The global regulator GacS regulates biofilm formation in Pseudomonas chlororaphis O6 differently with carbon source

2014 ◽  
Vol 60 (3) ◽  
pp. 133-138 ◽  
Author(s):  
Ji Soo Kim ◽  
Yong Hwan Kim ◽  
Ju Yeon Park ◽  
Anne J. Anderson ◽  
Young Cheol Kim
Keyword(s):  
Carbon Source ◽  
Biofilm Formation ◽  
Defined Medium ◽  
Root Surface ◽  
Gray Mold ◽  
Systemic Resistance ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Tomato Leaf Mold ◽  
Phenazine Production

An aggressive root colonizer, Pseudomonas chlororaphis O6 produces various secondary metabolites that impact plant health. The sensor kinase GacS is a key regulator of the expression of biocontrol-related traits. Biofilm formation is one such trait because of its role in root surface colonization. This paper focuses on the effects of carbon source on biofilm formation. In comparison with the wild type, a gacS mutant formed biofilms at a reduced level with sucrose as the major carbon source but at much higher level with mannitol in the defined medium. Biofilm formation by the gacS mutant occurred without phenazine production and in the absence of normal levels of acyl homoserine lactones, which promote biofilms with other pseudomonads. Colonization of tomato roots was similar for the wild type and gacS mutant, showing that any differences in biofilm formation in the rhizosphere were not of consequence under the tested conditions. The reduced ability of the gacS mutant to induce systemic resistance against tomato leaf mold and tomato gray mold was consistent with a lack of production of effectors, such as phenazines. These results demonstrated plasticity in biofilm formation and root colonization in the rhizosphere by a beneficial pseudomonad.

scholarly journals Altering the Ratio of Phenazines in Pseudomonas chlororaphis (aureofaciens) Strain 30-84: Effects on Biofilm Formation and Pathogen Inhibition

2008 ◽  
Vol 190 (8) ◽  
pp. 2759-2766 ◽  
Author(s):  
V. S. R. K. Maddula ◽  
E. A. Pierson ◽  
L. S. Pierson
Keyword(s):  
Fungal Pathogen ◽  
Biofilm Formation ◽  
Flow Cell ◽  
Gaeumannomyces Graminis ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Initial Attachment ◽  
Pathogen Inhibition ◽  
Biofilm Development ◽  
Derivatives Of

ABSTRACT Pseudomonas chlororaphis strain 30-84 is a plant-beneficial bacterium that is able to control take-all disease of wheat caused by the fungal pathogen Gaeumannomyces graminis var. tritici. The production of phenazines (PZs) by strain 30-84 is the primary mechanism of pathogen inhibition and contributes to the persistence of strain 30-84 in the rhizosphere. PZ production is regulated in part by the PhzR/PhzI quorum-sensing (QS) system. Previous flow cell analyses demonstrated that QS and PZs are involved in biofilm formation in P. chlororaphis (V. S. R. K. Maddula, Z. Zhang, E. A. Pierson, and L. S. Pierson III, Microb. Ecol. 52:289-301, 2006). P. chlororaphis produces mainly two PZs, phenazine-1-carboxylic acid (PCA) and 2-hydroxy-PCA (2-OH-PCA). In the present study, we examined the effect of altering the ratio of PZs produced by P. chlororaphis on biofilm formation and pathogen inhibition. As part of this study, we generated derivatives of strain 30-84 that produced only PCA or overproduced 2-OH-PCA. Using flow cell assays, we found that these PZ-altered derivatives of strain 30-84 differed from the wild type in initial attachment, mature biofilm architecture, and dispersal from biofilms. For example, increased 2-OH-PCA production promoted initial attachment and altered the three-dimensional structure of the mature biofilm relative to the wild type. Additionally, both alterations promoted thicker biofilm development and lowered dispersal rates compared to the wild type. The PZ-altered derivatives of strain 30-84 also differed in their ability to inhibit the fungal pathogen G. graminis var. tritici. Loss of 2-OH-PCA resulted in a significant reduction in the inhibition of G. graminis var. tritici. Our findings suggest that alterations in the ratios of antibiotic secondary metabolites synthesized by an organism may have complex and wide-ranging effects on its biology.

