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

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

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

Taxonomic classification of Vibrio harveyi using 16S rDNA and atpA gene sequencing method

Genotypic analyses could provide highly accurate information on taxonomic linage and can be used to develop identification tool for fish bacterial pathogens. In this study, the nucleotide sequences of 16S rRNA and atpA genes in15 strains of V. harveyi were analyzed to determine which of these genes provide high confident level in the identification of the bacterial pathogen. In addition, the phenotypic characteristics and antibiotic susceptibility of the bacterial strains were also determined. The phenotypic analysis classified V. harveyi strains into 5 phenotypic groups. Each of this phenotypic group also exhibited variable responses to antibiotics. The 16S rRNA gene sequence analysis grouped V. harveyi into two main groups. The grouping was due to the presence of two unique nucleotide sequences located at nt1004 – nt1013 (V. harveyiATCC 35084 (GQ370528)). Unfortunately, these unique sequences were also found in other closely related Vibrio species. On the other hand, the atpA gene sequencing analysis clustered all the V. harveyi strains into a single group and differentiated from closely related species. The single clustering of V. harveyi was the result of the presence of one unique sequence at the nucleotide positions, nt1071 – nt1122 (V. harveyiATCC 35084 (JF723525)). The present study shows that phenotypic characterization and antibiotic susceptibility test may not be able to identify V. harveyi strains with high degree of confidence. Although, 16S rDNA gene sequencing analysis has been widely accepted as the universal method for bacterial identification, it is less useful in taxonomic classification ofV. harveyi. Hence our study suggests that atpA gene may be the best target for DNA sequencing analysis for the purpose of taxonomic classification of V. harveyi