Microbial detoxification of chlorpyrifos, profenofos, monocrotophos, and dimethoate by a multifaceted rhizospheric Bacillus cereus strain PM38 and its potential for the growth promotion in cotton.

Bacillus genera, especially among rhizobacteria, are known for their ability to promote plant growth and their effectiveness in alleviating several stress conditions. This study aimed to utilize indigenous Bacillus cereus PM38 to degrade four organophosphate pesticides (OPs) such as chlorpyrifos (CP), profenofos (PF), monocrotophos (MCP), and dimethoate (DMT) to mitigate the adverse effects of these pesticides on cotton crop growth. Strain PM38 exhibited distinct characteristics that set it apart from other Bacillus species. These include the production of extracellular enzymes, hydrogen cyanide, exopolysaccharides, Indol-3-acetic acid (166.8 µg/mL), siderophores (47.3 µg/mL), 1-aminocyclopropane-1-carboxylate deaminase activity (32.4 µg/mL), and phosphorus solubilization (162.9 µg/mL), all observed at higher concentrations. This strain has also shown tolerance to salinity (1200 mM), drought (20% PEG-6000), and copper and cadmium (1200 mg/L). The amplification of multi-stress-responsive genes, such as acdS, ituC, czcD, nifH, sfp, and pqqE, further confirmed the plant growth regulation and abiotic stress tolerance capability in strain PM38. Following the high-performance liquid chromatography (HPLC) analysis, the results showed striking compatibility with the first kinetic model. Strain PM38 efficiently degraded CP (98.4%), PF (99.7%), MCP (100%), and DMT (95.5%) at a concentration of 300 ppm over 48 h at 35 °C under optimum pH conditions, showing high coefficients of determination (R2) of 0.974, 0.967, 0.992, and 0.972, respectively. The Fourier transform infrared spectroscopy (FTIR) analysis and the presence of opd, mpd, and opdA genes in the strain PM38 further supported the potential to degrade OPs. In addition, inoculating cotton seedlings with PM38 improved root length under stressful conditions. Inoculation of strain PM38 reduces stress by minimizing proline, thiobarbituric acid-reactive compounds, and electrolyte leakage. The strain PM38 has the potential to be a good multi-stress-tolerant option for a biological pest control agent capable of improving global food security and managing contaminated sites.

Identification and Characterization of Bacterial Alliinase: Resource and Substrate Stereospecificity.

Limited alliinase resources cause difficulties in the biosynthesis of thiosulfinates (e.g., allicin), restricting their applications in the agricultural and food industries. To effectively biosynthesize thiosulfinates, this study aimed to excavate bacterial alliinase resources and elucidate their catalytic properties. Two bacterial cystathionine ß-lyases (MetCs) possessing high alliinase activity (>60 U mg -1) toward L-(-)-alliin were identified from Allium sativum rhizosphere isolates. Metagenomic exploration revealed that cystathionine ß-lyase from Bacillus cereus (BcPatB) possessed high activity toward both L-(±)-alliin and L-(+)-alliin (208.6 and 225.1 U mg -1), respectively. Although these enzymes all preferred l-cysteine S-conjugate sulfoxides as substrates, BcPatB had a closer phylogenetic relationship with Allium alliinases and shared several similar features with A. sativum alliinase. Interestingly, the Trp30Ile31Ala32Asp33 Met34 motif in a cuspate loop of BcPatB, especially sites 31 and 32 at the top of the motif, was modeled to locate near the sulfoxide of L-(+)-alliin and is important for substrate stereospecificity. Moreover, the stereoselectivity and activity of mutants I31V and A32G were higher toward L-(+)-alliin than those of mutant I31L/D33E toward L-(-)-alliin. Using bacterial alliinases and chemically synthesized substrates, we obtained thiosulfinates with high antimicrobial and antinematode activities that could provide insights into the protection of crops and food.

Biodegradation of polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics by floc-forming bacteria, Bacillus cereus strain SHBF2, isolated from a commercial aquafarm.

