Papel de las actividades superóxido dismutasa y catalasa en la ...

RESULTS AND DISCUSSION
oxidative stress. Results obtained (articles 1.1. and 1.2., Article section) show that iron
plays an important role in survival of P. damselae subsp. piscicida in contact with sole
phagocytes; whether this is attributable to its contribution to capsular material or SOD
and catalase synthesis by the bacterium needs to be investigated. In conclusion, P.
damselae subsp. piscicida is able to survive in contact with sole phagocytes, survival
rates being higher for a virulent strain. The increased levels of catalase activity detected
in the virulent strain indicate a possible role for this enzyme in bacterial survival.
Once determined the role of superoxide dismutase and catalase activities in P.
damselae subsp. piscicida protection against respiratory burst of sole phagocyes, the
following topic to study was the search for prevention tools such as immunostimulant
application. This work has focused on the respiratory burst activity of sole phagocytes
to evaluate the possible immunostimulant effect of two types of microorganisms: a red
microalga, Porphyridium cruentum, and two potentially probiotic bacteria strains,
whose immunostimulant activity has been reported in mammals (Morris et al., 2000) and
gilthead seabream (Díaz-Rosales et al., 2006; Salinas et al., 2006) phagocytes,
respectively.
Evaluation of the potential stimulant activity of aqueous and ethanolic extracts
from P. cruentum indicated that none of them stimulated superoxide anion production,
while the positive control, commercial β-glucan from alga Euglena gracilis, is able to
increase respiratory burst after 30 min in contact with phagocytes, but only at the highest
concentration assayed (10 mg ml -1 ). These results are in agreement with data reported by
Castro et al. (1999), who observed increases of the respiratory burst activity of head
kidney phagocytes of turbot (Psetta maxima) phagocytes and gilthead seabream with
different concentrations of β-glucans obtained from fungus and yeasts. On the other
hand, Castro et al. (2004) found great variations in the stimulative capacities of algal
extracts depending not only on their origin, but on the concentrations used and time of
incubation.
P. cruentum culture has several advantages, such as fast growth and low cost. On
the other hand P. cruentum could be a natural immunostimulant, which is
biocompatible, biodegradable and safe for the environment and human health. For this
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