bluuebunny/crossref_metadata_2025 huggingface dataset:
Lytic Enzyme from Lysates of
Streptomyces venezuelae
Infected with Actinophage MSP2
Authors: Meinke William J. , Jones Lily A.
Published: January 2020

A lytic enzyme was purified 600-fold with 12% recovery from lysates of
Streptomyces venezuelae
S13 infected with actinophage MSP2. The purified enzyme preparation was homogeneous as shown by polyacrylamide electrophoresis. The enzyme was active over a
p
H range 6.0 to 9.0 with a maximum at
p
H 7.5. The
p
H profile for stability was sharp, with an optimum at
p
H 7.5. Maximal activity occurred between 30 and 35 C. The enzyme was stable at 20 C or less. A 30-min exposure to 25, 30, 35, 40, 45, and 50 C produced an inactivation of 3, 40, 77, 82, 93, and 100%, respectively. Lytic activity was stimulated fivefold by either 5 × 10
−3
m
Mg
2+
or Mn
2+
and three- and twofold by Ca
2+
and Ba
2+
, respectively. Addition of Na
+
, K
+
, NH
4
+
, or Li
+
to the tris(hydroxymethyl)aminomethane-hydrochloride buffer did not alter the rate of lysis. Enzyme activity was inhibited 74 and 27% by 10
−4
and 10
−5
m
ethylenediaminetetraacetic acid (EDTA), respectively. The inhibition by EDTA was reversed partially by addition of Mg
2+
. Lytic activity was abolished by either 5 × 10
−4
m
HgCl
2
or
p
-hydroxymercuribenzoate, whereas 5 × 10
−4
m
CuSO
4
inhibited 72%. Cell wall solubilization paralleled the release of
N
-terminal amino groups and reached a level of 0.23 μmole per mg of cell walls. No release of reducing power was detected in treated or untreated cell wall suspensions. Tests for proteolytic activity were negative.
Effect of Benzo(a)pyrene and Piperonyl Butoxide on Formation of Respiratory System, Phospholipids, and Carotenoids of
Staphylococcus aureus
Authors: Joyce Gay H. , White David C.
Published: January 2020

Staphylococcus aureus
formed an electron transport system when exponentially growing cells were aerated. Formation of the electron transport system occurred concomitantly with increases in the phospholipids and the carotenoids. The addition of piperonyl butoxide or benzo(a)pyrene at the onset of aeration (i) slowed the formation of the electron transport system, (ii) both inhibited cytochrome oxidase
o
synthesis and decreased its stability, (iii) simultaneously depressed the increase in total phospholipid (especially cardiolipin), and (iv) depressed the synthesis of the carotenoid rubixanthin. Benzo(a)pyrene was the more inhibitory of the two, both on the rate of synthesis of the electron transport system and on rubixanthin formation. Evidence obtained with the inhibitors suggested that inhibition of the lipid synthesis was related to the formation of the electron transport system.
Inhibitory Effects and Metabolism of 5-Fluoropyrimidine Derivatives in Pneumococcus
Authors: Bean Barry , Tomasz Alexander
Published: January 2020

5-Fluorouracil (FU), 5-fluorocytosine, and the riboside and deoxyriboside derivatives of these fluoropyrimidines each exhibit a different spectrum of inhibitory effects in pneumococci. The biochemical basis of this finding seems to be the extremely low level of nucleoside phosphorylase (hydrolase) and
N
-trans-deoxyribosylase activity in pneumococcus and the consequent, relatively limited metabolic interconversion of the different fluoropyrimidines, which can therefore selectively affect one or the other of the several drug-sensitive biochemical reactions in this bacterium. Special attention was paid to the effect of fluoropyrimidines on the metabolism of cytosine and thymidine. In spite of the fact that FU is converted to both fluorouridine triphosphate and fluorocytidine triphosphate, only fluorouridylate but no fluorocytidylate can be detected in the ribonucleic acid Exogenous FU and fluorouridine also inhibit the synthesis of cytosine nucleotides from supplied uridine in a pyrimidine auxotroph. Thymidine was found to be a poor reversing agent for any of the fluoropyrimidine inhibitions. In both the wild type and in a thymidine-requiring (thymidylate-synthetase deficient) mutant, growing with supplied thymidine in the medium, fluorodeoxyuridine (FUdR) treatment caused cell death and inhibition of the incorporation of radioactive thymidine, adenosine, or uracil into deoxyribonucleic acid. It is suggested that FUdR (or a metabolic derivative) inhibits the transport of phosphorylation of thymidine in this microorganism.
Histidinol Dehydrogenase (
hisD
) Mutants of
Salmonella typhimurium
Authors: Greeb J. , Atkins J. F. , Loper J. C.
Published: January 2020

A multidisciplinary analysis has been applied to over 150
hisD
mutants of
Salmonella typhimurium
in a study of gene-enzyme relationship. The mutants were examined for production of immunologically cross-reacting material by using antibody to purified histidinol dehydrogenase, and for genetic complementation by using a set of F′ factors bearing
Escherichia coli hisD
complementing mutants. Classifications as to missense, nonsense, frameshift, or deletion mutant are proposed on the basis of mutagenesis and suppression tests. For the suppression tests the mutants were examined both by a simultaneous suppression technique and by testing for response to
E. coli
F′ factors bearing a recessive lethal amber and a recessive lethal ochre suppressor. The data are interpreted in relation to the position of the mutations in the recombination and complementation maps and in relation to the known composition of histidinol dehydrogenase. The gene
hisD
appears to be single cistron for the production of a single biosynthetic polypeptide.
Transverse Septum Formation in Budding Cells of the Yeastlike Fungus
Candida albicans
Authors: Shannon James L. , Rothman Alvin H.
Published: January 2020

