Genetic analysis of protoplast fusant Xhhh constructed for pharmaceutical wastewater treatment

Construction of a fusant bacterial strain simultaneously degrading atrazine and acetochlor and its application in soil bioremediation

Application of herbicide-degrading bacteria is an effective strategy to remove herbicide in soil. However, the ability of bacteria to degrade a herbicide is often severely limited in the presence of other pesticide. In this study, the atrazine-degrading strain Klebsiella varicola FH-1 and acetochlor-degrading strain Bacillus Aryabhatti LY-4 were used as parent strains to construct the recombinant RH-92 strain through protoplast fusion technology. Compared with the parent strains, RH-92 exhibited enhanced ability to degrade herbicide mixture containing atrazine and acetochlor, exhibiting 63.16 % and 68.48 % higher degradation rates, respectively. RAPD analysis showed that gene rearrangement occurred during protoplast fusion, and the genetic similarity indexes of the fused strain RH-92 and the two parent strains were 0.5853 and 0.4240, respectively. HPLC-MS analysis confirmed that RH-92 shared similar degradation products and pathways with both parent strains but exhibited a novel metabolic pathway for the continuous degradation of CMEPA (degradation product of acetochlor) into MEA through amide bond hydrolysis. The activities of GSH, GST and SOD of RH-92 increased and the level of MDA decreased under the stress of compound herbicides. Strain RH-92 did not show a large number of bacterial apoptosis, and maintained good cell membrane integrity and permeability. The half-lives of atrazine and acetochlor were 4.9 d and 7.6 d when the parent strains FH-1 and LY-4 were applied in unsterilized soil containing herbicide mixture treatment,the application fusant RH-92 strain significantly reduced the half-life to 1.6 and 1.8 d, respectively. Furthermore, 16S rRNA sequencing indicated that RH-92 application effectively restored bacterial taxa with diminished relative abundances under herbicide mixture treatment, ameliorated phytotoxicity in soybean seedlings, and promoted enhanced vegetative growth in the roots and plant height. This study highlighted the application of fusant strains as a bioremediation strategy for combatting atrazine and acetochlor pollution in soil and provided theoretical insights.

Highly toxic and broad-spectrum insecticidal local Bacillus strains engineered using protoplast fusion

Protoplast fusion was performed between a local Bacillus thuringiensis UV-resistant mutant 66/1a (Bt) and Bacillus sphaericus GHAI (Bs) to produce new Bacillus strains with a wider spectrum of action against different insects. Bt is characterized as sensitive to polymyxin and streptomycin and resistant to rifampicin and has shown 87% mortality against Spodoptera littoralis larvae at concentration of 1.5 × 10(7) cells/mL after 7 days of feeding; Bs is characterized as resistant to polymyxin and streptomycin and sensitive to rifampicin and has been shown to have 100% mortality against Culex pipiens after 1 day of feeding at the same concentration as that of Bt. Among a total of 64 Bt::Bs fusants produced on the selective medium containing polymyxin, streptomycin, and rifampicin, 17 fusants were selected because of their high mortality percentages against S. littoralis (Lepidoptera) and C. pipiens (Diptera). While Bt harboured 3 plasmids (600, 350, and 173 bp) and Bs had 2 plasmids (544 and 291 bp), all the selected fusants acquired plasmids from both parental strains. SDS-PAGE protein analysis of the 17 selected fusants and their parental strains confirmed that all fusant strains acquired and expressed many specific protein bands from the 2 parental strains, especially the larvicidal proteins to both lepidopteran and dipteran species with molecular masses of 65, 70, 80, 88, 100, and 135 kDa. Four protein bands with high molecular masses of 281, 263, 220, and 190 kDa, which existed in the Bt parental strain and did not exist in the Bs parental strain, and 2 other protein bands with high molecular masses of 185 and 180 kDa, which existed in the Bs parental strain and did not exist in the Bt parental strain, were expressed in most fusants. The results indicated the expression of some cry genes encoded for insecticidal crystal proteins from Bt and the binary toxin genes from Bs in all fusant strains. The recombinant fusants have more efficient and potential values for agricultural application compared with both the insecticidal Bt and the mosquitocidal Bs strains alone against S. littoralis and C. pipiens larvae, respectively.

