Arsenic Removal from Aqueous Solutions by Different Bacillus and Lysinibacillus Species

Removal of toxic and carcinogenic arsenic from underground water is very essential for the safety of water that may be used for drinking or irrigation. In this study, six different bacterial strains were recently isolated from a groundwater sample, routinely used for irrigation at Taif City, Kingdom of Saudi Arabia, containing arsenic, vanadium, and boron. The isolates were molecularly identified and the 16S rDNA sequencing data revealed their belonging to two different genera, Bacillus and Lysinibacillus. B. cereus strains EA4, EA5, and EA6 were able to resist arsenic up to 15 mg/L. B. cereus strain EA5 and a mixed culture of L. sphaericus EA1, B. fusiformis EA2, and Lysinibacillus sp. EA3 were found to be efficient in bioremediation of arsenic oxychloride up to 94.9% and 99.7%, respectively. Due to these near-standard records, these strains are strongly recommended for bioremediation of the highly toxic arsenic from the environment. B. cereus EA5 was also effective to remediate different concentrations of arsenic. High concentrations of arsenic showed dramatic decrease in the bioremediation activity of this strain. Reduction in cell size was distinct in scanning electron micrographs when cells were exposed to arsenic. Besides, protein electrophoresis showed that around 15 different stress proteins were produced when cells of B. cereus EA5 were exposed to arsenic oxychloride.     

Isolation of Bacterial Strain from Sediment Core of Pulp and Paper Mill Industries for Production and Purification of Lignin Peroxidase (LiP) Enzyme

Five bacterial strains were isolated and purified (CSA101 to CSA105) from the sediment core of the effluent released from the Century Pulp and Paper Mill Ltd., India. These strains were grown in minimal salt medium (MSM) containing pulp (10% as a carbon source). The production of lignin peroxidase, CMCase, Fpase, and xylanase together with protein and reducing sugar by all bacterial strains was observed. All of the bacterial isolates responded differently with respect to growth and ligninocellulolytic enzyme production. The maximum lignin peroxidase (LiP) was obtained from the cell extract of Bacillus sp. (CSA105) strain, which was used for purification, fractionation and characterization. The culture filtrate from Bacillus sp. (CSA105) was purified with ammonium sulfate precipitation. Crude protein was desalted by dialyzing with Tris buffer. The lignolytic enzyme produced in the liquid medium was fractionated by gel filtration on Sephadex G-100. In the present study, 12.4-fold purification of LiP enzyme was obtained and 35.85% yield of lignin peroxidase was achieved in the cell extract of Bacillus sp. (CSA105). Lignin peroxidase enzyme plays an important role in lignin degradation process. The ligninolytic enzymes were produced by all of the bacterial strains but maximum lignin peroxidase activity was found in cell extract of CSA105. On the basis of the results obtained, the bacterial strain (CSA105) was found most suitable for the purification of the LiP enzyme.     

Novel Hyper Antimony-Oxidizing Bacteria Isolated from Contaminated Mine Soils in China

Antimony (Sb)-oxidizing bacteria play an important role in environmental Sb bioremediation because of their ability to convert the more toxic Sb(III) to the less toxic Sb(V). So far, the information about the Sb(III)-oxidizing bacteria species is still limited. In this study, three highly Sb(III)-resistant bacterial strains were isolated from contaminated mine soils after aerobic enrichment culturing with Sb(III) (1 mM). The morphological, biochemical, and 16S rRNA gene sequencing analysis suggested that the three novel bacterial isolates fell within Cupriavidus, Moraxella, and Bacillus, respectively. Among the strains, Moraxella sp. S2 isolated from soils with the highest Sb content exhibited the highest minimum inhibitory concentration for Sb(III) but the lowest Sb(III) oxidation efficiency, which could not completely oxidize 50 μM Sb(III) in 15 days. Cupriavidus sp. S1 was able to oxidize 50 μM Sb(III) completely in 12 days, but could not oxidize 100 μM Sb(III) even with extended time of incubation, while Bacillus sp. S3 with the lowest resistance to Sb(III) could aerobically oxidize 100 µM Sb(III) within 2 days, showing high Sb(III) oxidation efficiency. Our research demonstrated that indigenous microorganisms associated with Sb mine soils were capable of Sb oxidation, and the novel bacteria isolated could represent good candidates for Sb remediation in heavily polluted sites.     

