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Carbon Source (carbon + source)
Kinds of Carbon Source Terms modified by Carbon Source Selected AbstractsCARBON SOURCES AND THEIR EFFECT ON GROWTH, ACETIC ACID AND ETHANOL PRODUCTION BY BRETTANOMYCES BRUXELLENSIS IN BATCH CULTUREJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2007M.G. AGUILAR USCANGA ABSTRACT The influence of available low-cost carbohydrates as carbon sources on Brettanomyces bruxellensis growth, acetic acid and ethanol production was studied in order to ascertain the viability of this yeast to eventually become an industrial acetic acid producer. Six different raw materials were included as carbon sources (glucose, sugarcane molasses, refined cane sugar, pineapple, sugarcane and beet juices). B. bruxellensis develops in a complex culture medium like plant juices and sugarcane molasses better than in a medium with a simple carbohydrate such as glucose. The maximum acid acetic yield (0.24 g/g) and productivity (0.14 g/L/h) were attained in tests carried out with sugarcane molasses containing 60 g/L sucrose. The strain produced low levels of ethanol in a refined sugarcane medium, but was able to produce a substantial quantity of acetic acid (13 g/L). [source] Template Synthesis of Aligned Carbon Nanotube Arrays using Glucose as a Carbon Source: Pt Decoration of Inner and Outer Nanotube Surfaces for Fuel-Cell Catalysts,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2008Zhenhai Wen A facile method is developed to synthesize aligned arrays of open-ended carbon nanotubes (CNTs) via in situ glucose polymerization in the inner pores of anodic aluminum oxide templates under hydrothermal conditions, followed by carbonization at high temperature. Pt nanoparticles are decorated on the surfaces of the as-prepared CNTs using the incipient wet method based on the use of NaBH4 as a reductant. Characterization of the resulting structures by transmission electron microscopy and field-emission scanning electron microscopy demonstrates that the Pt nanoparticles are anchored on both the inner and outer walls of CNTs, thus giving rise to a shell,core,shell-like nanotube composite. The electrocatalytic properties of the Pt,CNT,Pt electrodes are investigated for methanol oxidation by cyclic voltammetry and chronoamperometric measurements. It is found that the hybrid electrodes show superior catalytic performance compared to commercial carbon-black-supported Pt. The increased catalytic efficiency of Pt might be a result of the unique morphology of these structures. [source] Utilization of an Alternative Carbon Source for Efficient Production of Human ,1 -Antitrypsin by Genetically Engineered Rice Cell CultureBIOTECHNOLOGY PROGRESS, Issue 3 2001Masaaki Terashima Human ,1 -antitrypsin was produced by genetically engineered rice cells using promoter and signal peptide of a rice ,-amylase isozyme. Batch and continuous cultures were employed to investigate the effects of alternative carbon sources on the ,1 -antitrypsin production. While this expression system is inducible by sugar depletion, we have found that the productivity of ,1 -antitrypsin increased 2.4- to 3.4-fold, compared with the control medium without carbon source, in medium containing an alternative carbon source, such as pyruvic acid and glyoxylic acid. The accumulated ,1 -antitrypsin in the medium containing pyruvic acid reached 18.2,24.2 mg/g-dry cell in 50,70 h by batch culture. [source] Effect of Different Carbon Sources on the Production of Succinic Acid Using Metabolically Engineered Escherichia coliBIOTECHNOLOGY PROGRESS, Issue 2 2007Christian Andersson Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L,1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g,1). When using xylose as a carbon source, a yield of 0.50 g g,1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g,1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g,1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25,40 g L,1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7,6.7 and 0,2.7 g L,1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L,1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed. [source] Nutritional factors determining sclerotial formation of Polyporus umbellatusLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2009Y.-Y. Liu Abstract Aims:, To find out which nutritional condition is the determining factor for sclerotial formation of Polyporus umbellatus. Methods and Results:, The nutritional requirements of 15 carbohydrates, ten nitrogen compounds, eight vitamins and eight mineral elements were studied for their effects on mycelial growth and sclerotial formation of Polyporus umbellatus using the one-factor-at-a-time method. Only fructose could induce sclerotial formation of P.,umbellatus. An additional test indicated that nitrogen source categories influenced sclerotial formation significantly and that peptone was found to be the best for sclerotial production. Through an orthogonal matrix test, the effects of carbon/nitrogen factors on sclerotial formation were found be in the order: fructose > interaction between fructose and peptone > peptone. The optimal concentration for sclerotial formation was determined to be 50·0 g l,1 fructose and 4·0 g l,1 peptone. Conclusions:, Carbon