Bacterial Epibiosis Research Articles

Prompt induction of chemical defenses in the red seaweed Laurencia dendroidea: The role of herbivory and epibiosis

Induced chemical defense is still - uncertain process in seaweed, especially in tropical areas. Attention has been given to changes on phlorotannin contents due herbivore pressure, while knowledge considering - other secondary metabolites or other environmental factors as inducers is limited. We used laboratory experiments to assess induced chemical defense in the tropical red seaweed Laurencia dendroidea in response to simulated herbivory, presence of epibionts (microalga and bacterium), and bacterial infestation, addressing the following questions: 1) does inducible chemical defense by simulated herbivory, as well as microalgal and bacterial epibiosis, occur?; 2) are chemical defenses induced by bacterial infestation after simulated herbivory?; 3) is there a trade-off between inducible defense and seaweed growth?; and 4) how do variations in chemical defense affect seaweed susceptibility to specialist and generalist consumers? Inducible defense was measured as changes in sesquiterpene elatol levels, and growth was taken to infer whether induced chemical defense incurred metabolic costs. Specimens of L. dendroidea under simulated herbivory produced higher concentrations of elatol up to 2 days after treatment, followed by relaxation after 7 days, while epibiosis (by microalga and bacterium) and bacterial infestation did not induce a defense response. Simulated herbivory resulted in reduced L. dendroidea growth, reinforcing that induced chemical defense is a cost-saving strategy as stated by the Optimal Defense Theory (ODT), -in addition there was a tendency of epibiosis for biomass decreasing. The defensive effect varied according to elatol concentration and consumer identity, since aplysiids tolerated 10-fold natural concentrations (NC) whereas sea urchins were inhibited by NC. Our results highlight that inducible chemical defenses may also be a more rapid process than previously evidenced in seaweeds. Higher levels of elatol promoted decreased consumption, demonstrating that seaweed susceptibility is dose-dependent and induction is an important ecological strategy depending on environmental conditions.

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.

Species- and site-specific bacterial communities associated with four encrusting bryozoans from the North Sea, Germany

Epi- and endozoic bacterial communities associated with four bryozoan species from the Jade (North Sea, Germany) were investigated by the combined application of molecular tools and electron microscopic visualisation of zooids. Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments of associated bacteria displayed specific bacterial community profiles in the examined species Aspidelectra melolontha, Conopeum reticulum, Electra monostachys and Electra pilosa. Actual bacterial epibiosis was only observed on C. reticulum whilst the other bryozoans under investigation were largely free of microbial epibionts. These observations indicated that bryozoan-associated bacteria identified by molecular methods originated from internal cavities of bryozoan zooids. Cluster analysis of DGGE band patterns revealed species-specific bacterial communities in A. melolontha, E. monostachys and E. pilosa. Bacteria associated with C. reticulum were seemingly influenced by site-specific parameters. A comparison of bacterial community profiles between reference and invertebrate surfaces allowed for an interpretation of conspicuous group-specific differences. Operational taxonomic units (OTUs) obtained from a single set of bryozoan replicates that were absent on the inorganic reference samples (mussel shells) were hypothesized to be favourable endobionts. Contrary, OTUs present in the references but absent in bryozoan samples could be assumed to stem from bryozoan-specific defenses against ubiquitous bacterial colonizers. Although there was no experimental evidence for a mutual relationship between prokaryotes and their eukaryotic bryozoan hosts, this study demonstrated that in three out of four bryozoans under investigation associated bacterial communities were characteristically shaped by host attributes.

Effects of Caribbean sponge secondary metabolites on bacterial surface colonization

