[Microbial models in screening of inhibitors of sterol biosynthesis]

On the base of previously developed microbial models high effective scheme for screening of inhibitors of sterol biosynthesis (ISB) is proposed. It is based on cultivation of halophilic bacteria Halobacterium salinarum (former Halobacterium halobium), possessing mevalonate pathway of sterol biosynthesis, and cultivation of fungus Acremonium fusidioides (former Fusidium coccineum), that is producer of steroid antibiotic fusidin (fusidic acid), which biosynthesis has great similarity (with coincidence of its initial steps till squalene formation) to cholesterol biosynthesis in human organism. In H. salinarum model ISB are revealed as compounds that inhibit test-culture growth, whereas in A. fusidioides test-system they are revealed as compounds that strongly reduce fusidin production without any visible influence on producer's growth. Mevalonate that is one of the crucial intermediates of sterol biosynthesis remove inhibition induced by many microbial metabolites that is the evidence of their action at early stages of sterol biosynthetic pathway, including HMG-CoA reductase step. Both test-systems are developed as micromethod and could be easily mechanized due to miniaturization of microbiological procedures, cultivation in sterile 96-well plates and usage of automatic micropipettes and dispensers. Effectiveness of both test-systems, as well as their sensitiveness, laboriousness and ability to give false-positive or false-negative results in ISB screening work is compared. The proposed scheme of screening of ISB includes microbial models at early steps of screening procedures and Hep G2 test-system at the late step. The preliminary screening of microbial metabolites possessing antifungal activity at initial step is compulsory. Miniaturization and mechanization of microbial processes and purification of producers' culture broth with micro- and ultrafiltration are under consideration as well.

Stimulation of cephalosporin C production in Acremonium chrysogenum M35 by glycerol

In this study, the effects of glycerol on cephalosporin C production by Acremonium chrysogenum M35 were evaluated. The addition of glycerol increased cephalosporin production by up to 12-fold. Glycerol caused the upregulation of the transcription of the isopenicillin synthase (pcbC) and transporter (cefT) genes in early exponential phase, and affected the cell morphology since hyphal fragments differentiated into arthrospores. These results indicate that glycerol effectively enhances cephalosporin C production via stimulation of cell differentiation.

Activity profile in vitro of micafungin against Spanish clinical isolates of common and emerging species of yeasts and molds

A collection of 2,278 isolates belonging to 86 different fungal species was tested with micafungin and eight other drugs using the EUCAST procedures. Micafungin was active against species of Candida and Aspergillus (even azole-resistant species) as well as Penicillium spp., Scedosporium apiospermum, and Acremonium spp. It was inactive for species of Basidiomycota and Mucorales and for multiresistant species such as those of Fusarium.

Invasive Acremonium strictum infection in a bone marrow transplant recipient

We describe an invasive Acremonium strictum infection in a 9-year-old debilitated bone marrow transplant recipient. Outcome was successful, despite resistance to the amphotericin B that was initially administered. A. strictum was isolated from bone and urine cultures. We summarize data on 15 opportunistic invasive infections caused by Acremonium in pediatric hosts reported thus far in the English language literature.

Effects of some benzoxazinoids on in vitro growth of Cephalosporium gramineum and other fungi pathogenic to cereals and on Cephalosporium stripe of winter wheat

The benzoxazolinones benzoxazolin-2(3H)-one (BOA) and 6-methoxybenzoxazolin-2(3H)-one (MBOA) and selected degradation products of these compounds were examined for their in vitro antifungal activity against Cephalosporium gramineum, Gaeumannomyces graminis var. graminis, and Fusarium culmorum. BOA was also applied to the soil-incorporated inoculum of C. gramineum to test its capability of reducing Cephalosporium stripe disease in winter wheat. MBOA reduced the mycelial growth of G. graminis var. tritici, C. gramineum, and F. culmorum by 50% (EC50) at the concentrations of 77, 134, and 271 microg/mL of corn meal agar, respectively, and the corresponding BOA EC50 values for the fungi were 11, 189, and 456 microg/mL. BOA degradation products 2-amino-3H-phenoxazin-3-one (APO), 2-acetylamino-3H-phenoxazin-3-one (AAPO), and o-aminophenol (o-AP) were much more inhibitory to the growth of C. gramineum and G. graminis var. tritici than the parent compounds. APO, AAPO, and o-AP EC50 values were found to be as low as 0.58, 4.57, and 1.4 microg/mL, respectively, for C. gramineum and 0.78, 2.18, and 0.80 microg/mL for G. graminis var. tritici. These compounds applied at the corresponding concentrations did not significantly affect the mycelial growth of F. culmorum. The treatment of C. gramineum inoculum with a 1% water solution of BOA resulted in a significant reduction infection of winter wheat with C. gramineum as compared to the control with the untreated inoculum,but this treatment was not as effective as the application of a commercial fungicide.

