Structures and activation mechanism of the Gabija anti-phage system.

Prokaryotes have evolved intricate innate immune systems against phage infection1-7. Gabija is a highly widespread prokaryotic defence system that consists of two components, GajA and GajB8. GajA functions as a DNA endonuclease that is inactive in the presence of ATP9. Here, to explore how the Gabija system is activated for anti-phage defence, we report its cryo-electron microscopy structures in five states, including apo GajA, GajA in complex with DNA, GajA bound by ATP, apo GajA-GajB, and GajA-GajB in complex with ATP and Mg2+. GajA is a rhombus-shaped tetramer with its ATPase domain clustered at the centre and the topoisomerase-primase (Toprim) domain located peripherally. ATP binding at the ATPase domain stabilizes the insertion region within the ATPase domain, keeping the Toprim domain in a closed state. Upon ATP depletion by phages, the Toprim domain opens to bind and cleave the DNA substrate. GajB, which docks on GajA, is activated by the cleaved DNA, ultimately leading to prokaryotic cell death. Our study presents a mechanistic landscape of Gabija activation.

Dissecting the role of the MS-ring protein FliF in Bacillus cereus flagella-related functions.

The flagellar MS-ring, uniquely constituted by FliF, is essential for flagellar biogenesis and functionality in several bacteria. The aim of this study was to dissect the role of FliF in the Gram-positive and peritrichously flagellated Bacillus cereus. We demonstrate that fliF forms an operon with the upstream gene fliE. In silico analysis of B. cereus ATCC 14579 FliF identifies functional domains and amino acid residues that are essential for protein functioning. The analysis of a ΔfliF mutant of B. cereus, constructed in this study using an in frame markerless gene replacement method, reveals that the mutant is unexpectedly able to assemble flagella, although in reduced amounts compared to the parental strain. Nevertheless, motility is completely abolished by fliF deletion. FliF deprivation causes the production of submerged biofilms and affects the ability of B. cereus to adhere to gastrointestinal mucins. We additionally show that the fliF deletion does not compromise the secretion of the three components of hemolysin BL, a toxin secreted through the flagellar type III secretion system. Overall, our findings highlight the important role of B. cereus FliF in flagella-related functions, being the protein required for complete flagellation, motility, mucin adhesion, and pellicle biofilms.

Design of a two functional permeable reactive barrier for synergistic enzymatic and microbial bioremediation of phenol-contaminated waters: laboratory column evaluation : Enzymatic and microbial bioremediation of phenol in a bilayer permeable reactive barrier.

The present study aimed to develop a system using a combination of enzymatic and microbial degradation techniques for removing phenol from contaminated water. In our prior research, the HRP enzyme extracted from horseradish roots was utilized within a core-shell microcapsule to reduce phenolic shock, serving as a monolayer column. To complete the phenol removal process, a second column containing degrading microorganisms was added to the last column in this research. Phenol-degrading bacteria were isolated from different microbial sources on a phenolic base medium. Additionally, encapsulated calcium peroxide nanoparticles were used to provide dissolved oxygen for the microbial population. Results showed that the both isolated strains, WC1 and CC1, were able to completely remove phenol from the contaminated influent water the range within 5 to 7 days, respectively. Molecular identification showed 99.8% similarity for WC1 isolate to Stenotrophomonas rizophila strain e-p10 and 99.9% similarity for CC1 isolate to Bacillus cereus strain IAM 12,605. The results also indicated that columns using activated sludge as a microbial source had the highest removal rate, with the microbial biofilm completely removing 100% of the 100 mg/L phenol concentration in contaminated influent water after 40 days. Finally, the concurrent use of core-shell microcapsules containing enzymes and capsules containing Stenotrophomonas sp. WC1 strain in two continuous column reactors was able to completely remove phenol from polluted water with a concentration of 500 mg/L for a period of 20 days. The results suggest that a combination of enzymatic and microbial degrading systems can be used as a new system to remove phenol from polluted streams with higher concentrations of phenol by eliminating the shock of phenol on the microbial population.

Unveiling the biointerfaces characteristics and removal pathways of Cr(â ¥) in Bacillus cereus FNXJ1-2-3 for the Cr(â ¥)-to-Cr(0) conversion.

