Marine microbial natural products in antifouling coatings

Ecological problems associated with current antifouling technologies have increased interest in the natural strategies that marine organisms use to keep their surfaces clean and free from fouling. Bacteria isolated from living surfaces in the marine environment have been shown to produce chemicals that are potential antifoulants. Active compounds from the cells and culture supernatant of two bacterial strains, FS‐55 and NudMB50–11, isolated from surface of the seaweed, Fucus serratus, and the nudibranch, Archidoris pseudoargus, respectively, were extracted using solid phase extraction. The extracts were combined with acrylic base paint resin and assayed for antifouling activity by measuring their ability to inhibit the growth of fouling bacteria. These formulations were found to be active against fouling bacteria isolated from marine surfaces. The formulation of antifouling paints that incorporate marine microbial natural products is reported here for the first time. This is a significant advance towards the production of an environmentally friendly antifouling paint that utilises a sustainable supply of natural biodegradable compounds.     

The study of antagonistic interactions among pelagic bacteria: a promising way to coin environmental friendly antifouling compounds

Ten strains of marine bacteria (SCH0401–SCH0410) were isolated from Ayajin, the east coast of South Korea. In spectrophotometer based chemotaxis assay the ethyl acetate extract (300 μg) of SCH0402 decreased the optical density (OD) of the motile target strains SCH0401, SCH0402, SCH0407 and SCH0408 by two to six times when compared to control. Tributyltin oxide (TBTO) decreased the OD of all target strains by only two times. The most active strain SCH0402 was identified as Shewanella oneidensis by using 16S rDNA gene sequence analysis. Similarly, the target motile strains SCH0401, SCH0402, SCH0407 and SCH0408 were identified as Alteromonas marina, Shewanella oneidensis, Roseobacter gallaeciensis and Bacillus atrophaeus, respectively. The growth inhibition zone produced by the test bacterial extracts against the target strains were three to eight times smaller when compared to that of TBTO. Even though, SCH0402 showed six times weaker antibacterial activity, the repellent activity was three times stronger than TBTO. Therefore, the higher negative chemotactic activity would be better to select eco-friendly antifouling compounds than the other antibacterial activities.     

Antimicrobial activity of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> strains

A bacterial strain with a high level of antimicrobial activity was isolated from soil and identified as Bacillus megaterium. Production of antibiotics by nine strains of this species from the collection of the State Research Institute for Genetics and Selection of Industrial Microorganisms was investigated. In submerged cultures, nine out of ten B. megaterium strains were found to produce antibacterial antibiotics differing in their spectra of action. Physicochemical characteristics of five compounds were described. Three of them belonged to peptide antibiotics. All five compounds were active against the methicillin-resistant strain Staphylococcus aureus INA 00761. Three of them were shown to be the previously undescribed compounds. Antibiotics produced by various B. megaterium strains were also active against the Leuconostoc mesenteroides VKPM B-4177 strain resistant to glycopeptide antibiotics and against gram-negative bacteria Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922.     

Antifungal compounds produced by bacterial populations of the Sea SpongeVerongia sp.

The taxonomic structure and some metabolic features of the bacterial populations of the sea spongeVerongia sp were studied. Twenty-three symbiotrophic strains were isolated into axenic cultures and identified. These wereProteobacteria of the generaPseudoalteromonas andVibrio (about 52%), firmicutes with low G+C content (up to 22%), and bacteria of the generaFlavobacterium/Cytophaga/Bacteroides (13% of the strains studied). The strain KMM 3427, identified asBacillus subtilis, synthesized the secondary metabolite 2-p-hydroxyphenylalcohol (tyrosol), which is known to be an antifungal compound and may perform the function of chemical defence inVerongia sp.     

Surface metabolites of the brown alga Taonia atomaria have the ability to regulate epibiosis

This study aimed to improve understanding of the strategies developed by the Mediterranean seaweed Taonia atomaria to chemically control bacterial epibiosis. An experimental protocol was optimized to specifically extract algal surface-associated metabolites by a technique involving dipping in organic solvents whilst the integrity of algal cell membranes was assessed by fluorescent microscopy. This methodology was validated using mass spectrometry-based profiles of algal extracts and analysis of their principal components, which led to the selection of methanol as the extraction solvent with a maximum exposure time of 15 s. Six compounds (A–F) were identified in the resulting surface extracts. Two of these surface-associated compounds (B and C) showed selective anti-adhesion properties against reference bacterial strains isolated from artificial surfaces while remaining inactive against epibiotic bacteria of T. atomaria. Such specificity was not observed for commercial antifouling biocides and other molecules identified in the surface or whole-cell extracts of T. atomaria.     