A study on the utility of immobilized cells of indigenous bacteria for biodegradation of reactive azo dyes

Abstract

Azo dyes are recalcitrant compounds used as a colorant in various industries. The pollution caused by their extensive usage has adversely affected the environment for years. The existing physicochemical methods for dye pollution remediation are rather inefficient and hence there is a dearth of low-cost, potential systems capable of dye degradation. The current research studies the biodegradation potential of immobilized bacterial cells against azo dyes Reactive Orange 16 (RO-16) and Reactive Blue 250 (RB-250). Two indigenous dye degrading bacteria Bacillus sp. VITAKB20 and Lysinibacillus sp. KPB6 was isolated from textile sludge sample. Free cells of Bacillus. sp. VITAKB20 degraded 92.38% of RO-16 and that of Lysinibacillus sp. KPB6 degraded 95.36% of RB-250 within 72?h under static conditions. Upon immobilization with calcium alginate, dye degradation occurred rapidly. Bacillus. sp. VITAKB20 degraded 97.5% of RO-16 and Lysinibacillus sp. KPB6 degraded 98.2% of RB-250 within 48?h under shaking conditions. Further, the nature of dye decolorization was biodegradation as evident by high-performance liquid chromatography (HPLC), and Fourier-transform infrared spectroscopy (FTIR) results. Phytotoxicity and biotoxicity assays revealed that the degraded dye products were less toxic in nature than the pure dyes. Thus, immobilization proved to be a highly likely alternative treatment for dye removal.     

Bioremediation of sago industry effluent and its impact on seed germination (green gram and maize)

In this study, we attempted two investigational systems: one is treatment of sago industry effluent by aerobic bacterial consortium and the other is impact of treated and untreated effluent on seed germination. For the treatment system, the starch degrading bacteria were isolated from sago industry effluent and effluent contaminated soil. The genera, Alcaligenes, Bacillus and Corynebacterium were found efficient in starch degradation. The selected isolates were tested for their efficiency on the degradation of starch both in Mineral Salts Medium (MSM) and in sago industry effluent. About 85% of the starch was degraded in MSM by a bacterial consortium composed of Alcaligenes, Bacillus and Corynebacterium, whereas in effluent the degradation of starch was only 63%. The physico-chemical properties such as electrical conductivity, total solids, suspended solids, dissolved solids, BOD, COD, nitrogen and phosphate were found decreased in effluent after 72 h. The pH of the effluent was relatively increased from 3 to 6.7. The study of seed germination (maize and green gram) was carried out at 25, 50, 75 and 100% concentrations of treated and untreated effluent using soil sowing method. Shoot length, root length, fresh weight, dry weight and chlorophyll content showed an increase when treated effluent was tested whereas a decrease of growth was noticed in untreated effluent tested seedlings. The results revealed that effluent treated by aerobic microorganisms has no negative impact on the seed germination and can be effectively used for irrigation.     

Membrane fatty acids adaptive profile in the simultaneous presence of arsenic and toluene in <Emphasis Type="Italic">Bacillus</Emphasis> sp. ORAs2 and <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. ORAs5 strains

Bacillus sp. ORAs2 and Pseudomonas sp. ORAs5, two arsenic-resistant bacterial strains previously isolated from sediments of the Orbetello Lagoon, Italy, were tested for their adaptation to mixed contaminants on the level of membrane fatty acid composition. The two bacterial strains were characterized by high levels of arsenic resistance, and Pseudomonas sp. ORAs5 was also shown to be solvent-tolerant. The bacterial strains were exposed to mixtures of two toxic compounds: arsenic at fixed concentrations and toluene in variable amounts or, alternatively, toluene at constant values along with arsenic added at variable concentrations. Both strains react to the contaminants by changing the composition of their membrane fatty acids. Bacillus sp. strain ORAs2 showed a correlation between growth rate decreases and fatty acids degree of saturation increases in both cases, although pointedly in the presence of 1, 2, and 3 mM of toluene and different additions of arsenic, counteracting membranes fluidity induced by toxic compounds. In Pseudomonas sp. ORAs5, adaptive changes in membrane composition was observed both in terms of increases in the degree of saturation and in the trans/cis ratio of unsaturated fatty acids in the presence of varying toluene and constant arsenic concentrations, whereas only minor changes occurred with increasing arsenic and constant toluene concentrations. Thus, on the level of membrane composition, Bacillus sp. ORAs2 showed a higher potential for adaptation to the presence of mixed pollutants, suggesting its probable suitability for bioremediation purposes.     