Septum formation is initiated in
Candida albicans
by an electron transparent primary septum, which is then thickened on both sides to form secondary septa. Primary and secondary septa are incorporated into the bud scar, and secondary septum material only is incorporated into the birth scar.
Extrachromosomal Nature of Hydrogen Sulfide Production in
Escherichia coli
Authors: Layne Porter , Hu A. S. L. , Balows Albert , Davis Betty R.
Published: January 2020

Two strains of
Escherichia coli
which produce hydrogen sulfide appear to have acquired this ability via transfer of genetic material from another genus.
Methionine-Mediated Repression in
Saccharomyces cerevisiae:
a Pleiotropic Regulatory System Involving Methionyl Transfer Ribonucleic Acid and the Product of Gene
eth2
Authors: Cherest H. , Surdin-Kerjan Y. , De Robichon-Szulmajster H.
Published: January 2020

Detailed study of methionine-mediated repression of enzymes involved in methionine biosynthesis in
Saccharomyces cerevisiae
led to classification of these enzymes into two distinct regulatory groups. Group I comprises four enzymes specifically involved in different parts of methionine biosynthesis, namely, homoserine-
O
-transacetylase, homocysteine synthetase, adenosine triphosphate sulfurylase, and sulfite reductase. Repressibility of these enzymes is greatly decreased in strains carrying a genetically impaired methionyl-transfer ribonucleic acid (tRNA) synthetase (mutation
ts
−
296). Conditions leading to absence of repression in the mutant strain have been correlated with a sharp decrease in bulk tRNA
met
charging, whereas conditions which restore repressibility of group I enzymes also restore tRNA
met
charging. These findings implicate methionyl-tRNA in the regulatory process. However, the absence of a correlation in the wild type between methionyl-tRNA charging and the levels of methionine group I enzymes suggests that only a minor iso accepting species of tRNA
met
may be devoted with a regulatory function. Repressibility of the same four enzymes (group I) was also decreased in strains carrying the regulatory mutation
eth2
r
. Although structural genes coding for two of these enzymes, as well as mutations
ts
−
296 and
eth2
r
segregate independently to each other, synthesis of group I enzymes is coordinated. The pleiotropic regulatory system involved seems then to comprise beside a “regulatory methionyl tRNA
met
,” another element, product of gene
eth2
, which might correspond either to an aporepressor protein or to the “regulatory tRNA
met
” itself. Regulation of group II enzymes is defined by response to exogenous methionine, absence of response to either mutations
ts
−
296 and
eth2
r
, and absence of coordinacy with group I enzymes. However, the two enzymes which belong to this group and are both involved in threonine and methionine biosynthesis undergo distinct regulatory patterns. One, aspartokinase, is subject to a bivalent repression exerted by threonine and methionine, and the other, homoserine dehydrogenase, is subject only to methionine-mediated repression. Participation of at least another aporepressor and another corepressor, different from the ones involved in regulation of group I enzymes, is discussed.
Biochemical Bases for the Antimetabolite Action of
l
-Serine Hydroxamate
Authors: Tosa Tetsuya , Pizer Lewis I.
Published: January 2020

The amino acid analogue
l
-serine hydroxamate, which is bacteriostatic for
Escherichia coli
, has been shown to inhibit protein synthesis. The antimetabolite is a competitive inhibitor of seryl-transfer ribonucleic acid (tRNA) synthetase with a
K
i
value of 30 μ
m
. Mutants resistant to
l
-serine hydroxamate have been selected, and three were shown to have seryl-tRNA synthetases with increased
K
i
values. One mutant contains a 3-phosphoglycerate dehydrogenase which is insensitive to inhibition by
l
-serine.
New Mutant Types at the
ade3
Locus of
Saccharomyces cerevisiae
Authors: Lomax Christopher A. , Gross Trevor S. , Woods Robin A.
Published: January 2020

Six mutants, allelic to
ade3
, were isolated after mutagenic treatment of a prototrophic strain of yeast. All six grow on medium supplemented with adenine alone and four respond to histidine. Supplementation with adenine plus histidine or methionine inhibits growth, but a mixture of these three is stimulatory. Heteroallelic diploids formed by the new mutants with the standard
ade3
can resemble either parent or show an intermediate phenotype. The new mutants, unlike standard
ade3
, are not fully epistatic to
ade2
. The activities of three enzymes concerned in tetrahydrofolate metabolism have been assayed in the new and standard
ade3
mutants and wild type. The only difference detected between the new and standard
ade3
was in the levels of 10-formyltetrahydrofolate synthetase. Activity in the new mutants ranged from 36 to 109% of wild type compared with 10 to 12% in the standard
ade3
. Possible mechanisms to account for the varied phenotypes at the
ade3
locus are discussed.
Physiological Studies of Methane and Methanol-Oxidizing Bacteria: Oxidation of C-1 Compounds by
Methylococcus capsulatus
Authors: Patel Ramesh N. , Hoare Derek S.
Published: January 2020

Methylococcus capsulatus
grows only on methane or methanol as its sole source of carbon and energy. Some amino acids serve as nitrogen sources and are converted to keto acids which accumulate in the culture medium. Cell suspensions oxidize methane, methanol, formaldehyde, and formate to carbon dioxide. Other primary alcohols are oxidized only to the corresponding aldehydes. Oxidation of formate by cell suspensions is more sensitive to inhibition by cyanide than is the oxidation of other one carbon compounds. This is due to the cyanide sensitivity of a soluble nicotinamide adenine dinucleotide-specific formate dehydrogenase. Oxidation of formaldehyde and methanol is catalyzed by a nonspecific primary alcohol dehydrogenase which is activated by ammonium ions and is independent of pyridine nucleotides. Some comparisons are made with a strain of
Pseudomonas methanica
.
Regulation of Tryptophan Biosynthetic Enzymes in
Neurospora crassa
Authors: Lester Gabriel
Published: January 2020

