Toxin Synthesis and Mucin Breakdown Are Related to Swarming Phenomenon in Clostridium septicum

Abstract

Clostridium septicum is responsible for several diseases in humans and animals. The bacterium is capable of a simple kind of multicellular behavior known as swarming. In this investigation, environmental and physiologic factors affecting growth and swarm cell formation in C. septicum were studied over a range of dilution rates (D ‫؍‬ 0.02 to 0.65 h ؊1 ) in glucose-limited, glucose-excess, and mucin-limited chemostats. Cellular differentiation was observed at low specific growth rates, irrespective of the carbon and energy source, showing that swarming occurred in response to nutrient depletion. Differential expression of virulence determinants was detected in swarm cells. Hemolysin was secreted by short motile rods but not swarm cells, whereas in cultures grown with glucose, only swarm cells formed DNase, hyaluronidase, and neuraminidase. However, neuraminidase and, to a lesser degree, hyaluronidase were induced in short motile rods in mucin-limited cultures. Both swarm cells and short rods were cytotoxic to Vero cells. Mucin was chemotaxic to C. septicum, and large amounts of mucin-degrading enzymes (␤-galactosidase, N-acetyl ␤-glucosaminidase, glycosulfatase, and neuraminidase) were produced. Synthesis of these enzymes was catabolite regulated. In chemostat experiments, glycosulfatase secretion occurred only in swarm cells at low dilution rates in mucin-limited cultures. Determinations of oligosaccharide utilization demonstrated that N-acetylglucosamine, galactose, and N-acetylgalactosamine were the main carbon sources for C. septicum in mucin. Neuraminic acid was not assimilated, showing that neuraminidase does not have a direct nutritional function in this pathogen.

Swarming motility in Bacillus cereus and characterization of a fliY mutant impaired in swarm cell differentiation The EMBL accession number for the sequence reported in this paper is Y08031.

“…B. cereus swarm colonies never exhibited macroscopically layered consolidation phases due to regularly spaced cycles of swarming migration and consolidation. As also reported for Y. enterocolitica, S. liquefaciens and Clostridium septicum (Eberl et al, 1999 ;Macfarlane et al, 2001 ;Young et al, 1999), B. cereus appeared to swarm continuously at the colony rim, while the colony centre apparently consisted of a unique consolidation phase.…”

“…In P. mirabilis, swarming has been associated with the ability to invade urothelial cells and to express higher levels of virulence factors, such as intracellular urease, extracellular haemolysin and metalloprotease (Allison et al, 1992a(Allison et al, , b, 1994. Swarming by S. liquefaciens was found to be accompanied by an increase in the expression of the phospholipase gene (Eberl et al, 1996), and C. septicum was capable of producing DNase, hyaluronidase and neuraminidase only during the swarm-cell state (Macfarlane et al, 2001). The fact that the B. cereus mutant harbouring an expression plasmid containing fliY regained the ability to swarm and to produce the L # component of HBL strongly suggests that a relationship between expression of virulence factors and differentiation of swarm cells also exists in this organism.…”

“…the swimmer cells, which undergo a co-ordinated surfaceinduced differentiation process characterized by the production of hyperflagellated, elongated, multinucleate cells, i.e. the swarm cells (Eberl et al, 1996 ;Harshey & Matsuyama, 1994 ;Henrichsen, 1972 ;Hoeniger & Taushel, 1974 ;Macfarlane et al, 2001) Abbreviations : CI, capilliary index ; HBL, haemolysin BL ; RAPD, randomly amplified polymorphic DNA ; TBS, tris-buffered saline.…”

Swarming Differentiation and Swimming Motility inBacillus subtilisAre Controlled byswrA, a Newly Identified Dicistronic Operon

“…This type of locomotion is strictly dependent on the ability of surface-adhering bacteria to undergo a differentiation process characterized by the production of specialized swarm cells, longer and more flagellated than planktonic cells. Swarm cells are able to revert into the short oligoflagellated swimmer cells when the advancing front of swarmers stops migrating (1,7,9,12,14,15,25,36). Swarming, therefore, is regarded as a behavioral response to the surface, which provides flagellated bacteria with the ability to act as a multicellular population rapidly colonizing nutrient-rich solid substrates (38).…”

Identification of non-flagellar genes involved in swarm cell differentiation using a Bacillus thuringiensis mini-Tn10 mutant library

“…These cells aggregate themselves in rafts and migrate over the surface in a highly co-ordinated manner that is dependent on multicellular interactions and cell-to-cell signalling (Rather, 2005). In swarming-proficient pathogens, swarm cells may exert a higher degree of virulence due to their enhanced ability to adhere to and colonize the host mucosal surfaces (Allison et al, 1992a;Belas & Colwell, 1982;Callegan et al, 2006;Kirov et al, 2004), as well as to secrete increased amounts of specific virulence factors (Allison et al, 1992b;Ghelardi et al, 2007;Macfarlane et al, 2001).…”