scholarly journals Exopolysaccharide Production Is Required for Biofilm Formation and Plant Colonization by the Nitrogen-Fixing Endophyte Gluconacetobacter diazotrophicus

2011 ◽  
Vol 24 (12) ◽  
pp. 1448-1458 ◽  
Author(s):  
Carlos H. S. G. Meneses ◽  
Luc F. M. Rouws ◽  
Jean L. Simões-Araújo ◽  
Marcia S. Vidal ◽  
José I. Baldani
Keyword(s):  
Biofilm Formation ◽  
Bacterial Species ◽  
Carbon Sources ◽  
Normal Growth ◽  
Root Surface ◽  
Plant Colonization ◽  
Gluconacetobacter Diazotrophicus ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Endophytic Colonization

The genome of the endophytic diazotrophic bacterial species Gluconacetobacter diazotrophicus PAL5 (PAL5) revealed the presence of a gum gene cluster. In this study, the gumD gene homologue, which is predicted to be responsible for the first step in exopolysaccharide (EPS) production, was insertionally inactivated and the resultant mutant (MGD) was functionally studied. The mutant MGD presented normal growth and nitrogen (N2) fixation levels but did not produce EPS when grown on different carbon sources. MGD presented altered colony morphology on soft agar plates (0.3% agar) and was defective in biofilm formation on glass wool. Most interestingly, MGD was defective in rice root surface attachment and in root surface and endophytic colonization. Genetic complementation reverted all mutant phenotypes. Also, the addition of EPS purified from culture supernatants of the wild-type strain PAL5 to the mutant MGD was effective in partially restoring wild-type biofilm formation and plant colonization. These data provide strong evidence that the PAL5 gumD gene is involved in EPS biosynthesis and that EPS biosynthesis is required for biofilm formation and plant colonization. To our knowledge, this is the first report of a role of EPS in the endophytic colonization of graminaceous plants by a nitrogen-fixing bacterium.

scholarly journals Adaptation Genomics of a Small-Colony Variant in a Pseudomonas chlororaphis 30-84 Biofilm

2014 ◽  
Vol 81 (3) ◽  
pp. 890-899 ◽  
Author(s):  
Dongping Wang ◽  
Robert J. Dorosky ◽  
Cliff S. Han ◽  
Chien-chi Lo ◽  
Armand E. K. Dichosa ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Genetic Alterations ◽  
Whole Genome Sequence ◽  
Phenotypic Switching ◽  
Whole Genome ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Content Type ◽  
Small Colony Variant ◽  
Small Colony

ABSTRACTThe rhizosphere-colonizing bacteriumPseudomonas chlororaphis30-84 is an effective biological control agent against take-all disease of wheat. In this study, we characterize a small-colony variant (SCV) isolated from aP. chlororaphis30-84 biofilm. The SCV exhibited pleiotropic phenotypes, including small cell size, slow growth and motility, low levels of phenazine production, and increased biofilm formation and resistance to antimicrobials. To better understand the genetic alterations underlying these phenotypes, RNA and whole-genome sequencing analyses were conducted comparing an SCV to the wild-type strain. Of the genome's 5,971 genes, transcriptomic profiling indicated that 1,098 (18.4%) have undergone substantial reprograming of gene expression in the SCV. Whole-genome sequence analysis revealed multiple alterations in the SCV, including mutations inyfiR(cyclic-di-GMP production),fusA(elongation factor), andcyoE(heme synthesis) and a 70-kb deletion. Genetic analysis revealed that theyfiRlocus plays a major role in controlling SCV phenotypes, including colony size, growth, motility, and biofilm formation. Moreover, a point mutation in thefusAgene contributed to kanamycin resistance. Interestingly, the SCV can partially switch back to wild-type morphologies under specific conditions. Our data also support the idea that phenotypic switching inP. chlororaphisis not due to simple genetic reversions but may involve multiple secondary mutations. The emergence of these highly adherent and antibiotic-resistant SCVs within the biofilm might play key roles inP. chlororaphisnatural persistence.

