scholarly journals Role of gene duplications in the adaptation of Salmonella typhimurium to growth on limiting carbon sources.

Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 19-28 ◽  
Author(s):  
R V Sonti ◽  
J R Roth
Keyword(s):  
Carbon Source ◽  
Salmonella Typhimurium ◽  
Carbon Sources ◽  
Chromosomal Segment ◽  
Transport Systems ◽  
Energy Sources ◽  
Gene Duplications ◽  
Large Segment

Abstract Duplication-containing cells are selected when growth of Salmonella typhimurium is limited by the availability of any one of several carbon and energy sources. Under conditions of extreme starvation, growth occurs almost exclusively in the duplication-containing fraction of the population. Cells with duplications of one large segment of the chromosome are repeatedly selected regardless of which of these carbon sources limits growth. The duplicated chromosomal segment encodes the transport systems for all of these carbon sources. This duplication is not selected during growth on a carbon source for which the permease is not included within the duplication segment. This suggests that the growth advantage conferred by the duplication may be due to increased transport of the limiting carbon source. Inclusion of the permease alone is not sufficient to explain the growth advantage of the duplications, since other common duplications that include the permease are not selected.

scholarly journals The Catabolite Repressor/Activator Cra Is a Bridge Connecting Carbon Metabolism and Host Colonization in the Plant Drought Resistance-Promoting Bacterium Pantoea alhagi LTYR-11Z

2018 ◽  
Vol 84 (13) ◽  
Author(s):  
Lei Zhang ◽  
Muhang Li ◽  
Qiqi Li ◽  
Chaoqiong Chen ◽  
Meng Qu ◽  
...  
Keyword(s):  
Carbon Source ◽  
Carbon Metabolism ◽  
Carbon Sources ◽  
Endophytic Bacterium ◽  
Bacterial Attachment ◽  
Gene Encoding ◽  
Wheat Roots ◽  
Host Colonization ◽  
Content Type

ABSTRACT Efficient root colonization is a prerequisite for application of plant growth-promoting (PGP) bacteria in improving health and yield of agricultural crops. We have recently identified an endophytic bacterium, Pantoea alhagi LTYR-11Z, with multiple PGP properties that effectively colonizes the root system of wheat and improves its growth and drought tolerance. To identify novel regulatory genes required for wheat colonization, we screened an LTYR-11Z transposon (Tn) insertion library and found cra to be a colonization-related gene. By using transcriptome (RNA-seq) analysis, we found that transcriptional levels of an eps operon, the ydiV gene encoding an anti-FlhD 4 C 2 factor, and the yedQ gene encoding an enzyme for synthesis of cyclic dimeric GMP (c-di-GMP) were significantly downregulated in the Δ cra mutant. Further studies demonstrated that Cra directly binds to the promoters of the eps operon, ydiV , and yedQ and activates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production and biofilm formation. Consistent with previous findings that Cra plays a role in transcriptional regulation in response to carbon source availability, the activating effects of Cra were much more pronounced when LTYR-11Z was grown within a gluconeogenic environment than when it was grown within a glycolytic environment. We further demonstrate that the ability of LTYR-11Z to colonize wheat roots is modulated by the availability of carbon sources. Altogether, these results uncover a novel strategy utilized by LTYR-11Z to achieve host colonization in response to carbon nutrition in the environment, in which Cra bridges a connection between carbon metabolism and colonization capacity of LTYR-11Z. IMPORTANCE Rapid and appropriate response to environmental signals is crucial for bacteria to adapt to competitive environments and to establish interactions with their hosts. Efficient colonization and persistence within the host are controlled by various regulatory factors that respond to specific environmental cues. The most common is nutrient availability. In this work, we unraveled the pivotal role of Cra in regulation of colonization ability of Pantoea alhagi LTYR-11Z in response to carbon source availability. Moreover, we identified three novel members of the Cra regulon involved in EPS synthesis, regulation of flagellar biosynthesis, and synthesis of c-di-GMP and propose a working model to explain the Cra-mediated regulatory mechanism that links carbon metabolism to host colonization. This study elucidates the regulatory role of Cra in bacterial attachment and colonization of plants, which raises the possibility of extending our studies to other bacteria associated with plant and human health.

scholarly journals Carbon Source Dependence and Photostimulation of Conidiation in Hypocrea atroviridis

