-
Critical Reviews in Microbiology 2004Over the years it has been important for humans to control the populations of harmful insects and insecticides have been used for this purpose in agricultural and... (Review)
Review
Over the years it has been important for humans to control the populations of harmful insects and insecticides have been used for this purpose in agricultural and horticultural sectors. Synthetic insecticides, owing to their various side effects, have been widely replaced by biological insecticides. In this review we attempt to describe three bacterial species that are known to produce insecticidal toxins of tremendous biotechnological, agricultural, and economic importance. Bacillus thuringiensis (BT) accounts for 90% of the bioinsecticide market and it produces insecticidal toxins referred to as delta endotoxins. The other two bacteria belong to the genera Photorhabdus and Xenorhabdus, which are symbiotically associated with entomopathogenic nematodes of the families Heterorhabditidae and Steinernematidae respectively. Whereas, Xenorhabdus and Photorhabdus exist in a mutualistic association with the entomopathogenic nematodes, BT act alone. BT formulations are widely used in the field against insects; however, over the years there has been a gradual development of insect resistance against BT toxins. No resistance against Xenorhabdus or Photorhabdus has been reported to date. More recently BT transgenic crops have been prepared; however, there are growing concerns about the safety of these genetically modified crops. Nematodal formulations are also used in the field to curb harmful insect populations. Resistance development to entomopathogenic nematodes is unlikely due to the physical macroscopic nature of infection. Xenorhabdus and Photorhabdus transgenes have not yet been prepared; but are predicted to be available in the near future. In this review we start with an overview of the synthetic insecticides and then discuss Bacillus thuringiensis, Xenorhabdus nematophilus, and Photorhabdus luminescens in greater detail.
Topics: Agriculture; Animals; Bacillus thuringiensis; Bacterial Toxins; Insecta; Pest Control, Biological; Photorhabdus; Xenorhabdus
PubMed: 15116762
DOI: 10.1080/10408410490270712 -
The Journal of Biological Chemistry Apr 2017Members of the gammaproteobacterial genus share mutualistic relationships with nematodes, and the pairs infect a wide swath of insect larvae. species produce a family...
Members of the gammaproteobacterial genus share mutualistic relationships with nematodes, and the pairs infect a wide swath of insect larvae. species produce a family of stilbenes, with two major components being 3,5-dihydroxy-4-isopropyl--stilbene (compound 1) and its stilbene epoxide (compound 2). This family of molecules harbors antimicrobial and immunosuppressive activities, and its pathway is responsible for producing a nematode "food signal" involved in nematode development. However, stilbene epoxidation biosynthesis and its biological roles remain unknown. Here, we identified an orphan protein (Plu2236) from that catalyzes stilbene epoxidation. Structural, mutational, and biochemical analyses confirmed the enzyme adopts a fold common to FAD-dependent monooxygenases, contains a tightly bound FAD prosthetic group, and is required for the stereoselective epoxidation of compounds 1 and 2. The epoxidase gene was dispensable in a nematode-infective juvenile recovery assay, indicating the oxidized compound is not required for the food signal. The epoxide exhibited reduced cytotoxicity toward its producer, suggesting this may be a natural route for intracellular detoxification. In an insect infection model, we also observed two stilbene-derived metabolites that were dependent on the epoxidase. NMR, computational, and chemical degradation studies established their structures as new stilbene-l-proline conjugates, prolbenes A (compound 3) and B (compound 4). The prolbenes lacked immunosuppressive and antimicrobial activities compared with their stilbene substrates, suggesting a metabolite attenuation mechanism in the animal model. Collectively, our studies provide a structural view for stereoselective stilbene epoxidation and functionalization in an invertebrate animal infection model and provide new insights into stilbene cellular detoxification.
Topics: Animals; Anti-Infective Agents; Biological Products; Catalysis; Chromatography, High Pressure Liquid; Crystallography, X-Ray; DNA Mutational Analysis; Epoxy Compounds; Gene Deletion; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Immunosuppressive Agents; Magnetic Resonance Spectroscopy; Molecular Conformation; Mutation; Photorhabdus; Protein Folding; Rhabditoidea; Stereoisomerism; Stilbenes; Symbiosis
PubMed: 28246174
DOI: 10.1074/jbc.M116.762542 -
Organic Letters Sep 2021Herein, we report the total synthesis of the phosphorylated zwitterionic trisaccharide repeating unit of subsp. 3240. The efficient route involves regio- and...
