Impact of the first Streptomyces genome sequence on the discovery and production of bioactive substances

An important addition to the field of bacterial genomics is the recent publication of the complete genome sequence of Streptomyces coelicolor. This strain has been for some decades the model organism for streptomycetes and other filamentous actinomycetes, Gram-positive bacteria highly valuable for their ability to produce thousands of bioactive metabolites, many of which have found important applications in medicine and agriculture. We discuss here the impacts that the S. coelicolor genome sequence is likely to have on the production of bioactive metabolites by current industrial strains, on the possible development of future superhost(s) for the production of valuable drugs, and on the search for new bioactive substances from microbial sources.

Biosynthesis of the thiazolylpeptide antibiotic GE2270

The biosynthesis of the antibiotic GE2270 in the producing microorganism Planobispora rosea was investigated by adding labelled amino acid precursors. Efficient incorporation of glycine and serine was observed, leading to specific enrichments of selected positions of the thiazole, oxazoline and pyridine rings. Furthermore, efficient enrichment of the C-, N- and O-methyl groups was detected. These results indicate that GE2270 is made through a biosynthetic route similar to that determined for other thiazolylpeptides. At the same time, the result point to an efficient route for the conversion of glycine into serine and methyl equivalents in Planobispora rosea.

[Hilar localization of splenic cyst does not always exclude the possibility of resective treatment]

Non parasitic cysts of the spleen require surgical treatment because of their progressive growth and in order to prevent the potential severe complications associated with such cysts. Since it is now well known that total splenectomy, especially in young patients, has potential for short- and long-term complications, much emphasis has been placed on splenic salvage, suggesting partial splenectomy as procedure of choice for splenic cysts. However various Authors suggest that many but not all splenic cysts can be treated with partial splenectomy. In particular cystic mass arising from the anterior aspect of the hilum near to vascular peduncle contraindicate partial resection requiring splenectomy. In a case observed TC scan demonstrated a very large epidermoid cyst penetrating hilar parenchyma just above splenic vessels insertion. Preoperative imaging suggested splenectomy as the only possible procedure to remove the cyst. At operation the exposure of the splenic artery extended proximally along the pancreatic tail showed an arterial branch running with satellite vein in the splenopancreatic ligament for inferior segment of the spleen. As we found this branch it was possible to resect cyst preserving a large inferior parenchymal segment normally perfused and functioning at postoperative scintigraphic controls. In conclusion not all hilar cysts must be considered an absolute indication to splenectomy. An accurate and extensive exposure of splenic artery and vein can demonstrate vascular anatomical variations permitting resection also for large cysts located near the splenic hilum.

Time course of changes in pancreatic enzymes, isoenzymes and, isoforms in serum after endoscopic retrograde cholangiopancreatography

Kinetics of the catalytic activities of total amylase (AMY; EC 3.2.1.1), pancreatic (P)-AMY isoenzyme, P2 and P3 isoforms, and pancreatic lipase (LPS; EC 3.1.1.3), and of the mass concentration of LPS in serum were studied in 10 patients who underwent endoscopic retrograde cholangiopancreatography (ERCP) and showed a distinct pancreatic injury. The temporal characteristics of enzyme changes described were (a) the maximal rate (Ka) at which enzymes are released into blood, (b) the time lag from ERCP until maximum concentration value, (c) the peak value of each serum enzyme, and (d) the rate (Kd) at which each enzyme is cleared from serum. LPS activity and mass concentrations increased and decreased faster than AMY and isoamylases, and the time of the LPS peak tended to be earlier than that of the other enzymes, but not significantly. The average peak increase of LPS values was higher than that of total AMY, P-AMY, and P2 isoform (P less than 0.001). The P-AMY time-activity curve was a composite of curves attributable to its isoforms; the isoforms increased and peaked sequentially, with P3 returning to normal more slowly than did P2. LPS mass and activity concentrations showed excellent parallelism, with no important differences. At 50 h after ERCP, only LPS values still exceeded the upper reference limit, returning to normal 70 h after the examination.

Time course of changes in pancreatic enzymes, isoenzymes and, isoforms in serum after endoscopic retrograde cholangiopancreatography

Kinetics of the catalytic activities of total amylase (AMY; EC 3.2.1.1), pancreatic (P)-AMY isoenzyme, P2 and P3 isoforms, and pancreatic lipase (LPS; EC 3.1.1.3), and of the mass concentration of LPS in serum were studied in 10 patients who underwent endoscopic retrograde cholangiopancreatography (ERCP) and showed a distinct pancreatic injury. The temporal characteristics of enzyme changes described were (a) the maximal rate (Ka) at which enzymes are released into blood, (b) the time lag from ERCP until maximum concentration value, (c) the peak value of each serum enzyme, and (d) the rate (Kd) at which each enzyme is cleared from serum. LPS activity and mass concentrations increased and decreased faster than AMY and isoamylases, and the time of the LPS peak tended to be earlier than that of the other enzymes, but not significantly. The average peak increase of LPS values was higher than that of total AMY, P-AMY, and P2 isoform (P less than 0.001). The P-AMY time-activity curve was a composite of curves attributable to its isoforms; the isoforms increased and peaked sequentially, with P3 returning to normal more slowly than did P2. LPS mass and activity concentrations showed excellent parallelism, with no important differences. At 50 h after ERCP, only LPS values still exceeded the upper reference limit, returning to normal 70 h after the examination.

