Herbaspirillum lusitanum sp. nov., a novel nitrogen-fixing bacterium associated with root nodules of Phaseolus vulgaris.
Several bacterial strains were isolated from root nodules of Phaseolus vulgaris plants grown in a soil from Portugal. The strains were Gram-negative, aerobic, curved rod-shaped and motile. The isolates were catalase- and oxidase-positive. The TP-RAPD (two-primer randomly amplified polymorphic DNA) patterns of all strains were identical, suggesting that they belong to the same species. The complete 16S rDNA sequence of a representative strain was obtained and phylogenetic analysis based on the neighbour-joining method indicated that this bacterium belongs to the beta-Proteobacteria and that the closest related genus is Herbaspirillum. The DNA G+C content ranged from 57.9 to 61.9 mol%. Growth was observed with many different carbohydrates and organic acids including caprate, malate, citrate and phenylacetate. No growth was observed with maltose, meso-inositol, meso-erythritol or adipate as sole carbon source. According to the phenotypic and genotypic data obtained in this work, the bacterium represents a novel species of the genus Herbaspirillum, and the name Herbaspirillum lusitanum sp. nov. is proposed. The type strain is P6-12(T) (=LMG 21710(T)=CECT 5661(T)). (+info)
Herbaspirillum chlorophenolicum sp. nov., a 4-chlorophenol-degrading bacterium.
A 4-chlorophenol-degrading bacterial strain, formerly designated as a strain of Comamonas testosteroni, was reclassified as a member of the genus Herbaspirillum based on its phenotypic and chemotaxonomic characteristics, as well as phylogenetic analysis using 16S rDNA sequences. Phylogenetic inference based on 16S rDNA sequences showed that strain CPW301(T) clusters in a phylogenetic branch that contains Herbaspirillum species. 16S rDNA sequence similarity of strain CPW301(T) to species of the genus Herbaspirillum with validly published names is in the range 98.7-98.9 %. Despite the considerably high 16S rDNA sequence similarity, strain CPW301(T) could be distinguished clearly from type strains of Herbaspirillum species with validly published names by DNA-DNA relatedness values, which were <15.7 %. The genomic DNA G+C content of strain CPW301(T) is 61.3 mol%. The predominant ubiquinone is Q-8 and the major cellular fatty acids are C(16 : 0) and cyclo-C(17 : 0). The strain does not fix nitrogen and is not plant-associated. It is an aerobic rod with one unipolar flagellum. On the basis of these characteristics, a novel Herbaspirillum species, Herbaspirillum chlorophenolicum sp. nov., is proposed. The type strain of the novel species is strain CPW301(T) (=KCTC 12096(T)=IAM 15024(T)). (+info)
Proposals of Curvibacter gracilis gen. nov., sp. nov. and Herbaspirillum putei sp. nov. for bacterial strains isolated from well water and reclassification of [Pseudomonas] huttiensis, [Pseudomonas] lanceolata, [Aquaspirillum] delicatum and [Aquaspirillum] autotrophicum as Herbaspirillum huttiense comb. nov., Curvibacter lanceolatus comb. nov., Curvibacter delicatus comb. nov. and Herbaspirillum autotrophicum comb. nov.
