Variations In Carbon Sources Research Articles

A close-up view of the Permian–Triassic boundary based on expanded organic carbon isotope records from Norway (Trøndelag and Finnmark Platform)

High-resolution carbon isotope records of organic carbon (δ 13C org) across the Permian–Triassic boundary (PTB) from the expanded sections of the Trøndelag and Finnmark platforms in Norway demonstrate that the negative carbon isotope excursion around the PTB begins with a stepwise 8‰ negative decline to a first minimum. After a subsequent positive excursion, a second minimum follows in the basal Griesbachian. Particulate organic matter (POM) is dominated by terrestrial particles with changing marine contributions. Intervals with minor C-isotope fluctuations coincide with homogeneous terrestrial POM assemblages, whereas intervals with pronounced C-isotope fluctuations correspond to heterogeneous marine–terrestrial POM assemblages, suggesting that the C-isotope curve represents a global signal with superimposed local variations of carbon sources. The δ 13C org of the contributing organic carbon ranges from − 32‰ (marine organic carbon) to − 22‰ (terrestrial organic carbon). Comparison of the new record, divided into 10 chemostratigraphic intervals with other, globally distributed sections suggests the presence of gaps in several classical PTB sections. Detailed chemostratigraphic correlation reveals that the extinction of marine organisms occurred during the stepwise negative shift and the end-Permian floral turnover occurred prior to the first C-isotope minimum. The correlation also shows that the marker of the recently defined Global Stratotype Section and Point PTB occurs within a broad interval ranging from most negative δ 13C values up to the subsequent isotopic increase.

EVIDENCE SUPPORTING THE IMPORTANCE OF TERRESTRIAL CARBON IN A LARGE-RIVER FOOD WEB

Algal carbon has been increasingly recognized as the primary carbon source supporting large-river food webs; however, many of the studies that support this contention have focused on lotic main channels during low-flow periods. The flow variability and habitat-heterogeneity characteristic of these systems has the potential to significantly influence food web structure and must be integrated into models of large-river webs. We used stable-isotope analysis and IsoSource software to model terrestrial and algal sources of organic carbon supporting consumer taxa in the main channel and oxbow lakes of the Brazos River, Texas, USA, during a period of frequent hydrologic connectivity between these habitat types. Standardized sampling was conducted monthly to collect production sources and consumer species used in isotopic analysis. Predictability of hydrologic connections between habitat types was based on the previous 30 years of flow data. IsoSource mixing models identified terrestrial C3 macrophytes (riparian origin) as the primary carbon source supporting virtually all consumers in the main channel and most consumers in oxbow lakes. Small-bodied consumers (<100 mm) in oxbow lakes assimilated large fractions of algal carbon whereas this pattern was not apparent in the main channel. Estimates of detritivore trophic positions based on delta15N values indicated that terrestrial material was likely assimilated via invertebrates rather than directly from detritus. High flows in the river channel influenced algal standing stock, and differences in the importance of terrestrial and algal production sources among consumers in channel vs. oxbow habitats were associated with patterns of flooding. The importance of terrestrial material contradicts the findings of recent studies of large-river food webs that have emphasized the importance of algal carbon and indicates that there can be significant spatial, temporal, and taxonomic variation in carbon sources supporting consumers in large rivers.

Effect of carbon source on the antimicrobial activity of Corynebacterium kutscheri and Corynebacterium xerosis

In an attempt to screen out new potent antimicrobial substances producing bacteria,Corynebacterium kutscheri NB-1 and Corynebacterium xerosis NB-2 were isolated and were found antagonistic to bacteria and fungi. Antimicrobial substances production of the bacterial strains was greatly influenced by variation of carbon sources. Galactose and glucose strongly enhanced the antimicrobial activity ofCorynebacterium kutscheri and Corynebacterium xerosis, respectively. But their antimicrobial activity had been repressed by ribose and lactose, respectively. Key words: Antimicrobial substances, Corynebacterium kutscheri, Corynebacterium xerosis, fermentation.

