Initial Phase Of Incubation Research Articles

Evaluation of fate of organic matter in sediment through microcosm experiments

AbstractLaboratory microcosm experiments help to understand the degradation pattern of different sources derived from organic matter (OM) at the sediment–water interface and relate it to field processes. Microcosm experiments were carried out for 65 days to assess the degradation of organic materials such as diatoms, zooplankton, and mangrove leaves using source‐specific fatty acid (FA) biomarkers. The viable bacterial population in the microcosm sediment was low on day 1, but on day 3, it increased substantially by two to threefold in all the treatments. An increase in the bacterial population resulted in a decrease in the FAs specific to organic materials during the initial incubation phase (10 days), suggesting the degradation of organic materials derived from different sources. The FAs specific to diatoms showed faster degradation when compared to zooplankton and mangrove‐specific FAs. The degradation of FAs was influenced by the nature of the source material, unsaturation of FAs, and the sediment type. Sandy sediment facilitated higher degradation of diatom and zooplankton‐specific FAs, whereas mangrove‐specific FAs showed higher degradation in silty‐clay sediment. Thus, bacterial community composition coupled with the habitat characteristics, the OM composition, and the grain size of the sediment, influenced the degradation of FAs. The degradation of mangrove‐specific long‐chain FAs was ~1.11–2.5 times higher when spiked with plankton‐derived labile OM from mixed sources, which otherwise took a longer time for degradation pointing toward co‐metabolism (priming effect), which could play a significant role in the cycling of terrestrial plant‐derived OM in an estuarine ecosystem.

Glycerol amendment enhances biosulfidogenesis in acid mine drainage-affected areas: An incubation column experiment.

Microbial sulfate (SO4 2−) reduction in Acid Mine Drainage (AMD) environments can ameliorate the acidity and extreme metal concentrations by consumption of protons via the reduction of SO4 2− to hydrogen sulfide (H2S) and the concomitant precipitation of metals as metal sulfides. The activity of sulfate-reducing bacteria can be stimulated by the amendment of suitable organic carbon sources in these generally oligotrophic environments. Here, we used incubation columns (IC) as model systems to investigate the effect of glycerol amendment on the microbial community composition and its effect on the geochemistry of sediment and waters in AMD environments. The ICs were built with natural water and sediments from four distinct AMD-affected sites with different nutrient regimes: the oligotrophic Filón Centro and Guadiana acidic pit lakes, the Tintillo river (Huelva, Spain) and the eutrophic Brunita pit lake (Murcia, Spain). Physicochemical parameters were monitored during 18 months, and the microbial community composition was determined at the end of incubation through 16S rRNA gene amplicon sequencing. SEM-EDX analysis of sediments and suspended particulate matter was performed to investigate the microbially-induced mineral (neo)formation. Glycerol amendment strongly triggered biosulfidogenesis in all ICs, with pH increase and metal sulfide formation, but the effect was much more pronounced in the ICs from oligotrophic systems. Analysis of the microbial community composition at the end of the incubations showed that the SRB Desulfosporosinus was among the dominant taxa observed in all sulfidogenic columns, whereas the SRB Desulfurispora, Desulfovibrio and Acididesulfobacillus appeared to be more site-specific. Formation of Fe3+ and Al3+ (oxy)hydroxysulfates was observed during the initial phase of incubation together with increasing pH while formation of metal sulfides (predominantly, Zn, Fe and Cu sulfides) was observed after 1–5 months of incubation. Chemical analysis of the aqueous phase at the end of incubation showed almost complete removal of dissolved metals (Cu, Zn, Cd) in the amended ICs, while Fe and SO4 2− increased towards the water-sediment interface, likely as a result of the reductive dissolution of Fe(III) minerals enhanced by Fe-reducing bacteria. The combined geochemical and microbiological analyses further establish the link between biosulfidogenesis and natural attenuation through metal sulfide formation and proton consumption.

