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Biomedical subjects

F Besson

Publications and source records attributed to F Besson.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1987

Isolation and characterization of new iturins: iturin D and iturin E.

Two new antibiotics, iturin D and iturin E, were isolated from a strain of Bacillus subtilis producing iturin A. These compounds belong to the iturin group, the acid hydrolysates contained alpha-amino acids Asp3, Glu1, Pro1, Ser1, Tyr1, and a mixture of n-C14, iso-C15, anteiso-C15, iso-C16 and n-C16 beta-amino acids. They differ from iturin A by the presence of a free carboxyl group in iturin D and a carboxymethyl group in iturin E.

Antifungal Agents↗
PubMed1986

Effect of various growth conditions on spore formation and bacillomycin L production in Bacillus subtilis.

Bacillomycin L is produced by Bacillus subtilis NCIB 8872 in the stationary phase; it is excreted into the culture medium, without prior accumulation in the bacterial cells. The production of bacillomycin L is largely dependent on the composition of the culture medium. The action of specific inhibitors of sporulation, netropsin and diethyl malonate, on antibiotic synthesis is dependent on the composition of the culture medium. Although they occurred at the same time, there appears to be no direct correlation between sporulation and antibiotic synthesis.

Bacillus subtilis↗
PubMed1984

Action of antifungal peptidolipids from Bacillus subtilis on the cell membrane of Saccharomyces cerevisiae.

Iturin A and bacillomycin L, antibiotics of the iturin group inhibit the growth of Saccharomyces cerevisiae and the lethal doses were respectively 10 and 60 micrograms/ml. Both antibiotics had an effect on the incorporation of radioactive precursors into macromolecules which decreased with increasing concentrations of antibiotics. However, no specificity was observed on the various macromolecules, proteins, ribonucleic acids and polysaccharides. The site of action on yeast cells was demonstrated to be the cytoplasmic membrane: both antibiotics of iturin group lysed spheroplasts of S. cerevisiae. Moreover, a rapid leakage of potassium ions occurred in the presence of the antibiotics; this leakage was directly associated to the killing effect. These results are consistent with a disruption of the structural integrity of the cytoplasmic membrane correlated to the loss of viability of the yeast cells.

Anti-Bacterial Agents↗
PubMed1984

Action of the antibiotics of the iturin group on artificial membranes.

The action of iturin A and bacillomycin L on vesicles of dipalmitoylphosphatidylcholine (DPPC) and DPPC-cholesterol was studied. Iturin A destroyed the vesicles, bacillomycin L bound with DPPC vesicles and destroyed vesicles containing DPPC and cholesterol. These results are discussed in comparison with the action of antibiotics of the iturin group on cytoplasmic membranes.

Anti-Bacterial Agents↗
PubMed1982

Action of peptidolipidic antibiotics of the iturin group on erythrocytes. Effect of some lipids on hemolysis.

Iturin A, bacillomycin L and bacillomycin L dimethyl ester have a strong lytic activity upon human erythrocytes while iturin C is totally inactive. The hemolytic action of the antibiotics is inhibited by free cholesterol as well as by cholesterol included in mixed liposomes of phosphatidylcholine-cholesterol and to a lesser extent by phosphatidylcholine liposomes. This inhibition is the result of an interaction between the antibiotic and added lipids which diminishes the concentration of free antibiotic available to lyse erythrocytes. The inhibitory effect of liposomes on hemolysis demonstrated the affinity of the antibiotic for artificial membrane, especially those containing cholesterol.

Anti-Bacterial Agents↗
PubMed1981

Structure of bacillomycin D, a new antibiotic of the iturin group.

Bacillomycin D is an antifungal agent extracted from the culture medium of a strain of Bacillus subtilis. It is a mixture of two homologous lipopeptides: the lipid moiety consists of 3-amino-12-methyltridecanoic acid or 3-amino-12-methyltetradecanoic acid; the peptide moiety contains one residue of each of the following seven amino acid: D-asparagine, L-aspartate, L-glutamate, L-proline, D-serine, L-threonine and D- tyrosine. The peptide sequence and the cyclic structure were determined by structural analysis of the peptides obtained by mild acid hydrolysis and by cleavage of the molecule with N-bromosuccinimide.

Amino Acids↗