Construction and analysis of high-ethanol-producing fusants with co-fermentation ability through protoplast fusion and double labeling technology

Double labeling of resistance markers and report genes can be used to breed engineered Saccharomyces cerevisiae strains that can assimilate xylose and glucose as a mixed carbon source for ethanol fermentation and increased ethanol production. In this study Saccharomyces cerevisiae W5 and Candida shehatae 20335 were used as parent strains to conduct protoplast fusion and the resulting fusants were screened by double labeling. High performance liquid chromatography (HPLC) was used to assess the ethanol yield following the fermentation of xylose and glucose, as both single and mixed carbon sources, by the fusants. Interestingly, one fusant (ZLYRHZ7) was demonstrated to have an excellent fermentation performance, with an ethanol yield using the mixed carbon source of 0.424 g g⁻¹, which compares with 0.240 g g⁻¹ (W5) and 0.353 g g⁻¹ (20335) for the parent strains. This indicates an improvement in the ethanol yield of 43.4% and 16.7%, respectively.

Construction and analysis of an intergeneric fusant able to degrade bensulfuron-methyl and butachlor

Rhodococcus sp. BX2 degrades bensulfuron-methyl but not butachlor, and Acinetobacter sp. LYC-1 degrades butachlor but not bensulfuron-methyl. Functional strains were constructed through protoplast fusion of Rhodococcus sp. BX2 and Acinetobacter sp. LYC-1 to generate fusants with an improved ability to simultaneously degrade bensulfuron-methyl and butachlor. Initial identification and stability tests of the fusants were performed. Three fusants with eighth transfer on plates containing two antibiotics and two herbicides were obtained. F1 also grew well in an inorganic salt solution containing bensulfuron-methyl and butachlor. F1 was characterized by its parents' morphological and physio-biochemical features. F1 not only had bands in common with BX2 and LYC-1, but also had its own specific bands analyzed by Random Amplified Polymorphic DNA. The genetic similarity indices between F1 and BX2 and F1 and LYC-1 were 0.507 and 0.470, respectively. The percentages bensulfuron-methyl and butachlor degradation by F1 in an inorganic salt solution supplemented with 100 mg/L bensulfuron-methyl and 100 mg/L butachlor were 65.35 and 62.41 %, respectively, and the percentages in soil contaminated with 10 mg/kg bensulfuron-methyl and 10 mg/kg butachlor with an inoculum size of 5 % at 34 °C and at a pH of 7.5 after 35 days were 63.74 and 61.53 %, respectively. It was demonstrated that F1 could simultaneously degrade bensulfuron-methyl and butachlor.

Exopolysaccharide production by a genetically engineered Enterobacter cloacae strain for microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is a petroleum biotechnology for manipulating function and/or structure of microbial environments existing in oil reservoirs for prolonged exploitation of the largest source of energy. In this study, an Enterobacter cloacae which is capable of producing water-insoluble biopolymers at 37°C and a thermophilic Geobacillus strain were used to construct an engineered strain for exopolysaccharide production at higher temperature. The resultant transformants, GW3-3.0, could produce exopolysaccharide up to 8.83 g l(-1) in molasses medium at 54°C. This elevated temperature was within the same temperature range as that for many oil reservoirs. The transformants had stable genetic phenotype which was genetically fingerprinted by RAPD analysis. Core flooding experiments were carried out to ensure effective controlled profile for the simulation of oil recovery. The results have demonstrated that this approach has a promising application potential in MEOR.

Microbial dynamics in a sequencing batch reactor treating alkaline peroxide mechanical pulp and paper process wastewater

BACKGROUND, AIM, AND SCOPE

For many years, highly concentrated wastewater generated from the pulp and paper industry has become the focus of much concern worldwide. The objectives of this study were to determine the treatment efficiency of the alkaline peroxide mechanical pulp (APMP) process wastewater using a sequencing batch reactor (SBR) and analyze the microbial dynamics of the wastewater treatment system using the random amplified polymorphic DNA (RAPD) method.