The ubiquitous proximity of the commonly used microplastic (MP) particles particularly polyethylene (PE), polypropylene (PP), and polystyrene (PS) poses a serious threat to the environment and human health globally. Biological treatment as an environment-friendly approach to counter MP pollution has recent interest when the bio-agent has beneficial functions in their ecosystem. This study aimed to utilize beneficial floc-forming bacteria Bacillus cereus SHBF2 isolated from an aquaculture farm in reducing the MP particles (PE, PP, and PS) from their environment. The bacteria were inoculated for 60 days in a medium containing MP particle as a sole carbon source. On different days of incubation (DOI), the bacterial growth analysis was monitored and the MP particles were harvested to examine their weight loss, surface changes, and alterations in chemical properties. After 60 DOI, the highest weight loss was recorded for PE, 6.87 ± 0.92%, which was further evaluated to daily reduction rate (k), 0.00118 day-1, and half-life (t1/2), 605.08 ± 138.52 days. The OD value (1.74 ± 0.008 Abs.) indicated the higher efficiency of bacteria for PP utilization, and so for the colony formation per define volume (1.04 × 1011 CFU/mL). Biofilm formation, erosions, cracks, and fragments were evident during the observation of the tested MPs using the scanning electron microscope (SEM). The formation of carbonyl and alcohol group due to the oxidation and hydrolysis by SHBF2 strain were confirmed using the Fourier transform infrared spectroscopic (FTIR) analysis. Additionally, the alterations of pH and CO2 evolution from each of the MP type ensures the bacterial activity and mineralization of the MP particles. The findings of this study have confirmed and indicated a higher degree of biodegradation for all of the selected MP particles. B. cereus SHBF2, the floc-forming bacteria used in aquaculture, has demonstrated a great potential for use as an efficient MP-degrading bacterium in the biofloc farming system in the near future to guarantee a sustainable green aquaculture production.

Screening of cellulose-degrading bacteria and optimization of cellulase production from Bacillus cereus A49 through response surface methodology.

Cellulose-degrading microorganisms hold immense significance in utilizing cellulose resources efficiently. The screening of natural cellulase bacteria and the optimization of fermentation conditions are the hot spots of research. This study meticulously screened cellulose-degrading bacteria from mixed soil samples adopting a multi-step approach, encompassing preliminary culture medium screening, Congo red medium-based re-screening, and quantification of cellulase activity across various strains. Particularly, three robust cellulase-producing strains were identified: A24 (MT740356.1 Brevibacillus borstelensis), A49 (MT740358.1 Bacillus cereus), and A61 (MT740357.1 Paenibacillus sp.). For subsequent cultivation experiments, the growth curves of the three obtained isolates were monitored diligently. Additionally, optimal CMCase production conditions were determined, keeping CMCase activity as a key metric, through a series of single-factor experiments: agitation speed, cultivation temperature, unit medium concentration, and inoculum volume. Maximum CMCase production was observed at 150 rpm/37 °C, doubling the unit medium addition, and a 5 mL inoculation volume. Further optimization was conducted using the selected isolate A49 employing response surface methodology. The software model recommended a 2.21fold unit medium addition, 36.11 °C temperature, and 4.91 mL inoculant volume for optimal CMCase production. Consequently, three parallel experiments were conducted based on predicted conditions consistently yielding an average CMCase production activity of 15.63 U/mL, closely aligning with the predicted value of 16.41 U/mL. These findings validated the reliability of the model and demonstrated the effectiveness of optimized CMCase production conditions for isolate A49.

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.

Bacterial screening in Indian coastal regions for efficient polypropylene microplastics biodegradation.

