Epibiotic Vibrio luminous bacteria isolated from some hydrozoa and bryozoa species

Massilia arvi sp. nov., isolated from fallow-land soil previously cultivated with Brassica oleracea, and emended description of the genus Massilia

A novel bacterial strain, designated THG-RS2OT, was isolated from fallow-land soil previously cultivated with Brassica oleracea in Yongin, South Korea. Cells were Gram-stain-negative, aerobic, non-motile rods, catalase- and oxidase-positive. Strain THG-RS2OT grew optimally at 25–37 °C, at pH 7.0 and in the absence of NaCl. 16S rRNA gene sequence analysis demonstrated that strain THG-RS2OT shows highest sequence similarity with Massilia kyonggiensis KACC 17471T followed by Massilia aerilata KACC 12505T, Massilia niastensis KACC 12599T, Massilia tieshanensis KACC 14940T and Massilia haematophila KCTC 32001T. Levels of DNA–DNA relatedness between strain THG-RS2OT and the closest phylogenetic neighbours were below 55.0 % and the DNA G+C content of strain THG-RS2OT was 63.2 mol%. Major fatty acids were C16 : 0, cyclo-C17 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). The major respiratory quinone was identified as ubiquonone-8 and predominant polar lipids were determined to be diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Characterization by 16S rRNA gene sequence analysis, DNA–DNA hybridization, ubiquinone, polar lipid, fatty acid composition, and physiological and biochemical parameters revealed that strain THG-RS2OT represents a novel species of the genus Massilia. Hence, the present study describes a novel species for which the name Massilia arvi sp. nov. is proposed. The type strain is THG-RS2OT ( = KCTC 42609T = CCTCC AB 2015115T).

Pedobacter humi sp. nov., isolated from a playground soil

A Gram-stain-negative, aerobic, non-motile, rod-shaped and yellow-pigmented bacterium, designated strain THG S15-2T, was isolated from playground soil in Sindorim-dong, Guro-gu, Seoul, South Korea. According to 16S rRNA gene sequence comparisons, strain THG S15-2T was found to be related most closely to Pedobacter ginsengisoli Gsoil 104T (97.5 % similarity), Pedobacter panaciterrae Gsoil 042T (97.4 %), Pedobacter seoulensis THG-G12T (97.1 %) and Pedobacter caeni LMG 22862T (97.1 %). The level of DNA-DNA relatedness between strain THG S15-2T and its phylogenetically closest neighbours was below 30.0 %. The only isoprenoid quinone detected in strain THG S15-2T was menaquinone-7. The DNA G+C content was 45.9 mol%. The major polar lipid was phosphatidylethanolamine. The major component in the polyamine pattern was sym-homospermidine. The major fatty acids were identified as summed feature 3 (C16:1ω7c and/or C16:1ω6c), iso-C15:0 and C16:0. These data supported the affiliation of strain THG S15-2T to the genus Pedobacter. Strain THG S15-2T was distinguished from related Pedobacter species by physiological and biochemical tests. Therefore, strain THG S15-2T represents a novel species, for which the name Pedobacter humi sp. nov. is proposed. The type strain is THG S15-2T (= KCTC 42735T = CCTCC AB 2015293T).

The Mediterranean non-indigenous ascidian Polyandrocarpa zorritensis: Microbiological accumulation capability and environmental implications

We investigated the bacterial accumulation and digestion capability of Polyandrocarpa zorritensis, a non-indigenous colonial ascidian originally described in Peru and later found in the Mediterranean. Microbiological analyses were carried out on homogenates from "unstarved" and "starved" ascidians and seawater from the same sampling site (Adriatic Sea, Italy). Culturable heterotrophic bacteria (22 °C), total culturable bacteria (37 °C) and vibrios abundances were determined on Marine Agar 2216, Plate Count Agar and TCBS Agar, respectively. Microbial pollution indicators were measured by the most probable number method. All the examined microbiological groups were accumulated by ascidians but differently digested. An interesting outcome is the capability of P. zorritensis to digest allochthonous microorganisms such as coliforms as well as culturable bacteria at 37 °C, counteracting the effects of microbial pollution. Thus, the potential exploitation of these filter feeders to restore polluted seawater should be taken into consideration in the management of this alien species.

