Chemical and serological studies of liposaccharides of bacteria of the genus Azospirillum

Konnova, O. N.; Boiko, Anastasiia S.; Burygin, Gennady L.; Fedonenko, Yu. P.; Matora, L. Yu.; Коннова, С. А.; Игнатов, В. В.

doi:10.1134/s0026261708030090

Cited by 25 publications

(14 citation statements)

References 16 publications

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“…This switch from smooth (S) to rough (R) colonies occurs in several Gram-negative mutants that fail to add the O-antigen portion to the LPS (Kustos et al, 2000a, b;Godowski, 2005;Wolf & Goldberg, 2006). However, from our study, we cannot conclude that Wzm is involved in O-antigen export in A. brasilense, as we were not able to detect in the mutant the intermediate molecular mass band that is typical of the A. brasilense Sp7 R-LPS, consisting of lipid A and core oligosaccharide (Konnova et al, 2008). Therefore, the LPS profile of the mutant strain, characterized by diffuse, low-molecular-mass bands, suggests that in A. brasilense, Wzm could also be involved in export of the core oligosaccharide.…”

Section: Discussioncontrasting

confidence: 52%

“…Similarly sized bands have been observed in other LPS studies of A. brasilense strains, including with strain Sp7 (Katzy et al, 1998;Konnova et al, 2008). These bands (arrows 1 and 2, respectively) have been shown to correspond to the smooth-LPS (containing lipid A, core oligosaccharide and O-antigen) and rough-LPS (lacking the O-antigen part) (Konnova et al, 2008). In contrast to the wild-type, the wzm mutant pattern showed diffuse bands of lower molecular mass (Fig.…”

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confidence: 84%

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The wzm gene located on the pRhico plasmid of Azospirillum brasilense Sp7 is involved in lipopolysaccharide synthesis

2009

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Several genes involved in the interaction between Azospirillum brasilense Sp7 and plants are located on the pRhico plasmid. Here we report the characterization of an Sp7 mutant strain with impairment of the pRhico-located gene wzm. This gene encodes an inner-membrane component of an ATP-binding cassette (ABC) transporter with similarity to transporters involved in surface polysaccharide export. Indeed, SDS-PAGE revealed that LPS synthesis is affected in the wzm mutant. No significant differences were observed between wild-type and mutant strains in exopolysaccharide (EPS) amount; however, several differences were observed between them in EPS monosaccharide composition, and only wild-type colonies stained positively with Congo red. Microscopy revealed that wzm mutant cells are longer and thinner, and exhibit several differences in their cell surface relative to the wild-type. The wzm mutant was more resistant to oxidative stress, starvation, desiccation, heat and osmotic shock than the wild-type. In contrast, the mutant was more susceptible than the wild-type to UV radiation and saline stress. The strains also differed in their susceptibility to different antibiotics. Differences between the strains were also observed in their outer-membrane protein composition. No differences were observed between strains in their ability to attach to sweet corn roots and seeds, and to promote growth under the tested conditions. As LPS plays an important role in cell envelope structural integrity, we propose that the pleiotropic phenotypic changes observed in the wzm mutant are due to its altered LPS relative to the wild-type. INTRODUCTIONThe Azospirillum genus belongs to the alpha-proteobacteria and comprises free-living, nitrogen-fixing, vibrio-or spirillum-shaped rods that exert beneficial effects on plant growth and yield of many crops of agronomic importance (Dobbelaere et al., 2001). Plant growth promotion by Azospirillum is attributed to morphological and physiological changes in inoculated plant roots, which enhance water and mineral uptake. Plant growth substances, such as auxins, cytokinins and gibberellins (Steenhoudt & Vanderleyden, 2000;Dobbelaere et al., 2001), as well as nitric oxide (Creus et al., 2005) produced by the bacteria are at least partially responsible for the plant growth promotion.Within the Azospirillum genus, one of the most studied species is Azospirillum brasilense (Tarrand et al., 1978). A. brasilense cells are surrounded by a dense, tightly cellbound layer of capsular polysaccharides (CPSs), and by outer exopolysaccharides (EPSs), which are loosely bound to the cell and easily detached by centrifugation (Burdman et al., 2000c). EPSs and CPSs, as well as extracellular proteins, have been shown to play important roles in bacterial aggregation and in the establishment of the bacterium-plant association (Burdman et al., 1999(Burdman et al., , 2000cSteenhoudt & Vanderleyden, 2000). It has been suggested that EPSs and CPSs are involved in anchoring the bacteria to the surface of wheat roots , and in t...