Polypropylene based medical devices significantly increased production and usage in COVID-19 pandemic states, and this material is very resilient in the environment. Thus, more than ever, rapid action is needed to reduce this pollution. This study focuses on the degradation of polypropylene microplastics (PP MPs) by unique marine bacterial strains obtained from the Thoundi (Bacillus tropicus, Bacillus cereus, Stenotrophomonas acidaminiphila, and Brucella pseudintermedia) and Rameshwaram coasts (Bacillus cereus). Those above five bacterial strains were chosen after preliminary screening of their hydrophobicity, biofilm-forming capabilities, and responsiveness to the zone of clearance technique. During the biodegradation process (28 days), the growth, metabolic activity, and viability of these five isolates were all raised. After the post-biodegradation process, the weight loss percentages of the mentioned bacterial strains treated with PP MPs gradually decreased, with values of 51.5 ± 0.5 %, 47.5 ± 0.5 %, 33 ± 1 %, 28.5 ± 0.5 and 35.5 ± 0.5 %, respectively. UV-Vis DRS and SEM analysis confirmed that bacterial strains adhering to MPs cause cracks and cavities on their surface. The degradation of PP MPs can be inferred from alterations in the FT-IR spectrum, specifically in the carbonyl group range of 1100-1700 cm-1, as well as changes in the 1H NMR spectrum, including chemical shift and proton peak pattern alterations. Bacterial strains facilitated the degradation of PP MPs through the secretion of hydrolase-categorized enzymes of protease, lipase, and esterase. The findings of this study indicate that marine bacteria may possess distinctive characteristics that facilitate the degradation of plastic waste and contribute to environmental conservation.

Expression, Characterisation, Homology Modelling and Molecular Docking of a Novel M17 Family Leucyl-Aminopeptidase from Bacillus cereus CZ.

Leucyl-aminopeptidase (LAP), an important metallopeptidase, hydrolyses amino acid residues from the N-terminus of polypeptides and proteins, acting preferentially on the peptide bond formed by N-terminus leucine. A new leucyl-aminopeptidase was found in Bacillus cereus CZ. Its gene (bclap) contained a 1485 bp ORF encoding 494 amino acids with a molecular weight of 54 kDa. The bcLAP protein was successfully expressed in E. coli BL21(DE3). Optimal activity is obtained at pH 9.0 and 58 °C. The bcLAP displays a moderate thermostability and an alkaline pH adaptation range. Enzymatic activity is dramatically enhanced by Ni2+. EDTA significantly inhibits the enzymatic activity, and bestatin and SDS also show strong inhibition. The three-dimensional model of bcLAP monomer and homohexamer is simulated byPHYRE2 server and SWISS-MODEL server. The docking of bestatin, Leu-Trp, Asp-Trp and Ala-Ala-Gly to bcLAP is performed using AutoDock4.2.5, respectively. Molecular docking results show that the residues Lys260, Asp265, Lys272, Asp283, Asp342, Glu344, Arg346, Gly372 and His437 are involved in the hydrogen bonding with the ligands and zinc ions. There may be two nucleophilic catalytic mechanisms in bcLAP, one involving His 437 or Arg346 and the other involving His437 and Arg346. The bcLAP can hydrolyse the peptide bonds in Leu-Trp, Asp-Trp and Ala-Ala-Gly.

Complete genome sequence of Bacillus cereus Z4, a biocontrol agent against tobacco black shank, isolated from the Western Pacific Ocean.

Bacillus species have been considered as promising biological control agents due to their excellent antimicrobial ability. Bacillus cereus strain Z4 was isolated from 2000 m deep sea sediments of the Western Pacific Ocean, which possesses significant antifungal activity against Phytophthora nicotianae, the pathogenic fungus of tobacco black shank disease. To reveal the underlying antifungal genetic mechanisms, here, we report the complete genomic sequence of the strain Z4. The genome has one circular chromosome of 5,664,309 bp with a G + C content of 35.31%, 109 tRNAs, and 43 rRNAs. Genomic analysis identified 10 gene clusters related to the biosynthesis of biocontrol active compounds, including bacillibactin, petrobactin, fengycin, and molybdenum cofactor. Meanwhile, 6 gene clusters were responsible for the biosynthesis of metabolites with unknown functions. Strain Z4 also contains a large number of genes encoding carbohydrate-active enzymes and secreted proteins, respectively. The whole genomic analysis of Bacillus cereus Z4 may provide a valuable reference for elucidating its biocontrol mechanism against tobacco black shank.

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.

Response surface optimization of poly-ß-hydroxybutyrate synthesized by Bacillus cereus L17 using acetic acid as carbon source.

