LPS-Induced Mortality in Zebrafish: Preliminary Characterisation of Common Fish Pathogens.

Disease outbreaks are a common problem in aquaculture, with serious economic consequences to the sector. Some of the most important bacterial diseases affecting aquaculture are caused by Gram-negative bacteria including spp. (vibriosis), (photobacteriosis), spp. (furunculosis; haemorrhagic septicaemia) or (tenacibaculosis). Lipopolysaccharides (LPS) are important components of the outer membrane of Gram-negative bacteria and have been linked to strong immunogenic responses in terrestrial vertebrates, playing a role in disease development. To evaluate LPS effects in fish, we used a hot-phenol procedure to extract LPS from common fish pathogens. , , and purified LPS were tested at different concentrations (50, 100, 250 and 500 µg mL) at 3 days post-fertilisation (dpf) larvae, for 5 days. While LPS did not cause any mortality under all concentrations tested, LPS induced 15.5% and LPS induced 58.3% of zebrafish larvae mortality at 500 µg mL. LPS from was revealed to be the deadliest, with a zebrafish larvae mortality percentage of 80.6%. Analysis of LPS separated by gel electrophoresis revealed differences in the overall LPS structure between the bacterial species analysed that might be the basis for the different mortalities observed.