source is the factor determining sclerotial formation of Polyporus umbellatus. Nitrogen source can influence such a morphological transformation significantly. The categories of vitamin and mineral element do not have relationship with the sclerotial formation. Significance and Impact of the Study:, This study provides the preparatory knowledge for the completely artificial culture of Polyporus umbellatus for its sclerotium. [source] Carbon sources of Amazonian fisheriesFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2000E. Benedito-Cecilio Variation in the seasonal and spatial isotopic composition of plant C4 (aquatic macrophytes) and C3 (forest, C3 aquatic macrophytes and algae), and that of fish [Prochilodus nigricans Agassiz, Mylossoma duriventre (Cuvier), Colossoma macropomum (Cuvier), Semaprochilodus insignis (Schomburgk) and S. taeniurus Steindachner in the Amazon floodplain were analysed to test whether the fisheries deliver plant carbon to the population of Manaus in the same proportion as it is available in the floodplain. The contribution of C4 plants was significantly lower in 13C during the season of high water levels and increased toward the west of the basin. Mylossoma duriventre and C. macropomum changed ,13C levels, while the ,13C of P. nigricans and C. macropomum shifted spatially. The contribution of C4 to the fisheries yield was small. C3 plants (excluding phytoplankton) also contributed less than expected. This was explained by the importance of detritivores to the yield of the fisheries and the dependence of these species on algal carbon. [source] Production of ,-Amylase and Glucoamylase by a New Isolate of Trichoderma sp.ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2004Using Sorghum Starch as a Carbon Source The performance of a new Trichoderma sp. isolate to produce extracellular ,-amylase and glucoamylase from raw sorghum starch was evalutated. To reduce the costs of starch saccharification and the consumption of amylolytic enzymes, this microorganism has been used for the first time in cultivations using such a carbon source without any prior gelatinization. [source] Pseudomonas fluorescens orchestrates a fine metabolic-balancing act to counter aluminium toxicityENVIRONMENTAL MICROBIOLOGY, Issue 6 2010Joseph Lemire Summary Aluminium (Al), an environmental toxin, is known to disrupt cellular functions by perturbing iron (Fe) homeostasis. However, Fe is essential for such metabolic processes as the tricarboxylic acid (TCA) cycle and oxidative phosphorylation, the two pivotal networks that mediate ATP production during aerobiosis. To counter the Fe conundrum induced by Al toxicity, Pseudomonas fluorescens utilizes isocitrate lyase and isocitrate dehydrogenase-NADP dependent to metabolize citrate when confronted with an ineffective aconitase provoked by Al stress. By invoking fumarase C, a hydratase devoid of Fe, this microbe is able to generate essential metabolites. To compensate for the severely diminished enzymes like Complex I, Complex II and Complex IV, the upregulation of a H2O-generating NADH oxidase enables the metabolism of citrate, the sole carbon source via a modified TCA cycle. The overexpression of succinyl-CoA synthetase affords an effective route to ATP production by substrate-level phosphorylation in the absence of O2. This fine metabolic balance enables P. fluorescens to survive the dearth of bioavailable Fe triggered by an Al environment, a feature that may have potential applications in bioremediation technologies. [source] The microbial community of Vetiver root and its involvement into essential oil biogenesisENVIRONMENTAL MICROBIOLOGY, Issue 10 2008Luigi Del Giudice Summary Vetiver is the only grass cultivated worldwide for the root essential oil, which is a mixture of sesquiterpene alcohols and hydrocarbons, used extensively in perfumery and cosmetics. Light and transmission electron microscopy demonstrated the presence of bacteria in the cortical parenchymatous essential oil-producing cells and in the lysigen lacunae in close association with the essential oil. This finding and the evidence that axenic Vetiver produces in vitro only trace amounts of oil with a strikingly different composition compared with the oils from in vivo Vetiver plants stimulated the hypothesis of an involvement of these bacteria in the oil metabolism. We used culture-based and culture-independent approaches to analyse the microbial community of the Vetiver root. Results demonstrate a broad phylogenetic spectrum of bacteria, including ,-, ,- and ,- Proteobacteria, high-G+C-content Gram-positive bacteria, and microbes belonging to the Fibrobacteres/Acidobacteria group. We isolated root-associated bacteria and showed that most of them are able to grow by using oil sesquiterpenes as a carbon source and to metabolize them releasing into the medium a large number of compounds typically found in commercial Vetiver oils. Several bacteria were also able to induce gene expression of a Vetiver sesquiterpene synthase. These results support the intriguing hypothesis that bacteria may have a role in essential oil biosynthesis opening the possibility to use them to manoeuvre the Vetiver oil molecular structure. [source] Characterizing the regulation of the Pu promoter in