scholarly journals Phenotypic Consequences Resulting from a Methionine-to-Valine Substitution at Position 48 in the HPr Protein of Streptococcus salivarius

1999 ◽  
Vol 181 (22) ◽  
pp. 6914-6921 ◽  
Author(s):  
Pascale Plamondon ◽  
Denis Brochu ◽  
Suzanne Thomas ◽  
Julie Fradette ◽  
Lucie Gauthier ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Minor Effect ◽  
Streptococcus Salivarius ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Regulatory Molecule ◽  
Dependent Protein ◽  
A Minor

ABSTRACT In gram-positive bacteria, the HPr protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) can be phosphorylated on a histidine residue at position 15 (His15) by enzyme I (EI) of the PTS and on a serine residue at position 46 (Ser46) by an ATP-dependent protein kinase (His∼P and Ser-P, respectively). We have isolated fromStreptococcus salivarius ATCC 25975, by independent selection from separate cultures, two spontaneous mutants (Ga3.78 and Ga3.14) that possess a missense mutation in ptsH (the gene encoding HPr) replacing the methionine at position 48 by a valine. The mutation did not prevent the phosphorylation of HPr at His15 by EI nor the phosphorylation at Ser46 by the ATP-dependent HPr kinase. The levels of HPr(Ser-P) in glucose-grown cells of the parental and mutant Ga3.78 were virtually the same. However, mutant cells growing on glucose produced two- to threefold less HPr(Ser-P)(His∼P) than the wild-type strain, while the levels of free HPr and HPr(His∼P) were increased 18- and 3-fold, respectively. The mutants grew as well as the wild-type strain on PTS sugars (glucose, fructose, and mannose) and on the non-PTS sugars lactose and melibiose. However, the growth rate of both mutants on galactose, also a non-PTS sugar, decreased rapidly with time. The M48V substitution had only a minor effect on the repression of α-galactosidase, β-galactosidase, and galactokinase by glucose, but this mutation abolished diauxie by rendering cells unable to prevent the catabolism of a non-PTS sugar (lactose, galactose, and melibiose) when glucose was available. The results suggested that the capacity of the wild-type cells to preferentially metabolize glucose over non-PTS sugars resulted mainly from inhibition of the catabolism of these secondary energy sources via a HPr-dependent mechanism. This mechanism was activated following glucose but not lactose metabolism, and it did not involve HPr(Ser-P) as the only regulatory molecule.

The phosphoenolpyruvate: sugar phosphotransferase system of Streptococcus salivarius. Identification of a IIIman protein

1987 ◽  
Vol 33 (2) ◽  
pp. 118-122 ◽  
Author(s):  
Christian Vadeboncoeur ◽  
Lucie Gauthier
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Deae Cellulose ◽  
Reaction Medium ◽  
Inhibitory Effect ◽  
Spontaneous Mutant ◽  
Streptococcus Salivarius ◽  
Wild Type ◽  
Phosphotransferase System ◽  
Growth Inhibitory

A double-spontaneous mutant resistant to the growth inhibitory effect of α-methylglucoside and 2-deoxyglucose was isolated from Streptococcus salivarius. This mutant strain, called αS3L11, did not grow on mannose and grew poorly on 5 mM fructose and 5 mM glucose. Isolated membranes of strain αS3L11 were unable to catalyse the phosphoenolpyruvate-dependent phosphorylation of mannose in the presence of purified enzyme I and HPr. Addition of dialysed membrane-free cellular extract of the wild-type strain to the reaction medium restored the activity. The factor that restored the phosphoenolpyruvate–mannose phosphotransferase activity to membranes of strain αS3L11 was called IIIman. This factor was partially purified from the wild-type strain by DEAE-cellulose chromatography, DEAE-TSK chromatography, and molecular seiving on a column of Ultrogel AcA 34. This partially purified preparation also enhanced the phosphoenolpyruvate-dependent phosphorylation of glucose, fructose, and 2-deoxyglucose in strain αS3L11.

scholarly journals Ca2+-calmodulin promotes survival of pheromone-induced growth arrest by activation of calcineurin and Ca2+-calmodulin-dependent protein kinase.