Two strains of curved bacteria, 7-1(T) and 7-2(T), isolated from well water, were phylogenetically examined to determine their taxonomic position. Strain 7-1(T) is a Gram-negative, slightly curved rod. Analysis of the 16S rRNA gene sequence showed that strain 7-1(T) formed a cluster with [Aquaspirillum] delicatum and [Pseudomonas] lanceolata. It has some similar characteristics to [A.] delicatum and [P.] lanceolata, but has sufficient distance to separate it from other genera. DNA-DNA hybridization analysis, as well as chemotaxonomic and morphological studies, demonstrated that strain 7-1(T), [A.] delicatum and [P.] lanceolata belong to a new genus, Curvibacter gen. nov. Strain 7-1(T) (=IAM 15033(T)=ATCC BAA-807(T)) is classified as the type strain of Curvibacter gracilis gen. nov., sp. nov., and [A.] delicatum and [P.] lanceolata are classified as Curvibacter delicatus comb. nov. and Curvibacter lanceolatus comb. nov., respectively. Strain 7-2(T) is a Gram-negative spirillum. Phylogenetic study based on the 16S rRNA gene sequences showed that it formed a cluster with the members of the genus Herbaspirillum, [Pseudomonas] huttiensis and [Aquaspirillum] autotrophicum. The classification is therefore proposed of strain 7-2(T) (=IAM 15032(T)=ATCC BAA-806(T)) as the type strain of Herbaspirillum putei sp. nov., and [P.] huttiensis and [A.] autotrophicum are transferred to the genus Herbaspirillum as Herbaspirillum huttiense comb. nov. and Herbaspirillum autotrophicum comb. nov., respectively. (+info)
Three stages of a biofilm community developing at the liquid-liquid interface between polychlorinated biphenyls and water.
Soil contaminated with polychlorinated biphenyls (PCB) was used as an inoculum to grow a complex biofilm community on PCB oil (Aroclor 1242) on a substratum (Permanox). The biofilm was monitored for 31 days by confocal laser scanning microscopy, community fingerprinting using single-strand conformational polymorphism (SSCP), amplicons of the 16S rRNA genes, and chemical analyses of the PCB congeners. SSCP analysis of the young biofilm revealed a rather diverse microbial community with species of the genera Herbaspirillum and Bradyrhizobium as dominant members. The biofilm developing on the PCB droplets displayed pronounced stages of PCB degradation and biofilm development not described before from pure-culture experiments. The first step was the colonization of the substratum while the PCB oil was hardly populated. When a certain density of bacteria was reached on the Permanox, the PCB was colonized, but soon the degradation of the congeners was markedly reduced and many cells were damaged, as seen by LIVE/DEAD staining. Finally, the biofilm formed aggregates and invaded the PCB oil, showing lower numbers of damaged cells than before and a dramatic increase in PCB degradation. This sequence of biofilm formation is understood as a maturation process prior to PCB oil colonization. This is followed by a thin biofilm on the PCB droplet, an aggregation process forming pockets in the PCB, and finally an invasion of the biofilm into the PCB oil. Only the mature biofilm showed degradation of pentachlorinated PCB congeners, which may be reductively dechlorinated and the resulting trichlorobiphenyls then aerobically metabolized. (+info)
Expression of the nifH gene of a Herbaspirillum endophyte in wild rice species: daily rhythm during the light-dark cycle.
The expression of nitrogenase genes of Herbaspirillum sp. B501 associated in shoot (leaf and stem) of wild rice, Oryza officinalis, was studied by means of reverse transcription-PCR (RT-PCR) targeted at the nifH gene. RT-PCR analyses indicate that nifH transcript was detected exclusively from nitrogen-fixing cells of gfp-tagged strain B501gfp1 in both free-living and endophytic states by using a constitutive gfp gene transcript as a positive control. Transcription of nifH and nitrogen fixation in free-living cells were induced maximally at a 2% O2 concentration and repressed in free air (21% O2). nifH transcription was monitored in the endophytic cells by using total RNA extracted from B501gfp1-inoculated wild rice plants during daily light-dark cycles. The level of nifH transcription in planta varied dramatically, with a maximum during the light period. Moreover, the light radiation enhanced nifH expression even in free-living cells grown in culture. These results suggest that in planta nitrogen fixation by the endophyte shows a daily rhythm determined by the plant's light environment. (+info)
Herbaspirillum hiltneri sp. nov., isolated from surface-sterilized wheat roots.