Isolation and characterization of chromium(VI)-reducing Bacillus sp. FY1 and Arthrobacter sp. WZ2 and their bioremediation potential

Two native bacterial strains, FY1 and WZ2, that showed high chromium(VI)-reducing ability were respectively isolated from electroplating and tannery effluent–contaminated sites and identified as Bacillus and Arthrobacter. The objective of the present study was to evaluate their potential for future application in soil bioremediation. The results showed that both Bacillus sp. FY1 and Arthrobacter sp. WZ2 were tolerant to 1000 mg L^?1 Cr(VI) and capable of reducing 78–85% and 75–82% of Cr(VI) (100–200 mg L^?1) within 24 h, respectively. The Cr(VI) reduction rate decreased with increasing levels of Cr(VI) concentration (200–1000 mg L^?1). The optimum pH, temperature, and inoculum concentration for Cr(VI) reduction were found to be between pH 7.0 and 8.0; 30 and 35°C; and 1 × 10⁸ cells ml^?1, respectively. Further evidence for the bioremediation potential of Bacillus sp. FY1 and Arthrobacter sp. WZ2 was provided by the high capacity to reduce 100, 200, and 500 mg kg^?1 Cr(VI) in contaminated soil by 83–91%, 78–85%, and 71–78% within 7 days, respectively. These findings demonstrated the high potential of Bacillus sp. FY1 and Arthrobacter sp. WZ2 for application in future soil bioremediation.     

Biotransformation Patterns of 2,4,6-Trinitrotoluene by Aerobic Bacteria

2,4,6-Trinitrotoluene (TNT), a toxic nitroaromatic explosive, accumulates in the environment, making necessary the remediation of contaminated areas and unused materials. Although bioremediation has been utilized to detoxify TNT, the metabolic processes involved in the metabolism of TNT have proven to be complex. The three aerobic bacterial strains reported here (Pseudomonas aeruginosa, Bacillus sp., and Staphylococcus sp.) differ in their ability to biotransform TNT and in their growth characteristics in the presence of TNT. In addition, enzymatic activities have been identified that differ in the reduction of nitro groups, cofactor preferences, and the ability to eliminate-NO₂ from the ring. The Bacillus sp. has the most diverse bioremediation potential owing to its growth in the presence of TNT, high level of reductive ability, and capability of removing-NO₂ from the nitroaromatic ring. Received: 16 May 1997 / Accepted: 19 July 1997     

Enhanced decolorization of sulfonated azo dye methyl orange by single and mixed bacterial strains AK1, AK2 and VKY1

Abstract

Methyl orange, a sulfonated azo dye having various industrial applications was decolorized by three bacteria Bacillus sp. strain AK1, Lysinibacillus sp. strain AK2 and Kerstersia sp. strain VKY1. The effect of various factors such as dye concentration, pH, temperature and NaCl concentration on decolorization was investigated. At 200?mg/L methyl orange concentration, the strains AK1, AK2 and VKY1 exhibited maximum decolorizing potential of 93, 95 and 96%, respectively, at temperature 35?°C and pH 7.0 within 18?h of incubation. These strains decolorized the dye over a wide range of pH (5–10), temperature (15–55?°C), and NaCl concentration (5–20?g/L). Further, these strains decolorize up to 800?mg/L concentrations of methyl orange within 24?h. The dye decolorization efficiency was further increased by using different consortia of these three strains which could decolorize the dye completely within 12?h of incubation. The cell-free extracts of the strains AK1, AK2 and VKY1 grown on methyl orange exhibited the azoreductase activity of 0.4794, 1.56 and 1.01?µM/min/mg protein, respectively. HPLC and FTIR analysis of the dye decolorized sample indicated the formation of 4-aminobenzenesulfonic acid and N,N-dimethyl-p-phenylenediamine as breakdown products of azo bond. The high decolorization potential of these bacterial strains individually and in consortia has potential application in remediation of dye effluent.     