MATERIALS AND METHODS

An SBR was applied to the treatment of APMP pulp and paper process wastewater. The wastewater characteristics and many physicochemical operator indicators in the wastewater treatment process were analyzed and determined according to standard methods. Microbial 16 S rDNA in active sludge was extracted, amplified, and analyzed using the RAPD method for the microbial dynamics of the wastewater treatment system.

RESULTS AND DISCUSSION

Ten kinds of natural organic compounds of plants such as monoterpene were detected in the APMP pulp and paper process wastewater. With an influent chemical oxygen demand (COD) that varied in the range of 685.7 to 907.5 mg/L, the corresponding effluent COD was 176.5 to 266.1 mg/L and the removal efficiency was 70.3% to 79.8%. An optimal strain (S308: CAGGGGTGGA) was selected to study the population dynamics and diversity of the bacterial community. The RAPD-polymerase chain reaction (PCR) fingerprints showed very high polymorphism of the genetic bands (78-100%). Four groups of species were clustered using the unweighted pair group method with arithmetic (UPGMA) analysis, and the genetic distance was close between the species within each group. The Shannon-Weaver index was high and varied over time with the COD removal.

CONCLUSIONS

The RAPD-PCR technique can be used to study microbial dynamics, which was shown to vary over time with the removal efficiency of SBR treating APMP pulp and paper process wastewater.

Effects of Yangtze River source water on genomic polymorphisms of male mice detected by RAPD

In order to evaluate the environmental health risk of drinking water from Yangtze River source, randomly amplified polymorphic DNA (RAPD) markers were used to detect the effects of the source water on genomic polymorphisms of hepatic cell of male mice (Mus musculus, ICR). After the mice were fed with source water for 90 days, RAPD-polymerase chain reactions (PCRs) were performed on hepatic genomic DNA using 20 arbitrary primers. Totally, 189 loci were generated, including 151 polymorphic loci. On average, one PCR primer produced 5.3, 4.9 and 4.8 bands for each mouse in the control, the groups fed with source water and BaP solution, respectively. Compared with the control, feeding mice with Yangtze River source water caused 33 new loci to appear and 19 to disappear. Statistical analysis of RAPD printfingers revealed that Yangtze River source water exerted a significant influence on the hepatic genomic polymorphisms of male mice. This study suggests that RAPD is a reliable and sensitive method for the environmental health risk of Yangtze River source water.

Degradation of benzo(a)pyrene in Yangtze River source water with functional strains

Degradation of benzo(a)pyrene (BaP) existing in the Yangtze River, used as source water for Nanjing City, China, was investigated with functional strains. The removal rates of BaP were 37.5, 20.8 and 70.8% for the three strains of the native bacterium NJ, and the two functional strains of Xhhh and Fhhh, respectively. The Fhhh specific degradation rate of BaP was 3.02 x 10(-6) day(-1), which was 1.9-fold of the rate with NJ and 3.7-fold of the rate with Xhhh. The concentrations of BaP in the source water, tap water and Fhhh reactor effluent were 8.3-, 7.6-, and 2.4-fold of that of the oral carcinogenicity unit risk. The results suggest that the functional strain Fhhh could be used for the reduction of BaP concentrations in source water and hence reduction of carcinogenic risk.

Extracellular proteomic analysis for degradation of PAHs in source of drinking water with fusant strains

Extracellular proteomic expressions of two fusant strains were analyzed to observe their abilities to degrade polycyclic aromatic hydrocarbons (PAHs) in the source of drinking water from Yangtze River. The extracellular proteomes for the hybrid strains, Fhhh and Xhhh, and one of their parental strain Phanerochaete chrysosporium were measured by the two-dimensional electrophoresis and MS/MS. The similarity of proteome expression was 34.7% between Fhhh and P. chrysosporium and that was 28.6% between Xhhh and P. chrysosporium. PAHs degeneration performance for Fhhh, Xhhh and the native bacterium NJ2007 was studied by biological activated carbon reactor. The specific degradation rate of Fhhh for PAHs was 3.05 x 10(-5) day(-1) which was significantly higher than that of the NJ2007 and Xhhh (P < 0.05). The results indicate that the fusant strain could not express the same proteome as that of its parental strain but could degrade PAHs in the source water with higher efficiency.