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 40:191-203 (2005) - doi:10.3354/ame040191 Effects of Caribbean sponge secondary metabolites on bacterial surface colonization Sarah R. Kelly1, Eliane Garo2, Paul R. Jensen2, William Fenical2, Joseph R. Pawlik1,* 1Department of Biology and Marine Biology, Center for Marine Science, University of North Carolina at Wilmington, Wilmington, North Carolina 28403, USA2Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego,La Jolla, California 92093, USA *Corresponding author. Email: pawlikj@uncw.edu ABSTRACT: Crude organic tissue extracts from 8 species of Caribbean sponges were assayed for inhibitory effects on surface colonization using 24 environmental marine bacterial isolates, 4 known marine invertebrate pathogens, and 1 common fouling bacterium. Each extract was tested for its effects on bacterial attachment, growth and swarming. The 24 bacterial strains were isolated from sponge surfaces, nearby substrata, or adjacent seawater. Extracts were incorporated into agar for assays of bacterial attachment and swarming. Growth-inhibition assays were conducted with the standard agar disk-diffusion assay. Of the 24 bacterial isolates, 23 were significantly inhibited from attaching to an extract-treated agar surface; 1 isolate from the surface of Agelas conifera exhibited significantly enhanced attachment on agar treated with the extract of that sponge. Sponge extracts had the least effect on growth: of 184 assays, 11 displayed significant antibacterial activity, all of these from 4 sponge species (A. conifera, Ailochroia crassa, Amphimedon compressa, and Aplysina fulva). The same isolate from the surface of A. conifera that exhibited enhanced attachment in response to the extract of that sponge exhibited inhibited growth in response to the same extract. Six out of 24 bacterial isolates exhibited swarming, the majority (67%) of which were isolated from substratum sources. Extracts from 4 of the 8 sponge species (the same species as listed above) inhibited swarming in all 6 strains, while the remaining extracts enhanced, inhibited, or had no effect on swarming depending on the strain. Bioassay-guided fractionation of the extract of A. crassa yielded 2 compounds responsible for inhibiting attachment and swarming, respectively. Ianthellin was identified as the metabolite that inhibited attachment, whereas another brominated tryosine metabolite inhibited swarming. Chemical defenses of sponges may target microbial attachment, and to a lesser degree influence swarming and growth. Non-toxic metabolites may play the greatest role in affecting bacterial epibiosis on the surfaces of marine sponges. KEY WORDS: Bacterial attachment · Bacterial swarming · Bromotyrosine metabolites · Microbial chemical defense · Quorum sensing · Antibacterial Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 40, No. 2. Online publication date: September 06, 2005 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2005 Inter-Research.

Potential control of bacterial epibiosis on the surface of the sponge Mycale adhaerens

Terminal restriction fragment length polymorphism (T-RFLP) analysis revealed struc- tural differences in bacterial communities colonizing the surface of the sponge Mycale adhaerens or an inanimate reference surface. Since these surfaces are exposed to a common pool of indigenous bacterial colonizers in the water column, the differences in bacterial community structure were attributed to differences in chemical and/or physical characteristics between sponge and reference surfaces. In order to investigate a potential chemical interaction between sponge and bacterial com- munities, the effect of organic extracts from both the sponge and 20 bacterial isolates from the sponge surface was tested at tissue-level concentration on 36 bacterial isolates from the reference surface. Half of these isolates were susceptible to extract from sponge tissue and 61% to those of the isolates from the sponge surface; 30% were sensitive to extracts from both sponge and isolates. In contrast, only 1 of the isolates from the sponge surface was slightly inhibited by the sponge extract (5%) and none by the extracts from the epibiotic isolates, supporting speculations on potential endo- and exogenous chemical control of bacterial epibiosis by the sponge and epibiotic bacteria, respectively.

Distribution of bacteria and associated minerals in the gill chamber of the vent shrimp Rimicaris exoculata and related biogeochemical processes

The shrimp Rimicaris exoculata dominates the megafauna of some Mid-Atlantic Ridge hydrothermal vent fields. This species harbours a rich bacterial epibiosis inside its gill chamber. At the 'Rainbow' vent site (36° 14.0' N), the epibionts are associated with iron oxide deposits. Investiga- tion of both bacteria and minerals by scanning electron microscopy (SEM) and X-ray microanalysis (EDX) revealed 3 distinct compartments in the gill chamber: (1) the lower pre-branchial chamber, housing bacteria but devoid of minerals; (2) the 'true' branchial chamber, containing the gills and devoid of both bacteria and minerals; and (3) the upper pre-branchial chamber, housing the main ectosymbiotic bacterial community and associated mineral deposits. Our chemical and temperature data indicated that abiotic iron oxidation appears to be kinetically inhibited in the environment of the shrimps, which would explain the lack of iron oxide deposits in the first 2 compartments. We propose that iron oxidation is microbially promoted in the third area. The discrepancy between the spatial dis- tribution of bacteria and minerals suggests that different bacterial metabolisms are involved in the first and third compartments. A possible explanation lies in the modification of physico-chemical con- ditions downstream of the gills that would reduce the oxygen content and favours the development of bacterial iron-oxidizers in this Fe II -rich environment. A potential role of such iron-oxidizing symbionts in the shrimp diet is suggested. This would be unusual for hydrothermal ecosystems, in which most previously described symbioses rely on sulphide or methane as an energy source.

