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Biomedical subjects

F Besson

Publications and source records attributed to F Besson.

At least 19 recordsLinked to original sources
PubMed1992

Biosynthesis of bacillomycin D by Bacillus subtilis. Evidence for amino acid-activating enzymes by the use of affinity chromatography.

Bacillomycin D is an antifungal lipopeptide produced by B. subtilis. The formation of the peptidyl bonds of bacillomycin D occurs non-ribosomally, as demonstrated by the use of chloramphenicol, an inhibitor of protein biosynthesis. Amino acid-activating enzymes were found in B. subtilis cell lysates purified by affinity chromatography on a gel containing L-Pro, an amino acid of bacillomycin D. Presence of ATP during this purification increases the binding of enzymatic proteins and their activity. An enzyme, with an apparent molecular weight of 230 kDa, catalyzed ATP-PPi exchange reactions, which were mediated by specific amino acids, corresponding to a partial sequence of bacillomycin D.

Adenosine Triphosphate↗
PubMed1992

Synthesis of beta-hydroxy fatty acids and beta-amino fatty acids by the strains of Bacillus subtilis producing iturinic antibiotics.

The iturinic antibiotics, which contain long chain beta-amino acids, are produced by Bacillus subtilis. Screening these strains for the presence of a possible precursor of the iturinic antibiotics, we isolated a lipopeptide containing beta-hydroxy fatty acids. The structure of this compound was studied and it appears to be identical or structurally very similar to surfactin. The carbon chain of its beta-hydroxy fatty acids was n C16, iso C16, iso C15 or anteiso C15. The percentages of each beta-hydroxy fatty acids varied according to the strain producing iturinic antibiotics and were influenced by addition of branched-chain alpha-amino acids to the culture medium. These results demonstrate for the first time that iso C14 beta-hydroxy fatty acid is a constituent present in such a surfactin like lipopeptide. Besides, the presence of radioactive beta-hydroxy fatty acids in the phospholipids when the strains were grown in the presence of sodium [14C]acetate seems also characterize the different strains producing iturinic antibiotics.

Amino Acid Sequence↗
PubMed1992

Phase I-II study of vinorelbine (Navelbine) plus cisplatin in advanced non-small cell lung cancer.

32 patients with advanced non-small cell lung cancer previously untreated by chemotherapy were included in a phase I-II study in order to determine the feasibility of the combination of vinorelbine and cisplatin, each administered at its optimal dose, i.e. 30 mg/m2 weekly and 120 mg/m2 every 4-6 weeks, respectively. There were 27 males and 5 females with a mean age of 55 years and a median performance status of 80%. 13 had locally advanced disease and 19 had distant metastases at the time of inclusion. Our study demonstrated the feasibility of this protocol. Dose intensities could be maximised by adapting vinorelbine doses rather than by postponing treatment in the event of neutropenia. Both response rate (33%) and overall survival of the population (median 11 months) justify further studies.

Adult↗
PubMed1991

Studies on the antifungal antibiotics: bacillomycin D and bacillomycin D methylester.

Bacillomycin D, an antifungal compound of Bacillus subtilis, was produced during the stationary phase of growth when all the glucose of the medium was exhausted and the pH reached about 8. In addition to bacillomycin D, bacillomycin D methylester was characterized by its antifungal properties and its haemolytic activity.

Anti-Bacterial Agents↗
PubMed1991

Influence of divalent ions on the solubility of iturin and bacillomycin L, antifungal peptidolipids of Bacillus subtilis.

When calcium chloride was added to the culture medium of strains producing iturin or bacillomycin L, the antibiotic, normally excreted in the supernatant of the culture medium, was found in the cell pellet. This apparent inhibition of the antibiotic excretion was studied and it was demonstrated that CaCl2 precipitated the antibiotic after its excretion in the medium. The ability of various chloride salts to precipitate iturin and bacillomycin L was tested and the most effective salts were CaCl2 and MnCl2. Comparison of the compounds obtained by CaCl2 precipitation and by acid precipitation showed that, in the latter case, major antibiotics were accompanied by minor congeners resulting from modifications of genuine antibiotics.

