It is possible that some kinds of cell growth or division signals are misread in the presence of phenol in the

colR mutant, which eventually leads to the cell lysis. In that case phenol could act as a signal, leading to the cell death, rather than being killing factor itself. Our further experiments will hopefully clarify whether phenol- and glucose-caused stresses originate from the same defect of the colR mutant or they are caused by different reasons. Conclusions Current study demonstrates the involvement of the ColRS two-component system and the TtgABC efflux pump in phenol tolerance of P. putida. Our results imply that TtgABC and ColRS systems are not directly connected ABT-888 ic50 and may affect phenol tolerance via independent pathways. Both these systems affect phenol tolerance of growing cells only but not of starving ones, indicating that ColRS and TtgABC systems affect processes occurring in metabolically active and dividing bacteria. Most tolerance mechanisms to aromatic hydrocarbons are directed toward maintaining the cell membrane intactness [2]. Given that ColRS and TtgABC systems are also implicated in membrane functions [12, 30, 38], it is reasonable to conclude that they may assist in regulation of biosynthesis and/or turnover

of membrane components, so helping to maintain membrane homeostasis during growth and division. Population structure analysis at single cell level revealed that strong cell division inhibition occurred in phenol-exposed population which check details could be considered as adaptive response to phenol stress to reduce the phenol-caused damage and to maintain membrane homeostasis. Acknowledgements We are grateful to Tiina Alamäe and Paula Ann Kivistik for critically reading the manuscript. We thank Riho Teras for plasmid pUCNotKm. Dimitri Lubenets is specially acknowledged for operating FACSAria. This work was supported by grant 7829 from the Estonian Science Foundation to R. H., and by funding of Targeted Financing Project TLOMR0031 from the Estonian Ministry of Research and Education and by grant HHMI 55005614 from the Howard Hughes

Medical Cell press Institute International Research Scholars Program to M. K. Electronic supplementary material Additional file 1: Plate assay of phenol tolerance of P. putida PaW85 (wt) and colR -deficient (colR) strains. Cells were grown on glucose (glc) minimal medium in the presence or absence of 8 mM phenol. Approximate number of inoculated bacterial cells is indicated above the figure. Bacteria were photographed after 4 days of growth. (PDF 188 KB) Additional file 2: Comparative analysis of subpopulations with different DNA content by staining of cells with SYTO9 and PI or SYTO9 alone. P. putida wild-type (wt) and ttgC-deficient (ttgC) strains were grown for 24 h on gluconate minimal selleck screening library plates supplemented with 8 mM phenol. Cells were stained with PI and SYTO9 (SYTO9+PI) or SYTO9 alone and analysed by flow cytometry.