bluuebunny/crossref_metadata_2025 huggingface dataset:
Nephrotoxicity of Dietary Ochratoxin A in Broiler Chikens
Authors: Huff W. E. , Wyatt R. D. , Hamilton P. B.
Published: December 2020

Graded doses of pure ochratoxin A (0, 0.5, 1.0, 2.0, 4.0, and 8.0 μg of toxin per g of feed) were incorporated into a commercial diet which was fed to chicks from 1 day to 3 weeks of age, at which time the experiments were terminated. Growth was inhibited at 2.0, 4.0, and 8.0 μg/g, whereas the kidneys were enlarged at doses of 1.0 μg/g and above. Renal function as measured by clearance of phenol red was decreased 15 and 31% by doses of 4.0 and 8.0 μg/g, respectively. Uric acid was increased 38 and 48% over the control values by doses of 4.0 and 8.0 μg/g, respectively. The plasma electrolytes Na, Cl, Ca, and K were measured; however, only K was significantly (P < 0.05) altered, showing a decrease at doses of 4.0 and 8.0 μg/g. The percentage dry weight of the kidneys decreased significantly at dose levels of 4.0 and 8.0 μg/g, indicative of edema. Histological examination of kidney sections gave the impression of edema and some tubular necrosis. Pathological changes were observed at all dose levels. These data demonstrate that ochratoxin A is a severe nephrotoxin in young broiler chickens.
Degradation of Petroleum by an Alga,
Prototheca Zopfii
Authors: Walker J. D. , Colwell R. R. , Petrakis L.
Published: December 2020

Prototheca zopfii
is an achlorophyllous alga which degrades oil. It has been found to degrade 10 and 40% of a motor oil and crude oil, respectively, when tested under appropriate conditions. Degradation of the crude oil observed in this study compares well with the amount of degradation accomplished by bacteria.
P. zopfii
was found to degrade a greater percentage of the aromatic hydrocarbons in motor oil than of the saturated hydrocarbons and a greater percentage of saturated hydrocarbons in crude oil than of aromatic hydrocarbons. Resins and asphaltenes were produced during degradation of motor oil, whereas these fractions in crude oil were degraded.
P. zopfii
did not demonstrate preferential utilization of lower homologues of cycloalkanes and aromatics as has been observed with bacteria.
Survival of Frozen Mycoplasmas
Authors: Raccach Moshe , Rottem Shlomo , Razin Shmuel
Published: December 2020

Cooling to -70 C killed a higher percentage of
Acholeplasma laidlawii
and
Mycoplasma mycoides
var.
capri
cells than cooling to -20 C. However, to preserve cell viability for prolonged periods storage at -70 C was much more preferable. The percentage of cells surviving freezing could be increased by increasing the initial cell concentration or by the addition of dimethyl sulfoxide or glycerol as cryoprotective agents. In the presence of 1.5 M of any one of these agents survival rates of up to 100% could be obtained. The optimal cooling rates for maximal survival of
A. laidlawii
under the experimental conditions tested were 11 C/min for cooling to -20 C and about 15 C/min for cooling to -70 C. Increasing the warming rate during thawing from 0.6 to 67 C/min increased survival by 3 log. Oleic acid enrichment of
A. laidlawii
membrane lipids, or reduction in the cholesterol content of
M. mycoides
var.
capri
membranes, increased the percentage of organisms surviving freezing. Hence, the composition of membrane lipids appears to have a marked influence on the susceptibility of mycoplasmas to freezing injury.
Antibodies Against Enteric Bacteria in Brown Bullhead Catfish (
Ictalurus nebulosus
, LeSueur) Inhabiting Contaminated Waters
Authors: Troast Judith L.
Published: December 2020

Brown bullhead catfish were collected from sewage- and acid mine waste-polluted waters in an attempt to detect antibodies against human enteric bacteria in their sera and to investigate the association of antibody response with environmental conditions. Agglutination antigens prepared from isolates obtained from water collected at the same locations as the fish habitats were used to demonstrate such antibodies. The results showed large percentages of reactive sera for common isolates such as
Escherichia coli
and
Enterobacter cloacae
as well as lesser incidences of antibodies to other, less common isolates. In general, fish with the highest titers were collected from habitats with higher coliform counts. Acid mine drainage reduced the total coliform counts, but did not appear to affect the titers of sera from fish collected from water so affected. It was concluded that the bottom-feeding catfish might be a better subject for the study of fish as an ecological indicator of fecal pollution in acid-polluted waters.
Characterization of Radiation-Resistant Vegetative Bacteria in Beef
Authors: Welch Ardyce B. , Maxcy R. B.
Published: December 2020