Acinetobacter baylyi ADP1ENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Wei E. Huang Summary Effective gene trapping and screening requires sensory and regulatory compatibility of both host and exogenous systems. The naturally competent bacterium Acinetobacter baylyi ADP1 is able to efficiently take up and integrate exogenous DNA into the chromosome, making it an attractive host system for a wide range of metagenomic applications. To test the ability of A. baylyi ADP1 to express the XylR-regulated Pu promoter from Pseudomonas putida mt-2, we have constructed and examined an A. baylyi ADP1 strain, ADPWH- Pu-lux-xylR. The Pu promoter in ADPWH- Pu-lux-xylR was specifically induced by toluene, m -, p - and o- xylene. The substrate-induced Pu promoter was highly dependent on the growth medium: it was repressed in rich media until stationary phase, but was immediately induced in minimal medium with glucose as the sole carbon source (MMG). However, the Pu promoter was repressed in MMG when it was supplemented with 5 g l,1 yeast extract. Further investigation showed that the Pu promoter in MMG was repressed by 0.5 g l,1 aspartic acid or asparagine, but not repressed by glutamine. Changing the carbon/nitrogen ratios by addition of ammonia did not significantly affect the Pu promoter activity but addition of nitrate did. These results show that A. baylyi ADP1 reproduced characteristics of the XylR-regulated Pu promoter observed in its original host. It demonstrates that A. baylyi could provide an excellent genetic host for a wide range of functional metagenomic applications. [source] Raman-FISH: combining stable-isotope Raman spectroscopy and fluorescence in situ hybridization for the single cell analysis of identity and functionENVIRONMENTAL MICROBIOLOGY, Issue 8 2007Wei E. Huang Summary We have coupled fluorescence in situ hybridization (FISH) with Raman microscopy for simultaneous cultivation-independent identification and determination of 13C incorporation into microbial cells. Highly resolved Raman confocal spectra were generated for individual cells which were grown in minimal medium where the ratio of 13C to 12C content of the sole carbon source was incrementally varied. Cells which were 13C-labelled through anabolic incorporation of the isotope exhibited key red-shifted spectral peaks, the calculated ,red shift ratio' (RSR) being highly correlated with the 13C-content of the cells. Subsequently, Raman instrumentation and FISH protocols were optimized to allow combined epifluorescence and Raman imaging of Fluos, Cy3 and Cy5-labelled microbial populations at the single cell level. Cellular 13C-content determinations exhibited good congruence between fresh cells and FISH hybridized cells indicating that spectral peaks, including phenylalanine resonance, which were used to determine 13C-labelling, were preserved during fixation and hybridization. In order to demonstrate the suitability of this technology for structure,function analyses in complex microbial communities, Raman-FISH was deployed to show the importance of Pseudomonas populations during naphthalene degradation in groundwater microcosms. Raman-FISH extends and complements current technologies such as FISH-microautoradiography and stable isotope probing in that it can be applied at the resolution of single cells in complex communities, is quantitative if suitable calibrations are performed, can be used with stable isotopes and has analysis times of typically 1 min per cell. [source] Methane-derived carbon flows through methane-oxidizing bacteria to higher trophic levels in aquatic systemsENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Peter Deines Summary Recent investigations have shown that biogenic methane can be a carbon source for macro invertebrates in freshwater food webs. Stable carbon isotopic signatures, used to infer an organism's food source, indicated that methane can play a major role in the nutrition of chironomid larvae. However, the pathway of methane-derived carbon into invertebrate biomass is still not confirmed. It has been proposed that chironomid larvae ingest methane-oxidizing bacteria (MOB), but this has not been experimentally demonstrated to date. Using 13C-labelled methane we could show for the first time that chironomid larvae assimilate methane-derived carbon through MOB. Chironomid larval biomass was significantly 13C-enriched after dwelling for 10 days in lake sediment enriched with labelled methane. Moreover, phospholipid fatty acids diagnostic for MOB were detected in larval tissue and were significantly 13C-enriched, which encompasses the 13C-uptake predicted for a methane-based nutrition. Additionally, chironomid larvae fed on sediment and water-column derived MOB biomass. [source] Detection of glycolate oxidase gene glcD diversity among cultured and environmental marine bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 10 2006W. W. Y. Lau Summary Of eight laboratory cultures of marine ,- and ,- Proteobacteria tested, growth on glycolate as a sole carbon source was detected for only three species: Pseudomonas stutzeri, Oceanimonas doudoroffii and Roseobacter sp. isolate Y3F. Degenerate polymerase chain reaction (PCR) primers were designed to amplify glcD, which encodes the D-subunit of the enzyme