The formation of enzymatic activities involved in the biosynthesis of tryptophan in
Neurospora crassa
was examined under various conditions in several strains. With growth-limiting tryptophan, the formation of four enzymatic activities, anthranilic acid synthetase (AAS), anthranilate-5-phosphoribosylpyrophosphate phosphoribosyl transferase (PRAT), indoleglycerol phosphate synthetase (InGPS), and tryptophan synthetase (TS) did not occur coordinately. AAS and TS activities began to increase immediately, whereas PRAT and InGPS activities began to increase only after 6 to 12 hr of incubation. In the presence of amitrole (3-amino-1,2,4-triazole), the formation of TS activity in a wild-type strain was more greatly enhanced than were AAS and InGPS activities. With a
tr-3
mutant, which ordinarily exhibits an elevated TS activity, amitrole did not produce an increase in TS activity greater than that observed on limiting tryptophan. With
tr-3
mutants, the increased levels of TS activity could be correlated with the accumulation of indoleglycerol in the medium; prior genetic blocks which prevented or reduced the synthesis of indoleglycerol also reduced the formation of TS activity. The addition of indoleglycerol to cultures of a double mutant (
tr-1, tr-3
) which could not synthesize indoleglycerol markedly stimulated the production of TS activity but not PRAT activity; the production of TS activity reached the same level with limiting or with excess tryptophan. A model explaining these and other related observations on enzyme formation in
N. crassa
is proposed.
Protein A Mutants ofStaphylococcus aureus
Authors: Forsgren Arne , Nordström Kristina , Philipson Lennart , Sjöquist John
Published: January 2020

Staphylococcus aureusCowan I was exposed to nitrosoguanidine or ethyl-methanesulfonate, and survivors were screened on nutrient agar plates containing rabbit anti-protein A serum for loss of protein A production. More than half of all protein A-deficient mutants also lacked nuclease, coagulase, alpha hemolysin, fibrinolysin, mannitol utilization, and the phage-type pattern. Mutants with a spectrum of these properties were also isolated. Induced or spontaneous reversions of the mutants were observed. The properties of the protein A-deficient mutants suggest that synthesis or release (or both) of a number of extracellular products ofS. aureusis controlled by a common regulatory mechanism.
Apparent Lack of Control by Repression of Arginine Metabolism in Blue-Green Algae
Authors: Hood W. , Carr N. G.
Published: January 2020

Five anabolic and two catabolic enzymes of arginine metabolism were neither repressed nor induced after inclusion of arginine in the growth medium of
Anabaena variabilis
.
Inhibition of Arginyl-Transfer Ribonucleic Acid Synthetase Activity of
Escherichia coli
by Arginine Biosynthetic Precursors
Authors: Yem D. W. , Williams L. S.
Published: January 2020

The arginine biosynthetic precursors, ornithine, citrulline, and argininosuccinate, inhibit arginyl-transfer ribonucleic acid (tRNA) synthetase (EC 6.1.1.13, arginine: soluble RNA ligase, adenosine monophosphate) activity in the in vitro attachment assay system. Ornithine is the most potent, argininosuccinate is next, and citrulline is least effective. The implications of these results are discussed in relation to arginyl-tRNA synthetase activity and the level of the arginine biosynthetic enzymes during conditions of restricted and unrestricted supply of arginine to cells.
Deoxyribonucleic Acid-Dependent Ribonucleic Acid Polymerase Activity in Purified Trachoma Elementary Bodies: Effect of Sodium Chloride on Ribonucleic Acid Transcription
Authors: Sarov Israel , Becker Yechiel
Published: January 2020

Highly purified trachoma elementary bodies (T′ang strain), incubated in the presence of the four nucleoside triphosphates [Mg
2+
, Mn
2+
, 2-mercaptoethanol, tris(hydroxymethyl)aminomethane buffer (
p
H 7.5)] were found to incorporate
3
H-uridine triphosphate (UTP) into ribonucleic acid (RNA) molecules. Eighty-seven per cent of the labeled molecules were sensitive to ribonuclease treatment. In vitro RNA synthesis was almost completely inhibited by actinomycin D. Rifampin was also inhibitory, but allowed some initial RNA synthesis before complete inhibition occurred. When the reaction mixture lacked Mn
2+
, trachoma elementary bodies synthesized, for a limited period, high-molecular-weight RNA species (23 to 24
S
, 16 to 17
S
, and 10 to 11
S
). Addition of 0.2
m
NaCl to the same reaction mixture stimulated and prolonged
3
H-UTP incorporation into the same radioactive RNA species. Addition of 0.001
m
Mn
2+
instead of NaCl also stimulated
3
H-UTP incorporation but prevented the synthesis of the high-molecular-weight RNA species.
Site of Action of the Cord Factor of
Corynebacterium diphtheriae
in Mitochondria
Authors: Kato Masahiko
Published: January 2020