Although less toxic than hexavalent chromium, Cr (Ⅲ) species still pose a threat to human health. The Cr (Ⅵ) should be converted to Cr (0) instead of Cr (Ⅲ), which is still involved in biological detoxification filed. Herein, for the first time, it was found that Cr(Ⅵ) can be reduced into Cr(0) by Bacillus cereus FNXJ1-2-3, a way to completely harmless treatment of Cr(Ⅵ). The bacterial strain exhibited excellent performance in the reduction, sorption, and accumulation of Cr(Ⅵ) and Cr (Ⅲ). XPS etching characterization inferred that the transformation of Cr(Ⅵ) into Cr(0) followed a reduction pathway of Cr(Ⅵ)→Cr (Ⅲ)→metallic Cr(0), in which at least two secretory chromium reductases (ECrⅥ→Ⅲ and ECrⅢ→0) worked. Under the optimum condition, the yield ratio of Cr(0)/Cr (Ⅲ) reached 33.90%. In addition, the interfacial interactions, ion channels, chromium reductases, and external electron donors also contributed to the Cr(Ⅵ)/Cr(0) transformation. Findings of this study indicate that Bacillus cereus FNXJ1-2-3 is a promising bioremediation agent for Cr(Ⅵ) pollution control.

Microbial degradation mechanism and pathway of the insecticide thiamethoxam by isolated Bacillus Cereus from activated sludge.

The high water solubility and ecotoxicity of thiamethoxam (TMX) is a potential hazard to ecosystems and human health. Here, a strain of Bacillus cereus with high TMX degradation activity was isolated from the sediment of the A2O process in the wastewater treatment plant and was able to utilize TMX as its sole carbon source. Under different environmental conditions, the degradation efficiency of TMX by Bacillus cereus-S1 (strain S1) ranged from 41.0% to 68.9% after 216 h. The optimum degradation conditions were DO = 3.5 mg/L and pH 9.0. The addition of an appropriate carbon-to-nitrogen ratio could accelerate the degradation of TMX. A plausible biodegradation pathway has been proposed based on the identified metabolites and their corresponding degradation pathways. TMX can be directly converted into Clothianidin (CLO), TMX-dm-hydroxyl and TMX-Urea by a series of reactions such as demethylation, oxadiazine ring cleavage and C=N substitution by hydroxy group. The main products were TMX-dm-hydroxyl and TMX-Urea, the amount of CLO production is relatively small. This study aims to provide a new approach for efficient degradation of TMX; furthermore, strain S1 is a promising biological source for in situ remediation of TMX contamination.

Impact of Bacillus cereus SPB-10 on Growth Promotion of Wheat (Triticum aestivum L.) Under Arsenic-Contaminated Soil.

This study investigates the impact of bacteria on arsenic reduction in wheat plants, highlighting the potential of microbe-based eco-friendly strategies for plant growth. In the present study, bacterial isolate SPB-10 was survived at high concentration against both form of arsenic (As3+ and As5+). SPB-10 produced 5.2 g/L and 11.3 g/L of exo-polysaccharide at 20 ppm of As3+ and As5+, respectively, whereas qualitative examination revealed the highest siderophores ability. Other PGP attributes such as IAA production were recorded 52.12 mg/L and 95.82 mg/L, phosphate solubilization was 90.23 mg/L and 129 mg/L at 20 ppm of As3+ and As5+, respectively. Significant amount of CAT, APX, and Proline was also observed at 20 ppm of As3+ and As5+ in SPB-10. Isolate SPB-10 was molecularly identified as Bacillus cereus through 16S rRNA sequencing. After 42 days, wheat plants inoculated with SPB-10 had a 25% increase in shoot length and dry weight, and 26% rise in chlorophyll-a pigment under As5+ supplemented T4 treatment than control. Reducing sugar content was increased by 24% in T6-treated plants compared to control. Additionally, SPB-10 enhanced the content of essential nutrients (NPK), CAT, and APX in plant's-leaf under both As3+ and As5+ stressed conditions after 42 days. The study found that arsenic uptake in plant roots and shoots decreased in SPB-10-inoculated plants, with the maximum reduction observed in As5+ treated plants. Bio-concentration factor-BCF was reduced by 90.89% in SPB-10-inoculated treatment T4 after 42 days. This suggests that Bacillus cereus-SPB-10 may be beneficial for plant growth in arsenic-contaminated soil.

Bacillus cereus G2 alleviate salt stress in Glycyrrhiza uralensis Fisch. by balancing the downstream branches of phenylpropanoids and activating flavonoid biosynthesis.

