Elevated MIF identified by multiple cytokine analyses facilitates macrophage M2 polarization contributing to postoperative recurrence in chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by tissue heterogeneity and high postoperative recurrence risk. This study aims to employ cytokine analyses to identify serum biomarkers associated with postoperative CRSwNP recurrence and elucidate underlying recurrent mechanisms.

METHODS

A prospective cohort study was conducted on CRSwNP patients undergoing functional endoscopic sinus surgery. Serum and tissue samples were collected and analyzed for multiple cytokines. Participants were followed for 3 years and categorized into recurrent and non-recurrent groups. Cytokine profiles were compared, and potential markers for recurrence were further assessed. Macrophage migration inhibitory factor (MIF) expression in macrophages was modulated, and their polarization and cytokine secretion were assessed.

RESULTS

In the discovery cohort (21 recurrent and 40 non-recurrent patients), circulating cytokine profiles differed significantly, with 8 cytokines showing differential expression between the two groups. Among them, serum eotaxin, MIF, RANTES, and TRAIL exhibited promise in predicting recurrence. In the validation cohort (24 recurrent and 44 non-recurrent patients), serum eotaxin, MIF, and TRAIL levels were higher in recurrent cases. Tissue MIF was elevated in recurrent cases and had a strong predictive value for recurrence. Moreover, tissue MIF was co-expressed with CD206 in recurrent cases. Mechanistically, MIF overexpression promoted macrophage M2 polarization and TGF-β1, CCL-24, and MIF secretion, and MIF recombinant protein facilitated M2 polarization, and TGF-β1 and CCL-24 production, contributing to CRSwNP recurrence.

CONCLUSIONS

Serum-specific cytokine signatures were associated with postoperative recurrence risk in CRSwNP. Elevated MIF enhanced macrophage M2 polarization and cytokine secretion, contributing to the recurrent mechanisms of CRSwNP.

Stereoselective Alder-Ene Reactions of Bicyclo[1.1.0]butanes: Facile Synthesis of Cyclopropyl- and Aryl-Substituted Cyclobutenes

Bicyclo[1.1.0]butanes (BCBs), strained carbocycles comprising two fused cyclopropane rings, have become well-established building blocks in organic synthesis, medicinal chemistry, and chemical biology due to their diverse reactivity profile with radicals, nucleophiles, cations, and carbenes. The constraints of the bicyclic ring system confer high p-character on the interbridgehead C-C bond, leading to this broad reaction profile; however, the use of BCBs in pericyclic processes has to date been largely overlooked in favor of such stepwise, non-concerted additions. Here, we describe the use of BCBs as substrates for ene-like reactions with strained alkenes and alkynes, which give rise to cyclobutenes decorated with highly substituted cyclopropanes and arenes. The former products are obtained from highly stereoselective reactions with cyclopropenes, generated in situ from vinyl diazoacetates under blue light irradiation (440 nm). Cyclobutenes featuring a quaternary aryl-bearing carbon atom are prepared from equivalent reactions with arynes, which proceed in high yields under mild conditions. Mechanistic studies highlight the importance of electronic effects in this chemistry, while computational investigations support a concerted pathway and rationalize the excellent stereoselectivity of reactions with cyclopropenes.

Gold-Catalyzed Cyclization of Yndiamides with Isoxazoles via α-Imino Gold Fischer Carbenes

Gold catalysis is an important method for alkyne functionalization. Here we report the gold-catalyzed formal [3+2] aminative cyclization of yndiamides and isoxazoles in a direct synthesis of polysubstituted diaminopyrroles, which are important motifs in drug discovery. Key to this process is the formation, and subsequent cyclization, of an α-imino gold Fischer carbene, which represents a new type of gold carbene intermediate. The reaction proceeds rapidly under mild conditions, with high regioselectivity being achieved by introducing a subtle steric bias between the nitrogen substituents on the yndiamide. DFT calculations revealed that the key to this regioselectivity was the interconversion of isomeric gold keteniminiun ions via a low-barrier π-complex transition state, which establishes a Curtin-Hammett scenario for isoxazole addition. By using benzisoxazoles as substrates, the reaction outcome could be switched to a formal [5+2] cyclization, leading to 1,4-oxazepines.

First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment

The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9  GeV/c^{2}. The most stringent limit is set for spin-independent scattering at 36  GeV/c^{2}, rejecting cross sections above 9.2×10^{-48}  cm at the 90% confidence level.

