98 research outputs found
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Steady-State Growth under Inorganic Carbon Limitation Conditions Increases Energy Consumption for Maintenance and Enhances Nitrous Oxide Production in Nitrosomonas europaea
Nitrosomonas europaea is a chemolithoautotrophic bacterium that oxidizes ammonia (NHâ) to obtain energy for growth on carbon dioxide (COâ) and can also produce nitrous oxide (NâO), a greenhouse gas. We interrogated the growth, physiological, and transcriptome responses of N. europaea to conditions of replete (>5.2 mM) and limited inorganic carbon (IC) provided by either 1.0 mM or 0.2 mM sodium carbonate (NaâCOâ) supplemented with atmospheric COâ. IC-limited cultures oxidized 25 to 58% of available NHâ to nitrite, depending on the dilution rate and NaâCOâ concentration. IC limitation resulted in a 2.3-fold increase in cellular maintenance energy requirements compared to those for NHâ-limited cultures. Rates of NâO production increased 2.5- and 6.3-fold under the two IC-limited conditions, increasing the percentage of oxidized NHâ-N that was transformed to NâO-N from 0.5% (replete) up to 4.4% (0.2 mM NaâCOâ). Transcriptome analysis showed differential expression (P †0.05) of 488 genes (20% of inventory) between replete and IC-limited conditions, but few differences were detected between the two IC-limiting treatments. IC-limited conditions resulted in a decreased expression of ammonium/ammonia transporter and ammonia monooxygenase subunits and increased the expression of genes involved in Câ metabolism, including the genes for RuBisCO (cbb gene cluster), carbonic anhydrase, folate-linked metabolism of Câ moieties, and putative C salvage due to oxygenase activity of RuBisCO. Increased expression of nitrite reductase (gene cluster NE0924 to NE0927) correlated with increased production of NâO. Together, these data suggest that N. europaea adapts physiologically during IC-limited steady-state growth, which leads to the uncoupling of NHâ oxidation from growth and increased NâO production.
IMPORTANCE: Nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, is an important process in the global nitrogen cycle. This process is generally dependent on ammonia-oxidizing microorganisms and nitrite-oxidizing bacteria. Most nitrifiers are chemolithoautotrophs that fix inorganic carbon (COâ) for growth. Here, we investigate how inorganic carbon limitation modifies the physiology and transcriptome of Nitrosomonas europaea, a model ammonia-oxidizing bacterium, and report on increased production of NâO, a potent greenhouse gas. This study, along with previous work, suggests that inorganic carbon limitation may be an important factor in controlling NâO emissions from nitrification in soils and wastewater treatment
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Bacterial Resistance to Antisense Peptide-Phosphorodiamidate Morpholino Oligomers
Peptide phosphorodiamidate morpholino oligomers (PPMO) are synthetic DNA mimics that bind complementary RNA and inhibit bacterial gene expression. (RFF)âRXB- AcpP PPMO (R, arginine; F, phenylalanine; X, 6-aminohexanoic acid; B, ÎČ-alanine) is complementary to 11 bases of the essential gene acpP (encodes acyl carrier protein). The MIC of (RFF)âRXB-AcpP was 2.5 ÎŒM (14 ÎŒg/ml) in Escherichia coli W3110. The rate of spontaneous resistance of E. coli to (RFF)âRXB-AcpP was 4 x 10â»â· mutations/cell division. A spontaneous (RFF)âRXB-AcpP-resistant mutant (PR200.1) was isolated. The MIC of (RFF)âRXB-AcpP was 40 ÎŒM (224 ÎŒg/ml) in PR200.1. The MICs of standard antibiotics were identical in PR200.1 and W3110. The sequence of acpP was identical in PR200.1 and W3110. PR200.1 was also resistant to other PPMOs conjugated to (RFF)âRXB or peptides with a similar composition or pattern of cationic and non-polar residues. Genomic sequencing of PR200.1 identified a mutation in sbmA, which encodes an active transport protein. In separate experiments, a (RFF)âRXB-AcpP-resistant isolate (RR3) was selected from a transposome library, and the insertion was mapped to sbmA. Genetic complementation of PR200.1 or RR3 with sbmA restored susceptibility to (RFF)âRXB-AcpP. Deletion of sbmA caused resistance to (RFF)âRXB-AcpP. We conclude that resistance to (RFF)âRXB-AcpP was linked to the peptide and not the PMO, dependent on the composition or repeating pattern of amino acids, and caused by mutations in sbmA. The data further suggest that (RFF)âR-XB PPMOs may be transported across the plasma membrane by SbmA
Targeting RNA Polymerase Primary Ï70 as a Therapeutic Strategy against Methicillin-Resistant Staphylococcus aureus by Antisense Peptide Nucleic Acid
BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) causes threatening infection-related mortality worldwide. Currently, spread of multi-drug resistance (MDR) MRSA limits therapeutic options and requires new approaches to "druggable" target discovery, as well as development of novel MRSA-active antibiotics. RNA polymerase primary Ïâ·â° (encoded by gene rpoD) is a highly conserved prokaryotic factor essential for transcription initiation in exponentially growing cells of diverse S. aureus, implying potential for antisense inhibition. METHODOLOGY/PRINCIPAL FINDINGS: By synthesizing a serial of cell penetrating peptide conjugated peptide nucleic acids (PPNAs) based on software predicted parameters and further design optimization, we identified a target sequence (234 to 243 nt) within rpoD mRNA conserved region 3.0 being more sensitive to antisense inhibition. A (KFF)âK peptide conjugated 10-mer complementary PNA (PPNA2332) was developed for potent micromolar-range growth inhibitory effects against four pathogenic S. aureus strains with different resistance phenotypes, including clinical vancomycin-intermediate resistance S. aureus and MDR-MRSA isolates. PPNA2332 showed bacteriocidal antisense effect at 3.2 fold of MIC value against MRSA/VISA Mu50, and its sequence specificity was demonstrated in that PPNA with scrambled PNA sequence (Scr PPNA2332) exhibited no growth inhibitory effect at higher concentrations. Also, PPNA2332 specifically interferes with rpoD mRNA, inhibiting translation of its protein product Ïâ·â° in a concentration-dependent manner. Full decay of mRNA and suppressed expression of Ïâ·â° were observed for 40 ”M or 12.5 ”M PPNA2332 treatment, respectively, but not for 40 ”M Scr PPNA2332 treatment in pure culture of MRSA/VISA Mu50 strain. PPNA2332 (â„1 ”M) essentially cleared lethal MRSA/VISA Mu50 infection in epithelial cell cultures, and eliminated viable bacterial cells in a time- and concentration- dependent manner, without showing any apparent toxicity at 10 ”M. CONCLUSIONS: The present result suggested that RNAP primary Ïâ·â° is a very promising candidate target for developing novel antisense antibiotic to treat severe MRSA infections
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2011 Seed production research at Oregon State University, USDA-ARS cooperating
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2010 Seed production research at Oregon State University, USDA-ARS cooperating
En kunnskapsbasert finansnĂŠring
Prosjektet âEn kunnskapsbasert finansnĂŠringâ inngĂ„r som delprosjekt i det store nasjonale forskningsprosjektet âEt kunnskapsbasert Norgeâ som gjennomfĂžres ved HandelshĂžyskolen BI under ledelse av professor Torger Reve.
Norsk nÊringsliv er avhengig av en velfungerende finansnÊring. Denne nÊringen fungerer pÄ mange mÄter som et nav for de andre nÊringene i Þkonomien. For at nÊringslivet skal kunne skape vekst, mÄ det kanaliseres kapital til prosjekter som har hÞy lÞnnsomhet og evne til verdiskaping. Dersom bedriftene selv ikke har denne kapitalen tilgjengelig er det nÞdvendig med ekstern kapitaltilfÞrsel. Det er her finansnÊringen bidrar, bÄde med kapital og kompetanse om hvor kapitalen bÞr kanaliseres. Finansmarkedet fungerer ogsÄ som et korrektiv til bedriftenes atferd. Bedrifter som gjÞr det bra blir premiert gjennom hÞyere verdsetting pÄ bÞrs, mens de som gjÞr det dÄrlig opplever fallende kurser. PÄ denne mÄten fÄr eierne et tydelig signal om hvor godt bedriften er styrt og kan pÄ denne bakgrunn legge opp til endringer i bedriftens strategi. Videre spiller finansmarkedet en viktig rolle gjennom Ä ivareta bÄde nÊringslivets, husholdningenes og offentlig sektors behov for likviditet gjennom Ä tilby regulÊre banktjenester. NÊringen har ogsÄ en sentral oppgave gjennom Ä avdempe risiko gjennom ulike forsikringsprodukter. Sist, men ikke minst, har finansnÊringen en formidlerrolle gjennom Ä bistÄ aktÞrer i Þkonomien i Ä flytte verdier seg imellom. Vi snakker med andre ord om en nÊring med mange aktivitetsomrÄder og som i all hovedsak har forankret sine aktiviteter i andre aktÞrers Þkonomiske aktivitet
Quorum Quenching of Nitrobacter winogradskyi Suggests that Quorum Sensing Regulates Fluxes of Nitrogen Oxide(s) during Nitrification
Quorum sensing (QS) is a widespread process in bacteria used to coordinate gene expression with cell density, diffusion dynamics, and spatial distribution through the production of diffusible chemical signals. To date, most studies on QS have focused on model bacteria that are amenable to genetic manipulation and capable of high growth rates, but many environmentally important bacteria have been overlooked. For example, representatives of proteobacteria that participate in nitrification, the aerobic oxidation of ammonia to nitrate via nitrite, produce QS signals called acyl-homoserine lactones (AHLs). Nitrification emits nitrogen oxide gases (NO, NO2, and N2O), which are potentially hazardous compounds that contribute to global warming. Despite considerable interest in nitrification, the purpose of QS in the physiology/ecology of nitrifying bacteria is poorly understood. Through a quorum quenching approach, we investigated the role of QS in a well-studied AHL-producing nitrite oxidizer, Nitrobacter winogradskyi. We added a recombinant AiiA lactonase to N. winogradskyi cultures to degrade AHLs to prevent their accumulation and to induce a QS-negative phenotype and then used mRNA sequencing (mRNA-Seq) to identify putative QS-controlled genes. Our transcriptome analysis showed that expression of nirK and nirK cluster genes (ncgABC) increased up to 19.9-fold under QS-proficient conditions (minus active lactonase). These data led to us to query if QS influenced nitrogen oxide gas fluxes in N. winogradskyi. Production and consumption of NOx increased and production of N2O decreased under QS-proficient conditions. Quorum quenching transcriptome approaches have broad potential to identify QS-controlled genes and phenotypes in organisms that are not genetically tractable
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