glycolate oxidase; glcD could be amplified only from those cultures that grew on glycolate. The PCR primers were used to explore glcD diversity in four field samples collected from different ocean environments: an Atlantic Gulf Stream Ring, sampled above and below the thermocline and two Pacific coastal sites, Parks Bay and San Juan Channel, WA. Environmental glcD sequences belonged to six major bacterial phylogenetic groups, with most sequences forming novel clades with no close relatives. Different patterns of glcD diversity were observed within and between the two nutrient regimes. Comparison of glcD and 16S rDNA diversity and analyses of available bacterial genomes and a metgenomic library from the Sargasso Sea show that glycolate-utilizing potential exists in only a subset of bacteria. Glycolate is produced in marine environments mainly by phytoplankton. Examination of glcD diversity will aid in understanding the influence of phytoplankton on bacterial community structure. [source] Anaerobic arsenite oxidation by novel denitrifying isolatesENVIRONMENTAL MICROBIOLOGY, Issue 5 2006E. Danielle Rhine Summary Autotrophic microorganisms have been isolated that are able to derive energy from the oxidation of arsenite [As(III)] to arsenate [As(V)] under aerobic conditions. Based on chemical energetics, microbial oxidation of As(III) can occur in the absence of oxygen, and may be relevant in some environments. Enrichment cultures were established from an arsenic contaminated industrial soil amended with As(III) as the electron donor, inorganic C as the carbon source and nitrate as the electron acceptor. In the active enrichment cultures, oxidation of As(III) was stoichiometrically coupled to the reduction of NO3,. Two autotrophic As(III)-oxidizing strains were isolated that completely oxidized 5 mM As(III) within 7 days under denitrifying conditions. Based on 16S rRNA gene sequencing results, strain DAO1 was 99% related to Azoarcus and strain DAO10 was most closely related to a Sinorhizobium. The nitrous oxide reductase (nosZ) and the RuBisCO Type II (cbbM) genes were successfully amplified from both isolates underscoring their ability to denitrify and fix CO2 while coupled to As(III) oxidation. Although limited work has been done to examine the diversity of anaerobic autotrophic oxidizers of As(III), this process may be an important component in the biological cycling of arsenic within the environment. [source] Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 10 2002Husen Zhang Summary Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the , subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water. [source] Bioavailability of solid and non-aqueous phase liquid (NAPL)-dissolved phenanthrene to the biosurfactant-producing bacterium Pseudomonas aeruginosa 19SJENVIRONMENTAL MICROBIOLOGY, Issue 9 2001Marta García-Junco The biodegradation of phenanthrene by the biosurfactant-producing strain Pseudomonas aeruginosa 19SJ was investigated in experiments with the compound present either as crystals or dissolved in non-aqueous phase liquids (NAPLs). Growth on solid phenanthrene exhibited an initial phase not limited by dissolution rate and a subsequent, carbon-limited phase caused by exhaustion of the carbon source. Rhamnolipid biosurfactants were produced from solid phenanthrene and appeared in solution and particulate material (cells and phenanthrene crystals). During the carbon-limited phase, the concentration of rhamnolipids detected in culture exceeded the critical micelle concentration (CMC) determined with purified rhamnolipids. The biosurfactants caused a significant increase in dissolution rate and pseudosolubility of phenanthrene, but only at concentrations above the CMC. Externally added rhamnolipids at a concentration higher than the CMC increased the biodegradation rate of solid phenanthrene. Mineralization curves of low concentrations of phenanthrene initially dissolved in two NAPLs [2,2,4,4,6,8,8-heptamethylnonane and di(2-ethylhexyl)phthalate] were S-shaped, although no growth was observed in the population of suspended bacteria. Biosurfactants were not detected in solution under these conditions. The observed mineralization was attributed not only to suspended bacteria, but also to bacterial populations growing at the NAPL,water interface, mineralizing the compound at higher rates than predicted by abiotic partitioning. We suggest that rhamnolipid production and attachment increased the bioavailability of phenanthrene, so promoting biodegradation activity. [source] Selection and identification of bacterial strains with methyl- tert -butyl ether, ethyl- tert -butyl ether, and tert -amyl methyl ether degrading capacitiesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2008Jessica Purswani Abstract Nine bacterial strains isolated from two hydrocarbon-contaminated soils were selected because of their capacity for growth in culture media amended with 200 mg/L of one of the following gasoline oxygenates: Methyl- tert -butyl ether (MTBE), ethyl- tert -butyl ether (ETBE), and tert -amyl methyl ether (TAME). These strains were identified by amplification of their 16S rRNA gene, using fD1 and rD1 primers, and were tested for their capacity to grow and biotransform these oxygenates in both mineral