Extracellular siderophores from Aspergillus ochraceous.

A large number of iron-chelating compounds (siderophores) were isolated from supernatants of iron-deficient cultures of a mold isolate, subsequently identified as Aspergillus ochraceous . Siderophores in their iron chelate form were purified to homogeneity by using Bio-Gel P2, silica gel, and C-18 bonded silica gel (reverse-phase) columns. Most of these compounds, as identified by 1H and 13C nuclear magnetic resonance spectroscopy and X-ray crystallography, belong to the ferrichrome family. The organism produces ferrirubin and ferrichrysin as the predominant and the second major compound (62 and 15% of the total siderophores), respectively. Ferrichrysin appears as the first siderophore in the medium on day 2 of growth. Several of the other siderophores are novel and ranged in quantities from 0.2 to 5% of the total. The trivial names asperchrome A, B1, B2, C, D1, D2, and D3 are proposed for these novel compounds, which are all members of the ferrichrome family, and all but the first one contain a common Orn1 - Orn2 - Orn3 - Ser1 -Ser2-Gly cyclic hexapeptide ring with three dissimilar ornithyl delta-N-acyl groups. Another compound which appeared late in the growth period was similar to fusarinine C ( fusigen ). All of these compounds showed growth factor activity to various extents in bioassays with Arthrobacter flavescens Jg-9. None of these compounds showed antibacterial activity against Escherichia coli or Bacillus megaterium.     

Determination of Key Metabolites during Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine with Rhodococcus sp. Strain DN22

Rhodococcus sp. strain DN22 can convert hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to nitrite, but information on degradation products or the fate of carbon is not known. The present study describes aerobic biodegradation of RDX (175 μM) when used as an N source for strain DN22. RDX was converted to nitrite (NO₂⁻) (30%), nitrous oxide (N₂O) (3.2%), ammonia (10%), and formaldehyde (HCHO) (27%), which later converted to carbon dioxide. In experiments with ring-labeled [¹⁵N]-RDX, gas chromatographic/mass spectrophotometric (GC/MS) analysis revealed N₂O with two molecular mass ions: one at 44 Da, corresponding to ¹⁴N¹⁴NO, and the second at 45 Da, corresponding to ¹⁵N¹⁴NO. The nonlabeled N₂O could be formed only from -NO₂, whereas the ¹⁵N-labeled one was presumed to originate from a nitramine group (¹⁵N-¹⁴NO₂) in RDX. Liquid chromatographic (LC)-MS electrospray analyses indicated the formation of a dead end product with a deprotonated molecular mass ion [M-H] at 118 Da. High-resolution MS indicated a molecular formula of C₂H₅N₃O₃. When the experiment was repeated with ring-labeled [¹⁵N]-RDX, the [M-H] appeared at 120 Da, indicating that two of the three N atoms in the metabolite originated from the ring in RDX. When [U-¹⁴C]-RDX was used in the experiment, 64% of the original radioactivity in RDX incorporated into the metabolite with a molecular weight (MW) of 119 (high-pressure LC/radioactivity) and 30% in ¹⁴CO₂ (mineralization) after 4 days of incubation, suggesting that one of the carbon atoms in RDX was converted to CO₂ and the other two were incorporated in the ring cleavage product with an MW of 119. Based on the above stoichiometry, we propose a degradation pathway for RDX based on initial denitration followed by ring cleavage to formaldehyde and the dead end product with an MW of 119.     

Tight Coupling between Glucose and Mitochondrial Metabolism in Clonal ��-Cells Is Required for Robust Insulin Secretion

The biochemical mechanisms underlying glucose-stimulated insulin secretion from pancreatic β-cells are not completely understood. To identify metabolic disturbances in β-cells that impair glucose-stimulated insulin secretion, we compared two INS-1-derived clonal β-cell lines, which are glucose-responsive (832/13 cells) or glucose-unresponsive (832/2 cells). To this end, we analyzed a number of parameters in glycolytic and mitochondrial metabolism, including mRNA expression of genes involved in cellular energy metabolism. We found that despite a marked impairment of glucose-stimulated insulin secretion, 832/2 cells exhibited a higher rate of glycolysis. Still, no glucose-induced increases in respiratory rate, ATP production, or respiratory chain complex I, III, and IV activities were seen in the 832/2 cells. Instead, 832/2 cells, which expressed lactate dehydrogenase A, released lactate regardless of ambient glucose concentrations. In contrast, the glucose-responsive 832/13 line lacked lactate dehydrogenase and did not produce lactate. Accordingly, in 832/2 cells mRNA expression of genes for glycolytic enzymes were up-regulated, whereas mitochondria-related genes were down-regulated. This could account for a Warburg-like effect in the 832/2 cell clone, lacking in 832/13 cells as well as primary β-cells. In human islets, mRNA expression of genes such as lactate dehydrogenase A and hexokinase I correlated positively with HbA_1c levels, reflecting perturbed long term glucose homeostasis, whereas that of Slc2a2 (glucose transporter 2) correlated negatively with HbA_1c and thus better metabolic control. We conclude that tight metabolic regulation enhancing mitochondrial metabolism and restricting glycolysis in 832/13 cells is required for clonal β-cells to secrete insulin robustly in response to glucose. Moreover, a similar expression pattern of genes controlling glycolytic and mitochondrial metabolism in clonal β-cells and human islets was observed, suggesting that a similar prioritization of mitochondrial metabolism is required in healthy human β-cells. The 832 β-cell lines may be helpful tools to resolve metabolic perturbations occurring in Type 2 diabetes.     