1996 ◽  
Vol 16 (9) ◽  
pp. 4824-4831 ◽  
Author(s):  
M J Moser ◽  
J R Geiser ◽  
T N Davis
Keyword(s):  
Protein Kinase ◽  
Type Strain ◽  
Wild Type Strain ◽  
Lethal Dose ◽  
Wild Type ◽  
Dependent Protein Kinase ◽  
Gene Encoding ◽  
Alpha Factor ◽  
Dependent Protein ◽  
Calmodulin Mutant

The cmd1-6 allele contains three mutations that block Ca2+ binding to calmodulin from Saccharomyces cerevisiae. We find that strains containing cmd1-6 lose viability during cell cycle arrest induced by the mating pheromone alpha-factor. The 50% lethal dose (LD50) of alpha-factor for the calmodulin mutant is almost fivefold below the LD50 for a wild-type strain. The calmodulin mutants are not more sensitive to alpha-factor, as measured by activation of a pheromone-responsive reporter gene. Two observations indicate that activation of the Ca2+-calmodulin-dependent protein phosphatase calcineurin contributes to survival of pheromone-induced arrest. First, deletion of the gene encoding the calcineurin regulatory B subunit, CNB1, from a wild-type strain decreases the LD50 of alpha-factor but has no further effect on a cmd1-6 strain. Second, a dominant constitutive calcineurin mutant partially restores the ability of the cmd1-6 strain to survive exposure to alpha-factor. Activation of the Ca2+-calmodulin-dependent protein kinase (CaMK) also contributes to survival, thus revealing a new function for this enzyme. Deletion of the CMK1 and CMK2 genes, which encode CaMK, decreases the LD50 of pheromone compared with that for a wild-type strain but again has no effect in a cmd1-6 strain. Furthermore, the LD50 of alpha-factor for a mutant in which the calcineurin and CaMK genes have been deleted is the same as that for the calmodulin mutant. Finally, the CaMK and calcineurin pathways appear to be independent since the ability of constitutive calcineurin to rescue a cmd1-6 strain is not blocked by deletion of the CaMK genes.

scholarly journals Expression and function of the cdgD gene, encoding a CHASE–PAS-DGC-EAL domain protein, in Azospirillum brasilense

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
José Francisco Cruz-Pérez ◽  
Roxana Lara-Oueilhe ◽  
Cynthia Marcos-Jiménez ◽  
Ricardo Cuatlayotl-Olarte ◽  
María Luisa Xiqui-Vázquez ◽  
...  
Keyword(s):  
Azospirillum Brasilense ◽  
Type Strain ◽  
Wild Type Strain ◽  
Soil Conditions ◽  
Wild Type ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Genes Encoding ◽  
In The Wild ◽  
Plant Growth Promoting

AbstractThe plant growth-promoting bacterium Azospirillum brasilense contains several genes encoding proteins involved in the biosynthesis and degradation of the second messenger cyclic-di-GMP, which may control key bacterial functions, such as biofilm formation and motility. Here, we analysed the function and expression of the cdgD gene, encoding a multidomain protein that includes GGDEF-EAL domains and CHASE and PAS domains. An insertional cdgD gene mutant was constructed, and analysis of biofilm and extracellular polymeric substance production, as well as the motility phenotype indicated that cdgD encoded a functional diguanylate protein. These results were correlated with a reduced overall cellular concentration of cyclic-di-GMP in the mutant over 48 h compared with that observed in the wild-type strain, which was recovered in the complemented strain. In addition, cdgD gene expression was measured in cells growing under planktonic or biofilm conditions, and differential expression was observed when KNO3 or NH4Cl was added to the minimal medium as a nitrogen source. The transcriptional fusion of the cdgD promoter with the gene encoding the autofluorescent mCherry protein indicated that the cdgD gene was expressed both under abiotic conditions and in association with wheat roots. Reduced colonization of wheat roots was observed for the mutant compared with the wild-type strain grown in the same soil conditions. The Azospirillum-plant association begins with the motility of the bacterium towards the plant rhizosphere followed by the adsorption and adherence of these bacteria to plant roots. Therefore, it is important to study the genes that contribute to this initial interaction of the bacterium with its host plant.

scholarly journals vpaH, a Gene Encoding a Novel Histone-Like Nucleoid Structure-Like Protein That Was Possibly Horizontally Acquired, Regulates the Biogenesis of Lateral Flagella in trh-Positive Vibrio parahaemolyticus TH3996

