bluuebunny/crossref_metadata_2025 huggingface dataset:
Screening test for assessment of ultimate biodegradability: linear alkylbenzene sulfonates
Authors: Gledhill W E
Published: December 2020

A relatively simple shake-flask system for determining CO2 evolution was developed to assess the ultimate biodegradability by soil and sewage micro-organisms of chemicals which enter the environment. Linear alkylbenzene sulfonates (LAS) were used as model compounds to evaluate the method and were found to undergo substantial biodegradation in this dilute system. At the 30 mg/liter test concentration, higher-molecular-weight LAS compounds were biodegraded at a slower rate and to a lesser extent than lower-molecular-weight LAS, an effect which was eliminated or greatly reduced upon incremental addition of the LAS to the test medium during the first week of incubation. LA35S was used to demonstrate rapid LAS desulfonation, and 14CO2 evolution studies with (14C) benzene ring-labeled LAS indicated concomitant biodegradation of the entire LAS molecule as well as the LAS aromatic component. The test can be employed to examine numerous compounds at the same time and is readily adapted to studies of the effect of variation in temperature and oxygen concentration on biodegradation.
Chemical alteration of carotene biosynthesis in Phycomyces blakesleeanus and mutants
Authors: Lee T C , Rodriguez D B , Karasawa I , Lee T H , Simpson K L , Chichester C O
Published: December 2020

The effects of diphenylamine, dimethyl sulfoxide, streptomycin, AMO-1618, and beta-ionone on the carotene composition of a wild-type and three mutant strains of Phycomyces blakesleeanus have been examined. Diphenylamine increased the phytoene and phytofluene concentrations of all strains while reducing the levels of the color carotenes. Dimethyl sulfoxide reduced the concentration of both cyclic and acyclic carotenes, whereas AMO-1618 increased the levels of all carotenes in all the strains. The wild type and mutants responded differently to the presence of streptomycin and beta-ionone. The possible mode of action of the above agents on carotenoid biosynthesis is discussed.
Kinetics of a bacterial culture growth: validity of the affinity rule in biological systems
Authors: Marchand A , Dulos E
Published: December 2020

The kinetic study of a process is usually performed by measuring a convenient intensive property, P, as a function of time. The "affinity rule" states that, when a given process takes place under different external constraints (e.g., different temperatures, pressures, pH values, etc.), the various P versus time curves are related by an affinity transformation parallel to the time axis: in other words the P versus log time curves are parallel and can be superimposed by translation. The validity of the rule has been extensively tested in chemical and physiochemical processes, but there is no evidence as yet that it extends to biological systems. The present paper shows that the rule is indeed valid for the kinetics of growth of an Escherichia coli culture at various temperatures and pH values. More extended experiments are necessary to prove or disprove the general validity of the rule in biological systems, but its practical interest is evident: whenever it is valid it will be possible, from a very small number of measurements, to predict the complete behavior of the system in a number of various external conditions
An Improved Method for the Preparation of Sulphur and Iron Containing Differentiation Media
Authors: Rappaport F. , Rabinovitz M. , Konforti N.
Published: December 2020

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Evaluation of Disinfection Techniques for, and Their Effects on, Rectal Thermocouple Catheters
Authors: Maher J. T. , Rogers M. R. , Peterson D. W.
Published: December 2020

The antibacterial activities of an iodophor (Wescodyne G), a quaternary ammonium compound (Roccal), and an iodine tincture as agents for the cold disinfection of rectal catheters contaminated in vitro were determined. Following thorough cleaning with an alcoholic solution of soft soap, each of the three disinfectants tested showed satisfactory results (100% kill) in 5 min against the enteric test bacteria (
Escherichia coli
and
Salmonella typhosa
) as well as a test species of the genus
Pseudomonas
, among the bacteria most resistant to surface-active agents.

An aqueous solution of Wescodyne G containing 75 ppm available iodine was used both as a wiping solution and for subsequent disinfection of rectal catheters contaminated in vivo. Total bacterial destruction was found to follow a 60-min soak preceded by the wiping procedure.

Rectal catheters subjected to prolonged immersion in each of the test disinfectants were found to be essentially unaffected, retaining their initial calibrations within a permissible tolerance. Neither Roccal nor Wescodyne G solutions were found to measurably attack bare thermocouples. Alcoholic iodine 0.5% did, however, exert a deteriorating effect on bare thermocouples in a short time, as measured by change in resistance characteristics.

