Indigenous marine seaweeds and their biological activities have played a significant role in aquaculture especially
with regard to their antibacterial and antiviral properties. The bioactive compounds and the toxicity profile of
aqueous and ethanol extracts of Padina gymnospora andSargassum cinereum species were assessed for the treatment of bacterial infection. The optimum exposure to seaweed extracts varied with different concentrations,
from 100 mg/l to 500 mg/l of dried solvent extracts dispersed in 10 l of water. It was found to be non-toxic up
to 250 mg/l. Oreochromis mossambicus infected with Pseudomonas aeruginosa showed abnormal activities like
hyperactivity, lethargic movements, hemorrhagic lesions and exophthalmia, with LC 50 values of 1.287, 1.634
and 2.021 mg/l for 72, 96, 120 h respectively. They were exposed to sea weed extracts of different concentrations.
Insignificant mortality was seen in the treated group. PCR and histopathological analysis were done. PCR studies
were performed to study the distribution of P. aeruginosa in the tissues of different organs. The results revealed
that PCR was positive for gills, while skin showed mild positive, which indicates the presence of the bacteria in
these organs. The liver and the kidney were found to be negative.
Statement of relevance
The sea weed extracts are excellent source of antimicrobial compounds. These can be used for treating bacterial
infection as an alternative to antibiotics which cause resistance. The extracts are found to be nontoxic and can be
used in aquaculture industries for treating bacterial infection.
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