RNA sequencing of Acinetobacter baylyi and E. coli while co-incubating on LB agar plates

The bacterial type VI secretion system is a widespread secretion mechanism important for competition in many Gram-negative bacteria. Killing and lysing of competing bacteria can provide advantages such as nutrients or acquisition of new genes by DNA uptake. Here, we show that T6SS-dependent lysis of prey cells by the naturally competent Acinetobacter baylyi results in extensive filamentation of a significant subpopulation of A. baylyi cells. This is dependent on the release of genomic DNA from the lysed prey cells and its uptake by the competence system of A. baylyi. Single-cell level analysis using live-cell imaging shows that filamentous A. baylyi cells appear at the interface between the species. The analysis of A. baylyi transcriptome and the response of transcriptional reporters suggest that the uptake of genomic DNA results in a highly upregulated SOS response, which often leads to the cell division arrest. Using competition experiments, we show that the parental strain is outcompeted by a strain lacking the DNA uptake machinery because such mutant shows no SOS response-dependent cell division arrest. Our data suggest that the cost of SOS-response may drive selection of decreased DNA uptake in T6SS positive bacteria. Overall design: We analyzed expression profiles of A. baylyi in competition with E. coli. We deep-sequenced cDNA prepared from a mixture of E. coli with tae1-expressing (no other effectors present) and T6SS-deficient A. baylyi upon 10-30min of incubation.