Rhodium-Catalyzed [2 + 2 + 2] Cyclotrimerizations of Yndiamides with Alkynes

Yndiamides offer opportunities for the synthesis of vicinally nitrogen-disubstituted aromatics and azacycles. Here we report the Rh-catalyzed cyclotrimerization of alkynyl yndiamides with alkynes, the regiochemical outcome of which is controlled by the electronic properties of the alkyne partner, enabling the formation of 7-aminoindolines with excellent selectivity (up to >20:1 r.r.). We also report a complementary synthesis of bicyclic 1,2-dianiline derivatives by cyclotrimerization of yndiamides with terminal diynes, where slow addition of the diyne overcomes self-dimerization.

Synthesis of Polysubstituted Fused Pyrroles by Gold-Catalyzed Cycloisomerization/1,2-Sulfonyl Migration of Yndiamides

Yndiamides (bis-N-substituted alkynes) are valuable precursors to azacycles. Here we report a cycloisomerization/1,2-sulfonyl migration of alkynyl-yndiamides to form tetrahydropyrrolopyrroles, unprecedented heterocyclic scaffolds that are relevant to medicinal chemistry. This functional group tolerant transformation can be achieved using Au(I) catalysis that proceeds at ambient temperature, and a thermally promoted process. The utility of the products is demonstrated by a range of reactions to functionalize the fused pyrrole core.

Advances in polycyclization cascades in natural product synthesis

Cascade reactions are among the most powerful means to achieve the construction of multiple ring systems in a single step. This tutorial review describes recent advances in the use of polycyclization cascades in natural product synthesis.

Efficacy of utidelone plus capecitabine versus capecitabine for heavily pretreated, anthracycline- and taxane-refractory metastatic breast cancer: final analysis of overall survival in a phase III randomised controlled trial

BACKGROUND

Primary analysis of the phase III trial BG01-1323L demonstrated that utidelone plus capecitabine significantly improved progression-free survival (PFS) and overall response rate (ORR) versus capecitabine alone in heavily-pretreated patients with metastatic breast cancer (MBC). Here, we report the final overall survival (OS) analysis and updates of other endpoints.

PATIENTS AND METHODS

In total, 405 patients were randomised 2:1 to receive utidelone (30 mg/m² IV daily, days 1-5, over 90 min) plus capecitabine (1000 mg/m² orally b.i.d., days 1-14) or capecitabine alone (1250 mg/m² orally b.i.d., days 1-14) every 21 days. The secondary endpoint, OS, was estimated using the Kaplan-Meier product-limit approach at a two-sided alpha level of 0.05 after the prespecified 310 death events had been reached. Exploratory analyses of the primary endpoint, PFS, and the secondary endpoint, ORR, were also done. Safety was analysed in patients who had at least one dose of study drug.

RESULTS

At the final OS analysis, the median duration of follow-up was 19.6 months in the utidelone plus capecitabine group and 15.4 months in the capecitabine alone group. In the intention-to-treat population, 313 deaths had occurred at data cut-off, 203 of 270 patients in the combination group and 110 of 135 in the monotherapy group. Median OS in the combination group was 19.8 months compared with 16.0 months in the monotherapy group [hazard ratio (HR) = 0.75, 95% confidence intervals (CI) 0.59-0.94, P = 0.0142]. The updated analysis of PFS and ORR showed that the combination therapy remained superior to monotherapy. Safety results were similar to those previously reported with respect to incidence, severity and specificity. No late-emerging toxicities or new safety concerns occurred.

CONCLUSIONS

For heavily-pretreated, anthracycline- and taxane-resistant MBC patients, utidelone plus capecitabine significantly improved OS versus capecitabine alone. These results support the use of utidelone plus capecitabine as a novel therapeutic regimen for patients with MBC.

