Rapid Surface Motility in Bacillus subtilis Is Dependent on Extracellular Surfactin and Potassium Ion

Abstract

Motility on surfaces is an important mechanism for bacterial colonization of new environments. In this report, we describe detection of rapid surface motility in the wild-type Bacillus subtilis Marburg strain, but not in several B. subtilis 168 derivatives. Motility involved formation of rapidly spreading dendritic structures, followed by profuse surface colonies if sufficient potassium ion was present. Potassium ion stimulated surfactin secretion, and the role of surfactin in surface motility was confirmed by deletion of a surfactin synthase gene. Significantly, this motility was independent of flagella. These results demonstrate that wild-type B. subtilis strains can use both swimming and sliding-type mechanisms to move across surfaces.

Branched swarming patterns on a synthetic medium formed by wild-type Bacillus subtilis strain 3610: detection of different cellular morphologies and constellations of cells as the complex architecture develops

“…The presence of both flagella and a detergent-like lipopeptide (surfactin), secreted by the bacteria and subject to regulation by quorum sensing in planktonic culture (Solomon et al, 1995), has also been implicated in swarming in this organism (Ohgiwari et al, 1992;Wakita et al, 1998). Some reports, however, have indicated that swarming can occur independently of either flagella or surfactin (Dixit et al, 2002;Kinsinger et al, 2003;Mendelson & Salhi, 1996). In our studies with the laboratory strain 168 (Trp 2 ), the bacteria, although SrfA 2 , still swarmed efficiently on LB agar, albeit less rapidly than strain 3610.…”

“…Such patterns also occur in the branching architecture of the lung and in structures formed by non-living systems, for example snow crystals. Swarming in B. subtilis is reported to require the presence of flagella (Ohgiwari et al, 1992), although flagellaindependent swarming has also been described recently (Kinsinger et al, 2003). An antibiotic surfactant, whose synthesis is subject to control by quorum sensing (Solomon et al, 1995;Solomon & Grossman, 1996), has also been implicated in swarming in this organism (Kearns & Losick, 2003;Bees et al, 2000; see also Wakita et al, 1998).…”

Leakage and lysis of lipid membranes induced by the lipopeptide surfactin

“…It consists of a cyclic heptapeptide moiety with the typical sequence GluLeu-D-Leu-Val-Asp-D-Leu-Leu which is closed to a lactone ring by a C 14-15 b-hydroxy fatty acid. Surfactin is highly surface active, which may play a key role for the motility of the bacillus (Kinsinger et al 2003) as well as for technical applications (Cameotra and Makkar 2004). Given the great interest in the development of new peptide antibiotics, it is of particular relevance that surfactin possesses also hemolytic (Kracht et al 1999), anti-viral (Kracht et al 1999;Vollenbroich et al 1997a), anti-bacterial (Beven and Wroblewski 1997;Vollenbroich et al 1997b), and anti-tumor (Kameda et al 1974) activity.…”

Water reservoir maintained by cell growth fuels the spreading of a bacterial swarm

“…Some bacteria synthesize biosurfactants (1). Marangoni flows driven by surface-tension gradients can account for the flagellar-independent colony expansion of some species, such as Bacillus subtilis that produces surfactin (12)(13)(14). However, this cannot be the general mechanism driving swarm-fluid spreading because most swarming is flagella dependent and does not always require production of surfactants (1).…”