Fis regulates the competitiveness of Pseudomonas putida on barley roots by inducing biofilm formation

Abstract

An important link between the environment and the physiological state of bacteria is the regulation of the transcription of a large number of genes by global transcription factors. One of the global regulators, Fis (factor for inversion stimulation), is well studied in Escherichia coli, but the role of this protein in pseudomonads has only been examined briefly. According to studies in Enterobacteriaceae, Fis regulates positively the flagellar movement of bacteria. In pseudomonads, flagellar movement is an important trait for the colonization of plant roots. Therefore we were interested in the role of the Fis protein in Pseudomonas putida, especially the possible regulation of the colonization of plant roots. We observed that Fis reduced the migration of P. putida onto the apices of barley roots and thereby the competitiveness of bacteria on the roots. Moreover, we observed that overexpression of Fis drastically reduced swimming motility and facilitated P. putida biofilm formation, which could be the reason for the decreased migration of bacteria onto the root apices. It is possible that the elevated expression of Fis is important in the adaptation of P. putida during colonization of plant roots by promoting biofilm formation when the migration of bacteria is no longer favoured.

Fis overexpression enhances Pseudomonas putida biofilm formation by regulating the ratio of LapA and LapF

“…Switching from planktonic to sessile growth requires reorganization of bacterial physiology and thus the expression of a large number of genes is changed during the process of attachment to abiotic or biotic surfaces (Mathesius, 2009;Matilla et al, 2007Matilla et al, , 2011Ramos-González et al, 2005). Indeed, we have shown that the global regulator Fis (factor for inversion stimulation) is involved in Pseudomonas putida PaW85 biofilm formation (Jakovleva et al, 2012). In addition, Fis reduces motility and recolonization of new areas on barley roots, showing that Fis is involved in the regulation of P. putida sessile and planktonic lifestyles (Jakovleva et al, 2012).…”

“…Indeed, we have shown that the global regulator Fis (factor for inversion stimulation) is involved in Pseudomonas putida PaW85 biofilm formation (Jakovleva et al, 2012). In addition, Fis reduces motility and recolonization of new areas on barley roots, showing that Fis is involved in the regulation of P. putida sessile and planktonic lifestyles (Jakovleva et al, 2012).…”

“…We have shown that overexpression of Fis in P. putida causes enhanced biofilm formation in rich media like LB, King B and barley seedling medium (Jakovleva et al, 2012). In this work, we carried out transposon mutagenesis to find possible Fis target genes that could affect P. putida biofilm formation.…”

“…Although Fis is well-studied in enterobacteria, the role of this protein in pseudomonads has only been examined in a few published studies (Jakovleva et al, 2012;Kugelberg et al, 2005;Perron et al, 2005;Teras et al, 2009;Yeung et al, 2009;Yuste et al, 2006). Fis binds and bends DNA, and thereby it participates in several important processes for Escherichia coli, such as modulating DNA supercoiling (Schneider et al, 1999(Schneider et al, , 2001Travers et al, 2001), direct regulation of transcription (Bradley et al, 2007;González-Gil et al, 1996;Xu & Johnson, 1995) and regulation of certain site-specific DNA recombination events (Dorgai et al, 1993;Finkel & Johnson, 1992;Johnson et al, 1986).…”

“…Liberati et al, 2006;Osuna et al, 1995;Teras et al, 2009;Yeung et al, 2009), which makes it difficult to study Fis's involvement in P. putida biofilm formation. Indeed, we can only examine Fis's impact on P. putida biofilm using the fis-overexpression strain F15, since all our attempts to reduce the amount of Fis by fis gene deletion or conditional gene expression resulted in a lethal genotype or unexpected recombination of the native fis to somewhere in the P. putida genome (Jakovleva et al, 2012).…”