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1.
ISME J ; 14(6): 1614-1625, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32203123

RESUMO

With each cell division, phytoplankton create new space for primary colonization by marine bacteria. Although this surface microenvironment is available to all planktonic bacterial colonizers, we show the assembly of bacterial consortia on a cosmopolitan marine diatom to be highly specific and reproducible. While phytoplankton-bacteria interactions play fundamental roles in marine ecosystems, namely primary production and the carbon cycle, the ecological paradigm behind epiphytic microbiome assembly remains poorly understood. In a replicated and repeated primary colonization experiment, we exposed the axenic diatom Thalassiosira rotula to several complex and compositionally different bacterial inocula derived from phytoplankton species of varying degrees of relatedness to the axenic Thalassiosira host or natural seawater. This revealed a convergent assembly of diverse and compositionally different bacterial inocula, containing up to 2071 operational taxonomic units (OTUs), towards a stable and reproducible core community. Four of these OTUs already accounted for a cumulative abundance of 60%. This core community was dominated by Rhodobacteraceae (30.5%), Alteromonadaceae (27.7%), and Oceanospirillales (18.5%) which was qualitatively and quantitatively most similar to its conspecific original. These findings reject a lottery assembly model of bacterial colonization and suggest selective microhabitat filtering. This is likely due to diatom host traits such as surface properties and different levels of specialization resulting in reciprocal stable-state associations.

2.
Proc Natl Acad Sci U S A ; 117(12): 6599-6607, 2020 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-32170018

RESUMO

Marine microalgae sequester as much CO2 into carbohydrates as terrestrial plants. Polymeric carbohydrates (i.e., glycans) provide carbon for heterotrophic organisms and constitute a carbon sink in the global oceans. The quantitative contributions of different algal glycans to cycling and sequestration of carbon remain unknown, partly because of the analytical challenge to quantify glycans in complex biological matrices. Here, we quantified a glycan structural type using a recently developed biocatalytic strategy, which involves laminarinase enzymes that specifically cleave the algal glycan laminarin into readily analyzable fragments. We measured laminarin along transects in the Arctic, Atlantic, and Pacific oceans and during three time series in the North Sea. These data revealed a median of 26 ± 17% laminarin within the particulate organic carbon pool. The observed correlation between chlorophyll and laminarin suggests an annual production of algal laminarin of 12 ± 8 gigatons: that is, approximately three times the annual atmospheric carbon dioxide increase by fossil fuel burning. Moreover, our data revealed that laminarin accounted for up to 50% of organic carbon in sinking diatom-containing particles, thus substantially contributing to carbon export from surface waters. Spatially and temporally variable laminarin concentrations in the sunlit ocean are driven by light availability. Collectively, these observations highlight the prominent ecological role and biogeochemical function of laminarin in oceanic carbon export and energy flow to higher trophic levels.

3.
Mar Drugs ; 16(11)2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30441860

RESUMO

Cyclic imine toxins are neurotoxic, macrocyclic compounds produced by marine dinoflagellates. Mass spectrometric screenings of extracts from natural plankton assemblages revealed a high chemical diversity among this toxin class, yet only few toxins are structurally known. Here we report the structural characterization of four novel cyclic-imine toxins (two gymnodimines (GYMs) and two spirolides (SPXs)) from cultures of Alexandrium ostenfeldii. A GYM with m/z 510 (1) was identified as 16-desmethylGYM D. A GYM with m/z 526 was identified as the hydroxylated degradation product of (1) with an exocyclic methylene at C-17 and an allylic hydroxyl group at C-18. This compound was named GYM E (2). We further identified a SPX with m/z 694 as 20-hydroxy-13,19-didesmethylSPX C (10) and a SPX with m/z 696 as 20-hydroxy-13,19-didesmethylSPX D (11). This is the first report of GYMs without a methyl group at ring D and SPXs with hydroxyl groups at position C-20. These compounds can be conceived as derivatives of the same nascent polyketide chain, supporting the hypothesis that GYMs and SPXs are produced through common biosynthetic genes. Both novel GYMs 1 and 2 were detected in significant amounts in extracts from natural plankton assemblages (1: 447 pg; 2: 1250 pg; 11: 40 pg per mL filtered seawater respectively).