Trehalose-6,6′-dicorynomycolate (T66DCM), the cord factor of
Corynebacterium diphtheriae
, induced in vitro a swelling accompanied with a partially irreversible change of the mitochondrial membrane system in mouse liver. Preincubation of the mitochondrial suspension with T66DCM resulted in an inhibition of phosphorylation coupled to the oxidation of either succinate or a number of reduced nicotinamide adenine dinucleotide-linked substrates and a loss of respiratory control. T66DCM affected both electron transport and phosphorylation at coupling site II and uncoupled respiration and phosphorylation at coupling site III. T66DCM stimulated mitochondrial adenosine triphosphatase. The induction of adenosine triphosphatase by T66DCM and by 2,4-dinitrophenol was additive.
β-Lactamases of R Factors Derived from
Shigella
and
Salmonella
Strains
Authors: Jenkins Philip G. , Drabble William T.
Published: January 2020

R. factors conferring resistance to penicillins and cephalosporins were transferred by conjugation from six strains of
Shigella
and from four strains of
Salmonella typhimurium
to a standard strain of
S. typhimurium
LT2. The β-lactamases produced were then characterized by using cell-free extracts. The enzymes were of two types, I and II, with respect to specific activity against benzyl penicillin, substrate profile,
K
m
,
p
H optimum, temperature optimum, inhibition by chloride and nitrate ions, and heat inactivation. The six type I enzymes were associated with R factors from
Shigella
strains; five of these were R(f) factors. The four type II enzymes were associated with R factors from
S. typhimurium
; all these were R(i) factors.
Phenotypic Reversion in Some Early Blocked Sporulation Mutants of
Bacillus subtilis
: Isolation and Phenotype Identification of Partial Revertants
Authors: Guespin-Michel J. F.
Published: January 2020

Single-step mutants of
Bacillus subtilis
blocked at stage zero of sporulation (
spoO
mutants) are pleiotropic. They are impaired in several traits, including increased sensitivity to polymyxin B, when compared to the wild type. Revertants for one or another of the traits associated in this pleiotropy have been isolated and classified according to their phenotypes. Attention was centered on partial revertants (
spoO
still), of which at least three classes could be recognized. Class I partial revertants recovered a high level of resistance to polymyxin and, in a constant order, a variable number of the other traits; some kind of hierarchy is thus revealed to exist among the traits affected in the original pleiotropy. Partial revertants in the other two classes are still hypersensitive to polymyxin. In class II revertants, ability to excrete exoenzymes and antibiotic(s) is recovered to various extents. Only inducibility of nitrate reductase by nitrate is recovered in class III mutants. The possible significance of these observations is discussed.
Growth of
Aerobacter aerogenes
on
d
-Arabinose: Origin of the Enzyme Activities
Authors: Oliver Eugene J. , Mortlock Robert P.
Published: January 2020

Mutants of
Aerobacter aerogenes
can be selected which are capable of utilizing
d
-arabinose as a sole source of carbon and energy for growth. Mutants can also be selected which are capable of using
l
-xylose. The mutational event permitting the utilization of
d
-arabinose results in the constitutive synthesis of certain enzymes of the
l
-fucose catabolic pathway.
l
-Fucose isomerase catalyzes the first reaction in the degradation of
d
-arabinose: the isomerization of
d
-arabinose to
d
-ribulose. No other type of mutation appears to be required to initiate growth on
d
-arabinose, and wild-type cells induced for the enzymes of the
l
-fucose catabolic pathway are capable of growth on
d
-arabinose. The first reaction in the catabolism of
l
-xylose, the isomerization of
l
-xylose to
l
-xylulose, also appears to be catalyzed by constitutively synthesized
l
-fucose isomerase.
Isolation and Fractionation of the Photosynthetic Membranous Organelles fromRhodopseudomonas spheroides
Authors: Fraker Pamela J. , Kaplan Samuel
Published: January 2020

Molecular sieve chromatography and sucrose gradient centrifugation were used to prepare large quantities of purified chromatophores fromRhodopseudomonas spheroides. Electron micrographs of these chromatophores revealed that the final preparations were very homogeneous and free of non-chromatophore particulate material. As an additional check on purity,14C-l-phenylalanine-labeled aerobic cells, devoid of chromatophores, were mixed with unlabeled photosynthetic cells. The resulting preparation contained less than 1% of the radioactivity, originally located in non-chromatophore protein. The purified chromatophores were solubilized in 2-chloroethanol and separated into two fractions. Fraction P1contained 3 to 5% of the total chromatophore protein and could be resolved into 10 electrophoretic components. The second fraction, PII, contained five electrophoretic components. One of these components had associated with it all of the pigment and phospholipid present in PII. Preliminary immunochemical studies on these fractions are also reported.
Fracture Faces in the Cell Envelope of
Escherichia coli
Authors: Gool A. P. Van , Nanninga N.
Published: January 2020

Freeze-fracturing of
Escherichia coli
cells in the presence of 30% (v/v) glycerol resulted in a double cleavage of the cell envelope exposing two convex and two concave fracture faces ([Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text]) with characteristic patterns. Complementary replicas revealed the relationship of the fracture faces to their corresponding fracture planes. The inner fracture plane splits the plasma membrane at one particular level. Apparently the outer fracture plane was located in the outer part of the wall, as it was separated by a layer ([Formula: see text]) from the fractured profile (CW1) presumably corresponding to the murein layer. The outer fracture plane did alternate toward the cell periphery, exposing complementary smooth areas ([Formula: see text] and [Formula: see text]). When cells were freeze-fractured in the absence of glycerol, the outer cell surface appeared as an etching face rather than a fracture face. A schematic representation of the relative location of the different fracture faces in the
E. coli
cell envelope is given.
Microstructure of Colonies of Rod-Shaped Bacteria
Authors: Drucker D. B. , Whittaker D. K.
Published: January 2020