Enhancement in antimicrobial activity of 2-(phenyl)-3-(2-butyl-4-chloro-1H-imidazolyl)-5-butylate isoxazolidine

The trans rich isomer, 2-(phenyl)-3-(2-butyl-4-chloro-1H-imidazolyl)-5-butylate isoxazolidine A (>96% ee) was synthesized by the condensation of E isomer rich nitrone 4 (>98% ee) with butyl acrylate in an inert solvent. Obtained isoxazolidine was screened for its antifungal activity against Aspergillus niger, Cephalosporium acremonium, Fusarium moniliforme by using Nystatin as positive control. It was also tested for its antibacterial activity against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus by using Streptomycin as positive control. Enhanced antifungal activity was observed in isoxazolidine of >96% ee compared to the isoxazolidine of >69% ee (B), and enhancement was not observed in antibacterial activity.

Strain improvement for cephalosporin production by Acremonium chrysogenum using geneticin as a suitable transformation marker

An Acremonium chrysogenum strain improvement program based on the transformation with cephalosporin biosynthetic genes was carried out to enhance cephalosporin C production. Best results were obtained with cefEF and cefG genes, selecting transformants with increased cephalosporin C production and lower accumulation of biosynthetic intermediates. Phleomycin resistant transformants, designated B1 and C1, showed a single copy random integration event, higher levels of cefEF transcript and, according to immunoblotting analyses, higher amounts of deacetylcephalosporin C acetyltransferase (DAC-AT) protein than their parental strains. Moreover, DAC-AT activity was higher in the transformants. Plasmids carrying geneticin resistance markers based on the nptII gene from Tn5 and the aphI gene from Tn903 were constructed to transform again B1 and C1, showing that the cassette Pgdh-nptII-trpC was able to confer geneticin resistance to A. chrysogenum and demonstrating that geneticin is a helpful selection marker.

[Antifungal susceptibility of Acremonium species using E-test and Sensititre]

Filamentous fungi have become a common cause of severe infections, especially in immunocompromised patients. In recent years, the number and diversity of the infections caused by Acremonium species have increased and numerous species have been implicated. As is the case for most emerging pathogens, the optimal therapeutic approach to Acremonium species remains to be determined. We used two methods to determine the in vitro susceptibility to amphotericin B, itraconazole and fluconazole for 15 clinical isolates of eight different species of Acremonium. The MICs were determined according to protocol M38-A of the National Committee for Clinical Laboratory Standards (NCCLS) document, using the Sensititre and E-test microdilution methods. Amphotericin B was effective in vitro for few species using the Sensititre method. However, high MICs were obtained with E-test. Fluconazole and itraconazole were ineffective according to both methods. Acremonium species are generally resistant to the most commonly used antifungal agents. Consequently, Acremonium susceptibility testing is recommended to assist in choosing adequate treatment of infections caused by this filamentous fungus.

Successful treatment of Acremonium fungemia with voriconazole

We report two cases of Acremonium fungemia with proven involvement of the skin and probably of the lung in patients who were both undergoing chemotherapy, one for mantle cell lymphoma and the other for acute lymphoblastic leukemia. Both patients failed amphotericin B deoxycholate treatment and were successfully treated with voriconazole with very mild toxicity.

