Family Rhodobacteraceae Research Articles

Microbial Associations of Four Species of Algal Symbiont-bearing Foraminifers from the Florida Reef Tract, Usa

Abstract While microbiome research is a rapidly expanding field of study, relatively little is known of the microbiomes associated with Foraminifera. This preliminary study investigated microbes associated with four species of Foraminifera, representing two taxonomic orders, which host three kinds of algal endosymbionts. A major objective was to explore potential influences on the microbiome composition, including phylogenetic relatedness among the host species, similarities in algal symbionts hosted, and environmental conditions from which the specimens were collected. Samples examined from two locations along the middle Florida Keys reef tract included 45 foraminiferal specimens and four environmental samples. Bacterial DNA extraction from individual specimens was followed by amplification and amplicon sequencing of the V4 variable region of the 16S rRNA gene; results were obtained from 21 specimens. The Order Miliolida, Family Soritidae, was represented by 5–8 specimens of each of three species: Archaias angulatus and Cyclorbiculina compressa, which both host chlorophyte symbionts, and Sorites orbiculus, which hosts dinoflagellate symbionts. Three Ar. angulatus specimens from which the microbiome was successfully sequenced shared 177 OTUs. Six C. compressa specimens successfully sequenced shared 58 OTUs, of which 31 were also shared by the three specimens of Ar. angulatus. Four successfully sequenced S. orbiculus specimens shared 717 unique OTUs. The 13 soritid specimens shared 26 OTUs, 23 of which represented Proteobacteria, predominantly of the bacterial family Rhodobacteraceae. The fourth foraminiferal species, Amphistegina gibbosa (Order Rotaliida) hosts diatom endosymbionts. Bacterial DNA extraction was attempted on 16 Am. gibbosa, including both normal-appearing and partly-bleached specimens. Only six OTUs, four of which represented Proteobacteria, were found in all eight specimens successfully sequenced. The partly bleached specimens shared nearly twice as many unique microbial OTUs (32) as the normal-appearing specimens (19). All Am. gibbosa specimens shared only four microbial OTUs with the soritid species, three of which may have been contaminants, indicating minimal commonality between the microbiomes of Am. gibbosa and the soritid taxa.

Diet and diet-associated bacteria shape early microbiome development in Yellowtail Kingfish (Seriola lalandi).

SummaryThe supply of quality juveniles via land‐based larviculture represents a major bottleneck to the growing finfish aquaculture industry. As the microbiome plays a key role in animal health, this study aimed to assess the microbial community associated with early larval development of commercially raised Yellowtail Kingfish (Seriola lalandi). We used qPCR and 16S rRNA gene amplicon sequencing to monitor changes in the microbiome associated with the development of S. lalandi from larvae to juveniles. We observed an increase in the bacterial load during larval development, which consisted of a small but abundant core microbiota including taxa belonging to the families Rhodobacteraceae, Lactobacillaceae and Vibrionaceae. The greatest change in the microbiome occurred as larvae moved from a diet of live feeds to formulated pellets, characterized by a transition from Proteobacteria to Firmicutes as the dominant phylum. A prediction of bacterial gene functions found lipid metabolism and secondary metabolite production were abundant in the early larval stages, with carbohydrate and thiamine metabolism functions increasing in abundance as the larvae age and are fed formulated diets. Together, these results suggest that diet is a major contributor to the early microbiome development of commercially raised S. lalandi.

Oceanibium sediminis gen. nov., sp. nov., isolated from marine sediment.

A novel Gram-stain-negative, rod-shaped marine bacterium, designated as strain O448T, was isolated from the coastal area of Weihai, China (122° 14' E, 36° 54' N). Cells of strain O448T were non-motile, aerobic, approximately 0.4-0.6 µm wide and 1.5-2.0 µm long. Growth occurred at 20-40 °C (optimally between 33-37 °C), pH 6.5-8.0 (optimally at 7.0) and in the presence of 1.0-5.0 % (w/v) NaCl (optimally between 2.0-3.0 %). Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain O448T belongs to family Rhodobacteraceae and exhibits 16S rRNA gene sequence similarities of 94.3, 94.1 and 93.8 % to the type strains of Pontivivens insulae, Halovulum dunhuangense and Maritimibacter alkaliphilus, respectively. The major cellular fatty acid was C18 : 1ω7c and the major polar lipids were phosphatidylethanolamine, phosphatidylcholine and phosphatidylglycerol. Strain O448T contained Q-10 as the sole respiratory quinone. The genomic DNA G+C content was 65.6 mol%. It is evident from phenotypic data and phylogenetic inference that strain O448T represents a novel species in a new genus, for which the name Oceanibiumsediminis gen. nov., sp. nov. is proposed. The type strain is O448T (=KCTC 62076T=MCCC 1H00233T).

