Aphanomyces invadans, the causal agent of Epizootic Ulcerative Syndrome, is a global threat to wild and farmed fish

Acknowledgements Our work is supported by the University of Aberdeen (PvW); BBSRC (BB/M026566/1 & BB/P020224/1: PvW); BBSRC (BB/N005058/1 & BB/J018333/1: FT & PvW); NERC (NE/P010873/1: PvW) and a PhD scholarship from Ministry of Education Malaysia (NAI).Peer reviewedPostprin

Cell entry of a host-targeting protein of oomycetes requires gp96

The animal-pathogenic oomycete Saprolegnia parasitica causes serious losses in aquaculture by infecting and killing freshwater fish. Like plant-pathogenic oomycetes, S. parasitica employs similar infection structures and secretes effector proteins that translocate into host cells to manipulate the host. Here, we show that the host-targeting protein SpHtp3 enters fish cells in a pathogen-independent manner. This uptake process is guided by a gp96-like receptor and can be inhibited by supramolecular tweezers. The C-terminus of SpHtp3 (containing the amino acid sequence YKARK), and not the N-terminal RxLR motif, is responsible for the uptake into host cells. Following translocation, SpHtp3 is released from vesicles into the cytoplasm by another host-targeting protein where it degrades nucleic acids. The effector translocation mechanism described here, is potentially also relevant for other pathogen-host interactions as gp96 is found in both animals and plants.This work is supported by the [European Community’s] Seventh Framework Programme [FP7/2007–2013] under grant agreement no. [238550] (L.L., J.D.-U., C.J.S., P.v.W.); BBSRC [BBE007120/1, BB/J018333/1 and BB/G012075/1] (F.T., I.d.B., C.J.S., S.W., P.v.W.); Newton Global Partnership Award [BB/N005058/1] (F.T., P.v.W.), the University of Aberdeen (A.D.T., T.R., C.J.S., P.v.W.) and Deutsche Forschungsgemeinschaft [CRC1093] (P.B., T.S.). We would like to acknowledge the Ministry of Higher Education Malaysia for funding INA. We would like to thank Brian Haas for his bioinformatics support. We would like to acknowledge Neil Gow and Johannes van den Boom for critical reading of the manuscript. We would like to acknowledge Svetlana Rezinciuc for technical help with pH-studies

In vitro and in vivo characterisations of Centella asiatica extract against Vibrio alginolyticus infection in whiteleg shrimp, Penaeus vannamei

Methanolic leaf extracts of the medicinal herb Centella asiatica (Asiatic pennywort) were screened for in vitro and in vivo antimicrobial activities against Vibrio alginolyticus isolated from whiteleg shrimp, Penaeus vannamei. Phytochemical analyses were positive for tannins, saponins, steroids, and cardiac glycosides. Antioxidant test revealed antioxidant activity nearly as potent as that of 0.8 mg/mL ascorbic acid. Minimum inhibitory and bactericidal concentrations against V. alginolyticus were determined to be 0.79 and 12.50 mg/mL respectively. Scanning electron microscopy demonstrated disruptions of treated bacterial cells. 30 mg/kg extract supplementation achieved 85% survival of juvenile shrimp in a feeding trial. Histopathology showed increasingly fewer alterations in hepatopancreas from 10, 20 to 30 mg/kg supplementation, where 30 mg/kg preserved the tissues most with relatively complete structure including the star-shaped tubule lumen and various cell types. The present findings suggest the potential of C. asiatica as an alternative antimicrobial agent against V. alginolyticus as well as other Vibrio spp. and gram-negative bacteria in aquaculture