Physicochemical parameters influencing the formation of biofilms compared in mutant and wild-type cells of Pseudomonas chlororaphis O6

2005 ◽  
Vol 52 (7) ◽  
pp. 21-25 ◽  
Author(s):  
A.J. Anderson ◽  
D.W. Britt ◽  
J. Johnson ◽  
G. Narasimhan ◽  
A. Rodriguez
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Cell Structure ◽  
Strong Interactions ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Small Colony Variant ◽  
Force Microscopy ◽  
Force Mode ◽  
Biofilm Structure

Bacteria colonize surfaces as heterogeneous structures called biofilms. Intercellular communication using acyl homoserine lactones has been implicated in biofilm formation in some systems. Here, we investigate cell structure in biofilms and associated physiochemical properties of wild type and quorum sensing mutants of Pseudomonas chlororaphis O6 (PcO6), a root-colonizing bacterium. The wild type strain generates multilayered biofilms under conditions where the quorum sensing mutant, deficient in the GacS sensor kinase, does not mature beyond a monolayer structure. However, this gacS mutant rapidly evolves to form a small colony variant (gacS-SCV) that again produces a multilayered biofilm structure although AHSL production is not restored to wild type level. Biofilms formed by the gacS-SCV (114±12°) mutant were the most hydrophobic displaying a higher average ethylene glycol contact angle than those formed by the wild type (28±7°) and gacS (18±6°). Tapping mode atomic force microscopy revealed elongated cell structure in both of the mutant biofilm cells. Digital pulsed force mode adhesion mapping showed that the average adhesion followed the order gacS>gacS-SCV, wild-type. Certain of these gacS mutant cells displayed strong interactions of the AFM tip with cell boundaries, the role of which in biofilm formation is currently under investigation.

scholarly journals Lactate Acquisition Promotes Successful Colonization of the Murine Genital Tract by Neisseria gonorrhoeae

2006 ◽  
Vol 75 (3) ◽  
pp. 1318-1324 ◽  
Author(s):  
Rachel M. Exley ◽  
Hong Wu ◽  
Jonathan Shaw ◽  
Muriel C. Schneider ◽  
Harry Smith ◽  
...  
Keyword(s):  
Carbon Source ◽  
Tract Infection ◽  
Neisseria Gonorrhoeae ◽  
Genital Tract ◽  
Defined Medium ◽  
Growth Defect ◽  
Wild Type ◽  
Genital Tract Infection ◽  
Lactate Utilization

ABSTRACT Previous studies on Neisseria gonorrhoeae have demonstrated that metabolism of lactate in the presence of glucose increases the growth rate of the bacterium and enhances its resistance to complement-mediated killing. Although these findings in vitro suggest that the acquisition of lactate promotes gonococcal colonization, the significance of this carbon source to the survival of the gonococcus in vivo remains unknown. To investigate the importance of lactate utilization during Neisseria gonorrhoeae genital tract infection, we identified the gene lctP, which encodes the gonococcal lactate permease. A mutant that lacks a functional copy of lctP was unable to take up exogenous lactate and did not grow in defined medium with lactate as the sole carbon source, in contrast to the wild-type and complemented strains; the mutant strain exhibited no growth defect in defined medium containing glucose. In defined medium containing physiological concentrations of lactate and glucose, the lctP mutant demonstrated reduced early growth and increased sensitivity to complement-mediated killing compared with the wild-type strain; the enhanced susceptibility to complement was associated with a reduction in lipopolysaccharide sialylation of the lctP mutant. The importance of lactate utilization during colonization was evaluated in the murine model of lower genital tract infection. The lctP mutant was significantly attenuated in its ability to colonize and survive in the genital tract, while the complemented mutant exhibited no defect for colonization. Lactate is a micronutrient in the genital tract that contributes to the survival of the gonococcus.

scholarly journals Polyhydroxyalkanoate (PHA) Polymer Accumulation and pha Gene Expression in Phenazine (phz-) and Pyrrolnitrin (prn-) Defective Mutants of Pseudomonas chlororaphis PA23