A strain of Bacillus that can tolerate 10 g/L acetic acid and use the volatile fatty acids produced by the hydrolysis and acidification of activated sludge to produce polyhydroxyalkanoate was screened from the activated sludge of propylene oxide saponification wastewater. The strain was identified by 16S rRNA sequencing and phylogenetic tree analysis and was named Bacillus cereus L17. Various characterization methods showed that the polymer synthesized by strain L17 is poly-ß-hydroxybutyrate, which has low crystallinity, good ductility and toughness, high thermal stability and a low polydispersity coefficient. It has wide thermoplastic material operating space as well as industrial and medicinal applications. The optimal fermentation conditions were determined by single factor optimization. Then, Plackett-Burman and Box-Behnken design experiments were carried out according to the single factor optimization results, and the response surface optimization was completed. The final results were: initial pH 6.7, temperature 25 °C, and loading volume 124 mL. The verification experiment showed that the yield of poly-ß-hydroxybutyrate after optimization increased by 35.2 % compared to that before optimization.

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.

Dual inoculation with rhizosphere-promoting bacterium Bacillus cereus and beneficial fungus Peniophora cinerea improves salt stress tolerance and productivity in willow.

Utilization of rhizosphere microorganisms to improve plant growth and salt tolerance has recently attracted widespread attention. The growth and salt tolerance of willows inoculated with Bacillus cereus JYZ-SD2 and Peniophora cinerea XC were studied under different salt stress conditions. The results showed that the chlorophyll content of willow cuttings inoculated with the XC strain increased significantly by 51.27%. After salt stress of willow cuttings inoculated with B. cereus JYZ-SD2 and P. cinerea XC (solely or in combination), the amount of sodium in the roots from the epidermis to the pericycle decreased and the content of sodium in the pericycle was significantly lower than that of the uninoculated willow, while the proportion of potassium increased. Willow cuttings inoculated with microorganisms showed increased activity of SOD and POD. At the salt concentration of 100 mmol/L, the highest SOD activity was found in B. cereus JYZ-SD2-inoculated willows, with 59.88% increase compared to uninoculated willows; the highest POD activity was found in P. cinerea XC and B. cereus JYZ-SD2 co-inoculated willows, with 51.05% increase compared to uninoculated willows. The Na-K-ATPase and Ca-Mg-ATPase activities of inoculated P. cinerea XC willow cuttings were also 59.38% and 60% higher than that of uninoculated willows, respectively. The qPCR analysis showed that the expression of vp2 gene in the microorganism-inoculated willow leaves was always higher than that in willow alone. The expression of vp2 gene in P. cinerea XC-inoculated willow cuttings was 270.81% higher than that in uninoculated willows. Further observation of the ultrastructure of root cells under salt stress revealed that most of the vesicles in the root tip cells of willow were intact and secreted phagocytic vesicles to absorb sodium ions in the cytoplasm. This study shows that the combined beneficial fungi and rhizosphere-promoting bacteria inoculation technology as a practical biotechnological approach to enhance the growth of willows in salt-affected soils.

Feather-Degrading Bacillus cereus HD1: Genomic Analysis and Its Optimization for Keratinase Production and Feather Degradation.

Keratinase is an important enzyme that is used to degrade feather wastes produced by poultry industries and slaughterhouses that accumulate rapidly over time. The search for keratinase-producing microorganisms is important to potentially substitute physicochemical treatments of feather waste. In this study, the genome of Bacillus cereus HD1 and its keratinolytic prowess was investigated. The whole-genome shotgun size is 5,668,864 bp consisting of 6083 genes, 69 tRNAs, and 10 rRNAs. The genomic analyses revealed 15 potential keratinase genes and other enzymes that might assist keratin degradation, such as disulfide reductase and cysteine dioxygenase. The optimal conditions for feather degradation and keratinase production by B. cereus HD1 such as incubation time, pH, temperature, yeast extract, and glycerol concentrations were determined to be 5 days, pH 8, 37 °C, 0.05% (w/v), and 0.1% (v/v), respectively. Under optimized conditions, B. cereus HD1 exhibited feather degradation of 65%, with bacterial growth and maximum keratinase activity of 1.3 × 1011 CFU/mL and 41 U/mL, respectively, after 5 days of incubation in a feather basal medium. The findings obtained from this study may facilitate further research into utilizing B. cereus HD1 as a prominent keratinolytic enzymes production host and warrant potential biotechnological applications.

