Article

Low Densities of Epiphytic Bacteria from the Marine Alga Ulva australis Inhibit Settlement of Fouling Organisms

School of Biotechnology and Biomolecular Sciences and Centre for Marine Bio-innovation, Biological Sciences Building, University of New South Wales, Sydney, NSW 2052, Australia.
Applied and Environmental Microbiology (Impact Factor: 3.67). 01/2008; 73(24):7844-52. DOI: 10.1128/AEM.01543-07
Source: PubMed

ABSTRACT

Bacteria that produce inhibitory compounds on the surface of marine algae are thought to contribute to the defense of the
host plant against colonization of fouling organisms. However, the number of bacterial cells necessary to defend against fouling
on the plant surface is not known. Pseudoalteromonas tunicata and Phaeobacter sp. strain 2.10 (formerly Roseobacter gallaeciensis) are marine bacteria often found in association with the alga Ulva australis and produce a range of extracellular inhibitory compounds against common fouling organisms. P. tunicata and Phaeobacter sp. strain 2.10 biofilms with cell densities ranging from 102 to 108 cells cm−2 were established on polystyrene petri dishes. Attachment and settlement assays were performed with marine fungi (uncharacterized
isolates from U. australis), marine bacteria (Pseudoalteromonas gracilis, Alteromonas sp., and Cellulophaga fucicola), invertebrate larvae (Bugula neritina), and algal spores (Polysiphonia sp.) and gametes (U. australis). Remarkably low cell densities (102 to 103 cells cm−2) of P. tunicata were effective in preventing settlement of algal spores and marine fungi in petri dishes. P. tunicata also prevented settlement of invertebrate larvae at densities of 104 to 105 cells cm−2. Similarly, low cell densities (103 to 104cells cm−2) of Phaeobacter sp. strain 2.10 had antilarval and antibacterial activity. Previously, it has been shown that abundance of P. tunicata on marine eukaryotic hosts is low (<1 × 103 cells cm−2) (T. L. Skovhus et al., Appl. Environ. Microbiol. 70:2373-2382, 2004). Despite such low numbers of P. tunicata on U. australis in situ, our data suggest that P. tunicata and Phaeobacter sp. strain 2.10 are present in sufficient quantities on the plant to inhibit fouling organisms. This strongly supports the
hypothesis that P. tunicata and Phaeobacter sp. strain 2.10 can play a role in defense against fouling on U. australis at cell densities that commonly occur in situ.