Assuntos
Dinoflagelados/química , Compostos Heterocíclicos com 3 Anéis/química , Hidrocarbonetos Cíclicos/química , Iminas/química , Toxinas Marinhas/química , Fitoplâncton/química , Compostos de Espiro/química , Compostos Heterocíclicos com 3 Anéis/isolamento & purificação , Hidrocarbonetos Cíclicos/isolamento & purificação , Iminas/isolamento & purificação , Toxinas Marinhas/isolamento & purificação , Estrutura Molecular , Compostos de Espiro/isolamento & purificação
4.
J Nat Prod ; 81(2): 400-404, 2018 02 23.
Artigo em Inglês | MEDLINE | ID: mdl-29381357

RESUMO

Three new and seven known calopins were isolated from Caloboletus radicans. The structures of the new cyclocalopins, 8-deacetylcyclocalopin B (1), cyclocalopin A-15-ol (2), and 12,15-dimethoxycyclocalopin A (3), were mainly elucidated by NMR and MS data analysis. The stereochemistry of 1-3 was assigned based on NOE correlations and coupling constants and by comparison of their CD spectra with those of similar known calopins. While 1-10 were inactive against two cancer cell lines, they displayed anti-staphylococcal activity against methicillin-resistant Staphylococcus aureus strains (MRSA) with MIC values of 16-256 µg/mL. Moreover, some calopins were active against the fish pathogen Enterococcus faecalis F1B1.


Assuntos
Antibacterianos/química , Carpóforos/química , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Agaricales/química , Linhagem Celular Tumoral , Enterococcus faecalis/efeitos dos fármacos , Células Hep G2 , Humanos , Testes de Sensibilidade Microbiana/métodos , Infecções Estafilocócicas/tratamento farmacológico
5.
FEMS Microbiol Ecol ; 91(1): 1-9, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25764535

RESUMO

Most marine invertebrates have dispersive larvae and relatively immobile adults. These developmental stages are linked by a settlement event, which is often mediated by specific cues in bacterial biofilms. While larvae distinguish between biofilms from different environments, it remains unknown if they receive information from all, only a few or even just a single bacterial species in natural biofilms. Here we asked how specific is larval settlement to the bacterial community structure and/or taxonomically distinguishable groups of bacteria in epiphytic marine biofilms? We used novel multivariate statistical approaches to investigate if larval settlement of two sea urchins correlated with the microbial community composition. Larval settlement of Heliocidaris erythrogramma revealed a strong correlation with the community composition, highlighted by canonical analysis of principle components, a constrained ordination technique. Using this technique, the importance of operational taxonomic units (OTUs) within communities relative to larval settlement was investigated. Larval settlement not only correlated, both positively and negatively, with the epiphytic bacterial community composition but also with the relative abundance of few OTUs within these communities. In contrast, no such correlation was observed for the other urchin, Holopneustes purpurascens, whose larvae likely respond to bacterial biofilms in a more general way and specifically respond to a defined settlement cue of algal origin.


Assuntos
Bactérias/classificação , Biofilmes , Larva/fisiologia , Locomoção/fisiologia , Ouriços-do-Mar/fisiologia , Animais , Metamorfose Biológica
6.
Mar Drugs ; 12(5): 2802-15, 2014 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-24828288

RESUMO

The ethanol extract of Pseudoalteromonas strain J010, isolated from the surface of the crustose coralline alga Neogoniolithon fosliei, yielded thirteen natural products. These included a new bromopyrrole, 4'-((3,4,5-tribromo-1H-pyrrol-2-yl) methyl)phenol (1) and five new korormicins G-K (2-6). Also isolated was the known inducer of coral larval metamorphosis, tetrabromopyrrole (TBP), five known korormicins (A-E, previously named 1, 1a-c and 3) and bromoalterochromide A (BAC-A). Structures of the new compounds were elucidated through interpretation of spectra obtained after extensive NMR and MS investigations and comparison with literature values. The antibacterial, antifungal and antiprotozoal potential of 1-6, TBP and BAC-A was assessed. Compounds 1-6 showed antibacterial activity while BAC-A exhibited antiprotozoal properties against Tetrahymena pyriformis. TBP was found to have broad-spectrum activity against all bacteria, the protozoan and the fungus Candida albicans.


