Mutagenic action of acenaphthene on haploid and diploid cultures of Candida scottii

Acenaphthene used as vapour increases the frequency of morphological mutations as well as mutations yielding strains with a reduced activity of respiration in Candida scottii. The diploid culture has more mutants than the haploid culture. The frequency of mutants depends on the duration of acenaphthene action. Cells more resistant to the action of acenaphthene vapour are selected in the haploid culture when C. scottii cells are transferred many times into new wort drops. As a result, the frequency of mutations decreases. When the diploid culture is exposed to the action of acenaphthene vapour for a longer time, the frequency of mutations rises. Apparently, the diploid culture has a lower activity of reparation of premutational damages than the haploid culture and therefore the number of mutant cells increases.     

Growth of Streptococcus pyogenes and streptolysin O production in complex and synthetic media

A comparative study of the growth of a highly haemolytic group A streptococcal strain in Trypticase-yeast extract medium and in a chemically defined medium was undertaken. Appreciable growth was obtained in the latter medium with the release of significant amounts (120 haemolytic units) of streptolysin O. This indicates that toxinogenic factors present only in the peptones of complex media are not essential for biosynthesis and release of this cytolytic toxin, as is the case for many bacterial toxins. NADase was also released in the synthetic medium. Bacterial cell mass, growth rate, and streptolysin O production were threefold higher in the complex medium. The effects of various carbohydrates on streptolysin O production in complex medium are investigated. No repression of toxin formation by glucose was observed. The relationship between growth and toxinogenesis in streptococci and in other toxinogenic bacteria is discussed.     

Growth and protopectinase production of Geotrichum klebahnii in batch and continuous cultures with synthetic media

Geotrichum klebahnii ATCC 42397 produces a protopectinase (PPase-SE) with polygalacturonase (PGase) activity. The microorganism was aerobically cultivated in synthetic media. Glucose, fructose and xylose yielded the highest enzyme levels (10–11 PGase units ml⁻¹). Galacturonic acid repressed enzyme production and no growth was obtained with disaccharides and pectin. Specific enzyme activity obtained in an O₂-limited culture was similar to that found in nonlimited ones. A growth yield (Y _x/s) of 0.49 g of cell dry weight per gram of glucose consumed was obtained in a typical batch bioreactor culture. Enzyme production was growth associated, and no major products other than biomass and CO₂ were detected. The volumetric enzyme activity reached a maximum around D=0.3–0.4 h⁻¹ in glucose-limited continuous cultures. However, it varied strongly (together with microorganism morphology) even after retention times ≥8 at any D tested (0.035–0.44 h⁻¹) though the rest of the culture variables remained fairly constant. No correlation between morphology and enzyme activity could be obtained. Enzyme production was poor in urea- and vitamin-limited continuous cultures. In all cases, biomass and CO₂ accounted for ≅100% of carbon recovery though Y _x/s values were different. Journal of Industrial Microbiology & Biotechnology (2000) 25, 260–265. Received 20 April 2000/ Accepted in revised form 15 September 2000     

Growth of Candida albicans in dexamethasone-supplemented media

Candida albicans grown in dexamethasone (DXM) shows an apparent increase in dry weight. This increase, however, represents an artefact due to entrapment and incorporation of DXM by the yeast. Thus opportunistic infections by C. albicans which are promoted by DXM must be due entirely to effects other than growth enhancement of the organism.