Illuminating and mitigating the evolving impacts of COVID-19 on ethnocultural communities: a participatory action mixed-methods study

BACKGROUND:The COVID-19 pandemic has exacerbated disparities in poverty and illness for people in vulnerable circumstances in ethnocultural communities. We sought to understand the evolving impacts of COVID-19 on ethnocultural communities to inform intersectoral advocacy and community action.METHODS:The Illuminate Project used participatory action research, with cultural health brokers as peer researchers, from Sept. 21 to Dec. 31, 2020, in Edmonton, Alberta. Twenty-one peer researchers collected narratives from members of ethnocultural communities and self-interpreted them as they entered the narratives into the SenseMaker platform, a mixed-method data collection tool. The entire research team analyzed real-time, aggregate, quantitative and qualitative data to identify emerging thematic domains, then visualized these domains with social network analysis.RESULTS:Brokers serving diverse communities collected 773 narratives. Identified domains illuminate the evolving and entangled impacts of COVID-19 including the following: COVID-19 prevention and management; care of acute, chronic and serious illnesses other than COVID-19; maternal care; mental health and triggers of past trauma; financial insecurity; impact on children and youth and seniors; and legal concerns. We identified that community social capital and cultural brokering are key assets that facilitate access to formal health and social system supports.INTERPRETATION:The Illuminate Project has illustrated the entangled, systemic issues that result in poor health among vulnerable members of ethnocultural communities, and the exacerbating effects of COVID-19, which also increased barriers to mitigation. Cultural brokering and community social capital are key supports for people during the COVID-19 pandemic. These findings can inform policy to reduce harm and support community resiliency.

Mahatma Gandhi observed that “the true measure of any society can be found in how it treats its most vulnerable members.” Ethnocultural communities, defined by their unique shared characteristics (e.g., cultural traditions, language, country of origin),¹ face greater challenges and have higher rates of poverty and illness than the general Canadian population. Migration results in conditions that affect all social determinants of health and disproportionally affect health outcomes, herein referred to as vulnerable circumstances.^2,3 The emergence of major outbreaks of SARS-CoV-2 infections in ethnocultural communities highlights both the vulnerable circumstances of these communities and the disparities they face in accessing high-quality, culturally appropriate information and support.^4–7 Studies have shown substantial variation in deaths attributed to COVID-19 based on factors such as age, sex, ethnicity, length of time in Canada, income and education.^8–11 However, given the well-known gap in reporting comprehensive COVID-19 data in relation to race and ethnicity, efforts to measure its impact are hampered.^8–12 There is an urgent need to understand the evolving challenges of COVID-19 to inform action and public policy that can mitigate these challenges.To understand evolving situations of complexity and crisis, sensemaking, defined as “a continuous process to establish situational awareness,”¹³ is a crucial undertaking.¹⁴ Using participatory action research,^15–18 we sought to understand the evolving impacts of COVID-19 on ethnocultural communities to inform broader national efforts to migitate the impacts of COVID-19. Particularly, we sought to understand how the challenges of COVID-19 are entangled with contextual factors at multiple levels, how families and communities are leveraging strengths and social capital to adapt, and the role of cultural brokers in managing the crisis.     

The effect of norflurazon on protein composition and chlorophyll organization in pigment–protein complex of Photosystem II

The pyridazinone-type herbicide norflurazon SAN 9789 inhibiting the biosynthesis of long-chain carotenoids results in significant decrease in PS II core complexes and content of light-harvesting complex (LHC) polypeptides in the 29.5–21 kDa region. The Chl a forms at 668, 676, and 690 nm that belong to LHC and antenna part of PS I disappear completely after treatment. The intensity of the Chl b form at 648 nm is sharply decreased in treated seedlings grown under 30 or 100 lx light intensity. The bands of carotenoid absorption at 421, 448 (Chl a), 452, 480, 492, 496 (β-carotene), and 508 nm also disappear. The band shift from 740 to 720 nm and decrease in its intensity relative to the 687 nm emission peak in the low-temperature fluorescence spectrum (77 K) suggests a disturbance of energy transfer from LHC to the Chla form at 710–712 nm.     

Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcus sp.

The psychrotroph Rhodococcus sp. strain Q15 was examined for its ability to degrade individual n-alkanes and diesel fuel at low temperatures, and its alkane catabolic pathway was investigated by biochemical and genetic techniques. At 0 and 5°C, Q15 mineralized the short-chain alkanes dodecane and hexadecane to a greater extent than that observed for the long-chain alkanes octacosane and dotriacontane. Q15 utilized a broad range of aliphatics (C₁₀ to C₂₁ alkanes, branched alkanes, and a substituted cyclohexane) present in diesel fuel at 5°C. Mineralization of hexadecane at 5°C was significantly greater in both hydrocarbon-contaminated and pristine soil microcosms seeded with Q15 cells than in uninoculated control soil microcosms. The detection of hexadecane and dodecane metabolic intermediates (1-hexadecanol and 2-hexadecanol and 1-dodecanol and 2-dodecanone, respectively) by solid-phase microextraction–gas chromatography-mass spectrometry and the utilization of potential metabolic intermediates indicated that Q15 oxidizes alkanes by both the terminal oxidation pathway and the subterminal oxidation pathway. Genetic characterization by PCR and nucleotide sequence analysis indicated that Q15 possesses an aliphatic aldehyde dehydrogenase gene highly homologous to the Rhodococcus erythropolis thcA gene. Rhodococcus sp. strain Q15 possessed two large plasmids of approximately 90 and 115 kb (shown to mediate Cd resistance) which were not required for alkane mineralization, although the 90-kb plasmid enhanced mineralization of some alkanes and growth on diesel oil at both 5 and 25°C.     

Chemotaxis-mediated biodegradation of cyclic nitramine explosives RDX, HMX, and CL-20 by Clostridium sp. EDB2

Cyclic nitramine explosives, RDX, HMX, and CL-20 are hydrophobic pollutants with very little aqueous solubility. In sediment and soil environments, they are often attached to solid surfaces and/or trapped in pores and distribute heterogeneously in aqueous environments. For efficient bioremediation of these explosives, the microorganism(s) must access them by chemotaxis ability. In the present study, we isolated an obligate anaerobic bacterium Clostridium sp. strain EDB2 from a marine sediment. Strain EDB2, motile with numerous peritrichous flagella, demonstrated chemotactic response towards RDX, HMX, CL-20, and NO(2)(-). The three explosives were biotransformed by strain EDB2 via N-denitration with concomitant release of NO(2)(-). Biotransformation rates of RDX, HMX, and CL-20 by the resting cells of strain EDB2 were 1.8+/-0.2, 1.1+/-0.1, and 2.6+/-0.2nmol h(-1)mgwet biomass(-1) (mean+/-SD; n=3), respectively. We found that commonly seen RDX metabolites such as TNX, methylenedinitramine, and 4-nitro-2,4-diazabutanal neither produced NO(2)(-) during reaction with strain EDB2 nor they elicited chemotaxis response in strain EDB2. The above data suggested that NO(2)(-) released from explosives during their biotransformation might have elicited chemotaxis response in the bacterium. Biodegradation and chemotactic ability of strain EDB2 renders it useful in accelerating the bioremediation of explosives under in situ conditions.     

Fluorinated aminoglycosides and their mechanistic implication for aminoglycoside 3'-phosphotransferases from Gram-negative bacteria

Aminoglycoside 3'-phosphotransferases [APH(3')s] are important bacterial resistance enzymes for aminoglycoside antibiotics. These enzymes phosphorylate the 3'-hydroxyl of these antibiotics, a reaction that inactivates the drug. A series of experiments were carried out to shed light on the details of the turnover chemistry by these enzymes. Quench-flow pre-steady-state kinetic analyses of the reactions of Gram-negative APH(3') types Ia and IIa with kanamycin A, neamine, and their respective difluorinated analogues 4'-deoxy-4',4'-difluorokanamycin A and 4'-deoxy-4',4'-difluoroneamine were carried out, in conjunction with measurements of thio effect and viscosity studies. The fluorinated analogues were shown to be severely impaired as substrates for these enzymes. The magnitude of the effect of the impairment of the fluorinated substrates was in the same range as when the D198A mutant APH(3')-Ia was studied with nonfluorinated substrates. Residue 198 is the proposed active site base that promotes the aminoglycoside hydroxyl for phosphorylation. These findings collectively argue that the Gram-negative APH(3')s show significant nucleophilic participation in the transition state for the phosphate transfer reaction.     

Polyphenols of mature plant,seedling and tissue cultures of Theobroma cacao

The major flavone in mature cocoa leaves is isovitexin, with smaller amounts of vitexin and 7-O-glucosides of apigenin, luteolin and chrysoeriol. F