Fungal peritonitis in 15 patients on continuous ambulatory peritoneal dialysis (CAPD). Fallberichte. Pilz-Peritonitis bei 15 Patienten mit ambulanter Dauerperitonealdialyse (CAPD)

Peritonitis is a frequent complication in patients with chronic renal failure on continuous ambulatory peritoneal dialysis (CAPD) treatment. The aim of this study was to know the prevalence of fungal peritonitis on patients undergoing CAPD, and to determine the antifungal susceptibility pattern of the identified isolates. Samples of the peritoneal dialysis fluid from 165 patients on CAPD treatment with peritonitis manifestations were submitted to mycological study (direct microscopic examination, culture and antifungal susceptibility test). Ten Candida isolates were identified, being C. albicans and C. parapsilosis the most common species. From isolates obtained, three species (C. albicans, C. parapsilosis, and C. guilliermondii) presented itraconazole resistance while C. glabrata was resistant to both itraconazole and ketoconazole. Aspergillus fumigatus was associated to peritonitis in three cases and Acremonium sp. in two.

The first echinocandin: caspofungin

The antifungal agent caspofungin is the first echinocandin that has been approved in the US and in Europe for treatment of invasive aspergillosis in adult patients who are refractory to or intolerant of conventional amphotericin B, its lipid-based formulations, and/or itraconazole. It is given as a 70 mg loading dose and a 50 mg daily maintainance dose as a one hour infusion. Due to low intestinal absorption an oral formulation has not been developed. Caspofungin is active against Candida spp. and Aspergillus spp. by inhibition the synthesis of beta-(1,3)-D-glucan, a cell wall component. The drug is inactive against Cryptococcus spp., Fusarium spp., Trichosporon spp., Rhizopus spp., and Pseudoallescheria spp. In invasive aspergillosis caspofungin resulted in higher response rates compared to a historic control under standard therapy. Efficacy data on persistently febrile neutropenic patients are pending. In several multicenter randomised double blind trials on candida infections caspofungin proved to be at least non-inferior to standard therapies. Reports of combination therapy or highly effective antifungal treatment (HEAT) in limited patient numbers are promising. New trials of combination therapy are warranted.

Stimulation of the cyanide-resistant alternative respiratory pathway by oxygen in Acremonium chrysogenum correlates with the size of the intracellular peroxide pool

The relationship between oxygen input and activity of the cyanide-resistant alternative respiration of submerged cultures of Acremonium crysogenum was investigated. The volumetric oxygen transfer coefficient of the respective cultures correlated positively within almost two ranges of magnitude with the size of the intracellular peroxide pool, which in turn, correlated with the activity of the cyanide-resistant alternative respiratory pathway. Increased aeration also stimulated the glucose uptake rate but had no effect on the total respiration rate or the growth rate. Addition of the lipid peroxyl radical scavenger DL-alpha-tocopherol to A. chrysogenum cultures decreased the rate of intracellular peroxide production as well as glucose uptake. An increase in the cyanide-resistant fraction of total respiration was observed, while growth and the total respiratory activity remained unchanged. We conclude that intracellular peroxides may stimulate the alternative respiration in A. chrysogenum.

Acremonium strictum pulmonary infection in a leukemic patient successfully treated with posaconazole after failure of amphotericin B

A severely neutropenic patient with chronic lymphocytic leukemia developed a diffuse bilateral pulmonary infection while receiving a therapeutic daily dosage of intravenous amphotericin B for Candida glabrata esophagitis. Computed tomography of the chest showed numerous lung nodules, ground glass areas and a pleural effusion. Biopsy of one nodule demonstrated hyaline septate hyphae. Multiple sputum cultures grew Acremonium strictum. Increasing the dose of amphotericin B and the addition of itraconazole did not resolve the infection. Change of treatment to posaconazole given orally at 200 mg four times/d resulted in progressive improvement leading finally to cure after 24 weeks of therapy. Treatment with posaconazole was clinically and biologically well tolerated.

Strain improvement studies for cephalosporin C production by Cephalosporium acremonium

Treatment of spore suspension of Cephalosporium acremonium ATCC 48272 with UV rays and N-methyl-N-nitro-N-nitrosoguanidine (NTG) induced mutants capable of producing higher yields of cephalosporin C. Antibiotic yield was improved from 630 micrograms/ml to 1995 micrograms/ml of the broth resulting in a high yielding mutant.