The results of this study have led to the recommendation that Wescodyne G containing 75 ppm available iodine be used in standing operating procedures for the initial cleaning and subsequent disinfection of rectal thermocouple catheters.
Testing Thermal Death Data for Significant Nonlogarithmic Behavior
Authors: Humphrey Arthur E. , Nickerson John T. R.
Published: December 2020

The thermal death behavior of
Bacillus stearothermophilus
spores in distilled water suspensions is nonlogarithmic in dynamic as well as static tests. The explanation of heat lags as the cause of nonlogarithmic behavior is incorrect.
Studies on Media for Enumerating Enterococci in Frozen Vegetables
Authors: Splittstoesser D. F. , Wright R. , Hucker G. J.
Published: December 2020

A study was made of the relative sensitivity and specificity of presumptive and confirmatory media for the most probable number enumeration of enterococci in frozen vegetables. Azide dextrose broth yielded the highest numbers of confirmable enterococci and its sensitivity was shown to be comparable to nonselective media. The use of ethyl violet azide broth as a confirmatory medium resulted in a significant number of false positive tests. Growth in broth containing 6.5% sodium chloride incubated at 45 C for 2 days was found to be a more specific confirmatory test for enterococci.
Acetaldehyde Formation in Submerged Cultures on Non-film-forming Species of
Saccharomyces
Authors: Ough C. S.
Published: December 2020

Three different yeasts of the species
Saccharomyces cerevisiae
ferment ethyl alcohol to acetaldehyde aerobically and produce “flor” character in a wine medium with submerged culture techniques. Three pounds per square inch gauge (psig) of oxygen instead of 15 psig of air permitted fermentations to proceed, though slightly slower in the series tested, and reaching slightly lower total aldehydes.
Rifomycin
Authors: Margalith P. , Pagani H.
Published: December 2020

The production of a fraction of the rifomycin complex (rifomycin B) by
Streptomyces mediterranei
has been described. Both qualitative and quantitative aspects of the fermentation are determined by suitable agitation-aeration parameters. In addition to conventional nutrient ingredients, the presence of some of the barbituric acid derivatives was found to be essential for rifomycin B production. An attempt was made to explain the mode of action of these compounds.
Effect of Paper on the Performance Assay in the Control of Antibiotic Sensitivity Discs
Authors: Kramer Julian , Kirshbaum Amiel
Published: December 2020

Antibiotic discs were prepared, using several several batches of papers meeting Food and Drug Administration specifications. The analysis of 1,152 zones of inhibition produced showed no performance differences among these batches. Other discs were prepared using papers of different grades. These produced large differences in performance. It is obvious, therefore, that the use of a specified disc paper is necessary for standardizing the performances of the products of various manufacturers and that reproducible results can be attained with the grade of paper specified.
Degeneration of
Streptomyces niveus
with Repeated Transfers
Authors: Reusser F. , Koepsell H. J. , Savage G. M.
Published: December 2020

Novobiocin production by
Streptomyces niveus
decreased drastically as the culture was transferred at regular intervals under both sporulating and nonsporulating conditions. Addition of degenerated live mycelium as second inoculum to shake flask fermentations already inoculated with a high-producing strain resulted in sharply depressed novobiocin formation. Fractionated medium of low-producing strain containing either no cells or dead cells had no adverse effect on the antibiotic yield of the high-producing mycelium. It appears that the low-producing mycelium was outgrowing the high-producing mycelium. A study of the growth rates of the two types of mycelium in a clear broth medium indicated no differences in generation time. However, the low-producing strain proved to have a higher efficiency of carbohydrate utilization, thus overgrowing the high-producing strain. It was speculated that culture instability of
S. niveus
is due to heterocaryosis.
A New Hybrid Strain of an Oxytetracycline-producing Organism,
Streptomyces rimosus
Authors: Mindlin S. Z. , Alikhanian S. I. , Vladimirov A. V. , Mikhailova G. R.
Published: December 2020

A new strain,
Streptomyces rimosus
LS-T hybrid, characterized by a lower level of foaming and higher antibiotic activity as compared to the other active strains of
S. rimosus
, is obtained as a result of selection among prototrophic recombinant forms of strains LS-T293 and BS-21. The studies on strain LS-T hybrid show the possibilities of combining properties of different strains of
S. rimosus
in the hybrid forms. The occurrence of new properties in the hybrid forms is detected.
Continuous Fermentation of Novobiocin
Authors: Reusser F.
Published: December 2020

Continuous fermentation trials with
Streptomyces niveus
in a nine-stage fermentation system (7-liter reaction volume per stage) indicated that the cultures used gradually lost their ability to produce novobiocin when cultured over periods from 10 to 25 days. It was found that mycelial degeneration could be circumvented by operational means during continuous culture using the following technique: Two interchangeable 24-liter stages were installed at the front end of the nine-stage system and connected in parallel with the latter. Alternatingly one of these two tanks was then used as first stage of the continuous fermentation system. The holdup time in the first vessel was adjusted to limit cell growth chiefly to this stage so that most of the antibiotic production took place in subsequent stages. The first stages were switched at approximately weekly intervals. Each of the new tanks was prepared as a batch, inoculated with a high-producing cell population, and allowed to grow for 3 days before it was connected to the remaining system for continuous operation. Using this technique no evidence of culture degeneration was encountered in subsequent novobiocin production stages over a period of 33 days. In conventional runs without periodic replacement of the first stage, culture degeneration with the novobiocin fermentation occurred within a period of 10 to 25 days of continuous operation. This observation indicates that the described technique offers a solution to the problem of maintaining high steady-state titers in continuous novobiocin fermentations. Extension of this technique to other continuous fermentations where culture degeneration is a problem is indicated.
Use of Membrane Filters to Facilitate the Recovery of Virus from Aqueous Suspensions
Authors: Metcalf T. G.
Published: December 2020