2005 ◽  
Vol 73 (9) ◽  
pp. 5754-5761 ◽  
Author(s):  
Kwon-Sam Park ◽  
Michiko Arita ◽  
Tetsuya Iida ◽  
Takeshi Honda
Keyword(s):  
Biofilm Formation ◽  
Vibrio Parahaemolyticus ◽  
Type Strain ◽  
Wild Type Strain ◽  
Enteric Bacteria ◽  
Wild Type ◽  
Gene Encoding ◽  
Lateral Flagellum ◽  
Global Gene Regulation ◽  
Nucleoid Structure

ABSTRACT A histone-like nucleoid structure (H-NS) is a major component of the bacterial nucleoid and plays a crucial role in the global gene regulation of enteric bacteria. Here, we cloned and characterized the gene for the H-NS-like protein VpaH in Vibrio parahaemolyticus. vpaH encodes a protein of 134 amino acids that shows approximately 55%, 54%, and 41% identities with VicH in Vibrio cholerae, H-NS in V. parahaemolyticus, and H-NS in Escherichia coli, respectively. The vpaH gene was found in only trh-positive V. parahaemolyticus strains and not in Kanagawa-positive or in trh-negative environmental strains. Moreover, the G+C content of the vpaH gene was 38.6%, which is lower than the average G+C content of the whole genome of this bacterium (45.4%). These data suggest that vpaH was transmitted to trh-possessing V. parahaemolyticus strains by lateral transfer. The vpaH gene was located about 2.6 kb downstream of the trh gene, in the convergent direction of the trh transcription. An in-frame deletion mutant of vpaH lacked motility on semisolid motility assay plates. Western blot analysis and electron microscopy observations revealed that the mutant was deficient in lateral flagella biogenesis, whereas there was no defect in the expression of polar flagella. Additionally, the vpaH mutant showed a decreased adherence to HeLa cells and a decrease in biofilm formation compared with the wild-type strain. Introduction of the vpaH gene in the vpaH-negative strain increased the expression of lateral flagella compared with the wild-type strain. In conclusion, our findings suggest that VpaH affects lateral flagellum biogenesis in trh-positive V. parahaemolyticus strain TH3996.

scholarly journals Expression of Erwinia chrysanthemi Pectinase Genes pelI, pelL, and pelZ During Infection of Potato Tubers

1999 ◽  
Vol 12 (10) ◽  
pp. 845-851 ◽  
Author(s):  
Sylwia Jafra ◽  
Izabela Figura ◽  
Nicole Hugouvieux-Cotte-Pattat ◽  
Ewa Lojkowska
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Pectate Lyase ◽  
Soft Rot ◽  
Erwinia Chrysanthemi ◽  
Potato Tubers ◽  
Wild Type ◽  
In Planta ◽  
Gene Encoding ◽  
Glucuronidase Activity

Erwinia chrysanthemi mutants, containing transcriptional fusions of one of the minor pectate lyase genes (pelI, pelL, pelZ) with the reporter gene encoding β-glucuronidase activity, were studied for their ability to cause disease symptoms and to synthesize pectinases after inoculation of potato tubers. The strains affected in pelI and pelL genes displayed reduced virulence on potato tubers, demonstrating the important role of these isoenzymes in soft rot disease. Inactivation of the pelZ gene slightly influences the ability to macerate. Analysis of the bacterial population showed rapid multiplication of bacteria during infection. Similar kinetics of growth were observed for all mutants and for the wild-type strain. Comparison of the mutants and the wild-type strain showed that the pelI, pelL, and pelZ mutants synthesized reduced levels of Pels. The expression of pelZ is fivefold higher in planta than in bacterial cultures. In contrast, both pelI and pelL are highly (10-fold factor) induced in planta, which is characteristic of the plant-inducible pectate lyases.

scholarly journals Involvement of Quinolinate Phosphoribosyl Transferase in Promotion of Potato Growth by a Burkholderia Strain

2006 ◽  
Vol 72 (1) ◽  
pp. 760-768 ◽  
Author(s):  
Keri Wang ◽  
Kenneth Conn ◽  
George Lazarovits
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
De Novo ◽  
Growth Promotion ◽  
Amino Acid Level ◽  
Growth Stimulation ◽  
Wild Type ◽  
Gene Encoding ◽  
Burkholderia Strain ◽  
Potato Growth

