Regulation of Aspergillus nidulans penicillin biosynthesis and penicillin biosynthesis genes acvA and ipnA by glucose.

Expression of the Aspergillus nidulans penicillin biosynthesis genes acvA and ipnA, encoding delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase and isopenicillin N synthetase, respectively, was analyzed. The intergenic region carrying the divergently oriented promoters was fused in frame in both orientations to Escherichia coli lacZ and E. coli uidA reporter genes. Each construct permits simultaneous expression studies of both genes. Transformants of A. nidulans carrying a single copy of either plasmid integrated at the chromosomal argB locus were selected for further investigations. Expression of both genes was directed by the 872-bp intergenic region. ipnA- and acvA-derived gene fusions were expressed from this region at different levels. ipnA had significantly higher expression than did acvA. Glucose specifically reduced the production of penicillin and significantly repressed the expression of ipnA but not of acvA gene fusions. The specific activities of isopenicillin N synthetase, the gene product of ipnA, and acyl coenzyme A:6-aminopenicillanic acid acyltransferase were also reduced in glucose-grown cultures.     

Effect of penicillin precursors on antibiotic biosynthesis in various strains]

The regularities of biosynthesis of 6-aminopenicillanic acid (6-APA), benzylpenicillin (BP) and phenoxymethylpenicillin (PMP) by the strains under the investigation did not significantly differ. In the absence of the precursor both the strains mainly synthesized 6-APA. Phenylacetic acid (PAA) and phenoxyacetic acid (POAA) provided directed biosynthesis: the fungus synthesized BP or PMP depending on the precursor nature. When the amount of the precursors was not sufficient, 6-APA was synthesized along with the penicillins. PAA proved to be a more active precursor than POAA. When both precursors were present in the fermentation broth, only BR was synthesized. An important distinction of strain 316A was its increased sensitivity to PAA especially in the initial period. After an increase in the PAA concentration the growth rate of strain 316A lowered to a greater extent than that of strain 284A. This was likely to determine the higher levels of penicillin production by strain 316A in the presence of POAA, a nontoxic precursor. A procedure for supplying the precursors was developed. Under the laboratory conditions it provided high levels of the penicillin production.     

Carbon metabolism under conditions of regulated penicillin biosynthesis]

Carbon metabolism of P. chrysogenum under conditions of periodical addition of the nutrients was studied. It was found that a proper rate of the carbon source addition to the culture was of significant importance for intensive biosynthesis. The use of carbon for the energetic and constructive needs was not the same at different fermentation periods.     

Physiological role of fats in the process of penicillin biosynthesis]

The level of penicillin production in the presence of whale oil was shown to be higher. The stimulating effect of the oil was connected with accumulation of large biomass rather than with its specific effect on the biosynthesis. At the beginning of the process the oil eliminated the biomass accumulation lag-phase connected with beta-galactosidase repression by glucose. During the second part of the fermentation process the oil acclerated the culture growth in the presence of lactose. The rate of the oil consumption calculated for carbon was higher than that of the lactose utilization. The presence of the oil in the medium did not prevent the lactose consumption.     

Penicillium chrysogenum mycelial productivity in the 1st phase of penicillin biosynthesis]

The course of the mycelium low productivity during the first phase of the usual two-stage process of penicillin biosynthesis was studied. It was found that the low productivity of the mycelium at the beginning of the fermentation process was probably associated with catabolic regression of the penicillin-producing system. The high specific growth rate registered in the experiments (0.06-0.08 hours-1) had no negative effect on the mycelium productivity. It was not possible to connect the productivity level with the mycelium age, because young and mature mycelium had the same producitivity levels at any developmental stage under the same conditions.     

l-Lysine repression of penicillin biosynthesis and the expression of penicillin biosynthesis genes acvA and ipnA in Aspergillus nidulans

The addition of 0.1 M L-lysine to the fermentation medium reduced the production of penicillin by about 50% in Aspergillus nidulans. To analyse this effect at the molecular level, the expression of the penicillin biosynthesis genes acvA and ipnA, encoding delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase and isopenicillin N synthetase, was studied by using translational fusions with different reporter genes (strain AXB4A, acvA-uidA, ipnA-lacZ fusions; AXB4B, acvA-lacZ, ipnA-uidA fusions) integrated in single copy at the chromosomal argB locus of Aspergillus nidulans. Irrespective of the reporter genes used the expression of acvA and ipnA fusion genes was repressed in L-lysine grown cultures. The expression of a fusion gene of an A. nidulans primary metabolism gene (oliC-lacZ) was not affected by L-lysine.     

The effect of malonate on lipid biosynthesis in the liver]

Malonate regulates the liver metabolism and promotes stimulation of the fatty acids synthesis and pyruvate oxidation inhibition. The latter is particularly significant in regulation of aerobic processes and responsible for antihypoxic action of malonate.     

Dose-dependent effect of penicillin on activity of metabolic enzymes in Staphylococcus epidermidis]

The study was concerned with investigation of the biochemical properties, antibiotic resistance and the effect of various doses of penicillin on the activity of metabolic enzymes in the bacterial cells of Staphylococcus epidermidis isolated from the pharynx mucosa of healthy subjects. The study revealed an increase in the aggressive properties of the representatives of the mouth normal microflora. It was also observed that the highest percentage of the staphylococcal isolates was resistant to beta-lactam antibiotics. The effect of various concentrations of penicillin on the microbial metabolism was shown to be directed at different targets. Penicillin intensified the aerobic processes and lipid synthesis in the bacterial cells. The reactions of the processes of the amino acid metabolism proceeded in different directions. Some concentrations of penicillin inhibited such processes.     

Involvement of microbodies in penicillin biosynthesis.

Penicillium chrysogenum strains were constructed which express a mutant acyltransferase lacking the putative targeting signal for microbody proteins. The mutated enzyme was located in vacuoles and in neighbouring cytoplasm. Although acyltransferase was expressed in vivo and was active in vitro, the mutants did not produce penicillin. The results demonstrate the involvement of microbodies in penicillin production.