Identification of genes involved in long-term survival in Pseudomonas aeruginosa PAO1

Pseudomonas aeruginosa is a remarkably adaptable organism which is able to survive and persist under a broad range of environmental conditions. The traditional views of bacterial growth phases usually come from standard laboratory cultures which can be different from natural conditions. In many natural environments, bacteria could maintain a long-term surviving status. To understand bacterial long-term survival, a luxCDABE-based random promoter library of P. aeruginosa was used to screen genes persistently expressed in the long-term culture of which 45 of such genes were identified. Among them, 13 genes encode different enzymes and are involved in different metabolic processes. Eight genes encode transcriptional regulators or two-component systems. In addition, a large portion of the identified genes encode hypothetical proteins with unknown function. Six of these unknown genes (PA1216, PA2827, PA0550, PA0256, PA0057 and PA4578) were selected and gene knockout mutants were constructed. All of these mutants exhibited reduced competitiveness than the wild-type PAO1 in the long-term competition assay, suggesting that these genes may play important roles for the long-term survival in P. aeruginosa.