Cell surface properties correlated with cohesion in Myxococcus xanthus

Abstract

The gliding behavior of Myxococcus xanthus cells is controlled by two multigene systems, A and S, which encode information for adventurous and social behaviors, respectively. The S system can be genetically disrupted through mutation, such as a dsp mutation, or phenotypically disrupted by treating cells with the diazo dye Congo red (Arnold and Shimkets, J. Bacteriol. 170:5765-5770, 1988). One of the functions controlled by the S system is cell agglutination. Immediately after the induction of agglutination, wild-type cells begin to form aggregates, and within 30 min the cells are packed side-to-side in clumps containing thousands of cells. Changes in the cohesive properties of S+ cells are correlated with changes in the topology of the cell surface observed by electron microscopy. Two types of cell-associated appendages were observed on wild-type cells: thin filaments (ca. 5 nm in diameter), which have been called fimbriae or pili, at one cell pole, and thick, flaccid ifiaments (ca. 50 nm in diameter), referred to as fibrils, at both the sides and tips of cells. Cohesion was correlated with the secretion of the thick fibrils, which coat the cell surface and form an extracellular matrix in which the cells are interconnected. Several lines of evidence suggest that these thick fibrils are involved in cohesion. First, Dsp cells were unable to agglutinate or secrete this extracellular material. Second, wild-type cells which were treated with Congo red neither agglutinated nor secreted the extracellular fibrils. Finally, removal of the Congo red from wild-type cells restored cohesion and also restored production of the thick fibrils. Attempts to estimate the efficiency with which two cells cohered following collision suggested that under optimal conditions, one in three collisions resulted in stable contact. The collision efficiency decreased linearly as the cell density increased, suggesting a cell density-dependent regulation of cohesion. Some aspects of gliding behavior can be explained in terms of an inducer and an inhibitor of S motility.

The unique DKxanthene secondary metabolite family from the myxobacterium Myxococcus xanthus is required for developmental sporulation

“…Similarly, polysaccharide production as tested in the trypan blue assay (25,26) indicative for defects in extracellular matrix formation as well as trehalose accumulation (27) in the spores thought to be involved in heat and desiccation resistance showed no difference between wild type and mutant (data not shown). Antioxidant Activity of DKxanthene 534.…”

Nanoscale visualization and characterization of Myxococcus xanthus cells with atomic force microscopy

“…The dif mutants lack extracellular fibril material. SEM observations had originally defined ''fibrils'' as a matrix material consisting of branching extensions Ϸ30 nm in diameter that surrounds the wild-type cells (23,24). Later studies revealed that these fibrils likely form a mesh of extracellular polymeric substances over the entire cell body (25,31).…”

“…Contact-mediated cell-cell interactions are an important aspect of the social behavior of M. xanthus and are facilitated by extracellular fibril material that exists on the surface of the cells (17,23,24). The force-spectroscopy capacity of AFM allows us to investigate the nanomechanical properties of the M. xanthus surface adhesive molecules.…”

“…Extracellular fibril material has been visualized under SEM as 30-to 50-nm-thick intercellular fibers (23) that form a mesh-like network surrounding the cell body (24). Because mutants lacking fibril material are unable to agglutinate in liquid suspension, it was hypothesized that cohesion is the major role of fibril material (23). Biochemical analysis suggested that fibril material is composed of approximately equal amounts of protein and carbohydrate (25).…”

ADP‐ribosylation by the extracellular fibrils of Myxococcus xanthus

“…The peritrichous fibrils of M. xanthus play a role in the development and social behaviour of M. xanthus (Arnold and Shimkets, 1988;Behmlander and Dworkin, 1991;Chang and Dworkin, 1994). However, the mechanism whereby they may mediate contact between cells is unknown.…”