Use of sulfite resistance in Saccharomyces cerevisiae as a dominant selectable marker

Two S. cerevisiae genes were found to exhibit dominant phenotypes useful for selecting transformants of industrial and laboratory strains of S. cerevisiae. FZF1-4, which confers sulfite resistance, was originally isolated and identified as RSU1-4, but the two genes are shown here to be allelic. Cysteine 57 in wild-type Fzf1p was found to be replaced by tyrosine in Fzf1-4p. Multicopy SSU1, which also confers sulfite resistance, was found to be somewhat less efficient. In both cases, a period of outgrowth in non-selective medium following transformation was found to be necessary. The number of transformants obtained was found to be strain-dependent, and also to depend on the sulfite concentration used during selection. Undesirable background growth of non-transformants was not observed at cell densities as high as 2.5 x 10(7)/plate. In two ura3 laboratory strains where selection for URA3 was applied independently of that for sulfite, the transformation efficiency for sulfite resistance was about 50% that for uracil prototrophy.

Polyhydroxyalkanoates degradation affects survival of Pseudomonas oleovorans in river water microcosms

Bacterial survival in natural environments involves the ability of scavenging nutrients and energy sources. Polyhydroxyalkanoates (PHAs) are intracellular polymers that endow bacteria with enhanced survival capabilities in adverse environmental conditions. In this paper we compared survival of Pseudomonas oleovorans wild type and PHA depolymerase mutant strains in natural river waters by using microcosms. Experiments were performed with water samples collected from the Rio de la Plata. The survival of the P. oleovorans strain capable of degrading PHA was higher in raw river water compared to the depolymerase negative mutant strain. Bacterial numbers decreased during the experiment. At the end of the experiment, the difference in the number of cells between wild type and mutant strains was of 3 orders of magnitude. Mutants deficient in PHA degradation are useful to study the importance of reserve polymers in the survival of bacterial species in natural environments. They could also provide an adequate system for the analysis of the role of PHA in the tolerance to physical or chemical stress agents.

Potential impact of linking an emergency department and hospital-affiliated clinics to immunize pre-school-age children

OBJECTIVE

To determine whether the use of an urban pediatric emergency department (ED) to immunize pre-school-age children would result in an improvement in the percentage fully vaccinated by the end of the second year of life.

DESIGN

A retrospective cohort study of two groups: (1) 100 consecutive children (ED group) enrolled at one of two hospital-affiliated primary care clinics were chosen from the ED patient logs if their second birthday occurred in the 12 months prior to November 1990; and (2) 91 age-matched control children (control group) were chosen at random from the same hospital-affiliated clinics' enrollment logs without regard to ED use. The health care provided during the first 2 years of life for each group was compared.

RESULTS

The mean number of visits to the ED in the first 2 years of life by the ED group was significantly greater than that of the control group (2.9 [SD] +/- 2.5 vs 1.1 +/- 1.4; P < .001) during the first 2 years of life. In 67% of ED visits, children would have been well enough to receive a vaccination. Both groups had similar types and numbers of visits to the primary clinics. For example, the ED group had 10 +/- 5 visits by age 2 years compared with the control group, which had 9 +/- 4 visits. There was no significant difference in actual immunization percentages achieved in the clinic, with 62% of the ED group having received four diphtheria, pertussis, and tetanus vaccinations; three oral poliovirus vaccinations; and one measles, mumps, and rubella vaccination by age 2 compared with 69% of control children. There were more missed vaccination opportunities during clinic visits in the ED group (7.4 vs 4.6 per 100 clinic visits; P < .01). If immunizations were offered in the ED to those children who needed them, immunization percentages would have been increased an average of 20% compared with percentages achieved in the clinic alone.

CONCLUSION

Routine vaccinations in the ED would significantly increase immunization percentages in children enrolled in two hospital-affiliated clinics. Close linkage and coordination between the ED and hospital-affiliated clinics may improve preventive health care in urban children who use EDs.