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Background: Biomphalaria glabrata acts as the intermediate host of schistosomes that causes human schistosomiasis. Symbiotic bacteria, Xenorhabdus and Photorhabdus associated with Steinernema and Heterorhabditis, produce secondary metabolites with several biological activities. Controlling B. glabrata is a potential strategy to limit the transmission of schistosomiasis. The aims of this study were to identify Xenorhabdus and Photorhabdus bacteria based on recA sequencing and evaluate their molluscicidal activity against B. glabrata snail. Results: A total of 31 bacterial isolates belonging to Xenorhabdus (n = 19) and Photorhabdus (n = 12) (X. ehlersii, X. stockiae, X. indica, X. griffinae, P. luminescens, P. akhurstii, and P. laumondii subsp. laumondii were molecularly identified based on recA sequencing. Five isolates of bacterial extracts showed potential molluscicide, with 100% snail mortality. P. laumondii subsp. laumondii (bALN19.5_TH) showed the highest effectiveness with lethal concentration (LC) values of 54.52 µg/mL and 89.58 µg/mL for LC50 and LC90, respectively. Histopathological changes of the snail were observed in the head–foot region, which showed ruptures of the epithelium covering the foot and deformation of the muscle fiber. A hemocyte of the treated snails was observed in the digestive tubules of the digestive glands. The hermaphrodite glands of treated snails showed a reduction in the number of spermatozoa, degeneration of oocytes, and deformation and destruction in the hermaphrodite gland. In addition, liquid chromatography–tandem mass spectrometry (LC–MS/MS) of three symbiotic bacteria contained compounds such as GameXPeptide, Xenofuranone, and Rhabdopeptide. Conclusions: Five bacterial extracts showed good activity against B. glabrata, especially P. laumondii subsp. laumondii and X. stockiae, which produced virulent secondary metabolites resulting in the death of the snails. They also caused histopathological alterations in the foot, digestive glands, and hermaphrodite glands of the snails. This study suggests that extracts from these bacteria show promise as molluscicides for the control of B. glabrata. [ABSTRACT FROM AUTHOR]

Aim This study aimed to overproduce industrially relevant and safe bio-compound trans-cinnamic acid (tCA) from Photorhabdus luminescens with deletion strategies and homologous expression strategies that had not been applied before for tCA production. Methods and Results The overproduction of the industrially relevant compound tCA was successfully performed in P. luminescens by deleting stlB (TTO1ΔstlB) encoding a cinnamic acid CoA ligase in the isopropylstilbene pathway and the hcaE insertion (knockout) mutation (hcaE::cat) in the phenylpropionate catabolic pathway, responsible for tCA degradation. A double mutant of both stlB deletion and hcaE insertion mutation (TTO1DM ΔstlB-hcaE::cat) was also generated. These deletion strategies and the phenylalanine ammonium lyase-producing (PI-PAL from Photorhabdus luminescens) plasmid, pBAD30C, carrying stlA (homologous expression mutants) are utilized together in the same strain using different media, a variety of cultivation conditions, and efficient anion exchange resin (Amberlite IRA402) for enhanced tCA synthesis. At the end of the 120-h shake flask cultivation, the maximum tCA production was recorded as 1281 mg l−1 in the TTO1pBAD30C mutant cultivated in TB medium, with the IRA402 resin keeping 793 mg l−1 and the remaining 488 mg l−1 found in the supernatant. Conclusion TCA production was successfully achieved with homologous expression, coupled with deletion and insertion strategies. 1281 mg l−1is the highest tCA concentration that achieved by bacterial tCA production in flask cultivation, according to our knowledge. [ABSTRACT FROM AUTHOR]

The discovery of novel bioactive compounds produced by microorganisms holds significant potential for the development of therapeutics and agrochemicals. In this study, we conducted genome mining to explore the biosynthetic potential of entomopathogenic bacteria belonging to the genera Xenorhabdus and Photorhabdus. By utilizing next-generation sequencing and bioinformatics tools, we identified novel biosynthetic gene clusters (BGCs) in the genomes of the bacteria, specifically plu00736 and plu00747. These clusters were identified as unidentified non-ribosomal peptide synthetase (NRPS) and unidentified type I polyketide synthase (T1PKS) clusters. These BGCs exhibited unique genetic architecture and encoded several putative enzymes and regulatory elements, suggesting its involvement in the synthesis of bioactive secondary metabolites. Furthermore, comparative genome analysis revealed that these BGCs were distinct from previously characterized gene clusters, indicating the potential for the production of novel compounds. Our findings highlighted the importance of genome mining as a powerful approach for the discovery of biosynthetic gene clusters and the identification of novel bioactive compounds. Further investigations involving expression studies and functional characterization of the identified BGCs will provide valuable insights into the biosynthesis and potential applications of these bioactive compounds. [ABSTRACT FROM AUTHOR]