Ground beef contains numerous microorganisms of various types. The commonly recognized bacteria are associated with current problems of spoilage. Irradiation, however, contributes a new factor through selective destruction of the microflora. The residual microorganisms surviving a nonsterilizing dose are predominantly gram-negative coccobacilli. Various classifications have been given, e.g.,
Moraxella, Acinetobacter, Achromobacter
, etc. For a more detailed study of these radiation-resistant bacteria occurring in ground beef, an enrichment procedure was used for isolation. By means of morphological and biochemical tests, most of the isolates were found to be
Moraxella
, based on current classifications. The range of growth temperatures was from 2 to 50 C. These bacteria were relatively heat sensitive, e.g., D
10
of 5.4 min at 70 C or less. The radiation resistance ranged from D
10
values of 273 to 2,039 krad. Thus, some were more resistant than any presently recognized spores. A reference culture of
Moraxella osloensis
was irradiated under conditions comparable to the enrichment procedure used with the ground beef. The only apparent changes were in morphology and penicillin sensitivity. However, after a few subcultures these bacteria reverted to the characteristics of the parent strain. Thus, it is apparent that these isolates are a part of the normal flora of ground beef and not aberrant forms arising from the irradiation procedure. The significance, if any, of these bacteria is not presently recognized.
Incidence of
Vibrio parahaemolyticus
in Chesapeake Bay
Authors: Kaneko Tatsuo , Colwell R. R.
Published: December 2020

A Bay-wide survey of the distribution of
Vibrio parahaemolyticus
was carried out in Chesapeake Bay during May 1972, to determine whether the annual cycle of
V. parahaemolyticus
which was observed to occur in the Rhode River subestuary of Chesapeake Bay took place in other parts of Chesapeake Bay. In an earlier study, April to early June, when the water temperature rises from 14 to 19 C, was found to be a critical period in the annual cycle of the organism in the Rhode River, since this is the time period when the annual cycle is initiated. Results of this study, however, revealed that
V. parahaemolyticus
could not be found in the water column during May 1972. Neverthless, several samples of sediment and plankton yielded
V. parahaemolyticus
isolates. Comparison of data with those for the Rhode River area examined in the earlier studies of the annual cycle of
V. parahaemolyticus
suggests that the time of initiation of the annual cycle of
V. parahaemolyticus
in the open Bay proper may be influenced by various factors such as temperature and salinity, i.e., deeper water locations may show initiation of the
V. parahaemolyticus
annual cycle later than shallow areas. Confirmation of the presence of the organism in the samples studied was accomplished using numerical taxonomy with 19 reference strains also included in the analyses.
Principal Component Analysis of Infraspecific Bacteria
Authors: Darland Gary
Published: December 2020

In certain types of ecological investigations it may be desirable to investigate infraspecific variation in bacteria. Principal component analysis is demonstrated to be satisfactory for this purpose. Hypothetical bacterial populations were used to show that such analysis can be used to compare collections of bacterial isolates taken at different times or from different sources. Alternatively, given
n
isolates, whether they represent a single bacterial population can be determined. The method is applied to authentic collections of bacteria in three separate analyses. The results are compatible with current taxonomic tenets.
Automatic pH Control and Soluble and Insoluble Substrate Input for Continuous Culture of Rumen Microorganisms
Authors: Slyter Leonard L.
Published: December 2020

An artifical rumen continuous culture with pH control, automated input of water-soluble and water-insoluble substrates, controlled mixing of contents, and a collection system for gas is described.
Effects of a Commercial Malathion Preparation on Selected Soil Bacteria
Authors: Stanlake G. J. , Clark J. B.
Published: December 2020

The aromatic petroleum distillates present in a commercial preparation of malathion insecticide had a greater effect on viability of pure cultures of soil bacteria than did the malathion, whereas neither component had an effect on the population of the natural soil community.
Fermentative Accumulation of Guanosine Polyphosphate by
Brevibacterium ammoniagenes
Authors: Furuya Akira , Sato Akira
Published: December 2020

Guanosine-3′-diphosphate-5′-monophosphate (3.35 mg/ml), guanosine-3′-diphosphate-5′-diphosphate (MSI) (5.21 mg/ml), and guanosine-3′-diphosphate-5′ triphosphate (MSII) (0.82 mg/ml), in addition to guanosine 5′-monophosphate, guanosine 5′-diphosphate, and guanosine 5′-triphosphate, were accumulated by microbial conversion of 5′-xanthylic acid with a mutant of
Brevibacterium ammoniagenes
.
Automated Single-Slide Staining Device
Authors: Wilkins Judd R. , Mills Stacey M.
Published: December 2020

An automated single-slide staining device is described. Smears gram stained by the automatic device were equal in quality to the manual method.
Isolation of Acetyl T-2 Toxin from
Fusarium poae
Authors: Kotsonis Frank N. , Ellison Robert A. , Smalley Eugene B.
Published: December 2020

Acetyl T-2 toxin (3,4,15-triacetoxy-8-isovaleroxy-12,13-epoxy-Δ
9
-trichothecene) was isolated and characterized as a naturally occurring emetic trichothecene from liquid cultures of
Fusarium poae
(NRRL 3287). Acetyl T-2 toxin was shown to be much less toxic than T-2 toxin in pigeon assays.
Survival of
Aspergillus flavus
and
Fusarium moniliforme
in High-Moisture Corn Stored Under Modified Atmospheres
Authors: Wilson David M. , Huang L. H. , Jay Edward
Published: December 2020