Roseovarius ponticola sp. nov., a novel lipolytic bacterium of the family Rhodobacteraceae isolated from seawater.

A lipolytic, Gram-negative, aerobic, non-motile and pleomorphic bacterial strain, designated W-SW3T, was isolated from seawater around Wando, an island of South Korea, and its taxonomic position was determined using a polyphasic approach. Its optimal growth occurred at 30°C, pH 7.0-8.0 and 2.0-4.0% (w/v) NaCl. Neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain W-SW3T belonged to the genus Roseovarius of the family Rhodobacteraceae, by showing the highest 16S rRNA gene sequence similarity value (97.3%) to the type strain of Roseovarius nanhaiticus. Strain W-SW3T exhibited 16S rRNA gene sequence similarities of 93.2-95.6% to the type strains of the other Roseovarius species. Ubiquinone-10 was found as the predominant ubiquinone and C18:1ω7c and C16:0 were found as the major fatty acids. Phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified lipid and one unidentified aminolipid were major polar lipids detected. The DNA G + C content of strain W-SW3T was 63.9mol%. Mean DNA-DNA relatedness values of strain W-SW3T with the type strains of R. nanhaiticus and R. antarcticus were 18 and 9%, respectively. The phenotypic properties, together with the phylogenetic and genetic data, made it possible strain W-SW3T to be separated from other recognized species of the genus Roseovarius. On the basis of the data presented, strain W-SW3T represents a novel species of the genus Roseovarius, for which the name Roseovarius ponticola sp. nov. is proposed. The type strain is W-SW3T (= KCTC 62424T = KACC 19615T = NBRC 113186T).

Arenibacillus arenosus gen. nov., sp. nov., a member of the family Rhodobacteraceae isolated from sea sand.

A Gram-stain-negative, aerobic, non-motile, non-spore-forming, rod-shaped bacterial strain, designated CAU 1304T, was isolated from sea sand. Strain CAU 1304T grew optimally at pH 8.5 and 30 °C and in the presence of 1 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CAU 1304T belonged to the family Rhodobacteraceae, and was most closely related to Roseicitreum antarcticum ZS2-28T (96.54 % similarity) and Rhodobacter veldkampii ATCC 35703T (96.46 %). The major fatty acid was C18 : 1ω7c and the respiratory quinone was Q-10. The polar lipids were composed of phosphatidylglycerol, phosphatidylcholine and an unidentified aminolipid. The DNA G+C content was 55.9 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic analysis, it is proposed that strain CAU 1304T represents a novel species of a new genus of the family Rhodobacteraceae, for which the name Arenibacillus arenosus gen. nov., sp. nov. is proposed. The type strain of Arenibacillus arenosus is CAU 1304T (=KCTC 42827T=NBRC 113022T).

Litorivita pollutaquae gen. nov., sp. nov., a marine bacterium in the family Rhodobacteraceae isolated from surface seawater of Xiamen Port, China

A Gram-stain-negative Rhodobacterales strain, designated as FSX-11T, was isolated from surface seawater of Xiamen port in China. Strain FSX-11T showed less than 96.5 % 16S rRNA gene sequence similarity to the type strains of species with validly published names. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the novel isolate formed a distinct monophyletic clade within the family Rhodobacteriaceae and clustered distantly with the genera Thalassobius and Marivita. Cells of strain FSX-11T were non-motile, oval-shaped and facultative anaerobic. Optimal growth occurred at 20-30 °C, at pH 7.0-8.0 and in the presence of 2-3 % NaCl (w/v). The major respiratory quinone was ubiquinone-10. Summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), 11-methyl C18 : 1ω7c and C16 : 0 were the major fatty acids. The DNA G+C content of strain FSX-11T was 58.7 mol%. On the basis of phylogenetic analysis, phenotypic and chemotaxonomic characteristics and 16S rRNA gene signature nucleotide patterns, strain FSX-11T represents a novel species in a novel genus within the family Rhodobacteraceae, for which the name Litorivita pollutaquae gen. nov., sp. nov. is proposed. The type strain is FSX-11T (=JCM 32715T=MCCC 1K03503T).

