This is the first report of a fully annotated genomic sequence of
Streptomyces spectabilis
NRRL-2792, isolated and identified by The Upjohn Company in 1961. The genome was assembled into a single ...scaffold for annotation and analysis. The chromosome is linear, 9.5 Mb in size which is one of the largest
Streptomyces
genomes yet described, has a G+C content of 72%, and encodes for approximately 7943 genes. Antibiotic Secondary Metabolite Analysis Shell (antiSMASH) and Basic Local Alignment Search Tool (BLAST) bioinformatics analyses identified six complete secondary metabolite biosynthetic gene clusters for ectoine, melanin, albaflavenone, spectinomycin, 2-methylisoborneol and coelichelin. Additionally, biosynthetic clusters were identified that shared ≥ 90% gene content with complestatin, hopene, neoaureothin, or undecylprodigiosin. Thirty-one other likely secondary metabolite gene clusters were identified by antiSMASH. BLAST identified two subsets of undecylprodigiosin biosynthetic genes at polar opposites of the chromosome; their duplication was subsequently confirmed by primer walking.
ABSTRACT
We present a study of photometric flares on 154 low-mass (≤0.2 M⊙) objects observed by the SPECULOOS-South Observatory from 2018 June 1 to 2020 March 23. In this sample, we identify 85 ...flaring objects, ranging in spectral type from M4 to L0. We detect 234 flares in this sample, with energies between 1029.2 and 1032.7 erg, using both automated and manual methods. With this work, we present the largest photometric sample of flares on late-M and ultra-cool dwarfs to date. By extending previous M dwarf flare studies into the ultra-cool regime, we find M5–M7 stars are more likely to flare than both earlier, and later, M dwarfs. By performing artificial flare injection-recovery tests, we demonstrate that we can detect a significant proportion of flares down to an amplitude of 1 per cent, and we are most sensitive to flares on the coolest stars. Our results reveal an absence of high-energy flares on the reddest dwarfs. To probe the relations between rotation and activity for fully convective stars, we extract rotation periods for fast rotators and lower-bound period estimates of slow rotators. These rotation periods span from 2.2 h to 65 d, and we find that the proportion of flaring stars increases for the most fastest rotators. Finally, we discuss the impact of our flare sample on planets orbiting ultra-cool stars. As stars become cooler, they flare less frequently; therefore, it is unlikely that planets around the most reddest dwarfs would enter the ‘abiogenesis’ zone or drive visible-light photosynthesis through flares alone.
The effects of diatom abundance and biogenic silica (BSi) deposition on the population growth of tintinnid ciliates were investigated using incubations of sub-surface waters (10 m depth) of Suruga ...Bay, Japan in April and November 2018. Seawater for incubation was pre-filtered using a 200-µm mesh to remove mesozooplankton grazers. Initial concentrations of dissolved inorganic nitrogen were similar in both seasons, but silicic acid and phosphate were higher in April than in November. This allowed us to observe the growth of planktonic communities under varied silicic acid availability and explore the effects of BSi accumulation and food availability on the growth of tintinnids. Phytoplankton blooms dominated by diatoms formed in both, April and November incubations, but their biomass was higher in April than in November, demonstrating the effects of nutrients, particularly silicic acid, on diatom growth. The BSi concentration increased in both incubations but was higher in April than in November, confirming the effects of diatom abundance and size on BSi deposition. Tintinnid biomass also increased in both incubations but was higher in April than in November, showing that the biomass of tintinnid was affected by the BSi concentration. Species composition of diatoms affected the species composition of tintinnids by providing selected material for the construction of their lorica. Moreover, the results showed that the food supply mainly provided by pico-nanoflagellates via microbial loop and detritus may limit tintinnids’ population growth in natural planktonic ecosystems and this demonstrates tintinnids’ role as top predators in the microbial loop
Marine phytoplankton production as well as biomass is globally significant. This study hypothesized that a mild increase in nutrients concentrations (by a factor 1–2 higher) from artificial upwelling ...in oligotrophic water can alter phytoplankton dynamics (biomass, composition and size), and consequently, phytoplankton-derived particulate organic carbon flux. Primary production, carbon biomass of different planktonic groups, and organic carbon remineralization were examined by incubating seawater collected from two oceanographic stations in the vicinities of Ikitsuki Island, Japan, in 2004 and 2005. Station C, located near to and downstream of an artificial seamount that generates upwelling, had higher nutrient concentrations and biomass (Chl. a and carbon) than Station O-2, which was upstream and far from the seamount. Phytoplankton biomass and primary production rates remained higher during incubation for station C than for station O-2 in both 2004 and 2005. Phytoplankton composition also differed between the two stations. Picophytoplankton contributions to total biomass were smaller at station C than at station O-2 while those of micro- and nanophytoplankton were higher at station C. The results of this study indicate that even a small increase in nutrient availability in oligotrophic waters can alter productivity, biomass, and phytoplankton composition. Additionally, around 4.0% of net primary production was estimated to escape from grazers and remineralization, instead sinking into deep ocean layers in the form of less easily degraded particles. The difference in net primary productivity between Stns. C and O-2 gave an estimation of excess production at Stn. C resulting from upwelled nutrients. Owing to this 1.3 to 1.5mg more carbon m−2d−1 is likely to be exported at Stn. C compared to Stn. O-2.