Freshly harvested high-moisture corn with 29.4% moisture and corn remoistened to 19.6% moisture were inoculated with
Aspergillus flavus
Link ex Fr. and stored for 4 weeks at about 27 C in air (0.03% CO
2
, 21% O
2
, and 78% N
2
) and three modified atmospheres: (i) 99.7% N
2
and 0.3% O
2
; (ii) 61.7% CO
2
, 8.7% O
2
, and 29.6% N
2
; and (iii) 13.5% CO
2
, 0.5% O
2
, and 84.8% N
2
. Kernel infections by
A. flavus, Fusarium moniliforme
(Sheld.) Snyd. et Hans., and other fungi were monitored weekly. The modified-atmosphere treatments delayed deterioration by
A. flavus
and
F. moniliforme
, but their growth was not completely stopped.
A. flavus
survived better in the remoistened than in the freshly harvested corn.
F. moniliforme
survived in both.
A. flavus
and
F. moniliforme
were the dominant fungi in corn removed from the modified atmospheres and exposed to normal air for 1 week.
Factors Affecting the Production of Sterigmatocystin in Semisynthetic Media
Authors: Halls N. A. , Ayres J. C.
Published: December 2020

Production of sterigmatocystin by
Aspergillus versicolor
was stimulated by inorganic phosphate when used in conjunction with citric acid cycle compounds.
Inhibition of Methanogenesis in Marine Sediments by Acetylene and Ethylene: Validity of the Acetylene Reduction Assay for Anaerobic Microcosms
Authors: Oremland Ronald S. , Taylor Barrie F.
Published: December 2020

Methanogenesis was irreversibly inhibited in sediments by concentrations of acetylene employed in nitrogen fixation assays (1 to 20%, vol/vol). Ethylene, but not ethane, also stopped methane production, and the inhibition was reversed by gassing with hydrogen.
Carbohydrate Catabolism of Selected Strains in the Genus
Agrobacterium
Authors: Arthur Larry O. , Nakamura Lawrence K. , Julian Grant St. , Bulla Lee A.
Published: December 2020

Radiorespirometric and enzyme analyses were used to reveal the glucose-catabolizing mechanisms functioning in single strains of seven presumed
Agrobacterium
species. The Entner-Doudoroff and pentose cycle pathways functioned in
A. radiobacter, A. tumefaciens, A. rubi,
and
A. rhizogenes
. Whereas both catabolic pathways were utilized to an almost equal degree in the
A. radiobacter
and
A. tumefaciens
strains, use of the Entner-Doudoroff pathway predominated in the
A. rubi
and
A. rhizogenes
strains.
A. stellulatum
catabolized glucose almost solely through the Entner-Doudoroff pathway. In
A. pseudotsugae
and
A. gypsophilae
, glucose was metabolized mainly through the Emden-Meyerhof-Parnas pathway; the pentose phosphate pathway was also utilized.
Detection of Salmonellae in the Environment
Authors: Thomason Berenice M. , Biddle James W. , Cherry William B.
Published: December 2020

The incidence of salmonellae in contrasting environments was compared in this study. Samples collected from or near surface waters in a lush hardwood forest yielded four salmonellae serotypes from six culturally positive samples. A total of 76 samples collected from the top of a granite outcropping over a 3-month period yielded 10 positive samples. Only two salmonellae serotypes were isolated, and one of these was isolated only once. The nature of the sample material had no significant effect on the detection of salmonellae from the two sampling sites. However, the presence or absence of visible moisture in the sample significantly affected the recovery of salmonellae. The results showed that even a harsh environment such as that found on top of Stone Mountain may serve as an ecological niche for the survival and transmission of salmonellae.
Effect of Added Iron on the Formation of Clostridial Inhibitors
Authors: Huhtanen C. N. , Wasserman A. E.
Published: December 2020

Inhibition of
Clostridium botulinum
by nitrite was potentiated by the addition of Fe(II) or Fe(III) to the culture medium. The effect of iron was more pronounced when nitrite was added after autoclaving.
Prodiginine (Prodigiosin-Like) Pigments from
Streptoverticillium rubrireticuli
, an Organism That Causes Pink Staining of Polyvinyl Chloride
Authors: Gerber Nancy N. , Stahly Donald P.
Published: December 2020

Red pigments were extracted from
Streptoverticillium rubrireticuli
strain 100-19, an organism frequently incriminated in pink staining of polyvinyl chloride. These pigments were identified as undecylprodiginine and butylcycloheptylprodiginine.
Influence of Carbohydrate and Nitrogen Source on Patulin Production by
Penicillium patulum
Authors: Stott W. T. , Bullerman L. B.
Published: December 2020

A strain of
Penicillium patulum
, isolated from cheddar cheese, produced patulin when grown on liquid media containing lactose and milk nitrogen sources. Patulin production was affected by the temperature of incubation, the type and amount of carbohydrate, and the type of nitrogen source present. Patulin levels generally were depressed by incubation at 5 C and low carbohydrate levels. Patulin was produced at low levels in the absence of sugars at 5 C when the mold was grown on milk nitrogen sources. No patulin was detected in cultures grown on 25% casein slurries or cheddar cheese, even though growth of the mold was extensive.
Interaction Between Aflatoxicosis and a Natural Infection of Chickens with
Salmonella
Authors: Wyatt R. D. , Hamilton P. B.
Published: December 2020

Broiler chicks with a natural congenital infection of
Salmonella worthington
required a lower concentration of dietary aflatoxin (0.625 μg/g) to depress growth than uninfected chicks (2.50 μg/g).
Evaluation of Coli-Count Samplers for Possible Use in Standard Counting of Total and Fecal Coliforms in Recreational Waters
Authors: Hedberg Mary , Connor Douglas A.
Published: December 2020