Evaluation of the Biotechnological Potential of Pure and Mixture of Indigenous Iron-Oxidizing Bacteria to Dissolve Trace Metals from Cu Bearing Ore

Abstract

This study aimed to investigate the ability of pure and consortia of indigenous iron-oxidizing bacteria to enhance the dissolution of trace metals from Cu and Zn-bearing ore. Three bacterial strains Acidithiobacillus ferrooxidans strain WG101, Leptospirillum ferriphilum strain WG102, Leptospirillum ferrooxidans strain WG103 isolated from Baiyin copper mine, China were used in this study. The biotechnological potential of these indigenous isolates was evaluated both in pure and in consortia to extract cobalt, chromium, and lead from the copper and zinc bearing ore. The sulfur and iron-oxidizing bacterial isolate Acidithiobacillus ferrooxidans strain WG101 exhibited efficient dissolution compared to sole iron-oxidizing Leptospirillum ferriphilum strain WG102, and Leptospirillum ferrooxidans strain WG103. Initial medium pH, pulp density, and temperature were studied as influential parameters in bioleaching carried out by bacterial consortia. The achieved optimum conditions were; initial pH of 1.5, 10% of pulp density, and temperature 30?°C with 68.7?±?3.9% cobalt, 56.6?±?3.9% chromium, and 36?±?3.7% lead recovery. Analytical study of oxidation-reduction potential and pH fluctuation were observed during this whole process that shows the metal dissolution efficiency of bacterial consortia. Alterations in spectral bands of processed residues were reported through FTIR analysis compared with control ore sample. Mössbauer spectroscopy analysis showed the influence of bacterial consortia on iron speciation in bioleached samples. The findings confirm that the indigenous acidophilic iron-oxidizing bacterial strains are highly effective in the dissolution of trace elements present in ore samples. This study not only supports the notion that indigenous bacterial strains are highly effectual in metal dissolution but provides the basic vital conditions to upscale the bioleaching technique for metals dissolution.     

Genome comparison provides molecular insights into the phylogeny of the reassigned new genus Lysinibacillus

Background

Lysinibacillus sphaericus (formerly named Bacillus sphaericus) is incapable of polysaccharide utilization and some isolates produce active insecticidal proteins against mosquito larvae. Its taxonomic status was changed to the genus Lysinibacillus in 2007 with some other organisms previously regarded as members of Bacillus. However, this classification is mainly based on physiology and phenotype and there is limited genomic information to support it.

Results

In this study, four genomes of L. sphaericus were sequenced and compared with those of 24 representative strains belonging to Lysinibacillus and Bacillus. The results show that Lysinibacillus strains are phylogenetically related based on the genome sequences and composition of core genes. Comparison of gene function indicates the major difference between Lysinibacillus and the two Bacillus species is related to metabolism and cell wall/membrane biogenesis. Although L. sphaericus mosquitocidal isolates are highly conserved, other Lysinibacillus strains display a large heterogeneity. It was observed that mosquitocidal toxin genes in L. sphaericus were in close proximity to genome islands (GIs) and mobile genetic elements (MGEs). Furthermore, different copies and varying genomic location of the GIs containing binA/binB was observed amongst the different isolates. In addition, a plasmid highly similar to pBsph, but lacking the GI containing binA/binB, was found in L. sphaericus SSII-1.

Conclusions

Our results confirm the taxonomy of the new genus Lysinibacillus at the genome level and suggest a new species for mosquito-toxic L. sphaericus. Based on our findings, we hypothesize that (1) Lysinibacillus strains evolved from a common ancestor and the mosquitocidal L. sphaericus toxin genes were acquired by horizontal gene transfer (HGT), and (2) capture and loss of plasmids occurs in the population, which plays an important role in the transmission of binA/binB.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1359-x) contains supplementary material, which is available to authorized users.Keyword: Lysinibacillus, Bacillus, Lysinibacillus sphaericus, Genome, Phylogeny     

Isolation and Characterization of Mercury Resistant Bacillus sp. from Soils with an Extensive History as Substrates for Mercury Extraction in Mexico

