title: Effects of nutritional and environmental conditions on Sinorhizobium meliloti biofilm formation.
abstract: Rhizobia are non-spore-forming soil bacteria that fix atmospheric nitrogen into ammonia in a symbiosis with legume roots. However, in the absence of a legume host, rhizobia manage to survive and hence must have evolved strategies to adapt to diverse environmental conditions. The capacity to respond to variations in nutrient availability enables the persistence of rhizobial species in soil, and consequently improves their ability to colonize and to survive in the host plant. Rhizobia, like many other soil bacteria, persist in nature most likely in sessile communities known as biofilms, which are most often composed of multiple microbial species. We have been employing in vitro assays to study environmental parameters that might influence biofilm formation in the Medicago symbiont Sinorhizobium meliloti. These parameters include carbon source, amount of nitrate, phosphate, calcium and magnesium as well as the effects of osmolarity and pH. The microtiter plate assay facilitates the detection of subtle differences in rhizobial biofilms in response to these parameters, thereby providing insight into how environmental stress or nutritional status influences rhizobial survival. Nutrients such as sucrose, phosphate and calcium enhance biofilm formation as their concentrations increase, whereas extreme temperatures and pH negatively affect biofilm formation.
authors.affiliation: Departamento de Biología Molecular, Universidad Nacional de Río Cuarto, 5800-Río Cuarto, Córdoba, Argentina.
authors.forename: Luciana
authors.initials: L
authors.lastname: Rinaudi
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Fujishige
authors.forename: Ann M
authors.initials: AM
authors.lastname: Hirsch
authors.forename: Erika
authors.initials: E
authors.lastname: Banchio
authors.forename: Angeles
authors.initials: A
authors.lastname: Zorreguieta
authors.forename: Walter
authors.initials: W
authors.lastname: Giordano
mesh_terms: D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009566:Nitrates / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology; D016962:Sinorhizobium meliloti / Q000187:drug effects / Q000254:growth & development*; D012965:Sodium Chloride / Q000494:pharmacology; D013012:Sorbitol / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature
chemical_list: D003470:Culture Media; D009566:Nitrates; D010710:Phosphates; D012965:Sodium Chloride; D013012:Sorbitol; D013395:Sucrose; D008274:Magnesium; D002118:Calcium