Motility and Chemotaxis in Two Strains of Rhizobium with Complex Flagella

Abstract

Rhizobium meliloti MVII-1 and Rhizobium lupini H13-3, two strains with five to ten peritrichously inserted complex flagella, were studied with respect to motility and chemotaxis. Cells of both these strains move rapidly with speeds up to 40 pm s-I (R. meZiZoti) and 60 pm s-' ( R . Zupini) respectively. Increasing viscosity causes little reduction in their swimming velocities as compared with Salmonella typhimurium propelled by plain flagella. It is suggested that complex flagella possess a high 'flexural rigidity', which serves to maintain a helix conformation favourable for propulsive efficiency at increased viscosities. C hemotaxis in R . meliloti MVII-1 and R . lupini H13-3 was studied and the conditions required have been defined using the capillary tube assay. All 20 common L-amino acids and L-homoserine were shown to be attractive to R . meliloti MVII-1 with thresholds varying from lop6 M (proline) to M (aspartate). Leucine, proline and lysine elicited optimal responses. R hizobium lupini H13-3 was also attracted by L-amino acids except for leucine, which elicited no response. Aspartate was a significantly better attractant of R . Zupini H13-3 than of R . meliloti MVII-1, and glycine, isoleucine, homoserine, serine, threonine, cysteine, glutamine and glutamate were

Sinorhizobium meliloti Chemotaxis to Multiple Amino Acids Is Mediated by the Chemoreceptor McpU

“…However, chemoreceptors exhibit a very broad range of sensitivity (Bi and Lai 2015;Hazelbauer et al 2008), which makes the approximately 10-fold difference in exuded aa amounts negligible. S. meliloti RU11/001 chemoattraction to most aa is consistent with previous findings of the parental strain MVII-1, using traditional Adler capillary assays (Götz et al 1982). Recognition and chemotaxis toward a broad range of aa enables S. meliloti to benefit from these carbon compounds as energy sources and host-plant signaling molecules.…”

“…Motile cells for hydrogel capillary assays were grown for 2 days in TYC, were diluted 1:1,000 in 3 ml of TYC, and were grown overnight. Cultures were then diluted 1:1,000 in 10 ml of RB (6.1 mM K 2 HPO 4 , 3.9 mM KH 2 PO 4 , 1 mM MgSO 4 , 1 mM [NH 4 ] 2 SO 4 , 0.1 mM CaCl 2 , 0.1 mM NaCl, 0.01 mM Na 2 MoO 4 , 0.001 mM FeSO 4 , 20 µg of biotin per liter, 10 µg of thiamine per liter [Götz et al 1982]), were layered on Bromfield agar plates with no antibiotics (Sourjik and Schmitt 1996), and were incubated at 30°C for approximately 15 h, to an optical density at 600 nm (OD 600 ) of 0.16 ± 0.02.…”

Role of Motility and Chemotaxis in Efficiency of Nodulation by Rhizobium meliloti

“…Flagellar filaments presented a clear zig-zag configuration of high electron density bands around a possible central filament and a total diameter of 16.0 + 0.9 nm. These observations are consistent with those obtained by Gotz et al (21) for R. lupini H13-3 and R. meliloti MVII-1 and suggest that R. meliloti L5-30 has complex flagellar filaments. No extracellular structures other than these complex flagella were detected.…”

Sinorhizobial chemotaxis: a departure from the enterobacterial paradigm a aTo Professor Wolfram Heumann on his 87th birthday.

“…A new direction is taken up when some flagella switch to clockwise (cw) rotation, forcing the handedness and helical amplitude to change, which drives the bundle apart and causes the cell to tumble. Unlike E. coli, the soil bacterium S. meliloti is driven by rather rigid, righthanded helical filaments, which facilitate efficient swimming in a viscous environment (Go$ tz et al, 1982). Whereas the ' plain ' enterobacterial flagellar filaments are assembled from monomeric flagellin subunits, the ' complex ' rhizobial filaments consist of four related flagellin subunits that are assembled as functional heterodimers (Scharf et al, 2001).…”