Metal phytoextraction assisted by bacteria plays an important role in bioremediation systems. In this work, mercury-resistant bacterial strains were isolated from soils with high levels of mercury (San Joaquin, Queretaro State, Mexico) and identified as Bacillus sp. based on the 16S rDNA gene sequence analysis. The bacterial strains were found to exhibit different multiple mercury-resistance and carbon source utilization characteristics. The mercury reduction ability was tested through a volatilization assay. The bacterial isolates were also evaluated for their ability to promote growth and mercury uptake in tomato plants. In a roll towel assay, the maximum vigor index of tomato plants was obtained with the inoculation of Bacillus sp. A2, A12, B11, B15 and C1, while in a pot assay, the maximum vigor index was obtained with the inoculation of Bacillus sp. A6, A7 and B20, compared with un-inoculated controls in the presence of HgCl₂. Maximum Hg accumulation in the roots and shoots of tomato plants was obtained only with Bacillus sp. A7 in the roll towel assay, whereas in the pot assay, maximum accumulation was obtained with Bacillus sp. A12 compared with un-inoculated controls. Our results show that mercury accumulation in tissue is enhanced by these plant growth promoting bacterial strains, which recommends their possible use as microbe-assisted phytoremediation systems in mercury-polluted soils.     

Simultaneous hydrocarbon biodegradation and biosurfactant production by oilfield-selected bacteria

Aims: To study the bacterial diversity associated with hydrocarbon biodegradation potentiality and biosurfactant production of Tunisian oilfields bacteria. Methods and Results: Eight Tunisian hydrocarbonoclastic oilfields bacteria have been isolated and selected for further characterization studies. Phylogenetic analysis revealed that three thermophilic strains belonged to the genera Geobacillus, Bacillus and Brevibacillus, and that five mesophilic strains belonged to the genera Pseudomonas, Lysinibacillus, Achromobacter and Halomonas. The bacterial strains were cultivated on crude oil as sole carbon and energy sources, in the presence of different NaCl concentrations (1, 5 and 10%, w/v), and at 37 or 55°C. The hydrocarbon biodegradation potential of each strain was quantified by GC–MS. Strain C450R, phylogenetically related to the species Pseudomonas aeruginosa, showed the maximum crude oil degradation potentiality. During the growth of strain C450R on crude oil (2%, v/v), the emulsifying activity (E24) and glycoside content increased and reached values of 77 and 1·33 g l^?1, respectively. In addition, the surface tension (ST) decreased from 68 to 35·1 mN m^?1, suggesting the production of a rhamnolipid biosurfactant. Crude biosurfactant had been partially purified and characterized. It showed interest stability against temperature and salinity increasing and important emulsifying activity against oils and hydrocarbons. Conclusions: The results of this study showed the presence of diverse aerobic bacteria in Tunisian oilfields including mesophilic, thermophilic and halotolerant strains with interesting aliphatic hydrocarbon degradation potentiality, mainly for the most biosurfactant produced strains. Significance and Impact of the Study: It may be suggested that the bacterial isolates are suitable candidates for practical field application for effective in situ bioremediation of hydrocarbon‐contaminated sites.     

Biodegradation kinetics of the benzimidazole fungicide thiophanate-methyl by bacteria isolated from loamy sand soil

Degradation of the fungicide thiophanate-methyl (TM) by Enterobacter sp. TDS-1 and Bacillus sp. TDS-2 isolated from sandy soil previously treated with TM was studied in mineral salt medium (MSM) and soil. Both strains were able to grow in MSM supplemented with TM (50 mg l⁻¹) as the sole carbon source. Over a 16 days incubation period, 60 and 77% of the initial dose of TM were degraded by strains TDS-1 and TDS-2, respectively, and disappearance of TM was described by first-order kinetics. Medium supplementation with glucose markedly stimulated bacterial growth; while the final rate of TM degradation was reduced by 21 and 27% for strains TDS-1 and TDS-2, respectively as compared to medium with TM only. Moreover, this additional carbon source changed the TM degradation kinetics, which proceeded according to a zero-order model. This effect was linked to substrate competition and/or a strong decrease of medium pH. Isolates degraded TM (100 mg kg⁻¹) in soil with rate constants of 0.186 and 0.210 day⁻¹, following first-order rate kinetics, and the time in which the initial TM concentration was reduced by 50% (DT50) in soils inoculated with strains TDS-1 and TDS-2 were 6.3 and 5.1 days, respectively. Analysis of TM degradation products in soil showed that the tested strains may have the potential to transform carbendazim (MBC) to 2-aminobenzimidazole (2-AB), and may be useful for a bioremediation of MBC-polluted soils.     