and cometabolic media. The isolates were classified as Bacillus simplex, Bacillus drentensis, Arthrobacter sp., Acinetobacter calcoaceticus, Acinetobacter sp., Gordonia amicalis (two strains), Nocardioides sp., and Rhodococcus ruber. Arthrobacter sp. (strain MG) and A. calcoaceticus (strain M10) consumed 100 (cometabolic medium) and 82 mg/L (mineral medium) of oxygenate TAME in 21 d, respectively, under aerobic conditions. Rhodococcus ruber (strain E10) was observed to use MTBE and ETBE as the sole carbon and energy source, whereas G. amicalis (strain T3) used TAME as the sole carbon and energy source for growth. All the bacterial strains transformed oxygenates better in the presence of an alternative carbon source (ethanol) with the exception of A. calcoaceticus (strain M10). The capacity of the selected strains to remove MTBE, ETBE, and TAME looks promising for application in bioremediation technologies. [source] Light-induced gene expression of fructose 1,6-bisphosphate aldolase during heterotrophic growth in a cyanobacterium, Synechocystis sp.FEBS JOURNAL, Issue 1 2009PCC 680 Synechocystis sp. PCC 6803 exhibits light-activated heterotrophic growth (LAHG) under dark conditions with glucose as a carbon source. The light activation is remarkable at a late period of photoautotrophic preculture, such as the late-linear and stationary growth phases. To understand the physiological effects of light irradiation and glucose under LAHG conditions, their effects on the expression of soluble proteins were analyzed by means of 2D-PAGE. Various soluble proteins, which were minimal under photoautotrophic preculture conditions, were observed clearly under LAHG conditions, suggesting that proteins were synthesized actively under these conditions. Fructose 1,6-bisphosphate aldolase, one of the glycolytic enzymes, was found to be induced under LAHG conditions on 2D-PAGE. The activity of fructose 1,6-bisphosphate aldolase, which had decreased during photoautotrophic preculture, also increased under LAHG conditions, similar to the mRNA level of the encoding gene, fbaA. In addition, we found that a deletion mutant of sll1330, a putative gene containing a helix-turn-helix DNA-binding motif, could not grow under LAHG conditions, whereas it could grow photoautotrophically. The increases in the protein level of FbaA and fbaA gene expression observed in wild-type cells under LAHG conditions were greatly inhibited in the deletion mutant. These results suggest that the regulation of fbaA gene expression by way of sll1330 is one of the important processes in Synechocystis sp. PCC 6803 under light pulse LAHG conditions. [source] Intracellular pH homeostasis in the filamentous fungus Aspergillus nigerFEBS JOURNAL, Issue 14 2002Stephan J. A. Hesse Intracellular pH homeostasis in the filamentous fungus Aspergillus niger was measured in real time by 31P NMR during perfusion in the NMR tube of fungal biomass immobilized in Ca2+ -alginate beads. The fungus maintained constant cytoplasmic pH (pHcyt) and vacuolar pH (pHvac) values of 7.6 and 6.2, respectively, when the extracellular pH (pHex) was varied between 1.5 and 7.0 in the presence of citrate. Intracellular metabolism did not collapse until a ,pH over the cytoplasmic membrane of 6.6,6.7 was reached (pHex 0.7,0.8). Maintenance of these large pH differences was possible without increased respiration compared to pHex 5.8. Perfusion in the presence of various hexoses and pentoses (pHex 5.8) revealed that the magnitude of ,pH values over the cytoplasmic and vacuolar membrane could be linked to the carbon catabolite repressing properties of the carbon source. Also, larger ,pH values coincided with a higher degree of respiration and increased accumulation of polyphosphate. Addition of protonophore (carbonyl cyanide m -chlorophenylhydrazone, CCCP) to the perfusion buffer led to decreased ATP levels, increased respiration and a partial (1 µm CCCP), transient (2 µm CCCP) or permanent (10 µm CCCP) collapse of the vacuolar membrane ,pH. Nonlethal levels of the metabolic inhibitor azide (N3,, 0.1 mm) caused a transient decrease in pHcyt that was closely paralleled by a transient vacuolar acidification. Vacuolar H+ influx in response to cytoplasmic acidification, also observed during extreme medium acidification, indicates a role in pH homeostasis for this organelle. Finally, 31P NMR spectra of citric acid producing A. niger mycelium showed that despite a combination of low pHex (1.8) and a high acid-secreting capacity, pHcyt and pHvac values were still well maintained (pH 7.5 and 6.4, respectively). [source] Identification and characterization of the genes for N -acetylglucosamine kinase and N -acetylglucosamine-phosphate deacetylase in the pathogenic fungus Candida albicansFEBS JOURNAL, Issue 8 2001Toshiko Yamada-Okabe Like bacteria and many fungi, the pathogenic fungus Candida albicans can utilize GlcNAc as a carbon source for growth. A cluster of six genes was identified in the C. albicans genome. One of the genes in the cluster was CaNAG1, which is responsible for GlcN6P deaminase and is therefore essential for GlcNAc-dependent growth. The other five genes were designated CaNAG2, CaNAG3, CaNAG4, CaNAG5 and CaNAG6. The mRNA levels of CaNAG1, CaNAG2 and CaNAG5 were significantly induced by