A cell‐surface polysaccharide that facilitates rapid population migration by differentiated swarm cells of Proteus mirabilis

Abstract

Swarming by Proteus mirabilis is characterized by cycles of rapid population migration across surfaces, following differentiation of typical vegetative rods into long, hyperflagellated, virulent swarm cells. A swarm-defective TnphoA insertion mutant was isolated that was not defective in cell motility, differentiation or control of the migration cycle, but was specifically impaired in the ability to undergo surface translocation as a multicellular mass. The mutation, previously shown to compromise urinary tract virulence, was located within a 1112 bp gene that restored normal swarming of the mutant when expressed in trans. The gene encoded a 40.6 kDa protein that is related to putative sugar transferases required for lipopolysaccharide (LPS) core modification in Shigella and Salmonella. The immediately distal open reading frame encoded a protein that is related to dehydrogenases involved in the synthesis of LPS O-side-chains, enterobacterial common antigen and extracellular polysaccharide (PS). Gel electrophoresis and electron microscopy showed that the mutant still made LPS but it had lost the ability to assemble a surface (capsular) PS, which gas-liquid chromatography and mass spectrometry indicated to be an acidic type II molecule rich in galacturonic acid and galactosamine. We suggest that this surface PS facilitates translocation of differentiated cell populations by reducing surface friction.

Roles for motility in bacterial–host interactions

“…In contrast, a number of insertions uncoupled these phenotypes, resulting in mutants that swim but cannot swarm, or that swarm aberrantly. These were also affected in chemotaxis, extracellular polysaccharide synthesis or cell elongation, which are themselves complex traits (Belas et al, 1995;Gygi et al, 1995). From the standpoint of this discussion, a particularly striking observation is that conversion of vegetative cells into swarm cells is accompanied by a marked increase in expression of several putative virulence factors (Allison et al, 1992).…”

The interaction of thin-film flow, bacterial swarming and cell differentiation in colonies of Serratia liquefaciens

“…Under general conditions, S. liquefaciens directly extract the wetting-agent from the underlying media. Rauprich et al (1996) indicate that a similar phenomenon in colonies of Proteus mirabilis is facilitated by an extracellular acidic capsular polysaccaride (see Gygi et al 1995). This chemical component works together with the physical behaviour of the swarmer cells in order to extract a wetting agent from the underlying medium.…”

Structural and serological studies on a new acidic O‐specific polysaccharide of Proteus vulgaris O32

“…This may enhance the formation of struvite and carbonate apatite stones in urinary tract under alkaline conditions in the presence of ammonia, one of the products of urea decomposition caused by Proteus bacteria [11]. Recently, the importance of an acidic polysaccharide rich in galacturonic acid and galactosamine was demonstrated for migration of P. mirabilis swarm cells by reduction of surface friction [12].…”

“…This may enhance the formation of struvite and carbonate apatite stones in urinary tract under alkaline conditions in the presence of ammonia, one of the products of urea decomposition caused by Proteus bacteria [11]. Recently, the importance of an acidic polysaccharide rich in galacturonic acid and galactosamine was demonstrated for migration of P. mirabilis swarm cells by reduction of surface friction [12].A few structures of P. vulgaris O-antigens have been elucidated, some of them having been found neutral [7,13] and the others acidic [7Ϫ9]. Now, we report the structure of a new acidic O-specific polysaccharide of P. vulgaris O32 containing D-galacturonic acid.…”