Gene expression profiles and intracellular contents of stress protectants in Saccharomyces cerevisiae under ethanol and sorbitol stresses
The bacterial population of the flocs in different types of activated sludge was investigated; about t00 strains per sludge sample were isolated from high dilution count plates and their morphological and physiological characteristics were determined. The predominant flora of activated sludge grown in domestic waste water in the Zeist purification plant or in a laboratory apparatus consisted of aerobic gram-negative non-sporeforming rods of the family Achromobacteraceae (genera Alcatigenes, Flavobacterium and Achromobacter). In activated sludge grown in synthetic waste water (mineral salts, glucose, and ammonium sulphate) about one-half of the isolated bacterial strains belonged to the Achromobacteraceae while the other half consisted of Micrococcaceae and of large ovoid encapsulated bacteria as yet unclassified. The same types of activated sludge were used for metabolic investigations together with washed suspensions of pure bacterial cultures isolated from domestic sludge. The poor utilization of sugars by sludge and washed cultures of bacteria grown in sewage or in media devoid of sugars might be explained by the assumption that adaptation to sugar break-down had not occurred. When nitrogen compounds, particularly amino acids, were supplied along with glucose to non-adapted sludge or bacterial suspensions, a ready adaptation to glucose break-down occurred. Adaptation of existing ceils as well as selection of bacterial strains capable of consuming glucose were found to be responsible for substrate adaptation when the sludge had been grown on sugar-containing media. Dissimilation of 10-20% of the consumed glucose and of 30-40 ~ of the consumed acetate was found in activated sludge supplied with these substrates. Washed suspensions of bacterial strains behaved similarly, though dissimilation percentages for glucose were higher. It is concluded that glucose consumption by the bacterial cells of the sludge flocs rather than diffusion of the glucose molecules into the sludge is the limiting factor in substrate removal. Further, the enzymatic decomposition of glucose in the bacterial cells rather than glucose uptake is rate-limiting in the removal of glucose by activated sludge.