Synthesis, Cytotoxicity, and Mechanistic Investigation of Platinum(IV) Anticancer Complexes Conjugated with Poly(ADP-ribose) Polymerase Inhibitors

Many clinical trials using combinations of platinum drugs and PARP-1 inhibitors (PARPi) have been carried out, with the hope that such combinations will lead to enhanced therapeutic outcomes against tumors. Herein, we obtained seven potential PARPi with structural diversity and then conjugated them with cisplatin-based platinum(IV) complexes. Both the synthesized PARPi ligands and PARPi-Pt conjugates [PARPi-Pt(IV)] show inhibitory effects against PARP-1's catalytic activity. The PARPi-Pt(IV) conjugates are cytotoxic in a panel of human cancer cell lines, and the leading ones display the ability to overcome cisplatin resistance. A mechanistic investigation reveals that the representative PARPi-Pt(IV) conjugates efficiently enter cells, bind to genomic DNA, disturb cell cycle distribution, and induce apoptotic cell death in both cisplatin-sensitive and -resistant cells. Our study provides a strategy to improve the cytotoxicity of platinum(IV)-based anticancer complexes and overcome cisplatin resistance by using a small-molecule anticancer complex that simultaneously damages DNA and inhibits PARP.

Synthesis and Cytotoxic Study of a Platinum(IV) Anticancer Prodrug with Selectivity toward Luteinizing Hormone-Releasing Hormone (LHRH) Receptor-Positive Cancer Cells

Platinum drugs including cisplatin are widely used in clinics to treat various types of cancer. However, the lack of cancer-cell selectivity is one of the major problems that lead to side effects in normal tissues. Luteinizing hormone-releasing hormone (LHRH) receptors are overexpressed in many types of cancer cells but rarely presented in normal cells, making LHRH receptor a good candidate for cancer targeting. In this study, we report the synthesis and cytotoxic study of a novel platinum(IV) anticancer prodrug functionalized with LHRH peptide. This LHRH-platinum(IV) conjugate is highly soluble in water and quite stable in a PBS buffer. Cytotoxic study reveals that the prodrug selectively targets LHRH receptor-positive cancer cell lines with the cytotoxicities 5-8 times higher than those in LHRH receptor-negative cell lines. In addition, the introduction of LHRH peptide enhances the cellular accumulation in a manner of receptor-mediated endocytosis. Moreover, the LHRH-platinum(IV) prodrug is proved to kill cancer cells by binding to the genomic DNA, inducing apoptosis, and arresting the cell cycle at the G₂/M phase. In summary, we report a novel LHRH-platinum(IV) anticancer prodrug having largely improved selectivity toward LHRH receptor-positive cancer cells, relative to cisplatin.

Synthesis, Structure, and Cytotoxicity of Oxaliplatin-Based Platinum(IV) Anticancer Prodrugs Bearing One Axial Fluoride

Fluorine plays more and more important roles in drug design and development. In recent years, fluorine-containing organic drugs have already been applied in a broad range of therapeutic areas. Herein, we report our attempt to introduce an axial fluorine ligand to Pt(IV) complexes by oxidizing oxaliplatin with electrophilic fluorinating reagents in different protic solvents. The crystal structure of one representative complex is presented. The fluorinated Pt(IV) complexes are further expanded by functionalization with different anhydrides, and their analogues bearing one different axial ligand (OAc or OH group) are also synthesized. Further investigations show that the axial fluorine atom has dramatic effects on the chemical properties of these prodrugs. These new fluorinated Pt(IV) complexes are proved to be stable in physiological conditions. For most of the fluorinated Pt(IV) complexes, a higher reduction potential indicates its greater tendency to be reduced by ascorbate. Introducing an axial fluorine ligand in Pt(IV) complexes does not lead to the increase of their lipophilicity. Moreover, these new fluorinated Pt(IV) complexes show better cytotoxicity than nonfluorinated analogues which may derive from their higher cellular accumulation in cancer cells. Therefore, the good stability and high cytotoxicity of these fluorinated Pt(IV) prodrugs indicate their great potential as a building block for further functionalization.

Overexpression of EPS8L3 promotes cell proliferation by inhibiting the transactivity of FOXO1 in HCC

The homology of epidermal growth factor receptor pathway substrate 8 (EPS8), EPS8L3, is elevated significantly in hepatocellular carcinoma (HCC) tissues and cell lines compared with the normal liver tissues and cell lines. The MTT and colony formation assays demonstrated that overexpressing EPS8L3 enhances, while silencing reduces the proliferation of HCC cells. Further experiments illustrated that overexpressing EPS8L3 promotes the expression of p-AKT, Cyclin D1, but inhibits the transcriptional activity of FOXO1. Besides, colony formation assay demonstrated that AKT inhibitor suppresses the effect of EPS8L3 on proliferation in EPS8L3-overexpressing cells, whereas AKT restores the proliferation of EPS8L3-silenced cells, suggesting that EPS8L3 might promote proliferation by hyperactivating the AKT signaling pathway and subsequently inhibiting the FOXO1 transcriptional activity. Our results provide new view between EPS8L3 and progression of human HCC, suggesting that EPS8L3 may be a novel therapeutic target for HCC.