Resistance of biofilms containing alginate‐producing bacteria to disintegration by an alginate degrading enzyme (Algl)

Pure culture biofilms of Pseudomonas aeruginosa (strains 8830 and ATCC 700829) and mixed population biofilms composed of Pseudomonas aeruginosa (ATCC 700829), Pseudomonas fluorescens (ATCC 700830), and Klebsiellapneumoniae (ATCC 700831) were treated with an alginate‐degrading enzyme (AlgL). The enzyme effectively depolymerized the mannuronic acid rich (92%), partially O‐acetylated bacterial alginate produced by P. aeruginosa (8830), both in dilute solution and in a gel‐like, concentrated state. However, both biofilms were unaffected by the presence of the enzyme. These findings suggest either that bacterial alginates do not contribute significantly to the cohesiveness of biofilms or that the alginate is protected from enzymatic degradation in biofilms.     

Plant growth promotion abilities and formulation of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> strain B 388 (MTCC6521) isolated from a temperate Himalayan location

Bacillus megaterium strain B388, isolated from rhizosphere soil of pine belonging to a temperate Himalayan location has been characterized. The plant growth promotion and biocontrol properties of the bacterium have been evaluated through petridish and broth based assays. The isolate solubilized tricalcium phosphate under in vitro conditions; maximum activity (166 μg/ml) was recorded at 28°C after 15 days of incubation. Production of indole acetic acid demonstrated in broth assays was another important plant growth promoting character. The bacterium produced diffusible and volatile compounds that inhibited the growth of two phytopathogens viz. Alternaria alternata and Fusarium oxysporum. The carrier based formulations of the bacterium resulted in increased plant growth in bioassays. The rhizosphere colonization and the viability of the cells entrapped in alginate beads were greater in comparison to coal or broth based formulations. The bacterium showed maximum similarity with Bacillus megaterium by 16S rRNA analysis.     

Identification of some Bacteria from Paddy Antagonistic to Several Rice Fungal Pathogens

The effect of 23 bacterial strains from ricefields in the tropics on rice seed germination and on radicle and hypocotyl development of four rice cultivars was determined. There was a varietal difference in response to seed bacterization with the different bacterial strains. Germination of cv. IR58 increased from 78 to 93 %, that of cv. IR64, from 89 to 97 %. Less effects on germination of cvs IR42 and IR36 were observed. All strains inhibited the mycelial growth of Rhizoctonia solani in vitro. The three strains, identified as Bacillus subtilis, inhibited the mycelial growth of eight fungal pathogens whereas the other strains were pathogen-specific. Seed bacterization with these bacterial strains provided a sheath blight protection of 4. 5 to 73 % in the glasshouse trial. These 23 bacterial strains were identified by phenotypic tests using the API systems, morphological and biochemical features, and by comparison of electrophoretic patterns after sodium dodecyl sulphate polyacrylamide gel electrophoresis. Bacterial strains were identified (number of strains in brackets) as: Bacillus subtilis (3), Bacillus laterosporus (1), Bacillus pumilus (1), Pseudomonas aeruginosa (7), Pseudomonas belonging to section 1 (5), Erwina herbicola-like (1), and Serratia marcescens (1). The features of the other four strains were similar to Serratia except for the DNAase and lipase activities.     

甲基营养型芽孢杆菌拮抗玉蜀黍尾孢菌、链格菌和灰葡萄孢菌及环脂肽分析

[目的]探究甲基营养型芽孢杆菌(Bacillus methylotrophicus)对植物病原菌玉蜀黍尾孢菌(Cercospora zeae-maydis Tehon et Daniels)、链格菌(Alternaria alternate)和灰葡萄孢菌(Botrytis cinerea)的拮抗作用并鉴定抗菌物质,为其...     

Phenoloxidase (E.C. 1.14.18.1) from the byssus gland of Mytilus edulis: Purification,partial characterization and application for screening products with potential antifouling activities

Although a total ban on the use of TBT coatings is not expected in the short term, there is a growing need for environmentally safe antifouling systems. To assist in the rapid screening of a large number of potential antifouling substances, a method that is simple, efficient and inexpensive is required. The production of byssus threads by the blue mussel, Mytilus edulis, has often been studied for testing the antifouling efficacy of various compounds. The present study reports a new antifouling assay based on the inhibition of purified M. edulis phenoloxidase activity. The method has the advantage of being specific, reliable, sensitive and rapid.     