Herein, we report the total synthesis of the phosphorylated zwitterionic trisaccharide repeating unit of subsp. 3240. The efficient route involves regio- and stereoselective assembly of trisaccharide with rare deoxyamino sugar AAT at the nonreducing end, late stage oxidation, and installation of a phosphate linker on the trisaccharide. The total synthesis was completed via a longest linear sequence of 24 steps in 6.5% overall yield.
Topics: Molecular Structure; Phosphorylation; Photorhabdus; Trisaccharides
PubMed: 34459612
DOI: 10.1021/acs.orglett.1c02487 -
International Journal of Systematic and... Mar 2019Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17 and MEX47-22, were isolated from the digestive system of Heterorhabditis atacamensis and...
Photorhabdus khanii subsp. guanajuatensis subsp. nov., isolated from Heterorhabditis atacamensis, and Photorhabdus luminescens subsp. mexicana subsp. nov., isolated from Heterorhabditis mexicana entomopathogenic nematodes.
Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17 and MEX47-22, were isolated from the digestive system of Heterorhabditis atacamensis and Heterorhabditis mexicana entomopathogenic nematodes, respectively. Their 16S rRNA gene sequences suggest that strains MEX20-17 and MEX47-22 belong to the γ-Proteobacteria and to the genus Photorhabdus. Deeper analyses using housekeeping-gene-based and whole-genome-based phylogenetic reconstruction suggest that MEX20-17 is closely related to Photorhabdus khanii and that MEX47-22 is closely related to Photorhabdus luminescens. Sequence similarity scores confirm these observations: MEX20-17 and P. khanii DSM 3369 share 98.9 % nucleotide sequence identity (NSI) of concatenated housekeeping genes, 70.4 % in silico DNA-DNA hybridization (isDDH) and 97 % orthologous average nucleotide identity (orthoANI); and MEX47-22 and P. luminescens ATCC 29999 share 98.9 % NSI, 70.6 % isDDH and 97 % orthoANI. Physiological characterization indicates that both strains differ from all validly described Photorhabdus species and from their more closely related taxa. We therefore propose to classify MEX20-17 and MEXT47-22 as new subspecies within P. khanii and P. luminescens, respectively. Hence, the following names are proposed for these strains: Photorhabdus khanii subsp. guanajuatensis subsp. nov. with the type strain MEX20-17 (=LMG 30372=CCOS 1191) and Photorhabdus luminescenssubsp. mexicana subsp. nov. with the type strain MEX47-22 (=LMG 30528=CCOS 1199). These propositions automatically create Photorhabdus khanii subsp. khanii subsp. nov. with DSM 3369 as the type strain (currently classified as P. khanii), and Photorhabdus luminescenssubsp. luminescenssubsp. nov. with ATCC 29999 as the type strain (currently classified as P. luminescens).
Topics: Animals; Bacterial Typing Techniques; Base Composition; DNA, Bacterial; Fatty Acids; Mexico; Nucleic Acid Hybridization; Photorhabdus; Phylogeny; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; Soil
PubMed: 30688647
DOI: 10.1099/ijsem.0.003154 -
Applied Biochemistry and Biotechnology Apr 2021A putative aromatic amino acid ammonia-lyase gene (named Pl-pal) was discovered in Photorhabdus luminescens DSM 3368. BLAST and phylogenetic analyses predicted that this...
A putative aromatic amino acid ammonia-lyase gene (named Pl-pal) was discovered in Photorhabdus luminescens DSM 3368. BLAST and phylogenetic analyses predicted that this enzyme is a histidine ammonia-lyase, whereas sequence alignment suggested that it is more likely a phenylalanine ammonia-lyase (PAL). This gene was amplified from P. luminescens and expressed in Escherichia coli BL21(DE3). The function of Pl-PAL (58 kDa) was characterized by in vitro enzymatic reactions with L-phenylalanine (L-Phe), L-tyrosine (L-Tyr), L-histidine (L-His), and L-tryptophan (L-Trp). Pl-PAL can convert L-Phe and L-Tyr to trans-cinnamic acid and p-coumaric acid, respectively, but had no function on L-His and L-Trp. The optimum temperature and pH were determined to be 40 °C and 11.0, respectively. Under the optimal conditions, Pl-PAL had a k/K value of 0.52 s mM with L-Phe as the substrate, while only 0.013 s mM for L-Tyr. Therefore, the primary function of Pl-PAL was determined to be PAL. The Pl-pal-harboring E. coli strain was used as a whole-cell biocatalyst to produce trans-cinnamic acid from L-Phe. The overall molar conversion rate and productivity were 65.98% and 228.10 mg L h, respectively, after the cells were repeatedly utilized 7 times. This work thus provides a promising strain for industrial production of trans-cinnamic acid.