Whole colonies of
Bacillus cereus, B. megaterium, B. mycoides
CN2495,
Corynebacterium hofmanni
NCTC1938,
Escherichia coli, Lactobacillus acidophilus
NCIB1899,
Nocardia graminis
NCTC4728,
Pseudomonas viscosa
, and
Serratia marcescens
were prepared for scanning electron microscopic examination by freeze-drying and metal-coating. The arrangement of individual cells within colonies could be seen. Cells of
Bacillus
colonies tended to be longer than in liquid culture and irregular in shape and to give the appearance of branching.
B. megaterium
colonies frequently had a dense covering film. Colonies of gram-negative bacteria consisted of fairly short rods covered by much adherent extracellular material.
L. acidophilus
had colonies comprised of densely packed, well-oriented rods.
C. hofmanni
colonies contained coccobacilli, packed together. Correlations were observed between plano-convex colony form and densely packed cells, rough colony form and random arrangement of well-separated microorganisms, and irregular colony edge and tendency of cells to grow out from the colony in filaments.
Denitrification with Methanol: a Selective Enrichment for
Hyphomicrobium
Species
Authors: Sperl George T. , Hoare Derek S.
Published: January 2020

Hyphomicrobium
species were enriched in media with methanol as sole carbon source under conditions supporting denitrification. Pure cultures of
Hyphomicrobium
species were isolated which denitrified vigorously with methanol.
Hyphomicrobium
B522, isolated by aerobic enrichment, was adapted to anaerobic growth and denitrification.
Hyphomicrobium
B522 and a new isolate were surveyed for anaerobic growth and denitrification on a number of simple organic compounds. Cell suspensions were tested for denitrifying activity. Nitrogen production from nitrate and nitrite and carbon dioxide production from methanol were stoichiometric.
Relationship Between Sex-Pili Formation and Macarbomycin Sensitivity inEscherichia coli
Authors: Iyobe Shizuko , Mitsuhashi Susumu , Umezawa Hamao
Published: January 2020

The presence inEscherichia colistrains of derepressed sex factors determining F-type pili formation was found to increase their sensitivity to macarbomycin.
Recovery of Exocellular Acid Phosphatase Activity on
Saccharomyces mellis
After Treatment of the Organism with Reagents That Affect the Cell Surface
Authors: Weimberg Ralph
Published: January 2020

Derepressed cells of
Saccharomyces mellis
were treated in one of several different ways to either elute or inactivate the exocellular enzyme, acid phosphatase. The enzyme was either (i) eluted from resting cells with 0.5
m
KCl plus 0.1% β-mercaptoethanol, (ii) eluted from exponential phase cells by growing the organism in derepressing media containing 0.5
m
KCl, or (iii) inactivated on exponential phase cells by adding sufficient acid or base to growth media to destroy the enzyme but not enough to kill the cells. These treatments did not affect viability. Treated cells were transferred to fresh growth media or some other reaction mixture, and the kinetics of recovery of acid phosphatase activity was studied. In these reaction mixtures, enzyme was synthesized only by actively growing cells. Treated resting cells were indistinguishable from untreated, repressed resting cells in that the organism inoculated into complete growth medium remained in the lag phase for approximately 6 hr before both growth and enzyme synthesis began. Exponential phase derepressed cells treated by method (ii) or (iii) were transferred to fresh medium under conditions that allowed growth to continue. The cells immediately started to manufacture enzyme at a rate greater than normal until the steady-state level was reached, thus demonstrating a feedback control system. Exponential phase repressed cells were also transferred to fresh derepressing media under conditions which sustained growth. Though these cells began to grow immediately, there was a lag before acid phosphatase synthesis began followed by a lengthy inductive period. The length of the period of induction could be correlated with the polyphosphate content of the cells. As the supply of polyphosphate neared exhaustion, the rate of synthesis increased rapidly until it was greater than normal; this differential rate was sustained until the steady-state concentration was reached. When derepressed cells grow in a medium containing 0.5
m
KCl, some acid phosphatase activity is found free in the culture fluid and some remains firmly attached to the cells despite the presence of the salt. The bound activity is subject to feedback control, but the steady-state level of this activity on the cells is only one-third that of the acid phosphatase on cells growing in nonsaline media. The extracellular phosphatase is produced at a rate that is several-fold greater than that of the exocellular enzyme in a nonsaline medium. The synthesis of the extracellular enzyme does not seem to be controlled by a feedback mechanism but is produced at a maximal rate as long as the cells are growing.
Role of Autolysins in the Killing of Bacteria by Some Bactericidal Antibiotics
Authors: Rogers H. J. , Forsberg C. W.
Published: January 2020

The rapid lysis of
Bacillus licheniformis
NCTC 6346 and
B. subtilis
168
trp
caused by vancomycin and
d
-cycloserine can be inhibited by stopping protein synthesis. Protein synthesis must be stopped for more than one doubling time of the cells before addition of wall inhibitors. Poorly lytic mutants (lyt
−
) of
B. licheniformis
required 10 to 20 times the concentration of vancomycin or cycloserine to be added to growing cultures to cause even slow lysis. At lower concentrations growth of the mutants is stopped, but the bacteria remain fully viable. Sensitivity of mucopeptide synthesis to vancomycin is the same in both mutants and parent. Sensitivity to the action of
d
-cycloserine is slightly less in the mutant than in the parent.
Genetics of the Mandelate Pathway in
Pseudomonas aeruginosa
Authors: Rosenberg S. L. , Hegeman G. D.
Published: January 2020