Undibacterium aquatile sp. nov., isolated from a waterfall

A Gram-stain-negative, aerobic, motile and rod-shaped strain, THG-DN7.3T, was isolated from a waterfall. Strain THG-DN7.3T grew well at 18–28 °C and at pH 6.0–7.5 on Reasoner's 2A agar. Based on 16S rRNA gene sequence comparisons, strain THG-DN7.3T was most closely related to Undibacterium jejuense JS4-4T (97.3 % 16S rRNA gene sequence similarity) and Undibacterium seohonense SHS5-24T (96.5 %). The G+C content of the genomic DNA was 57.4 mol%. The mean DNA–DNA relatedness of strain THG-DN7.3T with U. jejuense KACC 12607T was 40 ± 1 % (reciprocal 50 ± 2.1 %). The major cellular fatty acids of strain THG-DN7.3T were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) (47.4 %), C16 : 0 (30.4 %), summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c) (6.8 %) and C12 : 0 (6.2 %). The predominant isoprenoid quinone was ubiquinone-8. The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The results of the DNA–DNA hybridization and genotypic analysis, in combination with chemotaxonomic and physiological data, demonstrated that strain THG-DN7.3T represents a novel species of the genus Undibacterium, for which the name Undibacterium aquatile sp. nov. is proposed. The type strain is THG-DN7.3T ( = KCTC 42243T = CCTCC AB 2015119T).

Brachybacterium horti sp. nov., isolated from garden soil

A bacterial strain, THG-S15-4T, was isolated from garden soil taken from the Guro-gu district of Seoul, Republic of Korea. Strain THG-S15-4T was Gram-stain-positive, facultatively anaerobic, coccus-shaped and non-motile, forming white colonies. The strain grew optimally at 25-37 °C, at pH 7.0 and in the presence of 0-2.0 % (w/v) NaCl. Phylogenetic analysis, based on 16S rRNA gene sequences, showed that strain THG-S15-4T was affiliated to species of the genus Brachybacterium, and the most closely related species were Brachybacterium rhamnosum KCTC 9917 T (98.5 % sequence similarity) and Brachybacterium squillarum KCTC 19899T (96.9 % sequence similarity). The DNA-DNA relatedness between strain THG-S15-4T and B. rhamnosum KCTC 9917 T was found to be below 20.0 %. The DNA G+C content was determined to be 69.5 mol%. The major isoprenoid quinone detected was MK-7. Strain THG-S15-4T was characterized chemotaxonomically as having meso-diaminopimelic acid in the cell-wall peptidoglycan. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, unidentified glycolipids and an unidentified polar lipid. The major fatty acids were found to be iso-C16 : 0 and anteiso-C15 : 0. The results of physiological and biochemical tests enabled strain THG-S15-4T to be differentiated phenotypically from species of the genus Brachybacterium with validly published names. Therefore, it is suggested that this newly isolated organism represents a novel species, for which the name Brachybacterium horti sp. nov. is proposed. The type strain is THG-S15-4T ( = KCTC 39563T = CCTCC AB 2015116T).

Pseudoxanthomonas humi sp. nov., a bacterium isolated from rhizospheric soil of Fraxinus chinensis in Gyeonggi Province, South Korea