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1203 ◽  
Author(s):  
Parveen Sharma ◽  
Riffat Munir ◽  
Jocelyn Plouffe ◽  
Nidhi Shah ◽  
Teresa Kievit ◽  
...  
Keyword(s):  
Gene Expression ◽  
Reducing Power ◽  
Pentose Phosphate ◽  
Pha Synthase ◽  
Pseudomonas Chlororaphis ◽  
Glucose Medium ◽  
Wild Type ◽  
Pha Production ◽  
Phenazine Production ◽  
Altered Gene

Pseudomonas chlororaphis PA23 was isolated from the rhizosphere of soybeans and identified as a biocontrol bacterium against Sclerotinia sclerotiorum, a fungal plant pathogen. This bacterium produces a number of secondary metabolites, including phenazine-1-carboxylic acid, 2-hydroxyphenazine, pyrrolnitrin (PRN), hydrogen cyanide, proteases, lipases and siderophores. It also synthesizes and accumulates polyhydroxyalkanoate (PHA) polymers as carbon and energy storage compounds under nutrient-limited conditions. Pseudomonads like P. chlororaphis metabolize glucose via the Entner-Doudoroff and Pentose Phosphate pathways, which provide precursors for phenazine production. Mutants defective in phenazine (PHZ; PA23-63), PRN (PA23-8), or both (PA23-63-1) accumulated higher concentrations of PHAs than the wild-type strain (PA23) when cultured in Ramsay’s Minimal Medium with glucose or octanoic acid as the carbon source. Expression levels of six pha genes, phaC1, phaZ, phaC2, phaD, phaF, and phaI, were compared with wild type PA23 by quantitative real time polymerase chain reaction (qPCR). The qPCR studies indicated that there was no change in levels of transcription of the PHA synthase genes phaC1 and phaC2 in the phz- (PA23-63) and phz- prn- (PA23-63-1) mutants in glucose medium. There was a significant increase in expression of phaC2 in octanoate medium. Transcription of phaD, phaF and phaI increased significantly in the phz- prn- (PA23-63-1) mutant. Mutations in regulatory genes like gacS, rpoS, and relA/spoT, which affect PHZ and PRN production, also resulted in altered gene expression. The expression of phaC1, phaC2, phaF, and phaI genes was down-regulated significantly in gacS and rpoS mutants. Thus, it appears that PHZ, PRN, and PHA production is regulated by common mechanisms. Higher PHA production in the phz- (PA23-63), prn- (PA23-8), and phz- prn- (PA23-63-1) mutants in octanoic medium could be correlated with higher expression of phaC2. Further, the greater PHA production observed in the phz- and prn- mutants was not due to increased transcription of PHA synthase genes in glucose medium, but due to more accessibility of carbon substrates and reducing power, which were otherwise used for the synthesis of PHZ and PRN.

The GacS-regulated sigma factor RpoS governs production of several factors involved in biocontrol activity of the rhizobacterium Pseudomonas chlororaphis O6

2013 ◽  
Vol 59 (8) ◽  
pp. 556-562 ◽  
Author(s):  
Sang A. Oh ◽  
Ji Soo Kim ◽  
Song Hee Han ◽  
Ju Yeon Park ◽  
Christian Dimkpa ◽  
...  
Keyword(s):  
Sigma Factor ◽  
Plant Diseases ◽  
Systemic Resistance ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Tomato Root ◽  
Rpos Mutant ◽  
Beneficial Traits ◽  
Sigma Factor Rpos

Pseudomonas chlororaphis O6 possesses many beneficial traits involved in biocontrol of plant diseases. In this paper, we examined the effect of a mutation in rpoS encoding a stress-related alternative sigma factor to better understand the regulation of these traits. Biochemical studies indicated that production of acyl homoserine lactones was altered and phenazine was increased in the P. chlororaphis O6 rpoS mutant. The rpoS mutation reduced hydrogen cyanide levels, but the rpoS mutant still displayed a level of in vitro antifungal activity against Fusarium graminearum and Alternaria alternata. Tomato root colonization by the rpoS mutant was lower than that by the wild type at 5, 7, and 13 days after inoculation. The rpoS mutant was less effective than the wild type in induction of systemic resistance to two foliar pathogens after root inoculation of the tomato plants. Our findings demonstrate that the stationary-phase sigma factor RpoS regulates production of several key factors involved in the biocontrol potential of P. chlororaphis O6, some independently of the global regulator GacS.