Amino Acid Sequence↗
PubMed1990

Studies on the biosynthesis of iturin, an antibiotic of Bacillus subtilis, and a lipopeptide containing beta-hydroxy fatty acids.

The biosynthesis of iturin, an antibiotic containing a beta-amino fatty acid, was studied by incubating Bacillus subtilis in the presence of various 14C-labelled precursors. Sodium acetate or palmitic acid were incorporated into the beta-amino acids of iturin. Among the alpha-amino acids (asparagine, glutamine, serine, proline and tyrosine) in the peptidic part of iturin, asparagine appears to be the best precursor. In the presence of sodium [14C]acetate or [14C]asparagine, there was a synthesis of radioactive compound (compound X) before the synthesis of radioactive iturin. Compound X contained asparagine and/or aspartic acid, glutamine and/or glutamic acid and beta-hydroxy fatty acids.

Acetates↗
PubMed1990

Specific inhibition of iturin biosynthesis by cerulenin.

Cerulenin, an inhibitor of fatty acid synthesis, inhibits the biosynthesis of iturin by Bacillus subtilis. With a cerulenin concentration of 2 micrograms/mL, 50% inhibition was achieved. At this concentration, cerulenin does not affect growth or total protein synthesis but does inhibit the incorporation of sodium [14C]acetate, [14C]myristic acid, and [14C]asparagine into iturin. Since cerulenin is known to block the condensation of malonyl-CoA subunits in the formation of fatty acids, the inhibition of iturin and beta-amino acid syntheses by cerulenin is discussed in relation with lipid synthesis.

Acetates↗
PubMed1990

Mycosubtilins B and C: minor antibiotics from mycosubtilin-producer Bacillus subtilis.

Mycosubtilins B and C were isolated from the culture medium of Bacillus subtilis. The acid hydrolysates of these new antifungal antibiotics, like mycosubtilin, contain alpha-amino acids (Asp3, Glu1, Pro1, Ser1 and Tyr1) and a mixture of iso-C16, n-C16, iso-C17 and anteiso-C17 beta-amino acids. Mycosubtilins B and C differ by the presence of a carboxyl group and of a carboxymethyl group, respectively, instead of a carboxamide group in previously described mycosubtilin.

Amino Acid Sequence↗
PubMed1989

Fatty acid and beta-amino acid syntheses in strains of Bacillus subtilis producing iturinic antibiotics.

Iturinic antibiotics, produced by different strains of Bacillus subtilis, contain long-chain beta-amino acids (beta-AA). The regulation of the synthesis of fatty acids (FA) and beta-AA was studied by modifying the culture medium. Addition of possible precursors, branched-chain alpha-amino acids, to the medium affected the FA and beta-AA compositions. According to this, the B. subtilis strains can be divided into two groups. The first contains the producers of mycosubtilin and bacillomycin F which synthesize a high level of iso C16 chains; the second contains the producers of bacillomycin D, bacillomycin L and iturin which synthesize a high level of n carbon chains. The incorporation of radioactive sodium acetate into FA and beta-AA showed rapid FA synthesis followed by a second synthetic step. Although the detailed mechanism has not yet been elucidated, this second step, corresponding to the beta-AA synthesis, seemed to be a key step in determining the alkyl chain of beta-AA.

Amino Acids↗
PubMed1989

Relationship between the 4 mmol running velocity, the time-distance relationship and the Léger-Boucher's test.

