Characterization of starvation‐induced dispersion in Pseudomonas putida biofilms

Abstract

The biofilm lifestyle, where microbial cells are aggregated because of expression of cell-to-cell interconnecting compounds, is believed to be of paramount importance to microbes in the environment. Because microbes must be able to alternate between sessile and planktonic states, it is anticipated that they must be able to regulate their ability to form biofilm and to dissolve biofilm. We present an investigation of a biofilm dissolution process occurring in flow-chamber-grown Pseudomonas putida biofilms. Local starvation-induced biofilm dissolution appears to be an integrated part of P. putida biofilm development that causes characteristic structural rearrangements. Rapid global dissolution of entire P. putida biofilms was shown to occur in response to carbon starvation. Genetic analysis suggested that the adjacent P. putida genes PP0164 and PP0165 play a role in P. putida biofilm formation and dissolution. PP0164 encodes a putative periplasmic protein of previously unknown function, and PP0164 mutant bacteria are sticky, and unable to reduce their adhesiveness and dissolve their biofilm in response to carbon starvation. PP0165 encodes a putative transmembrane protein containing GGDEF and EAL domains, and PP0165 mutant bacteria are unable to increase their adhesiveness and form biofilm. We suggest that the PP0164 and PP0165 proteins are involved in the regulation of the adhesiveness of the bacteria; the PP0165 protein through c-di-GMP signalling, and the PP0164 protein as a transducer of the signal.

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…2) (62). A similar system has recently been identified in Pseudomonas putida (50). Time-lapse microscopy studies determined that ⌬lapA mutants (as well as other lap mutants) are unable to progress from reversible to irreversible attachment on abiotic surfaces that these organisms likely encounter in the environment (62).…”

“…First described to control extracellular cellulose biosynthesis in Acetobacter xylinum, high c-di-GMP levels are now known to correlate with the motile-sessile transition in several microorganisms (32, 69, 112, 136-138, 142, 152). Modulation of c-di-GMP has furthermore been linked to biofilm dispersion (9,50,112,152), a mechanism used by biofilm bacteria to successfully transition to the planktonic growth state (140). C-di-GMP production and degradation are controlled by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), respectively, with overexpression of these enzymes generally causing global effects.…”

“…Release of LapA from attached cells promotes their detachment from the substratum and bacteria returning to the free-swimming mode of growth. The model is based on structural and functional analyses (50,62,109,116,118).…”

Selection of hyperadherent mutants in Pseudomonas putida biofilms

“…Images correspond to 3 h (top row) and 6 h (bottom row) of growth. also disrupted (Gjermansen et al, 2005(Gjermansen et al, , 2010. Interestingly, the four olpA mutants identified in the initial screening for ibi clones had the same point mutation in lapG.…”

“…In both KT2440 and ibi-626, a single base pair upstream of this locus is missing with respect to the published sequence. PP_0164 corresponds to lapG, a gene that has been proposed to act as a signal transducer in biofilm formation (Gjermansen et al, 2005), and more recently has been shown to encode a cysteine protease that affects the function of LapA in P. fluorescens (Newell et al, 2011), the main adhesin of this bacterium and of P. putida (Hinsa et al, 2003;Yousef-Coronado et al, 2008). Transposon mutants in which lapG is disrupted have been shown to be defective in detachment from biofilms, an effect that is compensated when lapA is Fig.…”