Ecological theory as a foundation to control pathogenic invasion in aquaculture

Detrimental host-pathogen interactions are a normal phenomenon in aquaculture animal production, and have been counteracted by prophylactic use of antibiotics. Especially, the youngest life stages of cultivated aquatic animals are susceptible to pathogen invasion, resulting in disease and mortality. To establish a more sustainable aquatic food production, there is a need for new microbial management strategies that focus on 'join them' and not the traditional 'beat them' approaches. We argue that ecological theory could serve as a foundation for developing sustainable microbial management methods that prevent pathogenic disease in larviculture. Management of the water microbiota in aquaculture systems according to ecological selection principles has been shown to decrease opportunistic pathogen pressure and to result in an improved performance of the cultured animals. We hypothesize that manipulation of the biodiversity of the gut microbiota can increase the host's resistance against pathogenic invasion and infection. However, substantial barriers need to be overcome before active management of the intestinal microbiota can effectively be applied in larviculture

Increased salinity improves the thermotolerance of mesophilic nitrification

Nitrification is a well-studied and established process to treat ammonia in wastewater. Although thermophilic nitrification could avoid cooling costs for the treatment of warm wastewaters, applications above 40 A degrees C remain a significant challenge. This study tested the effect of salinity on the thermotolerance of mesophilic nitrifying sludge (34 A degrees C). In batch tests, 5 g NaCl L-1 increased the activity of aerobic ammonia-oxidizing bacteria (AerAOB) by 20-21 % at 40 and 45 A degrees C. For nitrite-oxidizing bacteria (NOB), the activity remained unaltered at 40 A degrees C, yet decreased by 83 % at 45 A degrees C. In a subsequent long-term continuous reactor test, temperature was increased from 34 to 40, 42.5, 45, 47.5 and 50 A degrees C. The AerAOB activity showed 65 and 37 % higher immediate resilience in the salt reactor (7.5 g NaCl L-1) for the first two temperature transitions and lost activity from 45 A degrees C onwards. NOB activity, in contrast to the batch tests, was 37 and 21 % more resilient in the salt reactor for the first two transitions, while no difference was observed for the third temperature transition. The control reactor lost NOB activity at 47.5 A degrees C, while the salt reactor only lost activity at 50 A degrees C. Overall, this study demonstrates salt amendment as a tool for a more efficient temperature transition for mesophilic sludge (34 A degrees C) and eventually higher nitrification temperatures

Early mortality syndrome outbreaks : a microbial management issue in shrimp farming?

A recent disease of farmed Penaeid shrimp, commonly referred to as ‘‘early mortality syndrome’ ’ (EMS) or more technically known as ‘‘acute hepatopan-creatic necrosis disease’ ’ (AHPND), was first reported in southern China in 2010 and subsequently in Vietnam, Thailand, and Malaysia [1]. The EMS/AHPND disease typically affects shrimp postlarvae within 20–30 days after stocking and frequently causes up to 100 % mortality. The Global Aquaculture Alliance [2] has estimated that losses to the Asian shrimp culture sector amount to USD 1 billion. The causative agent of EMS/AHPND ha

The SAWA corpus: a parallel corpus English-Swahili

Research in data-driven methods for Machine Translation has greatly benefited from the increasing availability of parallel corpora. Processing the same text in two different languages yields useful information on how words and phrases are translated from a source language into a target language. To investigate this, a parallel corpus is typically aligned by linking linguistic tokens in the source language to the corresponding units in the target language. An aligned parallel corpus therefore facilitates the automatic development of a machine translation system and can also bootstrap annotation through projection. In this paper, we describe data collection and annotation efforts and preliminary experimental results with a parallel corpus English- Swahili.