Natural products have been proven to be important starting points for the development of new drugs. Bacteria in the genera Photorhabdus and Xenorhabdus produce antimicrobial compounds as secondary metabolites to compete with other organisms. Our study is the first comprehensive study screening the anti-protozoal activity of supernatants containing secondary metabolites produced by 5 Photorhabdus and 22 Xenorhabdus species against human parasitic protozoa, Acanthamoeba castellanii, Entamoeba histolytica, Trichomonas vaginalis, Leishmania tropica and Trypanosoma cruzi, and the identification of novel bioactive antiprotozoal compounds using the easyPACId approach (easy Promoter Activated Compound Identification) method. Though not in all species, both bacterial genera produce antiprotozoal compounds effective on human pathogenic protozoa. The promoter exchange mutants revealed that antiprotozoal bioactive compounds produced by Xenorhabdus bacteria were fabclavines, xenocoumacins, xenorhabdins and PAX peptides. Among the bacteria assessed, only P. namnaoensis appears to have acquired amoebicidal property which is effective on E. histolytica trophozoites. These discovered antiprotozoal compounds might serve as starting points for the development of alternative and novel pharmaceutical agents against human parasitic protozoa in the future. [ABSTRACT FROM AUTHOR]

Photorhabdus spp. (Enterobacteriales: Morganellaceae) occur exclusively as symbionts of Heterorhabditis nematodes for which they provide numerous services, including killing insects and providing nutrition and defence within the cadavers. Unusually, two species (Photorhabdus cinerea and Photorhabdus temperata) associate with a single population of Heterorhabditis downesi at a dune grassland site. Building on previous work, we investigated competition between these two Photorhabdus species both at the regional (between insects) and local (within insect) level by trait comparison and co-culture experiments. There was no difference between the species with respect to supporting nematode reproduction and protection of cadavers against invertebrate scavengers, but P. cinerea was superior to P. temperata in several traits: faster growth rate, greater antibacterial and antifungal activity and colonisation of a higher proportion of nematodes in co-culture. Moreover, where both bacterial symbionts colonised single nematode infective juveniles, P. cinerea tended to dominate in numbers. Differences between Photorhabdus species were detected in the suite of secondary metabolites produced: P. temperata produced several compounds not produced by P. cinerea including anthraquinone pigments. Bioluminescence emitted by P. temperata also tended to be brighter than that from P. cinerea. Bioluminescence and pigmentation may protect cadavers against scavengers that rely on sight. We conclude that while P. cinerea may show greater local level (within-cadaver) competitive success, co-existence of the two Photorhabdus species in the spatially heterogeneous environment of the dunes is favoured by differing specialisations in defence of the cadaver against differing locally important threats. [ABSTRACT FROM AUTHOR]

Serotonin (5-hydroxytryptamine: 5-HT) is a biogenic monoamine that mediates immune responses and modulates nerve signal in insects. Se-5HTR, a specific receptor of serotonin, has been identified in the beet armyworm, Spodoptera exigua. It is classified into subtype 7 among known 5HTRs. Se-5HTR was expressed in all developmental stages of S. exigua. It was expressed in all tested tissues of larval stage. Its expression was up-regulated in hemocytes and fat body in response to immune challenge. RNA interference (RNAi) of Se-5HTR exhibited significant immunosuppression by preventing cellular immune responses such as phagocytosis and nodulation. Treatment with an inhibitor (SB-269970) specific to 5HTR subtype 7 resulted in significant immunosuppression. Furthermore, knockout mutant of Se-5HTR by CRISPR-Cas9 led to significant reduction of phagocytotic activity of S. exigua hemocytes. Such immunosuppression was also induced by bacterial secondary metabolites derived from Xenorhabdus and Photorhabdus. To determine specific bacterial metabolites inhibiting Se-5HTR, this study screened 37 bacterial secondary metabolites with respect to cellular immune responses associated with Se-5HTR and selected 10 potent inhibitors. These 10 selected compounds competitively inhibited cellular immune responses against 5-HT and shared phenylethylamide (PEA) chemical skeleton. Subsequently, 46 PEA derivatives were screened and resulting potent chemicals were used to design a compound to be highly inhibitory against Se-5HTR. The designed compound was chemically synthesized. It showed high immunosuppressive activities along with specific and competitive inhibition activity for Se-5HTR. This study reports the first 5HT receptor from S. exigua and provides its specific inhibitor designed from bacterial metabolites and their derivatives. [ABSTRACT FROM AUTHOR]