Abstract PD3-08: A randomized phase II trial of pyrotinib plus capecitabine versus lapatinib plus capecitabine in patients with HER2-positive metastatic breast cancer previously treated with taxanes, anthracyclines and/or trastuzumab

Background:Pyrotinib is an oral, irreversible pan-ErbB receptor tyrosine kinase inhibitor (TKI) with activity against epidermal growth factor receptor (EGFR) / HER1, HER2, and HER4. Lapatinib in combination with capecitabine is one of the standards of care for patients with HER2-positive metastatic breast cancer (MBC) who have received prior taxanes, anthracyclines and/or trastuzumab.

Methods: We conducted an open label, multicenter, randomized phase II trial to comparatively evaluate efficacy and safety of pyrotinib + capecitabine (PC) or lapatinib + capecitabine (LC) in women with HER2-positive MBC. Key eligibility criteria included prior treatment with taxanes, anthracyclines and/or trastuzumab, ≤2 prior chemotherapies for metastatic disease, no CNS metastases, and no prior treatment with HER2 targeted TKI. Eligible patients were randomized 1:1 to PC Arm (P 400 mg QD D1–21 + C 1000 mg/m2BID D1–14, 21-D cycle) or LC Arm (L 1250 mg QD D1–21 + C 1000 mg/m2BID D1–14, 21-D cycle). The primary endpoint was objective response rate (ORR) as assessed by investigator, and secondary endpoints included progression-free survival (PFS), time to progression (TTP), duration of response (DoR), overall survival (OS), and safety.

Results: Between May 2015 and Mar 2016, 128 patients (65 in PC arm and 63 in LC arm) were enrolled in this study. Median age was 48 years (range 25-70), ECOG performance status was 0 (53.9%) or 1 (46.1%), 62.5% had hormone receptor-positive disease, 76.6% had visceral disease and 53.9% had received prior trastuzumab in (neo)adjuvant and/or mestastatic setting. Baseline characteristics were well balanced in two arms. Median follow-up time was 15.0 months. ORR was 78.5% in PC arm and 57.1% in LC arm (p=0.01), Median PFS was 18.1 months in PC arm and 7.0 months in LC arm (hazard ratio 0.363; 95% CI 0.228, 0.579; p<0.0001), PFS benefit in PC arm compared to LC arm was observed irrespective of prior trastuzumab or not. Treatment related Grade 3-4 toxicities occurred in >2% patients in PC arm vs LC arm included hand-foot syndrome (21.5% vs 19.0%), diarrhea (13.8% vs 4.8%), decreased neutrophil (7.7% vs 1.6%), decreased WBC (6.2% vs 1.6%), vomiting (4.6% vs 0%), increased AST (3.1% vs 1.6%), decreased hemoglobin (3.1% vs 1.6%), increased total bilirubin (0% vs 4.8%) and increased conjugated bilirubin (0% vs 3.2%).

Conclusions: In women with HER2-positive MBC previously treated with taxanes, anthracyclines and/or trastuzumab, pyrotinib + capecitabine yield statistically significant better PFS and ORR than lapatinib + capecitabine in this randomized phase II trial. Phase III study is ongoing to validate this finding.

Citation Format: Xu B, Ma F, Ouyang Q, Li W, Jiang Z, Tong Z, Liu Y, Li H, Yu S, Feng J, Wang S, Hu X, Zhu X, Zou J. A randomized phase II trial of pyrotinib plus capecitabine versus lapatinib plus capecitabine in patients with HER2-positive metastatic breast cancer previously treated with taxanes, anthracyclines and/or trastuzumab [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-08.

Irradiation after surgery for breast cancer patients with primary tumours and one to three positive axillary lymph nodes: yes or no?

OBJECTIVE AND METHODS

We retrospectively analyzed clinicopathologic features and survival in breast cancer patients who had T1 or T2 primary tumours and 1-3 histologically involved axillary lymph nodes and who were treated with modified radical mastectomy without adjuvant radiotherapy (rt). We also explored prognosis to find the high- and low-risk groups.

