Kinetics of microbial cell growth

As a rate equation of microbial cell growth, the Monod equation is widely used. However, this equation cannot fully correspond to real courses of microbial cell growth in many batch cultivations. Especially, predicted values based on this equation do not agree with observed values in many continuous cultivations. In this paper, which introduces new concepts of critical concentration and coefficient of consumption activity, the growth rate equation which corresponds to the whole period including lag period is newly derived and characteristics of microbial cell growth in batch cultivation are clarified. Further, applying the new rate equation to continuous cultivation, a general equation with which to calculate cell concentration is derived and characteristics of microbial cell growth in continuous cultivation are clarified. The calculated values of cell concentration based on the new theory showed quite good agreement with the observed values in both batch and continuous cultivation.     

Development of the bitterling,Paracheilognathus himantegus (Cyprinidae), with a note on minute tubercles on the skin surface

The development of the eggs and larvae and minute tubercles on the skin surface ofParacheilognathus himantegus larvae were observed. The egg began to hatch approximately 68 hours after insemination and the larvae reached the free-swimming stage 23 days after hatching at water temperature of 22±1°C. The larval development and minute tubercles on the skin surface of this species were similar to those ofAcheilognathus lanceolata, A. limbata, A. signifer andTanakia tanago. However, the shape of the ripe eggs ofP. himantegus differed from those of the four species. As regards the shape of eggs, there was a common characteristic amongP. himantegus, Rhodeus uyekii andA. limbata from Korea. As regards larval development,P. himantegus had two characters also found inRhodeus. These facts seem to suggest thatP. himantegus is closely related toA. lanceolata, A. limbata, A. signifer andT. tanago but is more specialized than these four species, except forA. limbata from Korea.     

Nucleotide sequence of the chromosomal gene coding for the aminoglycoside 6-adenylyltransferase from Bacillus subtilis Marburg 168

Gene aadK of Bacillus subtilis is 855 bp long and codes for aminoglycoside 6-adenylyltransferase.     

Purification and spectral characterization of a 121-kilodalton phytochrome from etiolated pea (Pisum sativum L.) seedlings

Procedures for the purification of native phytochrome from etiolatedpea seedlings without the use of immuno-purification techniquesare described. Phytochrome (in the P_FR form) was purified bypolyethyleneglycol fractionation, adsorption to pentyl agaroseand batch elution, chromatography on DEAE-Sepharose, adsorptionto phenyl Toyopearl and batch elution, and chromatography onRed Toyopearl. The resulting phytochrome had specific absorbanceratios (SAR = A₆₆₆/A₂₈₀ of P_R) that ranged from 0.55 to 0.6.The subsequent chromatography on Sephacryl S-300 yielded verypure phytochrome with a SAR of 0.98. P_R and P_FR peaks in thedifference spectrum of the phytochrome were centered at 665and 730 nm, respectively. The spectral change ratio (Ar/Afr)of the difference spectrum was unchanged after the chromatographyon phenyl Toyopearl, and the value was 1.05–1.08, indicatingthat the spectral properties of this preparation were intact.The absorption spectra indicated that the peak absorbance ofP_FR was at 728–730 nm and that of P_R was at 666–667nm. These peak positions were essentially same as those obtainedwith the undegraded oat phytochrome. Incubation of the samplepurified on Sephacryl S-300 at 25?C for 5 h in either the P_Ror P_FR form did not result in degradation of the molecule. Therate of dark reversion of P_FR observed with the purified peaphytochrome was similar to that observed in vivo. The additionof dithionite had no effect on the reversion rate. ²Present address: Fuji-Gotenba, Research Lab. of Chugai PharmaceuticalCo. Ltd., Gotenba, Shizuoka, 412 Japan (Received February 22, 1990; Accepted May 28, 1990)     

Camptothecin analog (CPT-11)-sensitive human pancreatic tumor cell line QGP-1N shows resistance to SN-38, an active metabolite of CPT-11.

In the course of our study to determine the cross-sensitivity between CPT-11 and its active metabolite, SN-38, we found a SN-38-resistant human pancreatic tumor cell line, QGP-1N, which shows sensitivity to CPT-11. The IC50 of SN-38 was 152 times greater for QGP-1N than for SUIT-2, also a human pancreatic tumor cell line, whose IC50 of CPT-11 was similar to that for QGP-1N. The uptakes of CPT-11 and SN-38 and the intracellular conversion of CPT-11 to SN-38 could not explain the difference in sensitivity. DNA synthesis of QGP-1N cells was inhibited by CPT-11 which did not affect that of SUIT-2, while SN-38 inhibited the DNA synthesis of SUIT-2 at lower concentrations than that of QGP-1N. The inhibition test of topoisomerase I catalytic activity by CPT-11 or SN-38 revealed no difference in the biochemical properties of the topoisomerase I enzymes to the compounds between these two cell lines. These results indicate that CPT-11 should have its own inhibitory effect on DNA synthesis through a yet unknown mechanism in QGP-1N cells, although SN-38 plays an essential role in the antitumor activity of CPT-11 in SUIT-2 cells. In some cases, the antitumor effect of CPT-11 might be consequent not only on SN-38 but also on CPT-11 itself.