Photorhabdus luminescens maintains a symbiotic relationship with the nematodes Heterorhabditis bacteriophora and together they infect and kill insect larvae. To maintain this symbiotic relationship, the bacteria must produce an array of secondary metabolites to assist in the development and replication of nematodes. The regulatory mechanisms surrounding production of these compounds are mostly unknown. The global post-transcriptional regulator, Hfq, is widespread in bacteria and performs many functions, one of which is the facilitation of sRNA binding to target mRNAs, with recent research thoroughly exploring its various pleiotropic effects. Here we generate and characterize an hfq deletion mutant and show that in the absence of hfq, the bacteria are no longer able to maintain a healthy symbiosis with nematodes due to the abolishment of the production of all known secondary metabolites. RNAseq led us to produce a second deletion of a known repressor, HexA, in the same strain, which restored both metabolite production and symbiosis. [ABSTRACT FROM AUTHOR]

Background: Bacteria within the genus Photorhabdus maintain mutualistic symbioses with nematodes in complicated lifecycles that also involves insect pathogenic phases. Intriguingly, these bacteria are rich in biosynthetic gene clusters that produce compounds with diverse biological activities. As a basis to better understand the life cycles of Photorhabdus we sequenced the genomes of two recently discovered representative species and performed detailed genomic comparisons with five publically available genomes. Results: Here we report the genomic details of two new reference Photorhabdus species. By then conducting genomic comparisons across the genus, we show that there are several highly conserved biosynthetic gene clusters. These clusters produce a range of bioactive small molecules that support the pathogenic phase of the integral relationship that Photorhabdus maintain with nematodes. Conclusions: Photorhabdus contain several genetic loci that allow them to become specialist insect pathogens by efficiently evading insect immune responses and killing the insect host. [ABSTRACT FROM AUTHOR]

The genus Sorangium synthesizes approximately half of the secondary metabolites isolated from myxobacteria, including the anti-cancer metabolite epothilone. We report the complete genome sequence of the model Sorangium strain S. cellulosum So ce56, which produces several natural products and has morphological and physiological properties typical of the genus. The circular genome, comprising 13,033,779 base pairs, is the largest bacterial genome sequenced to date. No global synteny with the genome of Myxococcus xanthus is apparent, revealing an unanticipated level of divergence between these myxobacteria. A large percentage of the genome is devoted to regulation, particularly post-translational phosphorylation, which probably supports the strain's complex, social lifestyle. This regulatory network includes the highest number of eukaryotic protein kinase–like kinases discovered in any organism. Seventeen secondary metabolite loci are encoded in the genome, as well as many enzymes with potential utility in industry. [ABSTRACT FROM AUTHOR]

During the last 20 years myxobacteria have made their way from highly exotic organisms to one of the major sources of microbial secondary metabolites besides actinomycetes and fungi. The pharmaceutical interest in these peculiar prokaryotes lies in their ability to produce a variety of structurally unique compounds and/or metabolites with rare biological activities. This review deals with the recent progress toward a better understanding of the biology, the genetics, the biochemistry and the regulation of secondary metabolite biosynthesis in myxobacteria. These research efforts paved the way to sophisticated in vitro studies and to the heterologous expression of complete biosynthetic pathways in conjunction with their targeted manipulation. The progress made is a prerequisite for using the vast resource of myxobacterial diversity regarding secondary metabolism more efficiently in the future. [ABSTRACT FROM AUTHOR]

In this issue of Chemistry & Biology, Angell et al. demonstrate synergism between two bacterial species, isolated from the same sediment sample, to produce a secondary metabolite not found in their respective pure cultures. [Copyright &y& Elsevier]

Isovaleryl-coenzyme A (IV-CoA) is the starting unit for some secondary metabolites and iso-odd fatty acids in several bacteria. According to textbook biochemistry, IV-CoA is derived from leucine degradation, but recently an alternative pathway that branches from the well-known mevalonate-dependent isoprenoid biosynthesis has been described for myxobacteria. A double mutant was constructed in Myxococcus xanthus by deletion of genes involved in leucine degradation and disruption of mvaS encoding the 3-hydroxy-3-methylglutaryl-coenzyme A synthase. A dramatic decrease of IV-CoA-derived iso-odd fatty acids was observed for the mutant, confirming mvaS to be involved in the alternative pathway. Additional quantitative real-time reverse transcription-PCR experiments indicated that mvaS is transcriptionally regulated by isovalerate. Furthermore, feeding studies employing an intermediate specific for the alternative pathway revealed that this pathway is induced during fruiting body formation, which presumably increases the amount of IV-CoA available when leucine is limited. [ABSTRACT FROM AUTHOR]

