Unveiling the CoA mediated salicylate catabolic mechanism in Rhizobium sp. X9.

Salicylate is a typical aromatic compound widely distributed in nature. Microbial degradation of salicylate has been well studied and salicylate hydroxylases play essential roles in linking the peripheral and ring-cleavage catabolic pathways. The direct hydroxylation of salicylate catalyzed by salicylate-1-hydroxylase or salicylate-5-hydroxylase has been well studied. However, the CoA mediated salicylate 5-hydroxylation pathway has not been characterized in detail. Here, we elucidate the molecular mechanism of the reaction in the conversion of salicylate to gentisate in the carbaryl-degrading strain Rhizobium sp. X9. Three enzymes (salicylyl-CoA ligase CehG, salicylyl-CoA hydroxylase CehH and gentisyl-CoA thioesterase CehI) catalyzed the conversion of salicylate to gentisate via a route, including CoA thioester formation, hydroxylation and thioester hydrolysis. Further analysis indicated that genes cehGHI are also distributed in other bacteria from terrestrial environment and marine sediments. These genomic evidences highlight the role of this salicylate degradation pathway in the carbon cycle of soil organic compounds and marine sediments. Our findings of this three-step strategy enhanced the current understanding of CoA mediated degradation of salicylate.

A conserved rhizobial peptidase that interacts with host-derived symbiotic peptides.

In the Medicago truncatula-Sinorhizobium meliloti symbiosis, chemical signaling initiates rhizobial infection of root nodule tissue, where a large portion of the bacteria are endocytosed into root nodule cells to function in nitrogen-fixing organelles. These intracellular bacteria are subjected to an arsenal of plant-derived nodule-specific cysteine-rich (NCR) peptides, which induce the physiological changes that accompany nitrogen fixation. NCR peptides drive these intracellular bacteria toward terminal differentiation. The bacterial peptidase HrrP was previously shown to degrade host-derived NCR peptides and give the bacterial symbionts greater fitness at the expense of host fitness. The hrrP gene is found in roughly 10% of Sinorhizobium isolates, as it is carried on an accessory plasmid. The objective of the present study is to identify peptidase genes in the core genome of S. meliloti that modulate symbiotic outcome in a manner similar to the accessory hrrP gene. In an overexpression screen of annotated peptidase genes, we identified one such symbiosis-associated peptidase (sap) gene, sapA (SMc00451). When overexpressed, sapA leads to a significant decrease in plant fitness. Its promoter is active in root nodules, with only weak expression evident under free-living conditions. The SapA enzyme can degrade a broad range of NCR peptides in vitro.

Hydrolase CehA and a Novel Two-Component 1-Naphthol Hydroxylase CehC1C2 are Responsible for the Two Initial Steps of Carbaryl Degradation in Rhizobium sp. X9.

Carbaryl is a widely used carbamate pesticide in agriculture. The strain Rhizobium sp. X9 possesses the typical carbaryl degradation pathway in which carbaryl is mineralized via 1-naphthol, salicylate, and gentisate. In this study, we cloned a carbaryl hydrolase gene cehA and a novel two-component 1-naphthol hydroxylase gene cehC1C2. CehA mediates carbaryl hydrolysis to 1-naphthol and CehC1, an FMNH2 or FADH2-dependent monooxygenase belonging to the HpaB superfamily, and hydroxylates 1-naphthol in the presence of reduced nicotinamide-adenine dinucleotide (FMN)/flavin adenine dinucleotide (FAD), and the reductase CehC2. CehC1 has the highest amino acid similarity (58%) with the oxygenase component of a two-component 4-nitrophenol 2-monooxygenase, while CehC2 has the highest amino acid similarity (46%) with its reductase component. CehC1C2 could utilize both FAD and FMN as the cofactor during the hydroxylation, although higher catalytic activity was observed with FAD as the cofactor. The optimal molar ratio of CehC1 to CehC2 was 2:1. The Km and Kcat/Km values of CehC1 for 1-naphthol were 74.71 ± 16.07 µM and (8.29 ± 2.44) × 10-4 s-1·µM-1, respectively. Moreover, the enzyme activities and substrate spectrum between CehC1C2 and previously reported 1-naphthol hydroxylase McbC were compared. The results suggested that McbC had a higher 1-naphthol hydroxylation activity, while CehC1C2 had a broader substrate spectrum.