Differential proteomic analysis under pesticides stress and normal conditions in Bacillus cereus 2D.

A potential pesticide degrading bacterial isolate (2D), showing maximum tolerance (450 mg∙L-1) for cypermethrin, fipronil, imidacloprid and sulfosulfuron was recovered from a pesticide contaminated agricultural field. The isolate degraded cypermethrin, imidacloprid, fipronil and sulfosulfuron in minimal salt medium with 94, 91, 89 and 86% respectively as revealed by high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis after 15 days of incubation. Presence of cyclobutane, pyrrolidine, chloroacetic acid, formic acid and decyl ester as major intermediate metabolites of cypermethrin biodegradation was observed in gas chromatography mass spectrometry (GC-MS) analysis. Results based on 16S rDNA sequencing, and phylogenetic analysis showed maximum similarity of 2D with Bacillus cereus (Accession ID: MH341691). Stress responsive and catabolic/pesticide degrading proteins were over expressed in the presence of cypermethrin in bacteria. Enzymatic kinetics of laccase was deduced in the test isolate under normal and pesticide stress conditions which suggested that the production of enzyme was induced significantly in pesticide stress (163 µg.µL-1) as compare to normal conditions(29 µg.µL-1) while the Km value was decreased in pesticides stress condition (Km = 10.57 mM) and increases in normal condition (Km = 14.33 mM).Amplification of laccase gene showed a major band of 1200bp. The present study highlights on the potential of 2D bacterial strain i.e., high tolerance level of pesticide, effective biodegradation rate, and presence of laccase gene in bacterial strain 2D, could become a potential biological agent for large-scale treatment of mixture of pesticide (cypermethrin, fipronil, imidacloprid and sulfosulfuron) in natural environment (soil and water).

Cysteine Proteome Reveals Response to Endogenous Oxidative Stress in Bacillus cereus.

At the end of exponential growth, aerobic bacteria have to cope with the accumulation of endogenous reactive oxygen species (ROS). One of the main targets of these ROS is cysteine residues in proteins. This study uses liquid chromatography coupled to high-resolution tandem mass spectrometry to detect significant changes in protein abundance and thiol status for cysteine-containing proteins from Bacillus cereus during aerobic exponential growth. The proteomic profiles of cultures at early-, middle-, and late-exponential growth phases reveals that (i) enrichment in proteins dedicated to fighting ROS as growth progressed, (ii) a decrease in both overall proteome cysteine content and thiol proteome redox status, and (iii) changes to the reduced thiol status of some key proteins, such as the transition state transcriptional regulator AbrB. Taken together, our data indicate that growth under oxic conditions requires increased allocation of protein resources to attenuate the negative effects of ROS. Our data also provide a strong basis to understand the response mechanisms used by B. cereus to deal with endogenous oxidative stress.

Implication of a Key Region of Six Bacillus cereus Genes Involved in Siroheme Synthesis, Nitrite Reductase Production and Iron Cluster Repair in the Bacterial Response to Nitric Oxide Stress.

Bacterial response to nitric oxide (NO) is of major importance for bacterial survival. NO stress is a main actor of the eukaryotic immune response and several pathogenic bacteria have developed means for detoxification and repair of the damages caused by NO. However, bacterial mechanisms of NO resistance by Gram-positive bacteria are poorly described. In the opportunistic foodborne pathogen Bacillus cereus, genome sequence analyses did not identify homologs to known NO reductases and transcriptional regulators, such as NsrR, which orchestrate the response to NO of other pathogenic or non-pathogenic bacteria. Using a transcriptomic approach, we investigated the adaptation of B. cereus to NO stress. A cluster of 6 genes was identified to be strongly up-regulated in the early phase of the response. This cluster contains an iron-sulfur cluster repair enzyme, a nitrite reductase and three enzymes involved in siroheme biosynthesis. The expression pattern and close genetic localization suggest a functional link between these genes, which may play a pivotal role in the resistance of B. cereus to NO stress during infection.

Biosorption of organic dye Acridine orange from aqueous solution using dry biomass of Bacillus cereus M116.

