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Using a 12 ks archival Chandra X-ray Observatory ACIS-S observation on the massive globular cluster (GC) M14, we detect a total of 7 faint X-ray sources within its half-light radius at a |$0.5{\small --}7\, \mathrm{keV}$| depth of |$2.5\times 10^{31}\, \mathrm{erg s^{-1}}$|⁠. We cross-match the X-ray source positions with a catalogue of the Very Large Array radio point sources and a Hubble Space Telescope (HST) UV/optical/near-IR photometry catalogue, revealing radio counterparts to 2 and HST counterparts to 6 of the X-ray sources. In addition, we also identify a radio source with the recently discovered millisecond pulsar PSR 1737−0314A. The brightest X-ray source, CX1, appears to be consistent with the nominal position of the classic nova Ophiuchi 1938 (Oph 1938), and both Oph 1938 and CX1 are consistent with a UV-bright variable HST counterpart, which we argue to be the source of the nova eruption in 1938. This makes Oph 1938 the second classic nova recovered in a Galactic GC since Nova T Scorpii in M80. CX2 is consistent with the steep-spectrum radio source VLA8, which unambiguously matches a faint blue source; the steepness of VLA8 is suggestive of a pulsar nature, possibly a transitional millisecond pulsar with a late K dwarf companion, though an active galactic nucleus (AGN) cannot be ruled out. The other counterparts to the X-ray sources are all suggestive of chromospherically active binaries or background AGNs, so their nature requires further membership information. [ABSTRACT FROM AUTHOR]

Objectives To investigate the genetic context and transferability of the oxazolidinone resistance gene optrA in a Streptococcus parasuis isolate. Methods The optrA -carrying S. parasuis isolate SFJ45 was characterized by PCR, antimicrobial susceptibility testing, complete genome sequencing and bioinformatic analysis. The transferability of optrA was verified by conjugation, followed by SmaI-PFGE and Southern blotting. Results The S. parasuis isolate SFJ45 was positive for optrA , mef (A), msr (D), erm (B), tetAB (P)′, tet (M), aadE , aphA3 , catQ , dfrG and mdt (A), conferring an MDR phenotype. The optrA gene was flanked by IS S1N at both termini in the same orientation, representing a novel 8750 bp pseudo-compound transposon, organized as the IS S1N - hth - clb - 4hp-optrA - 2hp -IS S1N structure. The IS S1N - optrA -carrying transposon was further inserted within an integrative and conjugative element, ICE Spsu SFJ45, at 3′ end of the fda gene. Conjugative transfer of the IS S1N - optrA -carrying transposon with ICE Spsu SFJ45 was observed from S. parasuis to Streptococcus suis at a frequency of (1.01 ± 3.12) × 10−7. Conclusions IS S1N was found to be associated with optrA spreading for the first time. Integration of the IS S1N - optrA transposon within ICE Spsu SFJ45 may lead to the co-selection of optrA with other antimicrobial resistance genes, contributing to its horizontal transfer from S. parasuis to clinically more important bacterial pathogens. [ABSTRACT FROM AUTHOR]

Millisecond pulsars (MSPs) are faint X-ray sources commonly observed in Galactic globular clusters (GCs). In this work, we investigate 18 MSPs newly found in the GC Omega Centauri (ω Cen) and search for their X-ray counterparts using Chandra observations with a total exposure time of 290.9 ks. We identify confident X-ray counterparts for 11 of the MSPs, with 9 of them newly identified in this work based on their positions, spectral properties, and X-ray colours. The X-ray spectra of nine MSPs are well described by a neutron star hydrogen atmosphere model, while two MSPs are well fitted by a power-law model. The identified MSPs have X-ray luminosities ranging from 1.0 × 1030 to 1.4 × 1031 erg s−1. Additionally, for population comparison purposes, we study the X-ray counterpart to MSP E in the GC M71, and find its X-ray spectrum is well described by blackbody-like models with a luminosity of 1.9 × 1030 erg s−1. We investigate the empirical correlations between X-ray luminosities and minimum companion masses, as well as mass functions, of spider pulsars. Clear correlations are observed, with best-fitting functions of log10 L X = (1.0 ± 0.1)log10 M c , min + (32.5 ± 0.2) and (0.35 ± 0.04)log10MF + (32.71 ± 0.20), respectively, with an intrinsic scatter of log10 L X of ∼0.3, where L X is the 0.5–10 keV X-ray luminosity, M c , min is the minimum companion mass, and MF represents the mass function, in solar masses. [ABSTRACT FROM AUTHOR]