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Section: Discussioncontrasting

confidence: 52%

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confidence: 84%

The wzm gene located on the pRhico plasmid of Azospirillum brasilense Sp7 is involved in lipopolysaccharide synthesis

2009

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“…Clear differences in LPS profiles were found between the three strains. While the wild-type pattern showed both high-and low-molecular-weight bands (HMW and LMW, respectively) typical of this strain (Katzy et al, 1998;Vanbleu et al, 2005;Konnova et al, 2008;Lerner et al, 2009), only an LMW band was detected in the LPS pattern of the noeJ mutant (Fig. 2).…”

Section: Analyses Of Lps and Eps Of Noej And Noel Mutantsmentioning

confidence: 99%

The Azospirillum brasilense Sp7 noeJ and noeL genes are involved in extracellular polysaccharide biosynthesis

et al. 2009

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The Azospirillum brasilense Sp7 noeJ and noeL genes are involved in extracellular polysaccharide biosynthesis Azospirillum brasilense is a plant root-colonizing bacterium that exerts beneficial effects on the growth of many agricultural crops. Extracellular polysaccharides of the bacterium play an important role in its interactions with plant roots. The pRhico plasmid of A. brasilense Sp7, also named p90, carries several genes involved in synthesis and export of cell surface polysaccharides. We generated two Sp7 mutants impaired in two pRhico-located genes, noeJ and noeL, encoding mannose-6-phosphate isomerase and GDP-mannose 4,6-dehydratase, respectively. Our results demonstrate that in A. brasilense Sp7, noeJ and noeL are involved in lipopolysaccharide and exopolysaccharide synthesis. noeJ and noeL mutant strains were significantly altered in their outer membrane and cytoplasmic/periplasmic protein profiles relative to the wild-type strain. Moreover, both noeJ and noeL mutations significantly affected the bacterial responses to several stresses and antimicrobial compounds. Disruption of noeL, but not noeJ, affected the ability of the A. brasilense Sp7 to form biofilms. The pleiotropic alterations observed in the mutants could be due, at least partially, to their altered lipopolysaccharides and exopolysaccharides relative to the wild-type.

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“…The typical high‐molecular‐weight LPS (HMW‐LPS; Fig. 1, upper arrow), which is commonly observed in LPS profiles of A. brasilense strains (Konnova et al. , 2008; Lerner et al.…”

Section: Resultsmentioning

confidence: 99%

Phenotypic variation in Azospirillum brasilense exposed to starvation

Lerner

Valverde

Castro‐Sowinski

et al. 2010

Environ Microbiol Rep

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Bacteria have developed mechanisms that allow them maintaining cell viability during starvation and resuming growth when nutrients become available. Among these mechanisms are adaptive mutations and phase variation, which are often associated with DNA rearrangements. Azospirillum brasilense is a Gram-negative, nitrogen-fixing, plant growth-promoting rhizobacterium. Here we report phenotypic variants of A. brasilense that were collected after exposure to prolonged starvation or after re-isolation from maize roots. The variants differed in several features from the parental strains, including pigmentation, aggregation ability, EPS amount and composition and LPS structure. One of the phenotypic variants, overproducing EPS and showing an altered LPS structure, was further characterized and showed differential response to several stresses and antibiotics relative to its parental strain. Characterization of the variants by repetitive-PCR revealed that phenotypic variation was often associated with DNA rearrangements.

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Chemical and serological studies of liposaccharides of bacteria of the genus Azospirillum

Cited by 25 publications

References 16 publications

The wzm gene located on the pRhico plasmid of Azospirillum brasilense Sp7 is involved in lipopolysaccharide synthesis

The wzm gene located on the pRhico plasmid of Azospirillum brasilense Sp7 is involved in lipopolysaccharide synthesis

The Azospirillum brasilense Sp7 noeJ and noeL genes are involved in extracellular polysaccharide biosynthesis

Phenotypic variation in Azospirillum brasilense exposed to starvation

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