Influenza virus was recovered from aqueous suspensions by means of membrane filters. Separation of virus from bacterial mixtures was achieved and virus was recovered free from bacteria. Technics developed for this application of the use of membrane filters were presented. These technics were extended to the successful isolation of Asian influenza virus from clinical specimens made available for use in the study.
The Occurrence of
Gallionella
in Salt Water
Authors: Sharpley J. M.
Published: December 2020

A
Gallionella
sp. is described that lives and freely multiplies in sea water. The habitat of the organism has been thoroughly investigated and the possibility of accidental occurrence has been eliminated. The appearance of the
Gallionella
sp. described is quite different from the similar iron bacteria occurring in fresh water.
Physiological Studies of the Rumen Protozoan
Ophryoscolex caudatus
Eberlein
Authors: Williams P. P. , Davis R. E. , Doetsch R. N. , Gutierrez J.
Published: December 2020

The rumen ciliate
Ophryoscolex caudatus
fermented starch with the production of acetic, butyric, and lactic acids plus CO
2
and H
2
. Cellulose was not significantly metabolized although pectin was rapidly attacked in the Warburg apparatus. The protein sources, cottonseed, soybean, and linseed oil meals, and the amino acids,
dl
-alanine,
dl
-valine, and
dl
-leucine, were utilized by the protozoan, whereas ammonia was demonstrated as an end product of nitrogenous metabolism. Methods for the separation of
O. caudatus
from mixed rumen contents are described.
Pseudomonas creosotenesis
sp. n., a Creosote-tolerant Marine Bacterium
Authors: O'Neill Thomas B. , Drisko Richard W. , Hochman Harry
Published: December 2020

In a study of the marine biological environment in which creosoted pilings are located, a previously unreported species of bacteria was isolated. This species was detected on creosoted piling from 11 widely differing locations and was the predominant species of bacteria found on these piling. The new organism was identified as a gram-negative rod belonging to the genus
Pseudomonas
and has been named
Pseudomonas creosotensis
. It has been completely described by the standard morphological and biochemical tests.
Antimicrobial Activity of Some Higher Amine Salts of Carboxylic Acids
Authors: Borick Paul M. , Bratt Martin
Published: December 2020

Various higher amine salts of dicarboxylic and tricarboxylic acids were prepared and tested for antimicrobial activity in vitro.

Although activity was present in all compounds tested, tetradecylammonium malonate showed the greatest activity with the widest spectrum. This compound was effective against gram-negative as well as gram-positive microorganisms, yeast, and fungi.

A high order of microbiological activity was demonstrated with various higher amine salts of dicarboxylic and tricarboxylic acids, e.g., tetradecylammonium oxalate, tetradecylammonium citrate, and so forth. Compounds tested exhibited a low order of toxicity.
A Bacteriophage-lysing Strain of
Staphylococcus
Employed in the Manufacture of Dry Sausage
Authors: Gyllenberg H. G. , Hackman C. R.
Published: December 2020

A bacteriophage of a certain
Staphylococcus
(a strain of
Staphylococcus lactis
) employed in the manufacture of dry sausage has been characterized. The host range of this bacteriophage is wide. In addition to the original host, 15 other strains (out of 40 strains tested) were found to support reproduction of the phage. The sensitive strains represented
Staphylococcus saprophyticus
and different types of
S. lactis
.

The growth rate of the bacterial host did not influence the rates of phage adsorption, nor the maximal reproduction rate of new particles. With increasing bacterial growth rate, the “lag” observed before phage reproduction started was distinctly decreased. This phase was shorter with the original host strain than with other sensitive strains.

Resistant cultures of the original host strain were easily obtained. These cultures grew as rapidly and gave as good yields of cell mass as the original phage-sensitive host. However, phage resistance was frequently lost.
Isolation of Salmonellae from Foods Samples
Authors: Taylor Welton I. , Silliker John H.
Published: December 2020

A comparison of various methods of enhancing frequency of
Salmonella
isolations revealed that inoculation of a second enrichment broth, with culture from the first, was no improvement over the single direct enrichment method. It was inferior to centrifugation.

Selenite was observed to produce more positive isolations at 48 hr than at 24. No change occurred in tetrathionate. Reconstitution of dried albumen with water produced a significant increase in isolations over direct inoculation of enrichment broth in the case of tetrathionate but not selenite broth.

Pre-enrichment in lactose broth before inoculation of enrichment media was vastly superior to reconstitution in water for both enrichment broths. A comparison of results obtained using dulcitol, mannitol, lactose and carbohydrate-free purple broths in pre-enrichment indicated that the carbohydrate added was immaterial.
Isolation of Salmonellae from Foods Samples
Authors: Taylor Welton I.
Published: December 2020

Comparison of three methods by which salmonellae may be isolated and enumerated from dried albumen, direct inoculation of enrichment media, centrifugation of samples, and pre-enrichment in noninhibitory media, reveals pre-enrichment to be the method of choice.

The superiority of pre-enrichment manifests itself in replicate aliquots of the same sample by producing a statistically significant increase in numbers of isolations of salmonellae and in empirical use with various albumen samples by consistently higher values of most probable numbers (MPN).