Bacterial Communities in Tissues and Surficial Mucus of the Cold-Water Coral Paragorgia arborea

Coral bacterial associates can play important functional roles for the holobiont, such as nitrogen cycling, nutrient processing, and supporting immunity. While bacteria found within the microbiome of corals may benefit the host, they can also be linked to pathogenesis. In the deep-sea, cold-water corals, like their warm shallow-water counterparts, host bacterial communities, but have received little attention due to logistical constraints in sampling. In particular, bacteria associated with surficial mucus of cold-water corals have not yet been investigated. Here, tissue and mucus samples of Paragorgia arborea were collected from three submarine canyons along the continental slope of the Gulf of Maine. Bacterial DNA was extracted from tissue and mucus samples and sequencing of the V6-V8 hypervariable region of the 16S rRNA gene was performed using Illumina MiSeq. The bacterial communities associated with P. arborea compartments (tissue and mucus) and sampling locations (canyon) differed significantly in composition. Proteobacteria, Tenericutes, and Spirochaetes were the dominant phyla across the majority of coral tissue samples, with Gammaproteobacteria and Alphaproteobacteria identified as the largest Proteobacteria contributors across all samples. OTUs belonging to the taxa Spirochaeta, Mycoplasma, Flavobacteriaceae, Terasakiellaceae, Campylobacterales and Rickettsiales were identified as biomarkers (bacterial taxa significantly more abundant in a specific coral microhabitat) of P. arborea tissues, while Paracoccus was a biomarker of P. arborea mucus. Many of the recovered biomarker taxa may be involved in nitrogen cycling. Representatives from several bacterial families (Vibrionaceae, Campylobacteraceae, Rhodobacteraceae, Flavobacteraceae, and Burkholderiaceae) previously reported in diseased scleractinians, were present in P. arborea as rare bacterial taxa. Characterizing the bacterial associates present in visibly healthy coral colonies provides a benchmark of dominant and rare bacterial groups present in the cold-water coral holobiont. This is the first characterization of bacterial groups associated with P. arborea, examining both tissue- and mucus-specific communities.

Draft Genome Sequence of Pelagicola sp. Strain LXJ1103, Isolated from Coastal Surface Seawater.

Pelagicola sp. strain LXJ1103, a representative of a new species in the family Rhodobacteraceae, was isolated from the coastal surface waters in Xiamen, China. Here, we announce the draft genome sequence and initial findings from a preliminary analysis of strain LXJ1103.

Cyclopropane-Containing Fatty Acids from the Marine Bacterium Labrenzia sp. 011 with Antimicrobial and GPR84 Activity.

Bacteria of the family Rhodobacteraceae are widespread in marine environments and known to colonize surfaces, such as those of e.g., oysters and shells. The marine bacterium Labrenzia sp. 011 is here investigated and it was found to produce two cyclopropane-containing medium-chain fatty acids (1, 2), which inhibit the growth of a range of bacteria and fungi, most effectively that of a causative agent of Roseovarius oyster disease (ROD), Pseudoroseovarius crassostreae DSM 16950. Additionally, compound 2 acts as a potent partial, β-arrestin-biased agonist at the medium-chain fatty acid-activated orphan G-protein coupled receptor GPR84, which is highly expressed on immune cells. The genome of Labrenzia sp. 011 was sequenced and bioinformatically compared with those of other Labrenzia spp. This analysis revealed several cyclopropane fatty acid synthases (CFAS) conserved in all Labrenzia strains analyzed and a putative gene cluster encoding for two distinct CFASs is proposed as the biosynthetic origin of 1 and 2.

Cross-exchange of B-vitamins underpins a mutualistic interaction between Ostreococcus tauri and Dinoroseobacter shibae.