Cyanide-resistant alternative respiration is strictly correlated to intracellular peroxide levels in Acremonium chrysogenum

A strict correlation between the intensity of the cyanide-resistant alternative respiratory pathway and the intracellular peroxide levels in the cephalosporin C producer filamentous fungus Acremonium chrysogenum was demonstrated. Intracellular peroxide levels increased in a dose-dependent manner after addition of H2O2 to the culture media. A similar phenomenon was observed due to the specific inhibition of catalase by salicylic acid. In both cases, cyanide-resistant respiration was markedly stimulated. On the other hand, both cyanide-resistant respiration and intracellular peroxide levels were effectively suppressed by the lipid peroxyl radical scavenger DL-alpha-tocopherol, which breaks lipid peroxidation chains effectively. Our findings firmly supported the assumption that there is a connection between the intracellular peroxide levels and the intensity of the alternative respiratory pathway in fungi.

Acremonium strictum fungaemia in a paediatric patient with acute leukaemia

A 7-y-old boy with relapsed acute lymphatic leukaemia developed fungaemia due to Acremonium strictum, a fungus belonging to the group of the hyaline hyphomycetes. Initially, the fungus was misdiagnosed as Candida sp. due to the presence of abundant adventitious forms. At the time of diagnosis the patient was neutropenic and had a central venous catheter (CVC) in situ. The formation of an occlusive thrombotic mass in the v. subclavia dextra complicated the infection. Treatment consisted of amphotericin B, fluconazole, granulocyte colony-stimulating factor (G-CSF) and removal of the CVC. However the patient responded clinically only after the intravascular thrombus had been removed surgically. Amphotericin B, voriconazole and terbinafine showed high activity in vitro against the Acremonium isolate. A literature review revealed 5 other immunocompromised paediatric patients with a systemic or localized infection due to Acremonium spp.

[The effect of culture conditions on the fatty acid composition in the mycelium of the Cephalosporium sp]

The optimal condition of Cephalosporium sp. to culture mycelia and accumulate polyunsaturated fatty acid (PUFA) was researched. The optimal culture condition to get mycelium productivity was: maltose 60 g/L, KNO3 3 g/L, initial pH 6.0, 100 mL medium in 500 mL flask, seeding 25% (v/v), 25 degrees C culture it for 10 days. The optimal condition to accumulation PUFA proportion to total fatty acid was: glucose 10-20 g/L, NH4Cl or (NH4)2SO4 3 g/L, initial pH 4.0, 100 mL medium in 500 mL falsk, seeding 10-20% (v/v) and lighted it when it was cultured. It was suggested that two step could be used in the producing progress. A proposal was put forward that the oileic acid transformed to linoleic acid was the key step to produce PUFA. This proposal gave a base to research the optimal culture condition and enzyme regulation.

The role of the alternative respiratory pathway in the stimulation of cephalosporin C formation by soybean oil in Acremonium chrysogenum

Addition of soybean oil to Acremonium chrysogenum cultures growing on sugars doubled the specific production of cephalosporin C during the idiophase of growth. While the addition of soybean oil had no effect on the total rate of respiration, the respiration that proceeded via the alternative, cyanide-insensitive pathway exhibited a more than twofold increase. Addition of soybean oil also stimulated the formation of isocitrate lyase activities. Inhibition of oxidative metabolism of one of the products of isocitrate lyase (succinate) by thenoyltrifluoroacetone completely inhibited the alternative respiratory pathway. The role of soybean-oil-stimulated alternative respiration in the stimulation of cephalosporin C production and the role of isocitrate lyase are discussed.

Cephalosporin C production by Cephalosporium acremonium: the methionine story

More than 40 years ago, it was reported that methionine markedly stimulated production of cephalosporin C by Cephalosporium acremonium. Over the years, many hypotheses were put forth to explain this phenomenon. The accumulating evidence strongly supported the concept that methionine stimulates by inducing enzymes of the biosynthetic pathway such as delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase, isopenicillin N synthase, and deacetoxycephalosporin C synthase. This mechanism has been strengthened by the finding that transcription of the genes encoding the above enzymes is markedly enhanced by growth with methionine. An effect of methionine in the fermentation unrelated to the titer stimulation is its contribution of the sulfur atom to the cephalosporin molecule. Methionine also stimulates mycelial fragmentation; the relationship between this effect on hyphal differentiation and the induction of the cephalosporin synthases remains to be elucidated.