Full-text

Available from: Rebecca J Case
    • "Microalgae are present in any aquaculture facility, either introduced on purpose, or as incidental colonizers of tank walls and water, and TDA-producing Phaeobacter strains may be commensals of these algae [66]. TDA-producing Phaeobacter are excellent biofilm formers [9] and may inhibit settlement of other organisms or even replace an already established biofilm [61,60]. The Phaeobacter isolates from the Greek aquaculture units produced TDA and were thus similar to isolates of P. inhibens, P. gallaeciensis and R. mobilis [8,32,55]. "
    [Show abstract] [Hide abstract] ABSTRACT: Fish-pathogenic Vibrio can cause large-scale crashes in marine larval rearing units and, since the use of antibiotics can result in bacterial antibiotic resistance, new strategies for disease prevention are needed. Roseobacter-clade bacteria from turbot larval rearing facilities can antagonize Vibrio anguillarum and reduce mortality in V. anguillarum-infected cod and turbot larvae. In this study, it was demonstrated that antagonistic Roseobacter-clade bacteria could be isolated from sea bass larval rearing units. In addition, it was shown that they not only antagonized V. anguillarum but also V. harveyi, which is the major bacterial pathogen in crustaceans and Mediterranean sea bass larvae cultures. Concomitantly, they significantly improved survival of V. harveyi-infected brine shrimp. 16S rRNA gene sequence homology identified the antagonists as Phaeobacter sp., and in silico DNA-DNA hybridization indicated that they could belong to a new species. The genomes contained genes involved in synthesis of the antibacterial compound tropodithietic acid (TDA), and its production was confirmed by UHPLC-TOFMS. The new Phaeobacter colonized live feed (Artemia) cultures and reduced Vibrio counts significantly, since they reached only 104 CFU mL−1, as opposed to 108 CFU mL−1 in non-Phaeobacter treated controls. Survival of V. anguillarum-challenged Artemia nauplii was enhanced by the presence of wild type Phaeobacter compared to challenged control cultures (89% ± 1.0 vs 8% ± 3.2). In conclusion, TDA-producing Phaeobacter isolated from Mediterranean marine larviculture are promising probiotic bacteria against pathogenic Vibrio in crustacean live-feed cultures for marine fish larvae.
    No preview · Article · Feb 2016 · Systematic and Applied Microbiology
  • Source
    • "Many of the characterized Roseobacter isolates can be described as free-living, having been isolated from seawater or inert marine surfaces. However, some roseobacters also associate with other organisms, including oysters (Ruiz-Ponte et al., 1998), sponges (Zan et al., 2014), algae (Rao et al., 2007; Case et al., 2011), and cephalopods (Grigioni et al., 2000; Pichon et al., 2005; Collins et al., 2012). Among many squid and cuttlefish, roseobacters have been found associated with the accessory nidamental gland (ANG), part of the female reproductive system and comprised of many epithelium-lined tubules that house dense populations of bacterial symbionts (Figure 1, Bloodgood, 1977; Collins et al., 2012). "
    [Show abstract] [Hide abstract] ABSTRACT: The accessory nidamental gland (ANG) of the female Hawaiian bobtail squid, Euprymna scolopes, houses a consortium of bacteria including members of the Flavobacteriales, Rhizobiales, and Verrucomicrobia but is dominated by members of the Roseobacter clade (Rhodobacterales) within the Alphaproteobacteria. These bacteria are deposited into the jelly coat of the squid's eggs, however, the function of the ANG and its bacterial symbionts has yet to be elucidated. In order to gain insight into this consortium and its potential role in host reproduction, we cultured 12 Rhodobacterales isolates from ANGs of sexually mature female squid and sequenced their genomes with Illumina sequencing technology. For taxonomic analyses, the ribosomal proteins of 79 genomes representing both roseobacters and non-roseobacters along with a separate MLSA analysis of 33 housekeeping genes from Roseobacter organisms placed all 12 isolates from the ANG within two groups of a single Roseobacter clade. Average nucelotide identity analysis suggests the ANG isolates represent three genera (Leisingera, Ruegeria, and Tateyamaria) comprised of seven putative species groups. All but one of the isolates contains a predicted Type VI secretion system, which has been shown to be important in secreting signaling and/or effector molecules in host-microbe associations and in bacteria-bacteria interactions. All sequenced genomes also show potential for secondary metabolite production, and are predicted to be involved with the production of acyl homoserine lactones (AHLs) and/or siderophores. An AHL bioassay confirmed AHL production in three tested isolates and from whole ANG homogenates. The dominant symbiont, Leisingera sp. ANG1, showed greater viability in iron-limiting conditions compared to other roseobacters, possibly due to higher levels of siderophore production. Future comparisons will try to elucidate novel metabolic pathways of the ANG symbionts to understand their putative role in host development.
    Full-text · Article · Feb 2015 · Frontiers in Microbiology
  • Source
    • "Epiphytic Vibrio species present on green alga Ulva reticulata significantly inhibited settlement and metamorphosis of polychaete larvae and may attribute to the host alga protection against further fouling (Dobretsov and Qian 2002). Similarly, epiphytic Pseudoalteromonas tunicata and Roseobacter gallaeciensis are found in association with green alga U. australis and produce a range of extracellular inhibitory compounds against marine fungi, bacteria, invertebrate larvae, and algal spores (Holmström et al. 2002; Rao et al. 2007). In contrast, three epiphytic strains of Pseudoalteromonas sp. "
    [Show abstract] [Hide abstract] ABSTRACT: In recent decade, seaweeds-associated microbial communities have been significantly evaluated for functional and chemical analyses. Such analyses let to conclude that seaweeds-associated microbial communities are highly diverse and rich sources of bioactive compounds of exceptional molecular structure. Extracting bioactive compounds from seaweed-associated microbial communities have been recently increased due to their broad-spectrum antimicrobial activities including antibacterial, antifungal, antiviral, anti-settlement, antiprotozoan, antiparasitic, and antitumor. These allelochemicals not only provide protection to host from other surrounding pelagic microorganisms, but also ensure their association with the host. Antimicrobial compounds from marine sources are promising and priority targets of biotechnological and pharmaceutical applications. This review describes the bioactive metabolites reported from seaweed-associated bacterial and fungal communities and illustrates their bioactivities. Biotechnological application of metagenomic approach for identifying novel bioactive metabolites is also dealt, in view of their future development as a strong tool to discover novel drug targets from seaweed-associated microbial communities.
    Full-text · Article · Dec 2014 · Applied Microbiology and Biotechnology
Show more