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1.
Microbiology (Reading) ; 162(3): 552-563, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26813656

ABSTRACT

In Gram-negative bacteria, tyrosine phosphorylation has been shown to play a role in the control of exopolysaccharide (EPS) production. This study demonstrated that the chromosomal ORF SMc02309 from Sinorhizobium meliloti 2011 encodes a protein with significant sequence similarity to low molecular mass protein-tyrosine phosphatases (LMW-PTPs), such as the Escherichia coli Wzb. Unlike other well-characterized EPS biosynthesis gene clusters, which contain neighbouring LMW-PTPs and kinase, the S. meliloti succinoglycan (EPS I) gene cluster located on megaplasmid pSymB does not encode a phosphatase. Biochemical assays revealed that the SMc02309 protein hydrolyses p-nitrophenyl phosphate (p-NPP) with kinetic parameters similar to other bacterial LMW-PTPs. Furthermore, we show evidence that SMc02309 is not the LMW-PTP of the bacterial tyrosine-kinase (BY-kinase) ExoP. Nevertheless, ExoN, a UDP-glucose pyrophosphorylase involved in the first stages of EPS I biosynthesis, is phosphorylated at tyrosine residues and constitutes an endogenous substrate of the SMc02309 protein. Additionally, we show that the UDP-glucose pyrophosphorylase activity is modulated by SMc02309-mediated tyrosine dephosphorylation. Moreover, a mutation in the SMc02309 gene decreases EPS I production and delays nodulation on Medicago sativa roots.


Subject(s)
Polysaccharides, Bacterial/biosynthesis , Protein Tyrosine Phosphatases/metabolism , Sinorhizobium meliloti/enzymology , Sinorhizobium meliloti/metabolism , UTP-Glucose-1-Phosphate Uridylyltransferase/metabolism , Medicago sativa/microbiology , Plant Root Nodulation , Plant Roots/microbiology
2.
Genome Announc ; 3(2)2015 Mar 26.
Article in English | MEDLINE | ID: mdl-25814613

ABSTRACT

Pseudomonas fluorescens SF4c and SF39a, strains isolated from wheat rhizosphere, have potential applications in plant growth promotion and biocontrol of fungal diseases of crop plants. We report the draft genome sequences of SF4c and SF39a with estimated sizes of 6.5 Mb and 5.9 Mb, respectively.

3.
Antonie Van Leeuwenhoek ; 97(3): 241-51, 2010 Mar.
Article in English | MEDLINE | ID: mdl-20020326

ABSTRACT

Survival of Pseudomonas sp. SF4c and Pseudomonas sp. SF10b (two plant-growth-promoting bacteria isolated from wheat rhizosphere) was investigated in microcosms. Spontaneous rifampicin-resistant mutants derived from these strains (showing both growth rate and viability comparable to the wild-strains) were used to monitor the strains in bulk soil and wheat rhizosphere. Studies were carried out for 60 days in pots containing non-sterile fertilized or non-fertilized soil. The number of viable cells of both mutant strains declined during the first days but then became established in the wheat rhizosphere at an appropriate cell density in both kinds of soil. Survival of the strains was better in the rhizosphere than in the bulk soil. Finally, the antagonism of Pseudomonas spp. against phytopatogenic fungi was evaluated in vitro. Both strains inhibited the mycelial growth (or the resistance structures) of some of the phytopathogenic fungi tested, though variation in this antagonism was observed in different media. This inhibition could be due to the production of extracellular enzymes, hydrogen cyanide or siderophores, signifying that these microorganisms might be applied in agriculture to minimize the utilization of chemical pesticides and fertilizers.


Subject(s)
Microbial Viability , Plant Roots/microbiology , Pseudomonas/physiology , Soil Microbiology , Triticum/microbiology , Animals , Antibiosis , Antifungal Agents/metabolism , Cluster Analysis , Colony Count, Microbial , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/chemistry , DNA, Ribosomal/genetics , Fungi/growth & development , Molecular Sequence Data , Phylogeny , Plant Growth Regulators/metabolism , Pseudomonas/classification , Pseudomonas/growth & development , Pseudomonas/metabolism , RNA, Ribosomal, 16S/genetics , Sequence Analysis, DNA
4.
Curr Microbiol ; 55(4): 314-22, 2007 Oct.
Article in English | MEDLINE | ID: mdl-17700983

ABSTRACT

A bacterial collection of approximately one thousand native strains, isolated from saline soils of Cordoba province (Argentina), was established. From this collection, a screening to identify those strains showing plant growth promotion and biocontrol activities, as well as salt tolerance, was performed. Eight native strains tolerant to 1 M: NaCl and displaying plant growth promotion and/or biocontrol features were selected for further characterization. Strains MEP(2 )18, MRP(2 )26, MEP(2 )11a, MEP(3 )1, and MEP(3 )3b significantly increased the growth of maize seedlings under normal and saline conditions, whereas isolates ARP(2 )3, AEP(1 )5, and ARP(2 )6 were able to increase the root dry weight of agropyre under saline conditions. On the other hand, strains MEP(2 )18 and ARP(2 )3 showed antagonistic activity against phytopathogenic fungi belonging to Sclerotinia and Fusarium genus. Antifungal activity was found in cell-free supernatants, and it was heat and protease resistant. Strains MEP(2)18 and ARP(2)3 were identified as Bacillus sp. and strains MEP(2)11a and MEP(3)3b as Ochrobactrum sp. according to the sequence analysis of 16S rRNA gene.


Subject(s)
Bacterial Physiological Phenomena , Fungi/growth & development , Plant Development , Plant Diseases/microbiology , Plant Roots/microbiology , Sodium Chloride/pharmacology , Soil Microbiology , Agropyron/drug effects , Agropyron/growth & development , Agropyron/metabolism , Argentina , Bacteria/isolation & purification , DNA, Ribosomal/genetics , Pest Control, Biological , Phylogeny , Sequence Analysis, DNA , Zea mays/drug effects , Zea mays/growth & development , Zea mays/metabolism
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