SEM pictures of microorganisms associated with the <i>Ectopleura crocea</i> epidermis.

<p>A) Surface of a tentacle densely covered with the two morphotypes of microorganisms living on the epidermis: one is horseshoe-shaped (green; named <i>Type I</i>) and the other is fusiform, worm-like (red; named <i>Type II</i>). B) Portion of a broken tentacle, bacteria were present on the surface (s) but not inside (is). C–D) Enlargements of tentacle portions which were densely covered by the two microorganisms. E) Particular of the horseshoe-shaped <i>Type I</i>, showing the peculiar arrangement in the tentacle grooves. F) Particular of a cluster of the worm-like <i>Type II</i>. Scale bars: A, C, E, F 5 μm; B 2 μm; D 10 μm.</p

Most abundant bacterial genera associated with <i>E. crocea</i> in April 2009 (A) and March 2010 (B), as revealed by tag-encoded amplicon pyrosequencing of the 16S rDNA gene.

<p>Reported are the 20 most abundant genera.</p

Main characteristics of <i>Ectopleura crocea</i>.

<p>A) Underwater photograph of the hydroid. B) Scheme of the colony. 1. Feeding and reproductive polyps; 2. Stems (hydrocauli); 3. Tangled stolons anchoring the colony to the substrate (hydrorhizae).</p

TEM pictures of <i>Type II</i> bacteria associated with <i>Ectopleura crocea.</i>

<p>A) Numerous bacteria in transversal sections (arrows) observed on the hydroid ectoderm (ec). B) Bacteria (longitudinal and tranversal sections) present in a groove of the hydroid ectoderm. C) Bacteria lying on the hydroid periderm (p) are often found in correspondence to the microvilles (mv) of the ectodermal cells. D) Close-up view showing the glycocalyx (gl) surrounded the microorganisms. e–f. Longitudinal section of a bacterium. Scale bars: a, c, e 1 μm; b 2 μm; d, f 0.5 μm.</p

Portions of <i>E. crocea</i> examined to find prokaryotes.

<p>A) Scheme illustrating the main features of the polyp stage. GC gastric column, AT aboral tentacles, OT oral tentacles, G gonophores, B basal portion of hydranth, N neck zone, H hydrocaulus (portion covered with perisarc). B–E. Close-up view at scanning electron microscope. B). Aboral tentacle colonized by bacteria. C. Broken female gonophore containing immature actinulae round in shape (a). Bacteria were rarely found on actinulae at this stage. D. Mature female gonophore with actinula's tentacles protruding through the opening (white arrow). Bacteria were often observed on these tiny tentacles. E. Released and free-living actinula with developed aboral (at) and oral (ot) tentacles. Scale bars: B 20 μm; C 500 μm D, E 200 μm.</p

Resistance genes detected before and after sediment incubation in antibiotic-supplemented BHI broth.

*<p>detected both in sediment and in broth.</p

Primer pairs used to detect resistance genes in PCR assays.

<p>Primer pairs used to detect resistance genes in PCR assays.</p

Control strains used in PCR assays.

a<p>American Type Culture Collection.</p

Abundance of benthic enterococci.

<p>Enterococcal abundance in the farm sediments and at the control site was determined by qPCR before and after incubation with antibiotic-supplemented BHI broth. A, St. 1; B, St. 2 and C, St. 3. *Not detectable i.e.</p

Location of the fish farm and of the sampling stations.

<p>The map is from <a href="http://earthobservatory.nasa.gov/" target="_blank">http://earthobservatory.nasa.gov/</a>, image courtesy Jesse Allen.</p