Slamet Budi Prayitno

Experimental infections of crustaceans with luminous bacteria related to Photobacterium and Vibrio. Effect of salinity and pH on infectiosity

Luminous bacterial shrimp diseases have recently become a major problem in shrimp hatcheries in Indonesia and other Asian countries. Luminous bacteria were isolated from moribund shrimp larvae from hatcheries in Jepara in December 1990. These isolates consisted of two groups which were closely related to Vibrio harveyi and Photobacterium phosphoreum. Pathogenicity tests demonstrated that several strains were pathogenic to Artemia nauplii and Penaeus monodon larvae at concentrations of 104 and 103 cfu/ml respectively. The virulence of the bacteria was related to the age of the larvae, such that 25.28% of zoea, 47.08% of mysis and 51.50% of postlarvae survived 48 h exposure to the pathogen. The bacteria were unable to cause significant mortalities to barnacle and Macrobrachium larvae but were pathogenic to P. indicus larvae indicating that they exhibit a degree of host specificity and that barnacles may be a potential reservoir for these disease-causing bacteria. Most outbreaks of luminous bacterial disease in Indonesia occur during the rainy season. Exposure of luminous bacterial pathogens to low salinities (10,15 ppt) for 12 h before use in immersion challenge experiments with Penaeus monodon larvae resulted in significantly enhanced mortalities (P < 0.05). This may account in part for the seasonality of luminous bacterial disease outbreaks. Exposure of luminous bacteria to acid pH (5.5) significantly reduced their pathogenicity toward penaeid prawn larvae (P < 0.05). These results imply that environmental factors may play a key role in disease outbreaks.

Genetic diversity of the causative agent of ice-ice disease of the seaweed Kappaphycus alvarezii from Karimunjawa island, Indonesia

An essential step in investigating the bacterial role in the occurrence of diseases in Kappaphycus alvarezii is the characterization of bacteria associated with this seaweed. A molecular characterization was conducted on the genetic diversity of the causative agents of ice-ice disease associated with K. alvarezii widely known as the main source of kappa carrageenan. K. alvrezii infected with ice-ice were collected from the Karimunjawa island, North Java Sea, Indonesia. Using Zobell 2216E marine agar medium, nine bacterial species were isolated from the infected seaweed. The molecular characterizations revealed that the isolated bacteria causing ice-ice disease were closely related to the genera of Alteromonas, Bacillus, Pseudomonas, Pseudoalteromonas, Glaciecola, Aurantimonas, and Rhodococcus. In order to identify the symptoms causative organisms, the isolated bacterial species were cultured and were evaluated for their pathogenity. Out of 9 species, only 3 isolates were able to cause the ice-ice symptoms and consisted of Alteromonas macleodii, Pseudoalteromonas issachenkonii and Aurantimonas coralicida. A. macleodii showed the highest pathogenity.

White Shrimp (Litopenaeus vannamei) Culture using Heterotrophic Aquaculture System on Nursery Phase

Heterotrophic aquaculture system is an environmental friendly shrimp culture that has a huge potency to improve yields of Litopenaeus vannamei. Biofloc grown in a heterotrophic aquaculture system that can be used as an alternative feed for shrimp due to its high nutrition. Biofloc contains bacterial protein and polyhydroxybutyrate that are able to enhance growth. Biofloc also contains bacteria that have peptidoglycan and lipopolysaccharide on their cell walls. The aim of the research was to study the effect of heterotrophic aquaculture system on culturing of Litopenaeus vannamei during nursery phase. The experiment was arranged in split plot design in three replicateses. The treatments consisted of two factors namely various densities and different aquaculture systems. The aquaculture systems were autotrophic and heterotrophic aquaculture system, while densities were 1,000, 1,500, and 2,000 PLm-3. The result showed that there was no significant interaction between densities and aquaculture system toward the growth rate, protein efficiency ratio and yield of Litopenaeus vannamei. The heterotrophic aquaculture system was able to increase the yield of Litopenaeus vannamei on nursery phase. However heterotrophic aquaculture system did not significantly affect growth rate and protein efficiency ratio of Litopenaeus vannamei. While, the density significantly affected survival rate and yield of Litopenaeus vannamei.

The Performance of Mangrove Leaf Extract (Sonneratiaalba) in Combating Bacterial Associated with Ice–Ice Disease of Seaweed (Kappaphycusalvarezii)

The outbreaks of ice–ice disease since 1999 at various seaweed culture in Indonesia were still very high with significant losses. Moreover, very scanty of the research on the cause and control methods has been developed. Meanwhile, Mangrove leaf extract (Sonneratiaalba) contained bacteriostatic that might potentially effective to combat a such disease. This research was aimed to demonstrate the performance of mangrove leaf extract to control bacteria causing ice–ice disease. Mangrove leaf (S. alba) was extracted by methanol. Nine bacterial collection from the ice–ice were then in vitro-exposed to mangrove extract at concentration of 2500, 5000 and 10,000 mg/l respectively. Research results demonstrated that mangrove leaf extract at all concentrations tested were able to prevent the growth of 9 bacterial strains associated with ice–ice disease. The diameter of clear zone was between 7.47 and 16.17 mm after 24 hours incubation. Thus, it can be concluded that alkaloid, saponin, tannin, triterpenoid/steroid, and flavonoid in the mangrove leaf at concentration as low as 2500 mg/l was able to prevent the growth of 9 bacterial associated with ice–ice disease.