Diversity, enumeration, and isolation of Arcobacter spp. in the giant abalone, Haliotis gigantea.

Arcobacter have been frequently detected in and isolated from bivalves, but there is very little information on the genus Arcobacter in the abalone, an important fishery resource. This study aimed to investigate the genetic diversity and abundance of bacteria from the genus Arcobacter in the Japanese giant abalone, Haliotis gigantea, using molecular methods such as Arcobacter-specific clone libraries and fluorescence in situ hybridization (FISH). Furthermore, we attempted to isolate the Arcobacter species detected. Twelve genotypes of clones were obtained from Arcobacter-specific clone libraries. These sequences are not classified with any other known Arcobacter species including pathogenic Arcobacter spp., A. butzleri, A. skirrowii, and A. cryaerophilus, commonly isolated or detected from bivalves. From the FISH analysis, we observed that ARC94F-positive cells, presumed to be Arcobacter, accounted for 6.96 ± 0.72% of all EUB338-positive cells. In the culture method, three genotypes of Arcobacter were isolated from abalones. One genotype had a similarity of 99.2%-100.0% to the 16S rRNA gene of Arcobacter marinus, while the others showed only 93.3%-94.3% similarity to other Arcobacter species. These data indicate that abalones carry Arcobacter as a common bacterial genus which includes uncultured species.

Arcobacter haliotis sp. nov., isolated from abalone species Haliotis gigantea.

A Gram-negative, aerobic, polar-flagellated and rod-shaped, sometimes slightly curved bacterium, designated MA5T, was isolated from the gut of an abalone of the species Haliotis gigantea collected in Japan. Phylogenetic analyses based on 16S rRNA, gyrB, hsp60 and rpoB gene sequences placed strain MA5T in the genus Arcobacter in an independent phylogenetic line. Comparison of the 16S rRNA gene sequence of this strain with those of the type strains of the established Arcobacter species revealed A. nitrofigilis (95.1 %) as nearest neighbour. Strain MA5T grew optimally at 25 °C, pH 6.0 to 9.0 and in the presence of 2 to 5 % (w/v) NaCl under both aerobic and microaerobic conditions. The predominant fatty acids found were summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c), C12 : 0 3-OH and C18 : 1 ω7c. Menaquinone-6 (MK-6) and menaquinone-7 (MK-7) were found as the major respiratory quinones. The major polar lipids detected were phosphatidylethanolamine and phosphatidylglycerol. Strain MA5T could be differentiated phenotypically from the phylogenetic closest Arcobacter species by its ability to grow on 0.05 % safranin and 0.01 % 2,3,5-triphenyl tetrazolium chloride (TTC), but not on 0.5 % NaCl. The obtained DNA G+C content of strain MA5T was 27.9 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic distinctiveness of MA5T, this strain is considered to represent a novel species of the genus Arcobacter, for which the name Arcobacter haliotis sp. nov. is proposed. The type strain is MA5T (=LMG 28652T=JCM 31147T).

Genome Sequence of Formosa haliotis Strain MA1, a Brown Alga-Degrading Bacterium Isolated from the Gut of Abalone Haliotis gigantea.

Formosa haliotis is a brown alga-degrading bacterium isolated from the gut of abalone Haliotis gigantea Here, we report the draft genome sequence of this bacterium and pointed out possible important features related to alginate degradation.

Formosa haliotis sp. nov., a brown-alga-degrading bacterium isolated from the gut of the abalone Haliotis gigantea.