Assuntos
Antozoários/microbiologia , Pseudoalteromonas/química , Pirróis/química , Rodófitas/química , Animais , Antibacterianos/farmacologia , Antifúngicos/farmacologia , Antiprotozoários/farmacologia , Ácidos Graxos Insaturados/química , Ácidos Graxos Insaturados/isolamento & purificação , Ácidos Graxos Insaturados/farmacologia , Lactonas/química , Lactonas/isolamento & purificação , Lactonas/farmacologia , Testes de Sensibilidade Microbiana , Pirróis/isolamento & purificação , Pirróis/farmacologia , Tetrahymena pyriformis/efeitos dos fármacos
7.
PLoS One ; 9(3): e91082, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24632854

RESUMO

The morphogenetic transition of motile coral larvae into sessile primary polyps is triggered and genetically programmed upon exposure to environmental biomaterials, such as crustose coralline algae (CCA) and bacterial biofilms. Although the specific chemical cues that trigger coral larval morphogenesis are poorly understood there is much more information available on the genes that play a role in this early life phase. Putative chemical cues from natural biomaterials yielded defined chemical samples that triggered different morphogenetic outcomes: an extract derived from a CCA-associated Pseudoalteromonas bacterium that induced metamorphosis, characterized by non-attached metamorphosed juveniles; and two fractions of the CCA Hydrolithon onkodes (Heydrich) that induced settlement, characterized by attached metamorphosed juveniles. In an effort to distinguish the genes involved in these two morphogenetic transitions, competent larvae of the coral Acropora millepora were exposed to these predictable cues and the expression profiles of 47 coral genes of interest (GOI) were investigated after only 1 hour of exposure using multiplex RT-qPCR. Thirty-two GOI were differentially expressed, indicating a putative role during the early regulation of morphogenesis. The most striking differences were observed for immunity-related genes, hypothesized to be involved in cell recognition and adhesion, and for fluorescent protein genes. Principal component analysis of gene expression profiles resulted in separation between the different morphogenetic cues and exposure times, and not only identified those genes involved in the early response but also those which influenced downstream biological changes leading to larval metamorphosis or settlement.


Assuntos
Antozoários/genética , Metamorfose Biológica/fisiologia , Animais , Recifes de Corais , Perfilação da Expressão Gênica , Metamorfose Biológica/genética
8.
PLoS One ; 9(1): e87545, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24489936

RESUMO

The early post-settlement stage is the most sensitive during the life history of reef building corals. However, few studies have examined the factors that influence coral mortality during this period. Here, the impact of fouling on the survival of newly settled coral spat of Acropora millepora was investigated by manipulating the extent of fouling cover on settlement tiles using non-toxic, wax antifouling coatings. Survival of spat on coated tiles was double that on control tiles. Moreover, there was a significant negative correlation between percentage cover of fouling and spat survival across all tiles types, suggesting that fouling in direct proximity to settled corals has detrimental effects on early post-settlement survival. While previous studies have shown that increased fouling negatively affects coral larval settlement and health of juvenile and adult corals, to the best of our knowledge, this is the first study to show a direct relationship between fouling and early post-settlement survival for a broadcast spawning scleractinian coral. The negative effects of fouling on this sensitive life history stage may become more pronounced in the future as coastal eutrophication increases. Our results further suggest that targeted seeding of coral spat on artificial surfaces in combination with fouling control could prove useful to improve the efficiency of sexual reproduction-based coral propagation for reef rehabilitation.


