The impact of pathogen-pathogen and host-pathogen signaling in larviculture of the giant freshwater prawn (Macrobrachium rosenbergii)

Aquaculture is the fastest‐growing food‐producing sector worldwide. The giant freshwater prawn, Macrobrachium rosenbergii, is one of the most important cultured species. However, diseases caused by pathogenic bacteria such as Vibrio spp. constitute a significant obstacle for the further expansion of M. rosenbergii cultivation. Some novel strategies to control diseases have been suggested, and in this thesis, we investigated the impact of host‐pathogen signaling and of quorum sensing, bacterial cell‐to‐cell communication, on the virulence of pathogenic bacteria towards giant freshwater prawn larvae. Vibrio campbellii is one of the major pathogens of aquatic organisms, and virulence gene expression of this bacterium is regulated by a three channel quorum sensing system. In this thesis, first it is shown that this quorum sensing system is required for full virulence of the bacterium towards giant freshwater prawn larvae. Secondly, the quorum sensing‐disrupting compounds cinnamaldehyde, brominated furanone, and brominated thiophenone are shown to increase the survival of giant freshwater prawn larvae when challenged to Vibrio campbellii. Third, quorum sensing signal molecule‐degrading bacteria isolated from microalgae are shown to degrade signal molecules produced by various aquaculture pathogens and to protect giant freshwater prawn larvae from vibriosis. Further, it is shown that catecholamines (stress hormones produced by higher organisms) significantly induce the growth in an iron‐limited environment and the swimming motility of vibrios. Finally, catecholamines are shown to significantly increase the virulence of V. campbellii towards giant freshwater prawn larvae. In conclusion, the results presented in this study showed that pathogen‐pathogen signaling and host‐pathogen signaling play an important role in the virulence of vibrios in giant freshwater prawn larvae. Quorum sensing‐disrupting compounds and quorum sensing signal molecule‐degrading bacteria are promising novel tools to control bacterial disease, and the interference with catecholamine sensing in order to control disease needs further research

KESESUAIAN EKOLOGI BUDIDAYA UDANG VANAME (Litopenaeus vannamei) PADA TAMBAK SEMI INTENSIF DI KECAMATAN GEROKGAK, BALI

Kecamatan Gerokgak menjadi salah satu pusat perikanan budidaya, khususnya budidaya udang vaname. Tujuan dari penelitian ini adalah untuk menentukan parameter kesesuaian ekologi pada kegiatan budidaya udang vaname di Kecamatan Gerokgak, Bali. Penelitian dilaksanakan di enam petak tambak yang berada di tiga desa, yaitu Desa Gerokgak, Patas, dan Sanggalangit mulai bulan Oktober 2021 hingga Januari 2022. Parameter ekologi yang diamati adalah suhu, pH, salinitas, oksigen terlarut, kecerahan, alkalinitas, amonia, bahan organik total, nitrat, nitrit, fosfat, kelimpahan plankton, bakteri heterotrofik, dan Vibrio. Data dianalisis menggunakan matriks kesesuaian dan dihitung indeks kesesuaiannya. Hasil penelitian menunjukkan suhu pagi sebesar 24,0-26,8°C; suhu sore 27,0-30,4°C; pH 7,3-8,1; salinitas 6-33 ppt; oksigen terlarut 7,7-7,9 mg L-1; kecerahan 38,5-44,6 cm; alkalinitas 205,9-212,6 mg L-1; amonia 0,28-0,48 mg L-1; bahan organik total 30-33 mg L-1; nitrat 0,2-0,3 mg L-1; nitrit 0,01-0,02 mg L-1; fosfat 0,53-0,66 mg L-1; kelimpahan plankton 117.909-200.764 ind L-1; bakteri heterotrofik 1,8x105-2,4x105 CFU mL-1; dan Vibrio sebesar 2.776-3.620 CFU mL-1. Semua tambak menunjukkan tingkat sangat sesuai untuk budidaya udang vaname. Nilai indeks kesesuaian tertinggi terdapat pada petak Desa Sanggalangit 2 (95,9%), diikuti oleh Desa Sanggalangit 1 dan Desa Patas 1 (93,8%), sementara nilai Desa Patas 2, Desa Gerokgak 1dan Desa Gerokgak 2 mendapatkan nilai indeks kesesuaian yang terendah (91,8%). Penelitian ini menyimpulkan bahwa seluruh petak yang diamati termasuk dalam tingkat kesesuaian ekologi Sangat Sesuai untuk budidaya udang vaname.Gerokgak area is the primary coastal aquaculture center in North Bali in which whiteleg shrimp farming has grown rapidly in the past decade. This study aimed to determine the ecological suitability of semi intensive whiteleg shrimp farming in the area. The research was carried out in six different ponds in three villages (Gerokgak, Patas, and Sanggalangit Villages) from October 2021 to January 2022. The evaluation parameters consist of temperature, pH, salinity, dissolved oxygen, transparency, alkalinity, ammonia, total organic matter, nitrate, nitrite, phosphate, plankton abundance, heterotroph bacteria count, and Vibrio count. The collected data were arranged into suitability matrix from which the suitability indexes were calculated. The morning temperature was 24.0-26.8°C; afternoon temperature 27.0-30.4°C; pH 7.3-8.1; salinity 26-33 ppt; dissolved oxygen 7.7-7.9 mg L-1; brightness 38.5-44.6 cm; alkalinity 205.9-212.6 mg L-1; ammonia 0.28-0.48 mg L-1; total organic matter 30-33 mg L-1; nitrate 0.2-0.3 mg L-1; nitrite 0.01-0.02 mg L-1; phosphate 0.53-0.66 mg L-1; plankton abundance 117,909-200,764 ind L-1; heterotrophic bacteria 1.8x105-2.4x105 CFU mL-1; and Vibrio 2,776–3,620 CFU mL-1. The highest suitability index value was scored by Sanggalangit Village pond 2 (95.9%), followed by Sanggalangit Village pond 1 and Patas Village pond 1 (93.8%), while Patas Village pond 2, Gerokgak Village pond 1, and Gerokgak Village pond 2 had the lowest suitability index (91.8%). This study concludes that all observed ponds are categorized as highly ecologically suitable for whiteleg shrimp culture

