Nutritional requirements of mutants of Escherichia coli resistant to gamma irradiation

1968 ◽  
Vol 14 (6) ◽  
pp. 711-715 ◽  
Author(s):  
Haskel Robern ◽  
F. S. Thatcher
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Basal Medium ◽  
Nutritional Requirements ◽  
Lag Phase ◽  
Wild Type ◽  
Γ Irradiation ◽  
Mineral Salts ◽  
Peptone Medium ◽  
Purines And Pyrimidines

The nutritional requirements of three mutants resistant to γ irradiation were investigated. The mutants were derived from a wild type strain of Escherichia coli and were arbitrarily designated in order of resistance as 1γ < 6γ < 12γ.Studies of growth of these strains in basal medium (mineral salts – glucose), peptone medium, and a complete chemically defined (CCD) medium, showed that the wild type and 1γ mutant grew in all media, but the 1γ mutant exhibited a prolonged lag phase in basal medium. The 6γ and 12γ mutants did not grow in basal medium but grew in peptone medium and in CCD medium (mineral salts, glucose, amino acids, purines, and pyrimidines) after a lag of several hours. None of the amino acids, purines, and pyrimidines were required for growth by the 1γ mutant, but leucine, methionine, and valine were stimulatory. The 6γ mutant required leucine, methionine, and proline, while threonine and valine were marked stimulants. The 12γ mutant required leucine, methionine, proline, valine, arginine, cysteine, histidine, tryptophan, and uracil or cytosine. Threonine was a strong stimulant for this strain. Thus, the nutritional requirements of the mutants resistant to γ irradiation increased with increased resistance to γ irradiation, and compounds which stimulated growth of a mutant with lower resistance to irradiation became essential for the mutants exhibiting a higher resistance.

INHIBITION OF GROWTH OF PSEUDOMONAS DENITRIFICANS BY AMINO ACIDS

1966 ◽  
Vol 12 (6) ◽  
pp. 1095-1098 ◽  
Author(s):  
Horace J. Daniels
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Basal Medium ◽  
Ammonium Phosphate ◽  
Complete Medium ◽  
Mineral Salts ◽  
Culture Studies ◽  
Pseudomonas Denitrificans ◽  
Inhibition Of Growth ◽  
Amino Acid Mixtures

A large number of amino acids failed to support growth of Pseudomonas denitrificans in a basal medium composed of glucose, ammonium phosphate, and other mineral salts. Inability of an amino acid to support growth correlated well with its inhibitory action in a complete medium made up by adding L-glutamic acid to the basal medium. D-Amino acids were more toxic than the corresponding L-forms, and neutral amino acids were more toxic than acidic amino acids. Basic amino acids which were least toxic supported the best growth. The danger of the indiscriminate use of amino acid mixtures for culture studies is discussed.

scholarly journals Fermentation of Glycerol to Succinate by Metabolically Engineered Strains of Escherichia coli

2010 ◽  
Vol 76 (8) ◽  
pp. 2397-2401 ◽  
Author(s):  
Xueli Zhang ◽  
K. T. Shanmugam ◽  
Lonnie O. Ingram
Keyword(s):  
Escherichia Coli ◽  
Electron Acceptors ◽  
Carbon Flow ◽  
Glycerol Dehydrogenase ◽  
Glycerol Metabolism ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
Mineral Salts ◽  
Succinate Production ◽  
Fermentation Products

