Training Manual Application of Genetics and Biotechnology in ...
Training Manual Application of Genetics and Biotechnology in ...
Training Manual Application of Genetics and Biotechnology in ...
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survival. It could have been due to the probiotic effect or an effect on the water<br />
quality by degradation <strong>of</strong> organic matter. As regards its effect as a probiotic on the<br />
possible <strong>in</strong>test<strong>in</strong>al transience it br<strong>in</strong>gs about, more studies are required to be camed<br />
out.<br />
Results <strong>of</strong> the experiments <strong>of</strong> Moriarty (1998) suggest the Bacillus spp is<br />
used as a biocontrol agent. The effects could possibly have been due to production <strong>of</strong><br />
antibiotics <strong>in</strong> relation to sporulation or dur<strong>in</strong>g proteolysis <strong>of</strong> the vegetative cells.<br />
The <strong>in</strong>clusion <strong>of</strong> nitrify<strong>in</strong>g bacteria under the term probiotic is rather <strong>in</strong>correct.<br />
This concept is considered as bioremediation which is def<strong>in</strong>ed as "Treatment <strong>of</strong> any<br />
waste by use <strong>of</strong> microbes that break down the undesirable substance". Other<br />
commercial preparations <strong>of</strong> lactic acid bacteria <strong>and</strong> Streptococcus faeciunr have also<br />
been tried <strong>in</strong> aquaculture but there is not much evidence <strong>of</strong> its ability to colonise the<br />
gut. There has been limited success <strong>in</strong> extend<strong>in</strong>g the use <strong>of</strong> probiotics <strong>of</strong> terrestrial<br />
animals to aquaculture. The survival <strong>of</strong> microbes <strong>in</strong> the gastro<strong>in</strong>test<strong>in</strong>al tract <strong>of</strong><br />
aquatic animals is uncerta<strong>in</strong>, therefore there has been a shift <strong>in</strong> the research by<br />
scientists who are now look<strong>in</strong>g for autochthonous stra<strong>in</strong>s resid<strong>in</strong>g <strong>in</strong> the<br />
gastro<strong>in</strong>test<strong>in</strong>al tract adher<strong>in</strong>g to the mucus, as possible c<strong>and</strong>idates.<br />
Antagonism, commonly observed among mar<strong>in</strong>e bacteria may be mediated<br />
by antibiotics, organic acids, hydrogen peroxide <strong>and</strong> siderophores. However, the <strong>in</strong><br />
vitro activity seen, should be extended to <strong>in</strong> vivo studies <strong>in</strong> order to consider it as a<br />
probiotic. Intest<strong>in</strong>al colonization is an important potential to consider <strong>in</strong> a probiotic.<br />
In a study, it was observed that autochthonous <strong>in</strong>test<strong>in</strong>al bacteria adhere specifically<br />
to <strong>in</strong>test<strong>in</strong>al mucus <strong>and</strong> their adherence potential to mucus was found to be stronger<br />
than to control surface bacteria. Yeasts are reported to have a greater ability to adhere<br />
to <strong>in</strong>test<strong>in</strong>e <strong>and</strong> colonise by specific adhesions <strong>and</strong> their application as probionts is<br />
promis<strong>in</strong>g.<br />
In conclusion one can.see the advantages <strong>of</strong> probiotics over other chemicals used<br />
<strong>in</strong> aquaculture. It is to be expected that probiotic-resistant pathogens will emerge. To<br />
avoid this situation, one must take care to ensure that probiotics with diversified<br />
antagonistic properties are used. It is also important to consider the stimulation <strong>of</strong> the<br />
immune system by the probiotic. Molecular approaches to analyze bacterial<br />
communities <strong>in</strong> the gut may help to look at the <strong>in</strong>fluence <strong>of</strong> specific probiotics on the<br />
gastro<strong>in</strong>test<strong>in</strong>al microbiota.