The linkage of genes governing synthesis of enzymes functional in the conversion of
l
(+)-mandelate to benzoate in
Pseudomonas aeruginosa
was studied. These genes were found to be linked in a fashion consistent with regulatory mechanisms known to govern synthesis of this inducible pathway. Surprisingly, linkage was also observed between the mandelate genes and those governing the synthesis of functionally related enzymes that participate in the catabolism of anthranilate and benzoate. These latter genes are grouped in at least three regulatory units. Some theoretical explanations for high intensity of linkage among functionally related genes whose expression is not induced by a common metabolite are discussed.
Effects of Mutations and Growth Conditions on Lipid Synthesis in
Neurospora crassa
Authors: Nyc Joseph F. , Brody Stuart
Published: January 2020

A morphological mutant (
col-2
) of
Neurospora
, which is partially deficient in glucose-6-phosphate dehydrogenase (G-6-PD) activity and has lower levels of reduced nicotinamide adenine dinucleotide phosphate (NADPH), accumulated three-fold more triglycerides during log-phase growth than the wild-type strain. Increased lipid deposition was not found in other strains that included slow-growing morphological mutants, NADPH-deficient strains, G-6-PD-deficient mutants, wild-type revertants from
col-2
, and a
cel, col-2
double mutant. The
cel, col-2
strain was supplemented with an exogenous source of fatty acids because it cannot synthesize these lipid moieties. The observed normal lipid content of this strain suggests that the lipid deposition in
col-2
on glucose is due to an overstimulation of fatty acid synthesis and not a deficiency in fatty acid breakdown. The neutral lipid levels in both wild type and
col-2
were decreased to identical levels when grown on glutamate as a carbon source. This effect was not due to changes in glutamic dehydrogenase levels. The omission of citrate from the glutamate medium reduced wild-type neutral lipid levels even further, but had no effect on
col-2
. The variations with time in the neutral lipid levels of
col-2
upon changes in these carbon sources are presented, as well as a discussion of the possible types of regulatory effects unique to the
col-2
mutation which might affect fatty acid synthesis.
Formate Dehydrogenase from
Clostridium acidiurici
Authors: Kearny James J. , Sagers Richard D.
Published: January 2020

Partial purification of formate dehydrogenase from
Clostridium acidiurici
has been accomplished, and some properties of the enzyme have been determined. The molecular weight of the protein is at least 200,000 daltons. The enzyme showed marked instability to freezing and thawing and was inhibited strongly by oxygen and by light. Such inhibition was not reversed by incubation in the presence of thiol compounds. Cyanide inhibited the enzyme 90% at 0.1 m
m
concentrations, but ethylenediaminetetraacetate produced only slight inhibition at concentrations as high as 50 m
m
. The purified enzyme showed no ferredoxin activity in the
Clostridium pasteurianum
clastic system during pyruvate oxidation. Crude preparations of the enzyme could be coupled through ferredoxin to the reduction of nicotinamide adenine dinucleotide during formate oxidation, but the purified enzyme could not catalyze the reduction of pyridine nucleotides by formate in the presence of ferredoxin. Formate oxidation with the purified enzyme was readily coupled to benzyl viologen reduction, in which case ferredoxin was not required. An exchange between formate and bicarbonate was catalyzed by both crude and purified preparations of the enzyme, but the net synthesis of formate from CO
2
was not accomplished.
Fatty Acid Desaturase Mutants of Yeast: Growth Requirements and Electron Spin Resonance Spin-Label Distribution
Authors: Wisnieski Bernadine J. , Kiyomoto Richard K.
Published: January 2020

Two respiratory-sufficient and one respiratory-deficient (nuclear petite) strains of yeast Δ
9
-desaturase mutants were analyzed to determine which fatty acids would serve as replacements for the naturally occurring fatty acids, 16:1 Δ
9
cis
and 18:1 Δ
9
cis
. The requirement can be satisfied by several fatty acids differing in double-bond position, steric configuration, chain length, and degree of unsaturation. The features common to growth-supporting fatty acids are presented and the effects of varying the carbon source and temperature are considered. In addition, we illustrate several pitfalls encountered in membrane studies which exploit lipid-requiring organisms. Since the membrane fatty acid composition of these mutants can be modified readily, electron spin resonance spectroscopy is used to compare membranes of mutant strains enriched for different fatty acids. The lipid distribution pattern of the most commonly employed electron spin resonance spin-label, 12-nitroxide stearate, was ascertained and compared to that of 18:1 Δ
9
cis
.
Deoxyribonucleic Acid Degradation and the Lethal Effect by Myxin in
Escherichia coli
Authors: Behki R. M. , Lesley S. M.
Published: January 2020

Exposure of
Escherichia coli
15T
−
cells to the antibiotic myxin results in the inhibition of deoxyribonucleic acid (DNA) biosynthesis, degradation of intracellular DNA, and death of the cells. Each of these effects was markedly enhanced when protein synthesis was simultaneously inhibited by chloramphenicol. In the continued presence of chloramphenicol, a brief (1 min) exposure to myxin resulted in a rate of DNA degradation and cell death equivalent to that found in the continued presence of myxin alone. Single-strand breaks were present in the DNA of cells exposed to myxin, but when chloramphenicol was also present the breaks were found much earlier. Degradation of DNA in cells exposed to myxin was found to be distributed randomly in both strands and extended over the genome with no restriction to the vicinity of the replication point. There was no release of DNA from its attachment to the cellular membrane in myxin-exposed cells. The possibility that the chloramphenicol effect is due to the inhibition of repair enzyme synthesis which is stimulated by exposure of the cells to myxin is discussed. These data indicate that the extent of the lethal and metabolic damage to the cells by an exposure to myxin represents the result of competition between damage to and repair of cellular DNA.
Positive and Negative Control of R-Factor Replication in
Proteus mirabilis
Authors: Punch J. D. , Kopecko D. J.
Published: January 2020