A novel bacterial strain THG-MM13(T) was isolated from rhizospheric soil sample and was characterized by using a polyphasic approach. Cells were Gram-reaction-negative, non-motile and rod-shaped. The strain was aerobic, catalase and oxidase positive, and optimum growth temperature and pH were 28 °C and 7.0, respectively. On the basis of 16S rRNA gene sequence analysis, strain THG-MM13(T) (KM598260) belongs to the genus Pseudoxanthomonas and is most closely related to Pseudoxanthomonas wuyuanensis KCTC 23877(T) (97.4 %) (JN247803), followed by Pseudoxanthomonas koreensis KCTC 12208(T) (96.7 %) (AY550263) and Pseudoxanthomonas yeongjuensis KACC 11580(T) (96.7 %) (DQ438977). The DNA G + C content was 63.7 mol%, and the predominant respiratory quinone was ubiquinone-8. The major polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. The major fatty acids were iso-C15:0 (31.3 %) and iso-C16:0 (19.3 %). The DNA-DNA relatedness value between strain THG-MM13(T) and P. wuyuanensis KCTC 23877(T) was below 50 %. The DNA-DNA hybridization result and results of the genotypic analysis in combination with chemotaxonomic and physiological data demonstrated that strain THG-MM13(T) represented a novel species within the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas humi is proposed. The type strain is THG-MM13(T) (=KACC 18280(T) = CCTCC AB 2015122(T)).

Lysobacter novalis sp. nov., isolated from fallow farmland soil

A novel bacterial strain, designated THG-PC7T, was isolated from fallow farmland soil in Yongin, South Korea. Cells of strain THG-PC7T were Gram-stain-negative, dark yellow, aerobic, rod-shaped and had gliding motility. Strain THG-PC7T grew optimally at 25–35 °C, at pH 7 and in the absence of NaCl. Comparative 16S rRNA gene sequence analysis identified strain THG-PC7T as belonging to the genus Lysobacter, exhibiting highest sequence similarity with Lysobacter ximonensis KCTC 22336T (98.7 %) followed by Lysobacter niastensis KACC 11588T (95.7 %). In DNA–DNA hybridization tests, DNA relatedness between strain THG-PC7T and its closest phylogenetic neighbour L. ximonensis was below 25 %. The DNA G+C content of the novel isolate was determined to be 62.5 mol%. Flexirubin-type pigments were found to be present. The major cellular fatty acids were determined to be iso-C15 : 0, iso-C16 : 0, anteiso-C15 : 0 and iso-C17 : 1ω9c. The major respiratory quinone was identified as ubiquonone-8 (Q8). The predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and an unidentified aminophospolipid. On the basis of results from DNA–DNA hybridization and the polyphasic data, strain THG-PC7T represents a novel species of the genus Lysobacter, for which the name Lysobacter novalis sp. nov. is proposed. The type strain is THG-PC7T( = KACC 18276T = CCTCC AB 2014319T).

Phycicoccus soli sp. nov., isolated from soil

A Gram-stain-positive, non-motile, coccus-shaped bacterium, strain THG-a14T, was isolated from soil of Gyeyang mountain in Incheon, Republic of Korea. The isolate grew optimally at 28 °C, at pH 6.5–7.5 and with 0–3 % (w/v) NaCl. Based on 16S rRNA gene sequence comparisons, strain THG-a14T was closely related to Phycicoccus aerophilus 5516T-20T (97.7 %), P. ginsenosidimutans BXN5-13T (97.6 %), ‘P. ochangensis’ L1b-b9 (97.4 %) and P. bigeumensis MSL-03 (97.2 %). The DNA G+C content of strain THG-a14T was 71.6 mol%. In DNA–DNA hybridization, the DNA–DNA relatedness between strain THG-a14T and its closest phylogenetically neighbours was below 50.0 %. Strain THG-a14T was characterized chemotaxonomically as having meso-diaminopimelic acid in the cell-wall peptidoglycan. Strain THG-a14T contained glucose and ribose as whole-cell-wall sugars and menaquinone MK-8(H4) as the major isoprenoid quinone. Polar lipids in strain THG-a14T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphoaminoglycolipids, unidentified phospholipids and unidentified lipids. The major fatty acids were iso-C16: 0, iso-C15: 0 and C17: 1ω8c. On the basis of our polyphasic taxonomy study, strain THG-a14T represents a novel species within the genus Phycicoccus, for which the name Phycicoccus soli sp. nov. is proposed. The type strain is THG-a14T ( = KACC 17892T = JCM 19837T).