Inoculum preparation for in-vitro susceptibility testing of filamentous fungi

The percent transmission (T) and the equivalence in cfu/mL of two suspensions of 125 isolates of clinically important filamentous fungi containing 1-5 x 10(5) and 1-5 x 10(4) conidia/mL, adjusted with a haemocytometer, were determined. A wide variation of T values was observed, especially with the first inoculum. A good agreement was obtained between the counted and the viable propagules. The haemocytometric method is considered a useful technique for standardizing inocula.

Allosamidin inhibits the fragmentation of Acremonium chrysogenum but does not influence the cephalosporin-C production of the fungus

The pseudotrisaccharide allosamidin, a potent inhibitor of chitinases, retarded the fragmentation of hyphae but did not affect the fungal growth and cephalosporin-C production in Acremonium chrysogenum. In vitro inhibition of A. chrysogenum cell-bound chitinase(s) by allosamidin revealed that about 47% of the soluble intracellular chitinase activity was resistant to the inhibitory effect of allosamidin. On the other hand, about 76% of the total chitinase activity localised in both the soluble and insoluble enzyme fractions was effectively inhibited by allosamidin. All the chitinase activities were measured using a new procedure based on purified A. chrysogenum chitin as substrate.

Regulation of neuronal and recombinant GABA(A) receptor ion channels by xenovulene A, a natural product isolated from Acremonium strictum

Xenovulene A (XR368) is a natural product exhibiting little structural resemblance with classical benzodiazepines yet is able to displace high-affinity ligand binding to the benzodiazepine site of the gamma-aminobutyric acid (GABA)A receptor. We have characterized this compound and an associated congener (XR7009) by use of radioligand binding and electrophysiological methodologies with native neurons and the Xenopus oocyte expression system. Xenovulene A, and the more potent XR7009, inhibited [3H]flunitrazepam binding to rat forebrain with Ki values of 7 and 192 nM, and 1.7 and 42 nM, respectively, each site accounting for approximately 50% of the total specific binding. In cerebellar and spinal cord membranes, these ligands identified only single binding sites. These ligands demonstrated no intrinsic agonist activity at recombinant GABA(A) receptors comprising alpha1beta1gamma2S subunits expressed in Xenopus oocytes, yet at 1 microM both significantly potentiated the GABA-induced response and reduced the GABA EC50 from 10.9 (control) to 5.1 (Xenovulene A) or 2.7 microM (XR7009). The rank potency order for enhancement of the 10 microM GABA response is: XR7009 (EC50, 0.02 microM) > diazepam (0.03) > Xenovulene A (0.05) > flurazepam (0.17). The activity of XR368 and XR7009 was reduced by the benzodiazepine antagonist, flumazenil, and absent in receptors devoid of the gamma2 subunit. These agents exhibited receptor subtype selectivity because alpha3beta1gamma2S receptors were less sensitive to these compounds relative to alpha1 subunit-containing receptors, whereas alpha6beta1gamma2S receptors were completely insensitive. Potentiation of the response to GABA on native GABA(A) receptors in cortical neurons substantiates the profile of the novel structures of Xenovulene A and XR7009 as specific benzodiazepine agonists.

Effect of oxygen on the respiratory system and cephalosporin-C production in Acremonium chrysogenum

In this paper in vivo studies on the overall and cyanide-resistant respiration of Acremonium chrysogenum in connection with different oxygen transfer rates are discussed. Two parameters of the cyanide-resistant respiration, the activity and the capacity were examined separately during cultivation together with the possibly respiration-influencing factors like NADH/NAD content and ADP-limitation. It was finally concluded that the cyanide-resistant respiration seems to be independent of the amount and proportion of oxidized/reduced coenzymes and not limited by ADP or phosphate, but it is strongly affected by the oxygen available. It was also established that the examined path must have an important role in cephalosporin-C overproduction.