Ostreococcus tauri, a picoeukaryotic alga that contributes significantly to primary production in oligotrophic waters, has a highly streamlined genome, lacking the genetic capacity to grow without the vitamins thiamine (B1) and cobalamin (B12). Here we demonstrate that the B12 and B1 auxotrophy of O. tauri can be alleviated by co-culturing with a heterotrophic bacterial partner Dinoroseobacter shibae, a member of the Rhodobacteraceae family of alpha-proteobacteria, genera of which are frequently found associated with marine algae. D. shibae lacks the complete pathway to synthesise three other B-vitamins: niacin (B3), biotin (B7), and p-aminobenzoic acid (a precursor for folate, B9), and the alga is in turn able to satisfy the reciprocal vitamin requirements of its bacterial partner in a stable long-term co-culture. Bioinformatics searches of 197 representative marine bacteria with sequenced genomes identified just nine species that had a similar combination of traits (ability to make vitamin B12, but missing one or more genes for niacin and biotin biosynthesis enzymes), all of which were from the Rhodobacteraceae. Further analysis of 70 species from this family revealed the majority encoded the B12 pathway, but only half were able to make niacin, and fewer than 13% biotin. These characteristics may have either contributed to or resulted from the tendency of members of this lineage to adopt lifestyles in close association with algae. This study provides a nuanced view of bacterial-phytoplankton interactions, emphasising the complexity of the sources, sinks and dynamic cycling between marine microbes of these important organic micronutrients.

Pelagivirga sediminicola gen. nov., sp. nov. isolated from the Bohai Sea.

A Gram-stain-negative bacterium, strain BH-SD19T, that was isolated from a marine sediment sample collected from the Bohai Sea, was subjected to a polyphasic taxonomic study. Cells of BH-SD19T are non-flagellated, non-gliding, oval-shaped rods, 0.5-1.0 µm wide and 1.0-2.0 µm long. BH-SD19T is strictly aerobic, and oxidase- and catalase-positive. Growth occurs at 15-40 °C (optimum 35 °C), at pH 6.0-8.5 (optimum 7.0-7.5) and with 1-10 % (w/v) NaCl (optimum 2 %). The predominant fatty acids are C19 : 0cyclo ω8c (46.5 %), C16 : 0 (20.3 %) and C18 : 1ω7c and/or C18 : 1ω6c (10.6 %). The major respiratory quinone is Q-10. The major polar lipids are phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. The DNA G+C content is 64.0 mol%. BH-SD19T shows the highest 16S rRNA sequence similarity to Pontibaca methylaminivorans (95.2 %) and strains of species of the genus Roseovarius(93.4-95.2 %). Sequence similarity values between BH-SD19T and other phylogenetically related species are all below 95.0 %. Phylogenetic trees based on 16S rRNA gene sequences indicate that BH-SD19T forms a distinct lineage and does not join any known genera in the trees. Phenotypic, chemotaxonomic and phylogenetic data indicate that BH-SD19T represents a novel genus and species in the family Rhodobacteraceae, for which the name Pelagivirga sediminicola gen. nov., sp. nov. is proposed. The type strain is BH-SD19T (=CCTCC AB 2017074T=KCTC 62202T).

Spatial and temporal characterization of epiphytic microbial communities associated with Eurasian watermilfoil: a highly invasive macrophyte in North America.

Bacterial communities that inhabit the surface of aquatic plants are thought to play a critical role in relation to host fitness and function. However, little is known about their structure and dynamics in comparison with those of bacterioplankton. In this study, we performed a comprehensive spatial and temporal characterization of epibacterial communities associated with Eurasian watermilfoil (EWM; Myriophyllum spicatum), an invasive macrophyte, which has established itself in thousands of lakes across North America. EWM samples were collected from 10 lakes in Minnesota, once a month, for six consecutive months, along with surrounding water and sediment. High-throughput DNA sequencing analyses, performed on all samples (n = 522) using the Illumina platform, indicated that EWM-associated epibacterial communities were distinct from those found in water and sediment. EWM-specific microbiota was comprised of operational taxonomic units classified to the families Rhodobacteraceae, Comamonadaceae, Cyanobacteria Subsection I Family I, Aeromonadaceae, Planctomycetaceae, Sphingomonadaceae and Verrucomicrobiaceae. In addition, several identified taxa were overrepresented in EWM samples when compared to water and sediment. Amongst all the environmental factors examined, water temperature had the greatest influence on epibacterial community structure. Our findings suggest that EWM harbor specific, but temporally adapted, epibacterial communities that are potentially involved in host-microbe interactions.

Acuticoccus kandeliae sp. nov., isolated from rhizosphere soil of the mangrove plant Kandelia, and emended description of Acuticoccus yangtzensis.