Antibacterial,antifungal and cytotoxic properties of some sulfonamide-derived chromones

A series of antibacterial and antifungal sulfonamide (sulfanilamide, sulfaguanidine, sulfamethaxozole, 4-aminoethylbenzenesulfonamide and 4-amino-6-trifluoromethyl-benzene-1,3-disulfonamide) derived chromones, previously reported as inhibitors of carbonic anhydrase, have been screened for in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Shigella flexeneri) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains, and for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, Candida glaberata. All compounds (1)–(5) showed significant antibacterial activity against all four Gram-negative species and both Gram-positive species. However, three of them, (1), (4) and (5), were found to be comparatively much more active compared to (2) and (3). Of these, (5) was found to be the most active one. For antifungal activity, generally compounds (1) and (2) showed significant activity against more than three strains whereas (3)–(5) also showed significant activity against varied fungal strains. In the brine shrimp bioassay for in-vitro cytotoxic properties, only two compounds, (4) and (5) displayed potent cytotoxic activity, LD₅₀ = 2.732 × 10^{? 4} M) and LD₅₀ = 2.290 × 10^{? 4} M) respectively, against Artemia salina.     

Carrier-based Preparations of Plant Growth-promoting Bacterial Inoculants Suitable for use in Cooler Regions

Summary Carrier-based preparations of two plant growth-promoting rhizobacteria (PGPR) viz. Bacillus subtilis and Pseudomonas corrugata, developed in five formulations were evaluated for their growth promotion, rhizosphere colonization, and viability under storage. The effect of these formulations as fresh preparations, and after 6 months of storage at 4 °C and room temperature, was also determined. The bacterial inoculants in all the formulations were found to enhance the growth parameters of the test plant species; best results were obtained in case of alginate-based formulations. Maximum numbers of inoculated bacteria were recovered from the rhizosphere of alginate-based formulation-treated plants after 6 weeks of growth. Viability of bacterial inoculants was maximal in alginate beads, and alginate beads supplemented with skim milk formulations, after 180 days of storage at 4 °C.     

Potential of rhizobacteria for prohibition of potato golden cyst nematode activity

Potato golden cyst nematode is an important causal agent of potato disease. Nematode cysts were isolated and identified by phenotypic and genotypic characteristics. Biocontrol activity of 120 isolated bacteria from rhizosphere towards Globodera rostochiensis, were evaluated. Nematode cysts were exposed to root extracts and released juveniles (J2) subjected to cultural filtrate of isolated bacteria and their mortality were recorded after 24 and 48 h. In total, 33 strains showed inhibitory activities which they caused mortality ranged from 61.10% to 78.74%. Five representatives of inhibitory strains were applied on potato cultivar Marfona under greenhouse conditions using tuber coating and soil drenching in a complete randomised block design with three replicates. The active bacterial strains were identified as Bacillus subtilis, Bacillus megaterium, Pseudomonas fluorescens bv. I, P. fluorescens bv. II and P. putida bv. B. In the greenhouse, significant differences were observed among the tested strains, where the highest disease severity reduction was 42.31%.     

Inhibitory Effects of Mediterranean Sponge Extracts and Metabolites on Larval Settlement of the Barnacle Balanus amphitrite

One of the most promising alternative technologies to antifouling paints based on heavy metals is the development of coatings whose active ingredients are compounds naturally occurring in marine organisms. This approach is based on the problem of epibiosis faced by all marine organisms and the fact that a great number of them cope with it successfully. The present study investigated the antifouling activity of a series of extracts and secondary metabolites from the epibiont-free Mediterranean sponges Ircinia oros, I. spinosula, Cacospongia scalaris, Dysidea sp., and Hippospongia communis. Antifouling efficacy was evaluated by the settlement inhibition of laboratory-reared Balanus amphitrite Darwin cyprids. The most promising activity was exhibited by the metabolites 2-[24-acetoxy]-octaprenyl-1-4-hydroquinone (8a), dihydrofurospongin II (10), and the alcoholic extract of Dysidea sp.     

Competitive Induction and Enhancement of Indole and a Diketopiperazine in Marine Bacteria

Thirteen bacterial strains isolated from a sample of Ulva californica were cultured, extracted, and assayed for antibiotic activity. The target strains were 2 gram-positive isolates from the same algal sample. When cultured in monoculture, 2 of the 13 isolates produced extracts with antimicrobial activity. More significantly, one Bacillus isolate (UA-094) produced indole and cyclo(Phe-Pro) at active levels upon challenge with a different Bacillus target strain. These mildly antibiotic compounds were barely detectable in extracts without challenge. This technique of competitive induction and enhancement could be a valuable tool in the search for new antibiotics.     

Bacillus halotolerans strain LYSX1-induced systemic resistance against the root-knot nematode Meloidogyne javanica in tomato

Purpose

Determination of the nematicidal potential and mode of action of bacteria isolated from tobacco rhizosphere soil against the root-knot nematode Meloidogyne javanica in tomato plants.