Effect of glyphosate on fungal population, respiration and the decay of some organic matters in Egyptian soil

Glyphosate (Roundup), when applied to the soil usually did not exert any significant effect on the total count of soil fungi after all periods of the experiment except after 6 and 10 weeks where the count was inhibited by the two doses used (1.84, 9.2 mg active ingredient/kg dry soil). When the herbicide was incorporated into the agar medium the count of total fungi, Acremonium strictum and Aspergillus fumigatus was significantly increased by the two doses used and of Penicillium glabrum by the high dose only. However, P. funiculosum was completely eliminated by the high dose. Oxygen consumption in soil treated with glyphosate was significantly inhibited by the high dose after 2 weeks and by the two doses after 6, 8 and 10 weeks. Glyphosate exerted two significant effects of stimulation and inhibition on the rate of the decay of stem segments of three plants at certain treatments of dose and time.

Exogenous methionine increases levels of mRNAs transcribed from pcbAB, pcbC, and cefEF genes, encoding enzymes of the cephalosporin biosynthetic pathway, in Acremonium chrysogenum

Methionine stimulated cephalosporin production in cultures of three different strains of Acremonium chrysogenum when added either at inoculation time or at 72 h to cells grown previously in the absence of methionine. When methionine was added at 72 h, the stimulation of cephalosporin biosynthesis was observed only 12 h later and required de novo protein synthesis. Methionine increased the levels of enzymes (isopenicillin N synthase and deacetylcephalosporin C acetyltransferase) expressed from genes (pcbC and cefG, respectively) located in the two clusters of cephalosporin biosynthesis genes in the wild-type A. chrysogenum strain and also in the two improved strains, CW19 and C10. Methionine-supplemented cells showed higher levels of transcripts of the four known genes (pcbAB, pcbC, cefEF and, to a slight extent, cefG) of the cephalosporin biosynthetic pathway than cells grown in the absence of methionine. The levels of the cefG transcript were much lower than those of the pcbAB, pcbC, and cefEF transcripts. The induction by methionine of transcription of the four cephalosporin biosynthesis genes and the known effect of this amino acid on the differentiation of A. chrysogenum indicate that methionine exerts a pleiotropic effect that coordinately regulates cephalosporin biosynthesis and differentiation.

Development of an homologous transformation system for Acremonium chrysogenum based on the beta-tubulin gene

The beta-tubulin gene was isolated from the filamentous fungus Acremonium chrysogenum using a heterologous gene probe to screen an A. chrysogenum lambda library. Sequencing of the A. chrysogenum gene revealed a mosaic gene which contains five exons and four intervening sequences. The exons encode for a polypeptide of 447 amino-acid residues which showed a high degree of similarity when compared with amino-acid sequences from beta-tubulins of other eukaryotes. The introns are characterized by typical consensus sequences found in intervening sequences from other filamentous fungi. In-vitro mutagenesis of codon 167 of the beta-tubulin gene resulted in the substitution of a phenylalanine by a tyrosine in the corresponding polypeptide sequence. The mutated gene was used successfully in the transformation and co-transformation of A. chrysogenum to benomyl resistance. The molecular analysis of transformants provided evidence that they contain the mutated beta-tubulin gene in addition to the wild-type gene, as was proved by Southern-hybridization analysis and direct sequencing of PCR amplification products.

Influence of dissolved oxygen concentration on the biosynthesis of cephalosporin C

