lecture8probioticbacteria：講座8益生菌-資料下載頁(yè)
2025-01-12 08:31本頁(yè)面
【正文】 ate the immune systems of animals and render them more resistant to infections by viruses, bacteria, fungi and parasites. ? Immune response varies in animals ? lactic acid bacteria administered orally may induce increased resistance to enteric infections ? problem: only shown with specific cell pounds or dead cells ? good indications, but no proof (5) Improvement of Water Quality ? Proposed as a mode of action as a result of monitoring water quality after addition of probiotics ? usually associated with Bacillus sp. ? Hook: gram + bacteria are better converters of anic matter back to CO2 than gram ? thus: phytoplankton blooms are more easily maintained (interesting research area!) ? monitor: DOC, POC ? so far, hasn’t been demonstrated Rationale for Selecting Probiotics Verschuere et al. (2022) Background Info ? Profound knowledge of culture ? Critical review of available literature ? Characterization of abiotic and biotic environment impacting culture ? Must know relationship between microbiota and host wellunderstood ? Relationship between microbiota and carrying capacity of environment Acquisition of Putative Probiotics ? Are putative probiotics (isolated from host or host environment) better than those from other sources? ? Putatives might be better due to fact they are already adhered to gut wall (., could block pathogen adhesion) ? If a nonpathogenic bacterium exists at high density in typical culture water, it will be welladapted to prevailing conditions and can probably pete efficiently with pathogens for nutrients Screening of Putatives: Invitro antagonism testing ? Candidates are exposed to pathogen in liquid or solid medium ? screened for production of inhibitory pounds (bacteriocins), siderophores, or on petition for nutrients ? must be undertaken with extreme caution: not all media are suitable ? probionts are finicky as to on which medium they produce inhibitory pounds (., marine agar vs. TSB) Evaluation of Pathogenicity ? Probiotics must not be pathogenic to the host anism this must be confirmed prior to acceptance ? host must be challenged under stressed and nonstressed conditions ? usually acplished by adding probiotic to the culture water ? proper way to do this under monoxenic conditions (only the probiont present) ? also look at interaction with other food anisms found simultaneously in culture (., algae) Invivo Evaluations ? Involves introducing candidate species to host cultures and monitoring growth, survival, physiochemical parameters ? means of addition: addition to artificial diet, addition to culture water, bathing, addition via live food ? next step: experimental (allochthonous) infection of host via immersion ? needs longterm evaluation (is the pathogenic effect one of suppression or delay?) Conclusions/Future ? Current status of probiotics in aquaculture is really hazy ? Lack of knowledge on modes of actions is very evident ? more info on petitive processes between bacteria is required ? more info on relationship between bacteria and other microbiota required ? economic value/efficiency, anyone???
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