title: Influence of substrate composition and flow rate on growth of Azospirillum brasilense Cd in a co-culture with 3 sorghum rhizobacteria.
abstract: The ability of Azospirillum brasilense Cd to colonize the niche occupied by 3 bacterial strains previously isolated from sorghum rhizosphere was studied by means of the Biolog system. The isolates were identified by different methods as strains belonging to Pseudomonas putida, Stenotrophomonas maltophilia, and Klebsiella terrigena species. Several C sources, also chosen among the constituents of sorghum root exudates, were used to evaluate the metabolic profiles of Azospirillum and the sorghum rhizobacteria. Azospirillum brasilense Cd exploited the same class of C compounds as the sorghum rhizobacteria and overlapped in their niche requirements. Since structure and functioning of a microbial community are largely affected by the flow rate of nutrient supply, the competitive behavior of A. brasilense Cd was studied in a chemostat mixed culture under C-limited conditions using disodium succinate as C source. Only at high growth rates, i.e., when the C source was highly supplied, A. brasilense Cd appeared to be a good competitor and it became the dominant species, whereas at low growth rates, it was outnumbered by the other species. However, the coexistence of all the strains was always maintained, thus suggesting that interactions other than competition or a potential cross-feeding might occur within the mixed culture.
authors.affiliation: Istituto di Biologia Agroambientale e Forestale, Consiglio Nazionale delle Ricerche, Area della Ricerca di Roma, Via Salaria Km. 29,300, 00016 Monterotondo Scalo, Rome, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Lippi
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: De Paolis
authors.forename: Elena
authors.initials: E
authors.lastname: Di Mattia
authors.forename: Tito
authors.initials: T
authors.lastname: Pietrosanti
authors.forename: Isabella
authors.initials: I
authors.lastname: Cacciari
mesh_terms: D000596:Amino Acids / Q000302:isolation & purification / Q000378:metabolism; D015806:Azospirillum brasilense / Q000254:growth & development* / Q000378:metabolism; D018533:Biomass; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000302:isolation & purification; D002264:Carboxylic Acids / Q000302:isolation & purification / Q000378:metabolism; D018920:Coculture Techniques; D015169:Colony Count, Microbial; D007709:Klebsiella / Q000254:growth & development* / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry / Q000378:metabolism; D016958:Pseudomonas putida / Q000254:growth & development* / Q000302:isolation & purification; D012988:Soil Microbiology; D045868:Sorghum / Q000382:microbiology*; D020615:Stenotrophomonas maltophilia / Q000254:growth & development* / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D002264:Carboxylic Acids; D010936:Plant Extracts