Incubation

About: Incubation is a(n) research topic. Over the lifetime, 5748 publication(s) have been published within this topic receiving 126541 citation(s).

Prolonged incubation in calcium chloride improves the competence of Escherichia coli cells.

Abstract: Escherichia coli cells are 4—6 times more transformable and 20—30 times more competent after 24 h incubation in cold calcium chloride than immediately after calcium chloride treatment. With 24-h-old competent cells we obtained routinely 2 · 107 transformants per μg of pBR322 DNA, and transformed over 20% of viable cells.

Nitrogen Mineralization Potentials of Soils

Abstract: Net mineralization of N in 39 widely differing soils was determined over a 30-week period at 35C, using incubation intervals of 2, 2, 4, 4, 4, 6, and 8 weeks. Mineral N was leached from the soils before the first incubation and following each of seven incubations by means of 0.01M CaCl₂ and a minus-N nutrient solution. Soil water contents were adjusted by applying suction (60 cm Hg), and losses of water during incubation under aerobic conditions were negligible. With most soils, cumulative net N mineralized was linearly related to the square root of time, t½. The pH of soils changed very little in the course of 30 weeks' incubation. Because of the generally consistent results, the data were employed in calculating the N mineralization potential, Nₒ, of each soil, based on the hypothesis that rate of N mineralization was proportional to the quantity of N comprising the mineralizable substrate. Values of Nₒ ranged from about 20 to over 300 ppm of air-dry soil. The fraction of total N comprising Nₒ varied widely (5 to 40%) among soils. Mineralization rate constants did not differ significantly among most of the soils. The most reliable estimate of the rate constant, k was .054 ± .009 week⁻¹. The time required to mineralize one-half of Nₒ, t½, was estimated to be 12.8 ± 2.2 weeks. Results suggest that the forms of organic N contributing to Nₒ were similar for most of the soils.

Dynamics of Gross Nitrogen Transformations in an Old-Growth Forest: The Carbon Connection

Abstract: We conducted a 456-d laboratory incubation of an old-growth coniferous forest soil to aid in the elucidation of C controls on N cycling processes in forest soils. Gross rates of N mineralization, immobilization, and nitrification were measured by 'IN isotope dilution, and net rates of N mineralization and nitrification were calculated from changes in KCl-extractable inorganic N and NOE-EN pool sizes, respectively. Changes in the availability of C were assessed by monitoring rates of CO, evolution and the sizes of extractable organic C and microbial biomass pools. Net and gross rates of N mineralization (r2 = 0.038, P =.676) and nitrification (r2 = 0.403, P = .125) were not significantly correlated over the course of the incubation, suggesting that the factors controlling N consumptive and productive processes do not equally affect these processes. A significant increase in the NO, pool size (net nitrification) only occurred after 140 d, when the NO3- pool size increased suddenly and massively. However, gross nitrification rates were substantial throughout the entire incubation and were poorly correlated with these changes in NO3 pool sizes. Concurrent decreases in the microbial biomass suggest that large increases in NO3 pool sizes after prolonged incubation of coniferous forest soil may arise from re- ductions in the rate of microbial immobilization of NO3, rather than from one of the mechanisms proposed previously (e.g., sequestering of NH,+ by microbial heterotrophs, the deactivation of allelopathic compounds, or large increases in autotrophic nitrifier pop- ulations). Strong correlations were found between rates of CO2 evolution and gross N mineralization (r2 = 0.974, P < .0001) and immobilization (r2 = 0.980, P < .0001), but not between CO, evolution and net N mineralization rates. Microbial growth efficiency, determined by combining estimates of gross N immobilization, CO2 evolution, and micro- bial biomass C and N pool sizes, declined exponentially over the incubation. These results suggest the utilization of lower quality substrates as C availability declined during incu- bation. Results from this research indicate the measurement of gross rates of N transfor- mations in soil provides a powerful tool for assessing C and N cycling relationships in forests.

Thermal Tolerance of Avian Embryos: A Review

Abstract: Avian eggs usually experience temperatures of 30 to 400C during the incubation period, but eggs often cool to much lower temperatures. Hyperthermia is less common. Passerines do not show higher incubation temperatures than other orders that have been studied extensively. Field measurements of incubation temperatures are usually lower than the optimal temperatures for development found in laboratory studies. Some species regulate egg temperatures closely throughout incubation; but in at least one penguin species, mean egg temperature increases and ranges of egg temperature decrease through the incubation period. Both the optimal temperature for continuous exposure and the range of temperatures producing high survivorship differ among species. Species also differ in their responses to temperature exposures of limited duration. Thus, the use of a "physiological zero" applicable to all species is not warranted. Penguins have both a lower optimum and a broader range of acceptable incubation temperatures than do other species studied. Age, duration, and temperature of exposure significantly affect survivorship. Hyperthermia is evidently more injurious to the developing embryo than is hypothermia. Resistance to cold exposure is a heritable trait, but the genetics and physiology of the response(s) are not known. For older embryos, the physiological effects of hyperthermia are similar to those of adult birds in terms of the organ systems that are first to fail. An estimate of thermal tolerance for short exposures in most species studied is 16 to 41 C and, for exposures lasting several hours, 36 to 390C.

Distinct prion proteins in short and long scrapie incubation period mice

Abstract: The Prn-i gene, controlling scrapie incubation period, is linked to or congruent with the murine prion protein (PrP) gene, Prn-p . In prototypic mouse strains with long (ILn) and short (NZW) incubation periods, Prn-p transcription is initiated at similar multiple sites. The predicted NZW and ILn PrP proteins differ at codons 108 and 189. Codon 189, highly conserved in mammals, lies within a polymorphic BstEll site that is retained in 17 mouse strains known to have short or intermediate incubation times, but is absent in ILn and two other inbred mice with long incubation times. Codon 108 in mice with short or intermediate incubation times encodes Leu; in mice with long incubation times it encodes Phe. The correlation of PrP sequence with length of scrapie incubation period suggests, but does not formally prove, congruency between Prn-p and Prn-i .