Isolation, identification and characterization of a novel Ralstonia sp. FD-1, capable of degrading 4-fluoroaniline

Microbial detoxification of bifenthrin insecticide by selected fungal strains and optimizing conditions using response surface methodology for agricultural sustainability

Bifenthrin is a type I broad spectrum pyrethroid insecticide widely employed in urban and agricultural settings with little knowledge about its biodegradation. Bifenthrin was subjected to a 35 days incubation period in which it was degraded by five fungal strains named as Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Penicillium chrysogenum, and Lasiodiplodia theobromae. Penicillium chrysogenum was found to be extremely effective in degrading bifenthrin up to 85%. Furthermore, response surface methodology (RSM) with Box-Behnken design is applied to optimize the degradation conditions with varying pH, temperature (°C), and incubation time (days). The p value < 0.05 in the response surface design and analysis of variance showed the significance of the reaction parameters. The ideal conditions for Penicillium chrysogenum to break down bifenthrin (10 mgL-1) were found to be 30 °C, pH 7, and a 24 days incubation period. In eutrophic conditions and a glucose-rich media, this fungus co-metabolized bifenthrin. By hydrolytically cleaving the carboxyl ester bond, the Penicillium chrysogenum breaks down bifenthrin, as shown by the chromatogram of four metabolites from GCMS. The biodegradation of bifenthrin by strain Penicillium chrysogenum and its use in agronomic situations are now well understood as per the findings of this study.

Atlas of the microbial degradation of fluorinated pesticides

Fluorine-based agrochemicals have been benchmarked as the golden standard in pesticide development, prompting their widespread use in agriculture. As a result, fluorinated pesticides can now be found in the environment, entailing serious ecological implications due to their harmfulness and persistence. Microbial degradation might be an option to mitigate these impacts, though environmental microorganisms are not expected to easily cope with these fluoroaromatics due to their recalcitrance. Here, we provide an outlook on the microbial metabolism of fluorinated pesticides by analyzing the degradation pathways and biochemical processes involved, while also highlighting the central role of enzymatic defluorination in their productive metabolism. Finally, the potential contribution of these microbial processes for the dissipation of fluorinated pesticides from the environment is also discussed.

Aerobic degradation of 4-fluoroaniline and 2,4-difluoroaniline: performance and microbial community in response to the inocula

In this study, a distinct inoculum was investigated as an isolated variable within sequencing batch reactors via a comparison of the 4-fluoroaniline (4-FA) or 2,4-difluoroaniline (2,4-DFA) removal amounts. The inocula were derived from a treatment plant for treating pharmaceutical wastewater plus a small amount of municipal sewage (PMS), a treatment plant for treating fluoridated hydrocarbon wastewater (FHS), and a treatment plant for treating the comprehensive wastewater in an industrial park (CIS). There were slight differences among the degradation patterns of the 4-FA for the three inocula, whether during the enrichment period or the high concentration shock period. In contrast, it was observed that the degradation efficiency of 2,4-DFA initially varied with the inocula. The FHS-derived inoculum was determined to be optimal, exhibiting the earliest degradation reaction only after an acclimation of 7 days had the highest degradation rate constant of 0.519 h^-1, and had the fastest recovery time of three weeks after high concentration shock. Additionally, compared with the PMS-derived inoculum, the CIS-derived inoculum exhibited an earlier degradation reaction within three weeks, and a higher microbial diversity, but a lower shock resistance and degradation rate constant of 0.257 h^-1. High-throughput sequencing demonstrated that each final consortium was different in composition, and the microbial consortia developed well on the inoculum and substrate. In comparison of the similarity among the three 2,4-DFA enrichment cultures, the higher similarity (63.9-70.0%) among three final consortia enriching with 4-FA was observed. The results indicated that the inoculum played an important role in the degradation of FAs and the microbial bacterial communities of final consortia, and the effect extent might well depend on the fluorinated level of FAs.

Aerobic degradation of 2- and 3-fluoroaniline in mixed culture systems and microbial community analysis

Among three monofluoroanilines, 2-fluoroaniline (2-FA) and 3-fluoroaniline (3-FA) exhibit relatively poor biodegradability. This work examined their degradation characteristics in a mixed culture system and also analyzed the microorganism community. After acclimation for 58 d and 43 d, the high removal efficiency of 100% of 2-FA and 95.3% of 3-FA was obtained by adding 25 mg L^-1 of 2-FA or 3-FA to the two reactors, respectively. In addition, the high defluorination rates of 2-FA and 3-FA were observed to be 87.0% and 89.3%, respectively. The degradation kinetics showed that the maximum specific degradation rates of 2-FA and 3-FA were (21.23 ± 0.91) mg FA (g•VSS·h)^-1, and (11.75 ± 0.99) mg FA (g•VSS·h)^-1, respectively. PCR-DGGE analysis revealed that the unique bacteria degrading 2-FA were mainly composed of six genera (Novosphingobium, Bradyrhizobium, Aquaspirillum, Aminobacter, Ochrobactrum, and Labrys), and five genera that degraded 3-FA (Ochrobactrum, Aquaspirillum, Lachnobacterium, Bradyrhizobium, and Variovorax). Analysis of the key catabolic enzyme activities indicated that the simultaneous hydroxylation and dehalogenation were involved in monooxygenase elimination of 2-FA and conversion of 3-FA to 4-fluorocatechol by dioxygenase, indicating that enriched mixed cultures were effective to metabolize 2-FA or 3-FA by unconventional pathways to prevent the accumulation of toxic metabolites.