Topics: Bacterial Proteins; Phenylalanine Ammonia-Lyase; Photorhabdus; Recombinant Proteins
PubMed: 33411135
DOI: 10.1007/s12010-020-03477-6 -
Current Biology : CB Sep 2006
Topics: Animals; Ants; Biological Evolution; Female; Male; Photorhabdus; Social Behavior; Wasps
PubMed: 16950082
DOI: 10.1016/j.cub.2006.08.015 -
Insect Biochemistry and Molecular... Nov 2023PirAB binary toxin from Photorhabdus is toxic to the larvae of dipteran and lepidopteran insect pests. However, the 3-D structures and their toxicity mechanism are not...
PirAB binary toxin from Photorhabdus is toxic to the larvae of dipteran and lepidopteran insect pests. However, the 3-D structures and their toxicity mechanism are not yet fully understood. Here we report the crystal structures of PirA and PirB proteins from Photorhabdus akhurstii subsp. akhurstii K-1 at 1.6 and 2.1 Å, respectively. PirA comprises of eight β-strands depicting jelly-roll topology while PirB folds into two distinct domains, an N-terminal domain (PirB-N) made up of seven α-helices and a C-terminal domain (PirB-C) consists of ten β-strands. Despite the low sequence identity, PirA adopts similar architecture as domain III and PirB shared similar architecture as domain I/II of the Cry δ-endotoxin of Bacillus thuringiensis, respectively. However, PirA shows significant structural variations as compared to domain III of lepidopteran and dipteran specific Cry toxins (Cry1Aa and Cry11Ba) suggesting its role in virulence among range of insect pests and hence, in receptor binding. High structural resemblance between PirB-N and domain I of Cry toxin raises the possibility that the putative PirAB binary toxin may mimic the toxicity mechanism of the Cry protein, particularly its ability to perform pore formation. The mixture of independently purified PirA and PirB proteins are not toxic to insects. However, PirA-PirB protein complex purified from expression of pir operon with non-coding Enterobacterial Repetitive Intergenic Consensus (ERIC) sequences found toxic to Galleria mellonella larvae with LD value of 1.62 μg/larva. This suggests that toxic conformation of PirA and PirB are achieved in-vivo with the help of ERIC sequences.
Topics: Animals; Photorhabdus; Bacterial Proteins; Endotoxins; Moths; Larva; Insecta; Hemolysin Proteins
PubMed: 37778713
DOI: 10.1016/j.ibmb.2023.104014 -
Toxicon : Official Journal of the... Apr 2021The Gram-negative bacteria Photorhabdus lives in a symbiotic relationship with the insect-pathogenic Heterorhabditis nematodes and produces numerous hydrolytic enzymes,...
The Gram-negative bacteria Photorhabdus lives in a symbiotic relationship with the insect-pathogenic Heterorhabditis nematodes and produces numerous hydrolytic enzymes, secondary metabolites and protein toxins. Seven Photorhabdus strains were previously isolated from the Heterorhabditis nematodes collected from different geographical regions of India. The strains IARI-SGMG3, IARI-SGHR2, IARI-SGHR4, IARI-SGMS1 and IARI-SGGJ2 were identified as P. akhurstii, whereas IARI-SGLDK1 and IARI-SGHP1 were identified as P. laumondii subsp. laumondii and P. laumondii subsp. clarkeii, respectively. A new and previously unreported 35 kDa molecular weight protein toxin 'Galtox' was identified from these Photorhabdus strains. The nucleotide sequences of the toxin gene from seven Photorhabdus strains were PCR amplified, sequenced, cloned into pET protein expression vector, and the protein toxin was expressed and purified. The Galtox sequence from various strains showed variations in sequence and toxicity against Galleria mellonella. The injection of purified Galtox protein into the 4th instar larvae showed median lethal dose (LD) values of 2.39-26.08 ng toxin/g G. mellonella bodyweight after 48 h. The protein injection killed the insects quickly and exhibited a median lethal time (LT) of 12-60 h when injected at the rate of 3.1-31.2 ng toxin/g G. mellonella bodyweight. Galtox protein sequence analysis indicated similarity to several bacterial toxin-related protein domains, such as 6rgnA domain of Bordetella membrane targeting toxin BteA, 6gy6 domain of Xenorhabdus α-Xenorhabdolysins, 4mu6A and 4xa9a domains similar to effector protein LegC3 from Legionella pneumophila and 1cv8.1 domain of staphylococcal cysteine proteinase staphopain B. The mode of action of Galtox needs to be understood to enable its use for the management of agricultural insect-pests.