GlcNAc, whereas those of CaNAG3, CaNAG4 and CaNAG6 were not. Neither CaNAG2 nor CaNAG5 was essential for growth, but disruption of CaNAG2 or CaNAG5 greatly retarded the growth of cells using GlcNAc as the sole carbon source. Although no homolog of CaNAG2 or CaNAG5 was found in the Saccharomyces cerevisiae genome, CaNag2p displayed sequence similarities to Escherichia coli nagA, and CaNag5p is homologous to a wide variety of hexose kinases. When expressed as a fusion protein with glutathione S -transferase (GST), CaNag5p produced GlcNAc-P from GlcNAc in the presence of ATP, whereas GST alone did not. Furthermore, the recombinant GST,CaNag2p fusion protein converted GlcNAcP, which was produced by CaNag5p, into GlcNP. These results clearly demonstrate that CaNAG2 and CaNAG5 encode GlcNAcP deacetylase and GlcNAc kinase, respectively. CaNag5p recognized glucose and mannose as substrates, whereas the recently identified human GlcNAc kinase was specific to GlcNAc. Deletion of CaNAG2 or CaNAG5 markedly, and that of CaNAG1 moderately, attenuated the virulence of C. albicans in a mouse systemic infection model. Thus, it appears that GlcNAc metabolism of C. albicans is closely associated with its virulence. [source] Growth kinetics of microorganisms isolated from Alaskan soil and permafrost in solid media frozen down to ,35°CFEMS MICROBIOLOGY ECOLOGY, Issue 2 2007Nicolai S. Panikov Abstract We developed a procedure to culture microorganisms below freezing point on solid media (cellulose powder or plastic film) with ethanol as the sole carbon source without using artificial antifreezes. Enrichment from soil and permafrost obtained on such frozen solid media contained mainly fungi, and further purification resulted in isolation of basidiomycetous yeasts of the genera Mrakia and Leucosporidium as well as ascomycetous fungi of the genus Geomyces. Contrary to solid frozen media, the enrichment of liquid nutrient solutions at 0°C or supercooled solutions stabilized by glycerol at ,1 to ,5°C led to the isolation of bacteria representing the genera Polaromonas, Pseudomonas and Arthrobacter. The growth of fungi on ethanol,microcrystalline cellulose media at ,8°C was exponential with generation times of 4.6,34 days, while bacteria displayed a linear or progressively declining curvilinear dynamic. At ,17 to ,0°C the growth of isolates and entire soil community on 14C-ethanol was continuous and characterized by yields of 0.27,0.52 g cell C (g of C-substrate),1, similar to growth above the freezing point. The ,state of maintenance,' implying measurable catabolic activity of non-growing cells, was not confirmed. Below ,18 to ,35°C, the isolated organisms were able to grow only transiently for 3 weeks after cooling with measurable respiratory and biosynthetic (14CO2 uptake) activity. Then metabolic activity declined to zero, and microorganisms entered a state of reversible dormancy. [source] Contribution of ethylamine degrading bacteria to atrazine degradation in soilsFEMS MICROBIOLOGY ECOLOGY, Issue 2 2006Daniel Smith Abstract Bacterial communities that cooperatively degrade atrazine commonly consist of diverse species in which the genes for atrazine dechlorination and dealkylation are variously distributed among different species. Normally, the first step in degradation of atrazine involves dechlorination mediated by atzA, followed by stepwise dealkylation to yield either N -ethylammelide or N -isopropylammelide. As the liberated alkylamine moieties are constituents of many organic molecules other than atrazine, it is possible that a large number of alkylamine-degrading bacteria other than those previously described might contribute to this key step in atrazine degradation. To examine this hypothesis, we isolated 82 bacterial strains from soil by plating soil water extracts on agar media with ethylamine as a sole carbon source. Among the relatively large number of isolates, only 3 were able to degrade N -ethylammelide, and in each case were shown to carry the atzB gene and atzC genes. The isolates, identified as Rhizobium leguminosarum, Flavobacterium sp., and Arthrobacter sp., were all readily substituted into an atrazine-degrading consortium to carry out N -ethylammelide degradation. The distribution of these genes among many different species in the soil microbial population suggests that these genes are highly mobile and over time may lead to generation of various atrazine-degrading consortia. [source] Molecular monitoring of microbial diversity in expanded granular sludge bed (EGSB) reactors treating oleic acidFEMS MICROBIOLOGY ECOLOGY, Issue 2 2002Maria Alcina Pereira Abstract A molecular approach was used to evaluate the microbial diversity of bacteria and archaea in two expanded granular sludge bed (EGSB) reactors fed with increasing oleic acid loading rates up to 8 kg of chemical oxygen demand (COD) m,3 day,1 as the sole carbon source. One of the reactors was inoculated with granular sludge (RI) and the other with suspended sludge (RII). During operation, the sludge in both reactors was segregated in two layers: a bottom settled one and a top floating one. The composition of the bacterial community, based on 16S rDNA sequence diversity, was affected most during the oleate loading process in the two reactors. The archaeal