ABSTRACT The fermentative metabolism of Escherichia coli was reengineered to efficiently convert glycerol to succinate under anaerobic conditions without the use of foreign genes. Formate and ethanol were the dominant fermentation products from glycerol in wild-type Escherichia coli ATCC 8739, followed by succinate and acetate. Inactivation of pyruvate formate-lyase (pflB) in the wild-type strain eliminated the production of formate and ethanol and reduced the production of acetate. However, this deletion slowed growth and decreased cell yields due to either insufficient energy production or insufficient levels of electron acceptors. Reversing the direction of the gluconeogenic phosphoenolpyruvate carboxykinase reaction offered an approach to solve both problems, conserving energy as an additional ATP and increasing the pool of electron acceptors (fumarate and malate). Recruiting this enzyme through a promoter mutation (pck*) to increase expression also increased the rate of growth, cell yield, and succinate production. Presumably, the high NADH/NAD+ ratio served to establish the direction of carbon flow. Additional mutations were also beneficial. Glycerol dehydrogenase and the phosphotransferase-dependent dihydroxyacetone kinase are regarded as the primary route for glycerol metabolism under anaerobic conditions. However, this is not true for succinate production by engineered strains. Deletion of the ptsI gene or any other gene essential for the phosphotranferase system was found to increase succinate yield. Deletion of pflB in this background provided a further increase in the succinate yield. Together, these three core mutations (pck*, ptsI, and pflB) effectively redirected carbon flow from glycerol to succinate at 80% of the maximum theoretical yield during anaerobic fermentation in mineral salts medium.

Effets des purines et des pyrimidines sur la croissance de Corynebacterium sepedonicum (Spiek. & Kott.) Skapt. & Burkh.

1968 ◽  
Vol 14 (4) ◽  
pp. 475-478 ◽  
Author(s):  
Lucien M. Bordeleau ◽  
Robert-A. Lachance
Keyword(s):  
Amino Acids ◽  
Nucleic Acids ◽  
Synthetic Medium ◽  
Limiting Factor ◽  
Mineral Salts ◽  
Corynebacterium Sepedonicum ◽  
Purines And Pyrimidines

The effects of purines and pyrimidines on the growth of Corynebacterium sepedonicum were studied in a synthetic medium containing amino acids, vitamins, mineral salts, and glucose. Among four purines tested, only adenine inhibited the growth of the organism. Hypoxanthine and guanine reversed the inhibition caused by adenine. None of four pyrimidines tested affected the growth. In the presence of pyrimidines, only hypoxanthine reversed the inhibition caused by adenine. It appears that purines and pyrimidines do not stimulate the growth of C. sepedonicum and that the synthesis of nucleic acids from these bases is not a limiting factor in the growth of the organism.

scholarly journals Hydrophilic Domain II of Escherichia coli Dr Fimbriae Facilitates Cell Invasion

2005 ◽  
Vol 73 (9) ◽  
pp. 6119-6126 ◽  
Author(s):  
Margaret Das ◽  
Audrey Hart-Van Tassell ◽  
Petri T. Urvil ◽  
Susan Lea ◽  
David Pettigrew ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Cell Invasion ◽  
Cell Entry ◽  
Wild Type ◽  
Alanine Scanning Mutagenesis ◽  
Decay Accelerating Factor ◽  
Fimbrial Subunit ◽  
Hydrophilic Domain ◽  
Intracellular Compartmentalization

ABSTRACT Uropathogenic and diarrheal Escherichia coli strains expressing adhesins of the Dr family bind to decay-accelerating factor, invade epithelial cells, preferentially infect children and pregnant women, and may be associated with chronic or recurrent infections. Thus far, no fimbrial domain(s) that facilitates cell invasion has been identified. We used alanine scanning mutagenesis to replace selected amino acids in hydrophilic domain II of the structural fimbrial subunit DraE and evaluated recombinant mutant DraE for attachment, invasion, and intracellular compartmentalization. The mutation of amino acids V28, T31, G33, Q34, T36, and P40 of DraE reduced or abolished HeLa cell invasion but did not affect attachment. Electron micrographs showed a stepwise entry and fusion of vacuoles containing Escherichia coli mutants T36A and Q34A or corresponding beads with lysosomes, whereas vacuoles with wild-type Dr adhesin showed no fusion. Mutants T31A and Q34A, which were deficient in invasion, appeared to display a reduced capacity for clustering decay-accelerating factor. Our findings suggest that hydrophilic domain II may be involved in cell entry. These data are consistent with the interpretation that in HeLa cells the binding and invasion phenotypes of Dr fimbriae may be separated.

