A new acid-tolerant nitrogen-fixing bacterium associated with sugarcane

Abstract

During surveys of bacteria possibly responsible for N 2 fixation in sugarcane, root and stem samples were collected in four sugarcane-growing regions in Brazil. A new microaerobic N 2-fixing bacterium was isolated from most samples of washed roots and stems from all regions. Isolation procedures were based on semisolid diluted sugarcane juice medium followed by replication to N-free 10% sugar medium acidified with acetic acid to pH 4.5. The new bacterium is an aerobic rod, motile by 1 to 3 lateral flagella, fixes N2 in semisolid media under air but not in liquid media except when a starter dose of N is added. It has no nitrate reductase and N2 fixation proceeds in the presence of 10mM NO~-. Best growth occurs with high sucrose concentrations (10%). Growth occurs up to 30% sucrose but not at 35%. Acid is formed reaching a final pH of below 3.0. Growth and Nz fixation proceed at this acidity. Ethanol is used for growth and is "overoxidised" (oxidized to CO2 and H20). Acetic and lactic acids are also oxidized to CO2 and H20. Acids produced from glucose are consumed with precipitation of CaCO3. Dark brown colonies are formed on potato agar with 10% sugar and dark orange colonies on N poor agar (20mg yeast extract per 1) containing bromothymol blue. In view of the distinct characteristics which do not allow identification within either Frateuria, Gluconobacter, Acetobacter or any known Nz-fixing bacterium a new genus and species are proposed and named Saccharobacter nitrocaptans.

Relação entre distribuição de nitrogênio e colonização por bactérias diazotróficas em cana-de-açúcar

“…Entre outras bactérias associadas à canade-açúcar, responsáveis pela FBN, destacam-se as espécies Gluconacetobacter diazotrophicus e Herbaspirillum spp. G. diazotrophicus está inserida no grupo das bactérias do ácido acético e foi isolada de raízes e parte aérea de cana-de-açúcar por Cavalcante & Döbereiner (1988). Já as bactérias do gênero Herbaspirillum são naturalmente associadas às gramíneas e aí se incluem as espécies H. seropedicae e H. rubrisubalbicans (Baldani et al, 1986(Baldani et al, , 1996.…”

Azide resistant mutants ofAcetobacterdiazotrophicusandAzospirillum brasilenseincrease yield and nitrogen content of cotton

“…Seeds of two cotton cultivars, namely Gossypium hirsutum cv H117 and G. herbaceum cv HD-123, were obtained from the Cotton Section, Department of Plant Breeding, CCSHAU, Hisar. Semi solid N-free medium (LGI medium, Cavalcante & Doberenier 1988) was used for isolation of Acetobacter and for testing resistance to sodium azide, while malate medium (Sadasivan & Neyra 1995) was used for culturing and isolation of mutants of A. brasilense . Isolated azide resistant mutants were further investigated by spotting on their respective culture media containing a particular concentration of azide.…”

Isolation and screening of nitrogen fixing endophytic bacterium

“…N-free semisolid LGI medium supplemented with 0.5% sugarcane juice at pH 4.5 was used (Cavalcante and Dobereiner, 1988). For isolation and culturing, acetic acid LGI agar plates supplemented with yeast extract (50 mg /1) and potato agar plates with 10% cane sugar were used (Cavalcante and Dobereiner, 1988).…”

“…Gluconacetobacter diazotrophicus is an endophytic bacterium first isolated from the sugarcane growing regions of Brazil (Cavalcante and Dobereiner, 1988). It was widely studied and used as a model system to assess the bacterial endophyte -plant interactions.…”