Interactive effects of nitrogen forms and temperature on soil organic carbon decomposition in the coastal wetland of the Yellow River Delta, China

Nitrogen (N) is a limiting nutrient in many terrestrial ecosystems. Many studies concentrated on the relationships between the amount of N deposition and soil organic carbon (SOC) dynamics. However, few studies are dedicated to differentiate the influence of inorganic and organic N deposition on SOC decomposition. In addition, the interactive effect of different forms of N and temperature on SOC decomposition is still unknown. A short-term incubation experiment was conducted to determine the interactive of N addition (nitrate, ammonium and organic N) and temperature on SOC decomposition in the coastal wetland of the Yellow River Delta, China. The results showed that increased temperature had a positive effect on SOC decomposition (P < 0.05). Both ammonium and organic N additions accelerated SOC decomposition at the initial phase of incubation (P < 0.05), while organic N produced larger and positive effects on SOC decomposition than ammonium at high level of N addition in the initial stage of incubation (P < 0.05). Furthermore, the interactive effect of N additions (i.e. two level of nitrate and organic N additions and a high level of ammonium addition) and temperature on SOC decomposition was mainly an additive effect due to the neutral effect of such N additions on the Q10 value of SOC decomposition. However, a low level of ammonium addition and temperature produced an antagonistic effect on SOC decomposition. This may be attributed to the decreased Q10 value of SOC decomposition at a low level of ammonium addition (P < 0.05). This indicates that short-term SOC decomposition under simultaneous influence of temperature and a low level of ammonium addition may be overestimated based on their single effects. Our results also highlight the importance of differentiating the effects of organic and inorganic N additions on SOC decomposition.

Redução na velocidade da nitrificação no solo após aplicação de cama de aviário com dicianodiamida

A rápida nitrificação do nitrogênio (N) amoniacal de fontes orgânicas e minerais no solo pode resultar em perdas de nitrato (NO3-) para o ambiente. Uma estratégia para a redução dessas perdas envolve o uso de inibidores de nitrificação. O objetivo do presente trabalho foi o de avaliar, em condições de laboratório, a eficiência da dicianodiamida (DCD), presente no produto Agrotain® Plus (AP), em inibir a nitrificação do N amoniacal de cama de aviário (CA) no solo. Foram avaliados cinco tratamentos, sendo um com CA incorporada ao solo, três com CA incorporada ao solo com AP, nas doses de 3,5, 7,0 e 14,0kg ha-1, além de um tratamento somente com solo. A nitrificação foi monitorada através da determinação periódica dos teores de NH4+ e NO3 no solo durante 69 dias. A maior taxa de nitrificação ocorreu no tratamento em que a CA foi incorporada ao solo sem AP. As doses de 3,5 e 7,0kg de AP ha-1 inibiram parcialmente a nitrificação do N amoniacal da CA na fase inicial da incubação, perdendo a eficiência em inibir esse processo no período entre 12 e 27 dias. O tratamento com a maior dose de AP (14kg ha-1) foi aquele em que a DCD exerceu maior efeito inibitório da nitrificação, preservando maior quantidade de NH4+ e retardando o aparecimento de NO3- no solo. Os resultados deste trabalho indicam que a DCD, contida no Agrotain® Plus, reduz a taxa de nitrificação do N amoniacal da CA no solo, o que poderá contribuir à redução das perdas de NO3- para o ambiente.

Wood modification with alkoxysilanes

Wood was treated with three different alkoxysilanes which are able to undergo a sol–gel process: tetraethoxysilane (TEOS), methyl triethoxysilane (MTES) and propyl triethoxysilane (PTEO). Two types of treatments were compared: impregnation of fibre saturated wood with monomeric silane solutions, and impregnation with pre-hydrolysed partly oligomeric silanes. Wood properties such as cell wall bulking, anti-swelling efficiency (ASE), moisture uptake and durability were more significantly improved in samples treated with monomeric silanes than in samples treated with oligomeric silanes. SEM-EDX mapping showed that this treatment resulted in a higher degree of silicon incorporation into the cell wall, although the weight percent gain (WPG) was lower compared to the treatment with pre-hydrolysed partly oligomeric silanes. The resistance against soil micro-organisms was enhanced in the initial phase of incubation especially in those samples treated with organo-functional-alkoxysilanes. In miniaturised block tests with the white-rot basidiomycete Trametes versicolor, an improved durability was observed within the test period. During an air conditioning step, a weight loss of the treated samples occurred which was accompanied by a reduction in bulking and ASE. The initial reduction of moisture uptake observed after treatment diminished almost completely. This effect was explained by an ageing of the gels in the wood cell wall which is a consequence of uncompleted hydrolysis and condensation of the silanes during the treatment.