The salinity environment is one of the biggest threats to Glycyrrhiza uralensis Fisch. (G. uralensis) growth, resulting from the oxidative stress caused by excess reactive oxygen species (ROS). Flavonoids are the main pharmacodynamic composition and help maintain ROS homeostasis and mitigate oxidative damage in G. uralensis in the salinity environment. To investigate whether endophytic Bacillus cereus G2 can improve the salt-tolerance of G. uralensis through controlling flavonoid biosynthesis, the transcriptomic and physiological analysis of G. uralensis treated by G2 in the saline environment was conducted, focused on flavonoid biosynthesis-related pathways. Results uncovered that salinity inhibited flavonoids synthesis by decreasing the activities of phenylalanine ammonialyase (PAL) and 4-coumarate-CoA ligase (4CL) (42% and 39%, respectively) due to down-regulated gene Glyur000910s00020578 at substrate level, and then decreasing the activities of chalcone isomerase (CHI) and chalcone synthase (CHS) activities (50% and 42%, respectively) due to down-regulated genes Glyur006062s00044203 and Glyur000051s00003431, further decreasing isoliquiritigenin content by 53%. However, salt stress increased liquiritin content by 43%, which might be a protective mechanism of salt-treated G. uralensis seedlings. Interestingly, G2 enhanced PAL activity by 27% whereas reduced trans-cinnamate 4-monooxygenase (C4H) activity by 43% which could inhibit lignin biosynthesis but promote flavonoid biosynthesis of salt-treated G. uralensis at the substrate level. G2 decreased shikimate O-hydroxycinnamoyltransferase (HCT) activity by 35%, increased CHS activity by 54% through up-regulating the gene Glyur000051s00003431 encoding CHS, and increased CHI activity by 72%, thereby decreasing lignin (34%) and liquiritin (24%) content, but increasing isoliquiritigenin content (35%), which could mitigate oxidative damage and changed salt-tolerance mechanism of G. uralensis.

A High-Homology Region Provides the Possibility of Detecting ß-Barrel Pore-Forming Toxins from Various Bacterial Species.

The pathogenicity of many bacteria, including Bacillus cereus and Staphylococcus aureus, depends on pore-forming toxins (PFTs), which cause the lysis of host cells by forming pores in the membranes of eukaryotic cells. Bioinformatic analysis revealed a region homologous to the Lys171-Gly250 sequence in hemolysin II (HlyII) from B. cereus in over 600 PFTs, which we designated as a "homologous peptide". Three ß-barrel PFTs were used for a detailed comparative analysis. Two of them-HlyII and cytotoxin K2 (CytK2)-are synthesized in Bacillus cereus sensu lato; the third, S. aureus α-toxin (Hla), is the most investigated representative of the family. Protein modeling showed certain amino acids of the homologous peptide to be located on the surface of the monomeric forms of these ß-barrel PFTs. We obtained monoclonal antibodies against both a cloned homologous peptide and a 14-membered synthetic peptide, DSFNTFYGNQLFMK, as part of the homologous peptide. The HlyII, CytK2, and Hla regions recognized by the obtained antibodies, as well as an antibody capable of suppressing the hemolytic activity of CytK2, were identified in the course of this work. Antibodies capable of recognizing PFTs of various origins can be useful tools for both identification and suppression of the cytolytic activity of PFTs.

Enhanced biodegradation of phenol under Cr(VI) stress by microbial collaboration and potential application of machine learning for phenol biodegradation.

Cr(VI) and phenol commonly coexist in wastewater, posing a great threat to the environment and human health. However, it is still a challenge for microorganisms to degrade phenol under high Cr(VI) stress. In this study, the phenol-degrading strain Bacillus cereus ZWB3 was co-cultured with the Cr(VI)-reducing strain Bacillus licheniformis MZ-1 to enhance phenol biodegradation under Cr(Ⅵ) stress. Compared with phenol-degrading strain ZWB3, which has weak tolerance to Cr(Ⅵ), and Cr(Ⅵ)-reducing strain MZ-1, which has no phenol-degrading ability, the co-culture of two strains could significantly increase the degraded rate and capacity of phenol. In addition, the co-cultured strains exhibited phenol degradation ability over a wide pH range (7-10). The reduced content of intracellular proteins and polysaccharides produced by the co-cultured strains contributed to the enhancement of phenol degradation and Cr(Ⅵ) tolerance. The determination coefficients R2, RMSE, and MAPE showed that the BP-ANN model could predict the degradation of phenol under various conditions, which saved time and economic cost. The metabolic pathway of microbial degradation of phenol was deduced by metabolic analysis. This study provides a valuable strategy for wastewater treatment containing Cr(Ⅵ) and phenol.

