Complete genome sequence of VpKK5, a novel vibrio parahaemolyticus lytic siphophage

This paper describes the complete sequence of a novel lytic marine siphophage, VpKK5, that is specific to Vibrio parahemolyticus

Effects of environmental conditions and nutrients on the occurrence and distribution of potential harmful phytoplankton in mesotrophic water

Marudu Bay, north coast of Sabah is characterized with mesotrophic water body and typical environmental parameters throughout the year. The current study was undertaken to evaluate the effect of environmental parameters and nutrients in mesotrophic water on the occurrence and distribution of potentially harmful phytoplankton species. The samplings were conducted over a period of thirteen months, covering southwest monsoon (SWM), inter-monsoon (IM), and northeast monsoon (NEM), at ten stations throughout the bay. Physical parameters (temperature, salinity, pH, dissolved oxygen, current speed and secchi depth), biological parameters (cell densities of phytoplankton) and chemical parameters (phosphate, nitrate, silicate and ammonia) were examined. The results indicated at least eight potentially harmful phytoplankton species (Dinophysis caudata, D. miles, Ceratium furca, C. fursus, Prorocentrum micans, P. sigmoides, P. triestinum and Pseudo-nitzschia sp.) were detected in north coast of Sabah. However, the potentially harmful phytoplankton species contributed only about 1.3% of the total phytoplankton community. Under nutrient deprivation conditions, the potentially harmful phytoplankton species distribution was mainly influenced by the ability to utilize other nitrogen sources, cell mobility and toleration to low nutrients environments

Dredging-induced shell damages to hard clam (Meretrix meretrix): a Malaysian case study

The hard clam (Meretrix meretrix) is a popular edible shellfish in South and Southeast Asia, being heavily exploited by hand dredging in Marudu Bay, Malaysia. The current study was performed to evaluate the shell damages caused by this artisanal dredging gear. Samplings were conducted in triplicates at two sites using both hand dredging and hand collecting (control) sampling methods. The shell length and total weight, damage areas and breakage patterns of each clam were recorded. A questionnaire survey was conducted with local bivalve harvesters to gather information on the fishing pressure in Marudu Bay. Results revealed that the efficiency (fishing yield) of hand dredging gear was three times higher than hand collecting. However, hand dredging gear causes lethal shell damages to small hard clams (<3cm in shell length). Hard clam harvesting is the main occupation of most fishermen in Kg. Popok, but most of them do not comply with the minimum harvesting size established by the fishery department. Moreover, most of the stakeholders are not aware of the negative impacts of hand dredging to the sustainability of the hard clam fishery in Marudu Bay. Therefore, organizing more awareness programs combined with introducing community-based fishery management are highly recommended to promote the sustainability of this artisanal fishery

Genome characterization of a novel vibriophage VpKK5 (Siphoviridae) specific to fish pathogenic strain of Vibrio parahaemolyticus

Vibrio parahaemolyticus has long been known pathogenic to shrimp but only recently it is also reported pathogenic to tropical cultured marine finfish. Traditionally, bacterial diseases in aquaculture are often treated using synthetic antibiotics but concern due to side effects of these chemicals is elevating hence, new control strategies which are both environmental and consumer friendly, are urgently needed. One promising control strategy is the bacteriophage therapy. In this study, we report the isolation and characterization of a novel vibriophage (VpKK5), belonging to the family Siphoviridae that was specific and capable of complete lysing the fish pathogenic strain of V. parahaemolyticus. The VpKK5 exhibited short eclipse and latent periods of 24 and 36 min, respectively, but with a large burst size of 180 pfu/cell. The genome analysis revealed that the VpKK5 is a novel bacteriophage with the estimated genome size of 56,637 bp and has 53.1% G + C content. The vibriophage has about 80 predicted open reading frames consisted of 37 complete coding sequences which did not match to any protein databases. The analysis also found no lysogeny and virulence genes in the genome of VpKK5. With such genome features, we suspected the vibriophage is novel and could be explored for phage therapy against fish pathogenic strains of V. parahaemolyticus in the near future

Developing vaccine against Vibriosis in marine fish

One of the major causes of economic loss in aquaculture of marine fish is the bacterial infection. A number of bacterial pathogens which include Vibrio sp., Streptococcus sp. and Photobaderium sp. have been reported to affect aquaculture fish in Sabah. However, no vaccines for combating these bacterial pathogens are currently available. The present study was conducted with the aims to develop the vaccine against one of these bacterial pathogens. The first part of this study was the identification of bacterial pathogens which are associated with diseased fish collected from aquaculture farms around Sabah. In addition to isolation, identification and characterization, pathogenicity of each bacterial strain was also determined. The finding from the study was taken as the basis for vaccine development. In this study, Vibrio halVeyi was found to be highly virulent to many species of cultured fish. Subsequently, the virulent strain of V. halVeyi was killed using formalin and served as bacterin. The ability of the bacterin to induce immune response was first tested in several fish species including freshwater and seawater fish species. The immune response was evaluated using agglutination test. The result showed that all the fish administrated with the bacterin developed antibody against the live antigen. The bacterin was further tested on Asian sea bass using two different delivery methods. The two methods included injection and hyperosmotic-treatment. The fish specimens were divided into three groups namely the non-booster, one time booster and two times booster. Next, the fish in every group was challenged using the bacterial pathogen through intraperitoneal injection. Among the methods of delivery, the injection with adjuvant provided the best protection, whereas the immersion with hyperosmotic-pretreatment (HI) resulted in no protection when tested at high lethal dosage (LDlOO). Both injection methods; adjuvant and non-adjuvant, provided relatively strong protection when challenged with LD60 with RPS value of more than 80%. V. harveyi bacterin was found useful for vaccine preparation as it has effectively prevented vibriosis in Asian sea bass. The finding also showed that vaccination through injection yielded better protection than immersion. Apart from positive outcome of the vaccine trials, vaccinated fish were found exhibiting other clinical signs of bacterial infection. Further analysis revealed the presence of another bacterial pathogen, Photobaderium damse/ae that complicated the result of vaccination trail against vibriosis. The second part of the study was the investigation of possible use of crude extract from plants as the alternative treatment for bacterial diseases. The result of the study revealed several commonly grown plants in Sabah including the Piper bette, Phy/anthus niruri and Syzygium aromaticum exhibited antibacterial properties against many aquaculture bacterial pathogens including the V. harveyi and Photobaderium damse/ae. The antibacterial properties of these plants were also found photosensitive. Besides vaccination, the extracts from these plants may be useful for alternative remedy of bacterial diseases in aquaculture with minimal environmental effects

