Sinorhizobium meliloti growing on soft agar can exhibit an unusual surface spreading behaviour that differs from other bacterial surface motilities. Bacteria in the colony secrete an exopolysaccharide-rich mucoid fluid that expands outward on the surface, carrying within it a suspension of actively dividing cells. The moving slime disperses the cells in complex and dynamic patterns indicative o...

The expression of phenotypic variability can enhance geometric mean fitness and act as a bet-hedging strategy in unpredictable environments. Metazoan bet hedging usually involves phenotypic diversification among an individual's offspring, such as differences in seed dormancy. Virtually all known microbial bet-hedging strategies, in contrast, rely on low-probability stochastic switching of a her...

In nitrogen-fixing symbiosis, plant sanctions against ineffective bacteria have been demonstrated in previous studies performed on soybean and yellow bush lupin, both developing determinate nodules with Bradyrhizobium sp. strains. In this study, we focused on the widely studied symbiotic association Medicago truncatula-Sinorhizobium meliloti, which forms indeterminate nodules. Using two strains...

Hemoglobins (Hbs) have been characterized from a wide variety of eubacteria, but not from nitrogen-fixing rhizobia. Our search for Hb-like sequences in the Sinorhizobium meliloti genome revealed that a gene coding for a flavohemoglobin (fHb) exists in S. meliloti (SmfHb). Computer analysis showed that SmfHb and Alcaligenes eutrophus fHb are highly similar and could fold into the same tertiary s...

To evaluate the role of uridylyl-transferase, the Sinorhizobium meliloti glnD gene was isolated by heterologous complementation in Azotobacter vinelandii. The glnD gene is cotranscribed with a gene homologous to Salmonella mviN. glnD1::Omega or mviN1::Omega mutants could not be isolated by a powerful sucrose counterselection procedure unless a complementing cosmid was provided, indicating that ...

Sinorhizobium fredii GR64 is a peculiar strain that is able to effectively nodulate bean but not soybean, the common host of S. fredii. Here we present the draft genome of S. fredii GR64. This information will contribute to a better understanding of the symbiotic rhizobium-plant interaction and of rhizobial evolution.

Bacterial surface components, especially exopolysaccharides, in combination with bacterial Quorum Sensing signals are crucial for the formation of biofilms in most species studied so far. Biofilm formation allows soil bacteria to colonize their surrounding habitat and survive common environmental stresses such as desiccation and nutrient limitation. This mode of life is often essential for surv...

The induction of root nodules by the majority of rhizobia has a strict requirement for the secretion of symbiosis-specific lipochitooligosaccharides (nodulation factors [NFs]). The nature of the chemical substitution on the NFs depends on the particular rhizobium and contributes to the host specificity imparted by the NFs. We present here a description of the genetic organization of the nod gen...

288 time to identify the carbohydrate-bearing structures. Recent examples of glycoproteins originally detected with lectins that have now been identified are desmosomal glycoproteins [ 151 and integrins [ 161. Changes in the carbohydrate moieties of adhesion molecules can alter their function [ 17-19] and thus the lectin patterns may turn out to provide new insights into the changes in the adhe...