bluuebunny/crossref_metadata_2025 huggingface dataset:
Refractive index of a liquid as a function of temperature
Authors: Olney Christopher J.
Published: April 2003

Without a spectrometer, the refractive index of a liquid can be measured as a function of temperature by means of a laser beam, meterstick, and triangular tank. The estimated error is ±0.001.
Using Interactive Physics in planetary motion
Authors: Pei Xiong-Skiba
Published: April 2003

This note demonstrates how to use software
Rocket physics
Authors: Widmark Stephen A.
Published: April 2003

By designing, building, testing, and flying model rockets, high school physics students learn the essential elements of dynamics. In addition, they learn about engineering, drafting, and computer modeling.
Measuring displacement vectors with the GPS
Authors: Larson Roger F.
Published: April 2003

A low -cost Global Positioning System (GPS) is used to determine the magnitude of the resultant of two displacement vectors. A physics class takes a field trip to the school’s football field. Then using the GPS, the students mark the corners of the field. The class then compare the calculated measurement of the field’s diagonal to that obtained from the GPS. Information and references are provided concerning the capabilities and limitations of the GPS.
Does an ideal wheel
really
rotate about its instantaneous point of contact?
Authors: Pritchett Tim , Nelson Raymond C. , Creamer Timothy J. , Oldaker Bruce G.
Published: April 2003

The notion of an instantaneous frame of reference is implicit in the statement that “a wheel which rolls without slipping rotates about its instantaneous point of contact.” We examine the mathematical conditions defining such frames and argue against their use in teaching introductory dynamics.
The surgical-hose rocket
Authors: Nicoll Martin
Published: April 2003

This article describes a lab that verifies the rocket equation derived from Newton’s laws. A novel way of producing constant velocity water from surgical latex tubing is described.
Finicky clay divers
Authors: Cordry Sean M.
Published: April 2003

Clay spheres dropped into a dilute vinegar/baking-soda solution accumulate CO2 bubbles on their surfaces. Spheres below a certain size will then float, otherwise they remain sunken. Students must determine the maximum size that will float by considering the net density of the clay/bubble system.
Drawing forces
Authors: van den Berg Ed , van Huis Cor
Published: April 2003

A force diagram can be a “forceful” way to quickly get insight into a problem and prospects for a solution. A rigid application of some trivial rules can make a force diagram a more forceful tool.
Using the sound board as an analog-to-digital card
Authors: Hansen Kirk , Harnetiaux Mark , Siegel Peter B.
Published: April 2003

We discuss how the sound board, or sound blaster card, can be used as an analog-to-digital data logger in the student laboratory. As an example, we describe an inexpensive electro-cardiogram set-up that uses the line input of the sound board to digitize signals from a simple amplifier circuit.
Misconceptions and their change in university-level astronomy courses
Authors: Zeilik Michael , Schau Candace , Mattern Nancy
Published: April 2003

Students enter courses with prior knowledge of the subject area. Unfortunately, these naive notions often are misconceptions (or “folk concepts”) that hinder learning of appropriate concepts in the field.
First, the question
Authors: Swartz Clifford E.
Published: April 2003

Ideally, every physics lesson, every lecture, every lab should be built around a question. The teacher should use the question as framework and should make the question explicit for the student.
Truth in advertising?—An automobile kinematics problem
Authors: King John G. , French A. P.
Published: April 2003

An advertisement showing a set of photographs of a car accelerating from rest along a straight road is analyzed. It is found that the times marked on the photographs must be incorrect, and a revised analysis is presented.
Star Wars and gravitational constants
Authors: Doherty Ryan , Rembert James “Alex” , Boice Nathan , Laws Priscilla
Published: April 2003

Star Wars takes place in another galaxy in another age and the adventure plays out on “inhabitable” planets unknown to us. Yet, it is curious how all the planets and other astronomical bodies of different sizes and compositions that Star Wars characters visit seem to have the same gravitational field at the surface.
Melde’s experiment with an aquarium aerator. Rich dynamics with inexpensive apparatus
Authors: Graham Mark
Published: April 2003

