碩士 / 東吳大學 / 微生物學系 / 98 / Laminarin is one kind of β-glucan. Previous studies have been demonstrated that β-glucan can enhance the innate immunity of the crustaceans by binding with β-glucan-binding protein (βGBP) and that treatment with β-glucan would enhance the ability of disease defense and change bacteria flora in the hepatopancreas of Penaeus monodon. In this study, we examined the relationship between the change of culturable bacterial composition and appearance and disappearance of pathogenic bacteria in the hepatopancreas of Macrobrachium rosenbergii fed with laminarin, and evaluated the practicability of specific bacteria as probiotics which appeared by feeding.
Macrobrachium rosenbergii fed with different concentration (0, 20, 30 and 40 μg/prawn) of laminarin (one 1,3 and 1,6-linkage β-glucan) for 15 days was examined; in addition, the mortality and total phenoloxidase activity (POT) of shrimps were detected on days 3, 5, 10 and 15 to decide the suitable dosage of feeding. The dead shrimps were found in the 30 μg-treated group on day 10 which occurred later than those in the other groups on day 5. Lower accumulated mortality (37.5%) and higher phenoloxidase activity were also found in the 30 μg-treated group than those found in other groups in 10 days after feeding. Bacteria in the hepatopancreas of 30-μg-treated group on days 3, 5, 10 and 15 after feeding were isolated and identified by sequencing 16S rDNA. The results showed that, the appearance percentage of pathogen were 17% on day 0, 33% on day 3, 0% on day 5, 10% on day 10 and 60% on day 15 and that bacterial diversity was 1.96、2.14、1.70、2.05 and 0.58, respectively. Furthermore, two species Ralstonia sp. and Lactococcus lactis were found in the 30-μg-treated group on days 5 after feeding, but were detected in neither the other treated groups nor the blank and control groups.
In order to characterize whether the two bacteria is probiotics for prawns, using a known probiotic Lactobacillus plantarum from mammal intestine as the control, the toxicity of three strains to prawns were determined. The results showed that the mortality of prawns challenged by L. plantarum was 87%, that by L. lactis was 12%, and that by Ralstonia sp. was 33%. After the bacterial extracellular fluid from different growth stages were separately co-cultured with three pathogens (Aeromonas hydrophila, A. veronii and Lactococcus garvieae), both extracellular fluid of L. plantarum and L. lactis could inhibit the growth of the two pathogenic Aeromonas spp. and the better effect of inhibition was detected at the late log phase for L. plantarum and the stationary phase for L. lactis on 0.88 mg/ml and 3.03 mg/ml, respectively. The extracellular fluid from Ralstonia sp. could inhibit the growth of all three pathogens and the better effect was detected at the late log phase on 0.076 mg/ml. After prawns were separately fed the three bacteria for 5 days, the survival of prawns was determined by challenge with the pathogenic L. garvieae. It was 14% for control, 29% for the L. lactis-fed group and 43% for the Ralstonia-fed group. The PO activity of bacteria-fed prawns was detected before challenge test. The results showed that the intracellular POS (0.43 U/min/mg) and extracellular POS (0.48 U/min/mg) and POT (2.12 U/min/mg) of the Ralstonia-fed group were not difference from those of control group (0.42 U/min/mg, 0.49 U/min/mg, and 2.02 U/min/mg), but the intracellular POT (4.01 U/min/mg) was higher than that of control group (0.50 U/min/mg). For the L. lactis-fed group, the intracellular POS (0.77 U/min/mg) and the extracellular POS (3.63 U/min/mg) and POT (2.96 U/min/mg) were higher than those of control group (0.42 U/min/mg, 0.50 U/min/mg, and 2.02 U/min/mg), while the extracellular POS (0.36 U/min/mg) was not different from the control group (0.49 U/min/mg).
All results are suggested that 30 μg of larminarin may delay the death of prawns via enhancing the immunity and changing the bacterial flora of hepatopancreas of prawns, which probiotics increase shortly to inhibit the pathogen growth. In addition, results from the characteristics of L. lactis and Ralstonia sp. are speculated that the two strains isolated from larminarin-fed prawns may have the potentiality of being probiotics in prawn industry.
| Identifer | oai:union.ndltd.org:TW/098SCU05381011 |
| Date | January 2010 |
| Creators | Yi-Hsang Peng, 彭怡瑄 |
| Contributors | Hung-Hung Sung, 宋宏紅 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 97 |
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