Thermomagneto-Responsive Smart Biocatalysts for Malonyl-Coenzyme A Synthesis.

Smart biocatalysts, in which enzymes are conjugated to stimuli-responsive polymers, have gained considerable attention because of their catalytic switchability and recyclability. Although many systems have been developed, they require separate laboratory techniques for their recovery, making them unsuitable for many practical applications. To address these issues, we designed a thermomagneto-responsive biocatalyst by immobilizing an enzyme on the terminal of thermo-responsive polymer brushes tethered on magnetic nanoparticle (NP) clusters. The concept is demonstrated by a system consisting of iron oxide NPs, poly(N-isopropyl-acrylamide), and a malonyl-Coenzyme A synthetase (MatB). By using free malonate and coenzyme A (CoA), the designed catalyst exhibits adequate activity for the production of malonyl-CoA. Thanks to the use of a magnetic NP cluster, whose magnetic moment is high, this system is fully recoverable under the magnetic field at above 32 °C because of the collapse of the thermo-responsive polymer shell in the clusters. In addition, the recycled catalyst maintains moderate activity even after three cycles, and it also shows excellent catalytic switchability, that is, negligible catalytic activity at 25 °C because of the blockage of the active sites of the enzyme by the extended hydrophilic polymer chains but great catalytic activity at a temperatures above the lower critical solution temperature at which the enzymes are exposed to the reaction medium because of the thermo-responsive contraction of polymer chains. Because the azide functionality in our system can be easily functionalized depending upon our need, such catalytically switchable, fully recoverable, and recyclable multiresponsive catalytic systems can be of high relevance for other cell-free biosynthetic approaches.

A novel way to synthesize pantothenate in bacteria involves ß-alanine synthase present in uracil degradation pathway.

Pantothenate is an indispensable vitamin precursor of the synthesis of coenzyme A (CoA), a key metabolite required in over 100 metabolic reactions. ß-Alanine (ß-ala) is an indispensable component of pantothenate. Due to the metabolic relevance of this pathway, we assumed that orthologous genes for ß-alanine synthesis would be present in the genomes of bacteria, archaea, and eukaryotes. However, comparative genomic studies revealed that orthologous gene replacement and loss of synteny occur at high frequency in panD genes. We have previously reported the atypical plasmid-encoded location of the pantothenate pathway genes panC and panB (two copies) in R. etli CFN42. This study also revealed the unexpected absence of a panD gene encoding the aspartate decarboxylase enzyme (ADC), required for the synthesis of ß-ala. The aim of this study was to identify the source of ß-alanine in Rhizobium etli CFN42. In this study, we present a bioinformatic analysis and an experimental validation demonstrating that the source of ß-ala in this R. etli comes from ß-alanine synthase, the last enzyme of the uracil degradation pathway.

Rhizobium glycinendophyticum sp. nov., isolated from roots of Glycine max (Linn. Merr.).

A Gram-stain-negative, rod-shaped and aerobic bacterium, designated CL12T, was isolated from roots of Glycine max (Linn. Merr.) collected from an experimental field in the campus of South China Agricultural University, PR China (22°58'46″S, 110°51'10″E). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CL12T belongs to the genus Rhizobium, closely related to Rhizobium wuzhouense W44T (99.3%), followed by Rhizobium rosettiformans W3T (98.0%) and Rhizobium ipomoeae Shin9-1T (97.9%). The results of analysis of sequences of four housekeeping genes (recA, atpD, rpoB and glnA) also revealed strain CL12T to be closely related to R. wuzhouense W44T with the similarities 91.0%, 95.0%, 94.2% and 90.5%, respectively. The major fatty acid of strain CL12T was Summed Feature 8 (C18:1ω7c and/or C18:1ω6c). Strain CL12T had not the nodulation genes (nodC and nodA) and nitrogenase reductase gene (nifH), and could not cause formation of nodule on soybean. The draft genome size of strain CL12T was 4.84 Mbp with a genomic DNA G + C content of 61.1 mol%. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) of strain CL12T and R. wuzhouense W44T were 27.4% and 84.7%, respectively. Based on genomic, phenotypic and phylogenetic analysis, strain CL12T is suggested to represent a new species of the genus Rhizobium, for which the name Rhizobium glycinendophyticum sp. nov. is proposed. The type strain is CL12T (=GDMCC 1.1597T = KACC 21281T).