Millipore Coli-Count Samplers were used to enumerate colonies of laboratory cultures of coliform bacteria. The samplers gave significantly lower counts than standard membrane-filter procedures for both total and fecal coliforms. Although the samplers are useful for semiquantitative analysis as indicated by the manufacturer, they are not suitable for standard examinations of recreational waters.
Cross-reactive antigens and lectin as determinants of symbiotic specificity in the Rhizobium-clover association
Authors: Dazzo F B , Hubbell D H
Published: December 2020

Cross-reactive antigens of clover roots and Rhizobium trifolii were detected on their cell surfaces by tube agglutination, immunofluorescent, and radioimmunoassay techniques. Anti-clover root antiserum had a higher agglutinating titer with infective strains of R. trifolii than with noninfective strains. The root antiserum previously adsorbed with noninfective R. trifolii cells remained reactive only with infective cells, including infective revertants. When adsorbed with infective cells, the root antiserum was reactive with neither infective nor noninfective cells. Other Rhizobium species incapable of infecting clover did not demonstrate surface antigens cross-reactive with clover. Radioimmunoassay indicated twice as much antigenic cross-reactivity of clover roots and R. trifolii 403 (infective) than R. trifolii Bart A (noninfective). Immunofluorescence with anti-R. trifolii (infective) antiserum was detected on the exposed surface of the root epidermal cells and diminished at the root meristem. The immunofluorescent crossreaction on clover roots was totally removed by adsorption of anti-R. trifolii (infective) antiserum with encapsulated infective cells but not with noninfective cells. The cross-reactive capsular antigens from R. trifolii strains were extracted and purified. The ability of these antigens to induce clover root hair deformation was much greater when they were obtained from the infective than noninfective strains. The cross-reactive capsular antigen of R. trifolii 403 was characterized as a high-molecular-weight (greater than 4.6 times 10(6) daltons), beta-linked, acidic heteropolysaccharide containing 2-deoxyglucose, galactose, glucose, and glucuronic acid. A soluble, nondialyzable, substance (clover lectin) capable of binding to the cross-reactive antigen and agglutinating only infective cells of R. trifolii was extracted from white clover seeds. This lectin was sensitive to heat, Pronase, and trypsin. inhibition studies indicated that 2-deoxyglucose was the most probable haptenic determinant of the cross-reactive capsular antigen capable of binding to the root antiserum and the clover lectin. A model is proposed suggesting the preferential adsorption of infective versus noninfective cells of R. trifolii on the surface of clover roots by a cross-bridging of their common surface antigens with a multivalent clover lectin.
Repulsion of bacteria from marine surfaces
Authors: Chet I , Asketh P , Mitchell R
Published: December 2020

Organic compounds are capable of repelling motile bacteria from marine surfaces. The most effective compounds were acrylamide and benzoic and tannic acids. These were active at concentrations that were not toxic to the bacteria. Repellents were incorporated in nontoxic paints and applied to metal panels. Treated panels immersed in seawater developed a bacterial film of only 10(6) bacteria per cm6 after 12 days compared with untreated panels, which had 5 times 10(12) bacteria per cm2 after the same period. Field studies confirmed the effectiveness of these repellents. The use of biological repellents provides a new approach to the control of marine fouling.
Separation of Spores and Parasporal Crystals of
Bacillus thuringiensis
in Gradients of Certain X-Ray Contrasting Agents
Authors: Sharpe Eugene S. , Nickerson Kenneth W. , Bulla Lee A. , Aronson John N.
Published: December 2020

Spores and parasporal crystals of
Bacillus thuringiensis
can be separated at moderate centrifugation speeds (10,000 to 12,000 rpm) in gradients of Renografin or sodium diatrizoate.
Incorporation of (2-14C)acetate into lipids of mink (Mustela vison) liver and intestine during in vitro and in vivo treatment with aflatoxin B1
Authors: Chou C C , Marth E H
Published: December 2020

The in vitro and in vivo incorporation of (2-14C)acetate into lipids of mink (Mustela vison) liver and intestines was studied. In vitro, a dose of aflatoxin B1 as small as 7.5 mug/ml of medium reduced by 20% the amount of (2-14C)acetate incorporated into lipids of mink liver slices, whereas 180 mug caused 76% reduction in the synthesis of lipids from the radioactive precusor. Similar inhibition of lipid synthesis by aflatoxin also was observed with tissues from mink intestines and fatty liver. The degree of inhibition (19 to 84% for tissue from intestines and 19 to 64% for tissue from fatty livers) depended on the amount of aflatoxin B1 (7.5 TO 180 MUG) present in the medium. In vivo, a substantially increased amount of 14C-labeled lipids was found in the livers of mink injected with 600 mug of aflatoxin B1 per kg of body weight 20, 28, and 40 h earlier. However, no appreciable difference in incorporation of (2-14C)acetate into lipids was observed between toxin-treated and control animals when these animals were sacrificed and examined for 14C-labeled lipids at 4 and 10 h after toxin was administered.
Tetramethyl-p-phenylenediamine oxidase reaction in Azotobacter vinelandii
Authors: Jurtshuk P , Marcucci O M , McQuitty D N
Published: December 2020

