Genome analysis of sponge symbiont 'Candidatus Halichondribacter symbioticus' shows genomic adaptation to a host-dependent lifestyle.

The marine sponge Halichondria panicea inhabits coastal areas around the globe and is a widely studied sponge species in terms of its biology, yet the ecological functions of its dominant bacterial symbiont 'Candidatus Halichondribacter symbioticus' remain unknown. Here, we present the draft genome of 'Ca. H. symbioticus' HS1 (2.8 Mbp, ca. 87.6% genome coverage) recovered from the sponge metagenome of H. panicea in order to study functions and symbiotic interactions at the genome level. Functional genome comparison of HS1 against closely related free-living seawater bacteria revealed a reduction of genes associated with carbohydrate transport and transcription regulation, pointing towards a limited carbohydrate metabolism, and static transcriptional dynamics reminiscent of other bacterial symbionts. In addition, HS1 was enriched in sponge symbiont specific gene families related to host-symbiont interactions and defence. Similarity in the functional gene repertoire between HS1 and a phylogenetically more distant symbiont in the marine sponge Aplysina aerophoba, based on COG category distribution, suggest a convergent evolution of symbiont specific traits and general metabolic features. This warrants further investigation into convergent genomic evolution of symbionts across different sponge species and habitats.

Co-cultivation of the marine sponge Halichondria panicea and its associated microorganisms.

Marine sponges host bacterial symbionts with biotechnological potential, yet isolation of true sponge symbionts remains difficult due to their host dependency. Moreover, attempts to grow sponges for their pharmacologically-active compounds outside of their habitat often results in a shift of their microbial community. In this study we evaluate suitable sponge cultivation methods that allow maintenance of both the marine sponge Halichondria panicea and its associated bacteria in an ex situ environment. In addition, we present a method for co-cultivation of sponge explants and microbes separated by a membrane in a multi-chamber device. Tests on ex situ cultivation of H. panicea under different controlled conditions showed that only high water exchange rates in the aquarium enabled maintenance of its dominant symbiont "Candidatus Halichondribacter symbioticus" at a high relative abundance in the sponge body, a prerequisite for co-cultivation. The bacterial enrichment retrieved from co-cultivation contained bacteria from nine different classes in addition to sequences corresponding to "Ca. H. symbioticus". This represents an increase of the cultivable bacterial classes from H. panicea compared to standard isolation techniques on solid media plates. The current study provides insights into sponge-microbe maintenance under ex situ conditions and proposes a new method for the isolation of sponge-associated bacteria.

Pelagibaculum spongiae gen. nov., sp. nov., isolated from a marine sponge in South-West Iceland.

A Gram-stain-negative, motile, mesophilic, aerobic, rod-shaped bacterium, designated Hp12T, was isolated from a marine sponge in the intertidal zone off the coast of Seltjarnarnes (64° 16' N 22° 00' W), Iceland. Strain Hp12T grew optimally at 20-22 °C, at pH 7-8 and in the presence of 1-2 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences placed strain Hp12T in the class Gammaproteobacteria, related to members of the genus Alcanivorax in the order Oceanospirillales with 90.3-88.5 % sequence similarity. The strain had a draft genome size of 4.99 Mbp with a DNA G+C content of 43.0 mol%. Cellular fatty acids were dominated by C16 : 1 ω7c, C18 : 1 ω7c and C16 : 0. The predominant polar lipids were phosphatidylglycerol and phosphatidylethanolamine. The major respiratory lipoquinones were ubiquinone Q8 and menaquinone MK8. From the taxonomic information and phenotypic properties obtained in this study, it is proposed that strain Hp12T be placed into a novel genus and species named Pelagibaculum spongiae gen. nov., sp. nov. The type strain of Pelagibaculum spongiae is Hp12T (=DSM 104963T=CECT 9367T).

Bacterial diversity in the marine sponge Halichondria panicea from Icelandic waters and host-specificity of its dominant symbiont "Candidatus Halichondribacter symbioticus".

Marine sponges can harbour diverse bacteria that contribute to host metabolism and defence. Identifying these stable members of sponge bacterial communities remains a necessary step in understanding their ecological roles and underlying co-evolutionary processes. In this study, we applied high-throughput sequencing of 16S rRNA gene amplicons, ribosomal nucleotide variant analysis and fluorescence in situ hybridisation to characterise the core members of the bacterial community in the marine sponge Halichondria panicea from Icelandic waters. We show that the core bacterial community across all samples consisted of a single, dominant bacterial taxon, for which we propose a candidate status 'Candidatus Halichondribacter symbioticus'. Comparison against public databases showed that 'Ca. H. symbioticus' is both a highly abundant specialist in H. panicea and a low abundant opportunist in other sponge species. Additionally, H. panicea with and without 'Ca. H. symbioticus' co-exist in similar locations in the North Atlantic. This dichotomy paired with the presence of geographically distinct ribosomal sequence variants of the symbiont make H. panicea an interesting sponge species for studying sponge-symbiont co-evolution and functional interactions.