•Effect of mild artificial upwelling of nutrients on plankton dynamics was studied.•Mild nutrient upwelling can increase phytoplankton productivity and biomass.•Mild nutrient upwelling has implication in export and sequestration of carbon.
Alkenes are industrially important platform chemicals with broad applications. In this study, we report a direct microbial biosynthesis of terminal alkenes from fermentable sugars by harnessing a ...P450 fatty acid (FA) decarboxylase from Macrococcus caseolyticus (OleTMC). We first characterized OleTMC and demonstrated its in vitro H2O2-independent activities towards linear C10:0-C18:0 FAs, with higher activity for C16:0-C18:0 FAs. Next, we engineered a de novo alkene biosynthesis pathway, consisting of OleTMC and an engineered E. coli thioesterase (TesA) with compatible substrate specificities, and introduced this pathway into E. coli for terminal alkene biosynthesis from glucose. The recombinant E. coli EcNN101 produced a total of 17.78 ± 0.63 mg/L odd-chain terminal alkenes, comprising of 0.9% ± 0.5% C11 alkene, 12.7% ± 2.2% C13 alkene, 82.7% ± 1.7% C15 alkene, and 3.7% ± 0.8% C17 alkene, and a yield of 0.87 ± 0.03 (mg/g) on glucose. To improve alkene production, we identified and overcame the electron transfer limitation in OleTMC, by introducing a two-component redox system, consisting of a putidaredoxin reductase (CamA) and a putidaredoxin (CamB) from Pseudomonas putida, into EcNN101, and demonstrated the alkene production increased ~2.8 fold. Finally, to better understand the substrate specificities of OleTMC observed, we employed in silico protein modeling to illuminate the functional role of FA binding pocket.
•Characterize a novel P450 fatty acid decarboxylase, OleTMC, for alkene biosynthesis.•Demonstrate alkene biosynthesis directly from glucose in a recombinant E. coli.•Alleviate electron transfer limitation in OleTMC for improved alkene production.•Use in silico protein modeling to illuminate substrate specificity of OleTMC.
We present resistivity and magnetization measurements on proton-irradiated crystals demonstrating that the superconducting state in the doped topological insulator NbxBi2Se3 (x=0.25) is surprisingly ...robust against disorder-induced electron scattering. The superconducting transition temperature Tc decreases without indication of saturation with increasing defect concentration, and the corresponding scattering rates far surpass expectations based on conventional theory. The low-temperature variation of the London penetration depth Δλ(T) follows a power law Δλ(T)∼T2 indicating the presence of symmetry-protected point nodes. Our results are consistent with the proposed robust nematic Eu pairing state in this material.
ABSTRACT
The variability induced by precipitable water vapour (PWV) can heavily affect the accuracy of time-series photometric measurements gathered from the ground, especially in the near-infrared. ...We present here a novel method of modelling and mitigating this variability, as well as open-sourcing the developed tool – Umbrella. In this study, we evaluate the extent to which the photometry in three common bandpasses (r′, i′, z′), and SPECULOOS’ primary bandpass (I + z′), are photometrically affected by PWV variability. In this selection of bandpasses, the I + z′ bandpass was found to be most sensitive to PWV variability, followed by z′, i′, and r′. The correction was evaluated on global light curves of nearby late M- and L-type stars observed by SPECULOOS’ Southern Observatory (SSO) with the I + z′ bandpass, using PWV measurements from the LHATPRO and local temperature/humidity sensors. A median reduction in RMS of 1.1 per cent was observed for variability shorter than the expected transit duration for SSO’s targets. On timescales longer than the expected transit duration, where long-term variability may be induced, a median reduction in RMS of 53.8 per cent was observed for the same method of correction.
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