Aplicação de técnicas eletroquímicas no estudo da dissolução oxidativa da covelita (CuS) por Thiobacillus ferrooxidans

Among the copper sulphides, chalcopyrite (CuFeS2), covellite (CuS) and chalcocite (Cu2S) are the most important source of minerals for copper mining industry. The acknowledge of behaviour of these sulphides related with bacterial leaching process are essential for optimization procedures. Despite of its importance, covellite has not deserved much interest of researchers regarding this matter. In this work it was studied the oxidation of covellite by the chemolithotrophic bacterium Thiobacillus ferrooxidans by using electrochemical techniques, such as open circuit potentials with the time and cyclic voltammetry. The experiments were carried out in acid medium (pH 1.8), containing or not Fe2+ as additional energy source, and in different periods of incubation; chemical controls were run in parallel. The results showed that a sulphur layer is formed spontaneously due the acid attack, covering the sulphide in the initial phase of incubation, blocking the sulphide oxidation. However, the bacterium was capable to oxidize this sulphur layer. In the presence of Fe2+ as supplemental energy source, the corrosion process was facilitated, because ocurred an indirect oxidation of covellite by Fe3+, which was produced by T. ferrooxidans oxidation of the Fe2+ added in the medium.

Improvement of mechanical and biological properties of freeze-dried denitrifying alginate beads by using starch as a filler and carbon source

Freeze-dried, alginate-based beads, used for the immobilization of a denitrifying bacterium (Pseudomonas sp.), were filled with different concentrations (10%, 20%, 30% and 40%, w/w) of granular starch. The beads were incubated under denitrifying conditions in laboratory-scale, flow-through columns and monitored for changes in their physical and denitrifying properties. Freeze-dried beads containing high concentrations of starch were found to have better mechanical and denitrifying properties than beads containing low concentrations of this filler. Nitrate removal by the beads was found to be correlated with their starch content. Nitrite accumulation, as a result of incomplete denitrification, increased with the decrease in starch content of the beads. Nitrite in the outlet of the columns was measured in all types of beads during the initial phase of incubation but was undetectable, with the exception of beads with the lowest starch content, at later stages of incubation.

Carbon and nitrogen mineralization and ammonia volatilization from fresh, aerobically and anaerobically treated pig manure during incubation with soil

We studied the decomposition of aerobically and anaerobically treated pig manure during a 2-month incubation with soil. The manure samples had not been in contact with straw or with animal urine. The aerobically decomposed manure proved to be the most stable (23% C mineralization), followed by fresh (75%) and anaerobically treated manure (105%, priming effect). The course of mineralization fitted combined first- and zeroorder kinetics. In the anaerobically treated manure, 76% of NH4+-N was immobilized during the initial incubation phase, followed by a slow linear mineralization. In the aerobically treated manure there was a slow linear mineralization after 5 days, and in the fresh material, a slightly faster linear mineralization after 6 days. Total mineralized N was very similar after 2 months (12%) in all treatments. Total NH3 losses were highest from the anaerobically treated manure (14%), reflecting a higher NH4+content with N mineralization following first-order kinetics. Relating NH3 losses to the initial NH4+content showed that all NH3 in the aerobically treated manure was volatilized, whereas only 28% was volatilized from the fresh and the anaerobically treated manure.

The alpha-saturation and terminal events in dolichol biosynthesis.

Incubations of 10,000 X g supernatant from rat liver with [3H]mevalonate were performed and the labeling of polyprenols was studied. It was demonstrated that factors like pH, substrate concentration, and presence of detergent not only greatly influence the total incorporation but also the relative distribution of radioactivity among the isoprenologues. The synthesis was shown to be extremely sensitive to Triton X-100. Substrate concentrations of 1 and 100 microM mostly gave polyprenols with 18 and 20 isoprenes, respectively. At a given substrate concentration, pH 6.5 resulted in shorter polyprenols than did pH 7.5. Ozonolytic fragmentation demonstrated that in the initial phase of incubation, polyprenols are elongated by 1 isoprene residue and saturated to give dolichols. No substantial dephosphorylation of polyprenyl phosphates to the free alcohol occurred. The production of dolichol in vitro was shown to utilize NADH for the saturation event. This seemed to occur concomitantly with the synthesis. alpha-Saturation of polyprenyl-P could not be achieved with the procedures employed. It is proposed that the synthesis of dolichol and dolichyl-P do not share the same terminal steps; saturation and terminal isoprene condensation occur in cooperation; and substrate concentration and pH influence the terminal enzyme(s) and the nature of the final product in the polyprenol biosynthesis.

Labeling of monoclonal antibodies with a 67Ga-phenolic aminocarboxylic acid chelate. Part I. Chemistry and labeling technique.

