A new form of bacterial movement, dragging of multicellular aggregate structures over solid surfaces, is powered by macrofiber supercoiling.

Growing Bacillus subtilis macrofibers use twist and supercoiling to: power their own self-assembly, join fibers together into multiclonal aggregates, move themselves over solid surfaces, and to drag other structures (cargo) over solid surfaces. The dragging of multiclonal aggregates attached to the ends of growing macrofibers is analyzed here. The linkage between fibers and cargo arose naturally in macrofiber cultures.

The dynamic behavior of bacterial macrofibers growing with one end prevented from rotating: variation in shaft rotation along the fiber's length, and supercoil movement on a solid surface toward the constrained end.

Background: Bacterial macrofibers twist as they grow, writhe, supercoil and wind up into plectonemic structures (helical forms the individual filaments of which cannot be taken apart without unwinding) that eventually carry loops at both of their ends. Terminal loops rotate about the axis of a fiber's shaft in contrary directions at increasing rate as the shaft elongates. Theory suggests that rotation rates should vary linearly along the length of a fiber ranging from maxima at the loop ends to zero at an intermediate point.

The mechanisms responsible for 2-dimensional pattern formation in bacterial macrofiber populations grown on solid surfaces: fiber joining and the creation of exclusion zones.

Background: When Bacillus subtilis is cultured in a complex fluid medium under conditions where cell separation is suppressed, populations of multicellular macrofibers arise that mature into ball-like structures. The final sedentary forms are found distributed in patterns on the floor of the growth chamber although individual cells have no flagellar-driven motility. The nature of the patterns and their mode of formation are described in this communication.

Motions caused by the growth of Bacillus subtilis macrofibres in fluid medium result in new forms of movement of the multicellular structures over solid surfaces.

Bacillus subtilis macrofibres, highly ordered multicellular structures, undergo twisting and writhing motions when they grow in fluid medium as a result of forces generated by the elongation of individual cells. Macrofibres are denser than the fluid medium in which they are cultured, consequently they settle to the bottom of the growth chamber and grow in contact with it. The ramifications of growth on plastic and glass surfaces were examined.