2007 ◽  
Vol 74 (1) ◽  
pp. 245-250 ◽  
Author(s):  
Martina A. Friedl ◽  
Christian P. Kubicek ◽  
Irina S. Druzhinina
Keyword(s):  
Carbon Source ◽  
Cyclic Amp ◽  
Parental Strain ◽  
Carbon Sources ◽  
Spore Formation ◽  
Blue Light Receptor ◽  
Small Set ◽  
Prime Determinant ◽  
Catalytic Role

ABSTRACT Hypocrea atroviridis is frequently used as a photomorphogenetic model due to its ability to conidiate upon exposure to light. Light is thereby believed to be the primary trigger for spore formation. In contrast, we show here that conidiation is primarily carbon source dependent and that illumination plays a catalytic role; of a total of 95 tested carbon sources, only a small set of carbohydrates, polyols, and sugar acids allowed conidiation in darkness, and on most of them, conidiation was significantly more strongly expressed in light. In addition, there are also a number of carbon sources on which H. atroviridis conidiates in darkness, but light does not further stimulate the process. Yet on another small set of carbon sources (l-sorbitol, d-fucose, d- and l-arabinose, and erythritol), H. atroviridis shows better sporulation in darkness than in light. No sporulation was observed on organic acids and amino acids. Mutants with deletions in the two blue-light receptor proteins BLR-1 and BLR-2 generally showed weaker conidiation on a smaller number of carbon sources than did the parental strain, yet they clearly sporulated on 15 and 27 of the 95 carbon sources tested, respectively. Of the carbon sources supporting sporulation, only 11 supported the conidiation of both mutants, suggesting that the BLR-1 and BLR-2 receptors are variously involved in the carbon source-dependent regulation of spore formation. The addition of cyclic AMP, which has been reported to lead to conidiation in darkness, both positively and negatively affected sporulation and resulted in different effects in the parental strain and the two Δblr mutants. Our data show that the carbon source is the prime determinant for conidiation and that it influences the organism's regulation of conidiation by means of BLR-1 and BLR-2 and their cross talk with cyclic AMP.

scholarly journals Magnesium and the Role of mgtC in Growth of Salmonella typhimurium

1998 ◽  
Vol 66 (8) ◽  
pp. 3802-3809 ◽  
Author(s):  
Mary Beth C. Moncrief ◽  
Michael E. Maguire
Keyword(s):  
Salmonella Typhimurium ◽  
Minimal Medium ◽  
Regulatory System ◽  
Low Ph ◽  
Transport Systems ◽  
Lag Phase ◽  
Primary Role ◽  
Cation Uptake ◽  
P Type

ABSTRACT Salmonella typhimurium has three distinct transport systems for Mg2+: CorA, MgtA, and MgtB. ThemgtCB operon encodes two proteins, MgtC, a hydrophobic protein with a predicted molecular mass of 22.5 kDa, and MgtB, a 102-kDa P-type ATPase Mg2+ transport protein. ThemgtCB locus has been identified as part of a newSalmonella pathogenicity island, SPI-3. Transcription ofmgtCB is regulated by extracellular Mg2+ via the two-component PhoPQ regulatory system important for virulence. To elucidate MgtC’s role in a low-Mg2+ environment, we looked at growth and transport in strains lacking the CorA and MgtA Mg2+ transporters but expressing MgtB, MgtC, or both.mgtC mgtB+ and mgtC+mgtB+ strains exhibited growth in N minimal medium without added Mg2+ with a 1- to 2-h lag phase. AnmgtC+ mgtB strain was also able to grow in N minimal medium without added Mg2+ but only after a 24-h lag phase. In N minimal medium containing 10 mM Mg2+, all strains grew after a short lag phase; the mgtC+mgtB strain grew to a higher optical density at 600 nm than anmgtC+ mgtB+ strain and was comparable to wild type. The lengthy lag phase before growth in anmgtC+ mgtB strain was not due to lack of expression of MgtC. Western blot analysis indicated that substantial MgtC protein is present by 2 h after suspension in N minimal medium. Surprisingly, in an mgtC+mgtB+ strain, MgtC was undetectable during Mg2+ starvation, although large amounts of MgtB were observed. The lack of expression of MgtC is not dependent on functional MgtB, since a strain carrying a nonfunctional MgtB with a mutation (D379A) also did not make MgtC. Since, during invasion of eukaryotic cells, S. typhimurium appears to be exposed to a low-pH as well as a low-Mg2+ environment, the growth of anmgtC+ mgtB strain was tested at low pH with and without added Mg2+. While significant quantities of MgtC could be detected after suspension at pH 5.2, themgtC+ mgtB strain was unable to grow at pH 5.2 whether or not Mg2+ was present. Finally, using63Ni2+ and 57Co2+ as alternative substrates for the unavailable28Mg2+, cation uptake could not be detected in an mgtC+ mgtB strain after Mg2+starvation. We conclude that MgtC is not a Mg2+ transporter and that it does not have a primary role in the survival of S. typhimurium at low pH.

