and 53.0 nmol/mg membrane protein for the number of binding sites. The binding of the cationic lysozyme was inhibited competitively by the addition of cationic cytochrome c to the incubation medium, while the neutral myoglobin had no effect. The anionic β-lactoglobulin A inhibited the lysozyme binding in a noncompetitive manner. These data suggest that the binding takes place between positively charged groups of the protein molecule and negative sites on the brush-border membrane, and, the competition between the cationic cytochrome c and the cationic lysozyme for the binding sites may be responsible for the inhibitory effect of cytochrome c on renal lysozyme reabsorption. The binding step at the brush-border membrane appears to be cation-selective.     

Phylogenetic relationships of Acronictinae with discussion of the abdominal courtship brush in Noctuidae (Lepidoptera)

We present results of an eight‐gene molecular study of the subfamily Acronictinae and related Noctuidae. Amphipyrinae are recovered as sister to Acronictinae, but with weak support – not surprisingly, the content of the two subfamilies has often been mixed in classifications. Balsinae, previously placed near Acronictinae or within Noctuinae, is recovered within an unresolved polytomy of Cuculliinae, Eustrotiinae, Raphiinae and Dilobinae. Gerbathodes Warren, Moma Hübner and Nacna Fletcher are excluded from Acronictinae. Three genera recently transferred into the subfamily – Cerma Hübner, Chloronycta Schmidt & Anweiler and Comachara Franclemont – are confirmed as acronictines. Lophonycta Sugi (the type genus of Lophonyctinae) is returned to the Acronictinae. Sinocharis Püngeler, formerly considered to be Acontiinae or as the basis of its own subfamily Sinocharinae, is nested within early diverging Acronictinae genera. Both subfamilies are formally synonymized: i.e. Lophonyctinae syn.n. and Sinocharinae syn.n. Nine acronictine genus‐level taxa were found to nest within the nominate genus Acronicta Ochsenheimer: Eogena Guenée, Hyboma Hübner, Hylonycta Sugi, Jocheaera Hübner, Oxicesta Hübner, Simyra Ochsenheimer, Subacronicta Kozhanchikov, Triaena Hübner, and Viminia Chapman. Eogena, Oxicesta, and Simyra, currently treated as valid genera, nest within terminal clades of the genus Acronicta and are here subsumed within the genus: Eogena syn.n. , Oxicesta syn.n. and Simyra syn.n. Four well‐supported species groups within Acronicta are identified: the alni clade, the leporina clade, the nervosa clade and the psi clade. While many previous treatments have stated explicitly that Acronictinae lack abdominal scent brushes, or excluded genera with brushes from the subfamily, we show that well‐developed brushes are present in three early diverging acronictine genera: Cerma, Lophonycta, and Sinocharis. We illustrate and describe the brushes of all three genera, and briefly review the taxonomic distribution of the anterior abdominal courtship brushes in Noctuidae, emphasizing the labile evolutionary distribution of these structures.