A novel bacterial strain, J103T, was isolated from rhizosphere soil of the mangrove plant Kandelia in Mai Po Inner Deep Bay Ramsar Site, Hong Kong. The strain was aerobic, Gram-stain-negative, oval-shaped with folds in the middle, non-motile and non-spore-forming. It grew at temperatures of 20-30 °C (optimum, 25-30 °C), at pH 6.0-9.0 (optimum pH 6.0) and at NaCl concentrations of 0.5-5.0 % (w/v) (optimum 1.0-2.0 %). Strain J103T was able to reduce nitrate to nitrite, and hydrolyse urea, Tween 40 and Tween 60. The major polar lipids were aminolipid, glycolipid, phosphatidylcholine and phosphatidylglycerol. The major fatty acids were C18 : 1ω7c and C19 : 0 cyclo ω8c. The respiratory quinone was Q-10. The DNA G+C content was 68.5 mol%. Sequence analysis of the 16S rRNA gene indicated that strain J103T belongs to the genus Acuticoccus, within the family Rhodobacteraceae. The closest phylogenetic neighbour was Acuticoccus yangtzensis JL1095T, showing 96.2 % 16S rRNA gene sequence similarity. The genome size of strain J103T was 6 478 100 bp. The average nucleotide identity and digital DNA-DNA hybridization values between strain J103T and Acuticoccus yangtzensis JL1095T were 75.44 and 16.43 %, respectively. Characterization based on phylogenetic, phenotypic, chemotaxonomic and genomic evidence demonstrated that strain J103T represents a novel species of the genus Acuticoccus, for which the name Acuticoccus kandeliae sp. nov. is proposed. The type strain is J103T (=DSM 104434T=MCCC 1K03288T).

Elucidation of glutamine lipid biosynthesis in marine bacteria reveals its importance under phosphorus deplete growth in Rhodobacteraceae

Marine microorganisms employ multiple strategies to cope with transient and persistent nutrient limitation, one of which, for alleviating phosphorus (P) stress, is to substitute membrane glycerophospholipids with non-P containing surrogate lipids. Such a membrane lipid remodelling strategy enables the most abundant marine phytoplankton and heterotrophic bacteria to adapt successfully to nutrient scarcity in marine surface waters. An important group of non-P lipids, the aminolipids which lack a diacylglycerol backbone, are poorly studied in marine microbes. Here, using a combination of genetic, lipidomics and metagenomics approaches, we reveal for the first time the genes (glsB, olsA) required for the formation of the glutamine-containing aminolipid. Construction of a knockout mutant in either glsB or olsA in the model marine bacterium Ruegeria pomeroyi DSS-3 completely abolished glutamine lipid production. Moreover, both mutants showed a considerable growth cost under P-deplete conditions and the olsA mutant, that is unable to produce the glutamine and ornithine aminolipids, ceased to grow under P-deplete conditions. Analysis of sequenced microbial genomes show that glsB is primarily confined to the Rhodobacteraceae family, which includes the ecologically important marine Roseobacter clade that are key players in the marine sulphur and nitrogen cycles. Analysis of the genes involved in glutamine lipid biosynthesis in the Tara ocean metagenome dataset revealed the global occurrence of glsB in marine surface waters and a positive correlation between glsB abundance and N* (a measure of the deviation from the canonical Redfield ratio), suggesting glutamine lipid plays an important role in the adaptation of marine Rhodobacteraceae to P limitation.

Primorskyibacter marinus sp. nov., isolated from coastal sediment.

A novel Gram-stain-negative, whitish-yellow, rod-shaped, non-pigmented, aerobic, oxidase-positive and catalase-positive bacterium, designated PX7T, was isolated from coastal sediment of Xiaoshi Island, Weihai, China (37° 31' 36″ N, 122° 00' 58″ E). Strain PX7T grew optimally at 30 °C, at pH 7.0-7.5 and in the presence of 3.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PX7T formed a robust clade with members of the genus Primorskyibacter and was closely related to Primorskyibacter sedentarius, Primorskyibacter aestuariivivens and Primorskyibacter insulae with 96.5, 96.2 and 95.1 % sequence similarities, respectively. The sole respiratory quinone of strain PX7T was ubiquinone-10, and the dominant fatty acid was C18 : 1ω7c (80.2 %). The major polar lipids were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, one unidentified aminolipid, one unidentified phospholipid and one unidentified lipid. The DNA G+C content of strain PX7T was 60.2 mol%. Based on the combination of phylogenetic analyses, phenotypic and chemotaxonomic data, strain PX7T is considered to represent a novel species within the genus Primorskyibacter in the family Rhodobacteraceae, for which the name Primorskyibacter marinus sp. nov. is proposed. The type strain of the new species is PX7T (=KCTC 42952T=MCCC 1H00196T).