RESULTS

From May 2001 to April 2005, 368 patients treated at Tianjin Tumor Hospital met the study criteria. The 5- and 8-year rates were 7.2% and 10.7% for locoregional recurrence (lrr), 85.1% and 77.7% for disease-free survival (dfs), and 92.8% and 89.3% for overall survival (os). Multivariate Cox regression analysis showed that age, tumour size, estrogen receptor (er) status, and lymphovascular invasion (lvi) were independent prognostic factors for lrr and dfs. Based on 4 patient-related factors that indicate poor prognosis (age < 40 years, tumour > 3 cm, er negativity, and lvi), the high-risk group (patients with 3 or 4 factors, accounting for 12.5% of the cohort) had 5- and 8-year rates of 24.3% and 36.9% for lrr, 57.2% and 39.2% for dfs, and 74.8% and 43.8% for os compared with 5.0% and 7.1% for lrr, 88.9% and 83.1% for dfs, 91.6% and 83.4% for os in the low-risk group (patients with 0-2 factors, accounting for 87.5% of the cohort; p < 0.001).

CONCLUSIONS

Our study identified several risk factors that correlated independently with a greater incidence of lrr and distant metastasis in patients with T1 and T2 breast cancer and 1-3 positive nodes. Patients with 0-2 risk factors may not be likely to benefit from post-mastectomy rt, but patients with 3-4 risk factors may need rt to optimize locoregional control and improve survival.

Succinate is an inflammatory signal that induces IL-1β through HIF-1α

Macrophages activated by the Gram-negative bacterial product lipopolysaccharide switch their core metabolism from oxidative phosphorylation to glycolysis. Here we show that inhibition of glycolysis with 2-deoxyglucose suppresses lipopolysaccharide-induced interleukin-1β but not tumour-necrosis factor-α in mouse macrophages. A comprehensive metabolic map of lipopolysaccharide-activated macrophages shows upregulation of glycolytic and downregulation of mitochondrial genes, which correlates directly with the expression profiles of altered metabolites. Lipopolysaccharide strongly increases the levels of the tricarboxylic-acid cycle intermediate succinate. Glutamine-dependent anerplerosis is the principal source of succinate, although the 'GABA (γ-aminobutyric acid) shunt' pathway also has a role. Lipopolysaccharide-induced succinate stabilizes hypoxia-inducible factor-1α, an effect that is inhibited by 2-deoxyglucose, with interleukin-1β as an important target. Lipopolysaccharide also increases succinylation of several proteins. We therefore identify succinate as a metabolite in innate immune signalling, which enhances interleukin-1β production during inflammation.

Injection of air into the headspace improves fermentation of phosphoric acid pretreated sugarcane bagasse by Escherichia coli MM170

Microaeration (injecting air into the headspace) improved the fermentation of hemicellulose hydrolysates obtained from the phosphoric acid pretreatment of sugarcane bagasse at 170°C for 10 min. In addition, with 10% slurries of phosphoric acid pretreated bagasse (180°C, 10 min), air injection into the headspace promoted xylose utilization and increased ethanol yields from 0.16 to 0.20 g ethanol/g bagasse dry weight using a liquefaction plus simultaneous saccharification and co-fermentation process (L+SScF). This process was scaled up to 80 L using slurries of acid pretreated bagasse (96 h incubation; 0.6L of air/min into the headspace) with ethanol yields of 312-347 L (82-92 gal) per tone (dry matter), corresponding to 0.25 and 0.27 g/g bagasse (dry weight). Injection of small amounts of air into the headspace may provide a convenient alternative to subsurface sparging that avoids problems of foaming, sparger hygiene, flotation of particulates, and phase separation.

Higher-capacity communication links based on two-mode phase-sensitive amplifiers

Optical communication links are usually made with erbium-doped fiber amplifiers, which amplify the signal waves in a phase-insensitive (PI) manner. They can also be made with parametric fiber amplifiers, in which the signal waves interact with idler waves. If information is transmitted using only the signals, parametric amplifiers are PI and their noise figures are comparable to those of erbium amplifiers. However, transmitting correlated information in the signals and idlers, or copying the signals prior to transmission, allows parametric amplifiers to be phase-sensitive (PS), which lowers their noise figures. The information capacities of two-mode PS links exceed those of the corresponding PI links by 2 b/s-Hz.