ABSTRACT Burkholderia sp. strain PsJN stimulates root growth of potato explants compared to uninoculated controls under gnotobiotic conditions. In order to determine the mechanism by which this growth stimulation occurs, we used Tn5 mutagenesis to produce a mutant, H41, which exhibited no growth-promoting activity but was able to colonize potato plants as well as the wild-type strain. The gene associated with the loss of growth promotion in H41 was shown to exhibit 65% identity at the amino acid level to the nadC gene encoding quinolinate phosphoribosyltransferase (QAPRTase) in Ralstonia solanacearum. Complementation of H41 with QAPRTase restored growth promotion of potato explants by this mutant. Expression of the gene identified in Escherichia coli yielded a protein with QAPRTase activities that catalyzed the de novo formation of nicotinic acid mononucleotide (NaMN). Two other genes involved in the same enzymatic pathway, nadA and nadB, were physically linked to nadC. The nadA gene was cotranscribed with nadC as an operon in wild-type strain PsJN, while the nadB gene was located downstream of the nadA-nadC operon. Growth promotion by H41 was fully restored by addition of NaMN to the tissue culture medium. These data suggested that QAPRTase may play a role in the signal pathway for promotion of plant growth by PsJN.

scholarly journals The chvH Locus ofAgrobacterium Encodes a Homologue of an Elongation Factor Involved in Protein Synthesis

2001 ◽  
Vol 183 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Wen-Tao Peng ◽  
Lois M. Banta ◽  
Trevor C. Charles ◽  
Eugene W. Nester
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Elongation Factor ◽  
Peptide Bond ◽  
Single Copy ◽  
Tumor Formation ◽  
Wild Type ◽  
Chromosomal Locus ◽  
Gene Encoding ◽  
Elongation Factor P

ABSTRACT The virulence of Agrobacterium tumefaciens depends on both chromosome- and Ti plasmid-encoded gene products. In this study, we characterize a chromosomal locus, chvH, previously identified by TnphoA mutagenesis and shown to be required for tumor formation. Through DNA sequencing and comparison of the sequence with identified sequences in the database, we show that this locus encodes a protein similar in sequence to elongation factor P, a protein thought to be involved in peptide bond synthesis inEscherichia coli. The analysis of vir-lacZ andvir-phoA translational fusions as well as Western immunoblotting revealed that the expression of Vir proteins such as VirE2 was significantly reduced in the chvH mutant compared with the wild-type strain. The E. coli efp gene complemented detergent sensitivity, virulence, and expression of VirE2 in the chvH mutant, suggesting that chvH andefp are functionally homologous. As expected, ChvH exerts its activity at the posttranscriptional level. Southern analysis suggests that the gene encoding this elongation factor is present as a single copy in A. tumefaciens. We constructed achvH deletion mutant in which a 445-bp fragment within its coding sequence was deleted and replaced with an omega fragment. On complex medium, this mutant grew more slowly than the wild-type strain, indicating that elongation factor P is important but not essential for the growth of Agrobacterium.

scholarly journals Identification and Characterization of hmr19 Gene Encoding a Multidrug Resistance Efflux Protein from Streptomyces hygroscopicus subsp. yingchengensis Strain 10–22

2004 ◽  
Vol 36 (8) ◽  
pp. 519-528 ◽  
Author(s):  
Lei Qin ◽  
Heng-An Wang ◽  
Zhong-Qin Wu ◽  
Xiao-Feng Zhang ◽  
Mei-Lei Jin ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Type Strain ◽  
Wild Type Strain ◽  
Sequence Similarity ◽  
Gene Replacement ◽  
Major Facilitator Superfamily ◽  
Streptomyces Hygroscopicus ◽  
Wild Type ◽  
Gene Encoding ◽  
Major Facilitator

