Development of genetic tools for in vivo virulence analysis of Streptococcus sanguinis.
Completion of the genome sequence of Streptococcus sanguinis SK36 necessitates tools for further characterization of this species. It is often desirable to insert antibiotic resistance markers and other exogenous genes into the chromosome; therefore, we sought to identify a chromosomal site for ectopic expression of foreign genes, and to verify that insertion into this site did not affect important cellular phenotypes. We designed three plasmid constructs for insertion of erm, aad9 or tetM resistance determinants into a genomic region encoding only a small (65 aa) hypothetical protein. To determine whether this insertion affected important cellular properties, SK36 and its erythromycin-resistant derivative, JFP36, were compared for: (i) growth in vitro, (ii) genetic competence, (iii) biofilm formation and (iv) virulence for endocarditis in the rabbit model of infective endocarditis (IE). The spectinomycin-resistant strain, JFP56, and tetracycline-resistant strain, JFP76, were also tested for virulence in vivo. Insertion of erm did not affect growth, competence or biofilm development of JFP36. Recovery of bacteria from heart valves of co-inoculated rabbits was similar to wild-type for JFP36, JFP56 and JFP76, indicating that IE virulence was not significantly affected. The capacity for mutant complementation in vivo was explored in an avirulent ssaB mutant background. Expression of ssaB from its predicted promoter in the target region restored IE virulence. Thus, the chromosomal site utilized is a good candidate for further manipulations of S. sanguinis. In addition, the resistant strains developed may be further applied as controls to facilitate screening for virulence factors in vivo.
Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA.|The Philips Institute of Oral and Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Lauren
L
Senty Turner
The Philips Institute of Oral and Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Sankar
S
Das
The Philips Institute of Oral and Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Taisei
T
Kanamoto
Department of Adult Health Nursing, Virginia Commonwealth University, Richmond, VA 23298, USA.
Cindy L
CL
Munro
Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, VA 23298, USA.|Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA.|The Philips Institute of Oral and Craniofacial Molecular Biology, Virginia Commonwealth University, Richmond, VA 23298, USA.
Todd
T
Kitten
D000818:Animals; D001431:Bacteriological Techniques / Q000379:methods; D018441:Biofilms; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004697:Endocarditis, Bacterial / Q000209:etiology*; D005798:Genes, Bacterial; D008297:Male; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000378:metabolism; D011817:Rabbits; D013290:Streptococcal Infections / Q000150:complications / Q000378:metabolism / Q000382:microbiology*; D013298:Streptococcus sanguis / Q000472:pathogenicity / Q000502:physiology; D014774:Virulence
D004269:DNA, Bacterial