Use of Bacteriophages to Control Vibrio Contamination of Microalgae Used as a Food Source for Oyster Larvae During Hatchery Culture.

Cultured microalgae are the primary food source for oyster larvae during hatchery culture and are a potential vector for Vibrio spp. infection of larval cultures. Bacteriophages have shown potential for controlling contamination of Vibrio spp. in aquaculture systems and their application could be an effective biological control method to eliminate such bacterial contamination of microalgae. This study investigated whether Vibrio-free microalgae sources could be ensured via the application of Vibrio specific phages. As a first step, four different Vibrio bacteriophages (belonging to the Myoviridae viral family) were isolated from marine waters in Queensland, Australia and used in challenge tests against a Vibrio host species, previously isolated from New South Wales oyster hatchery and found to be closely related to V. alginolyticus (ATCC 17749). The genome sequence of one of the four isolated bacteriophages, Vibrio Φ-2, that displayed strongest virulence against the host was determined. The 242446 bp genome of this bacteriophage was predicted to encode 217 proteins with an average GC content of 43.91%, containing putative thymidine kinases and a lysin enzyme. Application of these bacteriophages to pathogenic Vibrio spp. contaminating microalgae suspensions resulted in significant decreases in their numbers within 2 h. Findings indicated that direct application of bacteriophages to microalgae suspensions could be an effective method of reducing the occurrence of vibriosis in oyster hatcheries.

A novel role for Teneurin C-terminal Associated Peptide (TCAP) in the regulation of cardiac activity in the Sydney rock oyster, Saccostrea glomerata.

Teneurin C-terminal associated peptide (TCAP) is an ancient bioactive peptide that is highly conserved in metazoans. TCAP administration reduces cellular and behavioural stress in vertebrate and urochordate models, yet despite numerous studies in higher animals, there is limited knowledge of its role in invertebrates. In particular, there are no studies on TCAP's effects on the heart of any metazoan, which is a critical organ in the stress response. We used the Sydney rock oyster (SRO) as an invertebrate model to investigate a potential role for sroTCAP in regulating cardiac activity, including during stress. sroTCAP is localized to the neural innervation network of the SRO heart, and suggested binding with various heart proteins related to metabolism and stress, including SOD, GAPDH and metabotropic glutamate receptor. Intramuscular injection of sroTCAP (10 pmol) significantly altered the expression of heart genes that are known to regulate remodelling processes under different conditions, and modulated several gene families responsible for stress mitigation. sroTCAP (1 and 10 pmol) was shown to cause transient bradycardia (heart rate was reduced by up to 63% and for up to 40 min post-administration), indicative of an unstressed state. In summary, this study has established a role for a TCAP in the regulation of cardiac activity through modulation of physiological and molecular components associated with energy conservation, stress and adaptation. This represents a novel function for TCAP and may have implications for higher-order metazoans.

Teneurin and TCAP Phylogeny and Physiology: Molecular Analysis, Immune Activity, and Transcriptomic Analysis of the Stress Response in the Sydney Rock Oyster (Saccostrea glomerata) Hemocytes.

Teneurin C-terminal associated peptide (TCAP) is an ancient bioactive peptide that is highly conserved in metazoans. TCAP administration reduces cellular and behavioral stress in vertebrate and urochordate models. There is little information for invertebrates regarding the existence or function of a TCAP. This study used the Sydney rock oyster (SRO) as a molluscan model to characterize an invertebrate TCAP, from molecular gene analysis to its physiological effects associated with hemocyte phagocytosis. We report a single teneurin gene (and 4 teneurin splice variants), which encodes a precursor with TCAP that shares a vertebrate-like motif, and is similar to that of other molluscan classes (gastropod, cephalopod), arthropods and echinoderms. TCAP was identified in all SRO tissues using western blotting at 1-2 different molecular weights (~22 kDa and ~37kDa), supporting precursor cleavage variation. In SRO hemolymph, TCAP was spatially localized to the cytosol of hemocytes, and with particularly high density immunoreactivity in granules. Based on 'pull-down' assays, the SRO TCAP binds to GAPDH, suggesting that TCAP may protect cells from apoptosis under oxidative stress. Compared to sham injection, the intramuscular administration of TCAP (5 pmol) into oysters modulated their immune system by significantly reducing hemocyte phagocytosis under stress conditions (low salinity and high temperature). TCAP administration also significantly reduced hemocyte reactive oxygen species production at ambient conditions and after 48 h stress, compared to sham injection. Transcriptomic hemocyte analysis of stressed oysters administered with TCAP demonstrated significant changes in expression of genes associated with key metabolic, protective and immune functions. In summary, this study established a role for TCAP in oysters through modulation of physiological and molecular functions associated with energy conservation, stress and cellular defense.