THE APPLICATION OF A NUTRITIONAL GROUPING METHOD TO SOIL FUNGI

1955 ◽  
Vol 33 (3) ◽  
pp. 281-288 ◽  
Author(s):  
R. G. Atkinson ◽  
J. B. Robinson
Keyword(s):  
Amino Acids ◽  
Growth Factors ◽  
Yeast Extract ◽  
Soil Fungi ◽  
Basal Medium ◽  
Maximum Growth ◽  
Potassium Nitrate ◽  
Soil Extract ◽  
Mineral Salts ◽  
Soil Extracts

In tests with seven different liquid media in which the common nitrogen source was potassium nitrate and the carbohydrate substrate was glucose, at a concentration of only 0.1%, most of the 1914 soil fungi isolated fell into one of three nutritional groups requiring, respectively, for maximum growth amino acids, amino acids plus growth factors, or yeast extract. Relatively few isolates required growth factors alone or a combination of yeast and soil extracts. Most of the isolates grew poorly in the basal medium containing only mineral salts, and glucose, with or without soil extract. Although fungi requiring yeast extract were much less frequently isolated from soil on, rather than remote from, tubers grown in a soybean green-manured plot, isolates requiring amino acids, or yeast plus soil extracts, were correspondingly increased on immature and mature tubers, respectively. In a second plot, however, not specially treated, no differences were observed in the nutritional spectra of fungi isolated from the two kinds of soil environment.

scholarly journals Cephem Potentiation by Inactivation of Nonessential Genes Involved in Cell Wall Biogenesis of β-Lactamase-Producing Escherichia coli

2016 ◽  
Vol 61 (3) ◽  
Author(s):  
Kristin R. Baker ◽  
Helga Høeg Sigurðardóttir ◽  
Bimal Jana ◽  
Luca Guardabassi
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Lag Phase ◽  
Growth Curve Analysis ◽  
Wild Type ◽  
Content Type ◽  
Cell Wall Biogenesis ◽  
Genes Encoding ◽  
In The Wild ◽  
Nonessential Genes

ABSTRACT Reversal of antimicrobial resistance is an appealing and largely unexplored strategy in drug discovery. The objective of this study was to identify potential targets for “helper” drugs reversing cephem resistance in Escherichia coli strains producing β-lactamases. A CMY-2-encoding plasmid was transferred by conjugation to seven isogenic deletion mutants exhibiting cephem hypersusceptibility. The effect of each mutation was evaluated by comparing the MICs in the wild type and the mutant harboring the same plasmid. Mutation of two genes encoding proteins involved in cell wall biosynthesis, dapF and mrcB, restored susceptibility to cefoxitin (FOX) and reduced the MICs of cefotaxime and ceftazidime, respectively, from the resistant to the intermediate category according to clinical breakpoints. The same mutants harboring a CTX-M-1-encoding plasmid fell into the intermediate or susceptible category for all three drugs. Individual deletion of dapF and mrcB in a clinical isolate of CTX-M-15-producing E. coli sequence type 131 (ST131) resulted in partial reversal of ceftazidime and cefepime resistance but did not reduce MICs below susceptibility breakpoints. Growth curve analysis indicated no fitness cost in a ΔmrcB mutant, whereas a ΔdapF mutant had a 3-fold longer lag phase than the wild type, suggesting that drugs targeting DapF may display antimicrobial activity, in addition to synergizing with selected cephems. DapF appeared to be a potential FOX helper drug target candidate, since dapF inactivation resulted in synergistic potentiation of FOX in the genetic backgrounds tested. The study showed that individual inactivation of two nonessential genes involved in cell wall biogenesis potentiates cephem activity according to drug- and strain-specific patterns.

