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Biomedical subjects

M C Hudson

Publications and source records attributed to M C Hudson.

7 recordsLinked to original sources
PubMed1991

Use of the polymerase chain reaction in detection of culturable and nonculturable Vibrio vulnificus cells.

Vibrio vulnificus is a human pathogen associated with consumption of raw oysters. During the colder months the organism apparently enters a viable but nonculturable state and thus cannot be cultured by ordinary bacteriological methods. For this reason, another means of detecting this bacterium is necessary. In the present study we utilized the polymerase chain reaction (PCR) to detect V. vulnificus DNA, thus eliminating the problem of nonculturability. DNA from both culturable and nonculturable cells of V. vulnificus was amplified by PCR with primers flanking a 340-bp fragment of the cytotoxin-hemolysin gene. As little as 72 pg of DNA from culturable cells and 31 ng of DNA from nonculturable cells could be detected. Fifty cycles of a two-step reaction (30 s [each] at 94 and 65 degrees C) were found to be optimal as well as more time efficient than the three-step PCR. The total procedure from the point of DNA extraction to observation on a gel required less than 8 h. Possible reasons for the difficulties encountered in amplifying DNA from nonculturable cells, e.g., gene rearrangement or loss of the hemolysin gene, are discussed.

Base Sequence↗
PubMed1990

Regulation of expression of Streptococcus mutans genes important to virulence.

Studies were initiated to investigate the regulation of Streptococcus mutans genes which are believed to be important to virulence. Operon fusions were constructed between S. mutans gene regulatory regions and a promoterless chloramphenicol acetyltransferase gene (cat) found on the plasmid pMH109. Specifically, fusions were generated between cat and the S. mutans genes encoding fructosyltransferase (ftf) and the glucosyltransferase B/C (gtfB/C) operon. Constructs were confirmed by restriction enzyme analysis, and the fusions were subcloned into the integration vehicle pVA891. Following generation of multimeric DNA, recombinant plasmids were introduced into the s. mutans genome by Campbell-type insertion, resulting in single-copy operon fusions. Chloramphenicol acetyltransferase specific activities were used to monitor the expression of the S. mutans gtfB/C operon and ftf determinants. The expression of these genes is increased by the presence of sucrose and is followed by a rapid decline in expression over time. Additionally, expression of the gtfB/C operon is increased in S. mutans cells bound to artificial tooth pellicles.

Chloramphenicol O-Acetyltransferase↗
PubMed1986

Differential utilization of Staphylococcus aureus promoter sequences by Escherichia coli and Bacillus subtilis.

Promoter-cloning plasmids were constructed and have been used to isolate transcriptionally active DNA fragments from Staphylococcus aureus. The plasmids contain a chloramphenicol acetyltransferase (CAT) gene of Gram-positive (G+) origin which lacks both its promoter and the sequence responsible for CAT inducibility. The ability of S. aureus promoters to direct CAT expression in Escherichia coli and Bacillus subtilis was examined. Two classes of staphylococcal promoter sequences have been obtained. Class I DNA fragments direct CAT expression in S. aureus, B. subtilis, and E. coli, while class II DNA sequences direct CAT expression only in the G+ hosts.

Acetyltransferases↗