Abstract: The myxobacterial polyketide secondary metabolites aurafuron A and B were identified by genome mining in the myxobacterial strain Stigmatella aurantiaca DW4/3-1. The compounds contain an unusual furanone moiety and resemble metabolites isolated from soil-dwelling and marine actinobacteria, a fungus and mollusks. We describe here the cloning and functional analysis of the aurafuron biosynthetic gene cluster, including site-directed mutagenesis and feeding studies using labeled precursors. The polyketide core of the aurafurones is assembled by a modular polyketide synthase (PKS). As with many such systems described from myxobacteria, the aurafuron PKS exhibits a number of unusual features, including the apparent iterative use of a module, redundant modules and domains, a trans acting dehydratase and the absence of a terminal thioesterase domain. Four oxidoreductases are encoded within the gene locus, some of which likely participate in formation of the furanone moiety via a Baeyer–Villiger type oxidation. Indeed, inactivation of a gene encoding a cytochrome P 450 monooxygenase completely abolished production of both compounds. We also compare the complete gene locus to biosynthetic gene clusters from two Streptomyces sp., which produce close structural analogues of the aurafurones. A portion of the post-PKS biosynthetic machinery is strikingly similar in all three cases, in contrast to the PKS genes, which are highly divergent. Phylogenetic analysis of the ketosynthase domains further indicates that the PKSs have developed independently (polyphyletically) during evolution. These findings point to a currently unknown but important biological function of aurafuron-like compounds for the producing organisms. [Copyright &y& Elsevier]

[Display omitted] • Larvicidal and ovidical activities of bacterial CFS are dose and species dependent. • Xenorhabdus bacterial metabolites have ovicidal effects on Aedes aegypti eggs. • Fabclavines are highly toxic against mosquito larvae. Aedes -transmitted arboviral infections such as Dengue, Yellow Fever, Zika and Chikungunya are increasing public health problems. Xenorhabdus and Photorhabdus bacteria are promising sources of effective compounds with important biological activities. This study investigated the effects of cell-free supernatants of X. szentirmaii , X. cabanillasii and P. kayaii against Ae. aegypti eggs and larvae and identified the bioactive larvicidal compound in X. szentirmaii using The EasyPACId method. Among the three tested bacterial species, X. cabanillasii exhibited the highest (96%) egg hatching inhibition and larvicidal activity (100% mortality), whereas P. kayaii was the least effective species in our study. EasyPACId method revealed that bioactive larvicidal compound in the bacterial supernatant was fabclavine. Fabclavines obtained from promoter exchange mutants of different bacterial species such as X. cabanillasii, X. budapestensis, X. indica , X. szentirmaii, X. hominckii and X. stockiae were effective against mosquito larvae. Results show that these bacterial metabolites have potential to be used in integrated pest management (IPM) programmes of mosquitoes. [ABSTRACT FROM AUTHOR]

Quinolinic acid is a product of tryptophan degradation and may serve as a precursor for NAD+, an important enzymatic cofactor for enzymes such as the DNA repair protein PARP. Pathologic accumulation of quinolinic acid has been found in neurodegenerative disorders including Alzheimer and Huntington disease, where it is thought to be toxic for neurons by activating the N-methyl-D-aspartate (NMDA) receptor and inducing excitotoxicity. Although many tumors including gliomas constitutively catabolize tryptophan, it is unclear whether quinolinic acid is produced in gliomas and whether it is involved in tumor progression. Here, we show that quinolinic acid accumulated in human gliomas and was associated with a malignant phenotype. Quinolinic acid was produced by microglial cells, as expression of the quinolinic acid-producing enzyme 3-hydroxyanthranilate oxygenase (3-HAO) was confined to microglia in glioma tissue. Human malignant glioma cells, but not nonneoplastic astrocytes, expressed quinolinic acid phosphoribosyltransferase (QPRT) to use quinolinic acid for NAD+ synthesis and prevent apoptosis when de novo NAD+ synthesis was blocked. Oxidative stress, temozolomide, and irradiation induced QPRT in glioma cells. QPRT expression increased with malignancy. In recurrent glioblastomas after radiochemotherapy, QPRT expression was associated with a poor prognosis in two independent datasets. Our data indicate that neoplastic transformation in astrocytes is associated with a QPRT-mediated switch in NAD+ metabolism by exploiting microglia-derived quinolinic acid as an alternative source of replenishing intracellular NAD+ pools. The elevated levels of QPRT expression increase resistance to oxidative stress induced by radiochemotherapy, conferring a poorer prognosis. These findings have implications for therapeutic approaches inducing intracellular NAD+ depletion, such as alkylating agents or direct NAD+ synthesis inhibitors, and identify QPRT as a potential therapeutic target in malignant gliomas. [ABSTRACT FROM AUTHOR]