The Frequency of Survivorship in Heterozygous Diploids of Cdc13-1exo1Δ Mutants of S. cerevisiae Is One Survivor Cell in 72 Cells/Generation at 36°C

Telomeres cap ends of eukaryotic chromosomes prevent them from degradation and ensure genomic stability. Cdc13 is an essential telomere recruitment and maintenance protein. A temperature-sensitive point mutation in cdc13 gene leads to telomere impairment, giving rise to cdc13-1 mutants that suffer lethality at enhanced temperatures. Deleting Exo1 gene from these mutants, however, leads to the emergence of temperature-tolerant mutants called survivors. Yeasts are known to exist as either diploids or haploids. These yeast genotypes generate survivors. The frequency of survivorship in the haploid genotype is one cell in 104 cells/generation at 36°C, however, the frequency at which they emerge in their diploid counterparts at the same temperature is not known. In this study, we investigated the frequency of Survivorship in heterozygous diploids of cdc13-1exo1Δ mutants of S. cerevisiae at 36°C. Diploids were constructed by mating haploid strains of opposite mating type cdc13-1 exo1:LEU strains with strains of cdc13-1 exo1:HIS. The crosses were 1296 × 3181, 2561 × 3182, 1296 × 3182 and 2561 × 3181. Genetic markers and phenotypic appearance were considered while mating the mutant cells. Using a stick, a smear of one haploid strain was made on each YEPD plate labelled C2, C8, C9, D1, D14, and D15. A smear of another opposite mating type was made on the previous strain. They were mixed and allowed to mate overnight, before culturing on media lacking Luecine and Histidine (-L and -H). Survivors were generated by culturing these diploids at 36°C. Using SPSS 20.0 software for windows SPSS, 2011, the frequency was determined as one Survivor cell in 72 cells/generation, as their frequency of survivorship averaged 5.9 × 10-5 ± 0.04.

Investigating the Bioburden of “Neglected” Hospital Low Contact Surfaces

Microbes inhabit every surface, reproduce, and if undisturbed, could form biofilm. Hospital contact surfaces have been reported to play a major role in the spread of healthcare-acquired infections (HAIs). Most studies on these surfaces as a route for the spread of nosocomial infections have focused on the high-contact surfaces. There is a paucity of information on the bioburden of “neglected” low-contact surfaces such as bedside bible, ward television, and ward clock, etc. This study was carried out to investigate the bioburden of “neglected” low-contact hospital surfaces and compare it with that of the high-contact surfaces. Using a sterile swab stick moistened in normal saline, we collected 400 samples from contact surfaces of 20 randomly selected hospitals in Owerri, southeast in Nigeria, and by standard microbiological methods and with reference to standard identification manuals, microbial species were isolated and characterized. The results show that the mean of the bioburden in cfu/square swabbed surface of these “neglected” low-contact surfaces is significantly higher (p = 0.005) than that of the high-contact surfaces which may be a result of target hygienic cleaning, with attention on the high-contact surfaces and the low-contact surfaces are often “neglected”. This result gives an insight into the continued prevalence of hospital-acquired infections as these “neglected” low-contact surfaces continue to serve as a reservoir for pathogenic microbes and a source of continued microbial contamination of hospital surfaces. It therefore calls for a revamp of existing hospital cleaning protocols and redesigning of cleaning regimes.