consortium remained rather stable over operation in RI, whereas in RII the relative abundance of Methanosaeta -like organisms became gradually weaker, starting in the bottom layer. In the range of oleate loads evaluated, 6 kg of COD m,3 day,1 was found as the maximum value that could be applied to the system. A further increase to 8 kg of oleate-COD m,3 day,1 induced a maximal shift on the microbial structure of the sludges. At this time point, methanogenic acetoclastic activity was not detected and only very low methanogenic activity on H2/CO2 was exhibited by the sludges. [source] Bacillus subtilis contains a cyclodextrin-binding protein which is part of a putative ABC-transporterFEMS MICROBIOLOGY LETTERS, Issue 1 2001Annette Kamionka Abstract Bacillus subtilis is able to grow on ,-, ,- and ,-cyclodextrins as a carbon source via a yet unknown metabolizing system. Sequence analysis of the B. subtilis genome reveals that the putative yvfK-yvfO operon seems to be involved in cyclodextrin utilization, containing the open reading frame yvfK, now termed cycB. The amino acid sequence derived from the DNA sequence bears high similarities to solute-binding proteins from B. subtilis, as well as to cymE from Klebsiella oxytoca and malE from Escherichia coli, both encoding solute-binding proteins able to interact with cyclodextrins. A [His]6 -tagged variant of CycB from B. subtilis was constructed, overproduced in E. coli and purified. The modified protein has been used to study its substrate specificity by surface plasmon resonance and fluorescence spectroscopy. From these data, CycB can be classified as a cyclodextrin-binding protein which interacts with all three natural cyclodextrins: ,, , and ,, thereby showing the highest affinity to ,-cyclodextrin. [source] Transcriptional regulation of nonfermentable carbon utilization in budding yeastFEMS YEAST RESEARCH, Issue 1 2010Bernard Turcotte Abstract Saccharomyces cerevisiae preferentially uses glucose as a carbon source, but following its depletion, it can utilize a wide variety of other carbons including nonfermentable compounds such as ethanol. A shift to a nonfermentable carbon source results in massive reprogramming of gene expression including genes involved in gluconeogenesis, the glyoxylate cycle, and the tricarboxylic acid cycle. This review is aimed at describing the recent progress made toward understanding the mechanism of transcriptional regulation of genes responsible for utilization of nonfermentable carbon sources. A central player for the use of nonfermentable carbons is the Snf1 kinase, which becomes activated under low glucose levels. Snf1 phosphorylates various targets including the transcriptional repressor Mig1, resulting in its inactivation allowing derepression of gene expression. For example, the expression of CAT8, encoding a member of the zinc cluster family of transcriptional regulators, is then no longer repressed by Mig1. Cat8 becomes activated through phosphorylation by Snf1, allowing upregulation of the zinc cluster gene SIP4. These regulators control the expression of various genes including those involved in gluconeogenesis. Recent data show that another zinc cluster protein, Rds2, plays a key role in regulating genes involved in gluconeogenesis and the glyoxylate pathway. Finally, the role of additional regulators such as Adr1, Ert1, Oaf1, and Pip2 is also discussed. [source] SOA genes encode proteins controlling lipase expression in response to triacylglycerol utilization in the yeast Yarrowia lipolyticaFEMS YEAST RESEARCH, Issue 1 2010Thomas Desfougères Abstract The oleaginous yeast Yarrowia lipolytica efficiently metabolizes hydrophobic substrates such as alkanes, fatty acids or triacylglycerol. This yeast has been identified in oil-polluted water and in lipid-rich food. The enzymes involved in lipid breakdown, for use as a carbon source, are known, but the molecular mechanisms controlling the expression of the genes encoding these enzymes are still poorly understood. The study of mRNAs obtained from cells grown on oleic acid identified a new group of genes called SOA genes (specific for oleic acid). SOA1 and SOA2 are two small genes coding for proteins with no known homologs. Single- and double-disrupted strains were constructed. Wild-type and mutant strains were grown on dextrose, oleic acid and triacylglycerols. The double mutant presents a clear phenotype consisting of a growth defect on tributyrin and triolein, but not on dextrose or oleic acid media. Lipase activity was 50-fold lower in this mutant than in the wild-type strain. The impact of SOA deletion on the expression of the main extracellular lipase gene (LIP2) was monitored using a LIP2 -,-galactosidase promoter fusion protein. These data suggest that Soa proteins are components of a molecular mechanism controlling lipase gene expression in response to extracellular triacylglycerol. [source] Lithium-mediated suppression of morphogenesis and growth in Candida albicansFEMS YEAST RESEARCH, Issue 4 2008Layla F. Martins Abstract Hyphal development in Candida albicans contributes to virulence, and inhibition of filamentation is a target for the development of antifungal agents. Lithium is known to impair Saccharomyces cerevisiae growth in galactose-containing media