Studies on Biodegradation of Kerosene in Soil under Different Bioremediation Strategies

The effectiveness of bioremediation is often a function of the microbial population and how they can be enriched and maintained in an environment. Strategies for inexpensive in situ bioremediation of soil contaminated with petroleum hydrocarbons include stimulation of the indigenous microorganisms by introduction of nutrients (biostimulation) and/or through inoculation of an enriched mixed microbial culture into soil (bioaugmentation). To demonstrate the potential use of bioremediation in soil contaminated with kerosene, a laboratory study with the objective of evaluating and comparing the effects of bioattenuation, biostimulation, bioaugmentation, and combined biostimulation and bioaugmentation was performed. The present study dealt with the biodegradation of kerosene in soil under different bioremediation treatment strategies: bioattenuation, biostimulation, bioaugmentation, and combined biostimulation and bioaugmentation, respectively. Each treatment strategy contained 10% (w/w) kerosene in soil as a sole source of carbon and energy. After 5 weeks of remediation, the results revealed that bioattenuation, bioaugmentation, biostimulation, and combined biostimulation and bioaugmentation exhibited 44.1%, 67.8%, 83.1%, and 87.3% kerosene degradation, respectively. Also, the total hydrocarbon-degrading bacteria (THDB) count in all the treatments increased with time up till the second week after which it decreased. The highest bacterial growth was observed for combined biostimulation and bioaugmentation treatment strategy. A first-order kinetic model equation was fitted to the biodegradation data to further evaluate the rate of biodegradation and the results showed that the specific degradation rate constant (k) value was comparatively higher for combined biostimulation and bioaugmentation treatment strategy than the values for other treatments. Therefore, value of the kinetic parameter showed that the degree of effectiveness of these bioremediation strategies in the clean up of soil contaminated with kerosene is in the following order: bioattenuation < bioaugmentation < biostimulation < combined biostimulation and bioaugmentation. Conclusively, the present work has defined combined biostimulation and bioaugmentation treatment strategy requirements for kerosene oil degradation and thus opened an avenue for its remediation from contaminated soil.     

Potential role of bacterial extracellular polymeric substances as biosorbent material for arsenic bioremediation

Carcinogenic effects of arsenic through consumption of contaminated water are an alarming threat and there is an emergent need to reduce extremely high levels of toxic arsenic from environment. Bacterial biofilms produce polyanionic extracellular polymeric substance (EPS) that is considered an excellent biosorbent material for the remediation of toxic metals and metalloids. This study was aimed to investigate the role of bacterial EPS in arsenic bioremediation. EPS was extracted from biofilm forming and arsenic reducer bacterial strains that were isolated from industrial waste water and characterized biochemically. Fourier transform infrared spectroscopy was also performed to study functional groups. Both Exiguobacterium profundum PT2 and Ochrobactrum ciceri SW1 exhibited enhanced EPS production in the presence of arsenic. Arsenic stress increased protein and carbohydrate contents in the EPS of both bacterial strains as indicated by the peaks of 1363 to 1613 and 1035 to 1218?cm^?1 wavenumbers, respectively to cope with arsenic present in the surroundings. Shifting of peaks in As⁵⁺ treated samples from 1363 to 1379, 847 to 800 and 1211 to 1134?cm^?1 demonstrated the involvement of proteins, carbohydrates and phosphates in the sequestration of arsenic. Scanning electron microscopic examination of EPS revealed structural alterations such as the presence of closely embedded large clumps with interstitial spaces between stacked layers of the EPS of E. profundum PT2 treated with As⁵⁺ displayed the enhanced polysaccharide content and arsenic sorption. Therefore, increased production of bacterial EPS with large number of polyanionic functional groups on its surface having tendency to sequester arsenic through electrostatic or covalent interactions presented EPS an excellent biosorbent material for arsenic bioremediation.     

