Growing cultures

Following the realization that the presence of phenylacetic acid in the fermentation led to a simplification of the mixture of penicillins produced by the fungus due to preferential uptake of this acid and its incorporation into benzylpenicillin (4), a wide variety of other acids were added to the growing culture. Inclusion of the appropriate acids in the culture medium thus afforded, respectively, phenoxymethylpenicillin (5, penicillin V), phenethicillin propicillin (7), and phehbencillin... 

ZUchtung, /, breeding, growing, culture. ZUchtungsgefass, n. growing vessel (for crystals) culture vessel. 

Place the flask in a temperature-controlled shaker at 37 °C. The exponential growth phase will last from 2 to 24 hours after inoculation. The exact time and duration depend on the physiological condition of the inoculum. The data in Table 10.1 are plotted and a growth curve will be obtained for an exponentially growing culture. Figure 10.2 shows the typical growth curve obtained for a viable organism. 

Yee JA, Yan L, Dominguez JC et al (1993) Plasminogen-dependent activation of latent transforming growth factor beta (TGF beta) by growing cultures of osteoblast-hke cells. J Cell Physiol 157 528-534... 

The time interval between one cell division and the next is called the generation time. When considering a growing culture containing many thousands of cells, a mean generation time is usually calculated. 

In a normally growing culture of lysogenic bacteria, the majority of bacteria manage to keep their prophages in a dormant state. In a very small minority of cells, however, the prophage genes express themselves. This results in the multiplieation of the virus, lysis of the cells and liberation of infectious particles into the medium. 

In order to define the conditions of the growing cultures, buffered medium (VL) inoculated with E, coli ATCC 11775 and supplemented with nitrate, glucose and DMA was incubated at 37 C, and pH, nitrite concentration, nitrate concentration, cell growth and nitrosamine formation were followed (Fig. 1). Within 2 hrs, >90% of the nitrate is converted to nitrite (some of the nitrite is further reduced) and over 8 hrs the pH drops from 7.3 to 6.0. This would indicate that in experiments carried out for 20 hrs or more the control medium should be adjusted to pH 6.0 to 6.5 and nitrite should be added rather than nitrate. Such a control medium (VL) was supplemented with nitrite and DMA and NDMA formation was followed (Fig. 2). It can be seen that even without the addition of cells the rate of nitrosation is 4 fold greater than... 

These results led us to reexamine the published work on nitrosation in the presence of bacteria (Table II) In two of the studies (, 10) the amount of NDMA formed is actually less than the amount that can be predicted from theoretical consideration of the uncatalyzed chemical reaction alone (15) In another study (12), the yield of NDMA is again slightly lower than the predicted chemical yield at the final pH (6 0) of the growing culture The work by Kunisaki and Hayashl (13), on the other hand, does indicate that resting cells of E. coli B catalyze... 

A comparison had been made of fractionation during the dechlorination of tetrachlo-roethene by Sulfurospirillum multivorans and Desulfitobacterium sp. strain PCE-S in laboratory experiments (Nijenhuis et al. 2005). Isotope fractionation in growing cultures was 1.0052 for Desulfitobacterium sp. and only 1.00042 for Sulfurospirillum multivorans, whereas fractionation was greater in crude cell extracts from both strains. It was concluded that caution should therefore be exercised in applying fractionation factors to the evaluation of in situ bioremediation. 

To establish whether rifaximin, like the other members of the rifamycin family [36, 58], specifically inhibits bacterial RNA synthesis the effect of this antibiotic as well as that of rifampicin and chloramphenicol on RNA (via 3H-uridine incorporation), DNA (via 3H-thymidine incorporation) and protein (via 35S-methionine incorporation) synthesis was studied in growing cultures of Escherichia coli [59], While chloramphenicol reduced protein synthesis, both rifaximin and rifampicin inhibited RNA synthesis in a concentration-dependent fashion. In contrast, none of them affected 3H-thymidine incorporation into DNA. These data suggest that rifaximin, like rifampicin, inhibits RNA synthesis by binding the (3 subunit of the bacterial DNA-dependent RNA polymerase [60],... 

The cell titer of an exponentially growing culture of cells in CM 10 is determined with a Coulter counter. The cell suspension is centrifuged at 70 g for 5 min and the supernatant is reduced such that 3 ml contains approximately 5 x 106 cells (3-h treatment) or 2 x 106 (treatment more than 3 h). 

Off-gas analysis is widely used in many industrial fermentation plants to determine the cellular activity of growing cultures by monitoring respiration. One can measure oxygen uptake and CO2 production rates and thus measure metabolic activity/9 In addition, off-gas analysis is also used for monitoring other volatiles, the synthesis of which are strongly dependent on cultivation conditions 10 and product formation. 11 Off-gas estimation and control therefore serves as an indirect method for process analysis and control. 

Johnson et al. (1999) measured 5 " Se in volatilized Se, presumably in the form of alkylselenides, that was generated by cyanobacterial mats and incubated soils. For the cyanobacteria, an early sample of a vigorously growing culture yielded no measurable difference between the volatilized Se and the growth medium, whereas a later sample was enriched in the hghter isotope by 1.1 %o. In the soil volatilization experiments, four samples from two different incubated soils were analyzed. All of the samples 8 Se values were within 0.6%o of the total Se in the soil. Both the cyanobacteria and soil experiments were not highly controlled, but they do suggest that isotopic fractionation related to volatilization is small. 

Hillmer P, Gest H. 1977. H2 metabolism in the photosynthetic bacterium Rhodopseudomonas capsulata H2 production by growing cultures. J Bacteriol 129 724-31. 

Figure 18.3. Desulfovibrio vulgaris Hildenborough attachment kinetics to mild steel coupons under various Fe. Metal coupons (1.5 x 6.0 cm) were suspended into 24-h growing cultures under various Fe concentrations and removed at the times indicated. Coupons were washed with distilled water, dried, fixed with 5% gluteralde-hyde, and analyzed by scanning electron microscopy. The bacterial count at each datum point represents an average of 10 random sites on the coupon, counted from scanning micrographs and equated to a number (10 cells) per unit area (mm ) metal.

Cord-Ruwish R, Widdel F. 1986. Corroding iron as a hydrogen source for sulphate-reduction in growing cultures of sulphate-reducing bacteria. Appl Microbiol Biotechnol 25 169-74. 

Gest, H., Kamen, M.D. 1949a. Studies on the metabolism of photosynthetic bacteria photochemical production of molecular hydrogen by growing cultures of photosynthetic bacteria. J Bac-teriol 58 239-245. 

Grow cultures at 32°C in a shaker until the ODesonm reaches 0.6-0.8. 

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