by inhibition of phosphoglucomutase, which is essential for galactose metabolism. Lithium-mediated phosphoglucomutase inhibition is reverted by Mg2+. In this study we have assessed the effect of lithium upon C. albicans and found that growth is inhibited preferentially in galactose-containing media. No accumulation of glucose-1-phosphate or galactose-1-phosphate was detected when yeasts were grown in the presence of galactose and 15 mM LiCl, though we observed that in vitro lithium-mediated phosphoglucomutase inhibition takes place with an IC50 of 2 mM. Furthermore, growth inhibition by lithium was not reverted by Mg2+. These results show that lithium-mediated inhibition of growth in a galactose-containing medium is not due to inhibition of galactose conversion to glucose-6-phosphate but is probably due to inhibition of a signaling pathway. Deletion of the Ser-Thr protein phosphatase SIT4 and treatment with rapamycin have been shown to inhibit filamentous differentiation. We observed that C. albicans filamentation was inhibited by lithium in solid medium containing either galactose as the sole carbon source or 10% fetal bovine serum. These results suggest that suppression of hyphal outgrowth by lithium could be related to inhibition of the target of rapamycin (TOR) pathway. [source] The transcarboxylase domain of pyruvate carboxylase is essential for assembly of the peroxisomal flavoenzyme alcohol oxidaseFEMS YEAST RESEARCH, Issue 7 2007Paulina Z. Ozimek Abstract Pyruvate carboxylase (Pyc1p) has multiple functions in methylotrophic yeast species. Besides its function as an enzyme, Pyc1p is required for assembly of peroxisomal alcohol oxidase (AO). Hence, Pyc1p-deficient cells share aspartate auxotrophy (Asp,) with a defect in growth on methanol as sole carbon source (Mut,). To identify regions in Hansenula polymorpha Pyc1p that are required for the function of HpPyc1p in AO assembly, a series of random mutations was generated in the HpPYC1 gene by transposon mutagenesis. Upon introduction of 18 mutant genes into the H. polymorpha PYC1 deletion strain (pyc1), four different phenotypes were obtained, namely Asp, Mut,, Asp, Mut+, Asp+ Mut,, and Asp+ Mut+. One mutant showed an Asp+ Mut, phenotype. This mutant produced HpPyc1p containing a pentapeptide insertion in the region that links the conserved N-terminal biotin carboxylation domain (BC) with the central transcarboxylation (TC) domain. Three mutants that were Asp, Mut, contained insertions in the TC domain, suggesting that this domain is important for both functions of Pyc1p. Analysis of a series of constructed C-terminal and N-terminal truncated versions of HpPyc1p showed that the TC domain of Pyc1p, including the region linking this domain to the BC domain, is essential for AO assembly. [source] Hog1p mitogen-activated protein kinase determines acetic acid resistance in Saccharomyces cerevisiaeFEMS YEAST RESEARCH, Issue 8 2006Mehdi Mollapour Abstract When glucose-repressed, Saccharomyces cerevisiae cannot use acetic acid as a carbon source and is inhibited in growth by high levels of this compound, especially at low pH. Cultures exposed to a 100 mM acetate stress activate both the Hog1p and Slt2p stress-activated MAP kinases. Nevertheless, only active Hog1p, not Slt2p, is needed for the acquisition of acetate resistance. Hog1p undergoes more rapid activation by acetate in pH 4.5, than in pH 6.8 cultures, an indication that the acid may have to enter the cells in order to generate the Hog1p activatory signal. Acetate activation of Hog1p is absent in the ssk1, and pbs2, mutants, but is present in sho1, and ste11,, showing that it involves the Sln1p branch of the high-osmolarity glycerol (HOG) pathway signaling to Pbs2p. In low-pH (pH 4.5) cultures, the acetate-activated Hog1p, although conferring acetate resistance, does not generate the GPD1 gene or intracellular glycerol inductions that are hallmarks of activation of the HOG pathway by hyperosmotic stress. [source] Rhodotorula cycloclastica sp. nov., Rhodotorula retinophila sp. nov., and Rhodotorula terpenoidalis sp. nov., three limonene-utilizing yeasts isolated from soilFEMS YEAST RESEARCH, Issue 8 2004Vu Nguyen Thanh Abstract During a search for yeasts that hydroxylate monoterpenes, four yeast strains were isolated from soil and plant residue in monoterpene-rich environments using enrichment techniques with cyclohexanedioic acid or cyclohexanedimethanol as sole carbon source. These strains were able to utilize (+)-limonene supplied as a vapor as only carbon source. The yeasts have a CoQ-10 system. Morphology and physiological properties of the strains did not fit any known yeast species. Recent analysis of the 26S D1/D2 and ITS-5.8S rDNA sequences of basidiomycetous yeasts showed that these strains represented three hitherto unknown species of Rhodotorula and fell in a cluster consisting of Rhodotorula philyla and the mycoparasitic fungus Colacogloea peniophorae. Descriptions of three new species Rhodotorula cycloclastica (type strain TVN 309=UOFS Y 2046=CBS 8448), Rhodotorula retinophila (type strain TVN 295=UOFS Y 2043=CBS 8446), Rhodotorula terpenoidalis (type strain TVN 310=UOFS Y 2042=CBS 8445) are proposed to accommodate these isolates. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||