Developing an ELISA using serotype-specific antigens from selected pneumococcal strains of own selection.

Streptococcus pneumoniae (pneumococcus) is a significant cause of morbidity and mortality in infants and elderly people. Pneumococcal strains possess a polysaccharide capsule, and 90 different serotypes have been identified. The pneumococcal ELISA suggested by World Health Organization (WHO) guidelines is based on capsular serotypes included in the 23-valent polysaccharide vaccine (Pneumovax((R))). Pneumococcal antigens were developed and applied in an ELISA, which elicited a low baseline cross-reaction with the common cell wall polysaccharide (C-Ps). The aim of this study was to develop an ELISA using type-specific antigens from S. pneumoniae strains with serotypes of own selection in order to quantify type-specific pneumococcal antibodies in human serum.

Kinetic analysis of a trehalase-overexpressing strain grown on trehalose: a new tool for respiro-fermentative transition studies in Saccharomyces cerevisiae.

AIMS: The aim was to demonstrate the use of a trehalase-overexpressing Saccharomyces cerevisiae strain grown on trehalose as a valuable tool in the studies of respiro-fermentative transition at a reduced scale. METHODS AND RESULTS: A trehalase-overexpressing strain was cultivated in synthetic medium on trehalose under aerobic conditions. This strain grew at a maximum specific growth rate of 0.16 h(-1) and showed a pure oxidative metabolism. Glucose pulse experiments were carried out in this system in order to quantify the short-term Crabtree effect. These data were then compared with glucose pulse experiments carried out in the conventional way with the wild-type strain in glucose-limited chemostats. Glucose-pulse experiments in aerobic batch cultures grown on trehalose led to a metabolic respiro-fermentative transition similar to the one observed in glucose-limited chemostats. CONCLUSIONS: This cultivation system allowed us to quantitatively mimic at the flask scale the Crabtree effect observed in conventional chemostat studies. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is of primary interest in S. cerevisiae studies in which: (i) the implementation of oxidative growth is required (as with studies of the Crabtree effect and heterologous protein production); (ii) small-scale culture systems are required (e.g. high-throughput mutant screening and isotopic labelling experiments).