Assuntos
Antozoários/fisiologia , Parafina , Animais , Incrustação Biológica/prevenção & controle , Conservação dos Recursos Naturais , Recifes de Corais , Larva/fisiologia , Dinâmica Populacional
9.
FEMS Microbiol Ecol ; 84(2): 411-20, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23311942

RESUMO

The macroalga Fucus vesiculosus carries a specific community of surface bacteria. To identify chemical compounds that possibly mediate abundance and community composition of algae-associated bacteria, we tested the effect of surface-available algal compounds on bacterial settlement and community composition under field conditions. Compounds on algal thalli were separated from the surface by extraction with organic solvents and investigated on growth inhibition and settlement of bacterial isolates. Based on in vitro data, partially purified extract fractions were then exposed to bacterial colonizers in vivo followed by bacterial enumeration and community analysis. The polar fraction of the algal surface extract revealed a significant profouling effect for Vibrionales, whereas the nonpolar fraction - containing the xanthophyll pigment fucoxanthin and other unidentified nonpolar surface compounds - revealed a significant 80% reduction of surface colonizing bacteria. The analysis of bacterial surface communities by 454 pyrosequencing demonstrated that the antifouling activity of nonpolar algal surface compounds was targeting the abundance of natural bacterial colonizers rather than the relative composition of bacterial members within the community. Moreover, the bacterial community composition on F. vesiculosus was markedly different from artificial control substrates and chemically manipulated experimental treatments, suggesting that other, nonextractable surface features and/or physical properties render algal-specific epiphytic bacterial communities.


Assuntos
Bactérias/classificação , Fucus/microbiologia , Alga Marinha/microbiologia , Antibacterianos/química , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Bactérias/isolamento & purificação , Fucus/química , Alga Marinha/química , Xantofilas/análise
10.
FEMS Microbiol Rev ; 37(3): 462-76, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23157386

RESUMO

Seaweeds (macroalgae) form a diverse and ubiquitous group of photosynthetic organisms that play an essential role in aquatic ecosystems. These ecosystem engineers contribute significantly to global primary production and are the major habitat formers on rocky shores in temperate waters, providing food and shelter for aquatic life. Like other eukaryotic organisms, macroalgae harbor a rich diversity of associated microorganisms with functions related to host health and defense. In particular, epiphytic bacterial communities have been reported as essential for normal morphological development of the algal host, and bacteria with antifouling properties are thought to protect chemically undefended macroalgae from detrimental, secondary colonization by other microscopic and macroscopic epibiota. This tight relationship suggests that macroalgae and epiphytic bacteria interact as a unified functional entity or holobiont, analogous to the previously suggested relationship in corals. Moreover, given that the impact of diseases in marine ecosystems is apparently increasing, understanding the role of bacteria as saprophytes and pathogens in seaweed communities may have important implications for marine management strategies. This review reports on the recent advances in the understanding of macroalgal-bacterial interactions with reference to the diversity and functional role of epiphytic bacteria in maintaining algal health, highlighting the holobiont concept.


Assuntos
Fenômenos Fisiológicos Bacterianos , Biodiversidade , Interações Hospedeiro-Patógeno , Metagenoma , Alga Marinha/microbiologia , Simbiose , Bactérias/metabolismo , Bactérias/patogenicidade
11.
PLoS One ; 7(5): e37774, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22655067