The relationship between distance and best time is roughly linear for distances between 1500 and 5000 m. The slope of this relationship has the dimension of a velocity (Vlim) which can be sustained during a long time. The individual time-distance relationships and the resulting Vlim have been studied in 32 subjects practicing different athletic activities by measuring exhaustion time for 2 to 4 constant-velocity running exercises performed to exhaustion. The velocity corresponding to 4 mmol.l-1 of blood lactate (V4 mmol) has been compared with Vlim. As maximal oxygen uptake is a major factor determining V4 mmol, Vlim and V4 mmol have also been correlated with the result of a field test which is assumed to measure maximal aerobic power (Léger-Boucher's test). This test consists in running until exhaustion at a velocity which increases every two minutes. The higher the velocity at exhaustion (Vléger) is, the higher the maximal oxygen uptake is assumed. Both Vlim and Vléger were very well correlated with V4 mmol (r greater than 0.90) and the average value of Vlim was almost equal to the average value of V4 mmol (13.89 vs 13.71 km.h-1). However, it was not possible to estimate V4 mmol accurately from the values of Vlim or Vléger because the standard errors of estimates were too large.

Exercise↗
PubMed1989

Action of mycosubtilin on erythrocytes and artificial membranes.

Mycosubtilin has a strong lytic action upon erythrocytes. The haemolytic effect of the antibiotic is inhibited by free cholesterol as well as cholesterol included in liposomes of phosphatidylcholine-cholesterol. The antibiotic binding on artificial membranes was studied with radioactive bilayer vesicles of dipalmitoylphosphatidylcholine (DPPC), and DPPC-cholesterol:mycosubtilin destroyed both kinds of vesicles. The inhibition of the haemolytic effect of mycosubtilin by liposomes is a result of an interaction which diminishes the concentration of free cholesterol.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Action of mycosubtilin, an antifungal antibiotic of Bacillus subtilis, on the cell membrane of Saccharomyces cerevisiae.

Mycosubtilin, an antibiotic of the iturin group, inhibits the growth of Saccharomyces cerevisiae by a fungicidal action. Increasing concentrations of mycosubtilin decrease the incorporation of radioactive precursors into proteins, RNA and polysaccharides without specificity. Yeast spheroplasts are lysed by mycosubtilin. Its action on the cytoplasmic membrane induces important modifications of the membrane permeability: nucleotides, proteins and lipids are released from the cells. These releases increase with increasing concentrations of mycosubtilin.

Antifungal Agents↗
PubMed1988

Studies on the biosynthesis of beta-amino acids, the lipid moiety of iturins A, in Bacillus subtilis.

The biosynthesis of the beta-amino acid components of iturins A was studied in comparison to the biosynthesis of fatty acids. Palmitic acid was incorporated into the lipid moiety of iturins A when it was added to the culture medium of the iturin producer Bacillus subtilis. Addition of unlabeled palmitic acid enhanced the formation of straight-chain beta-amino acids and addition of valine or leucine increased the production of branched beta-amino acids. These modifications correlated with modifications in the corresponding biosynthesized fatty acids.

Anti-Bacterial Agents↗
PubMed1988

Bacillomycins Fb and Fc: isolation and characterization.

Bacillomycins Fb and Fc, new antifungal antibiotics, were isolated from a strain of Bacillus subtilis producing bacillomycin F. Because of the presence of beta-amino acids, these compounds belong to the iturin group. The acid hydrolysates contained alpha-amino acids Asp3, Glu1, Pro1, Thr1, Tyr1 and a mixture of iso-C15, anteiso-C15, iso-C16, iso-C17 and anteiso-C17 beta-amino acids. The ratios of the different beta-amino acids depend on the nature of the culture medium. Bacillomycins Fb and Fc differ from bacillomycin F by the presence of free carboxyl groups.

Amino Acid Sequence↗
PubMed1987

Influence of the culture medium on the production of iturin A by Bacillus subtilis.

The production of iturin A by Bacillus subtilis was studied with respect to the composition of the culture medium. Increasing phosphate concentrations did not modify the antibiotic yield. Fructose, sucrose and mannitol were better carbon sources than glucose for antibiotic production. The nature of the nitrogen source was an important factor in the production of antibiotic. Among the amino acids which are components of iturin A, L-asparagine was the best substrate for the biosynthesis of iturin A; L-glutamine and L-serine were rather poor substrates while L-proline and D-tyrosine gave no antibiotic. Ammonium salts permitted good synthesis of antibiotic but the addition of calcium ions to the culture medium inhibited the excretion of antibiotic from the cells.

Amino Acids↗