The influence of biofloc system on Vibrio composition, the growth and the gut microvilli performance of the Pacific white shrimp Penaeus vannamei

Biofloc technology has been shown to have a positive impact on shrimp culture by controlling pathogenic Vibrio. This study aimed to analyze the effect of biofloc on the Vibrio composition in water and shrimp gut, as well as the growth performance and microvilli of Pacific white shrimp (Penaeus vannamei). Shrimp post-larvae measuring 0.66 ± 0.02 g were reared in a glass aquarium (working volume 22 L) of 6 units with a density of 150 shrimp m-3 for 28 days. The treatments included rearing in the biofloc system with C/N ratio 10, and without a biofloc system as a control. The results showed that Vibrio was highly prevalent in the control gut (4.13%) and biofloc water (3.77%), but only a few were found in the control water (0.16%) and biofloc-treated gut (0.11%). V. hepatarius (1.10%) and V. nereis (1.06%) were found to dominate the Vibrio bacterial community in the biofloc system maintenance media, while Vibrio sp. Hep-1b-8 (2.26%) and V. parahaemolyticus (0.80%) known as a pathogenic bacteria dominated the control shrimp gut. The biofloc system significantly increased the digestive enzyme activity, growth performance, and microvilli length in the shrimp gut. In conclusion, the application of a biofloc system in shrimp culture can affect the composition and abundance of bacterial communities in both the culture environment and the shrimp gut, and improve growth performance with higher digestive enzyme activity and longer microvilli in the gut.   Keywords: biocontrol, biofloc, microbiota, shrimp, Vibrio   ABSTRAK   Teknologi bioflok menunjukkan dampak positif pada kegiatan budidaya udang vaname dengan mengendalikan bakteri patogen salah satunya Vibrio. Penelitian ini bertujuan untuk menganalisis efek bioflok terhadap komposisi Vibrio pada  air dan usus udang, serta kinerja pertumbuhan dan mikrovili udang vaname (Penaeus vanamei). Udang post-larva berukuran 0.66 ± 0.02 g dipelihara pada akuarium kaca (volume air 22 L) sebanyak 6 unit dengan kepadatan 150 ekor m-3 selama 28 hari. Perlakuan meliputi pemeliharaan udang pada sistem bioflok dengan rasio C/N 10, dan tanpa sistem bioflok sebagai perlakuan kontrol. Hasil pengamatan menunjukkan kelimpahan Vibrio yang cukup tinggi pada usus perlakuan kontrol (4.13%) dan air perlakuan bioflok (3.77%), tetapi sangat sedikit ditemukan pada air perlakuan kontrol dan usus perlakuan bioflok. Selanjutnya, V. hepatarius (2.26%) dan V. nereis (1.06%) terdeteksi mendominasi komunitas bakteri Vibrio di media pemeliharaan pada sistem bioflok, sedangkan Vibrio sp. Hep-1b-8 (2.26%) dan V. parahaemolyticus (0.80%) mendominasi usus udang vaname pada perlakuan kontrol. Sistem bioflok juga mampu meningkatkan aktivitas enzim pencernaan, performa pertumbuhan, dan panjang mikrovili usus secara signifikan (P < 0.05). Kesimpulan dari penelitian ini adalah penerapan sistem bioflok pada budidaya udang vaname mampu memengaruhi komposisi dan kelimpahan komunitas bakteri Vibrio pada lingkungan budidaya maupun pada usus udang, serta meningkatkan performa pertumbuhan dengan aktivitas enzim pencernaan yang lebih baik dan mikrovilli usus yang lebih panjang.   Kata kunci: bioflok, biokontrol, microbiota, udang vaname, Vibri