Degradation of 3-fluoroanilne by Rhizobium sp. JF-3

The interest of fluoroanilines in the environment is due to their extensive applications in industry and their low natural biodegradability. A pure bacterial strain capable of degrading 3-fluoroaniline (3-FA) as the sole source of carbon and energy was isolated from a sequencing batch reactor operating for the treatment of 3-FA. The strain (designated as JF-3) was identified by 16S rRNA gene analysis as a member of the genus Rhizobium. When grown in 3-FA medium at concentrations of 100-700 mg/L, strain JF-3 almost completely removed 3-FA within 72 h. However, the obvious cell growth inhibition was observed in cultures treated with 3-FA concentrations greater than 500 mg/L. The degradation kinetics of 3-FA were consistent with Haldane's model with the maximum degradation rate as 67.66 mg/(g dry cell h). The growth kinetics of strain JF-3 followed Andrew's model with the maximum growth rate as 30.87 h^-1. Also, strain JF-3 was able to degrade 4-fluoroaniline, aniline, and catechol, but hardly grew on 2-fluoroaniline, 2,4-dfluoroaniline, 2,3,4-trifluoroaniline, 3-fluorocatechol, and 4-fluorocatechol. Additionally, it was able to grow over a wide pH range (pH 6-10), and also showed tolerance to salinity with lower than 1.0%. This result, in combination with the enzyme assays and analysis of metabolite intermediates, indicated an unconventional pathway for 3-fluoroaniline metabolism that involved conversion to 3-aminophenol and resorcinol by monooxygenase, and which was subsequently metabolized via the ortho-cleavage pathway. To our knowledge, this is the first report on the utilization of 3-FA as a growth substrate by Rhizobium sp.

Simultaneous biodegradation of bifenthrin and chlorpyrifos by Pseudomonas sp. CB2

The degradation of bifenthrin (BF) and chlorpyrifos (CP), either together or individually, by a bacterial strain (CB2) isolated from activated sludge was investigated. Strain CB2 was identified as belonging to genus Pseudomonas based on the morphological, physiological, and biochemical characteristics and a homological analysis of the 16S rDNA sequence. Strain CB2 has the potential to degrade BF and CP, either individually or in a mixture. The optimum conditions for mixture degradation were as follows: OD_600nm = 0.5; incubation temperature = 30°C; pH = 7.0; BF-CP mixture (10 mg L^-1 of each). Under these optimal conditions, the degradation rate constants (and half-lives) were 0.4308 d^-1 (1.61 d) and 0.3377 d^-1 (2.05 d) for individual BF and CP samples, respectively, and 0.3463 d^-1 (2.00 d) and 0.2931 d^-1 (2.36 d) for the BF-CP mixture. Major metabolites of BF and CP were 2-methyl-3-biphenylyl methanol and 3,5,6-trichloro-2-pyridinol, respectively. No metabolite bioaccumulation was observed. The ability of CB2 to efficiently degrade BF and CP, particularly in a mixture, may be useful in bioremediation efforts.

Natural production of fluorinated compounds and biotechnological prospects of the fluorinase enzyme

Fluorinated compounds are finding increasing uses in several applications. They are employed in almost all areas of modern society. These compounds are all produced by chemical synthesis and their abundance highly contrasts with fluorinated molecules of natural origin. To date, only some plants and a handful of actinomycetes species are known to produce a small number of fluorinated compounds that include fluoroacetate (FA), some ω-fluorinated fatty acids, nucleocidin, 4-fluorothreonine (4-FT), and the more recently identified (2R3S4S)-5-fluoro-2,3,4-trihydroxypentanoic acid. This largely differs from other naturally produced halogenated compounds, which totals more than 5000. The mechanisms underlying biological fluorination have been uncovered after discovering the first actinomycete species, Streptomyces cattleya, that is capable of producing FA and 4-FT, and a fluorinase has been identified as the enzyme responsible for the formation of the C-F bond. The discovery of this enzyme has opened new perspectives for the biotechnological production of fluorinated compounds and many advancements have been achieved in its application mainly as a biocatalyst for the synthesis of [¹⁸F]-labeled radiotracers for medical imaging. Natural fluorinated compounds may also be derived from abiogenic sources, such as volcanoes and rocks, though their concentrations and production mechanisms are not well known. This review provides an outlook of what is currently known about fluorinated compounds with natural origin. The paucity of these compounds and the biological mechanisms responsible for their production are addressed. Due to its relevance, special emphasis is given to the discovery, characterization and biotechnological potential of the unique fluorinase enzyme.

