Study on toxigenic cyanobacteria of aquaculture ponds in Thailand

Proliferation of cyanobacteria is frequently encountered in natural eutrophicated lakes as well as in aquaculture ponds, since daily feeding contributes to the high nutrient loading for the intensive aquaculture. The extensive growth of cyanobacteria presents a considerable threat to human health because many species have the potential to produce cyanotoxin. Microcystis, in particular, is a typical bloom-forming cyanobacterial genus that produces a strong hepatotoxin microcystin. In this study, aquaculture ponds of catfish and tilapia in Thailand were surveyed to obtain the basic information on the occurrence of harmful cyanobacteria and cyanotoxins. This study provided two significant facets of information. One, from a viewpoint of the evaluation of the risk of cyanotoxins in aquaculture; the other, on the ecological study of toxigenic cyanobacteria at various environmental conditions. The relationship between the proliferation of toxigenic cyanobacteria and environmental conditions such as nutrients, temperature and kinds of cultured fish in aquaculture ponds were illuminated by mainly using conventional water quality analysis, quantitative real time PCR method (a molecular ecological method) and linear model analysis for the results. The results were summarized as follows. In September and December of 2009 and March of 2010, 22 ponds for commercial farming of Nile tilapia (Oreochromis niloticus) and 17 ponds for hybrid catfish (Clarias macrocephalus x C. gariepinus) were surveyed in the provinces of Chiang Mai, Chiang Rai and Phayao. Fish species (tilapia or catfish) did not significantly affect the occurrence of toxigenic cyanobacteria. Actually, mcyD gene was detected in 8 tilapia ponds and 11 catfish ponds. Then microcystin analyzed by HPLC was detected in only 4 tilapia ponds and 6 catfish ponds. However, these differences between catfish pond and tilapia pond were not statistical significant. On the other hands, chl-a, as a surrogate of total biomass of phytoplankton, depended on both T-N and T-P. Then the concentration of chl-a in high temperature season (March) was higher than that in low temperature season (December). On the other hand, total cyanobacteria mainly depended on T-P, then it was found much in December than in March. The detection probability of mcyD in aquaculture ponds was explained by a logistic model, mainly with T-P. The probability in March was lower than that in December

Whole-Genome Sequence of the Microcystin-Degrading Bacterium Sphingopyxis sp. Strain C-1

This report describes the whole-genome sequence of an alkalitolerant microcystin-degrading bacterium, Sphingopyxis sp. strain C-1, isolated from a lake in China

Off-flavor characterization in high nutrient load tilapia ponds in northern Thailand

These findings are an important step towards the prediction, control and management of the off-flavor problem in tilapia culture in high-nutrient load ponds. The aim was to determine the levels of odorous compounds (geosmin or 2-methylisoborneol (MIB) that potentially cause off-flavor problems in fish reared in integrated, high-nutrient-load ponds in northern Thailand. Without proper management of fish and animal numbers, as well as good water exchange, water quality can deteriorate and result in eutrophication which promotes cyanobacterial blooms that can harmfully affect water quality and produce odorous compounds. The paper details observations of Chlorophylla and Cyanobacterial abundance

Microcystin degradation in sphingopyxis sp. C-1

The microcystin-degrading gene cluster, mlrA-B-C-D, plaies an important role in the degradation process of hepatotoxic microcystins for several bacterial species. However after microcystin is degraded to linear-microcystin by MlrA, it is still unknown about where and by what it is metabolited. In order to clarify it, we disrupted the mlrB gene and mlrC gene in chromosome of microcystin-degrading bacteria, Sphingopyxis sp. C-1. The cells disrupted mlrB gene and mlrC gene accumulated of microcystin-degradation product, linear-microcystin and tetrapeptide, respectively, whereas the cell free extracts of ?mlrB cells detected Adda and ?mlrC cells accumulated tetrapeptide. Moreover, topology analysis of MlrB using the ß-lactamase gene fusion method insisted MlrB is the peripheral protein binding the inner-membrane. These results insist that MlrB degrades the linear microcystin in the periplasmic space and MlrC degrades tetrapeptide in cytoplasm. Thus, in intact cells, MlrC cannot degrade linear-microcystin as being separated in inner-membrane from linear-microcystin while MlrC is capable of degrading the linear-microcystin in cell-free extract

Applications and Data Analysis using Bayesian and Conventional Statistics in Biochar Adsorption Studies for Environmental Protection

The use of low-cost agricultural waste-derived biochar in solving water and environmental challenges induced by climate change was investigated and sound conclusions were presented. Water reuse strategies can diminish the impact of climate change in rural and remote areas of developing countries. The novel biochar materials from three agro-waste biomass (Matamba fruit shell, Mushuma, and Mupane tree barks) were investigated and characterized to attest to their capacity to remove iodine from the aqueous solution. Their surface morphologies were assessed using Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FESEM-EDX) which exhibited their structural phenomena to purge environmental pollutants. The Fourier-transform infrared spectroscopy (FTIR) was conducted to show surface functional groups of the biochar materials and Matamba fruit shell exhibited hydroxyl (-OH), carbonyl groups (C=O), C=C stretches of aromatic rings, and the carboxylate (C–O–O–) groups on its surface with corresponding data from the Isotherm and Kinetic models, statistically analyzed by the conventional and Bayesian methods. These surface mechanisms are said to be induced by weak van der Waals forces and - and -stacking interaction on the biochar surface. These adsorbents promised to be potential materials for environmental-ecosystem-protection and water re-use approach

Whole-genome sequence of the microcystin-degrading bacterium Sphingopyxis sp. strain C-1

This report describes the whole-genome sequence of an alkalitolerant microcystin-degrading bacterium, Sphingopyxis sp. strain C-1, isolated from a lake in China

Characteristics of Antibiotic Resistance and Tolerance of Environmentally Endemic <i>Pseudomonas aeruginosa</i>

Antibiotic-resistant bacteria remain a serious public health threat. In order to determine the percentage of antibiotic-resistant and -tolerant Pseudomonas aeruginosa cells present and to provide a more detailed infection risk of bacteria present in the environment, an isolation method using a combination of 41 °C culture and specific primers was established to evaluate P. aeruginosa in the environment. The 50 strains were randomly selected among 110 isolated from the river. The results of antibiotic susceptibility evaluation showed that only 4% of environmental strains were classified as antibiotic-resistant, while 35.7% of clinical strains isolated in the same area were antibiotic-resistant, indicating a clear difference between environmental and clinical strains. However, the percentage of antibiotic-tolerance, an indicator of potential resistance risk for strains that have not become resistant, was 78.8% for clinical strains and 90% for environmental strains, suggesting that P. aeruginosa, a known cause of nosocomial infections, has a high rate of antibiotic-tolerance even in environmentally derived strains. It suggested that the rate of antibiotic-tolerance is not elicited by the presence or absence of antimicrobial exposure. The combination of established isolation and risk analysis methods presented in this study should provide accurate and efficient information on the risk level of P. aeruginosa in various regions and samples