The primary factor involved in this superiority appears to be the greater ability of small numbers of salmonellae to initiate growth in the nonselective mannitol purple sugar broth than in the inhibitory enrichment media.

The method of analysis recommended entails inoculation of mannitol broth pre-enrichment medium, transfer of 24-hr culture aliquots to tetrathionate broth, and streaking on brilliant green agar for isolation of salmonellae.
Bacterial Oxidation of Pyritic Materials in Coal
Authors: Silverman Melvin P. , Rogoff Martin H. , Wender Irving
Published: December 2020

Applicability of the manometric method for studying the oxidation of pyritic material in the presence of bacteria has been demonstrated. Resting cells of
Ferrobacillus ferrooxidans
accelerated the oxidation of coal pyrites and coarsely crystalline marcasite, but were inactive on coarsely crystalline pyrite. Resting cells of
Thiobacillus thiooxidans
were inactive on all pyrites tested. Oxidation rates in the presence of
Ferrobacillus
were increased by reducing the particle size of pyritic samples, and, in one case, by removing the CaCO
3
from a calcite-containing sample.
Miso
Authors: Hesseltine C. W. , Shibasaki K.
Published: December 2020

Excellent miso has been prepared with soybean grits inoculated with a pure culture of
Saccharomyces rouxii
strain NRRL Y-2547. Pure culture inoculum of this osmophilic yeast was prepared by growing the culture in aerated flasks on a yeast extract medium with a salt concentration equal to that used in the manufacture of miso. It has also been found possible to make miso from whole beans with the above culture. The advantages of pure culture fermentation in producing miso are discussed.
Role of Bacteria in the Oxidation of Myoglobin
Authors: Robach D. L. , Costilow R. N.
Published: December 2020

The addition to steaks of cell suspensions of a number of aerobic bacteria and of
Saccharomyces cerevisiae
greatly increased the rate of discoloration. Low inocula resulted in the more rapid appearance of the brown color of metmyoglobin, whereas high cell populations quickly produced the purple color of myoglobin. Sonically treated suspensions of
Pseudomonas geniculata
produced similar changes in surface color but less rapidly. No such effect was observed with
Lactobacillus plantarum
.

The visible changes in color were found to be associated with the oxygen demand of the surface tissue including, of course, the demand of any contaminating microorganisms. Inhibitors of respiratory activity inhibited the rate of discoloration under normal atmospheric conditions. However, when the oxygen level in the atmosphere was reduced, the inhibitors had no significant effect. In an oxygen-free atmosphere, the steak surfaces were the purple color of myoglobin; at 10 mm oxygen pressure, the pigment was oxidized to metmyoglobin and the surface was brown in color. No bacterial activity was necessary for pigment oxidation under low oxygen pressures.

Addition of dilute solutions of glucose oxidase resulted in rapid oxidation of the meat pigment to metmyoglobin both in extracts and on steak surfaces. More concentrated solutions resulted in further oxidation as evidenced by the appearance of a green color. Horseradish extract with a high peroxidase activity added with H
2
O
2
resulted in rapid oxidation of the pigment but neither were very effective alone, although H
2
O
2
did result in a browning reaction in aged steaks.

It is concluded that the primary role of the bacteria in meat discoloration is in the reduction of the oxygen tension in the surface tissue. The implications of the data are discussed and a possible mechanism of myoglobin oxidation is proposed.
Factors Affecting the Activity of Phenolic Disinfectants
Authors: Ortenzio L. F. , Opalsky C. D. , Stuart L. S.
Published: December 2020

Low challenge phenol coefficient and high challenge use-dilution tests were made on a neutral cocoanut oil soap emulsion of
o
-phenylphenol and aqueous solutions of sodium
o
-phenylphenate prepared in the laboratory from the phenol using a stoichiometric amount of NaOH as well as with increasing amounts of excess NaOH. The phenol had considerably greater activity in both test methods when emulsified with the neutral soap than when converted to the phenate and dissolved in water. Use dilution test results against
Salmonella choleraesuis
with both the phenol and the phenate were within the range which would have been predicted from the
Salmonella typhosa
coefficient results employing the conventional conversion multiple of 20 to determine the maximal number of parts of water to which one part of germicide could be added. With the emulsified phenol this was also true where
Staphylococcus aureus
was employed in both procedures. With the aqueous solution of the phenate the maximal safe use-dilution by the phenol coefficient found for
S. aureus
and the same conventional conversion procedure was roughly five times higher than the maximal safe use-dilution found by the use-dilution method. Results with aqueous solutions of the phenate to which increasing amounts of excess NaOH were added showed no significant differences in the phenol coefficient method with either
S. typhosa
or
S. aureus
. In the use-dilution method, significant decreases in activity were found as the excess NaOH was increased to 4% with both
S. choleraesuis
and
S. aureus
. Although the pH values of aqueous solutions of the phenate were raised as the amount of free NaOH was increased, the decreases in pH observed as the dilution with water was increased were such that only small differences existed at the high critical killing dilutions found in the low challenge phenol coefficient method, whereas rather large differences existed at the lower critical killing dilutions in the high challenge use-dilution method.
Detection of Air-borne
Pasteurella tularensis
Using the Fluorescent Antibody Technique
Authors: Jaeger Robert F. , Spertzel Richard O. , Kuehne Ralph W.
Published: December 2020

