At later time points, hybridization with relB (Figure 1A) and relE (Figure 1B) probes gave different signals: in response to induction of MazF, MqsR, and HicA we saw cleavage of the full-length mRNA and massive accumulation of the toxin-encoding part, while the antitoxin-coding portion could not be detected and was apparently degraded

(Figure 1A,B). Such cleavage and accumulation of the toxin portion also occurred in response to RelE. Hybridization with relF probe revealed additional cleavage, both within relE and downstream, in response to expression of all these toxins, and the relF part accumulated as the AZD1390 manufacturer most abundant portion of the relBEF transcript (Figure 1C). Also, some transcripts larger than the full relBEF mRNA appeared, particularly after induction of RelE and MqsR. Production of HipA, which is not a ribonuclease, conferred strong induction of full-length relBEF mRNA but cleavage and uneven accumulation of different

mRNA fragments could not be seen. MUP treatment produced overproduction of the full relBEF mRNA as well as accumulation of some cleavage products. VE-822 research buy Production of YafQ did not lead to a clear cross-activation of relBEF transcription. However, relE probe showed accumulation of a short RNA fragment in response to this toxin. It is possible, that transcription of the operon is activated by YafQ but the transcript is degraded to small fragments. Clearly, these fragments cannot serve as templates for synthesis of RelE and, therefore, functional cross-activation does not occur. Protein Tyrosine Kinase inhibitor Modest induction of relBEF with no cleavage was evident in the 1h and 2h samples of control cultures, lacking artificial production of any free toxin. We have to consider that, at this stage, the control cultures were approaching stationary phase, and induction of toxin-antitoxin modules has been described in similar conditions [48]. Probes complementary to yiaF and rpsS were used for control because the levels of transcription of these genes did not differ between

log phase cells and the ampicillin-refractory non-growing subpopulation, where TA operons were selleck products highly expressed [38]. rpsS is a part of the large S10 ribosomal protein operon with an estimated transcribed length of 5181 bp [49]; yiaF (711 bp ORF) encodes for a putative membrane protein of unknown function; it is located between genes pointing in the opposite direction and must form a single-gene operon. The control mRNAs were not induced by toxins (Additional file 1: Figure S2B,C). After induction of toxins, the yiaF transcript was degraded without accumulation of any stable fragments. (Additional file 1: Figure S2B). Surprisingly, mupirocin initially induced transcription of yiaF whereas the level of the transcript dropped after longer incubation (Additional file 1: Figure S2B). The S10 transcript was degraded as well. Some accumulating stable fragments of the S10 transcript were detectable after MazF, RelE and MqsR production (Additional file 1: Figure S2C).