Penghambatan Faktor Virulensi Vibrio parahaemolyticus Menggunakan Isolat Bakteri dari Saluran Pencernaan Ikan Kerapu

Ikan kerapu adalah komoditas perikanan yang bernilai ekonomis tinggi pada pasar domestik dan internasional. Akan tetapi, dalam budidaya ikan kerapu masih sering ditemukan kasus penyakit vibrosis yang berdampak terhadap kerugian ekonomi akibat kematian yang ditimbulkan. Penyakit ini disebabkan salah satunya oleh bakteri Vibrio parahaemolyticus yang faktor virulensinya diregulasi oleh mekanisme kuorum sensing (QS). Pencegahan penyakit bakteri selama ini sering dilakukan dengan menggunakan antibiotik yang berisiko munculnya bakteri resisten antibiotik. Salah satu upaya untuk menghindari hal tersebut adalah dengan menghambat sistem QS menggunakan bakteri pendegradasi molekul sinyal N-acyl homoserine lactone (AHL). Pada penelitian ini dilakukan isolasi kandidat bakteri pendegradasi AHL pada media menggunakan AHL komersial sebagai sumber N tunggal dan juga melakukan isolasi bakteri V. parahaemolyticus pada media Thiosulfate-Citrate-BileSalts-Sucrose Agar dari saluran pencernaan ikan kerapu. Pengaruh penambahan isolat kandidat pendegradasi AHL terhadap tiga faktor virulensi V. parahaemolyticus yaitu motilitas, produksi kaseinase dan hemolisa diuji dengan mengkultur V. parahaemolyticus dengan dan tanpa penambahan isolat pendegradasi AHL. Hasil penelitian menunjukkan bahwa 2 isolat kandidat pendegradasi AHL yaitu SNA02 dan SNA03 mampu menurunkan ketiga faktor virulensi yang diuji tersebut. Hal ini mengindikasikan bahwa isolat SNA02 dan SNA03 berpotensi sebagai kandidat bakteri untuk mencegah penyakit vibriosis. Hasil ini diharapkan dapat membantu pembudidaya ikan kerapu dalam mengendalikan patogenitas bakteri V. parahaemolyticus

The Vibrio campbellii quorum sensing signals have a different impact on virulence of the bacterium towards different crustacean hosts.

Pathogenic bacteria communicate with small signal molecules in a process called quorum sensing, and they often use different signal molecules to regulate virulence gene expression. Vibrio campbellii, one of the major pathogens of aquatic organisms, regulates virulence gene expression by a three channel quorum sensing system. Here we show that although they use a common signal transduction cascade, the signal molecules have a different impact on the virulence of the bacterium towards different hosts, i.e. the brine shrimp Artemia franciscana and the commercially important giant freshwater prawn Macrobrachium rosenbergii. These results suggest that the use of multiple types of signal molecules to regulate virulence gene expression is one of the features that allow bacteria to infect different hosts. Our findings emphasize that it is highly important to study the efficacy of quorum sensing inhibitors as novel biocontrol agents under conditions that are as close as possible to the clinical situation

The expression patterns of HSP70 and HSP90 genes of abalone (

The packaging of abalone (H. squamata) (39.65 ± 0.24 mm TL) for long-term transportation (>8 hours) requires the addition of substances that provide an anesthetic effect so that it could reduce stress and maintain survival rate post transportation without having to repack. The objective was to investigate the expression pattern of HSP70 and HSP90 genes of abalone during transport with the addition of 2-phenoxyethanol. Abalone was packed using a styrofoam box with dimensions (42.5 x 75.5 x 27.5 cm3), containing 2 pcs of 10L Polyethylene (PE) plastic bags. The plastic bag consisted of 2 pcs of 25cm, 4-inch Polyvinyl Chloride (PVC) pipe for abalone attached. Both ends line enclosed with screen net and tied with rubber bands. Abalone density was 50 heads/pipe. Transportation tests were carried out using a dry system and wet system with and without the addition of 2-phenoxyethanol (PK, KK). Data analysis was done by paired sample ttest and ANOVA with a 95% confidence interval. The results showed that the best abalone survival (85%) was obtained in wet transport + 2-phenoxyethanol (PB) (p <0.05) within 24 hours of transportation