Novosphingobium aquaticum sp. nov., isolated from lake water in Suwon, Republic of Korea

A novel Gram-stain negative, yellow coloured, strictly aerobic, rod-shaped, non-motile bacterium designated as THW-SA1(T), was isolated from lake water near Samsung apartment, Suwon, Republic of Korea. The phylogenetic analysis based on 16S rRNA gene sequences showed that strain THW-SA1(T) belongs to the genus Novosphingobium and is closely related to Novosphingobium taihuense (97.8 %) and Novosphingobium subterraneum (97.1 %). The DNA-DNA relatedness values between strain THW-SA1(T) and the most closely related type strains were found to be less than 30.0 %. The DNA G+C content was determined to be 67.5 mol%. The strain grows optimally at 25-28 °C, at pH 7.0, and in the presence of 0.5 % NaCl. The predominant isoprenoid quinone was identified as ubiquinone Q-10. The polar lipid profile comprises diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidyldimethylethanolamine, sphingoglycolipid, phosphatidylcholine, some unidentified phospholipids and some unidentified polar lipids. Fatty acids characteristic for this genus, such as C16:1, C14:0 2-OH, C16:1 ω6c and/or C16:1 ω7c (summed feature 3) and C18:1 ω6c and/or C18:1 ω7c (summed feature 8) were also detected. On the basis of the phenotypic and genotypic analysis, the strain THW-SA1(T) is considered to represent a novel species of the genus Novosphingobium, for which the name Novosphingobium aquaticum sp. nov. is proposed. The type strain is THW-SA1(T) (=KCTC 42608(T)=CCTCC AB 2015114(T)).

Lysobacter agri sp. nov., a bacterium isolated from soil

A bacterial strain, designated as THG-SKA3(T), was isolated from field soil of Kyung Hee University, South Korea. Cells of the isolate were observed to be Gram-negative, aerobic, rod-shaped and motile by gliding. The strain was found to grow optimally at 28 °C, at pH 7 and in absence of NaCl. Based on 16S rRNA gene sequence comparisons, strain THG-SKA3(T) shared highest sequence similarity with Lysobacter niastensis KACC 11588(T) followed by Lysobacter panacisoli KACC 17502(T), Lysobacter enzymogenes LMG 8762(T) and Lysobacter oryzae KCTC 22249(T). The G+C content of THG-SKA3(T) was determined to be 68.9 mol%. The DNA-DNA relatedness values between strain THG-SKA3(T) and its closest phylogenetic neighbors were below 25.0 %.The major polar lipids of strain THG-SKA3(T) were determined to be diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The predominant respiratory quinone was identified as ubiquinone 8 (Q-8). The major cellular fatty acids were identified as branched chain iso-C15:0, iso-C16:0 and unsaturated iso-C17:1 ω9c. On the basis of polyphasic data presented, it is evident that strain THG-SKA3(T) represents a novel species of the genus Lysobacter, for which the name Lysobacter agri sp. nov. (type strain THG-SKA3(T) = KACC 18283(T) = CSCTCC AB 2015126(T)) is proposed.

Lysobacter fragariae sp. nov. and Lysobacter rhizosphaerae sp. nov. isolated from rhizosphere of strawberry plant