RESUMO

Biofilms of the bacterium Pseudoalteromonas induce metamorphosis of acroporid coral larvae. The bacterial metabolite tetrabromopyrrole (TBP), isolated from an extract of Pseudoalteromonas sp. associated with the crustose coralline alga (CCA) Neogoniolithon fosliei, induced coral larval metamorphosis (100%) with little or no attachment (0-2%). To better understand the molecular events and mechanisms underpinning the induction of Acropora millepora larval metamorphosis, including cell proliferation, apoptosis, differentiation, migration, adhesion and biomineralisation, two novel coral gene expression assays were implemented. These involved the use of reverse-transcriptase quantitative PCR (RT-qPCR) and employed 47 genes of interest (GOI), selected based on putative roles in the processes of settlement and metamorphosis. Substantial differences in transcriptomic responses of GOI were detected following incubation of A. millepora larvae with a threshold concentration and 10-fold elevated concentration of TBP-containing extracts of Pseudoalteromonas sp. The notable and relatively abrupt changes of the larval body structure during metamorphosis correlated, at the molecular level, with significant differences (p<0.05) in gene expression profiles of 24 GOI, 12 hours post exposure. Fourteen of those GOI also presented differences in expression (p<0.05) following exposure to the threshold concentration of bacterial TBP-containing extract. The specificity of the bacterial TBP-containing extract to induce the metamorphic stage in A. millepora larvae without attachment, using a robust, low cost, accurate, ecologically relevant and highly reproducible RT-qPCR assay, allowed partially decoupling of the transcriptomic processes of attachment and metamorphosis. The bacterial TBP-containing extract provided a unique opportunity to monitor the regulation of genes exclusively involved in the process of metamorphosis, contrasting previous gene expression studies that utilized cues, such as crustose coralline algae, biofilms or with GLW-amide neuropeptides that stimulate the entire onset of larval metamorphosis and attachment.


Assuntos
Antozoários/crescimento & desenvolvimento , Antozoários/genética , Metamorfose Biológica/efeitos dos fármacos , Pseudoalteromonas/química , Pirróis/farmacologia , Animais , Antozoários/efeitos dos fármacos , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Halogenação , Larva/efeitos dos fármacos , Larva/genética , Larva/crescimento & desenvolvimento , Pirróis/química , Pirróis/isolamento & purificação
12.
J Chem Ecol ; 38(5): 442-50, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22527059

RESUMO

The need for animals and plants to control microbial colonization is important in the marine environment with its high densities of microscopic propagules and seawater that provides an ideal medium for their dispersal. In contrast to the traditional emphasis on antagonistic interactions of marine organisms with microbes, emerging studies lend support to the notion that health and performance of many marine organisms are functionally regulated and assisted by associated microbes, an ecological concept defined as a holobiont. While antimicrobial activities of marine secondary metabolites have been studied in great depth ex-situ, we are beginning to understand how some of these compounds function in an ecological context to maintain the performance of marine holobionts. The present article reviews two decades of our research on the red seaweed Delisea pulchra by addressing: the defense chemistry of this seaweed; chemically-mediated interactions between the seaweed and its natural enemies; and the negative influence of elevated seawater temperature on these interactions. Our understanding of these defense compounds and the functional roles they play for D. pulchra extends from molecular interactions with bacterial cell signaling molecules, to ecosystem-scale consequences of chemically-controlled disease and herbivory. Delisea pulchra produces halogenated furanones that antagonize the same receptor as acylated homoserine lactones (AHL)-a group of widespread intercellular communication signals among bacteria. Halogenated furanones compete with and inhibit bacterial cell-to-cell communication, and thus interfere with important bacterial communication-regulated processes, such as biofilm formation. In a predictable pattern that occurs at the ecological level of entire populations, environmental stress interferes with the production of halogenated furanones, causing downstream processes that ultimately result in disease of the algal holobiont.


Assuntos
Ecossistema , Rodófitas/fisiologia , Fenômenos Fisiológicos Bacterianos , Furanos/metabolismo , Herbivoria , Rodófitas/metabolismo
13.
Ecology ; 93(12): 2736-45, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23431603

RESUMO

Invasion success of introduced species is often attributed to a lack of natural enemies as stated by the enemy release hypothesis (ERH). The ERH intuitively makes sense for specialized enemies, but it is less evident why invaders in their new area escape attacks by generalist enemies. A recent hypothesis explains low herbivore damage on invasive plants with plant defense chemicals that are evolutionarily novel to native herbivores. Support for this novel weapon hypothesis (NWH) is so far based on circumstantial evidence. To corroborate the NWH, there is a need for direct evidence through explicit characterizations of the novel chemicals and their effects on native consumers. This study evaluated the NWH using the highly invasive red alga Bonnemaisonia hamifera. In pairwise feeding experiments, preferences between B. hamifera and native competitors were assessed for four common generalist herbivores in the invaded area. Through a bioassay-guided fractionation, we identified the deterrent compound and verified its effect in an experiment with the synthesized compound at natural concentrations. The results showed that native herbivores strongly preferred native algae to B. hamifera. The resistance against herbivores could be tracked down to the algal metabolite 1,1,3,3-tetrabromo-2-heptanone, a compound not known from native algae in the invaded area. The importance of the chemical defense was further underlined by the feeding preference of herbivores for individuals with a depleted content of 1,1,3,3-tetrabromo-2-heptanone. This study thus provides the first conclusive example of a highly successful invader where low consumption in the new range can be directly attributed to a specific chemical defense against evolutionarily naive native generalists. In conclusion, our results support the notion that novel chemical weapons against naive herbivores can provide a mechanistic explanation for plant invasion success.


