Paenibacillus polymyxa rhizobacteria associate
with a wide range of plants and promote plant growth and
development. These bacteria produce exopolysaccharides,
which are very important for P. polymyxa adaptation to chang-
ing environmental conditions. In this study, five P. polymyxa
strains differing in exopolysaccharide yield and properties
(CCM 1465, CCM 1460, CCM 1459 T , 88A, and 92) were
investigated for motility in a liquid and a semisolid nutrient
medium with either glucose or sucrose as the carbon source. In
the liquid medium, all strains except CCM 1460 were motile
and swam by peritrichous flagella. After being stab inoculated
into the semisolid (0.4% agar) medium, all strains except
CCM 1460 switched to collective swarming and formed con-
centric macrocolonies with different diameters, depending on
the strain and the carbon source used. On the semisolid medi-
um containing the vital dye Congo red, P. polymyxa adsorbed
the dye, forming stained colonies. No changes in colony mor-
phology were observed. At 37.5 μg ml −1 of Congo red,
swarming was strongly suppressed: the swarming ring diam-
eters of strains 92, CCM 1459 T , 88A, and CCM 1465 ranged
from 12.4 to 17% (glucose) and from 9.5 to 16.0% (sucrose)
of the colony diameters obtained from bacterial growth with-
out the dye. The results suggest that the speed of collective
migration of P. polymyxa on agarized media may be affected,
among other factors, by the yield and physicochemical

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• Motility in liquid and semisolid media of Paenibacillus polymyxa associative rhizobacteria differing in exopolysaccharide yield and properties