scholarly journals Role of Escherichia coli in Biofuel Production

2016 ◽  
Vol 9 ◽  
pp. MBI.S10878 ◽  
Author(s):  
Veerendra Koppolu ◽  
Veneela KR Vasigala
Keyword(s):  
Escherichia Coli ◽  
Renewable Energy ◽  
Renewable Energy Sources ◽  
Carbon Sources ◽  
Volumetric Productivity ◽  
Biofuel Production ◽  
Energy Sources ◽  
E Coli ◽  
High Volumetric Productivity

Increased energy consumption coupled with depleting petroleum reserves and increased greenhouse gas emissions have renewed our interest in generating fuels from renewable energy sources via microbial fermentation. Central to this problem is the choice of microorganism that catalyzes the production of fuels at high volumetric productivity and yield from cheap and abundantly available renewable energy sources. Microorganisms that are metabolically engineered to redirect renewable carbon sources into desired fuel products are contemplated as best choices to obtain high volumetric productivity and yield. Considering the availability of vast knowledge in genomic and metabolic fronts, Escherichia coli is regarded as a primary choice for the production of biofuels. Here, we reviewed the microbial production of liquid biofuels that have the potential to be used either alone or in combination with the present-day fuels. We specifically highlighted the metabolic engineering and synthetic biology approaches used to improve the production of biofuels from E. coli over the past few years. We also discussed the challenges that still exist for the biofuel production from E. coli and their possible solutions.

scholarly journals In Vivo Analysis of HPr Reveals a Fructose-Specific Phosphotransferase System That Confers High-Affinity Uptake in Streptomyces coelicolor

2003 ◽  
Vol 185 (3) ◽  
pp. 929-937 ◽  
Author(s):  
Harald Nothaft ◽  
Stephan Parche ◽  
Annette Kamionka ◽  
Fritz Titgemeyer
Keyword(s):  
Carbon Source ◽  
Glucose Repression ◽  
Streptomyces Coelicolor ◽  
Carbon Sources ◽  
Glycerol Kinase ◽  
Transcriptional Analysis ◽  
Phosphotransferase System ◽  
Gram Positive ◽  
High Affinity

ABSTRACT HPr, the histidine-containing phosphocarrier protein of the bacterial phosphotransferase system (PTS), serves multiple functions in carbohydrate uptake and carbon source regulation in low-G+C-content gram-positive bacteria and in gram-negative bacteria. To assess the role of HPr in the high-G+C-content gram-positive organism Streptomyces coelicolor, the encoding gene, ptsH, was deleted. The ptsH mutant BAP1 was impaired in fructose utilization, while growth on other carbon sources was not affected. Uptake assays revealed that BAP1 could not transport appreciable amounts of fructose, while the wild type showed inducible high-affinity fructose transport with an apparent Km of 2 μM. Complementation and reconstitution experiments demonstrated that HPr is indispensable for a fructose-specific PTS activity. Investigation of the putative fruKA gene locus led to identification of the fructose-specific enzyme II permease encoded by the fruA gene. Synthesis of HPr was not specifically enhanced in fructose-grown cells and occurred also in the presence of non-PTS carbon sources. Transcriptional analysis of ptsH revealed two promoters that are carbon source regulated. In contrast to what happens in other bacteria, glucose repression of glycerol kinase was still operative in a ptsH background, which suggests that HPr is not involved in general carbon regulation. However, fructose repression of glycerol kinase was lost in BAP1, indicating that the fructose-PTS is required for transduction of the signal. This study provides the first molecular genetic evidence of a physiological role of the PTS in S. coelicolor.

scholarly journals Carbon Source-Dependent Phosphorylation of Hexokinase PII and Its Role in the Glucose-Signaling Response in Yeast

1998 ◽  
Vol 18 (5) ◽  
pp. 2940-2948 ◽  
Author(s):  
Francisca Randez-Gil ◽  
Pascual Sanz ◽  
Karl-Dieter Entian ◽  
Jose Antonio Prieto
Keyword(s):  
Carbon Source ◽  
Glucose Repression ◽  
Carbon Sources ◽  
Glucose Signaling ◽  
Regulatory Effects ◽  
Metabolic Signal ◽  
Signal Transductions ◽  
Mutant Cells