Assuntos
Herbivoria , Espécies Introduzidas , Invertebrados/fisiologia , Cetonas/toxicidade , Rodófitas/química , Rodófitas/metabolismo , Animais , Bioensaio , Evolução Biológica , Cetonas/química , Cetonas/metabolismo , Estrutura Molecular
14.
Appl Environ Microbiol ; 77(24): 8557-67, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22003011

RESUMO

The aims of this study were to determine if marine bacteria from Danish coastal waters produce antifouling compounds and if antifouling bacteria could be ascribed to specific niches or seasons. We further assess if antibacterial effect is a good proxy for antifouling activity. We isolated 110 bacteria with anti-Vibrio activity from different sample types and locations during a 1-year sampling from Danish coastal waters. The strains were identified as Pseudoalteromonas, Phaeobacter, and Vibrionaceae based on phenotypic tests and partial 16S rRNA gene sequence similarity. The numbers of bioactive bacteria were significantly higher in warmer than in colder months. While some species were isolated at all sampling locations, others were niche specific. We repeatedly isolated Phaeobacter gallaeciensis at surfaces from one site and Pseudoalteromonas tunicata at two others. Twenty-two strains, representing the major taxonomic groups, different seasons, and isolation strategies, were tested for antiadhesive effect against the marine biofilm-forming bacterium Pseudoalteromonas sp. strain S91 and zoospores of the green alga Ulva australis. The antiadhesive effects were assessed by quantifying the number of strain S91 or Ulva spores attaching to a preformed biofilm of each of the 22 strains. The strongest antifouling activity was found in Pseudoalteromonas strains. Biofilms of Pseudoalteromonas piscicida, Pseudoalteromonas tunicata, and Pseudoalteromonas ulvae prevented Pseudoalteromonas S91 from attaching to steel surfaces. P. piscicida killed S91 bacteria in the suspension cultures, whereas P. tunicata and P. ulvae did not; however, they did prevent adhesion by nonbactericidal mechanism(s). Seven Pseudoalteromonas species, including P. piscicida and P. tunicata, reduced the number of settling Ulva zoospores to less than 10% of the number settling on control surfaces. The antifouling alpP gene was detected only in P. tunicata strains (with purple and yellow pigmentation), so other compounds/mechanisms must be present in the other Pseudoalteromonas strains with antifouling activity.


Assuntos
Bactérias/isolamento & purificação , Microbiologia Ambiental , Interações Microbianas , Ulva/crescimento & desenvolvimento , Ulva/metabolismo , Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Técnicas de Tipagem Bacteriana , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Dinamarca , RNA Ribossômico 16S/genética , Análise de Sequência de DNA
15.
Mar Drugs ; 9(8): 1391-402, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21892353

RESUMO

Surface-associated marine bacteria often produce secondary metabolites with antagonistic activities. In this study, tropodithietic acid (TDA) was identified to be responsible for the antibacterial activity of the marine epiphytic bacterium Pseudovibrio sp. D323 and related strains. Phenol was also produced by these bacteria but was not directly related to the antibacterial activity. TDA was shown to effectively inhibit a range of marine bacteria from various phylogenetic groups. However TDA-producers themselves were resistant and are likely to possess resistance mechanism preventing autoinhibition. We propose that TDA in isolate D323 and related eukaryote-associated bacteria plays a role in defending the host organism against unwanted microbial colonisation and, possibly, bacterial pathogens.


