Isolation and characterization of lipopolysaccharides from different rhizobial isolates

Abstract

Formation of nodules on roots or in stems (in some cases) of leguminous plants is the unique ability of gram-negative bacteria, Rhizobia, which converts atmospheric nitrogen into usable forms by the host plant. Lipopolysaccharide (LPS) is the outer membrane component of the gram-negative bacteria, known to be an essential factor in host recognition, specificity, and initial infection processes. In the present study, we extracted lipopolysaccharides from different rhizobial isolates by a modified phenol-water method and partially characterized by polyacrylamide gel electrophoresis with silver staining. The results showed two separate banding regions, LPS-I and LPS-II. The high molecular weight and electrophoretic mobility of LPS-I region resembles that of lysozyme, used as a standard marker. The LPS-II region has a low molecular weight and electrophoretic mobility greater than that of lysozyme. The LPS-II region was due to incomplete LPS, which either lacks the entire O-antigen repeating unit or contains only one or two repeating units. The banding patterns of LPS vary among the different rhizobial isolates. Results revealed that the type of LPS structure and banding regions greatly facilitate the further characterization of the LPS modifications required for symbiosis.

Adaptive Divergence in Experimental Populations ofPseudomonas fluorescens. V. Insight into the Niche Specialist Fuzzy Spreader Compels Revision of the ModelPseudomonasRadiation

“…Indeed, O antigen is essential for the establishment of infection (or protection against host defenses) in a diverse array of plant and animal pathogens (Cava et al 1989;Dekkers et al 1998;Yang et al 2000;Kannenberg and Carlson 2001;Poon et al 2008;Kesawat et al 2009); moreover, the O antigen serves as a receptor for phages (Michel et al 2010;Filippov et al 2011;Garbe et al 2011;Shin et al 2012). Thus it would appear that O antigens are subject to two conflicting selective pressures: pressure to change to avoid phage predation and pressure to be maintained to enable colonization of host species during infection.…”

Lipopolysaccharides in diazotrophic bacteria

“…Among all diazotrophic bacteria, those belonging to the family Rhizobiaceae have certainly the greater number of species studied in regards to their LPS. Extensive work has been done on structural characterization, biosynthesis and involvement of LPS during Rhizobia-legume interaction (Carlson et al, 1999 , 2010 ; Price, 1999 ; Noel and Duelli, 2000 ; Fraysse et al, 2003 ; Kesawat et al, 2009 ). Lipid and monosaccharide composition in LPS found for Rhizobiaceae vary considerably, but the basic architecture for this molecule is conserved (Kannenberg et al, 1998 ).…”