Two bacterial strains, designated THG-DN8.7(T) and THG-DN8.3(T), were isolated from the rhizosphere of a strawberry plant in Gyeryong Mountain, South Korea. Cells of both isolates were observed to be Gram-negative, yellow-coloured and rod-shaped. Comparative 16S rRNA gene sequence analysis showed that strain THG-DN8.7(T) had highest sequence similarities to Lysobacter yangpyeongensis KACC 11407(T) (97.2 %), Lysobacter niabensis KACC 11587(T) (97.0 %) and Lysobacter oryzae KCTC 22249(T) (96.9 %), while strain THG-DN8.3(T) had closely similarity with L. niabensis KACC 11587(T) (98.1 %), L. oryzae KCTC 22249(T) (97.1 %) and L. yangpyeongensis KACC 11407(T) (96.1 %). DNA-DNA relatedness values between strains THG-DN8.7(T) and THG-DN8.3(T) and their closest phylogenetically neighbours were below 30.0 %, which indicates that strains THG-DN8.7(T) and THG-DN8.3(T) represent distinct species within the genus Lysobacter. Both strains were found to contain iso-C15:0, iso-C16:0 and iso-C17:1 ω9c as predominant fatty acids and ubiquinone-8 as major isoprenoid quinone. The major polar lipids were identified as phosphatidylethanolamine, phosphatidyl-N-methylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The DNA G+C content of strains THG-DN8.7(T) and THG-DN8.3(T) were determined to be 66.9 and 67.8 mol%, respectively. These data are consistent with the affiliation of the two new species represented by THG-DN8.7(T) and THG-DN8.3(T) to the genus Lysobacter. The names Lysobacter fragariae sp. nov. and Lysobacter rhizosphaerae sp. nov. are proposed for these species with the type strains THG-DN8.7(T) (=KCTC 42236(T) = JCM 30322(T)) and THG-DN8.3(T) (=KCTC 42237(T) = JCM 30321(T)), respectively.

Pedobacter daejeonensis sp. nov. and Pedobacter trunci sp. nov., isolated from an ancient tree trunk, and emended description of the genus Pedobacter

Two Gram-stain-negative, yellow, aerobic and rod-shaped bacterial isolates, designated THG-DN3.18(T) and THG-DN3.19(T), were isolated from an ancient tree trunk from Daejeon, South Korea. 16S rRNA gene sequence similarity showed that both strains belong to the genus Pedobacter within the family Sphingobacteriaceae . Strain THG-DN3.18(T) exhibited maximum sequence similarity with Pedobacter boryungensis KCTC 23344(T) (98.5%) while strain THG-DN3.19(T) exhibited maximum sequence similarity with Pedobacter nyackensis LMG 24260(T) (97.3%). In DNA-DNA hybridization tests, the two strains showed less than 35% relatedness with respect to closely related species of the genus Pedobacter . Both strains contained iso-C(15 : 0) and C(16 : 1)ω6c and/or C(16 : 1)ω7c (summed feature 3) as the predominant fatty acids and MK-7 as the major isoprenoid quinone. The DNA G+C contents of strains THG-DN3.18(T) and THG-DN3.19(T) were 35.5 and 40.1 mol%, respectively. The genotypic analysis, biochemical properties, and phenotypic and chemotaxonomic characteristics indicate that strains THG-DN3.18(T) and THG-DN3.19(T) represent novel species of the genus Pedobacter , for which the names Pedobacter daejeonensis sp. nov. and Pedobacter trunci sp. nov. are proposed. The type strains are THG-DN3.18(T) ( = KCTC 42230(T) = JCM 30352(T)) and THG-DN3.19(T) ( = KCTC 42233(T) = JCM 30353(T)), respectively.

Microbiological accumulation by the Mediterranean invasive alien species Branchiomma bairdi (Annelida, Sabellidae): potential tool for bioremediation

We examined the bacterial accumulation and digestion in the alien polychaete Branchiomma bairdi. Microbiological analyses were performed on worm homogenates from "unstarved" and "starved" individuals and on seawater from the same sampling site (Ionian Sea, Italy). Densities of culturable heterotrophic bacteria (22 °C), total culturable bacteria (37 °C) and vibrios were measured on Marine Agar 2216, Plate Count Agar and TCBS Agar, respectively. Microbial pollution indicators were determined by the most probable number method. B. bairdi was able to accumulate all the six considered microbiological groups which, however, differ in their resistance to digestion. B. bairdi results more efficient than the other two co-occurring sabellids in removing bacteria suggesting that it may counteract the effects of microbial pollution playing a potential role for in situ bioremediation. Thus a potential risk, such as the invasion of an alien species, could be transformed into a benefit with high potential commercial gain and economic feasibility.