Considerable research has been directed toward the development of rapid methods for the identification of air-borne microorganisms. The application of the fluorescent antibody technique (FAT) coupled with the impaction of contaminated air onto glass slides affords a rapid and specific method for the identification of air-borne
Pasteurella tularensis
. Early experiments presented problems of cross-reaction with organisms other than
P. tularensis
. These cross-reactions are eliminated by specific adsorption and proper dilution of the conjugate. A series of experiments conducted under rigidly controlled laboratory conditions indicates that fewer than ten viable
P. tularensis
per slide can be detected by this method. Time of impaction as well as the presence of large concentrations of other microorganisms did not alter this number. Calculations indicate that a concentration as low as one viable organism per 5 liters of air can be detected.
The Identification and Separation of
Aeromonas liquefaciens
from
Pseudomonas fluorescens
and Related Organisms Occurring in Diseased Fish
Authors: Bullock Graham L.
Published: December 2020

Taxonomy of the motile species of the genus
Aeromonas
is briefly discussed. It is suggested that
Aeromonas
organisms, isolated from outbreaks of red mouth of trout, red sore of pike, infectious abdominal dropsy and hemorrhagic septicemia of warm water fish, and which show acid and gas in glucose broth, production of 2,3-butanediol hydrogen sulfide from motility sulfide medium, presence of cytochrome oxidase, and hydrolysis of starch, be designated as
Aeromonas liquefaciens
. These tests also serve to differentiate
A. liquefaciens
from fish-pathogenic
Pseudomonas fluorescens
and from enteric bacteria.
Physiological and genetic responses of bacteria to osmotic stress
Authors: Csonka L N
Published: December 2020

The capacity of organisms to respond to fluctuations in their osmotic environments is an important physiological process that determines their abilities to thrive in a variety of habitats. The primary response of bacteria to exposure to a high osmotic environment is the accumulation of certain solutes, K+, glutamate, trehalose, proline, and glycinebetaine, at concentrations that are proportional to the osmolarity of the medium. The supposed function of these solutes is to maintain the osmolarity of the cytoplasm at a value greater than the osmolarity of the medium and thus provide turgor pressure within the cells. Accumulation of these metabolites is accomplished by de novo synthesis or by uptake from the medium. Production of proteins that mediate accumulation or uptake of these metabolites is under osmotic control. This review is an account of the processes that mediate adaptation of bacteria to changes in their osmotic environment.
R-body-producing bacteria
Authors: Pond F R , Gibson I , Lalucat J , Quackenbush R L
Published: December 2020

Until 10 years ago, R bodies were known only as diagnostic features by which endosymbionts of paramecia were identified as kappa particles. They were thought to be limited to the cytoplasm of two species in the Paramecium aurelia species complex. Now, R bodies have been found in free-living bacteria and other Paramecium species. The organisms now known to form R bodies include the cytoplasmic kappa endosymbionts of P. biaurelia and P. tetraurelia, the macronuclear kappa endosymbionts of P. caudatum, Pseudomonas avenae (a free-living plant pathogen), Pseudomonas taeniospiralis (a hydrogen-oxidizing soil microorganism), Rhodospirillum centenum (a photosynthetic bacterium), and a soil bacterium, EPS-5028, which is probably a pseudomonad. R bodies themselves fall into five distinct groups, distinguished by size, the morphology of the R-body ribbons, and the unrolling behavior of wound R bodies. In recent years, the inherent difficulties in studying the organization and assembly of R bodies by the obligate endosymbiont kappa, have been alleviated by cloning and expressing genetic determinants for these R bodies (type 51) in Escherichia coli. Type 51 R-body synthesis requires three low-molecular-mass polypeptides. One of these is modified posttranslationally, giving rise to 12 polypeptide species, which are the major structural subunits of the R body. R bodies are encoded in kappa species by extrachromosomal elements. Type 51 R bodies, produced in Caedibacter taeniospiralis, are encoded by a plasmid, whereas bacteriophage genomes probably control R-body synthesis in other kappa species. However, there is no evidence that either bacteriophages or plasmids are present in P. avenae or P. taeniospiralis. No sequence homology was detected between type 51 R-body-encoding DNA and DNA from any R-body-producing species, except C. varicaedens 1038. The evolutionary relatedness of different types of R bodies remains unknown.
Physiology, biochemistry, and specific inhibitors of CH4, NH4+, and CO oxidation by methanotrophs and nitrifiers
Authors: Bédard C , Knowles R
Published: December 2020