scholarly journals Role of Biofilm Formation by Bacillus pumilus HR10 in Biocontrol against Pine Seedling Damping-Off Disease Caused by Rhizoctonia solani

Forests ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 652 ◽  
Author(s):  
Mei-Ling Zhu ◽  
Xiao-Qin Wu ◽  
Ya-Hui Wang ◽  
Yun Dai
Keyword(s):  
Rhizoctonia Solani ◽  
Biofilm Formation ◽  
Bacillus Pumilus ◽  
Large Population ◽  
Control Plant ◽  
Plant Diseases ◽  
Systemic Resistance ◽  
Extracellular Polysaccharides ◽  
Wild Type ◽  
Mutant Strains

The biocontrol process mediated by plant growth-promoting rhizobacteria (PGPR) relies on multiple mechanisms. Biofilm formation plays an important role in the ability of PGPR to control plant diseases. Bacillus pumilus HR10, one such PGPR, promotes the growth of Pinus thunbergii. This study showed that the wild-type strain B. pumilus HR10 produces a stable and mature biofilm in vitro. Biofilm-deficient mutants of B. pumilus HR10 with different phenotypes were screened by mutagenesis. The contents of extracellular polysaccharides (EPS) and proteins produced by the mutant strains were significantly reduced, and the biofilms of the mutants were weakened to varying degrees. The swarming abilities of the wild-type and mutant strains were positively correlated with biofilm formation. A colonization assay demonstrated that B. pumilus HR10 could colonize the roots of Pinus massoniana seedlings in a large population and persist, while biofilm-deficient mutants showed weak colonization ability. Furthermore, a biocontrol assay showed that biocontrol efficacy of the mutants was reduced to a certain degree. We determined the inhibitory activity of B. pumilus HR10 and its ability to induce systemic resistance against Rhizoctonia solani of plants. The synthesis of lipopeptide antibiotics is probably involved in biofilm formation by B. pumilus HR10. These observations not only provide a reference for further research about the coordinated action between biofilm formation and the multiple biocontrol mechanisms of B. pumilus HR10 but also improve the understanding of the regulatory pathway of biofilm formation by B. pumilus HR10.

scholarly journals Galactinol Is a Signaling Component of the Induced Systemic Resistance Caused by Pseudomonas chlororaphis O6 Root Colonization

2008 ◽  
Vol 21 (12) ◽  
pp. 1643-1653 ◽  
Author(s):  
Mi Seong Kim ◽  
Song Mi Cho ◽  
Eun Young Kang ◽  
Yang Ju Im ◽  
Hoon Hwangbo ◽  
...  
Keyword(s):  
Root Colonization ◽  
Induced Systemic Resistance ◽  
Systemic Resistance ◽  
Suppressive Subtractive Hybridization ◽  
Transcriptional Level ◽  
Hybridization Technique ◽  
Pseudomonas Chlororaphis ◽  
Wild Type ◽  
Water Control ◽  
Tobacco Plants

Root colonization by Pseudomonas chlororaphis O6 in cucumber elicited an induced systemic resistance (ISR) against Corynespora cassiicola. In order to gain insight into O6-mediated ISR, a suppressive subtractive hybridization technique was applied and resulted in the isolation of a cucumber galactinol synthase (CsGolS1) gene. The transcriptional level of CsGolS1 and the resultant galactinol content showed an increase several hours earlier under O6 treatment than in the water control plants following C. cassiicola challenge, whereas no difference was detected in the plants without a pathogen challenge. The CsGolS1-overexpressing transgenic tobacco plants demonstrated constitutive resistance against the pathogens Botrytis cinerea and Erwinia carotovora, and they also showed an increased accumulation in galactinol content. Pharmaceutical application of galactinol enhanced the resistance against pathogen infection and stimulated the accumulation of defense-related gene transcripts such as PR1a, PR1b, and NtACS1 in wild-type tobacco plants. Both the CsGolS1-overexpressing transgenic plants and the galactinol-treated wild-type tobacco plants also demonstrated an increased tolerance to drought and high salinity stresses.

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