Exposure to static magnetic field stimulates quorum sensing circuit in luminescent Vibrio strains of the Harveyi clade

In this study, the evidence of electron-dense magnetic inclusions with polyhedral shape in the cytoplasm of Harveyi clade Vibrio strain PS1, a bioluminescent bacterium living in symbiosis with marine organisms, led us to investigate the behavior of this bacterium under exposure to static magnetic fields ranging between 20 and 2000 Gauss. When compared to sham-exposed, the light emission of magnetic field-exposed bacteria growing on solid medium at 18°C ±0.1°C was increased up to two-fold as a function of dose and growth phase. Stimulation of bioluminescence by magnetic field was more pronounced during the post-exponential growth and stationary phase, and was lost when bacteria were grown in the presence of the iron chelator deferoxamine, which caused disassembly of the magnetic inclusions suggesting their involvement in magnetic response. As in luminescent Vibrio spp. bioluminescence is regulated by quorum sensing, possible effects of magnetic field exposure on quorum sensing were investigated. Measurement of mRNA levels by reverse transcriptase real time-PCR demonstrated that luxR regulatory gene and luxCDABE operon coding for luciferase and fatty acid reductase complex were significantly up-regulated in magnetic field-exposed bacteria. In contrast, genes coding for a type III secretion system, whose expression was negatively affected by LuxR, were down-regulated. Up-regulation of luxR paralleled with down-regulation of small RNAs that mediate destabilization of luxR mRNA in quorum sensing signaling pathways. The results of experiments with the well-studied Vibrio campbellii strain BB120 (originally classified as Vibrio harveyi) and derivative mutants unable to synthesize autoinducers suggest that the effects of magnetic fields on quorum sensing may be mediated by AI-2, the interspecies quorum sensing signal molecule.

Characterization of vibrios diversity in the mucus of the polychaete Myxicola infundibulum (Annellida, Polichaeta)

Vibrios are among the most abundant culturable microbes in aquatic environments. They can be either free-living in the water column or associated with several marine organisms as mutualists, saprophytes, or parasites. In the present study we analysed vibrios abundance and diversity in the mucus of the polychaete Myxicola infundibulum, complementing culture-based with molecular methods. Vibrios reached 4.6 × 10(3) CFU mL(-1) thus representing a conspicuous component of the heterotrophic culturable bacteria. In addition, luminous vibrios accounted for about 60% of the total culturable vibrios in the mucus. The isolates were assigned to: Vibrio gigantis, Vibrio fischeri, Vibrio jasicida, Vibrio crassostreae, Vibrio kanaloae, and Vibrio xuii. Two Vibrio isolates (MI-13 and MI-15) may belong to a new species. We also tested the ability of the Vibrio isolates to grow on M. infundibulum mucus as the sole carbon source. All strains showed appreciable growth in the presence of mucus, leading us to conclude that this matrix, which is abundant and covers the animal entirely, may represent a microcosm and a food source for some bacteria, playing a crucial role in the structuring of a mucus-associated beneficial microbial community. Moreover, the trophic relationship between vibrios and M. infundibulum mucus could be enhanced by the protection that mucus offers to vibrios. The results of this study represent a contribution to the growing evidence for complex and dynamic invertebrate-microbe associations present in nature and highlight the importance of exploring relationships that Vibrio species establish with marine invertebrates.

Sphingomonas cynarae sp. nov., a proteobacterium that produces an unusual type of sphingan

