Identification of a novel N-acetylmuramic acid (MurNAc) transporter in Tannerella forsythia.

Tannerella forsythia is a Gram-negative periodontal pathogen lacking the ability to undergo de novo synthesis of amino sugars N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) that form the disaccharide-repeating unit of the peptidoglycan backbone. T. forsythia relies on the uptake of these sugars from the environment, which is so far unexplored. Here, we identified a novel transporter system of T. forsythia involved in the uptake of MurNAc across the inner membrane and characterized a homolog of the Escherichia. coli MurQ etherase involved in the conversion of MurNAc-6P to GlcNAc-6P. The genes encoding these components were identified on a three gene cluster spanning Tanf_08375 to Tanf_08385 located downstream from a putative peptidoglycan recycling locus. We show that the three genes, Tanf_08375, Tanf_08380, and Tanf_08385, encoding a MurNAc transporter, a putative sugar kinase, and a MurQ etherase, respectively, are transcriptionally linked. Complementation of the Tanf_08375 and Tanf_08380 genes together in trans, but not individually rescued the inability of an E. coli mutant deficient in the PTS (phosphotransferase system)-dependent MurNAc transporter MurP as well as that of a double mutant deficient in MurP and components of the PTS system to grow on MurNAc. In addition, complementation with this two-gene construct in E. coli caused depletion of MurNAc in the medium, further confirming this observation. Our results show that the products of Tanf_08375 and Tanf_08380 constitute a novel non-PTS MurNAc transporter system that seems to be widespread among bacteria of the Bacteroidetes phylum. To the best of our knowledge, this is the first identification of a PTS-independent MurNAc transporter in bacteria. IMPORTANCE: In this study we report the identification of a novel transporter for peptidoglycan amino-sugar N-acetylmuramic acid (MurNAc) in the periodontal pathogen T. forsythia It has been known since the late 1980s that T. forsythia is a MurNAc auxotroph relying on environmental sources for this essential sugar. Most sugar transporters, and the MurNAc transporter MurP in particular require a PTS phosho-relay to drive the uptake and concurrent phosphorylation of the sugar through the inner membrane in Gram-negative bacteria. Our study uncovered a novel type of PTS-independent MurNAc transporter, and although so far unique to T. forsythia, may be present in a range of bacteria both of the oral cavity and gut especially of the phylum Bacteroidetes

Influence of vessel characteristics and atmospheric processes on the gas and particle phase of ship emission plumes: In-situ measurements in the Mediterranean Sea and around the Arabian Peninsula

252 emission plumes of ships operating in the Mediterranean Sea and around the Arabian Peninsula were investigated using a comprehensive dataset of gas and submicron particle phase properties measured during the two-month shipborne AQABA field campaign in summer 2017. The post-measurement identification of the corresponding ship emission events in the measured data included the determination of the plume sources (up to 38 km away) as well as of the plume ages (up to 115 min) and was based on commercially available historical records of the Automatic Identification System. The dispersion lifetime of chemically inert CO2 in the ship emission plumes was determined as (70 ± 15) min, resulting in levels indistinguishable from the marine background after (260 ± 60) min. Emission factors (EFs) as quantities that are independent of plume dilution were calculated and used for the investigation of influences on ship emission plumes caused by ship characteristics and the combustion process as well as by atmospheric processes during the early stage of exhaust release and during plume aging. Combustion efficiency and therefore emission factors of black carbon and NOX were identified to depend mostly on the vessel speed and gross tonnage. Moreover, larger ships, associated with higher engine power were found to use fuel with higher sulfur content and have higher gas phase SO2, particulate sulfate, particulate organics and particulate matter EFs. Despite the independence of EFs on dilution, significant influence of the ambient wind speed on the particle number and mass EFs was observed that can be traced back to enhanced particle coagulation in case of slower dilution and suppressed vapor condensation on particles in case of faster dilution of the emission plume. Atmospheric reactions and processes in ship emission plumes were investigated that include NOX and O3 chemistry, gas-to-particle conversion of NOX and SO2 and the neutralization of acids in the particle phase through the uptake of ambient gas phase ammonia, the latter two of which cause the inorganic particulate content to increase and the organic fraction to decrease with increasing plume age. The results enable identification of the most important influences on (or processes in) ship emission plumes and to describe those quantitatively by parameterizations, which could be used for further refinement of atmospheric models