Assuntos
Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Poríferos/microbiologia , Rhodobacteraceae/metabolismo , Animais , Filogenia , RNA Ribossômico 16S/genética , Rhodobacteraceae/química , Rhodobacteraceae/genética , Rhodobacteraceae/isolamento & purificação , Tropolona/análogos & derivados , Tropolona/isolamento & purificação , Tropolona/farmacologia
16.
Integr Comp Biol ; 51(5): 794-806, 2011 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21893590

RESUMO

The sensory capacity of bacteria and macroalgae (seaweeds) is limited with respect to many modalities (visual, auditory) common in "higher" organisms such as animals. Thus, we expect that other modalities, such as chemical signaling and sensing, would play particularly important roles in their sensory ecology. Here, we discuss two examples of chemical signaling in bacteria and seaweeds: (1) the role of chemical defenses and quorum-sensing (QS) regulatory systems in bacterial colonization and infection of the red alga Delisea pulchra and their ecological consequences, and (2) the regulation of dispersal and differentiation by nitric oxide (NO) in bacterial biofilms. Consistent with the goals of neuroecology, in both cases, we investigate the links between specific signal-mediated molecular mechanisms, and ecological outcomes, for populations or assemblages of bacteria or seaweeds. We conclude by suggesting that because of the fundamental role played by chemical signaling in bacteria, bacterial systems, either by themselves or in interactions with other organisms, have much to offer for understanding general issues in neuroecology. Thus, further integration of microbiology with the biology of eukaryotes would seem warranted and is likely to prove illuminating.


Assuntos
Bactérias/química , Biofilmes , Eucariotos/fisiologia , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Bactérias/patogenicidade , Fenômenos Fisiológicos Bacterianos , Reação de Fuga , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Variação Genética , Interações Hospedeiro-Patógeno , Biologia Marinha , Óxido Nítrico/química , Percepção de Quorum , Rodófitas/microbiologia , Rodófitas/fisiologia
17.
PLoS One ; 6(4): e19082, 2011 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-21559509

RESUMO

The induction of larval attachment and metamorphosis of benthic marine invertebrates is widely considered to rely on habitat specific cues. While microbial biofilms on marine hard substrates have received considerable attention as specific signals for a wide and phylogenetically diverse array of marine invertebrates, the presumed chemical settlement signals produced by the bacteria have to date not been characterized. Here we isolated and fully characterized the first chemical signal from bacteria that induced larval metamorphosis of acroporid coral larvae (Acropora millepora). The metamorphic cue was identified as tetrabromopyrrole (TBP) in four bacterial Pseudoalteromonas strains among a culture library of 225 isolates obtained from the crustose coralline algae Neogoniolithon fosliei and Hydrolithon onkodes. Coral planulae transformed into fully developed polyps within 6 h, but only a small proportion of these polyps attached to the substratum. The biofilm cell density of the four bacterial strains had no influence on the ratio of attached vs. non-attached polyps. Larval bioassays with ethanolic extracts of the bacterial isolates, as well as synthetic TBP resulted in consistent responses of coral planulae to various doses of TBP. The lowest bacterial density of one of the Pseudoalteromonas strains which induced metamorphosis was 7,000 cells mm(-2) in laboratory assays, which is on the order of 0.1-1% of the total numbers of bacteria typically found on such surfaces. These results, in which an actual cue from bacteria has been characterized for the first time, contribute significantly towards understanding the complex process of acroporid coral larval settlement mediated through epibiotic microbial biofilms on crustose coralline algae.


