Potential

arrangement variants are: arrangement as determined by genome sequencing [1], at least two head-to-tail copies of RD2, tail-to-tail, single copy arranged in reverse orientation than the integrative copy determined by genome sequencing, head-to-tail arrangement of copies in reverse orientation than the integrative copy determined by genome sequencing, head-to-head, and circular form. B. PCR screen detects product amplified Selleckchem MLN2238 with primer pairs #1+#2, #3+#4, and #2+#3, corresponding to arrangement variant (head-to-tail) or (circular form), and #1+#4 detecting chromosomal integration site lacking RD2. C. Primers #2+#3 detect arrangement variant 2 or 7 in multiple RD2 positive strains [1]. Serotype M1 strain MGAS5005 (lacks RD2) was used as a negative control of amplification. To further investigate the putative presence of multiple extrachromosomal copies of RD2 in GAS cells, we performed quantitative real time PCR using total DNA isolated from MGAS6180 strain. Performed analysis revealed that RD2 is present in 6-9 copies per chromosome (Figure 5B, see below). Also,

the amplification of chromosomal junction (primers #1+#4) suggests that RD2 can be excised from the site of integration. Figure 5 Mitomycin C treatment results in amplification of RD2. A Rapid decrease in O.D. of a liquid culture of strain MGAS6180 after mitomycin C addition. The decreased O.D. is likely due to prophage BI 2536 cell line induction followed by lytic cycle EX 527 research buy Interleukin-2 receptor phage release. Smaller drop in OD is

observed after treatment with hydrogen peroxide. B. The RD2 element is present in 6-9 copies per chromosome in the absence of inducer. C. The RD2 element is not induced by oxidative stress. Bars in each group represent the RD2 copy number after 1 h, 2 h, 3 h, and 16 h after treatment with hydrogen peroxide. D. RD2 is induced by DNA damage. Bars in each group represent the increase in copy number at 1 h, 2 h, 3 h, and 16 h after treatment with mitomycin C. The statistical significance of the increase in RD2 copy number was determined by t-test, *** on the graph denotes p value below 0.001. Taken together, these results indicate that a circular form of RD2 is present in strain MGAS6180. Response of strain MGAS6180 to mitomycin C and hydrogen peroxide treatment We hypothesized that the putative circular form detected in overnight cultures (see above) is a transient form involved in DNA transfer. DNA damaging factors as ultraviolet light, hydrogen peroxide, or mitomycin C can induce mobilization of genetic elements such as prophages or pathogenic islands as part of a response to DNA damage or oxidative stress [23]. To test hypothesis that RD2 was induced/excised by DNA damage and oxidative stress, we examined induction of RD2 and five other integrative elements present in the genome of strain MGAS 6180 by mitomycin C and hydrogen peroxide treatment.