Gut microbiome responds to alteration in female sex hormone status and exacerbates metabolic dysfunction

ABSTRACTWomen are at significantly greater risk of metabolic dysfunction after menopause, which subsequently leads to numerous chronic illnesses. The gut microbiome is associated with obesity and metabolic dysfunction, but its interaction with female sex hormone status and the resulting impact on host metabolism remains unclear. Herein, we characterized inflammatory and metabolic phenotypes as well as the gut microbiome associated with ovariectomy and high-fat diet feeding, compared to gonadal intact and low-fat diet controls. We then performed fecal microbiota transplantation (FMT) using gnotobiotic mice to identify the impact of ovariectomy-associated gut microbiome on inflammatory and metabolic outcomes. We demonstrated that ovariectomy led to greater gastrointestinal permeability and inflammation of the gut and metabolic organs, and that a high-fat diet exacerbated these phenotypes. Ovariectomy also led to alteration of the gut microbiome, including greater fecal β-glucuronidase activity. However, differential changes in the gut microbiome only occurred when fed a low-fat diet, not the high-fat diet. Gnotobiotic mice that received the gut microbiome from ovariectomized mice fed the low-fat diet had greater weight gain and hepatic gene expression related to metabolic dysfunction and inflammation than those that received intact sham control-associated microbiome. These results indicate that the gut microbiome responds to alterations in female sex hormone status and contributes to metabolic dysfunction. Identifying and developing gut microbiome-targeted modulators to regulate sex hormones may be useful therapeutically in remediating menopause-related diseases

Measurement report: Observation-based formaldehyde production rates and their relation to OH reactivity around the Arabian Peninsula

Formaldehyde (HCHO) is the most abundant aldehyde in the troposphere. While its background-mixing ratio is mostly determined by the oxidation of methane, in many environments, especially in the boundary layer, HCHO can have a large variety of precursors, in particular biogenic and anthropogenic volatile organic compounds (VOCs) and their oxidation products. Here we present shipborne observations of HCHO, hydroxyl radical (OH) and OH reactivity (R(OH)), obtained during the Air Quality and Climate Change in the Arabian Basin (AQABA) campaign in summer 2017. The loss rate of HCHO was inferred from its reaction with OH, measured photolysis rates, and dry deposition. In photo-stationary state, the HCHO loss is balanced by production via OH initiated degradation of volatile organic compounds (VOCs), photolysis of oxygenated volatile organic compounds (OVOCs) and the ozonolysis of alkenes. The slope α from a scatter plot of the HCHO production rate versus the product of R(OH) and OH yields the fraction of R(OH) that contributes to HCHO production. Values of α varied between less than 2 % in rather clean air over the Arabian Sea and the southern Red Sea, and up to 32 % over the polluted Arabian Gulf (also known as the Persian Gulf), signifying that polluted areas harbour a larger variety of HCHO precursors. The HCHO yield from R(OH) depends on the absolute and relative contributions of alkanes, alkenes, oxygenated volatile organic compounds (OVOCs) and aromatics to R(OH), while no significant correlation to NOx mixing ratios was found, indicating that HCHO production was not NOx limited

Reactive nitrogen around the Arabian Peninsula and in the Mediterranean Sea during the 2017 AQABA ship campaign

