The carboxy terminal domain of Epr, a minor extracellular serine protease, is essential for the swarming motility ofBacillus subtilis168

Abstract

In this study we have investigated the role of Epr, a minor extracellular serine protease, in the swarming motility of Bacillus subtilis 168. We identified that the protease activity of Epr was dispensable for swarming. Since the protease activity of Epr was confined to its N-terminal domain, we hypothesized instead that its C-terminal domain (CTD) could be critical for swarming. Our study showed that not only the expression of Epr-CTD was necessary, but also its secretion was crucial for the swarming motility of B. subtilis 168.

Laboratory Strains ofBacillus subtilisDo Not Exhibit Swarming Motility

“…It has been proposed that Epr has a C-terminal domain which, when proteolytically cleaved, acts as an extracellular signal that promotes swarming behavior (12,24). Mutation of epr in 3610, however, resulted in no impairment of swarming on LB or B medium, consistent with other reports (6) (Fig.…”

“…Swarming motility of strain 3610 requires the production of a secreted surfactant, called surfactin (6,20), to reduce surface tension and permit surface spreading, and it also requires the protein SwrA to activate flagellar biosynthesis gene expression and increase the number of flagella on the cell surface (5,20). Some reports claim that domesticated derivatives of 3610, such as the commonly used laboratory strain 168, are also swarming proficient (10,18,19,24). Strain 168, however, is defective in both surfactin production (9,25) and SwrA (5,21,31), and thus, swarming 168 strains challenge the genetic definition of swarming motility.…”

Epr plays a key role in DegU-mediated swarming motility ofBacillus subtilis

“…Swarming motility in NCIB3610 is regulated by very low levels of the phosphorylated form of DegU (DegU∼P) (Kobayashi, 2007; Verhamme et al ., 2007). We had previously shown that Epr is involved in the swarming motility of B. subtilis 168 (Dixit et al ., 2002; Murudkar et al ., 2006). Therefore, we assessed whether the expression of epr is dependent on low or high levels of DegU∼P.…”

“…The protease activity resides within the first 405 amino acid from the N‐terminus of Epr (Bruckner et al ., 1990). We have shown that processing of the 240 amino acids from the C‐terminus of Epr provides the signals essential for the swarming motility of B. subtilis 168 (Murudkar et al ., 2006). Because swarming motility and the expression of exoproteases are biochemically separated by two different levels of DegU∼P (Verhamme et al ., 2007), we were thus intrigued by the apparent paradox that swarming motility is dependent on the expression of the exoprotease, Epr.…”

ScoC and SinR Negatively Regulateeprby Corepression inBacillus subtilis

“…We had previously shown that Epr, a minor extracellular protease in Bacillus subtilis (5,32), is transcribed by a Ddependent RNA polymerase and that it is involved in swarm activity (8,25). We were thus interested in determining how this gene is regulated.…”