Simultaneous Qualitative and Quantitative Analysis of theEscherichia coli Proteome

We describe a novel LCMS approach to the relative quantitation and simultaneous identification of proteins within the complex milieu of unfractionated Escherichia coli. This label-free, LCMS acquisition method observes all detectable, eluting peptides and their corresponding fragment ions. Postacquisition data analysis methods extract both the chromatographic and the mass spectrometric information on the tryptic peptides to provide time-resolved, accurate mass measurements, which are subsequently used for quantitation and identification of constituent proteins. The response of E. coli to carbon source variation is well understood, and it is thus commonly used as a model biological system when validating an analytical method. Using this LCMS approach, we characterized proteins isolated from E. coli grown in glucose, lactose, and acetate. The change in relative abundance of the corresponding proteins was measured from peptides common to both conditions. Protein identities were also determined for those peptides that were unique to each condition, and these identities were found to be consistent with the underlying biochemical restrictions imposed by the growth conditions. The relative change in abundance of the characterized proteins ranged from 0.1- to 90-fold among the three binary comparisons. The overall coverage of the characterized proteins ranged from 10 to 80%, consisting of one to 34 peptides per protein. The quantitative results obtained from our study were comparable to other existing proteomic and transcriptional profiling approaches. This study illustrates the robustness of this novel LCMS approach for the simultaneous quantitative and comprehensive qualitative analysis of proteins in complex mixtures.

Effect of Carbon Source on the Antimicrobial Activity of the Air Flora

In an attempt to screen for air flora producing new potent antimicrobial substances, Bacillus megaterium NB-3, Bacillus cereus NB-4, Bacillus cereus NB-5, Bacillus subtilis NB-6 and Bacillus circulans NB-7, were isolated and were found to be antagonistic to bacteria and/or fungi. Production of antimicrobial substances by the bacterial strains was greatly influenced by variation of carbon sources. Glycerol strongly enhanced the antimicrobial activity of strains NB-3 and NB-6, whereas glucose increased the antimicrobial activity of strains NB-4 and NB-5. The maximum antibiotic yield of NB-7 was achieved with fructose as a carbon source. Starch (Bacillus megaterium NB-3), maltose (Bacillus cereus NB-5), glycerol (Bacillus circulans NB-7), arabinose, ribose (Bacillus cereus NB-4) and arabinose, fructose, glucose, ribose and sucrose (Bacillus subtilis NB-6) repressed the production of antimicrobial substances by the respective bacterial strains.

Geochemical significance of the relative enrichment of pristane and the negative excursion of δ13CPr across the Permian-Triassic Boundary at Meishan, China

Changes in the distribution of isoprenoid hydrocarbons and in δ13Ckero or δ13CPr across the section from the Changxing Formation to the lower Yinkeng Formation at Meishan (the GSSP of PTB) are studied, in which a relative enrichment of pristane and a sharp shift in both δ13Ckero and δ13Cmole near the boundary are revealed. A possible mechanism for the abnormal accumulation of pristane near PTB is suggested: Lipids in some marine animals and their metabolites, rich in pristane, can be preserved and accumulate in some suitable depositing facies under certain special conditions, such as the catastrophic death of animals and/or developing of an anoxic water column, and thus the pristane enrichment occurs in the sediment. The occurrences of isoprenoid enrichment and high Pr/Ph ratios have been found in other typical marine anoxic sediments accompanied by mass extinction in various extent during the most important geological periods, such as Late Ordovician, end of Devonian, Early Jurassic and Late Cretaceous. These occurrences support to a certain extent the above mechanism that interprets the genesis of a high Pr/Ph ratio in some typical marine anoxic sediments. The synchronous sharp negative shifts in δ13Cmole, δ13Ckero and δ13Ccarb from Beds 24 to 26 of the Meishan profile indicate that a sudden and strong variation of carbon source in the atmosphere-ocean system occurred during the quick but equable evolution from the end-Permian to Early Triassic, and the coupling between the pristane enrichment and negative shift in δ13Ckero and δ13CPr may well indicate the importance of the release of methane hydrates and marine anoxia in the end-Permian mass extinction.

Stable Isotope Signatures of Native and Nonnative Fishes in Upper Colorado River Backwaters and Ponds

trophic relationships among native and nonnative fishes, and 2) can stable isotope signatures be used as a naturally-occurring marker to identify river fishes that have migrated from floodplain ponds? Nitrogen isotope ratios showed that at a particular location, either in ponds or backwaters, centrarchids were usually the top predators in each system. In one backwater, 815N and 8'3C signatures of the fish assemblage ranged about 4%o. The number of trophic levels represented was limited to about 2, and variation in carbon sources appeared to be great. The native flannelmouth sucker, Catostomus latipinnis, was most distinct with a relatively low 815N and high 813C signature. Stable isotope signatures appeared to have utility as a naturally occurring marker for tracking influx of nonnative fishes to the Colorado River from ponds. Whereas pond signatures were not consistently depleted or enriched relative to those from backwaters, mean stable isotope signatures were more different among ponds than among backwater sites. Further, within particular species, some ponds had carbon or nitrogen signatures that were quite different from those at backwater sites. Stable isotope analysis appears to have promise for studying trophic relationships and movement patterns of native and nonnative fishes in the upper Colorado River basin. RESUMEN-Is6topos estables de carb6n (13C) y nitr6geno (15N) que ocurren naturalmente fueron analizados para responder a preguntas acerca de interacciones tr6ficas entre pescados nativos

Effect of carbon source on enzymes and metabolites of arginine metabolism in Neurospora.