Exploring the Impact of the Biofloc Rearing System and an Oral WSSV Challenge on the Intestinal Bacteriome of Litopenaeus vannamei

We provide a global overview of the intestinal bacteriome of Litopenaeus vannamei in two rearing systems and after an oral challenge by the White spot syndrome virus (WSSV). By using a high-throughput 16S rRNA gene sequencing technology, we identified and compared the composition and abundance of bacterial communities from the midgut of shrimp reared in the super-intensive biofloc technology (BFT) and clear seawater system (CWS). The predominant bacterial group belonged to the phylum Proteobacteria, followed by the phyla Bacteroidetes, Actinobacteria, and Firmicutes. Within Proteobacteria, the family Vibrionaceae, which includes opportunistic shrimp pathogens, was more abundant in CWS than in BFT-reared shrimp. Whereas the families Rhodobacteraceae and Enterobacteriaceae accounted for almost 20% of the bacterial communities of shrimp cultured in BFT, they corresponded to less than 3% in CWS-reared animals. Interestingly, the WSSV challenge dramatically changed the bacterial communities in terms of composition and abundance in comparison to its related unchallenged group. Proteobacteria remained the dominant phylum. Vibrionaceae was the most affected in BFT-reared shrimp (from 11.35 to 20.80%). By contrast, in CWS-reared animals the abundance of this family decreased from 68.23 to 23.38%. Our results provide new evidence on the influence of both abiotic and biotic factors on the gut bacteriome of aquatic species of commercial interest.

Microbiomes of gall-inducing copepod crustaceans from the corals Stylophora pistillata (Scleractinia) and Gorgonia ventalina (Alcyonacea)

Corals harbor complex and diverse microbial communities that strongly impact host fitness and resistance to diseases, but these microbes themselves can be influenced by stresses, like those caused by the presence of macroscopic symbionts. In addition to directly influencing the host, symbionts may transmit pathogenic microbial communities. We analyzed two coral gall-forming copepod systems by using 16S rRNA gene metagenomic sequencing: (1) the sea fan Gorgonia ventalina with copepods of the genus Sphaerippe from the Caribbean and (2) the scleractinian coral Stylophora pistillata with copepods of the genus Spaniomolgus from the Saudi Arabian part of the Red Sea. We show that bacterial communities in these two systems were substantially different with Actinobacteria, Alphaproteobacteria, and Betaproteobacteria more prevalent in samples from Gorgonia ventalina, and Gammaproteobacteria in Stylophora pistillata. In Stylophora pistillata, normal coral microbiomes were enriched with the common coral symbiont Endozoicomonas and some unclassified bacteria, while copepod and gall-tissue microbiomes were highly enriched with the family ME2 (Oceanospirillales) or Rhodobacteraceae. In Gorgonia ventalina, no bacterial group had significantly different prevalence in the normal coral tissues, copepods, and injured tissues. The total microbiome composition of polyps injured by copepods was different. Contrary to our expectations, the microbial community composition of the injured gall tissues was not directly affected by the microbiome of the gall-forming symbiont copepods.

Understanding bacterial communities for informed biosecurity and improved larval survival in Pacific oysters

Bacteria are ubiquitous in all marine habitats and can be beneficial or detrimental to the survival and growth of shellfish raised in aquaculture. To reduce the exposure of cultured shellfish to potential pathogens, antibiotics can be used. However, risks associated with this practice have led to the development of alternative techniques such as ultraviolet (UV) light exposure for seawater disinfection. In this study, we used 16S rRNA gene metabarcoding to measure the effect of low (50 mJoules/cm2) and high (200 mJoules/cm2) UV treatment of seawater on the bacterial communities present in hatchery rearing water and in Pacific oyster Crassostrea gigas larvae. 81 samples were collected between 13 and 29 March 2017 for high-throughput DNA sequencing of bacterial communities, including differentially-treated seawater, the microalgae fed to the oysters and oyster larvae (fertilized eggs, early veliger larval stage [D-larvae], and pre-settlement stage) samples. Differences in larval mortality between low and high UV treatments were also assessed. We found that the two UV treatments influenced the overall bacterial community diversity and affected its composition in both seawater and oyster larval samples. While alpha-diversity was mostly driven by the UV treatment, we found that the microbiome composition was primarily affected by temporal changes in the water source. Compared to the bacterial microbiome associated with seawater, the oyster larvae microbiome changed more significantly in response to both UV treatments and sampling dates with marked shifts in the dominant bacteria associated with fertilized eggs (class Gammaproteobacteria, families Rhodospirillaceae and Pelagibacteraceae), the D-larvae (family Alteromonadaceae), and the pre-settlement larvae (families Flavobacteriaceae and Rhodobacteraceae). As larval development progressed, an increasingly complex bacterial community structure was observed. These bacterial community changes were likely driven by multiple factors, including the microbiome associated with microalgal cultures, which increased in complexity over time. Despite the clear response of bacterial communities to both low and high UV treatments, no significant effect was observed in relation to the oyster larval mortality rate. These results suggest that increasing the UV treatment to 200 mJoules/cm2, if required for more efficacious disinfection and biosecurity, would not be detrimental to Pacific oyster larval survival. Further research is required to increase understanding of the dynamics of functionally critical bacterial taxa and their successive roles in post-larval development of Pacific oysters.