Acridine orange (AO), a basic carcinogenic fluorochrome dye, is used in the industry for staining. In this study, Gram-positive bacteria, Bacillus cereus M116 (MTCC 5521) dry biomass was tested as an eco-friendly, easily available, and cheap biosorbent for the AO dye removal. We obtained optimum biosorption of AO at a biomass concentration of 0.25 g/L and initial dye concentrations of 50-400 mg/L at neutral to basic pH within the 300 min contact time. Kinetics analysis of the biosorption process was best fitted with the pseudo-second-order reaction type. We also performed the isotherm analysis to predict the nature of the reaction taking place, which was found to follow the Redlich Peterson isotherm model with high determination coefficients. The maximum sorption capacity was 210.46 mg/g of dry biomass. The differential FTIR spectroscopic analysis of pristine and AO-treated Bacillus cereus M116 cells suggested the potential involvement of carbonyl, hydroxyl, and amine groups in the biosorption process. Also, the scanning electron microscopy of the cells after AO removal confirmed a gross surface alteration compared to the untreated cells. Furthermore, Response Surface Model (RSM) analysis with the three-way ANOVA test confirms statistically significant interactions between the dye concentration, pH, and temperature with the biosorption capacity (p < 0.001). Hence, the dry biomass of Bacillus cereus M116 was found to be an effective bio-remedial for the AO removal.

Optimization for biogenic microbial synthesis of silver nanoparticles through response surface methodology, characterization, their antimicrobial, antioxidant, and catalytic potential.

Silver is a poisonous but precious heavy metal that has widespread application in various biomedical and environmental divisions. Wide-ranging usage of the metal has twisted severe environmental apprehensions. Henceforth there is a cumulative call for the progress of modest, low-cost and, the ecological method for remediation of silver. In the present study, Bacillus cereus was isolated from contaminated soil. Various experimental factors like the amount of AgNO3, inoculum size, temperature, time, and pH were improved by using central composite design (CCD) grounded on response surface methodology (RSM). Optimized values for AgNO3 (1 mM) 10 ml, inoculum size (Bacillus cereus) 8.7 ml, temperature 48.5 °C, time 69 h, and pH 9 showed in the form of optimized ramps. The formed nanoparticles stayed characterized by UV-visible spectrophotometer, Scanning Electron Microscopy, Fourier transform infra-red spectrometry, particle size analyzer, and X-ray diffraction. The particle size ranges from 5 to 7.06 nm with spherical form. The antimicrobial effectiveness of synthesized nanoparticles was tested contrary to five multidrug resistant microbial strains, Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Salmonella enterica, Porteus mirabilis by disc diffusion method. The minimum inhibitory concentrations and minimum lethal concentrations were detected by the broth macro dilution method. 2,2-diphenyl-1-picrylhydrazyl-hydrate (DPPH) was used to check the free radical scavenging ability of biogenic silver nanoparticles. Similarly, anti-radical activity was checked by 2,2'-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic Acid (ABTS) with varying time intervals. Catalytic potential of biosynthesized silver nanoparticles was also investigated.

Rearrangement of N-Terminal α-Helices of Bacillus thuringiensis Cry1Ab Toxin Essential for Oligomer Assembly and Toxicity.

Cry proteins produced by Bacillus thuringiensis are pore-forming toxins that disrupt the membrane integrity of insect midgut cells. The structure of such pore is unknown, but it has been shown that domain I is responsible for oligomerization, membrane insertion and pore formation activity. Specifically, it was proposed that some N-terminal α-helices are lost, leading to conformational changes that trigger oligomerization. We designed a series of mutants to further analyze the molecular rearrangements at the N-terminal region of Cry1Ab toxin that lead to oligomer assembly. For this purpose, we introduced Cys residues at specific positions within α-helices of domain I for their specific labeling with extrinsic fluorophores to perform Föster resonance energy transfer analysis to fluorescent labeled Lys residues located in Domains II-III, or for disulfide bridges formation to restrict mobility of conformational changes. Our data support that helix α-1 of domain I is cleaved out and swings away from the toxin core upon binding with Manduca sexta brush border membrane vesicles. That movement of helix α-2b is also required for the conformational changes involved in oligomerization. These observations are consistent with a model proposing that helices α-2b and α-3 form an extended helix α-3 necessary for oligomer assembly of Cry toxins.