Ralstonia mannitolilytica-Induced Septicemia and Homology Analysis in Infected Patients: 3 Case Reports

Background

Ralstonia mannitolilytica is an emerging opportunistic pathogen. Hospital outbreaks of Ralstonia spp. are mainly associated with contaminated treatment water or auxiliary instruments.

Objectives

In this report, we summarize the clinical infection characteristics of R. mannitolilytica, the drug-susceptibility testing of the bacterial strains, and the results of related infection investigations.

Patients and Methods

We retrospectively analyzed the clinical information of 3 patients with R. mannitolilytica.

Results

The patients’ primary-onset symptoms were chills and fever. The disease progressed rapidly and septic shock symptoms developed. Laboratory tests indicated progressively decreased white blood cells and platelets, as well as significant increases in certain inflammation indicators. The effect of treatment with Tazocin was good. The growth period of R. mannitolilytica in sterile distilled water was > 6 months. The pulsed-field gel electrophoresis (PFGE) results revealed that the infectious strains from these 3 patients were not the same clonal strain. This bacterium was not detected in the nosocomial infection samples.

Conclusions

Our results suggest that R. mannitolilytica-induced septicemia had an acute disease onset and rapid progression. The preferred empirical antibiotic was Tazocin. In these 3 cases, the R. mannitolilytica-induced septicemia was not due to clonal transmission.

Cometabolism of Fluoroanilines in the Presence of 4-Fluoroaniline byRalstoniasp. FD-1

A strain ofRalstoniasp. FD-1 capable of using 4-fluoroaniline (4-FA) as the sole carbon and nitrogen source was investigated for its ability to utilize 4-FA isomers (2-FA, 3-FA) and homologs (2,4-DFA, 3,4-DFA, and 2,3,4-TFA). Both 4-FA and 3-FA could be mineralized as the sole carbon and nitrogen source by FD-1. 2-FA, 2,4-DFA, 3,4-DFA, and 2,3,4-TFA could not be degraded by FD-1, respectively, and were selected as secondary substrates for cometabolism with 500 mg/L 4-FA as growth substrate. Bacterial growth (OD600), F−concentrations, and fluoroanilines contents were measured to determinate the degradation ability of 4-FA isomers and homologs by FD-1. FD-1 growth was inhibited by 2,4-DFA, 3,4-DFA, and 2,3,4-TFA at higher concentrations (400 mg/L), except for 2-FA. Complete fluoroanilines degradation was achieved while incomplete defluorination was characterized by the stoichiometric fluoride release indicating partial degradation but not total mineralization. When fluoroaniline was supplied to the resting cells of strain FD-1, a relatively effective removal was showed. Strain FD-1 had broadened application prospect of toxicity and low nutrition fluoroanilines wastewater.

Aerobic degradation study of three fluoroanilines and microbial community analysis: the effects of increased fluorine substitution

The fate of fluorinated compounds in the environment, especially polyfluorinated aromatics, is a matter of great concern. In this work, 4-Fluoroaniline (4-FA), 2,4-Difluoroanilines (2,4-DFA), and 2,3,4-Trifluoroanilines (2,3,4-TFA), were chosen as the target pollutants to study their biodegradability under aerobic conditions. The required enriched time of the mixed bacterial culture for degrading 4-FA, 2,4-DFA, and 2,3,4-TFA was 26, 51, and 165 days, respectively, which suggested that the longer enrichment time was required with the increase of fluorine substitution. At the initial concentrations of 100-200 mg L(-1), the 4-FA, 2,4-DFA, and 2,3,4-TFA could be degraded completely by the mixed bacterial culture. The maximum specific degradation rates of 4-FA, 2,4-DFA, and 2,3,4-TFA were 22.48 ± 0.55, 15.27 ± 2.04, and 8.84 ± 0.93 mg FA (g VSS h)(-1), respectively. Also, the three FAs enriched cultures showed certain potential of degrading other two FAs. The results from enzyme assay suggested the expression of meta-cleavage pathways during three FAs degradation. The denaturing gradient gel electrophoresis analysis revealed that unique bacterial communities were formed after FAs enrichment and these were principally composed of β-Proteobacteria, Oscillatoriophycideae, δ-Proteobacteria, α-Proteobacteria, Thermales, Xanthomonadales, Deinococci, Flavobacteriia, and Actinobacteridae. The Shannon-Wiener indexes in three FAs enriched culture decreased with the increase of fluorine substitution, indicating the significant effect of fluorine substitution on the microbial diversity. These findings supply important information on the fate of three FAs under aerobic environment, and the bacterial communities in their degradation systems.