Nutritional Factors Affecting Growth and Production of Antimicrobial Substances by Streptococcus lactis subsp. diacetylactis S1-67/C

1983 ◽  
Vol 46 (6) ◽  
pp. 514-517 ◽  
Author(s):  
N. S. REDDY ◽  
B. RANGANATHAN
Keyword(s):  
Amino Acids ◽  
Yeast Extract ◽  
Casein Hydrolysate ◽  
Basal Medium ◽  
Good Growth ◽  
Mineral Salts ◽  
Nutritional Factors ◽  
Maximum Production ◽  
Antimicrobial Substances ◽  
Streptococcus Lactis

The present study pertains to the effect of nutritional factors on the growth and production of antimicrobial substances (AS) by Streptococcus lactis subsp. diacetylactis S1-67/C. Among nine media tested, yeast extract dextrose broth supported good growth and maximum production of AS. Addition of beef extract and yeast extract at 1.0 and 0.6% levels, respectively, increased growth as well as production of AS. Of ten carbohydrates examined, maximum production of AS was achieved with 1% glucose followed by fructose, 4% molasses, lactose, sucrose, galactose, mannitol, maltose and 2% molasses. Xylose inhibited production of AS, although it stimulated growth of the organism. Peptone, tryptone and tryptose (each at the 1.5% level) significantly stimulated production of AS. Other nitrogen sources, including soytone, casein hydrolysate and proteose peptone, retarded production of inhibitory substances. Among the amino acids, L-leucine, DL-methionine and L-glutamic acid were most essential for growth and production of AS, whereas L-lysine, L-proline, DL-serine, DL-asparatic acid, L-arginine-HCl and DL-tryptophan were stimulatory. Other amino acids such as DL-ornithine, L-cysteine-HCl and DL-citrulline slightly stimulated AS production. In the presence of cynocobalmin, niacin, folic acid, calcium pantothenate and riboflavin, S. lactis subsp. diacetylactis S1-67/C produced maximum amounts of inhibitory substances. Omission of individual mineral salts from the basal medium did not affect production of AS by the organism.

scholarly journals Chemotaxis of Escherichia coli to Pyrimidines: a New Role for the Signal Transducer Tap

2007 ◽  
Vol 190 (3) ◽  
pp. 972-979 ◽  
Author(s):  
Xianxian Liu ◽  
Rebecca E. Parales
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Growth Conditions ◽  
Wild Type ◽  
E Coli ◽  
C Terminus ◽  
Signaling Domain ◽  
Chemotaxis Proteins ◽  
Periplasmic Domain

ABSTRACT Escherichia coli exhibits chemotactic responses to sugars, amino acids, and dipeptides, and the responses are mediated by methyl-accepting chemotaxis proteins (MCPs). Using capillary assays, we demonstrated that Escherichia coli RP437 is attracted to the pyrimidines thymine and uracil and the response was constitutively expressed under all tested growth conditions. All MCP mutants lacking the MCP Tap protein showed no response to pyrimidines, suggesting that Tap, which is known to mediate dipeptide chemotaxis, is required for pyrimidine chemotaxis. In order to confirm the role of Tap in pyrimidine chemotaxis, we constructed chimeric chemoreceptors (Tapsr and Tsrap), in which the periplasmic and cytoplasmic domains of Tap and Tsr were switched. When Tapsr and Tsrap were individually expressed in an E. coli strain lacking all four native MCPs, Tapsr mediated chemotaxis toward pyrimidines and dipeptides, but Tsrap did not complement the chemotaxis defect. The addition of the C-terminal 19 amino acids from Tsr to the C terminus of Tsrap resulted in a functional chemoreceptor that mediated chemotaxis to serine but not pyrimidines or dipeptides. These results indicate that the periplasmic domain of Tap is responsible for detecting pyrimidines and the Tsr signaling domain confers on Tapsr the ability to mediate efficient chemotaxis. A mutant lacking dipeptide binding protein (DBP) was wild type for pyrimidine taxis, indicating that DBP, which is the primary chemoreceptor for dipeptides, is not responsible for detecting pyrimidines. It is not yet known whether Tap detects pyrimidines directly or via an additional chemoreceptor protein.