Biodegradation of hexazinone by two isolated bacterial strains (WFX-1 and WFX-2)

Two hexazinone-degrading bacterial strains were isolated from soil by enrichment culture technique, and identified as Pseudomonas sp. and Enterobacter cloacap, respectively. The two purified isolates, designated as WFX-1 and WFX-2, could rapidly degrade hexazinone with half-lives of 3.08 and 2.95 days in mineral salts medium (hereafter referred to as MSM). In contrast, their mixed bacterial culture (herein abbreviated as MBC) was found to degrade hexazinone, at an initial concentration of 50 mg l⁻¹, by enhancing 2.3-fold over that when the isolates were used alone. The degradation of hexazinone by MBC in MSM clearly decreased concomitant with the increase of initial concentration, and the level of hexazinone that was toxic enough to totally inhibit degradation was in the range of 150–200 mg l⁻¹. The appropriately combined conditions for hexazinone degradation by MBC in MSM were studied, and found to be pH 5.5, 30 °C and at agitation of 120 rpm. The addition of MBC to soil had a greater impact on disappearance of hexazinone, which nearly increased fivefold over that of the control set. As a result, findings in the present investigation provide useful information for soil and water decontamination of hexazinone.     

Application of Biofilm-Forming Bacteria on the Enhancement of Organophosphorus Fungicide Degradation

This study aimed to develop technology enhancing the biodegradation efficacy against organophosphorus fungicide with biofilm-forming bacteria in situ. Using the crystal violet staining method, two bacterial strains having biofilm formation capability were isolated and identified as Pseudomonas sp. C7 and Bacillus sp. E5. Compared with the culture of tolclofos-methyl degrader Sphingomonas sp. 224, biofilm formation was improved by co-inoculation with biofilm-forming bacterium Bacillus sp. E5. Evaluated in liquid culture conditions, this two-species mixed consortium was observed to degrade tolclofos-methyl more effectively than Sphingomonas sp. 224 alone, with an approximately 90% degradation efficiency within 48 h of dosing. The improved effectiveness of the consortium biofilm was reflected using soil in situ with an approximately 7% increased degradation ratio over Sphingomonas sp. 224 alone. This is the first report demonstrating improved bioremediation degradation efficacy against tolclofos-methyl exhibited by a consortium biofilm. This work presents a possible effective bioremediation strategy using a specific biofilm composition against pollutants containing organophosphorus compounds in situ.     

Endophytic bacteria mediate plant resistance against cotton bollworm

Abstract

The efficacy of endophytic bacterial strains was evaluated in cotton against American bollworm infestation under greenhouse conditions. Among the 103 endophytic bacterial strains, the Bacillus strains (EPCO 102 and EPCO 16) and Pseudomonas fluorescens strain Pf1 significantly reduced the bollworm incidence. Talc-based bioformulation of EPCO 102, EPCO 16 and P. fluorescens Pf1 with and without chitin in inducing systemic resistance was tested against bollworm. The application of the bioformulation through seed, soil and foliar spray significantly reduced the bollworm incidence. The amendment of chitin in the formulation further reduced the pest incidence. Maximum bollworm reduction by endophytic bacterial strains EPCO 102, EPCO 16 and Pf1 strain with chitin was recorded. In addition, endophytic bacterial bioformulation with chitin induced more and timely activities of chitinase, β-1, 3-glucanase, peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase and phenol in cotton plants infested with Helicoverpa armigera.     

Phenol degradation by Paenibacillus thiaminolyticus and Bacillus cereus in axenic and mixed conditions

In this study, seven aerobic bacterial strains were screened for phenol tolerance at different concentration of phenol. Bacterial strains were unable to utilize phenol in absence of glucose, indicated the phenomenon of co-metabolism. Among the seven isolated bacterial strains, only ITRC BK-4 and ITRC BK-7 found potential and identified as Paenibacillus thiaminolyticus (DQ435022) and Bacillus cereus (DQ435023), respectively. Phenol degradation was monitored routinely with spectrophotometer and further confirmed by HPLC analysis. ITRC BK-4, ITRC BK-7 and mixed culture degrade 700 ppm phenol up to 51.72, 70.00 and 84.57% respectively in mineral salt medium (MSM) at temperature 37 ± 1°C, pH 7.5 ± 0.2, 120 rpm in presence of 1% glucose (w/v) within 144 h incubation. The mix culture was found more potential for phenol degradation compared to axenic strains. Hence, the axenic and mixed strains of these bacteria would be useful for the removal/mineralization of phenol from industrial waste waters.