oneidensis MR-1 strains constitutively expressing GFP was carried

oneidensis MR-1 strains constitutively expressing GFP was carried out using a Tn7 based delivery system [39]. GFP-labeling was performed by biparental mating. Cultures of S. oneidensis MR-1, AS262 and AS392 were grown in LB broth overnight. 0.5 mL of each culture containing about 108 cells was washed twice in

one culture volume of phosphate buffered saline (PBS). S. oneidensis MR-1 and AS262 cells were combined and resuspended in 250 μL PBS. AS392 cells were resupended in 250 μL PBS. 50 μL of the mixed S. oneidensis MR-1/AS262 cell suspension was combined with 50 μL AS392 cell suspension and spotted onto dry solidified LB medium. Petri dishes were incubated upright for 8 h at 30°C. The cell mass was then resuspended in PBS and spread onto LB agar supplemented with 10 μg/mL gentamycine to select for S. oneidensis MR-1 carrying a chromosomal insertion of the gfp-carrying Tn7. PCR was used to map the site of XMU-MP-1 supplier insertion in the S. oneidensis MR-1 genome. Tn5 mutagenesis and screen for mxd -deregulated mutants Transposon mutagenesis

was performed by mating AS536 with the donor strain E. coli BW20767 (AS259) harbouring suicide C646 plasmid pRL27, which carries a hyperactive transposase and a Tn5-mini transposon with a kanamycin resistance cassette and a R6K origin of replication [40]. The mating was performed at a 1:1 donor-recipient ratio at room temperature for 6 h. Transconjugants were plated onto solid LB medium Adenosine triphosphate containing kanamycin, tetracycline and X-gal to qualitatively screen for deregulated mxd mutants. Mutants were identified based on the intenstity of their blue colony color check details compared to the non-mutagenized control strain AS536. The mutant phenotypes were quantitatively confirmed by β -galactosidase assay in liquid culture. The location of a Tn5 insertion was mapped by arbitrary primed PCR [4]. Chromosomal DNA was prepared from the mutants and two rounds of amplification were used to specifically amplify and enrich for the DNA flanking the insertion

site. In the first round primer tpnRL 17-1-O or tpnRL 13-2-O, which are unique to one end of the transposon, and two different arbitrary primers ARB1 and ARB6 [4] were used for amplification. Among the many possible amplified regions from the first round of PCR were products primed from the transposon and flanking chromosomal DNA. Products flanking the transposon were specifically amplified in the second round of PCR with primers tpnRL17-1 or tpnRL13-2 [4] and ARB2. After the second round of PCR the obtained PCR products were purified and subsequently subjected to DNA sequence analysis using primers tpnRL17-1 or tpnRL13-2. To identify the location of the transposon insertion, the resulting nucleotide sequences were compared with the S. oneidensis MR-1 sequence database by BLAST search: (http://​blast.​ncbi.​nlm.​nih.​gov). β -galactosidase assay For β -galactosidase assays, S.

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