Strain SPC-1T was isolated from the phyllosphere of Cynara cardunculus L. var. sylvestris (Lamk) Fiori (wild cardoon), a Mediterranean native plant considered to be the wild ancestor of the globe artichoke and cultivated cardoon. This Gram-stain-negative, catalase-positive, oxidase-negative, non-spore-forming, rod-shaped and non-motile strain secreted copious amounts of an exopolysaccharide, formed slimy, viscous, orange-pigmented colonies and grew optimally at around pH 6.0–6.5 and 26–30 °C in the presence of 0–0.5 % NaCl. Phylogenetic analysis based on comparisons of 16S rRNA gene sequences demonstrated that SPC-1T clustered together with species of the genus Sphingomonas sensu stricto. The G+C content of the DNA (66.1 mol%), the presence of Q-10 as the predominant ubiquinone, sym-homospermidine as the predominant polyamine, 2-hydroxymyristic acid (C14 : 0 2-OH) as the major hydroxylated fatty acid, the absence of 3-hydroxy fatty acids and the presence of sphingoglycolipid supported this taxonomic position. 16S rRNA gene sequence analysis showed that SPC-1T was most closely related to Sphingomonas hankookensis ODN7T, Sphingomonas insulae DS-28T and Sphingomonas panni C52T (98.19, 97.91 and 97.11 % sequence similarities, respectively). However, DNA–DNA hybridization analysis did not reveal any relatedness at the species level. Further differences were apparent in biochemical traits, and fatty acid, quinone and polyamine profiles leading us to conclude that strain SPC-1T represents a novel species of the genus Sphingomonas , for which the name Sphingomonas cynarae sp. nov. is proposed; the type strain is SPC-1T ( = JCM 17498T = ITEM 13494T). A component analysis of the exopolysaccharide suggested that it represents a novel type of sphingan containing glucose, rhamnose, mannose and galactose, while glucuronic acid, which is commonly found in sphingans, was not detected.

Epidemic mortality of the sponge Ircinia variabilis (Schmidt, 1862) associated to proliferation of a Vibrio bacterium

In recent years, several episodes of mass mortality of sessile epibenthic invertebrates, including sponges, have been recorded worldwide. In the present study, we report a disease event on Ircinia variabilis recorded in September 2009 along the southern Adriatic and Ionian seas (Apulian coast), with the aim to quantify the mortality incidence on the sponge population, to investigate the effect of the disease on the sponge tissues and to assess whether the disease is associated with vibrios proliferation. The injured sponges showed wide necrotic areas on the surface or disruption of the body in several portions. Necrotic areas were whitish and often were covered with a thin mucous coat formed by bacteria. In the most affected specimens, sponge organisation resulted partial or complete loss, with the final exposure of the dense skeletal network of spongine fibres to the environment. The results of microbiological cultural analysis using in parallel Marine Agar 2216 and thiosulphate/citrate/bile salts/sucrose agar demonstrated that, in affected specimens, vibrios represented 15.8 % of the total I. variabilis surface culturable bacteria. Moreover, all the isolated vibrios, grown from the wide whitish areas that characterize the surface of the diseased sponges, were identified, and their assignment to the Vibrio rotiferianus was consistent with phylogenetic analysis and data of morphological, cultural and biochemical tests. Studies on V. rotiferianus have shown that its pathogenicity, with respect to various aquatic organisms, is higher than that of Vibrio harveyi. The factors triggering the disease outbreak in Ircinia variabilis populations remain unclear. At present, we can hypothesize the involvement in the disease of a synergetic mechanism that, under stressful physiological conditions (high temperature, elevated nutrients and reduced water flow), induces sponge pathogens, in our case V. rotiferanius, to become virulent, making sponges unable to control their proliferation. Additional studies are needed to understand the etiological processes as well as the factors involved in sponges recovering from this epidemic event allowing them to face mass mortality. A drastic reduction of sponge-specific representatives could have marked a negative impact on the environmental health on account of their role in the sea remediation processes as filter-feeding organisms.