Xinfangfangia soli gen. nov., sp. nov., isolated from a diuron-polluted soil.

A novel Gram-staining-negative, non-motile and rod-shaped bacterial strain ZQBWT, which was isolated from a diuron-polluted soil collected near Nanjing, PR China, was investigated for its taxonomic position by a polyphasic approach. ZQBWT grew well at pH 6.0-12.0 (optimum, pH 7.0), 26-35 °C (optimum, 30 °C) and up to 0.5 % NaCl (optimally the absence of NaCl) in R2A broth. The major fatty acids of ZQBWT were C18 : 1ω7c (82.7 %) and C18 : 0 (5.3 %). The polar lipid profile included the major compounds phophatidylcholine, phosphatidylglycerol and phosphatidylmethylethanolamine. The only respiratory quinone was ubiquinone Q-10. The G+C content of genomic DNA was 67.0 mol%. Comparisons with 16S rRNA gene sequences revealed that ZQBWT has the highest sequence similarities with members of the genus Tabrizicola (≤95.97 %), followed by Rhodobacter(≤95.96 %) and Falsirhodobacter(95.95 %) which all belong to the family Rhodobacteraceaein the phylum Proteobacteria. Photosynthesis genes pufLM were not found and photosynthesis pigments were not formed in ZQBWT. On the basis of the results from chemotaxonomic, phenotypic and phylogenetic analysis, ZQBWT represents a novel species of a novel genus, for which the name Xinfangfangia soli gen. nov., sp. nov. is proposed. The type strain is ZQBWT (=KCTC 62102T=CCTCC AB 2017177T).

Ruegeria denitrificans sp. nov., a marine bacterium in the family Rhodobacteraceae with the potential ability for cyanophycin synthesis.

Strain CECT 5091T, an aerobic, marine, Gram-reaction- and Gram-stain-negative, chemoheterotrophic bacterium was isolated from oysters harvested off the Spanish Mediterranean coast. Analysis of the 16S rRNA gene sequence placed the strain within the genus Ruegeria, in the family Rhodobacteraceae, with 16S rRNA gene similarities of 98.7, 98.7 and 98.4 % to Ruegeria conchae, Ruegeria atlanticaand Ruegeria arenilitoris, respectively. Average nucleotide identities (ANI) and in silico DNA-DNA hybridization (DDH) were determined, comparing the genome sequence of CECT 5091T with those of the type strains of 12 species of the genus Ruegeria: the values obtained were always below the thresholds (95-96 % ANI, 70 % in silico DDH) used to define genomic species, proving that CECT 5091T represents a novel species of the genus Ruegeria. The strain was slightly halophilic and mesophilic, with optimum growth at 26 °C, pH 7.0 and 3 % salinity, it required sodium and magnesium ions for growth and was able to reduce nitrate to dinitrogen. Carbon sources for growth include some carbohydrates (d-ribose, d-glucose, l-rhamnose, N-acetyl-d-glucosamine) and multiple organic acids and amino acids. The major cellular fatty acid was summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), representing 70 % of the total fatty acids. Carbon monoxide oxidation, cyanophycin synthetic ability and phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine production are predicted from genome annotation, while bacteriochlorophyll a production was absent. The DNA G+C content of the genome was 56.7 mol%. We propose the name Ruegeriadenitrificans sp. nov. and strain CECT 5091T (=5OM10T=LMG 29896T) as the type strain for the novel species.