The levels of enzymes and metabolites of arginine metabolism were determined in exponential cultures of Neurospora crassa grown on various carbon sources. The carbon sources decreased in effectiveness (as determined by generation times) in the following order: sucrose, acetate, glycerol, and ethanol. The basal and induced levels of the catabolic enzymes, arginase (EC 3.5.3.1) and ornithine transaminase (EC 2.6.1.13), were lower in mycelia grown on poor carbon sources. Arginase was more sensitive to variations in carbon source than was ornithine transaminase. Induction of both enzymes was sensitive to nitrogen metabolite control, but this sensitivity was reduced in mycelia grown on glycerol or ethanol. The pools of arginine and ornithine were reduced in mycelia grown in unsupplemented medium containing poor carbon sources, but the biosynthetic enzyme ornithine transcarbamylase (EC 2.1.3.3) was not derepressed. The arginine pools were similar, regardless of carbon source, in mycelia grown in arginine-supplemented medium. The ornithine pool was reduced by growth on poor carbon sources. The rate of arginine degradation was proportional to the level of arginase in both sucrose- and glycerol-grown mycelia. The distribution of arginine between cytosol and vesicles was only slightly altered by growth on glycerol instead of sucrose. The slightly smaller cytosolic arginine concentration did not appear to be sufficient to account for the alterations in basal and induced enzyme levels. The results suggest a possible carbon metabolite effect on the expression or turnover of a variety of genes for enzymes of arginine metabolism in Neurospora.

Autolytic Defective Mutant of Streptococcus faecalis

Autolytic Defective Mutant of <i>Streptococcus faecalis</i>

Increased Antimetabolite Sensitivity with Variation of Carbon Source During Growth

Increased Antimetabolite Sensitivity with Variation of Carbon Source During Growth

Increased antimetabolite sensitivity with variation of carbon source during growth

In Serratia marcescens, analogs of leucine (norleucine), methionine (alpha-methylmethionine), histidine (3-amino-1,2,4-triazolealanine), tyrosine (p-aminophenylalanine), and tryptophan (7-methylindole) are conditional inhibitors of growth; inhibition occurs during the metabolism of some carbon sources but not with others. A further increase in sensitivity to growth inhibition by these analogs can be accomplished through the use of particular combinations of carbon sources present in the inoculum and in the subsequent analog-containing culture medium. Variable sensitivity to analog-mediated inhibition of growth observed during growth on glucose, glycerol, fructose, or citrate correlated inversely with the intracellular pool sizes of the amino acids cognate to the analogs used. The above-cited results, in conjunction with previous results obtained with Pseudomonas aeruginosa and Bacillus subtilis, involve diverse biochemical pathways and suggest that nutritional manipulation to alter the pattern of carbon flow in microorganisms is a generally useful means to accomplish increased sensitivity to growth inhibition by metabolite analogs.

On the regulation of adenosine 3′,5′-monophosphate synthesis in bacteria I. Effect of carbon source variation on cyclic AMP synthesis in escherichia coli B/r

1. 1. The effect of carbon source variation in bacterial growth media on their growth rate, inducible enzymes and cyclic AMP synthesis was examined: an inverse relationship between the culture's growth rate and its differential rate of inducible enzyme (tryptophanase and β-galactosidase), and cyclic AMP synthesis was found. 2. 2. The effect of the culture's growth phase on its sensitivity or resistance to glucose catabolite repression was determined in the wild type and a catabolite insensitive mutant (ABDROI): the wild type's sensitivity to glucose repression was not affected, whereas the insensitivity of the mutant was found to be limited to its early logarithmic phase of growth. At late log, or stationary phase, the mutant was found to be sensitive to glucose repression. 3. 3. Examination of the kinetics of glucose uptake by the mutant, using α-[ 14C] methyl-glucoside showed evidence for two transport systems each with a different affinity to glucose. A low affinity transport system (apparent K m of 3.4 · 10 −5 M) which appears mostly at the early logarithmic phase of growth. A high affinity transport system (apparent K m of 1.2 · 10 −5 M) which appears mostly at the late log and stationary phases of growth. 4. 4. The effect of the culture density variation on its sensitivity to glucose repression showed that sensitivity to glucose catabolic repression is primarily a reflection of the formation of an allosteric effector molecule between glucose and its specific transport molecule which in turn regulates the activity of the adenylate cyclase.