Immune stimulation in European sea bass (Dicentrarchus labrax) larvae by administration of Poly-ß-hydroxybutyrate (PHB)

Global aquaculture production is growing rapidly, however, the industry is facing great challenges such as high mortality rates during early life stages. The lack of a fully mature immune system makes larvae highly sensitive to infectious diseases. One of the most common pathogenic bacteria in larviculture is Vibrio anguillarum causing worldwide severe economic losses. Due to the development of antibiotic resistances, the establishment of alternative methods to prevent and control diseases, ensure efficient growth and reach maximal survival rates is mandatory to optimize aquaculture productivity. A promising solution might be the early activation of the immature immune system of fish larvae by administration of immunostimulants as nutritional supplements. In our study we assessed the potential immunomodulatory effect of poly-ß-hydroxybutyrate (PHB) in European sea bass (Dicentrarchus labrax) larvae. PHB is a bacterial energy storage compound which may have a potential application as an immunostimulant in fish culture. In our experiment we used rotifers as live carriers to feed PHB-accumulating bacteria (Alcaligenes eutrophus) to first-feeding European sea bass larvae over a period of 14 days. To estimate the immediate impact of PHB, larval mortality rates were monitored daily during the course of the experiment. In order to assess the disease resistance of the larvae, survival rates after bath challenge with Vibrio anguillarum after 3 and 14 days of PHB treatment and 7 days post PHB treatment were monitored. Furthermore, we determined gene expression profiles for immune genes as well as metabolism- and stress-related genes. Results will be discussed in respect to the use of PHB in fish hatcheries and its effect on the immune system of first feeding sea bass

Does poly-ß-hydroxybutyrate stimulate the immune system of European sea bass larvae?

Introduction Various probiotics and immunostimulants have been shown to enhance the immune response and alter the disease resistance of aquaculture organisms. The bacterial energy storage compound poly-ß-hydroxybutyrate (PHB) for example improves resistance against pathogenic infections in shrimp (Laranja et al., 2014) and exhibits a controlling effect on the gut microbiota of juvenile sea bass which may result in the stimulation of immune functions (De Schryver et al., 2011). These properties might be of special importance for culturing early life stages since their immune system is not yet fully developed. Therefore, we assessed the potential immunostimulating effect of PHB in European sea bass (Dicentrarchus labrax) larvae in our study. Materials and methods We used rotifers as live carriers to feed PHB-accumulating bacteria (Alcaligenes eutrophus) to first-feeding larvae over a period of 14 days. Bacteria with a low (2.5%) and a high (75%) PHB content were used, respectively. Apart from the dose effect, we wanted to determine to which extend the point in time of the PHB administration matters. Therefore, PHB was added (in some experimental groups) directly to the water from the moment of mouth opening onwards. This led to the following experimental groups: 1) early and 2) later stimulation with a low PHB level, 3) early and 4) later stimulation with a high PHB level and 5) a control without any PHB. To estimate the immediate impact of PHB, larval mortality rates were monitored daily over the course of the experiment. Furthermore, larvae were sampled the first time after being fed for 3 days with PHB encapsulated in rotifers (and 5 days of PHB water treatment) and the second time after 14 days PHB via rotifers (and 16 days of PHB water treatment), respectively. Results and discussion Larval mortality rates were found to be the highest in the control group. During both sampling points larvae were slightly smaller and weighed less in the control group. The analysis of the gene expression profiles revealed that only certain immune genes such as cytokines (Interleukin-1ß, Interleukin 8 and TNFα) were affected by the PHB treatment. The data indicate that the application of PHB can provide a beneficial effect to sea bass larviculture in terms of higher survival rates. But further studies are required to verify the impact on the developing immune system of the larvae

Virulence-inhibitory activity of the degradation product 3-hydroxybutyrate explains the protective effect of poly-β-hydroxybutyrate against the major aquaculture pathogen Vibrio campbellii