ABSTRACT The HXK2 gene is required for a variety of regulatory effects leading to an adaptation for fermentative metabolism inSaccharomyces cerevisiae. However, the molecular basis of the specific role of Hxk2p in these effects is still unclear. One important feature in order to understand the physiological function of hexokinase PII is that it is a phosphoprotein, since protein phosphorylation is essential in most metabolic signal transductions in eukaryotic cells. Here we show that Hxk2p exists in vivo in a dimeric-monomeric equilibrium which is affected by phosphorylation. Only the monomeric form appears phosphorylated, whereas the dimer does not. The reversible phosphorylation of Hxk2p is carbon source dependent, being more extensive on poor carbon sources such as galactose, raffinose, and ethanol. In vivo dephosphorylation of Hxk2p is promoted after addition of glucose. This effect is absent in glucose repression mutants cat80/grr1, hex2/reg1, andcid1/glc7. Treatment of a glucose crude extract fromcid1-226 (glc7-T152K) mutant cells with λ-phosphatase drastically reduces the presence of phosphoprotein, suggesting that CID1/GLC7 phosphatase together with its regulatory HEX2/REG1 subunit are involved in the dephosphorylation of the Hxk2p monomer. An HXK2 mutation encoding a serine-to-alanine change at position 15 [HXK2(S15A)] was to clarify the in vivo function of the phosphorylation of hexokinase PII. In this mutant, where the Hxk2 protein is unable to undergo phosphorylation, the cells could not provide glucose repression of invertase. Glucose induction ofHXT gene expression is also affected in cells expressing the mutated enzyme. Although we cannot rule out a defect in the metabolic state of the cell as the origin of these phenomena, our results suggest that the phosphorylation of hexokinase is essential in vivo for glucose signal transduction.

scholarly journals Mig1 localization exhibits biphasic behavior which is controlled by both metabolic and regulatory roles of the sugar kinases

2020 ◽  
Vol 295 (6) ◽  
pp. 1489-1500
Author(s):  
Gregor W. Schmidt ◽  
Niek Welkenhuysen ◽  
Tian Ye ◽  
Marija Cvijovic ◽  
Stefan Hohmann
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Localization ◽  
Essential Role ◽  
Carbon Sources ◽  
Transcriptional Repressor ◽  
Energy Sources ◽  
Nucleocytoplasmic Shuttling

Abstract Glucose, fructose and mannose are the preferred carbon/energy sources for the yeast Saccharomyces cerevisiae. Absence of preferred energy sources activates glucose derepression, which is regulated by the kinase Snf1. Snf1 phosphorylates the transcriptional repressor Mig1, which results in its exit from the nucleus and subsequent derepression of genes. In contrast, Snf1 is inactive when preferred carbon sources are available, which leads to dephosphorylation of Mig1 and its translocation to the nucleus where Mig1 acts as a transcription repressor. Here we revisit the role of the three hexose kinases, Hxk1, Hxk2 and Glk1, in glucose de/repression. We demonstrate that all three sugar kinases initially affect Mig1 nuclear localization upon addition of glucose, fructose and mannose. This initial import of Mig1 into the nucleus was temporary; for continuous nucleocytoplasmic shuttling of Mig1, Hxk2 is required in the presence of glucose and mannose and in the presence of fructose Hxk2 or Hxk1 is required. Our data suggest that Mig1 import following exposure to preferred energy sources is controlled via two different pathways, where (1) the initial import is regulated by signals derived from metabolism and (2) continuous shuttling is regulated by the Hxk2 and Hxk1 proteins. Mig1 nucleocytoplasmic shuttling appears to be important for the maintenance of the repressed state in which Hxk1/2 seems to play an essential role.