As a chelating agent for labeling antibodies (Abs) with metallic radionuclides, a propionic acid substituted ethylenediamine N,N'-di-[(o-hydroxyphenyl) acetic acid] (P-EDDHA), which tightly complexes 67Ga, was synthesized. The 67Ga-P-EDDHA chelate was coupled in aqueous solution to IgG at a molar ratio of 1:1 via carbodiimide. The average coupling yield was 15%. A specific activity of 4 mCi/mg IgG could be obtained with commercially supplied 67Ga. In vitro stability was evaluated in human serum at 37 degrees C and showed a half-life of about 120 h for the release of 67Ga from the labeled Ab during the initial phase of incubation. This in vitro halflife is similar to that measured for 111In-DTPA labeled Abs. Because of the high stability of the 67Ga-P-EDDHA chelate, the in vivo formation of radioactive labeled transferrin by transchelation, as described for 111In-DTPA labeled Abs, should, however, be reduced by this labeling technique.

Comparative study on the effects of a hypoglycemic 2-substituted-2-imidazoline derivative (DG-5128) and tolbutamide on insulin secretion from and insulin synthesis in the isolated rat pancreatic islets

2[2-(4,5-Dihydro-1H-imidazol-2-yl)-1-phenylethyl]pyridine dihydrochloride sesquihydrate (DG-5128) was found to stimulate the glucose-primed insulin secretion from the isolated rat pancreatic islets throughout the incubation period, unlike tolbutamide which stimulated it only in the initial phase of incubation. The effect of DG-5128 was more pronounced at a higher glucose concentration (5 mg/ml). In the islet perifusion study, DG-5128 was also found to stimulate the glucose-induced insulin secretion in both the first and the second phases of the reaction, in contrast to tolbutamide which stimulated only the first phase of insulin secretion from the perifused islets. DG-5128 gave no significant effect on the glucose-stimulated increase in incorporation of [ 3H]leucine into the pro-insulin and insulin fractions, while tolbutamide significantly inhibited the incorporation especially at a low glucose concentration (1 mg/ml). These and the previous findings indicate that DG-5128 is a new class of hypoglycemic agent with a unique mode of action different from the known hypoglycemics ever reported.

Maximal elevation of 2,3-diphosphoglycerate concentrations in human erythrocytes: influence on glycolytic metabolism and intracellular pH.

The 2,3-DPG content of human red blood cells can be elevated in vitro to a maximum of 24 μMoles/g by incubating the cells in media containing inosine, pyruvate and inorganic phosphate (=IPP media). The rate of accumulation depends on the extracellular phosphate level. The concentrations of organic phosphate fractions other than 2,3-DPG also increase during the initial phase of incubation in IPP media, but rediminish thereafter. As a consequence of these changes, the total concentration of acid-soluble organic phosphates in the red cells rises from 14 to 55 μMoles P/g red cells. This increase of non-penetrating anions produces a shifting of the Donnan ratio H e +/H i + to lower values and thereby diminishes progressively the intracellular pH of the red cells during incubation in IPP media. The extent of these changes can be calculated on the basis of equations derived by van Slyke. The Donnan induced intracellular acidification causes a gradual impairment of red cell metabolism as the 2,3-DPG concentration increases, thus imposing a selflimitation to the accumulation of 2,3-DPG in the presence of IPP and leading to an inhibition of glucose consumption in IPP-pretreated cells. The findings are discussed with respect to their metabolic and biophysical basis and in view of possible implications for the regulation of red cell metabolism and function.

Time course of accumulation of UDP- N-acetylamino sugar derivatives in Staphylococcus aureus

Under incubation conditions including deprivation of nitrogen sources, deprivation of lysine, inhibition by oxamycin and inhibition by penicillin, the accumulation of UDP- N-acetylamino sugar derivatives in Staphylococcus aureus cells, with time, has been studied. UDP- N-acetylglucosamine and UDP- N-acetylglucosamine-3- O-lactic ether accumulated in cells which were incubated in amino acid-free medium. During the initial phase of incubation there was a rapid rise in the appearance of UDP- N-acetylglucosamine followed later by a decrease of this nucleotide; concomitant accumulation of UDP- N-acetylglucosamine-3- O-lactic ether and UDP- N-acetylglucosamine-3-O-lactyl-peptides was observed under every condition which induced UDP- N-acetylglycosamine-3- O-lactyl-peptide accumulation. The relationship of the observed accumulation to the pathway of cell-wall mucopeptide synthesis is discussed.