Biodiversity of prokaryotic communities associated with the ectoderm of Ectopleura crocea (Cnidaria, Hydrozoa)

The surface of many marine organisms is colonized by complex communities of microbes, yet our understanding of the diversity and role of host-associated microbes is still limited. We investigated the association between Ectopleura crocea (a colonial hydroid distributed worldwide in temperate waters) and prokaryotic assemblages colonizing the hydranth surface. We used, for the first time on a marine hydroid, a combination of electron and epifluorescence microscopy and 16S rDNA tag pyrosequencing to investigate the associated prokaryotic diversity. Dense assemblages of prokaryotes were associated with the hydrant surface. Two microbial morphotypes were observed: one horseshoe-shaped and one fusiform, worm-like. These prokaryotes were observed on the hydrozoan epidermis, but not in the portions covered by the perisarcal exoskeleton, and their abundance was higher in March while decreased in late spring. Molecular analyses showed that assemblages were dominated by Bacteria rather than Archaea. Bacterial assemblages were highly diversified, with up to 113 genera and 570 Operational Taxonomic Units (OTUs), many of which were rare and contributed to <0.4%. The two most abundant OTUs, likely corresponding to the two morphotypes present on the epidermis, were distantly related to Comamonadaceae (genus Delftia) and to Flavobacteriaceae (genus Polaribacter). Epibiontic bacteria were found on E. crocea from different geographic areas but not in other hydroid species in the same areas, suggesting that the host-microbe association is species-specific. This is the first detailed report of bacteria living on the hydrozoan epidermis, and indeed the first study reporting bacteria associated with the epithelium of E. crocea. Our results provide a starting point for future studies aiming at clarifying the role of this peculiar hydrozoan-bacterial association.

Susceptibility to antibiotics of Vibrio sp. AO1 growing in pure culture or in association with its hydroid host Aglaophenia octodonta (Cnidaria, Hydrozoa)

Vibrio harveyi is the major causal organism of vibriosis, causing potential devastation to diverse ranges of marine invertebrates over a wide geographical area. These microorganisms, however, are phenotypically diverse, and many of the isolates are also resistant to multiple antibiotics. In a previous study, we described a previously unknown association between Vibrio sp. AO1, a luminous bacterium related to the species V. harveyi, and the benthic hydrozoan Aglaophenia octodonta. In this study, we analyzed the susceptibility to antibiotics (ampicillin, streptomycin, tetracycline, or co-trimoxazole = mix of sulfamethoxazole and trimetoprim) of Vibrio sp. AO1 growing in pure culture or in association with its hydroid host by using microcosm experiments. The results of minimum inhibitory concentration (MIC) experiments demonstrated that Vibrio sp. AO1 was highly resistant to ampicillin and streptomycin in pure culture. Nevertheless, these antibiotics, when used at sub-MIC values, significantly reduced the hydroid fluorescence. Co-trimoxazole showed the highest inhibitory effect on fluorescence of A. octodonta. However, in all treatments, the fluorescence was reduced after 48 h, but never disappeared completely around the folds along the hydrocaulus and at the base of the hydrothecae of A. octodonta when the antibiotic was used at concentration completely inhibiting growth in vitro. The apparent discrepancy between the MIC data and the fluorescence patterns may be due to either heterogeneity of the bacterial population in terms of antibiotic susceptibility or specific chemical-physical conditions of the hydroid microenvironment that may decrease the antibiotic susceptibility of the whole population. The latter hypothesis is supported by scanning electron microscope evidence for development of bacterial biofilm on the hydroid surface. On the basis of the results obtained, we infer that A. octodonta might behave as a reservoir of antibiotic multiresistant bacteria, increasing the risk of their transfer into aquaculture farms.

Bioluminescence in the sea

Bioluminescence spans all oceanic dimensions and has evolved many times--from bacteria to fish--to powerfully influence behavioral and ecosystem dynamics. New methods and technology have brought great advances in understanding of the molecular basis of bioluminescence, its physiological control, and its significance in marine communities. Novel tools derived from understanding the chemistry of natural light-producing molecules have led to countless valuable applications, culminating recently in a related Nobel Prize. Marine organisms utilize bioluminescence for vital functions ranging from defense to reproduction. To understand these interactions and the distributions of luminous organisms, new instruments and platforms allow observations on individual to oceanographic scales. This review explores recent advances, including the chemical and molecular, phylogenetic and functional, community and oceanographic aspects of bioluminescence.