Ammonia oxidizers (family Nitrobacteraceae) and methanotrophs (family Methylococcaceae) oxidize CO and CH4 to CO2 and NH4+ to NO2-. However, the relative contributions of the two groups of organisms to the metabolism of CO, CH4, and NH4+ in various environments are not known. In the ammonia oxidizers, ammonia monooxygenase, the enzyme responsible for the conversion of NH4+ to NH2OH, also catalyzes the oxidation of CH4 to CH3OH. Ammonia monooxygenase also mediates the transformation of CH3OH to CO2 and cell carbon, but the pathway by which this is done is not known. At least one species of ammonia oxidizer, Nitrosococcus oceanus, exhibits a Km for CH4 oxidation similar to that of methanotrophs. However, the highest rate of CH4 oxidation recorded in an ammonia oxidizer is still five times lower than rates in methanotrophs, and ammonia oxidizers are apparently unable to grow on CH4. Methanotrophs oxidize NH4+ to NH2OH via methane monooxygenase and NH4+ to NH2OH via methane monooxygenase and NH2OH to NO2- via an NH2OH oxidase which may resemble the enzyme found in ammonia oxidizers. Maximum rates of NH4+ oxidation are considerably lower than in ammonia oxidizers, and the affinity for NH4+ is generally lower than in ammonia oxidizers. NH4+ does not apparently support growth in methanotrophs. Both ammonia monooxygenase and methane monooxygenase oxidize CO to CO2, but CO cannot support growth in either ammonia oxidizers or methanotrophs. These organisms have affinities for CO which are comparable to those for their growth substrates and often higher than those in carboxydobacteria. The methane monooxygenases of methanotrophs exist in two forms: a soluble form and a particulate form. The soluble form is well characterized and appears unrelated to the particulate. Ammonia monooxygenase and the particulate methane monooxygenase share a number of similarities. Both enzymes contain copper and are membrane bound. They oxidize a variety of inorganic and organic compounds, and their inhibitor profiles are similar. Inhibitors thought to be specific to ammonia oxidizers have been used in environmental studies of nitrification. However, almost all of the numerous compounds found to inhibit ammonia oxidizers also inhibit methanotrophs, and most of the inhibitors act upon the monooxygenases. Many probably exert their effect by chelating copper, which is essential to the proper functioning of some monooxygenases. The lack of inhibitors specific for one or the other of the two groups of bacteria hampers the determination of their relative roles in nature.
Microbial ureases: significance, regulation, and molecular characterization
Authors: Mobley H L , Hausinger R P
Published: December 2020

Microbial ureases hydrolyze urea to ammonia and carbon dioxide. Urease activity of an infectious microorganism can contribute to the development of urinary stones, pyelonephritis, gastric ulceration, and other diseases. In contrast to these harmful effects, urease activity of ruminal and gastrointestinal microorganisms can benefit both the microbe and host by recycling (thereby conserving) urea nitrogen. Microbial ureases also play an important role in utilization of environmental nitrogenous compounds and urea-based fertilizers. Urease is a high-molecular-weight, multimeric, nickel-containing enzyme. Its cytoplasmic location requires that urea enter the cell for utilization, and in some species energy-dependent urea uptake systems have been detected. Eucaryotic microorganisms possess a homopolymeric urease, analogous to the well-studied plant enzyme composed of six identical subunits. Gram-positive bacteria may also possess homopolymeric ureases, but the evidence for this is not conclusive. In contrast, ureases from gram-negative bacteria studied thus far clearly possess three distinct subunits with Mrs of 65,000 to 73,000 (alpha), 10,000 to 12,000 (beta), and 8,000 to 10,000 (gamma). Tightly bound nickel is present in all ureases and appears to participate in catalysis. Urease genes have been cloned from several species, and nickel-containing recombinant ureases have been characterized. Three structural genes are transcribed on a single messenger ribonucleic acid and translated in the order gamma, beta, and then alpha. In addition to these genes, several other peptides are encoded in the urease operon of some species. The roles for these other genes are not firmly established, but may involve regulation, urea transport, nickel transport, or nickel processing.
Biology of Haemophilus ducreyi
Authors: Albritton W L
Published: December 2020

The etiological agent of the sexually transmitted genital ulcer disease chancroid was first described in 1889 by Auguste Ducrey following repeated autoinoculation of purulent ulcer material from a series of patients. The organism was isolated on artificial media a decade later but has remained difficult to isolate consistently, resulting in controversy over its characteristics and role as the causative agent of chancroid. Because of its fastidious growth requirements, including unknown components in blood, the organism was included in the original description of the genus Haemophilus. Requirement for exogenous hemin and limited phenotypic characteristics, including structural and antigenic properties, suggested that Haemophilus ducreyi was a valid member of the genus Haemophilus. Recent studies of respiratory quinones, deoxyribonucleic acid hybridization, and competition for homologous transformation of the type species, H. influenzae, suggest that H. ducreyi is unrelated to any of the present species of the family Pasteurellaceae, which includes members of the genera Haemophilus, Actinobacillus, and Pasteurella. This review summarizes the early studies with H. ducreyi and our current knowledge of the microbiology of this important human pathogen.
Pathogenesis and immunity in murine salmonellosis
Authors: Hsu H S
Published: December 2020

