Characterization of Streptococcus criceti insertion sequence ISScr1.

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• The IS982 family insertion sequence element, ISScr1, was previously found disrupting the paaB gene in Streptococcus criceti E49.
• The paaB gene encodes an antigen I/II homologous protein, important in bacterial adhesion and virulence.

Purpose of the Study:

• To characterize the inserted regions of ISScr1 in S. criceti E49.
• To investigate the distribution and copy number of ISScr1 in different S. criceti strains.
• To explore potential correlations between ISScr1 presence and phenotypic variations in S. criceti.

Main Methods:

• Inverse polymerase chain reaction (IPCR) and gene-walking were used to identify ISScr1 insertion sites.
• Screening of a partial plasmid library aided in characterizing inserted regions.
• DNA hybridization analysis was employed to determine ISScr1 distribution and copy number across strains.
• Phenotypic assays assessed erythromycin susceptibility and dextran-induced agglutination.

Main Results:

• Two divergent inserted regions of ISScr1 were identified in S. criceti E49, with nucleotide analysis suggesting transposition generated direct repeat sequences.
• Identical ISScr1 hybridization patterns were observed in four studied S. criceti strains, with at least three copies present.
• Significant variations in erythromycin susceptibility and dextran-induced agglutination properties were noted among S. criceti strains.
• No ISScr1-like sequences were detected in 14 other oral streptococci strains tested.

Conclusions:

• ISScr1 is a mobile genetic element present in multiple copies within Streptococcus criceti strains.
• The presence and distribution of ISScr1 may contribute to the observed phenotypic diversity in S. criceti.
• ISScr1 appears specific to S. criceti and is not found in other related oral streptococci.