Annales de microbiologie最新文献

The growth of C. obscurus was studied in solid and liquid media. In agar media, the hyphal growth was linear, but the number of apices increased exponentially; total growth was consequently exponential but characterized by a low growth rate. In batch cultures in a fermenter, mycelial growth was continuously linear following a short exponential phase. The absence of branching induced a linear development of the fungus in liquid culture. Fermentation balances showed that the linear growth could not result from the presence of a specific inhibitor, nor from the existence of a limiting concentration of a nutrient in the medium. Hypotheses concerning the non-branching of the fungus in liquid culture are discussed.

Two spiroplasma strains (B31 and B39) recovered from diseased honey-bees (Apis mellifera) in southwestern France were similar in biochemical, serological and pathological properties. The organisms grew at 30 degrees C, required cholesterol for growth, fermented glucose, catabolized arginine and produced a film and spot reaction. The two spiroplasmas were serologically indistinguishable but were related to serogroup IV spiroplasmas, which had been previously isolated from flower surfaces and from insects. The isolates were distinct from the three previously established species of Spiroplasma and from other presently known serogroups. The G + C content of the DNA from strain B31 was 30 +/- 1 mol %. Both B31 and B39 strains were associated with a lethal infection ("May disease") of the honey-bee. On the basis of the characterization presented here, it is proposed that these spiroplasmal pathogens of bees and allied strains be classified as a new species, Spiroplasma apis, the type strain of which is B31 (ATCC 33834).

Tests were carried out to determine the effects of commercial preparations of indole-3-acetic acid (IAA), gibberellin (GA) and kinetin, separately and in combination, on Azospirillum lipoferum and A. brasilense. These hormones showed no effect upon morphology, growth rate, or oxygen uptake. Some random effects of GA, kinetin and the combination of hormones--but not of IAA alone--were observed on the number of viable cells. IAA, in the concentrations 0.001-1.0 microgram/ml, inhibited nitrogenase in A. lipoferum but not in A. brasilense. GA and kinetin separately and in combination with IAA had no influence on nitrogenase activity.

Virulent isolates of Shigella dysenteriae and Shigella boydii harboured a 140 Mdal plasmid which was either absent or deleted in spontaneously avirulent strains. Together with previous data concerning S. sonnei, S. flexneri and enteroinvasive Escherichia coli, the present results established the general role of extrachromosomal elements in the virulence of such enteroinvasive species. Among different species, these virulence plasmids showed unrelated endonuclease cleavage patterns, whereas hybridization experiments showed that homologous sequences were present throughout the molecules. These plasmids may therefore have derived from a common ancestor molecule which overcame evolutionary alterations in restriction sites. Furthermore, intraspecies and intraserotype comparison of these plasmids by endonuclease cleavage demonstrated highly conserved sequences. The consequences of these data for evolution, epidemiology and diagnosis of Shigella and enteroinvasive E. coli are discussed.

Strains of S. typhimurium biotype 6 possess neither tetrathionate reductase nor arginine dihydrolase; they use trehalose, but not inositol and glycerol. Most are multi-resistant to antibiotics and are responsible for numerous outbreaks of salmonellosis. They have been divided into four groups. Groups I includes strains of phage type 207, and was predominant in Belgium from 1969 to 1976. Group II includes strains of a classical variety belonging to phage types 49, 193 and 204. Group III includes strains of the copenhagen variety belonging to the same phage types. Strains of groups II and III are generally resistant to trimethoprim. They have predominated in Belgium since 1978 (mainly phage type 193). Group IV contains a few strains of various phage types, generally non-resistant, which have caused no epidemics.

The antigenic structure of glyceraldehyde-3-phosphate dehydrogenase of the most representative Enterobacteriaceae species were compared with an antiserum to Escherichia coli glyceraldehyde-3-phosphate dehydrogenase. The results of the immunodiffusion experiments were confirmed and specified by micro-complement fixation studies. They demonstrated a total immunological identity between the E. coli enzyme and the enzymes of Alcalescens-dispar and the Shigella species, a marked relatedness of the Salmonella species enzyme and a more or less significant relation of the enzymes of the other Enterobacteriaceae species. Moreover, the micro-complement fixation had the same sensitivity and a better selectivity than the DNA/DNA hybridizations. The results show that, like DNA polymerase, this enzyme has evolved more slowly than the other enzymes studied at this time.

The oxidation rate in resting cells of Rhizobium meliloti was investigated with either glucose or fructose as substrate. Fructose uptake was found to be complete, whereas glucose uptake did not fully occur, yielding 2-kitogluconic acid in the medium. At the end of fructose oxidation, significant levels of this substrate and its derivatives had accumulated in the bacteria.

We described the lysogeny among new species of Yersinia: Y. frederiksenii (47 strains), Y. kristensenii (57 strains) and Y. intermedia (133 strains). We found that 6.3% of the strains of Y. frederiksenii, 3.5% of Y. kristensenii and 2.2% of Y. intermedia were lysogenic for bacteriophages active on Y. enterocolitica (mainly the phenotypes incriminated in human pathology) and less frequently lysogenic for some strains of Y. frederiksenii, Y. kristensenii and Y. intermedia. One bacteriophage, isolated from the strain Y. frederiksenii 7291, should allow to discriminate between Y. enterocolitica phagovar IXa (susceptible) and IXb (resistant), and between the strains of Y. enterocolitica belonging to phagovar Xz and serovar 5 either biovar 1 (sometimes susceptible) or biovar 3 (always resistant).

The method described allowed a rapid, easy and reliable detection of exfoliative toxin produced by Staphylococcus aureus. A new culture technique of S. aureus strains and the detection of exfoliative toxin by electrosyneresis are described. This could replace the new-born mouse test. Such a method was useful for epidemiological studies because a lot of strains of S. aureus could be screened for exfoliative toxin production; thus the serotype of the toxin (ETA or ETB) was also determined.

Two sets of mice just weaned (germ-free or conventional) were fed ad libitum with three different diets: a 5% lactose solution, yogurt at a 3/5 dilution in this lactose solution, and heated yogurt at the same dilution in the same solution. Total lactase activity (TA) and specific lactase activity (SA) of the small intestine were measured after 14, 28 and 42 days of these diets. The results led to the following conclusions. 1) TA and SA were always significantly greater in germ-free and gnotobiotic animals than in conventional ones, whatever the diets and age of the animals. 2) TA and SA were significantly greater at the three times of measurement in the gnotobiotic and conventional animals fed with unheated yogurt than in the animals fed with heated yogurt. The 5% lactose solution gave intermediate results. 3) In conventional and gnotobiotic animals fed with yogurt, TA increased with time compared to the initial value at weaning. With the two other diets, TA remained constant or decreased. With yogurt, SA varied only weakly with time compared to weaning values, when it decreased in greater proportions with the two other diets.