It was possible to quantitate the tetramethyl-p-phenylenediamine (TMPD) oxidase reaction in Azotobacter vinelandii strain O using turbidimetrically standarized resting cell suspensions. The Q(O2) value obtained for whole cell oxidation of ascorbate-TMPD appeared to reflect the full measure of the high respiratory oxidative capability usually exhibited by this genera of organisms. The Q(O2) value for the TMPD oxidase reaction ranged from 1,700 to 2,000 and this value was equivalent to that obtained for the oxidation of the growth substrate, e.g., acetate. The kinetic analyses for TMPD oxidation by whole cells was similar to that obtained for the "particulate" A. vinelandii electron transport particle, that fraction which TMPD oxidase activity is exclusively associated with. Under the conditions used, there appeared to be no permeability problems; TMPD (reduced by ascorbate) readily penetrated the cell and oxidized at a rate comparable to that of the growth substrate. This, however, was not true for the oxidation of another electron donor, 2,6-dichloroindophenol, whose whole cell Q(O2) values, under comparable conditions, were twofold lower. The TMPD oxidase activity in A. vinelandii whole cells was found to be affected by the physiological growth conditions, and resting cells obtained from cells grown on sucrose, either under nitrogen-fixing conditions or on nitrate as the combined nitrogen source, exhibited low TMPD oxidase rates. Such low TMPD oxidase rates were also noted for chemically induced pleomorphic A. vinelandii cells, which suggests that modified growth conditions can (i) alter the nature of the intracellular terminal oxidase formed (or induced), or (ii) alter surface permeability, depending upon the growth conditions used. Preliminary studies on the quantitative TMPD oxidation reaction in mutant whole cells of both Azotobacter and a well-known Mucor bacilliformis strain AY1, deficient in cytochrome oxidase activity, showed this assay can be very useful for detecting respiratory deficiencies in the metabolism of whole cells.
Distribution and effects of 2,4,5-trichlorophenoxyacetic acid in cells of Bacillus megaterium
Authors: Hicks G F , Corner T R
Published: December 2020

Cell death in a resting population of an asporogenous Bacillus megaterium was accelerated by ambient concentrations of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) equal to or greater than 10 mug/ml or 5 mug/mg of cells (dry weight), but only after prolonged exposure. Conversely, populations of growing cells were not markedly influenced even at 100 mug/ml. Effects on cell respiration were not manifest until the ambient concentration reached 1,000 mug of 2,4,5-T/ml, or 500 mug/mg. Cells of B. megaterium did, however, accumulate 2,4,5-T passively to a level approximately twofold above the ambient concentration. Most of the accumulated compound was easily washed from the cells, but, of the firmly bound herbicide, about 0.5 mug/mg of cells (dry weight), nearly 60% by weight, was localized in the protoplast membrane. The foregoing results, obtained with a purified preparation of 2,4,5-T were also elicited by 2,4,5-T analytical standards. The extracted contaminants did not produce the results alone nor did they influence the results when present in combination with 2,4,5-T.
Accelerated Fermentation of Brewer's Wort by
Saccharomyces carlsbergensis
Authors: Porter Sookie C.
Published: December 2020

A rapid procedure for wort fermentation with
Saccharomyces carlsbergensis
at 12 C is described. Fermentation time was reduced from 7 to 4 days with normal inoculum by shaking. Increasing the inoculation to 5 to 10 times normal and shaking resulted in complete fermentation in 3 days. Maximum yeast population was reached rapidly with the large inocula, but fermentation proceeded at approximately the same rate when inoculations in excess of four times the normal were used. Similar results were obtained with both small-scale (100 ml) and microbrew (2.4 liters) fermentations.
Continuous Culture as a Method for Studying Rumen Fermentation
Authors: Stewart Daryl G. , Warner R. G. , Seeley H. W.
Published: December 2020

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Detection and Enumeration of Fecal Indicator Organisms in Frozen Sea Foods
Authors: Raj H. , Wiebe W. J. , Liston J.
Published: December 2020

Consistently high recoveries of enterococci as compared to the low numbers of coliforms obtained from the same samples of frozen sea foods are indirect evidence that enterococci are better indicators of contamination in such foods.

The use of azide dextrose broth, modified by the incorporation of bromthymol blue, and of ethyl violet azide broth as presumptive and confirmation tests, respectively, were found to be highly specific for the detection and enumeration of enterococci in these samples. Tetrazolium agar medium, when used as a third step after the confirmation test, provides a reliable differentiation of
Streplococcus faecalis
types from other group D streptococci. A simple procedure is described for further identification of
S. faecalis
varieties and other enterococcal species.

Incidence of biotypes within certain species is noted and relationships of these subgroups to the organisms described by other workers is discussed.

The striking resistance of all group D streptococci to dihydrostreptomycin and polymyxin B seems to offer promise for evolving a new selective medium for these organisms.
Resistance of Salmonellae Isolated in 1959 and 1960 to Tetracyclines and Chloramphenicol
Authors: Ramsey Carolyn H. , Edwards P. R.
Published: December 2020