Key selections for microalgae, the indispensable live feed in bivalve hatchery: a brief review

In the current study, bivalve primarily consumed microalgae were addressed in all their developmental stages. Microalgae, an absolute nutrient source of essential phytonutrients and biologically active compounds, are vital for bivalve growth, health and reproduction. However, in natural habitat, its feeding preferences are not limited to only microalgae, but also include bacterioplankton, microzooplankton, detritus, protist as well as nonnutritive and dissolved organic materials. In contrast, bivalve feeding under controlled hatchery conditions relies on selective microalgae species for broodstock conditioning, larval and post-larval rearing. These activities mainly targeted the high production of seed, also known as spat which depends on the quality and quantity of the microalgae. Thus, thorough preparation and selection of microalgae are critical for the success of hatchery operations. This paper provides a brief overview of the current literature and understanding of microalgae selection criteria as live feed in bivalve hatchery

Antiparasitic effect of formalin, trichlorfon, hydrogen peroxide, and copper sulfate on the parasitic isopod Caecognathia coralliophila

Caecognathia coralliophila is known as a pathogenic ectoparasite infecting tiger grouper Epinephelus fuscoguttatus in a hatchery in Sabah, Malaysia. The effects of copper sulfate, formalin, trichlorfon, and hydrogen peroxide on the survival of C. coralliophila larvae were tested in vitro. The larvae were exposed to different concentrations of each chemical for 10, 20, 30, 60 min, or 24 h. Trichlorfon was found to be the most effective, killing the parasites within 24 h at 0.2 ppm. Consequently, the toxicity of trichlorfon to tiger grouper was tested. Fish were exposed to trichlorfon at 0.2 ppm for 24 h or 3.2 ppm for 60 min. No fish died in the experiment. Thus, our data suggest that trichlorfon is effective for treating C. coralliophilainfection in E. fuscoguttatus

Isolation, Identification and Preliminary Characterization of Candidate Probiotic Bacteria from the Intestine of Domesticated Goldfish (Carassius auratus)

Aquaculture faces challenges from the emergence of many different diseases. For many years, these diseases, especially those caused by bacterial pathogens, were often treated using antibiotics, but due to rampant use of these drugs, many antibiotic-resistant pathogens have emerged. Besides market rejection, aquaculture products with high amounts of antibiotic traces can, in one way or another, harm consumers, and this has become a serious issue pertaining to food safety. In recent years, research on the use of probiotics has shown them not only to control fish diseases but also improve growth performance of farmed fish. Therefore, this study was undertaken to screen for bacteria with probiotic properties from the intestine of domesticated goldfish (Carassius auratus). A total of 169 bacterial isolates were tested for antagonistic properties towards selected fish bacterial pathogens using the disc diffusion method. Five bacterial strains with high antagonistic activity were selected for identification and evaluation of their probiotic capability against Streptococcus agalactiae, Aeromonas caviae, Aeromonas hydrophila, Aeromonas salmonicida, Vibrio harveyi, Vibrio parahaemolyticus, Vibrio alginolyticus and Photobacterium damselae. The bacterial strains included Alcaligenes faecalis, Staphylococcus saprophyticus, Bacillus thuringiensis, Enterobacter cloacae and Skermanella stibiiresistens. Of all the bacterial strains, B. thuringiensis showed a wide range of antagonistic activity towards fish pathogens, highest growth rate (0.34 %) with shortest doubling time (204 seconds) and survived through all the extreme environmental challenges (low acid, high bile and temperature). It seems that B. thuringiensis has more advantages than the other bacterial strains, and is assumed to have better probiotic potential. However, study to determine the beneficial effect of Bacillus thuringiensis in probiotic formulation requires further investigation

Temporal and spatial variability of heavy metals in Marudu Bay, Malaysia

The current study was conducted to estimate the baseline concentration of heavy metals in the surface sediment of Marudu Bay. Environmental parameters were measured at the seafloor and samples of the surface sediment were collected at monthly intervals for the period of 12 months. The organic content, total N, total P and concentration of 16 trace metals in the surface sediment were analyzed. The baseline concentration of metals was estimated by geochemical normalization. Anthropogenic inputs of metals were then estimated by calculating the enrichment factor for each element. The result demonstrated that the C/N ratio of sediment at Marudu Bay varies from 15 to 342, which indicates the dominance of terrestrial organic matter. The baseline concentration of V, Fe, Mn, Zn, Ti, Rb and Sr were 26.74 mg kg-1, 1.04%, 205.31 mg kg-1, 34.09 mg kg-1, 507.61 mg kg-1, 93.25 mg kg-1, 37.56 mg kg-1, respectively. The concentration of most metals was comparable to the baseline, except Mn and Zn which showed higher concentrations in most parts of Marudu Bay. In conclusion, the metal concentration in Marudu Bay is still within the permissible levels and should not cause any threats to public health