Effect of reduced sulfur compounds on the fermentation of phosphoric acid pretreated sugarcane bagasse by ethanologenic Escherichia coli

The addition of reduced sulfur compounds (thiosulfate, cysteine, sodium hydrosulfite, and sodium metabisulfite) increased growth and fermentation of dilute acid hydrolysate of sugarcane bagasse by ethanologenic Escherichia coli (strains LY180, EMFR9, and MM160). With sodium metabisulfite (0.5mM), toxicity was sufficiently reduced that slurries of pretreated biomass (10% dry weight including fiber and solubles) could be fermented by E. coli strain MM160 without solid-liquid separation or cleanup of sugars. A 6-h liquefaction step was added to improve mixing. Sodium metabisulfite also caused spectral changes at wavelengths corresponding to furfural and soluble products from lignin. Glucose and cellobiose were rapidly metabolized. Xylose utilization was improved by sodium metabisulfite but remained incomplete after 144 h. The overall ethanol yield for this liquefaction plus simultaneous saccharification and co-fermentation process was 0.20 g ethanol/g bagasse dry weight, 250 L/tonne (61 gal/US ton).

Noise performance of a frequency nondegenerate phase-sensitive amplifier with unequalized inputs

For the first time to our knowledge, the noise performance of a frequency nondegenerate phase-sensitive amplifier (PSA) with unequalized input powers has been experimentally characterized, based on a fiber-based parametric copier-PSA scheme. Two different noise-figure (NF) definitions-separate and combined NFs-are provided and compared. The results show that the separate NF of the weaker input wave is lower than that of the stronger wave due to the correlated-light nature. When considering the combined NF, the optimal noise performance (0 dB NF) is obtained only when the input powers are equal. Experiments agree well with the theoretical predictions.

Field-quadrature and photon-number correlations produced by parametric processes

In a previous paper [Opt. Express 13, 4986 (2005)], formulas were derived for the field-quadrature and photon-number variances produced by multiple-mode parametric processes. In this paper, formulas are derived for the quadrature and number correlations. The number formulas are used to analyze the properties of basic devices, such as two-mode amplifiers, attenuators and frequency convertors, and composite systems made from these devices, such as cascaded parametric amplifiers and communication links. Amplifiers generate idlers that are correlated with the amplified signals, or correlate pre-existing pairs of modes, whereas attenuators decorrelate pre-existing modes. Both types of device modify the signal-to-noise ratios (SNRs) of the modes on which they act. Amplifiers decrease or increase the mode SNRs, depending on whether they are operated in phase-insensitive (PI) or phase-sensitive (PS) manners, respectively, whereas attenuators always decrease these SNRs. Two-mode PS links are sequences of transmission fibers (attenuators) followed by two-mode PS amplifiers. Not only do these PS links have noise figures that are 6-dB lower than those of the corresponding PI links, they also produce idlers that are (almost) completely correlated with the signals. By detecting the signals and idlers, one can eliminate the effects of electronic noise in the detectors.

A Selective Medium for the Isolation and Quantification of Bradyrhizobium japonicum and Bradyrhizobium elkanii Strains from Soils and Inoculants

The ecological examination of members of the family Rhizobiaceae has been hampered by the lack of a selective medium for isolation of root nodule bacteria from soil. A novel non-antibiotic-containing medium has been developed which allows selective isolation of Bradyrhizobium japonicum and B. elkanii strains from soil and inoculants. The medium, BJSM, is based on the resistance of B.japonicum and B. elkanii strains to more than 40 mug of the metals ions Zn and Co per ml. BJSM does not allow growth of Rhizobium sp. strains. We used BJSM to isolate bacteria from a Hubbard soil and from several commercially prepared soybean inoculants. Ninety-eight percent of the isolates obtained from Hubbard soil nodulated Glycine max cv. Kasota, and between 55 and 95% of the isolates from the commercial inoculants had the ability to nodulate soybeans. Numbers of bradyrhizobia obtained by using BJSM, strain-specific fluorescent antibodies, and the most-probable-number plant infection assay indicated that the three techniques were comparable in quantifying B. japonicum strains in soils and inoculants, although most-probable-number counts were generally 0.5 order of magnitude greater than those obtained by using BJSM. Results of our studies indicate that BJSM is useful for direct isolation and quantification of B. japonicum and B. elkanii from natural soils and inoculants. This medium may prove to be an important tool for autecological and enumeration studies of diverse populations of bradyrhizobia and as a quality control method for soybean inoculants.