INVESTIGADORES
ZORREGUIETA Angeles
artículos
Título:
A positive correlation between bacterial autoaggregation and biofilm formation in native Sinorhizobium meliloti isolates from Argentina.
Autor/es:
SORROCHE, F; SPESIA, MB; ZORREGUIETA, A; GIORDANO, W
Revista:
APPLIED AND ENVIRONMENTAL MICROBIOLOGY
Editorial:
AMER SOC MICROBIOLOGY
Referencias:
Lugar: Washington; Año: 2012 vol. 78 p. 4092 - 4101
ISSN:
0099-2240
Resumen:
Sinorhizobium meliloti is a symbiotic nitrogen-fixing bacterium that
elicits nodule formation on roots of alfalfa plants. S. meliloti
produces two exopolysaccharides (EPSs), termed EPS I and EPS II, that
are both able to promote symbiosis. EPS I and EPS II are secreted in two
major fractions that reflect differing degrees of subunit
polymerization, designated high- and low-molecular-weight fractions. We
reported previously that EPSs are crucial for autoaggregation and
biofilm formation in S. meliloti reference strains and isogenic mutants.
However, the previous observations were obtained by use of
"domesticated" laboratory strains, with mutations resulting from
successive passages under unnatural conditions, as has been documented
for reference strain Rm1021. In the present study, we analyzed the
autoaggregation and biofilm formation abilities of native S. meliloti
strains isolated from root nodules of alfalfa plants grown in four
regions of Argentina. 16S rRNA gene analysis of all the native isolates
revealed a high degree of identity with reference S. meliloti strains.
PCR analysis of the expR gene of all the isolates showed that, as in the
case of reference strain Rm8530, this gene is not interrupted by an
insertion sequence (IS) element. A positive correlation was found
between autoaggregation and biofilm formation abilities in these
rhizobia, indicating that both processes depend on the same physical
adhesive forces. Extracellular complementation experiments using mutants
of the native strains showed that autoaggregation was dependent on EPS
II production. Our results indicate that a functional EPS II synthetic
pathway and its proper regulation are essential for cell-cell
interactions and surface attachment of S. meliloti.