The genus Herbaspirillum of the Betaproteobacteria mainly comprises diazotrophic bacteria with a potential for endophytic and systemic colonization of a variety of plants. The plant-associated bacterial isolates N3(T), N5 and N9 were derived from surface-sterilized wheat roots. After phylogenetic analysis of 16S rRNA gene sequence data the isolates could be allocated to the genus Herbaspirillum, and 99.9 % similarity to the sequence of Herbaspirillum lusitanum P6-12(T) was found. A set of 16S rRNA gene-targeted oligonucleotide probes was developed for the identification of the three novel isolates and H. lusitanum (Hhilu446), and for the specific detection of several other Herbaspirillum species described recently. For higher phylogenetic resolution, the 23S rRNA gene sequences of all members of the genus was sequenced and used to construct a phylogenetic tree. Isolates N3(T), N5 and N9 formed a group that was distinct from all other Herbaspirillum species. In addition, isolate N3(T) and H. lusitanum P6-12(T) exhibited a DNA-DNA hybridization value of only 25 %. The value for DNA-DNA hybridization between N3(T) and other members of the genus Herbaspirillum was between 14 and 32 %; DNA-DNA hybridization between strain N3(T) and isolates N5 and N9 produced values above 95 %. This places the three isolates as representatives of a novel species within the genus Herbaspirillum. A Biolog GN2 assay supported this conclusion. The major fatty acids were C(16 : 1)omega7c, C(16 : 0) and C(18 : 1)omega7c, and the DNA G+C content ranged from 60.9 to 61.5 mol%. Therefore these three isolates should be classified within a novel species, for which the name Herbaspirillum hiltneri sp. nov. is proposed. The type strain is N3(T) (=DSM 17495(T)=LMG 23131(T)). (+info)
N-fertilizer saving by the inoculation of Gluconacetobacter diazotrophicus and Herbaspirillum sp. in micropropagated sugarcane plants.
Colonization of micropropagated sugarcane plants by Gluconacetobacter diazotrophicus and Herbaspirillum sp. was confirmed by a dot-immunoblot assay. In all, a 45-day short-term and 180-day long-term experiments conducted on micropropagated sugarcane plants of Co 86032, a sugar rich popular variety in South India, indicated the usefulness of these diazotrophs as plant growth promoting bacteria. Co-inoculation of these two bacteria enhanced the biomass considerably under N-limited condition in the short duration experiment. In the long-term experiment, the establishment of inoculated Herbaspirillum sp. remained stable with the age of the crop up to 180 days, while there was a reduction in population of G. diazotrophicus for the same period. The total bio-mass and leaf N were higher in plants inoculated with G. diazotrophicus and Herbaspirillum sp. without N fertilization and also in plants with 50% of the recommended N (140 kg ha(-1)) than the plants fertilized with recommended dose of inorganic N (280 kg ha(-1)). This experiment showed that inoculation with these bacteria in sugarcane variety Co 86032 could mitigate fertilizer N application considerably in sugarcane cultivation. (+info)
Members of the ethylene signalling pathway are regulated in sugarcane during the association with nitrogen-fixing endophytic bacteria.
Nitrogen-fixing bacteria have been isolated from sugarcane in an endophytic and beneficial interaction that promotes plant growth. In this work, for the first time, the involvement of ethylene signalling in this interaction was investigated by molecular characterizing members of this pathway in sugarcane. The expression pattern of a putative ethylene receptor (SCER1) and two putative ERF transcription factors (SCERF1 and SCERF2) show exclusive modulation in plants inoculated with the diazotrophic endophytes. The gene expression profile of SCER1, SCERF1, and SCERF2 is differentially regulated in sugarcane genotypes that can establish efficient or inefficient associations with diazotrophic micro-organisms, exhibiting high or low biological nitrogen fixation (BNF) rates, respectively. In addition, SCER1, SCERF1, and SCERF2 expression is different in response to interactions with pathogenic and beneficial micro-organisms. Taken together, that data suggest that SCER1, SCERF1, and SCERF2 might participate in specific ethylene signalling cascade(s) that can identify a beneficial endophytic association, modulating sugarcane responses toward the diazotrophic endophytes. (+info)