Diversity of microcystins and non-microcystin-producing Microcystics population in the Dau Tieng reservoir, Vietnam

In this study, a 16S rDNA clone library was used to evaluate the diversity of potential microcystin producing cyanobacteria and polymerase chain reaction (PCR) was used to analyze the diversity of this population based on the presence of the mcyD gene in samples collected during a bloom season. The results revealed that Microcystis genera from the Dau Tieng reservoir (DTR) contained several genotypes. The isolated Microcystis strains from the DTR were found to consist both toxic and non-toxic species within species and population. In total 35 strains acounted for 58% were found to produce a mixture of microcystins (MCs). All samples of cyanobacterial blooms in the DTR contained high amount of MCs which could pose health risk to aquatic systems and local people.

Identification of the Dominant Microbial Species of Spoiled Crisp Grass Carp (Ctenopharyngodon idellus C. et V.) and Grass Carp (Ctenopharyngodon idellus) Fillets during Cold Storage by Culture-Independent 16S rDNA Sequence Analysis

ABSTRACT A new freshwater cultivation species, crisp grass carp (CGC; Ctenopharyngodon idellus C. et V.) has a special texture and is popular with consumers; thus, we should pay close attention to its storage conditions and bacterial degradation. CGC and grass carp (GC; Ctenopharyngodon idellus) were commercialized as fillets and subsequently stored at 4 and 8°C. Microbial growth parameters (total viable counts, psychrotrophic bacteria, and Pseudomonas spp.), physicochemical data (pH and total volatile base nitrogen), and sensory analysis were monitored during the storage period. Dominant microorganisms were identified using a 16S rDNA clone library and restriction fragment length polymorphism (RFLP) analysis after the fillets had spoiled completely. The results showed that Pseudomonas spp. lagged behind the psychrotrophic population and the total viable counts initially and increased more rapidly after storage for 2 days. Total volatile base nitrogen contents were found to increase with storage time in both species, coinciding with ongoing microbial change. The pH results obtained for both species during storage showed an overall increase at the end of storage. Sensory evaluation showed a shelf life of 3 and 6 days for both species at 8 and 4°C, respectively. RFLP analysis of the 16S rDNA clone library revealed that there were seven and five distinct RFLP pattern groups in the microflora of the spoiled CGC and GC fillets, respectively. Through RFLP patterns and 16S rDNA sequencing from the clones, it was determined that CGC fillets stored at 4°C were dominated by Pseudomonas spp. at the point of sensory rejection, whereas GC fillets were dominated by populations affiliated with Pseudomonas sp., Acinetobacter sp., and Aeromonas sp.

Bacterial Diversity in the High Arsenic Groundwater Systems of Jianghan Plain and Datong Basin by 16S rDNA Clone Library

To compare the difference bacterial diversity between Jianghan plain and Datong basin. The high arsenic sediment samples in this study were collected from different depths of borehole. The bacterial diversity in high arsenic aquifer sediments was studied by 16S rDNA clone library. The dominant bacterial community included Burkholderiales, Pseudomonadales, and Enterobacteriales in Jianghan plain, and Burkholderiales,Enterobacteriales and Actinomycetales in Datong basin.

Biodegradation of Lindane and Lignocellulose by Microbial Community

In order to investigate the capability of degradation lindane and lignocellulose of a microbial community, the gas chromatography(GC) was used to determine the concentration of lindane. After 18 days cultured, lindane reduced 6.25% more than the control. And the result of gas chromatography and mass spectrometry (GCMS) showed that the species and quantum of fermentation productions changed much in different phase. In order to determine the bacterial composition of the community, clone library was used to clarified bacterial composition. Constructed 16S rDNA clone library showed 60% closest relative among them were known the detailed information. Strain of closest relative of Clostridium may be main contribute to lignocellulose degradation, and closest relative of Proteobacterium may be the main contribute to degradation organochlorine pesticide (lindane).