The release of malachite green, a commonly used triphenylmethane dye, into the environment is causing increasing concern due to its toxicity, mutagenicity, and carcinogenicity. A bacterial strain that could degrade malachite green was isolated from the water of an aquatic hatchery. It was identified as a Pseudomonas sp. based on the morphological, physiological, and biochemical characteristics, as well as the analysis of 16S rRNA gene sequence and designated as MDB-1. This strain was capable of degrading both malachite green and leucomalachite green, as well as other triphenylmethane dyes including Crystal Violet and Basic Fuchsin. The gene tmr2, encoding the triphenylmethane reductase from MDB-1, was cloned, sequenced and effectively expressed in E. coli. These results highlight the potential of this bacterium for the bioremediation of aquatic environments contaminated by malachite green.

The aim of this study was to gain an understanding of the effects of mariculture on the bacterial communities in a co-culture pond, which is a popular culture model for shrimp, crab, and shellfish along the eastern coast of China. Six seawater samples were collected from a pond with cultures of shrimp, crab, and shellfish, and six other samples were collected from a non-cultured pond (control). The diversity of the bacterial communities in the samples was examined using the MiSeq desktop sequencer (Illumina) to amplify and sequence the V4-V5 region of the 16S ribosomal DNA analysis. The Meta-Stat computer program was used to assess the differences in the two communities. The sequences produced from all 12 samples were categorized into 1533 unique phylotypes, including 30 phyla, 81 classes, 270 families, and 414 genera. The top five dominant communities in the culture pond were Proteobacteria, Chloroflexi, Actinobacteria, Firmicutes, and Acidobacteria, while Proteobacteria, Planctomycetes, Bacteroidetes, Actinobacteria, and Cyanobacteria were the dominant communities in the control pond. Higher abundance was observed in the culture pond at the phylum, class, and genus levels, and the same result was also observed in the rarefaction curves. Elusimicrobia, Fibrobacteres, Fusobacteria, Tenericutes, MVP-21, SM2F11, and WCHB1-60 were present, whereas Deferribacteres and Lentisphaerae, as well as the candidate divisions BRC1, OD1, and OP11, disappeared from the culture pond. Moreover, abundant phylotypes (Aeromonadaceae, P s e u d o m o n a d a c e a e , E n t e r o b a c t e r i a c e a e , Bradyrhizobiaceae, Clostridiaceae, and Xanthomonadaceae) were present in the culture pond, but only rarely present in the control pond. These results suggest that mariculture contributed to the change in bacterial communities in the culture pond compared with the non-culture pond. Proteobacteria was the most dominant community in both ponds, but the second most dominant community was Planctomycetes in the control pond and Chloroflexi in the culture pond. Seven new phyla were observed, but five phyla disappeared in the culture pond. The disease-or metabolism-related members of the bacterial communities, namely, Aeromonadaceae, P s e u d o m o n a d a c e a e , E n t e ro b a c t e r i a c e a e , and Xanthomonadaceae, were abundant phylotypes in the culture pond. Our results contribute to an improved understanding of the establishment and maintenance of the bacterial community structure in a complex aquaculture ecosystem and may have practical applications in terms of improving seawater quality and early disease warning in this popular mariculture model in China.

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Burkholderia sp. GB-01 strain was used to study different factors affecting its growth for inoculum production and then evaluated for abamectin degradation in soil for optimization under various conditions. The efficiency of abamectin degradation in soil by strain GB-01 was seen to be dependent on soil pH, temperature, initial abamectin concentration, and inoculum size along with inoculation frequency. Induction studies showed that abamectin depletion was faster when degrading cells were induced by pre-exposure to abamectin. Experiments performed with varying concentrations (2-160 mg Kg(-1)) of abamectin-spiked soils showed that strain GB-01 could effectively degrade abamectin over the range of 2-40 mg Kg(-1). The doses used were higher than the recommended dose for an agricultural application of abamectin, taking in account the over-use or spill situations. A cell density of approximately 10(8) viable cells g(-1) dry weight of soil was found to be suitable for bioremediation over a temperature range of 30-35°C and soil pH 7.5-8.5. This is the first report on bacterial degradation of abamectin in soil by a Burkholderia species, and our results indicated that this bacterium may be useful for efficient removal of abamectin from contaminated soils.

A bacterial strain K9 capable of degrading malachite green was isolated from the sludge of the wastewater treatment system of a chemical plant. It was identified preliminarily as Pseudomonas sp. Strain K9 was also able to degrade other triphenylmethane dyes, such as Crystal Violet and Basic Fuchsin. The gene tmr2, encoding the triphenylmethane reductase, was cloned from strain K9, and functionally expressed in E. coli. A 5946-bp DNA fragment including the tmr2 gene was cloned from the genomic DNA of strain K9 by chromosome walking. Its sequence analysis showed that tmr2 was associated with a typical mobile element ISPpu12 consisting of tnpA (encoding a transposase), lspA (encoding a lipoprotein signal peptidase) and orf1 (encoding a putative MerR family regulator), orf2 (encoding a CDF family heavy metal/H(+) antiporter). This association was also found in another malachite green-degrading strain Pseudomonas sp. MDB-1, which indicated that the tmr2 gene might be a horizontally transferable gene.

Purpose This study sought to employ the response surface methodology (RSM) to investigate factors that affect Bacillus amyloliquefaciens X8 bacteriostasis. Methods Design Expert 8.0.6 was used to perform multiple regression fitting and create antimicrobial mathematical models to optimize the antimicrobial effect of Bacillus amyloliquefaciens X8. A Shodex Protein KW-2004 gel column and a C18 column coupled with a high-performance liquid chromatography (HPLC) system were used to separate and purify the antimicrobial substances extracted from Bacillus amyloliquefaciens X8 (X8-AS). An Agilent 6410 Triple Quad LC/MS system and Nicolet-is10 system were used to analyze X8-AS via liquid chromatography mass spectrometry (LC-MS) and infrared spectroscopy (IR). Results The results demonstrated that the optimum antimicrobial conditions for Bacillus amyloliquefaciens X8 (at which antimicrobial activity was increased by 22.3%) were pH 6, 30 ℃, and 36 h of incubation. Conclusion The results showed that the relative molecular weight of X8-AS was 1413.5 Da. After searching through the infrared spectrum material library, X8-AS was found to be highly similar to chondroitin sulfate.