DL 111, a new non-hormonal antifertility agent: contragestational and kinetic profile in baboons

It was previously shown that 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4 triazole (DL 111) given parenterally in single or multiple doses during the early stage of embryonal development terminates pregnancy in the mouse, the hamster, the rat, the rabbit and the dog. In the present work, the studies have been extended to the baboon. In this sub-human primate, single and/or multiple intramuscular injections of the compound terminated pregnancy when given between day 34 and 54 of gestation. The effectiveness of DL 111 was greater when earlier in gestation and the optimal mode of treatment appears to be a multiple one. DL 111 appears to act by a direct action on the conceptus, with consequent suppression of the endocrine function of the placenta, progesterone withdrawal and abortion. In all the baboons that aborted, the menstrual cycles resumed within a reasonable length of time and subsequent cycles were regular. All the animals that did not abort have given birth to normal and health term infants. Fertility appears to be unimpaired and the progeny resulting form these pregnancies did not show any abnormalities. No significant drug-related side-effects or alterations in plasma enzymes or haematological parameters were observed. Pharmacokinetic and activity relationships strongly suggest that sustained exposure of the conceptus to the drug action is indispensable for optimizing the pregnancy-terminating effect.

A new non-hormonal pregnancy-terminating agent

DL 111-IT, 3-(2-ethylphenyl)-5-(3-methoxyphenyl)-1H-1,2,4 triazole, a compound belonging to a new class of non-hormonal antifertility agents, when given subcutaneously, intramuscularly, intravaginally or orally terminates pregnancy in the rat, the mouse, the hamster and the dog. Time-course and dose-activity studies indicate that its effectiveness is dependent on dose, vehicle, route and time of pregnancy. DL 111-IT has no pre-implantation activity. The most effective time for treatment is the early post-implantation period. The compound has an antifertility effect through a slow and continuing action that results in the degeneration and subsequent resorption or expulsion of conceptuses. As a result, there must be sustained availability of active principle to arrest the pregnancy. Administered parenterally in a proper vehicle (oily) and with a suitable schedule of treatment (x 2-5 days), it demonstrates a very high pregnancy terminating activity (ED50: 0.04-0.7 mg/kg/day). Multiple intravaginal and oral administrations are also effective but the daily doses required are 10-20 and 40-100 times higher than the parenteral ones. Studies of the mechanism of action indicate that the site of action is the utero-placental complex. In fact, in pregnant rats, mice, hamsters and dogs, both plasma progesterone levels and the ineffectiveness of progesterone therapy rule out luteolysis as a basis for the activity. Moreover in hypophysectomized, ovariectomized animals whose pregnancies were maintained with proper hormonal treatments, DL 111-IT terminates pregnancy and adrenalectomy does not prevent its effect, which suggests that pituitary, ovaries and adrenals are not required for the antifertility action.

Rifamycin R, a novel metabolite from a mutant of Nocardia mediterranea

Rifamycin R is a novel ansamycin produced by a mutant of Nocardia mediterranea; both physical and chemical data indicate that it is 30-demethyl-30-hydroxymethyl rifamycin S.

Synthesis and biological activity of two metabolites of 1-methyl-5-(1-methylethyl)-2-nitro-1 H-imidazole, an antiprotozoal agent

5-(-Hydroxyl-1-methylethyl-)-1-methyl-2-nitro-1 H-imidazole (6) and 5-(1,2-dihydroxyl-1-methylethyl)-1-methyl-2-nitro-1 H-imidazole (9) are the principal metabolites found in urines of animals (mice, rats, and dogs) treated with 1-methyl-5-(1-methylethyl)-2-nitro-1 H-imidazole (1), an effective antitrichomonas agent. These two metabolites have been synthesized. Compound 6 was found to be less toxic than the parent compound 1 and to possess essentially the same activity against Trichomonas vaginalis in experimental infections. Compound 9 showed a low degree of in vivo activity.

Ansamycin biogenesis: studies on a novel rifamycin isolated from a mutant strain of Nocardia mediterranei

A novel ansamycin, rifamycin W, was isolated from a mutant strain of Nocardia mediterranei. The metabolic origin of rifamycin W was studied by (13)C nuclear magnetic resonance spectroscopy. Examination of the proton-decoupled pulse and Fourier transform (13)C spectra of rifamycin W biogenetically enriched with [1-(13)C]-, [2-(13)C]-, and [3-(13)C]propionate and with [1-(13)C]acetate has revealed that the alignment of acetate and propionate units corresponds to that previously proposed for rifamycin S. Washed mycelium from a rifamycin B-producing strain of N. mediterranei transformed rifamycin W into rifamycin B. We suggest that rifamycin W is a normal intermediate in the biosynthesis of the other rifamycins. These results, together with the structural similarity of rifamycin W to the streptovaricins, reinforce our hypothesis that a common progenitor is involved in the biogenesis of all naphthalenic ansamycins.

Relationships between bactericidal effect and inhibition of ribonucleic acid nucleotidyltransferase by rifampicin in Escherichia coli K-12

The mechanism of action of rifampicin, an antibiotic which inhibits in vitro the polycondensation of ribonucleotides by ribonucleic acid (RNA) nucleotidyltransferase, was studied in vivo in Escherichia coli. It is argued that the inhibition of RNA nucleotidyltransferase represents the primary lesion and is responsible for the bactericidal effect. This conclusion is based on (i) the correlation between concentrations of the antibiotic which block in vivo incorporation of labeled uracil and the bactericidal concentrations, (ii) the evidence that the loss of viability of the cells immediately follows the block of RNA synthesis, and (iii) the observation that the reversal of the inhibition of RNA synthesis goes together with a reversal of the loss of viability.