We present shipborne measurements of NOx (≡ NO + NO2) and NOy (≡ NOx+ gas- and particle-phase organic and inorganic oxides of nitrogen) in summer 2017 as part of the expedition “Air Quality and climate change in the Arabian BAsin” (AQABA). The NOx and NOz (≡ NOy-NOx) measurements, made with a thermal dissociation cavity ring-down spectrometer (TD-CRDS), were used to examine the chemical mechanisms involved in the processing of primary NOx emissions and their influence on the NOy budget in chemically distinct marine environments, including the Mediterranean Sea, the Red Sea, and the Arabian Gulf, which were influenced to varying extents by emissions from shipping and oil and gas production. Complementing the TD-CRDS measurements, NO and NO2 data sets from a chemiluminescence detector (CLD) were used in the analysis. In all regions, we find that NOx is strongly connected to ship emissions, both via direct emission of NO and via the formation of HONO and its subsequent photolytic conversion to NO. The role of HONO was assessed by calculating the NOx production rate from its photolysis. Mean NO2 lifetimes were 3.9 h in the Mediterranean Sea, 4.0 h in the Arabian Gulf, and 5.0 h in the Red Sea area. The cumulative loss of NO2 during the night (reaction with O3) was more important than daytime losses (reaction with OH) over the Arabian Gulf (by a factor 2.8) and over the Red Sea (factor 2.9), whereas over the Mediterranean Sea, where OH levels were high, daytime losses dominated (factor 2.5). Regional ozone production efficiencies (OPEs; calculated from the correlation between Ox and NOz, where Ox= O3+ NO2) ranged from 10.5 ± 0.9 to 19.1 ± 1.1. This metric quantifies the relative strength of photochemical O3 production from NOx compared to the competing sequestering into NOz species. The largest values were found over the Arabian Gulf, consistent with high levels of O3 found in that region (10–90 percentiles range: 23–108 ppbv). The fractional contribution of individual NOz species to NOy exhibited a large regional variability, with HNO3 generally the dominant component (on average 33 % of NOy) with significant contributions from organic nitrates (11 %) and particulate nitrates in the PM1 size range (8 %)

Reactive nitrogen around the Arabian Peninsula and in the Mediterranean Sea during the 2017 AQABA ship campaign

We present ship-borne measurements of NOx (≡ NO + NO2) and NOy (≡ NOx + gas- and particle-phase organic and inorganic oxides of nitrogen) in summer 2017 as part of the expedition "Air Quality and climate change in the Arabian Basin" (AQABA). The NOx and NOz (≡ NOy–NOx) measurements, made with a thermal dissociation cavity-ringdown-spectrometer (TD-CRDS), were used to examine the chemical mechanisms involved in the processing of primary NOx emissions and their influence on the NOy budget in chemically distinct marine environments, including the Mediterranean Sea, the Red Sea, and the Arabian Gulf which were influenced to varying extents by emissions from shipping and oil and gas production. In all regions, we find that NOx is strongly connected to ship emissions, both via direct emission of NO and via the formation of HONO and its subsequent photolytic conversion to NO. Mean NO2 lifetimes were 3.9 hours in the Mediterranean Sea, 4.0 hours in the Arabian Gulf and 5.0 hours in the Red Sea area. The cumulative loss of NO2 during the night (reaction with O3) was more important than daytime losses (reaction with OH) over the Arabian Gulf (by a factor 2.8) and over the Red Sea (factor 2.9), whereas over the Mediterranean Sea, where OH levels were high, daytime losses dominated (factor 2.5). Regional ozone production efficiencies (OPE) ranged from 10.5 ± 0.9 to 19.1 ± 1.1. This metric quantifies the relative strength of photochemical O3 production from NOx, compared to the competing sequestering into NOz species. The largest values were found over the Arabian Gulf, consistent with high levels of O3 found in that region (10–90 percentiles range: 23–108 ppbv). The fractional contribution of individual NOz species to NOy exhibited a large regional variability, with HNO3 generally the dominant component (on average 33 % of NOy) with significant contributions from organic nitrates (11 %) and particulate nitrates in the PM1 size range (8 %)