Marine Protists and Rhodotorula Yeast as Bio-Convertors of Marine Waste into Nutrient-Rich Deposits for Mangrove Ecosystems.

This paper represents a comprehensive study of two new thraustochytrids and a marine Rhodotorula red yeast isolated from Australian coastal waters for their abilities to be a potential renewable feedstock for the nutraceutical, food, fishery and bioenergy industries. Mixotrophic growth of these species was assessed in the presence of different carbon sources: glycerol, glucose, fructose, galactose, xylose, and sucrose, starch, cellulose, malt extract, and potato peels. Up to 14g DW/L (4.6gDW/L-day and 2.8gDW/L-day) of biomass were produced by Aurantiochytrium and Thraustochytrium species, respectively. Thraustochytrids biomass contained up to 33% DW of lipids, rich in omega-3 polyunsaturated docosahexaenoic acid (C22:6, 124mg/g DW); up to 10.2mg/gDW of squalene and up to 61µg/gDW of total carotenoids, composed of astaxanthin, canthaxanthin, echinenone, and ß-carotene. Along with the accumulation of these added-value chemicals in biomass, thraustochytrid representatives showed the ability to secrete extracellular polysaccharide matrixes containing lipids and proteins. Rhodotorula sp lipids (26% DW) were enriched in palmitic acid (C16:0, 18mg/gDW) and oleic acid (C18:1, 41mg/gDW). Carotenoids (87µg/gDW) were mainly represented by ß-carotene (up to 54µg/gDW). Efficient growth on organic and inorganic sources of carbon and nitrogen from natural and anthropogenic wastewater pollutants along with intracellular and extracellular production of valuable nutrients makes the production of valuable chemicals from isolated species economical and sustainable.

Crustacean larval factor shares structural characteristics with the insect-specific follicle cell protein.

Literature on the cuticle formation in larval stages of the diverse group of decapod crustaceans is lacking, as opposed to a wealth of knowledge in several insect groups. Here we provide the first glimpse of the cuticular organisation in larvae of the eastern spiny lobster Sagmariasus verreauxi. A bioinformatic approach applied to S. verreauxi transcriptome through metamorphosis identified for the first time a small secreted protein with multiple isoforms that is highly expressed in crustacean larvae. This protein, named crustacean larval factor (Clf) shares structural characteristics with insect follicle cell protein 3 (FCP3), an insect-specific, rapidly evolving protein, with spatial-temporal regulated expression that is restricted to follicular cells during the production of the vitellin coat. Furthermore, we identified the FCP3 domain in additional structural proteins in multiple arthropod groups. Recombinant Clf inhibited in vitro calcium carbonate crystalline precipitation, in keeping with the finding that the spiny lobster larval cuticle is mainly composed of amorphous calcium carbonate. In addition, the recombinant Clf was shown to bind chitosan. Taken together, this research identifies two novel structural domains with lineage-specific expansion across arthropods. In crustaceans, Clf is found predominantly in larvae and the spatial-temporal regulated FCP3 factor occurs as a domain identified in multiple structural proteins across arthropods. Given the shared ten cysteines backbone between the Clf and FCP domains, a shared evolution is suggested and should be further explored.