Theoretical analyses on enantiospecificity of L-2-haloacid dehalogenase (DehL) from Rhizobium sp. RC1 towards 2-chloropropionic acid.

Dehalogenases continue to garner interest of the scientific community due to their potential applications in bioremediation of halogen-contaminated environment and in synthesis of various industrially relevant products. Example of such enzymes is DehL, an L-2-haloacid dehalogenase (EC 3.8.1.2) from Rhizobium sp. RC1 that catalyses the specific cleavage of halide ion from L-2-halocarboxylic acids to produce the corresponding D-2-hydroxycarboxylic acids. Recently, the catalytic residues of DehL have been identified and its catalytic mechanism has been fully elucidated. However, the enantiospecificity determinants of the enzyme remain unclear. This information alongside a well-defined catalytic mechanism are required for rational engineering of DehL for substrate enantiospecificity. Therefore, using quantum mechanics/molecular mechanics and molecular mechanics Poisson-Boltzmann surface area calculations, the current study theoretically investigated the molecular basis of DehL enantiospecificity. The study found that R51L mutation cancelled out the dehalogenation activity of DehL towards it natural substrate, L-2-chloropropionate. The M48R mutation, however introduced a new activity towards D-2-chloropropionate, conveying the possibility of inverting the enantiospecificity of DehL from L-to d-enantiomer with a minimum of two simultaneous mutations. The findings presented here will play important role in the rational design of DehL dehalogenase for improving substrate utility.

Succinate irrepressible periplasmic glucose dehydrogenase of Rhizobium sp. Td3 and SN1 contributes to its phosphate solubilization ability.

Td3 and SN1 are phosphate-solubilizing nodule rhizobia of Cajanus cajan and Sesbania rostrata, respectively. They solubilized 423 µg/mL and 428 µg/mL phosphate from tricalcium phosphate through the secretion of 19.2 mM and 29.6 mM gluconic acid, respectively, when grown in 100 mM glucose. However, 90% and 80% reduction in phosphate solubilization coupled to the production of 40 mM (Td3) and 28.2 mM (SN1) gluconic acid was observed when the two isolates were grown in 50 mM succinate + 50 mM glucose. Our results illustrate the role of succinate irrepressible glucose dehydrogenase (gcd) in phosphate solubilization and the role of succinate: proton symport in succinate-mediated repression of phosphate solubilization in these rhizobia. Calcium ion supplementation reduced the 88% and 72% repression in P solubilization to 18% and 9% in Td3 and SN1, respectively, coupled to a reduction in media pH from 6.8 to 4.9 in Td3 and 6.3 to 4.8 in SN1. Hence, repression had no genetic basis and is purely due to the biochemical interplay of protons and other cations.

Cloning and expression of d-glucoside 3-dehydrogenase from Rhizobium sp. S10 in Escherichia coli and its application for d-gulose production.

The novel isolated Rhizobium sp. S10 was identified as d-glucoside 3-dehydrogenase (G3DH) producing microbe. Therefore, the gene encoding for G3DH from Rhizobium sp. S10 was cloned and overexpressed in Escherichia coli strain JM109 as a soluble enzyme complex. The recombinant G3DH (rG3DH) was purified with relatively high specific activity of 38.54 U/mg compared to the previously characterized and cloned G3DHs. The purified rG3DH showed the highest activity at pH 7.0, 40 °C toward cellobiose. It can also oxidize a broad range of mono-disaccharides including saccharide derivatives. The glycosides oxidizing activity combined with chemical reaction, could produce d-gulose from lactitol via 3-ketolactitol.

Extender Unit Promiscuity and Orthogonal Protein Interactions of an Aminomalonyl-ACP Utilizing Trans-Acyltransferase from Zwittermicin Biosynthesis.

Trans-acting acyltransferases (trans-ATs) are standalone enzymes that select and deliver extender units to polyketide synthase assembly lines. Accordingly, there is interest in leveraging trans-ATs as tools to regioselectively diversify polyketide structures. Yet, little is known regarding the extender unit and acyl carrier protein (ACP) specificity of trans-ATs, particularly those that utilize unusual ACP-linked extender units. For example, the biosynthesis of the antibiotic zwittermicin involves the trans-AT ZmaF, which is responsible for installing a rare ACP-linked aminomalonyl extender unit. Here, we developed a method to access a panel of non-natural and non-native ACP-linked extender units and used it to probe the promiscuity of ZmaF, revealing one of the most promiscuous ATs characterized to date. Furthermore, we demonstrated that ZmaF is highly orthogonal with respect to its ACP specificity, and the ability of ZmaF to trans-complement noncognate PKS modules was also explored. Together, these results set the stage for further engineering ZmaF as a tool for polyketide diversification.

Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restriction, and AMPylating enzymes

Background: The whole-genome sequences of nine Rhizobium species were evaluated using different in silico molecular techniques such as AFLP-PCR, restriction digest, and AMPylating enzymes. The entire genome sequences were aligned with progressiveMauve and visualized by reconstructing phylogenetic tree using NTSYS pc 2.11X. The "insilico.ehu.es" was used to carry out in silico AFLP-PCR and in silico restriction digest of the selected genomes. Post-translational modification (PTM) and AMPylating enzyme diversity between the proteome of Rhizobium species were determined by novPTMenzy. Results: Slight variations were observed in the phylogeny based on AFLP-PCR and PFGE and the tree based on whole genome. Results clearly demonstrated the presence of PTMs, i.e., AMPylation with the GS-ATasE (GlnE), Hydroxylation, Sulfation with their domain, and Deamidation with their specific domains (AMPylating enzymes) GS-ATasE (GlnE), Fic, and Doc (Phosphorylation); Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase; Sulfotransferase; and CNF (Cytotoxic Necrotizing Factors), respectively. The results pertaining to PTMs are discussed with regard to functional diversities reported in these species. Conclusions: The phylogenetic tree based on AFLP-PCR was slightly different from restriction endonuclease- and PFGE-based trees. Different PTMs were observed in the Rhizobium species, and the most prevailing type of PTM was AMPylation with the domain GS-ATasE (GlnE). Another type of PTM was also observed, i.e., Hydroxylation and Sulfation, with the domains Asparagine_hydroxylase and Collagen_prolyl_lysyl_hydroxylase and Sulfotransferase, respectively. The deamidation type of PTM was present only in Rhizobium sp. NGR234. How to cite: Qureshi MA, Pervez MT, Babar ME, et al. Genomic comparisons of Rhizobium species using in silico AFLP-PCR, endonuclease restrictions and ampylating enzymes.

Deciphering the catalytic amino acid residues of l-2-haloacid dehalogenase (DehL) from Rhizobium sp. RC1: An in silico analysis.

The l-2-haloacid dehalogenases (EC 3.8.1.2) specifically cleave carbon-halogen bonds in the L-isomers of halogenated organic acids. These enzymes have potential applications for the bioremediation and synthesis of various industrial products. One such enzyme is DehL, the l-2-haloacid dehalogenase from Rhizobium sp. RC1, which converts the L-isomers of 2-halocarboxylic acids into the corresponding D-hydroxycarboxylic acids. However, its catalytic mechanism has not been delineated, and to enhance its efficiency and utility for environmental and industrial applications, knowledge of its catalytic mechanism, which includes identification of its catalytic residues, is required. Using ab initio fragment molecular orbital calculations, molecular mechanics Poisson-Boltzmann surface area calculations, and classical molecular dynamic simulation of a three-dimensional model of DehL-l-2-chloropropionic acid complex, we predicted the catalytic residues of DehL and propose its catalytic mechanism. We found that when Asp13, Thr17, Met48, Arg51, and His184 were individually replaced with an alanine in silico, a significant decrease in the free energy of binding for the DehL-l-2-chloropropionic acid model complex was seen, indicating the involvement of these residues in catalysis and/or structural integrity of the active site. Furthermore, strong inter-fragment interaction energies calculated for Asp13 and L-2-chloropropionic acid, and for a water molecule and His184, and maintenance of the distances between atoms in the aforementioned pairs during the molecular dynamics run suggest that Asp13 acts as the nucleophile and His184 activates the water involved in DehL catalysis. The results of this study should be important for the rational design of a DehL mutant with improved catalytic efficiency.

The Crystal Structure of a Bacterial l-Arabinonate Dehydratase Contains a [2Fe-2S] Cluster.