The resistance of cultures of
Salmonella typhimurium
to tetracyclines and chloramphenicol has been examined periodically. Although none of 200 cultures isolated prior to 1948 was resistant to the antibiotics, 5% of 100 cultures from man and 9% of 100 cultures from fowls which were isolated in 1956 and 1957 were resistant to tetracyclines. Among 158 cultures isolated from man and 100 cultures isolated from fowls in 1959 and 1960, 13.9 and 29%, respectively, were resistant to tetracyclines. In the last series, cultures resistant to chloramphenicol were found for the first time. Among 150 cultures of other
Salmonella
serotypes from man and 137 similar cultures isolated from fowls in 1959 and 1960, 5.3 and 8%, respectively, were found resistant to tetracyclines. There is no obvious explanation for the higher percentage of resistant strains occurring in
S. typhimurium
than in other serotypes.
Purity Control of the Production of Baker's Yeast Employing a Fluorescent Antiserum
Authors: Kunz Ch. , Klaushofer H.
Published: December 2020

A simple staining procedure for the rapid detection of wild yeasts contaminating baker's yeast during the course of industrial production is described. Fluorescein-labeled, specific antiserum against
Saccharomyces cerevisiae
is applied to smears of baker's yeast which are then examined by ultraviolet microscopy. Optimal results are obtained with the combined phase contrast and fluorescence which makes the
S. cerevisiae
appear green, whereas cells of wild yeasts are visible in bright red counterstain. With this method, wild yeasts could be identified in baker's yeast at a dilution of 1:10,000.
Studies on Disinfection of Clinical Thermometers
Authors: Wright Eleanore S. , Mundy R. A.
Published: December 2020

A study was made of the chemical disinfection of oral thermometers used by patients with active pulmonary tuberculosis. Only 10% of these thermometers were found to be contaminated with acid-fast bacilli. Because of this small number, the use of a phenol coefficient type test with
Mycobacterium tuberculosis
was suggested as an alternative method for evaluating tuberculocidal activity. These data, in conjunction with data from Part I of these studies dealing with disinfection of oral thermometers from a general hospital, were the criteria used to judge the efficacy of the disinfectants. It was concluded that 70% ethyl alcohol, 2% phenolic no. 1, and 3% phenolic no. 3 were reliable disinfectants for thermometers. Fifty per cent ethyl alcohol, 2% phenolic no. 2, 2% iodophor (300 ppm available iodine), and 0.1% benzalkonium chloride, aqueous or tincture, were unreliable.
Rates of Production of Individual Volatile Fatty Acids in the Rumen of Lactating Cows
Authors: Hungate R. E. , Mah Robert A. , Simesen Mogens
Published: December 2020

The rumen fermentation rates in individual lactating cows were measured in four different experiments. The results disclosed that the amounts and proportions of volatile acids formed could vary widely. In one case, a marked difference in the proportions of the acids produced arose within the experiment and correlated with a difference in the proportion of methane formed.

The average rate of production per day was 10.5 moles butyric acid, 12.8 moles propionic acid, and 40 moles acetic acid. Manometric estimations of rate gave lower results than those obtained by the zero-time method, due to delay after sampling and to failure of the acids to liberate stoichiometric quantities of carbon dioxide.

For those experiments in which zero-time rates were estimated, the average specific absorption rates, i.e., the amount absorbed per hour per micromole of acid in the rumen, were 0.37 for butyric acid, 0.38 for propionic acid, and 0.26 for acetic acid.

The carbon dioxide, acids, and microbial cells produced in the rumen fermentation are estimated to account for about 90% of the carbon found in the milk and respiratory CO
2
of the cows. The carbon dioxide from the fermentation was about 27% of the carbon dioxide exhaled.
Metabolic growth rate control in Escherichia coli may be a consequence of subsaturation of the macromolecular biosynthetic apparatus with substrates and catalytic components
Authors: Jensen K F , Pedersen S
Published: December 2020

In this paper, the Escherichia coli cell is considered as a system designed for rapid growth, but limited by the medium. We propose that this very design causes the cell to become subsaturated with precursors and catalytic components at all levels of macromolecular biosynthesis and leads to a molecular sharing economy at a high level of competition inside the cell. Thus, the promoters compete with each other in the binding of a limited amount of free RNA polymerase and the ribosome binding sites on the mRNA chains compete with each other for the free ribosomes. The macromolecular chain elongation reactions sequester a considerable proportion of the total amount of RNA polymerase and ribosomes in the cells. We propose that the degree of subsaturation of the macromolecular biosynthetic apparatus renders a variable fraction of RNA polymerase and ribosomes unavailable for the initiation of new chain synthesis and that this, at least in part, determines the composition of the cell as a function of the growth rate. Thus, at rapid growth, the high speed of the elongation reactions enables the cell to increase the concentrations of free RNA polymerase and ribosomes for initiation purposes. Furthermore, it is proposed that the speed of RNA polymerase movement is adjusted to the performance speed of the ribosomes. Mechanistically, this adjustment of the coupling between transcription and translation involves transcriptional pause sites along the RNA chains, the adjustment of the saturation level of RNA polymerase with the nucleoside triphosphate substrates, and the concentration of ppGpp, which is known to inhibit RNA chain elongation. This model is able to explain the stringent response and the control of stable RNA and of ribosome synthesis in steady states and in shifts, as well as the rate of overall protein synthesis as a function of the growth rate.
PET genes of Saccharomyces cerevisiae
Authors: Tzagoloff A , Dieckmann C L
Published: December 2020

