Presently, most bacterial diseases of eel (Anguilla japonica) are controlled by antibiotics. However, antibiotics not only kill the bacterial pathogens but also kill those bacteria which might be beneficial to eels. In the meantime, application of antibiotics may result in spreading and accumulation of the resistance genes which may in turn lower the efficacy the antibiotics in the future and may threat public health. The recent trend to such problems is to screen non-pathogenic bacteria which are competitive to the pathogenic bacteria in the same environments. The eel pathogen, Edwardsiella tarda, was chosen as the target in this study. Bacterial strains were isolated from different eel ponds and tested for the ability to inhibit the growth of E. tarda. Of 2,412 strains tested, eight of them showed the inhibition capability. The molecular weights of the bioactive ingredients are all smaller than 12,000 daltons indicating they are not protein in nature. One of the strains is Bacillus cereus, four of the strains are Bacillus sphaericus, two of the strains are Bacillus laterosporus, and one of the strains of identified as Pseudomonas areuginosa competed extremely well with E. tarda. These antagonistic bacteria may have the potential of becoming as bio-control agents.Tiger shrimp (Penaeus monodon) is an important agricultural product in Taiwan. The over all production peaked in 1988, since then the outbreak of viral infection has caused the shrimp aquaculture a heavy damage. The current production is merely 1/10 of the peak. Many solutions were proposed to solve the problem, such as: increase the immunity of the shrimp, study pumping of the underground water has caused serious land subsidence in the coastal areas. Therefore, conservation of water is the trend of current aquaculture. In this study, culturable bacteria were isolated from a closed tiger shrimp pond. The taxonomy of the bacteria was based on 16S rDNA sequence phylogeny. Roughly 8 groups (genera) of bacteria were identified, including: Vibrio, Pseudoalteromonas, Porphyrobacter, Flavobacterium, Rhodthermus and three uncertain genera.

Com a crescente preocupação por práticas agrícolas mais sustentáveis, o uso de rizobactérias promotoras de crescimento de plantas (PGPR) tem recebido cada vez mais atenção por sua capacidade em melhorar a performance das plantas assim como aumentar sua resistência contra insetos e patógenos. Neste trabalho foi demonstrado que a inoculação de plantas de trigo com a rizobacteria Azospirillum brasilense reduziu alguns sintomas característicos de plantas infectadas pelo vírus do nanismo amarelo da cevada (BYDV), bem como a população do afídeo vetor, Rhopalosiphum padi, nessas plantas. A redução de alguns sintomas relacionados a doença foi associada à resistência sistêmica induzida, desencadeada pelo aumento nos níveis de ácido jasmônico, fitohormônio amplamente conhecido na indução de resistência por bactérias benéficas contra patógenos. Entretanto, não foi possível elucidar as vias de defesa que auxiliaram na diminuição da população do vetor. Adicionalmente, verificou- se que a inoculação bacteriana alterou os padrões de preferência hospedeira por ápteros não- virulíferos e virulíferos e alados de R. padi. Os dados apresentados nessa tese sugerem o grande potencial que a inoculação com A. brasilense pode ter no manejo do BYDV, influenciando não apenas o vírus, mas todo seu patossistema, uma vez que o crescimento populacional e o comportamento de seu vetor, R. padi, foram afetados pela interação BYDV-trigo-PGPR. / With the increasing concern for agricultural practices more sustainable, the use of plant growth promoting rhizobacteria (PGPR) has been received increasing attention for its ability to improve plant performance and increase plant resistance against insects and pathogens. In this work, it was demonstrated that the inoculation of wheat plants with the rhizobacteria Azospirillum brasilense, reduced some characteristic symptoms of plants infected by the barley yellow dwarf virus (BYDV), as well as the performance of its aphid vector, Rhopalosiphum padi. The reduction in disease severity was related to induced systemic resistance, triggered by the increase in the levels of jasmonic acid, phytohormone widely known to induce resistance by beneficial bacteria against pathogens. However, it was not possible to elucidate the pathways of defense involved in decrease the vector population. In addition, bacterial inoculation was found to affect the host preference of R. padi aptera non-viruliferous and viruliferous and alates. The data presented here suggest the great potential that the inoculation with A. brasilense can be in the management of BYDV, influencing not only the virus but all its pathosystem, considering that the population growth and the behaviour of its vector, R. padi, were affected by BYDV-wheat-PGPR interaction.