An alkaline protease from Bacillus cereus NJSZ-13 can act as a pathogenicity factor in infection of pinewood nematode.

Endophytic bacteria are an important biological control for nematodes. We isolated the nematicidal Bacillus cereus NJSZ-13 from healthy Pinus elliottii trunks. Bioassay experiments showed killing of all tested nematodes by proteins from the NJSZ-13 culture filtrate within 72 h. Degradation of the nematode cuticles was observed, suggesting the action of extracellular bacterial enzymes. The responsible protease was purified by ammonium sulfate precipitation, hydrophobic interaction chromatography, ion-exchange chromatography, and SDS-PAGE. The protease had a molecular weight of 28 kDa and optimal activity at 55 °C and pH 9, indicating an alkaline protease. The study suggests the potential for using this B. cereus NJSZ-13 strain protease to prevent pinewood nematode infection.

SigB modulates expression of novel SigB regulon members via Bc1009 in non-stressed and heat-stressed cells revealing its alternative roles in Bacillus cereus.

BACKGROUND: The Bacillus cereus Sigma B (SigB) dependent general stress response is activated via the two-component RsbKY system, which involves a phosphate transfer from RsbK to RsbY. It has been hypothesized that the Hpr-like phosphocarrier protein (Bc1009) encoded by bc1009 in the SigB gene cluster may play a role in this transfer, thereby acting as a regulator of SigB activation. Alternatively, Bc1009 may be involved in the activation of a subset of SigB regulon members. RESULTS: We first investigated the potential role of bc1009 to act as a SigB regulator but ruled out this possibility as the deletion of bc1009 did not affect the expression of sigB and other SigB gene cluster members. The SigB-dependent functions of Bc1009 were further examined in B. cereus ATCC14579 via comparative proteome profiling (backed up by transcriptomics) of wt, Δbc1009 and ΔsigB deletion mutants under heat stress at 42 °C. This revealed 284 proteins displaying SigB-dependent alterations in protein expression levels in heat-stressed cells, including a subgroup of 138 proteins for which alterations were also Bc1009-dependent. Next to proteins with roles in stress defense, newly identified SigB and Bc1009-dependent proteins have roles in cell motility, signal transduction, transcription, cell wall biogenesis, and amino acid transport and metabolism. Analysis of lethal stress survival at 50 °C after pre-adaptation at 42 °C showed intermediate survival efficacy of Δbc1009 cells, highest survival of wt, and lowest survival of ΔsigB cells, respectively. Additional comparative proteome analysis of non-stressed wt and mutant cells at 30 °C revealed 96 proteins with SigB and Bc1009-dependent differences in levels: 51 were also identified under heat stress, and 45 showed significant differential expression at 30 °C. This includes proteins with roles in carbohydrate/ion transport and metabolism. Overlapping functions at 30 °C and 42 °C included proteins involved in motility, and ΔsigB and Δbc1009 cells showed reduced motility compared to wt cells in swimming assays at both temperatures. CONCLUSION: Our results extend the B. cereus SigB regulon to > 300 members, with a novel role of SigB-dependent Bc1009 in the activation of a subregulon of  > 180 members, conceivably via interactions with other transcriptional regulatory networks.

Bacillus cereus: A review of "fried rice syndrome" causative agents.

"Fried rice syndrome" originated from the first exposure to a fried rice dish contaminated with Bacillus cereus. This review compiles available data on the prevalence of B. cereus outbreak cases that occurred between 1984 and 2019. The outcome of B. cereus illness varies dramatically depending on the pathogenic strain encounter and the host's immune system. B. cereus causes a self-limiting, diarrheal illness caused by heat-resistant enterotoxin proteins, and an emetic illness caused by the deadly toxin named cereulide. The toxins together with their extrinsic factors are discussed. The possibility of more contamination of B. cereus in protein-rich food has also been shown. Therefore, the aim of this review is to summarize the available data, focusing mainly on B. cereus physiology as the causative agent for "fried rice syndrome." This review emphasizes the prevalence of B. cereus in starchy food contamination and outbreak cases reported, the virulence of both enterotoxins and emetic toxins produced, and the possibility of contaminated in protein-rich food. The impact of emetic or enterotoxin-producing B. cereus on public health cannot be neglected. Thus, it is essential to constantly monitor for B. cereus contamination during food handling and hygiene practices for food product preparation.