Culturable epibacteria of the marine sponge Ircinia fusca: temporal variations and their possible role in the epibacterial defense of the host

The influence of environmental changes on the epibacterial population of the marine sponge Ircinia fusca (Carter) was evaluated by using a bacterial culture-based approach. Sponge surface-associated bacteria were isolated, enumerated and cultured during 5 different collection periods. These bacteria were assessed for antibacterial activity against fouling bacteria and for auto-inhibition with their extracts, using the ecologically relevant agar plug method. Morphological studies of all culturable sponge-associated bacteria were carried out and the isolates with antibacterial potential were further identified using 16S rRNA gene sequences. It was found that the epibacterial population of the sponge is influenced by temporal changes in the environment. However, the bacterial strain belonging to the genus Bacillus, which displayed antibacterial activity against fouling bacteria, was found to be associated with the sponge in every collection period, indicating close association of this strain with the sponge I. fusca. The sponge seems to have selective control of the bacterial epibiosis on its surface. The antibacterial assay of sponge extract against its associated bacteria showed that the sponge promotes the growth of certain antibiotic producing strains of the genus Bacillus, which may indirectly help the sponge in governing epibacterial populations on its surface by deterring settlement of other microbes from the vicinity. In summary, this investigation explores the possible role of sponge surface-associated bacteria in the epibacterial defense of the host, by considering the temporal variations in the habitat.

A bacterial culture-independent method to investigate chemically mediated control of bacterial epibiosis in marine invertebrates by using TRFLP analysis and natural bacterial populations

It has been postulated that a variety of physically undefended marine invertebrates have evolved strategies to control microbial epibiosis chemically. Ecologically meaningful experiments that demonstrate chemically mediated antibacterial effects are difficult due to the small number of cultivable bacteria. Based on the example of three sponges, this study introduces a culture-independent methodology to investigate chemically mediated control of bacterial epibiosis by analyzing the natural bacterial consortia. Organic extracts of sponges were immobilized in hydrogels at tissue level concentrations and exposed to the same source of natural seawater for bacterial colonization. Terminal restriction fragment length polymorphism analysis of polymerase chain reaction-amplified bacterial community DNA obtained from these gels was shown to be a useful tool to study bacterial community shifts in response to sponge metabolites by comparing bacterial ribotypes obtained from the gel surfaces. Several terminal restriction fragments were absent relative to the control suggesting that settlement of specific bacteria was prevented. On the other hand, additional fragments occurred in some treatments, coinciding with higher bacterial abundance evidenced by DAPI counts of bacterial cells, indicating the bacterial utilization of sponge extract components. The advantages of this method are (1) a culture-independent approach, i.e. the assessment of antimicrobial activities against natural bacterial communities, (2) no restriction to particular modes of microbial colonization, i.e. antibiotic and repellant, and (3) the in situ assessment of antimicrobial compounds under flow conditions.

A distinctive epibiotic bacterial community on the soft coral Dendronephthya sp. and antibacterial activity of coral tissue extracts suggest a chemical mechanism against bacterial epibiosis

Abstract Different bacterial community profiles were observed on the soft coral Dendronephthya sp. and an inanimate reference site using terminal restriction fragment length polymorphism analysis of bacterial community DNA. To correlate the observation with a chemical defense mechanism against bacterial epibiosis, antibacterial effects of coral tissue extracts and waterborne products of coral-associated bacterial isolates (11 morphotypes) were tested against indigenous benthic bacterial isolates (33 morphotypes) obtained in the vicinity of the coral colonies. The coral tissue extracts and waterborne products of coral-associated bacteria inhibited growth and attachment of indigenous bacterial isolates, suggesting an endogenous chemical and an exogenous biological mechanism against bacterial epibiosis in this soft coral.

Chemical Control of Bacterial Epibiosis and Larval Settlement of Hydroides elegans in the Red Sponge Mycale adherens

The sponge, Mycale adherens , usually occurs within the fouling community of Hong Kong waters, yet its body surface is rarely fouled by other macroorganisms. In this study, sponge-associated bacteria were isolated using enrichment culture techniques and compared with indigenous bacterial isolates from an inanimate reference site in the close vicinity. Bacterial isolates were identified phylogenetically by 16S rRNA gene sequence analysis. The comparison between culturable bacterial communities from the sponge and indigenous benthic bacteria revealed differences both in the total number of isolates and their phylogenetic affiliation. Laboratory bioassays utilizing monospecies bacterial films revealed that a significant portion of sponge-associated bacteria had either an inhibitory or neutral effect on larval settlement of the fouling polychaete, Hydroides elegans . In contrast to natural biofilms, which harbor ca 65% of bacteria with at least some sort of inductive effect on H. elegans , statistical analysis showed that only 25% of sponge-associated bacteria were classified as "inductive" strains while the remaining 75% were classified as "non-inductive" strains. Waterborne metabolites of sponges affected the larvae of H. elegans in a concentration-dependent manner by either exerting a toxic or an anti-settlement effect. Organic solvent extracts of sponge tissue weakly inhibited growth of bacterial strains isolated from marine biofilms. A potential antifouling mechanism in the sponge M. adherens is discussed.