Using the Hubble Ultraviolet Globular Cluster Survey (HUGS) and additional HST archival data, we have carried out a search for optical counterparts to the low-luminosity Chandra X-ray sources in the globular cluster M4 (NGC 6121). We have also searched for optical or X-ray counterparts to radio sources detected by the VLA. We find 24 new confident optical counterparts to Chandra sources for a total of 40, including the 16 previously identified. Of the 24 new identifications, 18 are stellar coronal X-ray sources (active binaries, ABs), the majority located along the binary sequence in a V 606– I 814 colour–magnitude diagram and generally showing an H α excess. In addition to confirming the previously detected cataclysmic variable (CV, CX4), we identify one confident new CV (CX76), and two candidates (CX81 and CX101). One MSP is known in M4 (CX12), and another strong candidate has been suggested (CX1); we identify some possible MSP candidates among optical and radio sources, such as VLA20, which appears to have a white dwarf counterpart. One X-ray source with a sub-subgiant optical counterpart and a flat radio spectrum (CX8, VLA31) is particularly mysterious. The radial distribution of X-ray sources suggests a relaxed population of average mass |$\sim 1.2\!-\! 1.5\, \mbox{$\mathrm{ M_\odot} $}$|⁠. Comparing the numbers of ABs, MSPs, and CVs in M4 with other clusters indicates that AB numbers are proportional to cluster mass (primordial population), MSPs to stellar encounter rate (dynamically formed population), while CVs seem to be produced both primordially and dynamically. [ABSTRACT FROM AUTHOR]

Aims: Assessing the role of ramRsl, a gene absent in a lincomycin over‐producing strain, in the regulation of morphological development and lincomycin biosynthesis in Streptomyces lincolnensis. Methods and Results: The gene ramRsl was deleted from the wild‐type strain NRRL 2936 and the ΔramR mutant strain was characterized by a slower growth rate and a delayed morphological differentiation compared to the original strain NRRL 2936. Furthermore, the ΔramR produced 2.6‐fold more lincomycin than the original strain, and consistently the level of expression of all lincomycin cluster located genes was enhanced at 48 and 96 h in the ΔramR. Complementation of ΔramR with an intact copy of ramRsl restored all wild‐type features, whereas the over‐expression of ramRsl led to a reduction of 33% of the lincomycin yield. Furthermore, the level of expression of glnR, bldA and SLCG_2919, three of known lincomycin biosynthesis regulators, was lower in the ΔramR than in the original strain at the early stage of fermentation and we demonstrated, using electrophoretic mobility shift assay and XylE reporter assay, that glnR is a novel direct target of RamR. Conclusions: Altogether, these results indicated that, beyond promoting the morphological development, RamR regulates negatively lincomycin biosynthesis and positively the expression of the nitrogen regulator GlnR. Significance and Impact of the Study: We demonstrated that RamR plays a negative role in the regulation of lincomycin biosynthesis in S. lincolnensis. Interestingly, the deletion of this gene in other antibiotic‐producing Streptomyces strains might also increase their antibiotic‐producing abilities. [ABSTRACT FROM AUTHOR]

We present a comprehensive census of X-ray millisecond pulsars (MSPs) in 29 Galactic globular clusters (GCs), including 68 MSPs with confirmed X-ray luminosities and 107 MSPs with X-ray upper limits. We compile previous X-ray studies of GC MSPs, and add new analyses of six MSPs (PSRs J1326–4728A, J1326–4728B, J1518+0204C, J1717+4308A, J1737–0314A, and J1807–2459A) discovered in five GCs. Their X-ray spectra are well described by a single blackbody model, a single power-law model, or a combination of them, with X-ray luminosities ranging from 1.9 × 1030to 8.3 × 1031 erg s−1. We find that most detected X-ray MSPs have luminosities between ∼1030 and 3 × 1031 erg s−1. Redback pulsars are a relatively bright MSP population with X-ray luminosities of ∼2 × 1031–3 × 1032 erg s−1. Black widows show a bimodal distribution in X-ray luminosities, with eclipsing black widows between ∼7 × 1030 and 2 × 1031 erg s−1, while the two confirmed non-eclipsing black widows are much fainter, with LX of 1.5–3 × 1030 erg s−1, suggesting an intrinsic difference in the populations. We estimate the total number of MSPs in 36 GCs by considering the correlation between the number of MSPs and stellar encounter rate in GCs, and suggest that between 600 and 1500 MSPs exist in these 36 GCs. Finally, we estimate the number of X-ray-detectable MSPs in the Galactic bulge, finding that 1–86 MSPs with LX > 1033 erg s−1, and 20–900 MSPs with LX > 1032 erg s−1 should be detectable there. [ABSTRACT FROM AUTHOR]

We analyse 55 ks of Chandra X-ray observations of the Galactic globular cluster (GC) M13. Using the latest radio timing positions of six known millisecond pulsars (MSPs) in M13 from Wang et al. (2020), we detect confident X-ray counterparts to five of the six MSPs at X-ray luminosities of LX (0.3–8 keV)∼3 × 1030–1031 erg s−1, including the newly discovered PSR J1641+3627F. There are limited X-ray counts at the position of PSR J1641+3627A, for which we obtain an upper limit LX < 1.3 × 1030 erg s−1. We analyse X-ray spectra of all six MSPs, which are well described by either a single blackbody (BB) or a single power-law model. We also incorporate optical/UV imaging observations from the Hubble Space Telescope (HST) and find optical counterparts to PSR J1641+3627D and J1641+3627F. Our colour–magnitude diagrams indicate the latter contains a white dwarf, consistent with the properties suggested by radio timing observations. The counterpart to J1641+3627D is only visible in the V band; however, we argue that the companion to J1641+3627D is also a white dwarf, since we see a BB-like X-ray spectrum, while MSPs with non-degenerate companions generally show non-thermal X-rays from shocks between the pulsar and companion winds. Our work increases the sample of known X-ray and optical counterparts of MSPs in GCs. [ABSTRACT FROM AUTHOR]