Salmonella is traditionally described as a facultative intracellular parasite, and host macrophages are regarded as the primary effector cells in both native and acquired immunity in mouse typhoid. This concept has not been unanimously accepted in the literature. Based on cell culture experiments and electron microscopic examinations of infected tissues, we observed that virulent Salmonella typhimurium is killed within polymorphs and macrophages of guinea pigs and mice. In a systemic disease, the organism propagates primarily in the extracellular locations of sinusoids and tissue lesions and within hepatocytes. Hence, it is more likely to be an extracellular pathogen and its virulence is directly related to its antiphagocytic property. The conspicuous absence of macrophages in the primary lesions of murine salmonellosis disputes the likelihood of their significant role in native resistance to the disease. Acquired cellular immunity is expressed as an enhanced antibacterial activity of macrophages facilitated by cytophilic antibodies rather than as an altered antibacterial action of immune macrophages. It is proposed that acquired immunity in murine salmonellosis is a synergistic manifestation of the innate capacity of polymorphs and macrophages to destroy ingested salmonellae, the activated antibacterial functions of macrophages mediated by cytophilic antibodies, the opsonic and agglutinating actions of antiserum, and the accelerated inflammation associated with delayed hypersensitivity to bacterial antigens. Unlike live attenuated vaccines, nonviable vaccines offer a significant, though not a solid, protection against subsequent challenges.
Rotavirus gene structure and function
Authors: Estes M K , Cohen J
Published: December 2020

Knowledge of the structure and function of the genes and proteins of the rotaviruses has expanded rapidly. Information obtained in the last 5 years has revealed unexpected and unique molecular properties of rotavirus proteins of general interest to virologists, biochemists, and cell biologists. Rotaviruses share some features of replication with reoviruses, yet antigenic and molecular properties of the outer capsid proteins, VP4 (a protein whose cleavage is required for infectivity, possibly by mediating fusion with the cell membrane) and VP7 (a glycoprotein), show more similarities with those of other viruses such as the orthomyxoviruses, paramyxoviruses, and alphaviruses. Rotavirus morphogenesis is a unique process, during which immature subviral particles bud through the membrane of the endoplasmic reticulum (ER). During this process, transiently enveloped particles form, the outer capsid proteins are assembled onto particles, and mature particles accumulate in the lumen of the ER. Two ER-specific viral glycoproteins are involved in virus maturation, and these glycoproteins have been shown to be useful models for studying protein targeting and retention in the ER and for studying mechanisms of virus budding. New ideas and approaches to understanding how each gene functions to replicate and assemble the segmented viral genome have emerged from knowledge of the primary structure of rotavirus genes and their proteins and from knowledge of the properties of domains on individual proteins. Localization of type-specific and cross-reactive neutralizing epitopes on the outer capsid proteins is becoming increasingly useful in dissecting the protective immune response, including evaluation of vaccine trials, with the practical possibility of enhancing the production of new, more effective vaccines. Finally, future analyses with recently characterized immunologic and gene probes and new animal models can be expected to provide a basic understanding of what regulates the primary interactions of these viruses with the gastrointestinal tract and the subsequent responses of infected hosts.
Protein phosphorylation and regulation of adaptive responses in bacteria
Authors: Stock J B , Ninfa A J , Stock A M
Published: December 2020

Bacteria continuously adapt to changes in their environment. Responses are largely controlled by signal transduction systems that contain two central enzymatic components, a protein kinase that uses adenosine triphosphate to phosphorylate itself at a histidine residue and a response regulator that accepts phosphoryl groups from the kinase. This conserved phosphotransfer chemistry is found in a wide range of bacterial species and operates in diverse systems to provide different regulatory outputs. The histidine kinases are frequently membrane receptor proteins that respond to environmental signals and phosphorylate response regulators that control transcription. Four specific regulatory systems are discussed in detail: chemotaxis in response to attractant and repellent stimuli (Che), regulation of gene expression in response to nitrogen deprivation (Ntr), control of the expression of enzymes and transport systems that assimilate phosphorus (Pho), and regulation of outer membrane porin expression in response to osmolarity and other culture conditions (Omp). Several additional systems are also examined, including systems that control complex developmental processes such as sporulation and fruiting-body formation, systems required for virulent infections of plant or animal host tissues, and systems that regulate transport and metabolism. Finally, an attempt is made to understand how cross-talk between parallel phosphotransfer pathways can provide a global regulatory curcuitry.
Genetics and molecular biology of siderophore-mediated iron transport in bacteria
Authors: Crosa J H
Published: December 2020

The possession of specialized iron transport systems may be crucial for bacteria to override the iron limitation imposed by the host or the environment. One of the most commonly found strategies evolved by microorganisms is the production of siderophores, low-molecular-weight iron chelators that have very high constants of association for their complexes with iron. Thus, siderophores act as extracellular solubilizing agents for iron from minerals or organic compounds, such as transferrin and lactoferrin in the host vertebrate, under conditions of iron limitation. Transport of iron into the cell cytosol is mediated by specific membrane receptor and transport systems which recognize the iron-siderophore complexes. In this review I have analyzed in detail three siderophore-mediated iron uptake systems: the plasmid-encoded anguibactin system of Vibrio anguillarum, the aerobactin-mediated iron assimilation system present in the pColV-K30 plasmid and in the chromosomes of many enteric bacteria, and the chromosomally encoded enterobactin iron uptake system, found in Escherichia coli, Shigella spp., Salmonella spp., and other members of the family Enterobacteriaceae. The siderophore systems encoded by Pseudomonas aeruginosa, namely, pyochelin and pyoverdin, as well as the siderophore amonabactin, specified by Aeromonas hydrophila, are also discussed. The potential role of siderophore-mediated systems as virulence determinants in the specific host-bacteria interaction leading to disease is also analyzed with respect to the influence of these systems in the expression of other factors, such as toxins, in the bacterial virulence repertoire.
Invertrons, a class of structurally and functionally related genetic elements that includes linear DNA plasmids, transposable elements, and genomes of adeno-type viruses
Authors: Sakaguchi K
Published: December 2020

