Iron depletion affects nitrogenase activity and expression ofnifHandnifAgenes inHerbaspirillum seropedicae

Rosconi, Federico; Souza, Emanuel M.; Pedrosa, F. O.; Platero, Raúl; González, Cecilia; González, Marcela; Batista, Silvia; Gill, Paul R.; Fabiano, Elena

doi:10.1111/j.1574-6968.2006.00218.x

Cited by 13 publications

(9 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, a mutant of that gene was identified in a Tn mutant library previously described for the closely related strain H. seropedicae Z67 (39); this suggests that acnA (Hsero_2283) does not participate in the TCA cycle. Homologs of iscA (Hsero_3845 and Hsero_3142), a gene involved in Fe-S cluster biogenesis, were identified as essential genes.…”

Section: Resultsmentioning

confidence: 98%

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Rosconi

Vries

Baig

et al. 2016

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

The interior of plants contains microorganisms (referred to as endophytes) that are distinct from those present at the root surface or in the surrounding soil. Herbaspirillum seropedicae strain SmR1, belonging to the betaproteobacteria, is an endophyte that colonizes crops, including rice, maize, sugarcane, and sorghum. Different approaches have revealed genes and pathways regulated during the interactions of H. seropedicae with its plant hosts. However, functional genomic analysis of transposon (Tn) mutants has been hampered by the lack of genetic tools. Here we successfully employed a combination of in vivo high-density mariner Tn mutagenesis and targeted Tn insertion site sequencing (Tn-seq) in H. seropedicae SmR1. The analysis of multiple gene-saturating Tn libraries revealed that 395 genes are essential for the growth of H. seropedicae SmR1 in tryptone-yeast extract medium. A comparative analysis with the Database of Essential Genes (DEG) showed that 25 genes are uniquely essential in H. seropedicae SmR1. The Tn mutagenesis protocol developed and the gene-saturating Tn libraries generated will facilitate elucidation of the genetic mechanisms of the H. seropedicae endophytic lifestyle.IMPORTANCE A focal point in the study of endophytes is the development of effective biofertilizers that could help to reduce the input of agrochemicals in croplands. Besides the ability to promote plant growth, a good biofertilizer should be successful in colonizing its host and competing against the native microbiota. By using a systematic Tn-based gene-inactivation strategy and massively parallel sequencing of Tn insertion sites (Tn-seq), it is possible to study the fitness of thousands of Tn mutants in a single experiment. We have applied the combination of these techniques to the plant-growth-promoting endophyte Herbaspirillum seropedicae SmR1. The Tn mutant libraries generated will enable studies into the genetic mechanisms of H. seropedicae-plant interactions. The approach that we have taken is applicable to other plant-interacting bacteria.

show abstract

Section: Resultsmentioning

confidence: 98%

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Rosconi

Vries

Baig

et al. 2016

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Transposon mutagenesis was performed with an mTn 5gusA‐oriV‐pgfp (Rosconi et al ., 2006) using the procedures described by Xi and colleagues (1999). Lipopolysaccharide defective derivatives were identified by screening for mutants showing auto‐agglutination in PY liquid medium.…”

Section: Methodsmentioning

confidence: 99%

Mutations in lipopolysaccharide biosynthetic genes impair maize rhizosphere and root colonization of Rhizobium tropici CIAT899

Ormeño‐Orrillo

Rosenblueth

Luyten

et al. 2008

Environmental Microbiology

View full text Add to dashboard Cite

Three transposon mutants of Rhizobium tropici CIAT899 affected in lipopolysaccharide (LPS) biosynthesis were characterized and their maize rhizosphere and endophytic root colonization abilities were evaluated. The disrupted genes coded for the following putative products: the ATPase component of an O antigen ABC-2 type transporter (wzt), a nucleotide-sugar dehydratase (lpsbeta2) and a bifunctional enzyme producing GDP-mannose (noeJ). Electrophoretic analysis of affinity purified LPS showed that all mutants lacked the smooth LPS bands indicating an O antigen minus phenotype. In the noeJ mutant, the rough LPS band migrated faster than the parental band, suggesting a truncated LPS core. When inoculated individually, the wzt and noeJ mutants colonize the rhizosphere and root to a lower extent than the parental strain while no differences were observed between the lpsbeta2 mutant and the parental strain. All mutants were impaired in competitive rhizosphere and root colonization. Pleiotropic effects of the mutations on known colonization traits such as motility and growth rate were observed, but they were not sufficient to explain the colonization behaviours. It was found that the LPS mutants were sensitive to the maize antimicrobial 6-methoxy-2-benzoxazolinone (MBOA). Only the combined effects of altered growth rate and susceptibility to maize antimicrobials could account for all the observed colonization phenotypes. The results suggest an involvement of the LPS in protecting R. tropici against maize defence response during rhizosphere and root colonization.

show abstract

“…Long-term weathering of soils generally increases their extractable iron content (Arduino et al, 1986), while calcium carbonate content of soils nifH T-RFLP and ARISA, respectively. Lack of iron is known to affect nifH expression and nitrogenase activity in several diazotrophic microorganisms including K. pneumoniae (Miller & Orme-Johnson, 1992), C. anabaena (Fillat et al, 1995), and H. seropedicae (Rosconi et al, 2006). The difference in community structure between rhizosphere communities of the two host species is small, though statistically significant.…”

Section: Discussionmentioning

confidence: 99%

Edaphic correlates of feedstock‐associated diazotroph communities

2018

View full text Add to dashboard Cite

Miscanthus × giganteus and Panicum virgatum are potential promising bioenergy feedstock crops suitable for the temperate zone. The energy efficiency and sustainability of bioenergy production could be improved by reducing their fertilizer inputs – particularly energy intensive nitrogen fertilizers. Miscanthus is known to benefit from nitrogen fixation by associative diazotrophs. However, because the effects of edaphic‐, management‐, and plant‐related factors on feedstock‐associated diazotroph communities have not yet been characterized, it is not currently possible to optimize the nitrogen contribution to feedstock crops from associated diazotroph communities. To address this critical knowledge gap, we characterized the bacterial and diazotroph communities in the rhizosphere and endophytic compartments of both species at eight research sites across Illinois. We also quantified the nifH gene abundance in the rhizosphere soil as well as a range of soil chemistry parameters at these sites. Multivariate statistical analyses revealed that diazotroph and bacterial communities in the rhizosphere varied primarily among sites, with very small differences between host species. Conversely, diazotroph and bacterial communities in the endophytic compartments differed significantly between plant species, but did not vary substantially among sites. Finally, nifH gene abundance in the rhizospheres of both species varied substantially from site to site and was positively correlated with soil iron concentration as well as soil ammonium concentration, and negatively correlated with abundance of other soil nutrients including calcium, total nitrogen, and nitrates. These results indicate the potential edaphic drivers of associative diazotroph communities in feedstock rhizospheres and suggest that manipulating bioavailable iron content in the soil is a potential direction for investigating the optimization of these communities to improve their nitrogen contribution to crops.

show abstract

Iron depletion affects nitrogenase activity and expression ofnifHandnifAgenes inHerbaspirillum seropedicae

Cited by 13 publications

References 23 publications

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

Mutations in lipopolysaccharide biosynthetic genes impair maize rhizosphere and root colonization of Rhizobium tropici CIAT899

Edaphic correlates of feedstock‐associated diazotroph communities

Contact Info

Product

Resources

About