Four brown-alga-degrading, Gram-stain-negative, aerobic, non-flagellated, gliding and rod-shaped bacteria, designated LMG 28520T, LMG 28521, LMG 28522 and LMG 28523, were isolated from the gut of the abalone Haliotis gigantea obtained in Japan. The four isolates had identical random amplified polymorphic DNA patterns and grew optimally at 25 °C, at pH 6.0-9.0 and in the presence of 1.0-4.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences placed the isolates in the genus Formosa with Formosa algae and Formosa arctica as closest neighbours. LMG 28520T and LMG 28522 showed 100 % DNA-DNA relatedness to each other, 16-17 % towards F. algae LMG 28216T and 17-20 % towards F. arctica LMG 28318T; they could be differentiated phenotypically from these established species. The predominant fatty acids of isolates LMG 28520T and LMG 28522 were summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1ω7c), iso-C15 : 1 G and iso-C15 : 0. Isolate LMG 28520T contained menaquinone-6 (MK-6) as the major respiratory quinone and phosphatidylethanolamine, two unknown aminolipids and an unknown lipid as the major polar lipids. The DNA G+C content was 34.4 mol% for LMG 28520T and 35.5 mol% for LMG 28522. On the basis of their phylogenetic and genetic distinctiveness, and differential phenotypic properties, the four isolates are considered to represent a novel species of the genus Formosa, for which the name Formosa haliotis sp. nov. is proposed. The type strain is LMG 28520T ( = NBRC 111189T).

Extracellular neutral lipids produced by the marine bacteria Marinobacter sp.

We analyzed the production of neutral lipids by the marine hydrocarbonoclastic bacteria Marinobacter sp. strain PAD-2 using hexadecane or succinate as the sole carbon source. Results showed that strain PAD-2 was able to grow and reduce the surface tension to 33±1.5 mN m(-1) and 58±1.5 mN m(-1) when n-hexadecane or succinate was used as the sole carbon source, respectively. The lipophilic compounds produced by Marinobacter sp. strain PAD-2 were extracted, and then crude lipophilic compounds, expected to be wax ester-like lipids, were analyzed by thin layer chromatography (TLC) . Furthermore, the lipophilic compound demonstrating surface activity was purified and subjected to gas chromatography/mass spectrometry (GC/MS) analysis. Although these did not give definite structural information due to the weak molecular ion peak (M(+)) , one component Ma-1 showed almost the same mass spectrum as that of component Fa-2, which represented a biosurfactant derived from Dietzia maris reported previously. Cell hydrophobicity was measured by a test of bacterial adhesion to hydrocarbons. A higher hydrophobic cell surface was observed in strain PAD-2. Extracellular wax ester-like compounds seem to be one type of the surface active compounds when bacteria grow on hexadecane or succinate as the sole carbon source.

Bacterial diversity associated with the rotifer Brachionus plicatilis sp. complex determined by culture-dependent and -independent methods.

The bacterial communities associated with rotifers (Brachionus plicatilis sp. complex) and their culture water were determined using culture-dependent and -independent methods (16S rRNA gene clone library). The bacterial communities determined by the culture-independent method were more diverse than those determined by the culture-dependent method. Although the culture-dependent method indicated the bacterial community of rotifers was relatively similar to that of the culture water, 16S rRNA gene clone library analyses revealed a great difference between the two microbiotas. Our results suggest that most bacteria associated with rotifers are not easily cultured using conventional methods, and that the microbiota of rotifers do not correspond with that of the culture water completely.

Wax ester-like compounds as biosurfactants produced by Dietzia maris from n-alkane as a sole carbon source.

The hydrocarbon-degrading bacterium Dietzia maris WR-3 was isolated from a consortium comprising ammonia-oxidizing and denitrifying bacteria derived from marine sediments. Here, we examined biosurfactant production by strain WR-3 when cultured using several different carbon (D-glucose, n -decane, n -hexadecane, motor oil, olive oil, and rapeseed oil) and nitrogen (NH(4) )(2) SO(4) , NaNO(3) , yeast extract, and polypeptone) sources as growth substrates. Strain WR-3 was able to grow and reduce the surface tension of culture broth to 31±1.0 mN m(-1) when cultured using n -hexadecane and nitrate ions. The surface-active compounds produced by strain WR-3 were extracted and analyzed by thin layer chromatography. Moreover, the main components in the extract were further purified and subjected to gas chromatography/mass spectrometry (GC/MS). From the analysis, the surface-active compounds were tentatively identified as wax ester-like compounds, which were synthesized from the degradation process of n -alkane. The production of surface-active compounds by strain WR-3 promoted attachment of cells to hydrocarbon droplets via increased cell hydrophobicity, thus allowing enhanced degradation of water immiscible substrates. As Dietzia spp. can grow and produce wax esters from the degradation process of hydrocarbons, these marine bacteria are potentially useful for the bioremediation of hydrocarbon-contaminated environments.