Biomedical subjects

C Houseweart

Publications and source records attributed to C Houseweart.

3 recordsLinked to original sources

PubMed2001

Antibiotic susceptibility profiles of Escherichia coli strains lacking multidrug efflux pump genes.

The contribution of seven known and nine predicted genes or operons associated with multidrug resistance to the susceptibility of Escherichia coli W3110 was assessed for 20 different classes of antimicrobial compounds that include antibiotics, antiseptics, detergents, and dyes. Strains were constructed with deletions for genes in the major facilitator superfamily, the resistance nodulation-cell division family, the small multidrug resistance family, the ATP-binding cassette family, and outer membrane factors. The agar dilution MICs of 35 compounds were determined for strains with deletions for multidrug resistance (MDR) pumps. Deletions in acrAB or tolC resulted in increased susceptibilities to the majority of compounds tested. The remaining MDR pump gene deletions resulted in increased susceptibilities to far fewer compounds. The results identify which MDR pumps contribute to intrinsic resistance under the conditions tested and supply practical information useful for designing sensitive assay strains for cell-based screening of antibacterial compounds.

Anti-Infective Agents, Local↗

PubMed2001

Genetic footprinting in bacteria.

In vivo genetic footprinting was developed in the yeast Saccharomyces cerevisiae to simultaneously assess the importance of thousands of genes for the fitness of the cell under any growth condition. We have developed in vivo genetic footprinting for Escherichia coli, a model bacterium and pathogen. We further demonstrate the utility of this technology for rapidly discovering genes that affect the fitness of E. coli under a variety of growth conditions. The definitive features of this system include a conditionally regulated Tn10 transposase with relaxed sequence specificity and a conditionally regulated replicon for the vector containing the transposase and mini-Tn10 transposon with an outwardly oriented promoter. This system results in a high frequency of randomly distributed transposon insertions, eliminating the need for the selection of a population containing transposon insertions, stringent suppression of transposon mutagenesis, and few polar effects. Successful footprints have been achieved for most genes longer than 400 bp, including genes located in operons. In addition, the ability of recombinant proteins to complement mutagenized hosts has been evaluated by genetic footprinting using a bacteriophage lambda transposon delivery system.

Bacteriophage lambda↗

PubMed1996

Discrete transcripts encode multiple chitinase isoforms in Brugian microfilariae.

The blood-borne microfilariae of the Brugian nematodes produce multiple isoforms of chitinase, whose expression is coincident with the onset of microfilarial infectivity for mosquitoes. A single cDNA sequence was previously obtained by screening a Brugia malayi microfilarial cDNA library, yet two chitinase isozymes are readily distinguished in this species. In this paper, we present evidence for the existence of multiple transcripts encoding Brugian microfilarial chitinases. Using primers based on the previously-sequenced cDNA clone, we amplified and sequenced two discrete products from B. malayi microfilarial RNA by RT-PCR. While the shorter fragment was nearly identical to the previously sequenced cDNA, the larger fragment contained an extra copy of a serine/threonine-rich repeat. RNAse protection assays were used to demonstrate that both sequences represent true transcripts, and not PCR artifacts. Using primers based on the B.malayi sequence, two novel sequences were generated by RT-PCR from B. pahangi microfilariae. Homologous and cross-species RNAse protection assays verified that multiple transcripts also encode chitinase isozymes in B. pahangi microfilariae.

Amino Acid Sequence↗