We describe a collection of nuclear respiratory-defective mutants (pet mutants) of Saccharomyces cerevisiae consisting of 215 complementation groups. This set of mutants probably represents a substantial fraction of the total genetic information of the nucleus required for the maintenance of functional mitochondria in S. cerevisiae. The biochemical lesions of mutants in approximately 50 complementation groups have been related to single enzymes or biosynthetic pathways, and the corresponding wild-type genes have been cloned and their structures have been determined. The genes defined by an additional 20 complementation groups were identified by allelism tests with mutants characterized in other laboratories. Mutants representative of the remaining complementation groups have been assigned to one of the following five phenotypic classes: (i) deficiency in cytochrome oxidase, (ii) deficiency in coenzyme QH2-cytochrome c reductase, (iii) deficiency in mitochondrial ATPase, (iv) absence of mitochondrial protein synthesis, and (v) normal composition of respiratory-chain complexes and of oligomycin-sensitive ATPase. In addition to the genes identified through biochemical and genetic analyses of the pet mutants, we have cataloged PET genes not matched to complementation groups in the mutant collection and other genes whose products function in the mitochondria but are not necessary for respiration. Together, this information provides an up-to-date list of the known genes coding for mitochondrial constituents and for proteins whose expression is vital for the respiratory competence of S. cerevisiae.
Parvovirus replication
Authors: Berns K I
Published: December 2020

The members of the family Parvoviridae are among the smallest of the DNA viruses, with a linear single-stranded genome of about 5 kilobases. Currently the family is divided into three genera, two of which contain viruses of vertebrates and a third containing insect viruses. This review concentrates on the vertebrate viruses, with emphasis on recent advances in our insights into the molecular biology of viral replication. Traditionally the vertebrate viruses have been distinguished by the presence or absence of a requirement for a coinfection with a helper virus before productive infection can occur, hence the notion that the dependoviruses (adeno-associated viruses [AAV]) are defective. Recent data would suggest that not only is there a great deal of structural and genetic organizational similarity between the two types of vertebrate viruses, but also there is significant similarity in the molecular biology of productive replication. What differs is the physiological condition of the host cell that renders it permissive. Healthy dividing cells are permissive for productive replication by autonomous parvoviruses; such cells result in latent infection by dependoviruses. For a cell to become permissive for productive AAV replication, it must have been exposed to toxic conditions which activate a latent AAV genome. Such conditions can be caused by helper-virus infection or exposure to physical (UV light) or chemical (some carcinogens) agents. In this paper the molecular biology of replication is reviewed, with special emphasis on the role of the host and the consequences of viral infection for the host.
Adherence and receptor relationships of Candida albicans
Authors: Calderone R A , Braun P C
Published: December 2020

The cell surface of Candida albicans is composed of a variety of polysaccharides such as glucan, chitin, and mannan. The first two components primarily provide structure, while the mannan, often covalently linked to protein, constitutes the major antigen of the organism. Mannoproteins also have enzymatic activity (acid protease) and ligand-receptor functions. The complement receptors of C. albicans appear to be mannoproteins that are required for the adherence of the organism to endothelial cells. This is certainly true of the CR3-like protein of C. albicans. Proof that the CR3 is the Candida receptor for endothelial cells is derived from two observations. First, mutants lacking CR3 activity are less adherent in vitro and, in fact, less virulent. Second, the ligand recognized by the CR3 receptor (C3bi) as well as anti-CR3 antibodies blocks adherence of the organism to endothelial cells. The CR2 of C. albicans appears to promote the adherence of the organism to plastic substrates. Unlike the CR2 of mammalian cells, the Candida CR2 recognizes ligands containing the RGD sequence of amino acids in addition to the C3d ligand, which does not contain the RGD sequence. There is uncertainty as to whether the Candida CR2 and CR3 are, in fact, different proteins. A mannoprotein has also been described as the adhesin for epithelial cells. In this case, the receptor has a lectinlike activity and recognizes fucose- or glucosamine-containing glycoproteins of epithelial cells, depending on the strain of C. albicans. The oligosaccharide component of the receptor is probably not involved in ligand recognition and may serve to stabilize the receptor. However, the oligosaccharide factor 6 epitope of mannan may also provide adhesin activity in the recognition of epithelial cells. Mannoproteins can be extracted from cells by a number of reagents. Zymolyase, for instance, tends to remove structural mannoproteins, which contain relatively little protein and are linked to glucan. Reagents such as dithiothreitol, on the other hand, tend to extract mannoproteins containing higher amounts of protein that appear to have receptor function. The mannoproteins of C. albicans are dynamically expressed and may be growth phase and growth form specific.
Lyme borreliosis: host responses to Borrelia burgdorferi
Authors: Szczepanski A , Benach J L
Published: December 2020

The chronic inflammatory condition that develops after infection by B. burgdorferi is a complex process resulting from host responses to a limited number of organisms. Amplification mechanisms driven by potent proinflammatory molecules, i.e., IL-1, may explain the vigorous response to a paucity of organisms. Spirochete dissemination to distant locations involves adherence to and penetration across endothelium and may be facilitated by host responses that increase vessel permeability. The apparent lack of tissue tropism in Lyme disease is reflected in the organism's ability to adhere to different eucaryotic cell types in vitro and the wide distribution of B. burgdorferi in various organs of infected humans and experimentally infected animals. While phagocytosis and complement activation have been observed in vitro, the specific immune response that develops in humans is inefficient in eradicating the organisms, which may possess some mechanism(s) to evade this response. There is significant evidence for host autoreactivity based on antigenic cross-reactivity between the 41-kDa flagellar subunit and stress proteins of the spirochetes and endogenous host cell components. Although the outer surface proteins appear to be suitable candidates as targets for vaccination in animal studies, fundamental differences in the immune response to spirochetal components may preclude their use in humans.
Control site location and transcriptional regulation in Escherichia coli
Authors: Collado-Vides J , Magasanik B , Gralla J D
Published: December 2020