scholarly journals Altered Oligomerization Properties of N316 Mutants of Escherichia coli TyrR

2008 ◽  
Vol 190 (24) ◽  
pp. 8238-8243 ◽  
Author(s):  
Takashi Koyanagi ◽  
Takane Katayama ◽  
Hideyuki Suzuki ◽  
Hidehiko Kumagai
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Amino Acids ◽  
Gel Filtration ◽  
Aromatic Amino Acids ◽  
Transcriptional Regulator ◽  
Wild Type ◽  
Oligomer Formation ◽  
Regulatory Properties

ABSTRACT The transcriptional regulator TyrR is known to undergo a dimer-to-hexamer conformational change in response to aromatic amino acids, through which it controls gene expression. In this study, we identified N316D as the second-site suppressor of Escherichia coli TyrRE274Q, a mutant protein deficient in hexamer formation. N316 variants exhibited altered in vivo regulatory properties, and the most drastic changes were observed for TyrRN316D and TyrRN316R mutants. Gel filtration analyses revealed that the ligand-mediated oligomer formation was enhanced and diminished for TyrRN316D and TyrRN316R, respectively, compared with the wild-type TyrR. ADP was substituted for ATP in the oligomer formation of TyrRN316D.

scholarly journals Engineered Cyanophycin Synthetase (CphA) from Nostoc ellipsosporum Confers Enhanced CphA Activity and Cyanophycin Accumulation to Escherichia coli

2006 ◽  
Vol 72 (12) ◽  
pp. 7652-7660 ◽  
Author(s):  
Tran Hai ◽  
Kay M. Frey ◽  
Alexander Steinbüchel
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Dry Matter ◽  
Wild Type ◽  
Acinetobacter Baylyi ◽  
E Coli ◽  
Recombinant Cells ◽  
Hydrophobic Amino Acids ◽  
Type Gene ◽  
Nostoc Ellipsosporum

ABSTRACT The cyanophycin (CGP) synthetase gene (cphA NE1) of the transposon-induced argL mutant NE1 of the cyanobacterium Nostoc ellipsosporum, which exhibits a CGP-leaky phenotype during diazotrophical growth, was cloned and expressed in Escherichia coli strain TOP10. Its amino acid sequence exhibited high similarities to CphAs of other cyanobacteria. Recombinant cells of E. coli, which harbored a fragment comprising the complete cphA NE1 gene plus 400 bp of its downstream region in colinear orientation to the lacZ promoter, accumulated CGP up to 17 and 8.5% (wt/wt) of cellular dry matter (CDM) if cultivated in complex medium in the presence or absence of isopropyl-β-d-thiogalactopyranoside, respectively. Two truncated CphAs, lacking 31 (CphANE1del96) or 59 (CphANE1del180) amino acids of the C-terminal region, were derived from cphA NE1 by deleting 96 or 180 bp from its 3′ region through the introduction of stop codons. In comparison to the wild-type gene, cphA NE1del96 conferred about 2.1- to 2.2-fold-higher enzyme activity (up to 5.75 U/mg protein) on E. coli. Furthermore, these cells accumulated about twofold more CGP (up to 34.5% [wt/wt] of CDM) than cells expressing the wild-type gene. An engineered CphA possessing significantly enhanced activity and conferring the highest CGP content on E. coli is demonstrated. In contrast, CphANE1del180 was inactive and did not confer CGP accumulation on E. coli. Interestingly, a short conserved stretch of 4 to 5 hydrophobic amino acids is located in the protein region present in CphANE1del96 but absent in CphANE1del180. In addition, CphANE1 and CphANE1del96 are, besides CphA from Acinetobacter baylyi, the only CphAs exhibiting rigid substrate specificities that do not enable the incorporation of lysine instead of arginine into CGP.

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