Evidence for plasmid DNA in Alcaligenes faecalis

Area of Science:

• Microbiology
• Bacterial Genetics
• Plasmid Biology

Background:

• Alcaligenes faecalis is an opportunistic pathogen.
• Plasmids are extrachromosomal DNA elements that can carry genes for virulence and antibiotic resistance.
• The role of specific plasmids in bacterial virulence is not always well-defined.

Purpose of the Study:

• To investigate the role of a specific plasmid in the virulence and antibiotic resistance of Alcaligenes faecalis.
• To compare the characteristics of a virulent strain with its plasmid-free derivative.

Main Methods:

• Isolation of a 10.6 megadalton plasmid from a virulent Alcaligenes faecalis strain (NC-D).
• Generation of a plasmid-free mutant derivative (strain NC-D1).
• Comparative analysis of virulence and antibiotic sensitivity between the parent strain and the mutant derivative.

Main Results:

• The virulent strain NC-D harbored a 10.6 megadalton plasmid.
• The plasmid-free derivative, strain NC-D1, was avirulent.
• Strain NC-D1 lacked the streptomycin and sulfonamide resistance observed in the parent strain NC-D.

Conclusions:

• The isolated plasmid is associated with the virulence of Alcaligenes faecalis strain NC-D.
• The plasmid carries genes conferring resistance to streptomycin and sulfonamide.
• Plasmid loss in Alcaligenes faecalis results in avirulence and loss of specific antibiotic resistances.