A distinctive epibiotic bacterial community on the soft coral Dendronephthya sp. and antibacterial activity of coral tissue extracts suggest a chemical mechanism against bacterial epibiosis

Different bacterial community profiles were observed on the soft coral Dendronephthya sp. and an inanimate reference site using terminal restriction fragment length polymorphism analysis of bacterial community DNA. To correlate the observation with a chemical defense mechanism against bacterial epibiosis, antibacterial effects of coral tissue extracts and waterborne products of coral-associated bacterial isolates (11 morphotypes) were tested against indigenous benthic bacterial isolates (33 morphotypes) obtained in the vicinity of the coral colonies. The coral tissue extracts and waterborne products of coral-associated bacteria inhibited growth and attachment of indigenous bacterial isolates, suggesting an endogenous chemical and an exogenous biological mechanism against bacterial epibiosis in this soft coral.

Bacterial epibiosis on Bahamian and Pacific ascidians

Interactions between epibiotic bacteria and organisms possibly play a central role in marine ecology. Despite its potential significance, this field has long time been neglected. For most aquatic taxa nothing is known about presence/absence of bacteria on their surface, much less about specific associations or potential interactions between epibiotically associated micro- and macroorganisms. Bahamian and Pacific ascidians, most of them colonial, were screened for the presence, abundance and diversity of epibiotic bacteria and macroepibionts. Only one species, Polyclinum planum, occasionally carried macroepibionts. All ascidian species exhibited varying densities of epibiotic bacteria on their surfaces. Average epibacterial abundance as assessed by plate counts on the 29 species ranged from 60 to 1.2 × 10 7/cm 2. Significant differences in bacterial abundances were observed between species, families and geographical regions. On the family level, Polyclinidae were the most densely colonized. Bahamian species exhibited less dense epibacterial communities than Pacific species, a difference that may partly be caused by the absence of the heavily fouled Polyclinidae from the Bahamian collection. Diversity of culturable strains, evaluated for the Bahamian species only, was uniformly high on most species. I did not find any evidence for specific associations (as reflected by dominance of single strains) between culturable bacteria and ascidian species. Contrarily, direct observation by epifluorescence revealed the presence of an apparently dominant photosynthetic symbiont on several didemnid species. The presence of this symbiont correlated negatively with abundance and diversity of culturable epibionts. This negative correlation could reflect properties of the host's surface which selectively favor proliferation of the symbiont or antagonistic interactions between the symbionts and other potential bacterial colonizers.

Chemical control of bacterial epibiosis on ascidians

Two co-occurring ascidians of the Pacific subtidal, Polyclinum planum and Cystodytes lobatus, were found to exhibit remarkably different numbers of surface bacteria. On average, epibacterial densities on P. planum were 140 times greater than those on C lobatus as measured by plate-counting methods. Organic extracts of both ascidian species were tested for antimicrobial activities and effects on bacterial settlement. Bacterial settlement was measured using a new bioassay described in this paper. The results of the settlement bioassay clearly demonstrate that extracts of the little-colonized C. lobatus deter bacterial settlement while extracts of the heavily colonized P. planum induce settlement relative to the control. In addition to reducing bacterial settlement, extracts of C. lobatus colonies exhibited varying, but generally low, levels of antiraicrobial activity against, on average, one-half of the 36 strains of marine bacteria tested. On an interspecific level, including 11 ascidian species screened in a pilot study, fouling-deterring activities were correlated with epibacterial abundances while antimicrobial activity was not. It is concluded that the chemical control of bacterial settlement, possibly complemented by antimicrobial toxicity, provides an accurate model to explain the dramatically different bacterial abundance on the surfaces of the ascidian species studied. This investigation presents evidence that non-toxic metabolites influence bacterial settlement and, in this way, may function to regulate bacterial epibiosis on the surfaces of some marine invertebrates.