We present a novel crystal structure of the IlvD/EDD family enzyme, l-arabinonate dehydratase from Rhizobium leguminosarum bv. trifolii (RlArDHT, EC 4.2.1.25), which catalyzes the conversion of l-arabinonate to 2-dehydro-3-deoxy-l-arabinonate. The enzyme is a tetramer consisting of a dimer of dimers, where each monomer is composed of two domains. The active site contains a catalytically important [2Fe-2S] cluster and Mg2+ ion and is buried between two domains, and also at the dimer interface. The active site Lys129 was found to be carbamylated. Ser480 and Thr482 were shown to be essential residues for catalysis, and the S480A mutant structure showed an unexpected open conformation in which the active site was more accessible for the substrate. This structure showed the partial binding of l-arabinonate, which allowed us to suggest that the alkoxide ion form of the Ser480 side chain functions as a base and the [2Fe-2S] cluster functions as a Lewis acid in the elimination reaction.

The active site structure and catalytic mechanism of arsenite oxidase.

Arsenite oxidase is thought to be an ancient enzyme, originating before the divergence of the Archaea and the Bacteria. We have investigated the nature of the molybdenum active site of the arsenite oxidase from the Alphaproteobacterium Rhizobium sp. str. NT-26 using a combination of X-ray absorption spectroscopy and computational chemistry. Our analysis indicates an oxidized Mo(VI) active site with a structure that is far from equilibrium. We propose that this is an entatic state imposed by the protein on the active site through relative orientation of the two molybdopterin cofactors, in a variant of the Rây-Dutt twist of classical coordination chemistry, which we call the pterin twist hypothesis. We discuss the implications of this hypothesis for other putatively ancient molybdopterin-based enzymes.

Improvement of the Stabilization and Activity of Protocatechuate 3,4-Dioxygenase Isolated from Rhizobium sp. LMB-1 and Immobilized on Fe3O4 Nanoparticles.

Protocatechuate 3,4-dioxygenase (P34O), which is isolated from Rhizobium sp. LMB-1, catalyzes the ring cleavage step in the metabolism of aromatic compounds, and has great potential for environmental bioremediation. However, its structure is very sensitive to different environmental factors, which weaken its activity. Immobilization of the enzyme can improve its stability, allow reusability, and reduce operation costs. In this work, the relative molecular mass of the native P34O enzyme was determined to be 500 kDa by gel filtration chromatography on Sephadex G-200, and the enzyme was immobilized onto (3-aminopropyl) triethoxysilane-modified Fe3O4 nanoparticles (NPs) by the glutaraldehyde method. The optimum pH of immobilized and free P34O was unaffected, but the optimum temperature of immobilized P34O increased from 60 to 70 °C, and the thermal stability of immobilized P34O was better than that of the free enzyme and showed higher enzymatic activity at 60 and 70 °C. In addition, with the exception of Fe3+, most metal ions and organic chemicals could not improve the activity of free and immobilized P34O. The kinetic parameters of the immobilized P34O were higher than those of the free enzyme, and immobilized P34O on Fe3O4 NPs could be reused ten times without a remarkable decrease in enzymatic activity.

High yield production of Rhizobium NodB chitin deacetylase and its use for in vitro synthesis of lipo-chitinoligosaccharide precursors.

Lipo-chitinoligosaccharides (LCOs) are key molecules for the establishment of plant-microorganisms symbiosis. Interactions of leguminous crops with nitrogen-fixing rhizobial bacteria involve Nod factors, while Myc-LCOs improve the association of most plants with arbuscular mycorrhizal fungi. Both Nod factors and Myc-LCOs are composed of a chitinoligosaccharide fatty acylated at the non-reducing end accompanied with various substituting groups. One straightforward way to access LCOs is starting from chitin hydrolysate, an abundant polysaccharide found in crustacean shells, followed by regioselective enzymatic cleavage of an acetyl group from the non-reducing end of chitin tetra- or pentaose, and subsequent chemical introduction of N-acyl group. In the present work, we describe the in vitro synthesis of LCO precursors on preparative scale. To this end, Sinorhizobium meliloti chitin deacetylase NodB was produced in high yield in E. coli as a thioredoxin fusion protein. The recombinant enzyme was expressed in soluble and catalytically active form and used as an efficient biocatalyst for N-deacetylation of chitin tetra- and pentaose.

Direct Raman Spectroscopic Measurements of Biological Nitrogen Fixation under Natural Conditions: An Analytical Approach for Studying Nitrogenase Activity.