Abstract The hmr19 gene was cloned from Streptomyces hygroscopicus subsp. yingchengensis strain 10–22, a bacterium strain producing agricultural antibiotics. Sequence similarity comparison indicates that hmr19 gene may encode a predicted protein with 14 putative transmembrane α-helical spanners, belonging to the drug:H+ antiporter-2 family of the major facilitator superfamily. The expression of hmr19 in the mycelium of strain 10-22 was detected by Western blotting analysis. Gene replacement technology was employed to construct an hmr19 disruption mutant. The growth inhibition test against different antibiotics indicated that the mutant strain was 5–20 fold more susceptible to tetracycline, vancomycin and mitomycin C than the parental wild type strain. The mutant took up tetracycline much faster and accumulated more antibiotics than the wild type strain 10-22. While with the addition of an energy uncoupler, carbonyl cyanide m-chlorophenylhydrazone, the characteristics of the accumulation of [3H]tetracycline in these two strains were almost the same. It was thus concluded that hmr19 encoded a multidrug resistance efflux protein.

scholarly journals Role of Respiratory Nitrate Reductase in Ability ofPseudomonas fluorescens YT101 To Colonize the Rhizosphere of Maize

2000 ◽  
Vol 66 (9) ◽  
pp. 4012-4016 ◽  
Author(s):  
Jean-Fran�ois Ghiglione ◽  
Fran�ois Gourbiere ◽  
Patrick Potier ◽  
Laurent Philippot ◽  
Robert Lensi
Keyword(s):  
Nitrate Reductase ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Replacement Series ◽  
Gene Encoding ◽  
Direct Demonstration ◽  
Respiratory Nitrate Reductase ◽  
Selection Of

ABSTRACT Selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. However, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. In the present study, we compared the rhizosphere survival of the denitrifyingPseudomonas fluorescens YT101 strain with that of its isogenic mutant deficient in the ability to synthesize the respiratory nitrate reductase, coinoculated in nonplanted or planted soil. We demonstrated that under nonlimiting nitrate conditions, the denitrifying wild-type strain had an advantage in the ability to colonize the rhizosphere of maize. Investigations of the effect of the inoculum characteristics (density of the total inoculum and relative proportions of mutant and wild-type strains) on the outcome of the selection demonstrated that the selective effect of the plant was expressed only during the phase of bacterial multiplication and that the intensity of selection was dependent on the magnitude of this phase. Moreover, application of the de Wit replacement series technique to our results suggests that the advantage of the wild-type strain was maximal when the ratio between the two strains in the inoculum was close to 1:1. This work constitutes the first direct demonstration that the presence of a functional structural gene encoding the respiratory nitrate reductase confers higher rhizosphere competence to a microorganism.

scholarly journals Screen for Leukotoxin Mutants in Aggregatibacter actinomycetemcomitans: Genes of the Phosphotransferase System Are Required for Leukotoxin Biosynthesis

2008 ◽  
Vol 76 (8) ◽  
pp. 3561-3568 ◽  
Author(s):  
Maria P. Isaza ◽  
Matthew S. Duncan ◽  
Jeffrey B. Kaplan ◽  
Scott C. Kachlany
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Aggressive Periodontitis ◽  
Pcr Analysis ◽  
Growth Media ◽  
Wild Type ◽  
Camp Production ◽  
Phosphotransferase System ◽  
In The Wild ◽  
Transposon Insertions

ABSTRACT Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans is a pathogen that causes localized aggressive periodontitis and extraoral infections including infective endocarditis. Recently, we reported that A. actinomycetemcomitans is beta-hemolytic on certain growth media due to the production of leukotoxin (LtxA). Based on this observation and our ability to generate random transposon insertions in A. actinomycetemcomitans, we developed and carried out a rapid screen for LtxA mutants. Using PCR, we mapped several of the mutations to genes that are known or predicted to be required for LtxA production, including ltxA, ltxB, ltxD, and tdeA. In addition, we identified an insertion in a gene previously not recognized to be involved in LtxA biosynthesis, ptsH. ptsH encodes the protein HPr, a phosphocarrier protein that is part of the sugar phosphotransferase system. HPr results in the phosphorylation of other proteins and ultimately in the activation of adenylate cyclase and cyclic AMP (cAMP) production. The ptsH mutant showed only partial hemolysis on blood agar and did not produce LtxA. The phenotype was complemented by supplying wild-type ptsH in trans, and real-time PCR analysis showed that the ptsH mutant produced approximately 10-fold less ltxA mRNA than the wild-type strain. The levels of cAMP in the ptsH mutant were significantly lower than in the wild-type strain, and LtxA production could be restored by adding exogenous cAMP to the culture.

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