Methods

Antagonistic bacteria were isolated from rhizosphere soil of tobacco infested with root-knot nematodes. Culture filtrate was used to examine nematicidal activity and ovicidal action of bacterial strains. Biocontrol of M. javanica and growth of treated tomato plants were assessed in pot experiments. To clarify whether secondary metabolites of bacteria in tomato roots induced systemic resistance to M. javanica, bacterial culture supernatants and second-stage juvenile nematodes were applied to spatially separated tomato roots using a split-root system. Bacterial strains were identified by 16S rDNA and gyrB gene sequencing and phylogenetic analysis.

Results

Of the 15 bacterial strains isolated, four (LYSX1, LYSX2, LYSX3, and LYSX4) demonstrated nematicidal activity against second-stage juveniles of M. javanica, and strain LYSX1 showed the greatest antagonistic activity; there was dose-dependent variability in nematicidal activity and inhibition of egg mass hatching by strain LYSX1. In vivo application of LYSX1 to tomato seedlings decreased the number of egg masses and galls and increased the root and shoot fresh weight. Treatment of half of the split-root system with LYSX1 reduced nematode penetration to the other half by 41.64%. Strain LYSX1 was identified as Bacillus halotolerans.

Conclusion

Bacillus halotolerans LYSX1 is a potential microbe for the sustainable biocontrol of root-knot nematodes through induced systemic resistance in tomato.

     

Recovery of plant growth-promoting rhizobacteria from sodium alginate beads after 3 years following storage at 4 °C

Two plant growth-promoting bacteria, Bacillus subtilis and Pseudomonas corrugata, immobilized in a sodium alginate based formulation were evaluated for their survival, viability and plant growth-promoting ability after 3 years of storage at 4 °C. Populations of both of the bacterial isolates recovered from the immobilized sodium alginate beads were in the order of 10⁸ cfu g⁻¹. The plant-based bioassay indicated that the plant growth promotion ability of both of the bacterial isolates was equal to those of fresh broth-based formulations. The bacterial isolates retained the root colonization, and antifungal and enzyme activities in the alginate-based formulation during storage.     

Novel depsides as potential anti-inflammatory agents with potent inhibitory activity against Escherichia coli-induced interleukin-8 production

Sixteen novel depsides were synthesized for the first time. Their chemical structures were clearly determined by ¹H NMR, ESI mass spectra, and elemental analyses. All the compounds were assayed for antibacterial activities against three Gram-positive bacterial strains (Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 6538, and Streptococcus faecalis ATCC 9790) and three Gram-negative bacterial strains (Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 13525, and Enterobacter cloacae ATCC 13047) by the MTT method. Compound 2-(2-methoxy-2-oxoethyl)phenyl 5-bromonicotinate (5) exhibited significant antibacterial activities against E. coli ATCC 35218 with an MIC of 0.78 μg/mL, which was superior to the positive control kanamycin B. In addition, compound 5 showed potent inhibitory activity against E. coli-induced interleukin-8 production.     

Screening of Marine Algal Extracts for Anti-settlement Activities against Microalgae and Macroalgae

The ban on the use of TBT-based antifouling paints for boats under 25 m in length has lead to a search for new non-toxic antifoulants. One of the most promising alternative technologies to heavy metal based antifouling paint is the development of antifouling coatings whose active ingredients are naturally occurring compounds from marine organisms. This is based on the principle that marine organisms also face the problem of the presence of epibionts on their own surfaces. In this study, the antifouling activity of a series of aqueous, ethanolic and dichloromethane extracts from thirty algae from the North East Atlantic coast was investigated. The extracts were tested in laboratory assays against species representative of two major groups of fouling organisms, viz . macroalgae and microalgae. The activity of several extracts was comparable to that of heavy metals and biocides (such as TBTO and CuSO 4 ) currently used in antifouling paints and their lack of toxicity with respect to the larvae of oysters and sea urchins suggests a potential for novel active ingredients.     

Metal-based ethanolamine-derived compounds: a note on their synthesis,characterization and bioactivity

Abstract

Metal-based ethanolamines, (L¹)–(L⁴) coordinated with Co(II), Cu(II), Ni(II) and Zn(II) metals in 1:2 (metal:ligand) molar ratio to produce new compounds have been reported. These compounds were screened for their bactericidal/fungicidal activity against a number of bacterial (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus and Bacillus subtilis) and fungal strains (Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata) alongside against a shrimp species known as Artemia salina. The screening results indicated that metal complexes have significantly higher activity than uncomplexed ligands against one or more bacterial/fungal species due to chelation. The ligand (L⁴) displayed good bacterial and fungal activity as compared to other ligands. The antibacterial results revealed that the Zn(II) complex (16) of (L⁴) was found to be the most active complex and Co(II) complex (14) of the same ligand (L⁴), demonstrated the highest antifungal activity.