Replication of the 50 and 58 moles per cent guanine plus cytosine (%GC) components of R factor 222 in
Proteus mirabilis
during growth in the presence and absence of chloramphenicol and after shifting exponential- and stationary-phase cells to conditions which inhibit host protein or deoxyribonucleic acid (DNA) synthesis was examined. Chloramphenicol reduced the growth rate but increased the amount of both R-factor components; the 58% GC component showed a larger proportionate increase. This was inferred to indicate reduced synthesis of an inhibitor that acts on both R-factor components and an initiator for replication of the 50% GC component. Replicative patterns observed after shifting exponential- and stationary-phase cells grown with or without chloramphenicol to minimal medium or chloramphenicol for one generation, or puromycin for 3 hr, corroborated this interpretation. After shifts of exponential cells from either medium, replication of the 50% GC components paralleled host replication, thus indicating a requirement for protein synthesis; replication of the 58% GC component increased due to reduced inhibitor synthesis. R-factor DNA remained constant after shifting stationary cells from drug-free medium, thus indicating that the cells contained effective concentrations of the regulatory inhibitor, whereas increased replication of the 58% GC component occurred after identical shifts of chloramphenicol-grown cells of the same chronological age. Similar responses were observed after shifts to 5 C or to medium containing streptomycin or tetracycline. Absence of replication of the 50% GC component after shifting to medium containing nalidixic acid or phenethanol and its hereditary persistence during growth indicated that the 50% GC replicon was attached to the membrane. Thus, in
P. mirabilis
the three replicons of R factor 222 are regulated as follows: The composite and transfer portion (RTF) replicons represented by the 50% GC component require protein synthesis and membrane attachment and are negatively regulated by an inhibitor; the 58% GC or resistance-determinants replicon exists cytoplasmically and is subject only to negative control.
Method for Isolating Mutants Overproducing Nicotinamide Adenine Dinucleotide and Its Precursors
Authors: Witholt Bernard
Published: January 2020

A procedure has been developed for isolating mutants which are defective with respect to nicotinamide adenine dinucleotide (NAD) metabolism. It is based on the well known V-factor requirement of
Haemophilus parainfluenzae
. This procedure was used to isolate a series of mutants from
Escherichia coli
. The pyridine metabolism of wild-type and mutant
E. coli
cells falls in one of four distinct classes. Class A includes wild-type
E. coli
and represents strains that are normal with respect to pyridine metabolism. Class B mutants have altered internal pools of NAD. The intracellular NAD concentration of different class B mutants varies over a 10-fold range. Class C mutants excrete pyridine mononucleotides, and class D mutants excrete NAD. The production of pyridine nucleotides by class C and D mutants exceeds that of wild-type
E. coli
by a factor of at least ten. The mutant strains generally have normal generation times and achieve normal cell densities in minimal medium.
Deoxyribonucleic Acid Damage by Monofunctional Mitomycins and Its Repair in
Escherichia coli
Authors: Otsuji Nozomu , Murayama Ichiko
Published: January 2020

Exposure of
Escherichia coli
to the antibiotic mitomycin C (MTC) at a concentration of 0.5 μg/ml caused cross-linkage between complementary strands of deoxyribonucleic acid (DNA). Derivatives of mitomycin, 7-methoxymitosene (7-MMT) and decarbamoyl mitomycin C (DCMTC), at a level as high as 20 μg/ml formed no cross-links between DNA strands. Ultraviolet light-sensitive mutants of
E. coli
K-12 bearing
uvrA, uvrB, uvrC
, or
recA
mutations were more sensitive to the lethal action of 7-MMT and of DCMTC than was the wild-type strain. Treatment of wild-type cells with these antibiotics resulted in the production of single-strand breaks in DNA, which were repaired upon incubation in a growth medium. Such breaks in DNA were not produced in the
uvrA
and the
uvrB
mutants. In the
uvrC
mutant, single-strand breaks were produced by 7-MMT or by DCMTC, but these breaks were not repaired upon incubation. These results are discussed in connection with the mechanism for removal of pyrimidine dimers in ultraviolet-irradiated bacteria.
Control of Stable Ribonucleic Acid Chain Initiation in
Escherichia coli
During Diauxie Lag
Authors: Jacobson Lewis A.
Published: January 2020

During glucose-lactose diauxie lag,
Escherichia coli
synthesizes ribonucleic acid (RNA) at about 7% of the rate in exponentially growing cells. RNA synthesis could be restored to the log-phase rate within 3 min after the addition of glucose to the culture (shift-up). This stimulation occurred equally well in the presence of chloramphenicol and therefore did not require the synthesis of new proteins. RNA synthesis could also be stimulated by the addition of glycerol, but only after a delay of 15 to 20 min. Glycerol stimulation occurred more rapidly in cells preadapted by prior growth on glycerol and occurred immediately in a mutant (
glpR
) constitutive for the enzymes of glycerol catabolism. Measurement of a parameter related to the rate of initiation of stable (ribosomal and transfer) RNA chains showed that the initiation of transcription of these stable RNA species was completely inhibited during the diauxie lag, but could be restored to the rate characteristic of log-phase cells by shift-up with glucose. Sucrose gradient analysis of RNA purified from cells after a glucose shift-up indicated an increased rate of accumulation of the ribosomal and transfer RNA species. It is proposed that a specific mechanism to inhibit the initiation of transcription of ribosomal and transfer RNA operates during diauxie lag. This inhibitory mechanism is governed by the level of cellular energy resources insofar as the inhibition is readily reversed by metabolizable energy sources.
Ordering of Mutant Sites in the Isoleucine-Valine Genes of
Escherichia coli
by Use of Merogenotes Derived from F
14
: a New Procedure for Fine-Structure Mapping
Authors: Marsh Nancy J. , Duggan D. E.
Published: January 2020

