Characterization of Herbaspirillum seropedicae gen. nov., sp. nov., a Root-Associated Nitrogen-Fixing Bacterium

Abstract

During a survey of the occurrence of Azospirillum spp. in cereal roots, we obtained 119 isolates which could not be identified as members of one of the three previously described Azospirillum species. These strains formed a very homogeneous group of N2-fixing, microaerobic, motile, vibrioid, gram-negative rod-shaped organisms which formed a veillike pellicle in semisolid medium similar to that of Azospirillum spp. However, the new isolates differed from Azospirillum spp. by their smaller cell width (0.6 to 0.7 pm), variable flagellation (one to three flagella on one or both poles), moist brownish colonies, and broader pH and oxygen tolerance for nitrogenase activity. Organic acids were the preferred carbon sources, but glucose, galactose, L-arabinose, mannitol, sorbitol, and glycerol were also used. The guanine-plus-cytosine content of the deoxyribonucleic acid was slightly lower than the guanine-plus-cytosine contents of Azospirillum spp. (66 to 67 mol%). Deoxyribonucleic acid hybridization experiments with 17 strains of the group showed 50 to 100% complementarity, while the levels of hybridization with the type strains of Azospirillum brasilense, Azospirillum lipuferum, and Azospirillum amazonense were 23, 15, and 6%, respectively. For these new isolates we propose a new genus, Herbaspirillum (the name refers to the habitat of the orgahisms, the roots of cereals, which are herbaceous seed-bearing plants). The type species is named Herbaspirillum seropedicae after the place where it was first isolated. The type strain is strain 267, which has been deposited in the American Type Culture Collection as strain ATCC 35892.

Identification and isolation of active N2O reducers in rice paddy soil

“…Herbaspirillum strains were previously shown to be involved in nitrate reduction of rice paddy soil (Ishii et al, 2009b, but the present study showed that they are also important players in N 2 O reduction. Although some Herbaspirillum species (for example, Herbaspirillum seropedica) can colonize rice roots and stems and fix atmospheric N 2 (Baldani et al, 1986;Elbertagy et al, 2001), almost all strains obtained in this study did not show N 2 -fixing ability (S. Ishii, unpublished data). In addition, 16S rRNA gene similarities between the Herbaspiriilum strains obtained in this study and other Herbaspirillum species were o97%.…”

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

“…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.…”

Caracterização fenotípica e diversidade de bactérias diazotróficas associativas isoladas de solos em reabilitação após a mineração de bauxita

“…Tal diversidade garante não só a resiliência da FBN nos ecossistemas, como também a ocorrência deste processo nos mais diferentes habitats terrestres (Moreira & Siqueira, 2002). Em geral, espécies de bactérias diazotróficas associativas têm sido isoladas de raízes e partes aéreas de gramíneas de pastagem e de grãos (Magalhães & Döbereiner, 1984;Baldani et al, 1986;Döbereiner, 1992;Baldani, 1996;Dicello et al, 1997, Eckert et al, 2001, de tubérculos (Balota et al, 1997), cafeeiros (Santos et al, 2001) e fruteiras (Magalhães & Döbereiner, 1984;Weber et al, 2001).…”