Cephalosporin C was produced by a highly productive strain of Cephalosporium acremonium under industrial production conditions by fed-batch cultivation in a 40-l stirred-tank reactor using a complex medium containing 50 g l-1 peanut flour. The influence of dissolved oxygen concentration (pO2, DOC), which was maintained at different constant levels between 5 and 40% of its saturation value, during the production phase by means of a parameter-adaptive pO2-controller, on the cephalosporin C biosynthesis, was investigated. The concentrations of cephalosporin C (CPC) and its precursors penicillin N (PEN N), deacetoxycephalosporin C (DAOC), and deacetylcephalosporin C (DAC) were monitored by on-line HPLC. The concentrations of amino acids, valine (VAL), cysteine (CYS), alpha-amino-adipic acid (alpha-AAA), the dipeptide alpha-amino-adipyl-cysteine (AC), and the tripeptide alpha-amino-adipyl-cysteinyl-valine (ACV) were determined by off-line HPLC. By reducing the pO2 in the production phase from 40 to 5% of its saturation value, the CPC concentration diminished from 7.2 to 1.1 g l-1 and the PEN N concentration increased from 2.57 to 7.65 g l-1. The DAC concentration also dropped from 3.13 to 0.42 g l-1; however, the DAOC concentration was less influenced. The concentrations of AC and ACV were also less affected. The small DOC did not lead to an accumulation of the intermediate AC and ACV during the production phase. With increasing DOC in the range of 5-20%, the maximal specific production rate, the cell mass concentration-based and the substrate-based yield coefficients for CPC increased almost linearly, and fell back for PEN N.(ABSTRACT TRUNCATED AT 250 WORDS)

[The viability of species of microscopic fungi in nitrate-polluted water]

It has been found out, that contamination of marine and river water and soil with nitrates significantly influence the viability of microscopic fungi living there. This influence was positive when the nitrates content was moderate (from 0.2 to 2 g/l), extremely high concentrations of nitrates (20 g/l) lead to the inhibition of fungi growth and to their death.

[Induced variability in Acremonium chrysogenum, a producer of neutral-alkaline proteases and peptidases]

Lethal and mutagenic effects of N-nitrosomethyl biuret on the organism producing a complex of proteolytic enzymes i. e. Acremonium chrysogenum were studied. It was shown that methionine inhibited production of the protease complex in the induced prototrophic mutants. The selected mutants were classified according to the level of enzyme biosynthesis induction by methionine.

[Effect of lysine on cephalosporin biosynthesis and morphogenesis in Acremonium chrysogenum]

The effect of exogenic lysine on production of cephalosporin by auxotrophic and prototrophic strains of A. chrysogenum and their development was studied. It was shown that lysine added to the medium at a concentration of 0.5 or 1 mg/ml partially eliminated the effect of catabolic repression by glucose and had a stimulating effect on production of cephalosporin in the presence of sucrose. Both phenomena were most pronounced in the prototrophic strain 309-A. High concentrations of lysine (10 mg/ml) inhibited cephalosporin biosynthesis more intensively in the auxotrophic strain 291-A than in the prototrophic strain 309-A. Marked differences in the character of the culture development in media supplemented with 1 or 10 mg/ml of lysine were also observed.

Enhancement of cerulenin production by a natural zeolite, an ammonium ion-trapping agent

Addition of a natural zeolite, a known ammonium ion-trapping agent, to a complex medium resulted in a several fold increase in cerulenin production by Cephalosporium caerulens. In the presence of zeolite, ammonium ion in the medium decreased, while mycelial growth increased to a small extent, and pH values remained constant. Small amounts of ammonium bicarbonate inhibited cerulenin production without affecting mycelial growth and pH values. It is thus assumed that zeolite stimulated cerulenin production by releasing the biosynthesis from the suppression by ammonium ions in C. caerulens.

[Characteristics of cephalosporin C biosynthesis on a synthetic medium]

The attitude of the cephalosporin C-producing organism to various sources of carbon and nitrogen was studied. Carbohydrates such as maltose, starch and sucrose and nitrogen sources such as mineral ((NH4)2SO4 + KNO3) and organic nitrogen (asparagine) may be successfully used for the culture growth and antibiotic biosynthesis. The use of the mineral nitrogen necessitates additional regulation of pH during the cultivation process. The effect of pH on cephalosporin C biosynthesis was studied and its optimal values were found. It was shown that methyloleate played no specific role in cephalosporin C biosynthesis. It is an additional source of carbon which may be replaced by whale oil. It was demonstrated that the 1st stage of assimilation of inorganic sulfate, i.e. its reduction was blocked in C. acrimonium 218A. The study on the problem of phases in production of cephalosporin C showed that unlike the penicillin-producing organism C. acremonium had no capacity for the antibiotic biosynthesis at the early developmental stages irrespective of the cultivation conditions.