Invertrons are genetic elements composed of DNA with inverted terminal repeats at both ends, covalently bonded to terminal proteins involved in the initiation of DNA replication at both their 5' termini when they exist in the cytoplasm of their host in free form. They function as viruses, linear DNA plasmids, transposable elements, and sometimes combinations of two of these properties. They differ from retroviruses and related retro-type transposons which have direct repeats on both their genomic ends and exploit RNA intermediates for replication of their DNA. A model for replication and integration of invertrons is presented, as well as a model for transposition of transposable elements.
Influence of interfaces on microbial activity
Authors: van Loosdrecht M C , Lyklema J , Norde W , Zehnder A J
Published: December 2020

Bacterial adhesion in natural and artificial systems has been critically reviewed to investigate the influences exerted by the presence of interfaces. Numerous investigations have demonstrated that, in the presence of a solid phase, the activity of bacterial cultures is changed. Reviewing relevant literature, two problems were encountered. One is of an experimental nature. Due to lack of similarity in experimental conditions, disparate experiments often cannot be compared; their results may even appear conflicting. The other problem is of an interpretational nature: several hypothetical theories exist which try to explain the effect of surfaces on microbial activity. These theories often confuse changes in the medium and limitations in mass transfer which are due to the presence of solid surfaces (indirect influences) with changes in cell properties (direct influences). Whenever a surface is reported to influence the metabolism of bacteria, the action is found almost exclusively to be due to changes in the medium or environment and is therefore indirect. Based on data reported in the literature, and by using thermodynamic and kinetic considerations, it is concluded that so far neither experimental nor theoretical evidence exists for a direct influence of interfaces on microbial activity.
Linkage map of Escherichia coli K-12, edition 8
Authors: Bachmann B J
Published: December 2020

The linkage map of Escherichia coli K-12 depicts the arrangement of genes on the circular chromosome of this organism. The basic units of the map are minutes, determined by the time-of-entry of markers from Hfr into F- strains in interrupted-conjugation experiments. The time-of-entry distances have been refined over the years by determination of the frequency of cotransduction of loci in transduction experiments utilizing bacteriophage P1, which transduces segments of DNA approximately 2 min in length. In recent years, the relative positions of many genes have been determined even more precisely by physical techniques, including the mapping of restriction fragments and the sequencing of many small regions of the chromosome. On the whole, the agreement between results obtained by genetic and physical methods has been remarkably good considering the different levels of accuracy to be expected of the methods used. There are now few regions of the map whose length is still in some doubt. In some regions, genetic experiments utilizing different mutant strains give different map distances. In other regions, the genetic markers available have not been close enough to give accurate cotransduction data. The chromosome is now known to contain several inserted elements apparently derived from lambdoid phages and other sources. The nature of the region in which the termination of replication of the chromosome occurs is now known to be much more complex than the picture given in the previous map. The present map is based upon the published literature through June of 1988. There are now 1,403 loci placed on the linkage group, which may represent between one-third and one-half of the genes in this organism.
Codon preferences in free-living microorganisms
Authors: Andersson S G , Kurland C G
Published: December 2020

A popular interpretation of the major codon preference is that it reflects the operation of a regulatory device that controls the expression of individual proteins. In this popular model, rapidly translated codons are thought to promote the accumulation of the highly expressed proteins and slowly translated codons are thought to retard the expression of poorly expressed proteins. However, this widely accepted model is not supported by kinetic theory or by experimental results. A less fashionable model in which the major codon preference has nothing to do with the expression level of the individual proteins is forwarded. In this model, the major codon preference is viewed as a global strategy to support the efficient function of the translation system and thereby to maximize the growth rates of cells under favorable conditions.
Animal cytomegaloviruses
Authors: Staczek J
Published: December 2020

Cytomegaloviruses are agents that infect a variety of animals. Human cytomegalovirus is associated with infections that may be inapparent or may result in severe body malformation. More recently, human cytomegalovirus infections have been recognized as causing severe complications in immunosuppressed individuals. In other animals, cytomegaloviruses are often associated with infections having relatively mild sequelae. Many of these sequelae parallel symptoms associated with human cytomegalovirus infections. Recent advances in biotechnology have permitted the study of many of the animal cytomegaloviruses in vitro. Consequently, animal cytomegaloviruses can be used as model systems for studying the pathogenesis, immunobiology, and molecular biology of cytomegalovirus-host and cytomegalovirus-cell interactions.