The bacterial storage compound poly-beta-hydroxybutyrate, a polymer of the short-chain fatty acid 3-hydroxybutyrate, has been reported to protect various aquatic animals from bacterial disease. In order to obtain a better mechanistic insight, we aimed to (1) investigate whether 3-hydroxybutyrate is released from poly-beta-hydroxybutyrate within sterile brine shrimp larvae, (2) determine the impact of 3-hydroxybutyrate on the virulence of Vibrio campbellii to brine shrimp larvae and on its cell density in the shrimp, and (3) determine the impact of this compound on virulence factor production in the pathogen. We detected 3-hydroxybutyrate in poly-beta-hydroxybutyrate-fed brine shrimp, resulting in 24 mM 3-hydroxybutyrate in the intestinal tract of shrimp reared in the presence of 1000 mg l(-1) poly-beta-hydroxybutyrate. We further demonstrate that this concentration of 3-hydroxybutyrate does not affect the growth of V. campbellii, whereas it decreases the production of different virulence factors, including hemolysin, phospholipase and protease activities, and swimming motility. We hypothesize that by affecting all these virulence factors at once, 3-hydroxybutyrate (and thus also poly-beta-hydroxybutyrate) can exert a significant impact on the virulence of V. campbellii. This hypothesis was confirmed in a challenge test showing that 3-hydroxybutyrate protected gnotobiotic brine shrimp from pathogenic V. campbellii, without affecting the number of host-associated vibrios

Probing the protective mechanism of poly-β-hydroxybutyrate against vibriosis by using gnotobiotic Artemia franciscana and Vibrio campbellii as host-pathogen model

The compound poly-beta-hydroxybutyrate (PHB), a polymer of the short chain fatty acid beta-hydroxybutyrate, was shown to protect experimental animals against a variety of bacterial diseases, (including vibriosis in farmed aquatic animals), albeit through undefined mechanisms. Here we aimed at unraveling the underlying mechanism behind the protective effect of PHB against bacterial disease using gnotobiotically-cultured brine shrimp Artemia franciscana and pathogenic Vibrio campbellii as host-pathogen model. The gnotobiotic model system is crucial for such studies because it eliminates any possible microbial interference (naturally present in any type of aquatic environment) in these mechanistic studies and furthermore facilitates the interpretation of the results in terms of a cause effect relationship. We showed clear evidences indicating that PHB conferred protection to Artemia host against V. campbellii by a mechanism of inducing heat shock protein (Hsp) 70. Additionally, our results also showed that this salutary effect of PHB was associated with the generation of protective innate immune responses, especially the prophenoloxidase and transglutaminase immune systems - phenomena possibly mediated by PHB-induced Hsp70. From overall results, we conclude that PHB induces Hsp70 and this induced Hsp70 might contribute in part to the protection of Artemia against pathogenic V. campbellii

Selective Manipulation of the Gut Microbiota Improves Immune Status in Vertebrates

All animals develop in association with complex microbial communities. It is now well established that commensal microbiota is essential for the correct functionality of each organ in the host. Particularly, the commensal gastro-intestinal microbiota (CGIM) is a key factor for development, immunity and nutrient conversion, rendering them bio-available for various uses. Thus, nutritional inputs generate a positive loop in maintaining host health and are essential in shaping the composition of the CGIM communities. Probiotics, which are live exogenous microorganisms, selectively provided to the host, are a promising concept for manipulating the microbiota and thus for increasing the host health status. Nevertheless, most mechanisms induced by probiotics to fortify the immune system are still a matter of debate. Alternatively, prebiotics, which are non-digestible food ingredients, can favor the growth of specific target groups of CGIM. Several metabolites are produced by the CGIM, one of the most important are the short-chain fatty acids (SCFAs), which emerge from the fermentation of complex carbohydrates. SCFAs have been recognized as key players in triggering beneficial effects elicited by simple diffusion and by specific receptors present thus far only in epithelial cells of higher vertebrates at different GI locations. However, both strategies have shown to provide resistance against pathogens during periods of high stress. In fish, knowledge about the action of pro- and prebiotics and SCFAs is still limited. Thus, in this review, we briefly summarize the mechanisms described on this topic for higher vertebrates and discuss why many of them may operate in the fish gut representing a model for different mucosal tissues