Relationship between carbon source and susceptibility of Cephalosporium acremonium to selected amino acid analogues

The susceptibility of Cephalosporium acremonium to selected amino acid analogues was markedly influenced by the carbon source used in the test media. Lysine hydroxamate, beta-hydroxy norvaline, and hexafluorovaline were toxic when tested with ribose, ribose or fructose, and ribose or galactose, respectively. In contrast, thialysine and thiaisoleucine inhibited C. acremonium with glucose, fructose, galactose, sucrose, mannitol, sorbitol, and soluble starch. Neither of these analogues was toxic at levels tested when glycerol was used as a carbon source. The minimal inhibitory concentrations (MIC) of thialysine, homoserine, and alpha-methylserine were greater than 1000, greater than 1000, and 250 microgram/mL, respectively, with glycerol. In contrast, the MIC values for the same three analogues were 31, 62, and 125 microgram/mL, respectively, with mannitol. The matching of the carbon sources with the specific amino acid analogues expands the number of analogues useful for selecting derepressed mutants. Thialysine-resistant mutants (tlysR) of C. acremonium which excrete lysine were isolated on a medium containing mannitol.

Effect of methionine on cephalosporin C and penicillin N production by a mutant of Cephalosporium acremonium

A mutant with enhanced potential to utilize sulfate for cephalosporin C production was isolated from a strain of Cephalosporium acremonium. The mutant displayed potency levels more than twofold that of the parent in the presence of sulfate but its productivity was severely inhibited by more than 0.5% of methionine which gave high cephalosporin C production with the parent. In a complex medium norleucine stimulated cephalosporin C production by the mutant in the presence of sulfate, whereas it showed no effect on the parent. In an incubation system with sulfur-starved cells of the mutant, L-methionine, but not the D-isomer, gave lower cephalosporin C production and a delayed production of penicillin N. However, it exhibited a stimulatory effect in the presence of valine or alpha-aminoadipic acid, the constituent amino acids of the antibiotic. Norleucine showed a similar effect to that of L-methionine in the presence of sulfate. On the basis of these results, characteristics of the mutant are discussed in connection with the effect of methionine.

Hydrogen peroxide sterilization of hydrophilic contact lenses

A new, simple, and effective procedure for the sterilization of soft contact lenses utilizes hydrogen peroxide, an inexpensive and readily availiable solution.

Behaviour of alpha-aminoadipylcysteine and glutamylcysteine in the presence of intact and disrupted mycelium of a Cephalosporium sp

1. delta-(l-alpha-Aminoadipyl)-l-cysteine, the corresponding d- and dl-alpha-aminoadipyl isomers, delta-(dl-alpha-amino[6-(14)C]adipyl)-l-cysteine and gamma- and alpha-l-glutamyl-l-cysteine were synthesized. 2. The behaviour of delta-(l-aminoadipyl)-l-cysteine and the corresponding d- and dl-alpha-aminoadipyl isomers was studied in the presence of suspensions of intact mycelium of a Cephalosporium sp., suspensions treated ultrasonically and extracts obtained by grinding with alumina. 3. With intact mycelium the l-alpha-aminoadipyl isomer was removed more rapidly from the extracellular fluid than the corresponding d-isomer. 4. Addition of delta-(dl-alpha-amino[6-(14)C]adipyl)-l-cysteine to suspensions of intact mycelium led to the labelling of extracellular and intracellular penicillin N and cephalosporin C, but also to extensive hydrolysis of the dipeptide. 5. Broken-cell systems hydrolysed delta-(l-alpha-aminoadipyl)-l-cysteine and the corresponding d-alpha-aminoadipyl isomer, but the former was hydrolysed more readily than the latter. 6. gamma- and alpha-l-Glutamyl-l-cysteine were also hydrolysed but delta-(l-alpha-aminoadipyl)-l-cysteinyl-l-valine was not. 7. Only part of the enzyme activity in broken-cell systems responsible for the hydrolysis of delta-(alpha-aminoadipyl)-l-cysteine was present in the supernatant obtained on centrifugation at 20000g. 8. Possible implications of these findings are discussed.