Papel de las actividades superóxido dismutasa y catalasa en la ...
Papel de las actividades superóxido dismutasa y catalasa en la ...
Papel de las actividades superóxido dismutasa y catalasa en la ...
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RESULTS AND DISCUSSION<br />
pres<strong>en</strong>t work we have observed that the non virul<strong>en</strong>t strain, EPOY-8803-II, shows<br />
activity levels simi<strong>la</strong>r to the virul<strong>en</strong>t strain.<br />
As <strong>de</strong>scribed before, information concerning mechanisms involved in the invasion<br />
and survival of P. damse<strong>la</strong>e subsp. piscicida insi<strong>de</strong> the host is scarce and results<br />
regarding interaction of this pathog<strong>en</strong> with phagocytes have be<strong>en</strong> contradictory. For this<br />
reason, pathog<strong>en</strong> survival after contact with sole phagocytes was evaluated. Results<br />
inclu<strong>de</strong>d in article 1.2. (Article section) show that P. damse<strong>la</strong>e subsp. piscicida is able to<br />
survive insi<strong>de</strong> sole phagocytes at least for five hours, survival rates being higher for the<br />
virul<strong>en</strong>t strain (62%) than the non virul<strong>en</strong>t strain (19%). Also, higher survival rates were<br />
observed in cultures with higher cata<strong><strong>la</strong>s</strong>e activity. These results suggest that bacterial<br />
inactivation could be due to the accumu<strong>la</strong>tion of hydrog<strong>en</strong> peroxi<strong>de</strong>, the precursor of<br />
hydroxyl radicals, after <strong>de</strong>composition of superoxi<strong>de</strong> radicals by bacterial superoxi<strong>de</strong><br />
dismutase. Both virul<strong>en</strong>t and non-virul<strong>en</strong>t strains assayed by Barnes et al. (1999a)<br />
showed high susceptibility to cell-free g<strong>en</strong>erated superoxi<strong>de</strong> radicals, in contrast, we<br />
have observed that a non-virul<strong>en</strong>t strain, EPOY-8803-II, is significantly more<br />
susceptible to killing by sole phagocytes than a virul<strong>en</strong>t strain (Lg h41/01 ). Besi<strong>de</strong>s the<br />
lower cata<strong><strong>la</strong>s</strong>e activity pres<strong>en</strong>t in the non-virul<strong>en</strong>t strain, the <strong>la</strong>ck of a capsule in cells of<br />
EPOY-8803-II could contribute to the high inactivation rates observed. Thus, the capsule<br />
could protect bacterial cells from oxidative radicals or ev<strong>en</strong> prev<strong>en</strong>t activation of<br />
phagocytes (Miller and Britigan, 1997; Arijo et al., 1998).<br />
Finally, the important role of iron in microbial infections has be<strong>en</strong> pointed out by<br />
several authors (Miller and Britigan, 1997; Weinberg, 2000). P. damse<strong>la</strong>e subsp.<br />
piscicida is more susceptible to killing by sole phagocytes wh<strong>en</strong> bacterial cells have<br />
be<strong>en</strong> cultured un<strong>de</strong>r iron-<strong>de</strong>pleted conditions. Bacteria require iron for growth and<br />
replication and synthesize SOD and cata<strong><strong>la</strong>s</strong>e to <strong>de</strong>al with oxidizing anions. P. damse<strong>la</strong>e<br />
subsp. piscicida posses a high-affinity iron uptake system, a sy<strong>de</strong>rophore (Magariños et<br />
al. 1994; Naka et al., 2005). However, <strong>de</strong>spite its ability to obtain iron from high-affinity<br />
systems, several authors have reported that cells grown un<strong>de</strong>r iron-limited conditions<br />
have reduced amounts of capsu<strong>la</strong>r material covering the cells (do Vale et al., 2001).<br />
These cells with reduced capsule would be more susceptible to phagocytosis and<br />
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