Biotechnological Potential of Cold Adapted Pseudoalteromonas spp. Isolated from 'Deep Sea' Sponges.

The marine genus Pseudoalteromonas is known for its versatile biotechnological potential with respect to the production of antimicrobials and enzymes of industrial interest. We have sequenced the genomes of three Pseudoalteromonas sp. strains isolated from different deep sea sponges on the Illumina MiSeq platform. The isolates have been screened for various industrially important enzymes and comparative genomics has been applied to investigate potential relationships between the isolates and their host organisms, while comparing them to free-living Pseudoalteromonas spp. from shallow and deep sea environments. The genomes of the sponge associated Pseudoalteromonas strains contained much lower levels of potential eukaryotic-like proteins which are known to be enriched in symbiotic sponge associated microorganisms, than might be expected for true sponge symbionts. While all the Pseudoalteromonas shared a large distinct subset of genes, nonetheless the number of unique and accessory genes is quite large and defines the pan-genome as open. Enzymatic screens indicate that a vast array of enzyme activities is expressed by the isolates, including ß-galactosidase, ß-glucosidase, and protease activities. A ß-glucosidase gene from one of the Pseudoalteromonas isolates, strain EB27 was heterologously expressed in Escherichia coli and, following biochemical characterization, the recombinant enzyme was found to be cold-adapted, thermolabile, halotolerant, and alkaline active.

Shelf life of air and modified atmosphere-packaged fresh tilapia (Oreochromis niloticus) fillets stored under chilled and superchilled conditions.

Optimal packaging and storage conditions for fresh tilapia fillets were established by evaluating sensory and microbiological changes, as well as monitoring physicochemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted, deskinned, and packaged in air and 50% CO2/50% N2 prior to chilling and superchilling storage at 1°C and -1°C. Sensory analysis of cooked samples revealed a shelf life of 13-15 days for air-packaged fillets during storage at 1°C and 20 days at -1°C. At the end of shelf life in air-packaged fillets, total viable counts (TVC) and pseudomonads counts reached log 8 colony-forming units (CFU) g(-1). In 50% CO2/50% N2-packaged fillets, the lag phase and generation time of bacteria were extended and recorded counts were below the limit for consumption (

Enzymatic hydrolysis of blue whiting (Micromesistius poutassou); functional and bioactive properties.

Functional and biochemical properties of fish protein hydrolysates (FPH) from blue whiting (BW) were studied. FPH (2.5%, 5%, 10%, and 15% degree of hydrolysis [DH]) were made from isolated proteins from headed and gutted BW with Alcalase 2.4 L. The properties of dried BW mince and protein isolate compared to 4 reference proteins (soy and milk protein) were studied: color, solubility, water-holding capacity (WHC), oil-binding capacity (OBC), emulsion capacity (EC), and emulsion stability (ES). The angiotensin I-converting enzyme (ACE) inhibitory activities of the soluble fraction of BW powders were also investigated. Furthermore, the products were characterized by analyzing their chemical composition. Chemical composition, solubility, OBC, and EC of the BW powders was significantly (P < 0.05) different with different DH, while color, ES, and WHC were not significantly (P > 0.05) different. Salt content of the FPH was high (4% to 19%) and increased with increased DH. Protein solubility varied from 10% to 70% and increased with increased DH. WHC of the FPH was around 97% and was higher than that of all the reference proteins tested. OBC decreased with increased DH (from 3.5 to 2.1 g oil/g protein) and was higher than OBC of the soy and milk proteins (1.6 to 1.9 g oil/g protein). EC of FPH was similar or lower than the reference proteins. ES of FPH (60% to 90%) was similar to or lower than soy and whey proteins (60% to 98%) but higher than casein (20%). ACE inhibition activity increased as DH was increased. Practical Application: The results from this study demonstrate that a functional bioactive hydrolysate can be produced from BW, which is an underutilized fish species, and may aid the industry in better utilizing this raw material. The novelty of this research was the use of BW as a raw material where the protein has been isolated with the pH shift method. Furthermore, it was novel that bioactivity and functionality was measured in the same samples.