Role of Toxin Concentration and Second Carbon Source in Microbial Transformation of Aflatoxin B1 by Flavobacterium aurantiacum

1995 ◽  
Vol 58 (9) ◽  
pp. 1042-1044 ◽  
Author(s):  
J. E. LINE ◽  
R. E. BRACKETT
Keyword(s):  
Carbon Source ◽  
Significant Influence ◽  
Aflatoxin B1 ◽  
Microbial Transformation ◽  
Energy Sources ◽  
Test Medium ◽  
Nutrient Source ◽  
Toxin Concentration ◽  
Cell Supernatant

The aflatoxins are toxic and carcinogenic mycotoxins which contaminate a variety of foods and feeds. The bacterium Flavobacterium aurantiacum NRRL B-184 has been previously shown to be effective in degrading aflatoxin B1) in liquid test medium as well as in several food types. The purpose of this study was to investigate the effects of an added nutrient source and added aflatoxin on the ability of F. aurantiacum to degrade aflatoxin B1. Radioactively labeled aflatoxin B1 was added to test solutions containing cells in phosphate buffer or tryptic soy broth. Nonlabeled aflatoxin B1 was also added to similar flasks. Analysis of radioactive CO2 and water- and chloroform-soluble portions of the cell supernatant fluids revealed that neither added nutrients nor added nonlabeled toxin had a significant influence on the microbial transformation of aflatoxin B1 These results suggest that the microbial degradation of aflatoxin by F. aurantiacum is probably a mineralization phenomenon and not a co-metabolism. The ability of this organism to detoxify aflatoxin without the need for exogenous energy sources could be important to future endeavors attempting to use the organism, or the mechanisms responsible, in fermentation reactions.

scholarly journals Key Role of Ser562/661 in Snf1-Dependent Regulation of Cat8p in Saccharomyces cerevisiae and Kluyveromyces lactis

2004 ◽  
Vol 24 (10) ◽  
pp. 4083-4091 ◽  
Author(s):  
Godefroid Charbon ◽  
Karin D. Breunig ◽  
Ruddy Wattiez ◽  
Jean Vandenhaute ◽  
Isabelle Noël-Georis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Target Genes ◽  
Kluyveromyces Lactis ◽  
Active Form ◽  
Phosphorylation Site ◽  
Carbon Sources ◽  
Mutant Form ◽  
Zinc Cluster

ABSTRACT Utilization of nonfermentable carbon sources by Kluyveromyces lactis and Saccharomyces cerevisiae requires the Snf1p kinase and the Cat8p transcriptional activator, which binds to carbon source-responsive elements of target genes. We demonstrate that KlSnf1p and KlCat8p from K. lactis interact in a two-hybrid system and that the interaction is stronger with a kinase-dead mutant form of KlSnf1p. Of two putative phosphorylation sites in the KlCat8p sequence, serine 661 was identified as a key residue governing KlCat8p regulation. Serine 661 is located in the middle homology region, a regulatory domain conserved among zinc cluster transcription factors, and is part of an Snf1p consensus phosphorylation site. Single mutations at this site are sufficient to completely change the carbon source regulation of the KlCat8p transactivation activity observed. A serine-to-glutamate mutant form mimicking constitutive phosphorylation results in a nearly constitutively active form of KlCat8p, while a serine-to-alanine mutation has the reverse effect. Furthermore, it is shown that KlCat8p phosphorylation depends on KlSNF1. The Snf1-Cat8 connection is evolutionarily conserved: mutation of corresponding serine 562 of ScCat8p gave similar results in S. cerevisiae. The enhanced capacity of ScCat8S562E to suppress the phenotype caused by snf1 strengthens the hypothesis of direct phosphorylation of Cat8p by Snf1p. Unlike that of S. cerevisiae ScCAT8, KlCAT8 transcription is not carbon source regulated, illustrating the prominent role of posttranscriptional regulation of Cat8p in K. lactis.

SISTEM AUTOMATIC SWITCH REDUNDANT UPS UNTUK BEBAN ESSENSIAL

2019 ◽  
Vol 5 (1) ◽  
pp. 35-45
Author(s):  
Markus Dwiyanto Tobi ◽  
Alimuddin Mappa
Keyword(s):  
Power Supply ◽  
Working Condition ◽  
Control Circuit ◽  
Energy Sources ◽  
Main Equipment ◽  
Telecommunication Equipment ◽  
Input Condition ◽  
Research Designs ◽  
Switch Circuit

The role of the power supply device is to produce, process and distribute energy sources. Telecommunication equipment can only operate if it has continuous supply. Therefore, to maintain the continuity of the supply, a UPS (Uninterruptable Power Supply) device system is needed so that the supply to the Essential Load device will remain available so that continuity will be maintained. This research designs and proposes how a series of automatic redundant switch systems on UPS to ensure the availability of power supply for the main equipment of telecommunications systems. The Auto switch circuit is designed to have 3 (three) working stages which will trigger the relay driver as control circuit, namely the normal working condition of the contactor input K1 is present, the input condition is zero (lost), and the input condition is present. This system can automatically supply power to telecommunications equipment.

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