Topics: Animals; Bacterial Toxins; India; Moths; Nematoda; Photorhabdus; Xenorhabdus
PubMed: 33610634
DOI: 10.1016/j.toxicon.2021.02.011 -
Microbes and Infection Jun 2008Gram-negative bacteria, Photorhabdus luminescens and P. temperata, form a mutualistic association with entomopathogenic heterorhabditid nematodes while P. asymbiotica is...
Gram-negative bacteria, Photorhabdus luminescens and P. temperata, form a mutualistic association with entomopathogenic heterorhabditid nematodes while P. asymbiotica is known as an opportunistic human pathogen that causes disseminated bacteremic spread on two continents, the United States and Australia. In the course of our phylogenetic study of Photorhabdus bacteria associated with Japanese Heterorhabditis nematodes, we found two Photorhabdus isolates (Photorhabdus sp. Cbkj163 and OnIr40) whose partial 16S rRNA gene sequence showed high similarities to clinical isolates of this pathogen from Heterorhabditis indica. The phylogenetic study, based upon the gyrase subunit B gene sequences of the two isolates, revealed clustering with these clinical isolates of P. asymbiotica from both the United States and Australia but not with other Photorhabdus bacteria associated with nematodes. The two bacterial isolates were also found to share microbiological and biochemical characteristics with clinical and entomopathogenic Photorhabdus strains. Moreover, not only the two novel Photorhabdus isolates but also an Australian clinical isolate of P. asymbiotica formed mutualistic association with H. indica isolates. These data suggest that the bacteria isolated from H. indica CbKj163 and OnIr40 are a novel subspecies of P. asymbiotica, and that some clinical isolates of P. asymbiotica could have originated from bacteria associated with entomopathogenic nematodes.
Topics: Animals; Bacterial Proteins; Bacterial Typing Techniques; Cluster Analysis; DNA Gyrase; DNA, Bacterial; DNA, Ribosomal; Genes, rRNA; Japan; Molecular Sequence Data; Photorhabdus; Phylogeny; RNA, Bacterial; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; Sequence Homology, Nucleic Acid; Symbiosis
PubMed: 18538616
DOI: 10.1016/j.micinf.2008.03.010 -
Current Microbiology Oct 2010The bacterial symbiont of the entomopathogenic nematode Heterorhabditis bacteriophora strain GPS11 was characterized by 16S rRNA gene sequence and physiological traits....
The bacterial symbiont of the entomopathogenic nematode Heterorhabditis bacteriophora strain GPS11 was characterized by 16S rRNA gene sequence and physiological traits. The phylogenetic tree built upon 16S rRNA gene sequences clustered the GPS11 bacterial isolate with Photorhabdus temperata strains which have been previously isolated from Heterorhabditis species. The phylogenetic tree further identified four subgroups in P. temperata, and the relationships among these subgroups were confirmed by gyrase subunit B (gyrB) gene sequence analysis. The subgroup containing the GPS11 bacterial isolate differs from other subgroups in sequences of 16S rRNA and gyrB gene, physiological traits, nematode host species, and geographic origin. Therefore, the subgroup comprising the GPS11 bacterial isolate is proposed here as a new subspecies: Photorhabdus temperata subsp. stackebrandtii subsp. nov. (type strain GPS11). The type strain has been deposited in ATCC and DSMZ collections.
Topics: Animals; Bacterial Typing Techniques; Base Sequence; DNA Gyrase; DNA, Bacterial; Genes, rRNA; Photorhabdus; Phylogeny; Polymerase Chain Reaction; RNA, Ribosomal, 16S; Rhabditoidea; Sequence Analysis, DNA; Symbiosis
PubMed: 20852981
DOI: 10.1007/s00284-010-9610-9