The regulatory regions for 119 Escherichia coli promoters have been analyzed, and the locations of the regulatory sites have been cataloged. The following observations emerge. (i) More than 95% of promoters are coregulated with at least one other promoter. (ii) Virtually all sigma 70 promoters contain at least one regulatory site in a proximal position, touching at least position -65 with respect to the start point of transcription. There are not yet clear examples of upstream regulation in the absence of a proximal site. (iii) Operators within regulons appear in very variable proximal positions. By contrast, the proximal activation sites of regulons are much more fixed. (iv) There is a forbidden zone for activation elements downstream from approximately position -20 with respect to the start of transcription. By contrast, operators can occur throughout the proximal region. When activation elements appear in the forbidden zone, they repress. These latter examples usually involve autoregulation. (v) Approximately 40% of repressible promoters contain operator duplications. These occur either in certain regulons where duplication appears to be a requirement for repressor action or in promoters subject to complex regulation. (vi) Remote operator duplications occur in approximately 10% of repressible promoters. They generally appear when a multiple promoter region is coregulated by cyclic AMP receptor protein. (vii) Sigma 54 promoters do not require proximal or precisely positioned activator elements and are not generally subject to negative regulation. Rationales are presented for all of the above observations.
DNA methylation and gene expression
Authors: Razin A , Cedar H
Published: December 2020

A large body of evidence demonstrates that DNA methylation plays a role in gene regulation in animal cells. Not only is there a correlation between gene transcription and undermethylation, but also transfection experiments clearly show that the presence of methyl moieties inhibits gene expression in vivo. Furthermore, gene activation can be induced by treatment of cells with 5-azacytidine, a potent demethylating agent. Methylation appears to influence gene expression by affecting the interactions with DNA of both chromatin proteins and specific transcription factors. Although methylation patterns are very stable in somatic cells, the early embryo is characterized by large alterations in DNA modification. New methodologies are now becoming available for studying methylation at this stage and in the germ line. During development, tissue-specific genes undergo demethylation in their tissue of expression. In tissue culture cells this process is highly specific and appears to involve an active mechanism which takes place in the absence of DNA replication. The X chromosome undergoes inactivation during development; this is accompanied by de novo methylation, which appears necessary to stably maintain its silent state. As opposed to the programmed changes in DNA methylation which occur in vivo, immortalized tissue culture cells demonstrate alterations in DNA modification which take place over a long time scale and which appear to be the result of selective pressures present during the growth of these cells in culture.
Surface layers of bacteria
Authors: Beveridge T J , Graham L L
Published: December 2020

Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance of the results in terms of our perception of the makeup and function of bacterial surfaces and their interaction with the surrounding environment.
Establishment and expression of cellular polarity in fucoid zygotes
Authors: Kropf D L
Published: December 2020

Zygotes of fucoid algae have long been studied as a paradigm for cell polarity. Polarity is established early in the first cell cycle and is then expressed as localized growth and invariant cell division. The fertilized egg is a spherical cell and, by all accounts, bears little or no asymmetry. Polarity is acquired epigenetically a few hours later in the form of a rhizoid/thallus axis. The initial stage of polarization is axis selection, during which zygotes monitor environment gradients to determine the appropriate direction for rhizoid formation. In their natural setting in the intertidal zone, sunlight is probably the most important polarizing vector; rhizoids form away from the light. The mechanism by which zygotes perceive environmental gradients and transduce that information into an intracellular signal is unknown but may involve a phosphatidylinositol cycle. Once positional information has been recorded, the cytoplasm and membrane are reorganized in accordance with the vectorial information. The earliest detectable asymmetries in the polarizing zygote are localized secretion and generation of a transcellular electric current. Vesicle secretion and the inward limb of the current are localized at the presumptive rhizoid. The transcellular current may establish a cytoplasmic Ca2+ gradient constituting a morphogenetic field, but this remains controversial. Localized secretion and establishment of transcellular current are sensitive to treatment with cytochalasins, indicating that cytoplasmic reorganization is dependent on the actin cytoskeleton. The nascent axis at first is labile and susceptible to reorientation by subsequent environmental vectors but soon becomes irreversibly fixed in its orientation. Locking the axis in place requires both cell wall and F-actin and is postulated to involve an indirect transmembrane bridge linking cortical actin to cell wall. This bridge anchors relevant structures at the presumptive rhizoid and thereby stabilizes the axis. Approximately halfway through the first cell cycle, the latent polarity is expressed morphologically in the form of rhizoid growth. Elongation is by tip growth and does not appear to be fundamentally different from tip growth in other organisms. The zygote always divides perpendicular to the growth axis, and this is controlled by the microtubule cytoskeleton. Two microtubule-organizing centers on the nuclear envelope rotate such that they align with the growth axis. They then serve as spindle poles during mitosis. Cytokinesis bisects the axial spindle, resulting in a transverse crosswall. Although the chronology of cellular events associated with polarity is by now rather detailed, causal mechanisms remain obscure.