Methane oxidation is an important process to mitigate the emission of the greenhouse gas methane and further exacerbating of climate forcing. Both aerobic and anaerobic microorganisms have been reported to catalyze methane oxidation with only a few possible electron acceptors. Recently, new microorganisms were identified that could couple the oxidation of methane to nitrate or nitrite reduction. Here we investigated such an enrichment culture at the (meta) genomic level to establish a metabolic model of nitrate-driven anaerobic oxidation of methane (nitrate-AOM). Nitrate-AOM is catalyzed by an archaeon closely related to (reverse) methanogens that belongs to the ANME-2d clade, tentatively named Methanoperedens nitroreducens. Methane may be activated by methyl-CoM reductase and subsequently undergo full oxidation to carbon dioxide via reverse methanogenesis. All enzymes of this pathway were present and expressed in the investigated culture. The genome of the archaeal enrichment culture encoded a variety of enzymes involved in an electron transport chain similar to those found in Methanosarcina species with additional features not previously found in methane-converting archaea. Nitrate reduction to nitrite seems to be located in the pseudoperiplasm and may be catalyzed by an unusual Nar-like protein complex. A small part of the resulting nitrite is reduced to ammonium which may be catalyzed by a Nrf-type nitrite reductase. One of the key questions is how electrons from cytoplasmically located reverse methanogenesis reach the nitrate reductase in the pseudoperiplasm. Electron transport in M. nitroreducens probably involves cofactor F420 in the cytoplasm, quinones in the cytoplasmic membrane and cytochrome c in the pseudoperiplasm. The membrane-bound electron transport chain includes F420H2 dehydrogenase and an unusual Rieske/cytochrome b complex. Based on genome and transcriptome studies a tentative model of how central energy metabolism of nitrate-AOM could work is presented and discussed.

Microbial methane oxidation is an important process to reduce the emission of the greenhouse gas methane. Anaerobic microorganisms couple the oxidation of methane to the reduction of sulfate, nitrate and nitrite, and possibly oxidized iron and manganese minerals. In this article, we review the recent finding of the intriguing nitrate- and nitrite-dependent anaerobic oxidation of methane (AOM). Nitrate-dependent AOM is catalyzed by anaerobic archaea belonging to the ANME-2d clade closely related to Methanosarcina methanogens. They were named 'Candidatus Methanoperedens nitroreducens' and use reverse methanogenesis with the key enzyme methyl-coenzyme M (methyl-CoM) reductase for methane activation. Their major end product is nitrite which can be taken up by nitrite-dependent methanotrophs. Nitrite-dependent AOM is performed by the NC10 bacterium 'Candidatus Methylomirabilis oxyfera' that probably utilizes an intra-aerobic pathway through the dismutation of NO to N and O for aerobic methane activation by methane monooxygenase, yet being a strictly anaerobic microbe. Environmental distribution, physiological and biochemical aspects are discussed in this article as well as the cooperation of the microorganisms involved.

Microorganisms are main drivers of the sulfur, nitrogen and carbon biogeochemical cycles. These elemental cycles are interconnected by the activity of different guilds in sediments or wastewater treatment systems. Here, we investigated a nitrate-reducing microbial community in a laboratory-scale bioreactor model that closely mimicked estuary or brackish sediment conditions. The bioreactor simultaneously consumed sulfide, methane and ammonium at the expense of nitrate. Ammonium oxidation occurred solely by the activity of anammox bacteria identified as Candidatus Scalindua brodae and Ca. Kuenenia stuttgartiensis. Fifty-three percent of methane oxidation was catalyzed by archaea affiliated to Ca. Methanoperedens and 47% by Ca. Methylomirabilis bacteria. Sulfide oxidation was mainly shared between two proteobacterial groups. Interestingly, competition for nitrate did not lead to exclusion of one particular group. Metagenomic analysis showed that the most abundant taxonomic group was distantly related to Thermodesulfovibrio sp. (87-89% 16S rRNA gene identity, 52-54% average amino acid identity), representing a new family within the Nitrospirae phylum. A high quality draft genome of the new species was recovered, and analysis showed high metabolic versatility. Related microbial groups are found in diverse environments with sulfur, nitrogen and methane cycling, indicating that these novel Nitrospirae bacteria might contribute to biogeochemical cycling in natural habitats.