F-merogenotes derived from F
14
by transductional shortening have previously been found to consist of the sex factor plus one or more of the
ilv
genes. It is shown here that they carry one or more
ilv
genes and a variable portion of the adjacent proximal
ilv
gene. This observation was used to develop a method, analogous to deletion mapping, for ordering mutant sites within the
ilv
genes. This method requires the use of a series of merogenotes each carrying an increasingly longer segment of the gene being mapped. A simplified method of fine-structure mapping is also described which requires only one or two F′ donor strains to map any one gene. This method is based on the large differences observed in recombination frequencies for mutant sites at various distances from the origin of the incomplete merogenote gene. The sequence of 25 mutant sites within three of the
ilv
genes was determined by use of the simplified procedure.
Ferrous Ion-Dependent
l
-Serine Dehydratase from
Clostridium acidiurici
Authors: Carter James E. , Sagers Richard D.
Published: January 2020

l
-Serine dehydratase from
Clostridium acidiurici
was purified 400-fold. The enzyme required activation by catalytic amounts of ferrous ion and a thiol reducing agent before the addition of substrate. Several cations tested were unable to substitute for divalent iron. The reducing agent of choice was dithiothreitol. The activation was presumed to result in the formation of an iron-enzyme complex, because once activated the enzyme retained essentially full activity in a reaction mixture not supplemented with iron or reducing agent. The reaction with substrate was carried out at
p
H 8.4 in phosphate buffer and was specific for
l
-serine. The presence of pyridoxal phosphate as coenzyme was indicated by absorption maxima at 330 and 420 nm and fluorescence maxima at 390 and 520 nm.
Ribosomal Proteins Involved in the Suppression of Streptomycin Dependence in
Escherichia coli
Authors: Kreider Gerald , Brownstein Barbara L.
Published: January 2020

Suppression of streptomycin dependence in
Escherichia coli
strain K-114, a spectinomycin-sensitive strain, is correlated with modification of 30
S
ribosomal protein P4, the component modified in spectinomycin-resistant mutants. The mutant is unusual in that reversion from dependence has previously been correlated only with modification in 30
S
protein P4a. Introduction into K-114 of another mutation conferring spectinomycin resistance results in a further alteration in protein P4.
Localization and Solubilization of the Respiratory Nitrate Reductase of
Bacillus stearothermophilus
Authors: Kiszkiss David F. , Downey R. J.
Published: January 2020

Membranes were isolated from
Bacillus stearothermophilus
2184D by lysozyme digestion of the cell wall and subsequent differential centrifugation. Observations with the electron microscope indicate that such membranes are relatively intact and have a typical membrane appearance. Nitrate will preferentially oxidize the cytochrome
b
of such membranes. Approximately 80% of the total respiratory nitrate reductase activity of whole cells can be localized in the washed membrane fraction and the process of membrane isolation results in a sixfold purification of this enzyme. Of several detergents tested, sodium dodecyl sulfate, Triton 114, and Triton X-100 are most effective in converting reduced methyl viologen-nitrate reductase to a form which will not pellet at 130,000 ×
g
. Density gradient analysis reveals that such detergent-mediated solubilization converts virtually all membrane protein to a form of lighter density.
New Obligate Methylotroph
Authors: Dahl Jean Stokes , Mehta R. J. , Hoare Derek S.
Published: January 2020

A new and unique obligate methylotroph was isolated from enrichment cultures with methanol as the sole source of carbon and energy. The organism grows only on methanol and methylamine and not on methane. It does not have a complex intracellular membrane system.
14
C-acetate was assimilated by growing cultures and cell suspensions but was incorporated into only a limited number of cell constituents.
14
C-acetate incorporation was strictly dependent on the oxidation of methanol or methylamine as a source of energy. Extracts had relatively low levels of enzymes of the tricarboxylic acid cycle, and α-ketoglutarate dehydrogenase was not detected. Comparisons were made with a facultative methylotroph isolated from the same enrichment cultures. The new obligate methylotroph contained hexose phosphate synthetase, a key enzyme in the ribose phosphate cycle of methyl metabolism.
Comparison of Cysteine and Tryptophan Content of Insoluble Proteins Derived from Wild-Type and mi-1 Strains of
Neurospora crassa
Authors: Zollinger Wendell D. , Woodward Dow O.
Published: January 2020

The possibility of an amino acid substitution (cysteine for tryptophan) in a membrane protein of the [mi-1] strain of
Neurospora crassa
has been investigated in detail by using a double radioactive labeling procedure. Auxotrophic strains of
Neurospora
having wild-type [+] or [mi-1] cytoplasm have been grown under conditions which result in the specific labeling of protein tryptophan with
3
H and protein cysteine with
35
S. Although the least soluble 1 to 20% of the [mi-1] mitochondrial membrane protein was usually found to have a higher Cys/Trp ratio (ratio of cysteine plus half-cystine to tryptophan) than the corresponding [+] fraction, it has been shown that these differences were due mainly to the presence of differential amounts of a very insoluble, cysteine-rich (Cys-rich) material. The same Cys-rich material was found in variable amounts in both [+] and [mi-1] cultures, but the concentration was usually higher in the [mi-1] cultures. The Cys-rich material is clearly distinct from “structural protein” on the basis of amino acid composition and appears to have no direct relationship to the [mi-1] phenotype. In the absence of the Cys-rich material, no difference between the Cys/Trp ratios of corresponding [+] and [mi-1] membrane proteins could be detected. We conclude, therefore, that the previously postulated amino acid substitution of cysteine for tryptophan in [mi-1] membrane protein is incorrect.