Kluyveromyces fragilis did not completely ferment early harvest Jerusalem Artichoke extracts. This unsatisfactory performance was due to the action of ethanol on the activity of the enzyme and on the substrate. The hydrolysis of polyfructosans is the limiting step in the fermentation process. A solution would be to improve this step by using an aerobic phase to increase biomass prior to the anaerobic fermentation phase. This way, early harvest extracts can be fermented in less than 44hr with a satisfactory ethanol yield (65g•l-1)
During an 18-month period, heterotrophic bacteria were quantified and the rates of glucose mineralization were measured in samples from the sediment-water interface of Bethel Lake, a small productive lake located in the city of Sudbury, Ontario, Canada. Among three incubation temperatures 2°C, 18°C, and 37°C, the highest bacterial counts were obtained consistently at 18°C. With incubation at 2°C the highest counts occurred when the water temperature in the lake was 10°C or lower, and psychrophilic bacteria were recovered only at such times. Most of the 2°C and 18°C isolates were psychrotrophs. Some of the 18°C isolates were incapable of growth at either 2°C or 37°C, the extreme recovery temperatures examined. Turnover times and heterotrophic potentials for the substrate of interest were calculable for seven of the eight mineralization experiments. Substrate turnover occurred more quickly and the potential for glucose mineralization was always greater at the higher test temperature, for a given sampling. Cold water temperatures did not preclude glucose mineralization.
We have prepared plasmids containing various lengths of palindrome. When the palindrome is longer than 184bp, the plasmid can not grow in wild-type Escherichia coli, but a plasmid with a palindrome less than 95bp can. The absolute length of the palindrome determines whether the plasmid can grow or not. Electron microscopy confirmed that the plasmid with palindrome had a relaxed form with cruciform structure. The length of the protruding region is not the same size as the palindrome inserted into the plasmid but the self-annealing length seems to be just enough to make the twisted molecule into the relaxed form. Although plasmids with palindromes longer than 184bp multiply in E. coli recB recC sbcB recF, deletions occur in the palindromes and these deletions seem to occur at a specific site.
We have prepared plasmid pLIOP3, a derivative of λdv whose pRoR-tof region was replaced by lacPO (lactose promoter-operator)-lacI (repressor for the lac operon). pLIOP3 did not transform Escherichia coli polA. A mutant of pLIOP3 which could multiply as a plasmid was isolated after hydroxylamine mutagenesis. The mutant had two base substitutions in lacPO, which made the operator constitutive. The mutant could become transformed even after the removal of the replication origin of pBR322 which was contained in pLIOP3. The mutant which contains only the replication origin of λ is named pLmI3. The synthesis of pLmI3 DNA was stimulated about 10-fold by the addition of an inducer of lactose promoter and the DNA recovered after induction had the same structure and biological activity as that recovered before induction. Cells carrying pLmI3 were killed. by the induction. The replication of pLmI3 DNA depended on O and P gene products and the "ori" region of λdv.
We studied how to control the ability of Lipomyces starkeyi cells to grow and accumulate lipid by adding inorganic elements. Adding Zn2+, Mn2+, and monopotassium phosphate at a stationary phase of growth caused rapid changes. However, adding these elements individually did not induce any marked changes in the cell growth and lipid accumulation. When these elements were added simultaneously, the yeast underwent a second logarithmic growth and the respiration rate increased. Concurrently, this addition stopped the normal increase in the amount of lipid in the culture (mg of lipid/ml of culture), and decreased the lipid content of the cells (mg of lipid/108cells). The periods of second logarithmic growth and the cessation of lipid accumulation were shortened when monopotassium phosphate was not added. The function of monopotassium phosphate was replaced by another buffer chemical.
We analyzed the DNA sequence changes in UV-induced mutagenesis of a chloramphenicol resistance gene of E. coli which was cloned on a plasmid. Both base change and frameshift mutations were observed after UV irradiation of the plasmid DNA. In base change mutations, GC to AT transitions were predominant. They appeared at the 3′C of 5′-Pyr-C-3′ sequences. This supports the hypothesis that the Pyr(6, 4)Pyo product is the main cause of UV-induced base-change mutations. Frameshift mutations with single-base deletion or insertion were found at sequences where the AT base pairs were repeated. This indicates that pyrimidine dimers induce frameshift mutations.
We have constructed a restriction map of the colicinogenic plasmid pKY-1 and analyzed its genetic structure. Although the cleavage map of pKY-1 is completely different from that of ColE1, the arrangement of its genes cea and imm and the region of origin (replication origin) is the same as that of ColE1. The nucleotide sequence of the region of origin and of the cea, imm and kil genes was determined. The sequence of the region of origin is almost identical with that of ColE1. The sequence of the RNAI deduced from the sequence is a hybrid of ColE1 and CloDF13 consistent with the fact that pKY-1 is compatible with ColE1. The amino acid sequence of colicin E1 deduced from the nucleotide sequence is almost identical with that of colicin E1. However, significant substitutions of amino acids in colicin E1 were observed in the region which would correspond to the N-M junction of colicin E1.