Introduction While chest x-rays (CXRs) represent a cost-effective imaging modality for developing countries like Pakistan, their utility for the prognostication of COVID-19 has been minimally explored. Thus, we describe the frequency and distribution of CXR findings, and their association with clinical outcomes of patients with COVID-19. Methods All adult (≥ 18 years) patients presenting between 28th February-31st May to the emergency department of a tertiary care hospital in Pakistan, who were COVID-19 positive on RT-PCR with CXR done on presentation, were included. A CXR Severity Score (CXR-SS) of 0–8 was used to quantify the extent of pulmonary infection on CXR, with a score of 0 being negative and 1–8 being positive. The patients’ initial CXR-SS and their highest CXR-SS over the hospital course were used for analysis, with cut-offs of 0–4 and 5–8 being used to assess association with clinical outcomes. Results A total of 150 patients, with 76.7% males and mean age 56.1 years, were included in this study. Initial CXR was positive in 80% of patients, and 30.7% of patients had an initial CXR-SS between 5–8. The mortality rate was 16.7% and 30.6% patients underwent ICU admission with intubation (ICU-Int). On multivariable analysis, initial CXR-SS (1.355 [1.136–1.616]) and highest CXR-SS (1.390 [1.143–1.690]) were predictors of ICU-Int, and ICU-Int was independently associated with both initial CXR-SS 5–8 (2.532 [1.109–5.782]) and highest CXR-SS 5–8 (3.386 [1.405–8.159]). Lastly, age (1.060 [1.009–1.113]), initial CXR-SS (1.278 [1.010–1.617]) and ICU-Int (5.047 [1.731–14.710]), were found to be independent predictors of mortality in our patients. Conclusion In a resource-constrained country like Pakistan, CXRs may have valuable prognostic utility in predicting ICU admission and mortality. Additional research with larger patient samples is needed to further explore the association of CXR findings with clinical outcomes.

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Summary Knowledge of the mechanisms by which fish excrete their metabolic nitrogenous waste and insights into nitrogen cycling in aquaculture systems is of utmost importance to improve the sustainable commercial production of fish. In fish, most nitrogenous waste is excreted via the gills as ammonia, a potentially toxic nitrogenous compound. In this study; activity assays, physiological experiments, molecular analysis and microscopy were used to show that the gills of fish harbor a unique combination of hitherto overlooked nitrogen‐cycle microorganisms that can theoretically detoxify excreted ammonia by converting it into inert dinitrogen gas. By doing so, these microorganisms may benefit from the ammonia supply by the host and prevent the build‐up of this compound to toxic concentrations. This novel relationship between vertebrates and microorganisms may shed new light on nitrogen handling by ammonotelic fish species.

Stroma mediated wound healing signals may share similarities with the ones produced by tumor’s microenvironment and their modulation may impact tumor response to the various anti-cancer treatments including radiation therapy. Therefore we conducted this study, to assess the crosstalk between stromal and carcinoma cells in response to radiotherapy by genetic modulation of the stroma and irradiation. We found that fibroblasts irrespective of their RhoB status do not modulate intrinsic radiosensitivity of TC-1 but produce diffusible factors able to modify tumor cell fate. Then we found that Wt and RhoB deficient fibroblasts stimulated TC-1 migration through distinct mechanisms which are TGF-β1 and MMP-mediated respectively. Lastly, we found that simultaneous irradiation of fibroblasts and TC-1 abrogated the pro-migratory phenotype by repression of TGF-β and MMP secretion. This last result is highly relevant to the clinical situation and suggests that conversely to, the current view; irradiated stroma would not enhance carcinoma migration and could be manipulated to promote anti-tumor immune response.

Pulmonary hamartomas are rare benign tumors consisting of multiple mesenchymal cell lines like cartilage, bone and fat. We discuss an interesting case of a 53-year-old male patient, who was referred to our clinic for persistent cough. Chest X-ray revealed a left suprahilar density associated with plate like atelectasis, which on chest CT was found to be a densely calcified nodule, causing narrowing of the left upper lobe (LUL) bronchus with calcified bilateral hilar lymph nodes. A bronchoscopy revealed a smooth endobronchial mass with calcification, which was removed. Histopathology revealed pulmonary hamartoma.