Assuntos
Antozoários/microbiologia , Antozoários/fisiologia , Larva/fisiologia , Metamorfose Biológica , Pseudoalteromonas/metabolismo , Pirróis/metabolismo , Animais , Bactérias/metabolismo , Biofilmes , Bioensaio/métodos , Técnicas Genéticas , Modelos Biológicos , Modelos Estatísticos , Filogenia , RNA Ribossômico 16S/metabolismo , Fatores de Tempo
18.
PLoS One ; 6(2): e16487, 2011 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-21379573

RESUMO

BACKGROUND: Attachment strength of fouling organisms on silicone coatings is low. We hypothesized that low attachment strength on silicones is, in part, due to the interaction of surface available components with natural glues. Components could alter curing of glues through bulk changes or specifically through altered enzyme activity. METHODOLOGY/PRINCIPAL FINDINGS: GC-MS analysis of silicone coatings showed surface-available siloxanes when the coatings were gently rubbed with a cotton swab for 15 seconds or given a 30 second rinse with methanol. Mixtures of compounds were found on 2 commercial and 8 model silicone coatings. The hypothesis that silicone components alter glue curing enzymes was tested with curing barnacle glue and with commercial enzymes. In our model, barnacle glue curing involves trypsin-like serine protease(s), which activate enzymes and structural proteins, and a transglutaminase which cross-links glue proteins. Transglutaminase activity was significantly altered upon exposure of curing glue from individual barnacles to silicone eluates. Activity of purified trypsin and, to a greater extent, transglutaminase was significantly altered by relevant concentrations of silicone polymer constituents. CONCLUSIONS/SIGNIFICANCE: Surface-associated silicone compounds can disrupt glue curing and alter enzyme properties. Altered curing of natural glues has potential in fouling management.


Assuntos
Adesivos/metabolismo , Enzimas/metabolismo , Compostos de Silício/efeitos adversos , Thoracica/enzimologia , Thoracica/metabolismo , Adesividade/efeitos dos fármacos , Adesivos/química , Animais , Cimentação , Ativação Enzimática/efeitos dos fármacos , Ensaios Enzimáticos , Enzimas/efeitos dos fármacos , Cromatografia Gasosa-Espectrometria de Massas , Fenômenos Mecânicos , Metanol/farmacologia , Modelos Biológicos , Modelos Teóricos , Compostos de Silício/química , Compostos de Silício/farmacologia , Propriedades de Superfície/efeitos dos fármacos , Thoracica/efeitos dos fármacos , Thoracica/fisiologia
19.
Environ Microbiol ; 13(3): 655-65, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21078035

RESUMO

Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7-16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae.


Assuntos
Bactérias/classificação , Alga Marinha/microbiologia , Bactérias/genética , Bactérias/isolamento & purificação , Biofilmes , Eletroforese em Gel de Gradiente Desnaturante , Meio Ambiente , Genes de RNAr , Especificidade de Hospedeiro , Estações do Ano , Ulva/microbiologia
20.
Biofouling ; 26(3): 247-55, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20054721

RESUMO

This study investigated whether surface-associated compounds isolated from the macroalga Fucus vesiculosus had the potential to mediate microbial and/or macrobial epibiosis similar to that on the natural alga. To selectively yield thallus-associated compounds and avoid contamination by intracellular algal compounds, cell lysis was monitored by surface microscopy of algal cells and chemical profiling of algal surface extracts by coupled gas chromatography mass spectroscopy. The optimized extraction resulted in polar and non-polar algal surface extracts. The non-polar surface extract was immobilized in hydrogel, the polar surface extract was homogeneously perfused through the gel to ensure a temporally constant delivery of polar extract components. During a 7 day field trial, bacterial biofilms were formed on control gels and gels featuring polar and/or non-polar extract components. PERMANOVA revealed that bacterial community profiles on controls and on gels featuring polar or non-polar extract were significantly different from the profile on F. vesiculosus, while the profile on the gels bearing both polar and non-polar extracts was not. Moreover, the polar surface extracts inhibited the settlement of barnacle cyprids. Considering the pronounced effects of bacterial biofilms on invertebrate larval settlement, these results suggest that algal surface chemistry affects macrofouling not only directly but also indirectly, via its control of biofilm formation and composition.


Assuntos
Bactérias/crescimento & desenvolvimento , Biofilmes/crescimento & desenvolvimento , Fucus/química , Fucus/microbiologia , Bactérias/genética , Ecossistema , Fucus/classificação , Fucus/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Propriedades de Superfície
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