Bacillus cereus extracellular vesicles act as shuttles for biologically active multicomponent enterotoxins.

BACKGROUND: Extracellular vesicles (EVs) from Gram-positive bacteria have gained considerable importance as a novel transport system of virulence factors in host-pathogen interactions. Bacillus cereus is a Gram-positive human pathogen, causing gastrointestinal toxemia as well as local and systemic infections. The pathogenicity of enteropathogenic B. cereus has been linked to a collection of virulence factors and exotoxins. Nevertheless, the exact mechanism of virulence factor secretion and delivery to target cells is poorly understood. RESULTS: Here, we investigate the production and characterization of enterotoxin-associated EVs from the enteropathogenic B. cereus strain NVH0075-95 by using a proteomics approach and studied their interaction with human host cells in vitro. For the first time, comprehensive analyses of B. cereus EV proteins revealed virulence-associated factors, such as sphingomyelinase, phospholipase C, and the three-component enterotoxin Nhe. The detection of Nhe subunits was confirmed by immunoblotting, showing that the low abundant subunit NheC was exclusively detected in EVs as compared to vesicle-free supernatant. Cholesterol-dependent fusion and predominantly dynamin-mediated endocytosis of B. cereus EVs with the plasma membrane of intestinal epithelial Caco2 cells represent entry routes for delivery of Nhe components to host cells, which was assessed by confocal microscopy and finally led to delayed cytotoxicity. Furthermore, we could show that B. cereus EVs elicit an inflammatory response in human monocytes and contribute to erythrocyte lysis via a cooperative interaction of enterotoxin Nhe and sphingomyelinase. CONCLUSION: Our results provide insights into the interaction of EVs from B. cereus with human host cells and add a new layer of complexity to our understanding of multicomponent enterotoxin assembly, offering new opportunities to decipher molecular processes involved in disease development. Video Abstract.

Identification of a novel cyclomaltodextrinase annotated as a neopullulanase in the genome of Bacillus cereus.

Bacillus cereus is a rod-shaped, gram-positive, motile, and ß-hemolytic soil bacterium. B. cereus is an opportunistic pathogen, often responsible for human foodborne illness that is caused by ingestion of starchy foods with symptoms of diarrhea and vomiting. Among the numerous amylolytic enzymes in the genome of the pathogen, the one annotated as a putative neopullulanase (NPase) was cloned and its biochemical properties were characterized in this study. The corresponding gene encoded an enzyme of 586 amino acids with a predicted molecular mass of 68.25 kDa. The putative NPase shared 43.7-59.2% of identity with NPases, cyclomaltodextrinases (CDases), and maltogenic amylases from various bacteria, but shared very low similarity with other amylolytic enzymes of B. cereus. The optimal pH and temperature of the enzyme was 6.5 and 37 â„ƒ, respectively. The enzyme activity was decreased by the cations tested in this study and completely inhibited by Co2+ and Cu2+. The purified enzyme showed substrate preference in the order of α-CD > ß-CD > starch > maltodextrin > γ-CD and hydrolyzed them mainly to maltose. However, it did not hydrolyze maltose, pullulan, and glycogen. The enzyme was designated herein as a CDase of B. cereus (BcCDase). Furthermore, the enzyme could transfer the sugars released from CDs and maltotriose to acceptor molecules. BcCDase was likely to be involved in the maltodextrin metabolism in B. cereus.

Characterization of the biosurfactant production and enzymatic potential of bacteria isolated from an oil-contaminated saline soil.