Biological N2 fixation is a major input of bioavailable nitrogen, which represents the most frequent factor limiting the agricultural production throughout the world. Especially, the symbiotic association between legumes and Rhizobium bacteria can provide substantial amounts of nitrogen (N) and reduce the need for industrial fertilizers. Despite its importance in the global N cycle, rates of biological nitrogen fixation have proven difficult to quantify. In this work, we propose and demonstrate a simple analytical approach to measure biological N2 fixation rates directly without a proxy or isotopic labeling. We determined a mean N2 fixation rate of 78 ± 5 µmol N2 (g dry weight nodule)-1 h-1 of a Medicago sativa-Rhizobium consortium by continuously analyzing the amount of atmospheric N2 in static environmental chambers with Raman gas spectroscopy. By simultaneously analyzing the CO2 uptake and photosynthetic plant activity, we think that a minimum CO2 mixing ratio might be needed for natural N2 fixation and only used the time interval above this minimum CO2 mixing ratio for N2 fixation rate calculations. The proposed approach relies only on noninvasive measurements of the gas phase and, given its simplicity, indicates the potential to estimate biological nitrogen fixation of legume symbioses not only in laboratory experiments. The same methods can presumably also be used to detect N2 fluxes by denitrification from ecosystems to the atmosphere.

Real-time PCR detection of aldoxime dehydratase genes in nitrile-degrading microorganisms.

Aldoxime dehydratase catalyses the conversion of aldoximes to their corresponding nitriles. Utilization of the aldoxime-nitrile metabolising enzyme pathway can facilitate the move towards a greener chemistry. In this work, a real-time PCR assay was developed for the detection of aldoxime dehydratase genes in aldoxime/nitrile metabolising microorganisms which have been purified from environmental sources. A conventional PCR assay was also designed allowing gene confirmation via sequencing. Aldoxime dehydratase genes were identified in 30 microorganisms across 11 genera including some not previously shown to harbour the gene. The assay displayed a limit of detection of 1 pg/µL DNA or 7 CFU/reaction. This real-time PCR assay should prove valuable in the high-throughput screening of micro-organisms for novel aldoxime dehydratase genes towards pharmaceutical and industrial applications.

Multi-template homology-based structural model of L-2-haloacid dehalogenase (DehL) from Rhizobium sp. RC1.

Dehalogenases are of high interest due to their potential applications in bioremediation and in synthesis of various industrial products. DehL is an L-2-haloacid dehalogenase (EC 3.8.1.2) that catalyses the cleavage of halide ion from L-2-halocarboxylic acid to produce D-2-hydroxycarboxylic acid. Although DehL utilises the same substrates as the other L-2-haloacid dehalogenases, its deduced amino acid sequence is substantially different (<25%) from those of the rest L-2-haloacid dehalogenases. To date, the 3D structure of DehL is not available. This limits the detailed understanding of the enzyme's reaction mechanism. The present work predicted the first homology-based model of DehL and defined its active site. The monomeric unit of the DehL constitutes α/ß structure that is organised into two distinct structural domains: main and subdomains. Despite the sequence disparity between the DehL and other L-2-haloacid dehalogenases, its structural model share similar fold as the experimentally solved L-DEX and DehlB structures. The findings of the present work will play a crucial role in elucidating the molecular details of the DehL functional mechanism.

Rhizobacteria with nematicide aptitude: enzymes and compounds associated.

The use of rhizobacteria to control plant parasitic nematodes has been widely studied. Currently, the research focuses on bacteria-nematode interactions that can mitigate this complex microbiome in agriculture. Various enzymes, toxins and metabolic by-products from rhizobacteria antagonize plant parasitic nematodes, and many different modes of action have been proposed. Hydrolytic enzymes, primarily proteases, collagenases and chitinases, have been related to the nematicide effect in rhizobacteria, proving to be an important factor involved in the degradation of different chemical constituents of nematodes at distinct developmental stages. Exuded metabolites may also alter the nematode-plant recognition process or create a hostile environment for nematodes in the rhizosphere. Specific bacteria strains responsible for the production of toxins, such as Cry proteins, are one of the strategies used by rhizobacteria. Characterization of the rhizobacteria mode of action could strengthen the development of commercial products to control populations of plant parasitic nematodes. This review aims to provide an overview of different enzymes and compounds produced by rhizobacteria related to the process of antagonism to plant-parasitic nematodes.