Biosurfactants are amphiphilic compounds with extensive applications in oily contaminated environments to remove hydrocarbons. Moreover, enzymes such as laccase and manganese peroxidase are responsible for the oxidation of a variety of phenolic compounds and aromatic amines. Therefore, in the present study, bacteria with the potential to produce biosurfactants and enzymes (namely, laccase, manganese peroxidase, and endoglucanase carboxymethyl cellulose (CMCase)) were isolated from petroleum oil-contaminated soil. From 15 isolated bacteria, three isolates were selected as the best producers of biosurfactants according to the related tests, such as tests for surface tension reduction. These three bacteria indicated tolerance to a salinity test and were classified as resistant and very resistant. The isolates 3, 12, 13, and 14 showed positive results for the degradation of guaiacol, phenol red, and carboxymethylcellulose, as well as the decoloration of methylene blue by the creation of a clear halo around the bacterial colony. Upon the quantitation of the laccase and manganese peroxidase activities, 22.58 U/L and 21.81 U/L, respectively, were measured by isolate 13. Furthermore, CMCase activity was recorded with 0.057436 U/ml belonging to isolate 14. Bacterial strains with appreciable laccase, peroxidase, CMCase activity, and biosurfactant production potentials were identified through 16S rDNA sequence analysis as Bacillus sp. (isolate 3), Bacillus toyonensis (isolate 12), Bacillus cereus (isolate 13), and Bacillus tropicus (isolate 14), and their nucleotide sequences were deposited in the GenBank. The potentials for the industrial applicability of the biosurfactants and enzymes abound, and production needs to be optimized by the selected bacterial strains.

Purification and biochemical characterization of phytase from Bacillus cereus isolated from gastrointestinal tract of African giant snail (Achatina fulica).

Phytases are specialized enzymes meant for phytic acid degradation. They possess ability to prevent phytic acid indigestion, including its attendant environmental pollution. This study was aimed at investigating biochemical properties of purified phytase of B. cereus isolated from Achatina fulica. Phytase produced from Bacillus cereus that exhibited optimal phytate degrading-ability of all the bacteria isolated was purified in a three-step purification. The biochemical properties of the purified enzyme were also determined. The phytase homogeny of approximately 45 kDa exhibited 12.8-purification fold and 1.6% yield with optima phytate degrading efficiency and maximum stability at pH 7 and 50 °C. Remaining activity of 52 and 47% obtained between 60 and 70 °C after 2 h further established thermostability of the purified phytase. Mg2+ and Zn2+ enhanced phytate hydrolysis by the enzyme, while Na+ showed mild inhibition but Hg2+ severely inhibited the enzymatic activity. Km and Vmax were estimated to be 0.11 mM and 55.6 µmol/min/mL, displaying enzyme-high substrate affinity and catalytic efficiency, respectively. Phytase purified from Bacillus cereus, isolated from African giant snails, has shown excellent characteristics suitable for phytic acid hydrolysis and could be employed in industrial and biotechnological applications.

Endophytic bacteria isolated from Urtica dioica L.- preliminary screening for enzyme and polyphenols production.

Endophytes, especially those isolated from herbal plants, may act as a reservoir of a variety of secondary metabolites exhibiting biological activity. Some endophytes express the ability to produce the same bioactive compounds as their plant hosts, making them a more sustainable industrial supply of these substances. Urtica dioica L. (common stinging nettle) is a synanthropic plant that is widely used in herbal medicine due to the diversity of bioactive chemicals it contains, e.g., polyphenols, which demonstrate anti-inflammatory, antioxidant, and anti-cancerous capabilities. This study aimed at isolating endophytic bacteria from stinging nettles for their bioactive compounds. The endophytic isolates were identified by both biochemical and molecular methods (16S rRNA) and investigated for enzymes, biosurfactants, and polyphenols production. Each of the isolated bacterial strains was capable of producing biosurfactants and polyphenols. However, three of the isolated endophytes, identified as two strains of Bacillus cereus and one strain of Bacillus mycoides, possessed the greatest capacity to produce biosurfactants and polyphenols. The derivatized extracts from culture liquid showed the 1.633 mol l-1 (9.691 mg l-1) concentration of polyphenol compounds. Therefore, the present study signifies that endophytic B. cereus and B. mycoides isolated from Urtica dioica L. could be a potential source of biosurfactants and polyphenols. However, further study is required to understand the mechanism of the process and achieve efficient polyphenol production by endophytic bacteria.

Antioxidants improve ß-cypermethrin degradation by alleviating oxidative damage and increasing bioavailability by Bacillus cereus GW-01.

Microbial degradation of pesticide residues has the potential to reduce their hazards to human and environmental health. However, in some cases, degradation can activate pesticides, making them more toxic to microbes. Here we report on the ß-cypermethrin (ß-CY) toxicity to Bacillus cereus GW-01, a recently described ß-CY degrader, and effects of antioxidants on ß-CY degradation. GW-01 exposed to ß-CY negatively affected the growth rate. The highest maximum specific growth rate (µm) appeared at 25 mg/L ß-CY. ß-CY induced the oxidative stress in GW-01. The activities of superoxide dismutase (SOD), catalyse (CAT), and glutathione-S-transferase (GST) were significantly higher than that in control (p < 0.01); but they are decreased as growth phase pronged, which is contrary to the ß-CY degradation by GW-01 cells obtaining from various growth phase. Ascorbic acid (Vc), tea polyphenols (TP), and adenosine monophosphate (AMP) improved the degradation through changing the physiological property of GW-01. TP and AMP prompted the expression of gene encoding ß-CY degradation in GW-01, while Vc does the opposite. Biofilm formation was significantly inhibited by ß-CY, while was significantly enhanced by certain concentrations of TP and AMP (p < 0.05); while cell surface hydrophobicity (CSH) was negatively associated with ß-CY concentrations from 25 to 100 mg/L, and these 4 antioxidants all boosted the CSH. Cells grown with ß-CY had lower levels of saturated fatty acids but increased levels of some unsaturated and branched fatty acids, and these antioxidants alleviated the FA composition changes and gene expression related with FA metabolism. We also mined transcriptome analyses at lag, logarithmic, and stationary phases, and found that ß-CY induced oxidative stress. The objective of this study was to elaborate characteristics in relation to the microbial resistance of pesticide poisoning and the efficiency of pesticide degradation, and to provide a promising method for improving pesticide degradation by microbes.

Identification of Quorum Quenching N-Acyl Homoserine Lactonases from Priestia aryabhattai J1D and Bacillus cereus G Isolated from the Rhizosphere.

Several pathogenic bacteria communicate using N-acyl homoserine lactone (AHL) as a quorum sensing (QS) molecule. The process of interfering with the QS system is known as quorum quenching (QQ), it is an effective tool to control QS-dependent virulence in pathogens. In the present study, rhizosphere bacterial isolates were screened for their ability to produce AHL lactonase enzyme as QQ molecules, which hydrolyses AHL signalling molecules and consequently blocks the QS system. Potent N-hexanoyl-l-homoserine lactone (C6HSL) hydrolytic QQ activity was detected in rhizosphere isolates namely Bacillus cereus G and Priestia aryabhattai J1D. The cell-free supernatant of the bacterial isolates indicated a reduction in biofilm formation in the human pathogens Vibrio cholerae, Pseudomonas aeruginosa, and Staphylococcus aureus without inhibiting cells, signifying their biocontrol property. Furthermore, liquid chromatography high resolution mass spectrometry analysis confirmed C6HSL hydrolytic activity by AHL lactonase produced by these rhizosphere isolates. Also, the aiiA homologous gene from the bacterial isolates showed similarity with the aiiA lactonase gene from Bacillus species, which was further confirmed by homology modelling. In silico structure analysis by comparing with the structure of Bacillus revealed the similarity in the active site, indicating the same degradation pattern. Based on available reported data, the present study indicates the first report of the presence of the aiiA lactonase gene in P. aryabhattai.

Target search and recognition mechanisms of glycosylase AlkD revealed by scanning FRET-FCS and Markov state models.

DNA glycosylase is responsible for repairing DNA damage to maintain the genome stability and integrity. However, how glycosylase can efficiently and accurately recognize DNA lesions across the enormous DNA genome remains elusive. It has been hypothesized that glycosylase translocates along the DNA by alternating between a fast but low-accuracy diffusion mode and a slow but high-accuracy mode when searching for DNA lesions. However, the slow mode has not been successfully characterized due to the limitation in the spatial and temporal resolutions of current experimental techniques. Using a newly developed scanning fluorescence resonance energy transfer (FRET)-fluorescence correlation spectroscopy (FCS) platform, we were able to observe both slow and fast modes of glycosylase AlkD translocating on double-stranded DNA (dsDNA), reaching the temporal resolution of microsecond and spatial resolution of subnanometer. The underlying molecular mechanism of the slow mode was further elucidated by Markov state model built from extensive all-atom molecular dynamics simulations. We found that in the slow mode, AlkD follows an asymmetric diffusion pathway, i.e., rotation followed by translation. Furthermore, the essential role of Y27 in AlkD diffusion dynamics was identified both experimentally and computationally. Our results provided mechanistic insights on how conformational dynamics of AlkD-dsDNA complex coordinate different diffusion modes to accomplish the search for DNA lesions with high efficiency and accuracy. We anticipate that the mechanism adopted by AlkD to search for DNA lesions could be a general one utilized by other glycosylases and DNA binding proteins.