As the basis for understanding music, quantum mechanics, and optical phenomena, standing waves are tremendously important, but instructors with a shoestring budget may not be able to do laboratories for them. However with simple modification of an inexpensive aquarium aerator costing a few dollars, instructors can take that shoestring and make standing waves.
Using digital video analysis in introductory mechanics projects
Authors: Laws Priscilla , Pfister Hans
Published: April 2003

During the first semester of our calculus-based introductory physics course sequence, students work in small groups on mechanics projects. Many teams choose digital video analysis for projects involving mechanics. We discuss the management of collaborative projects and schemes for critiquing collaborative papers and assigning individual grades. We also describe some of the more interesting projects. Finally, we offer some advice on how to find the information needed to create good digital video movies.
In a dark room, let there be light!
Authors: Brown Michael H.
Published: April 2003

What do you with a helium-filled balloon after you bring it home? Charge it by rubbing it with a wool cloth, and then raise and lower it in a dark room beneath a fluorescent lamp. This will cause the lamp to emit flashes of light!
Using telescopic observations in undergraduate astronomy courses
Authors: Townsend Greg
Published: April 2003

The development of remotely operated telescopes has provided a means for giving students in undergraduate astronomy courses valuable experience in making telescopic observations. This paper alerts physics teachers to the opportunities available on the web.
Select your standards carefully
Authors: Iona Mario
Published: April 2003

I will restrict my comments to physics topics in the National Science Education Standards (NSES), which seem to have some useful recommendations in other areas since they deal with many phases of education, including teacher education, assessment, school systems, content, relations to society and technology, and so on.
Brownian motion using a laser pointer
Authors: Mak Se-yuen
Published: April 2003

In this note, we describe a simple modification of the smoke cell experiment, which enables us to project the Brownian motion of smoke soot on a screen for demonstration. The key changes include the use of a laser pointer for illumination and a microvideo outfit for projection.
As easy as R, G, B
Authors: Parsons Leonard
Published: April 2003

Addition of primary additive colors of light using red, green, and blue lightsticks. Demonstrations of the addition of primary colors red, green, and blue to produce white, yellow, magenta, and cyan using three commercially available lightsticks and a variable speed drill are discussed. The demonstrations are applicable for junior-high and high school science, physics, or chemistry classes.
The Maxwell wheel investigated with MBL
Authors: Pecori Barbara , Torzo Giacomo
Published: April 2003

The Maxwell wheel motion is experimentally investigated by interfacing the system to a PC with a force sensor and a position sensor. Mechanical energy transformations and the impluse-momentum theorem during the “collision” at the end of the string are studied.
Energy conversion by an electric “space heater”
Authors: van den Berg Willem H.
Published: April 2003

By means of measuring the temperature of the air blown by an electric “space heater” one can show students that the air is heated at a rate approximately equal to the rated wattage of the heater.
A simple question with an interesting answer
Authors: Jackson David P.
Published: April 2003

The counter-intuitive result that two containers being filled by different faucets emitting exactly the same amount of water every second will not fill at the same rate is discussed and analyzed.
Slow balloon race
Authors: Bouffard Karen
Published: April 2003

This is the first of a proposed series of columns presenting Physics Olympics “challenges,” activities that can be adapted as classroom laboratory experiments. The slow balloon race is based on Archimedes’ principle.
Gender differences with batteries and bulbs
Authors: Brown Thomas R. , Slater Timothy F. , Adams Jeffrey P.
Published: April 2003

This study explores student performance on a simple hands-on activity commonly referred to as “batteries and bulbs.” A large population of introductory calculus-based physics students formed the subject group. Special consideration was given to gender differences in success rates.
Weight and gravity—the need for consistent definitions
Authors: Morrison Richard C.
Published: April 2003

Everyone who teaches introductory physics is used to dealing with the confusion students experience when first confronted with the difference between mass and weight.
Constructing a portable sundial
Authors: Larson Michelle B.
Published: April 2003

Detailed instructions for low-cost, horizontal sundials that can be created at various levels of complexity for different ages. These sundials are scalable in that they can be made into key chains, necklaces, or into full-size schoolyard projects.
Meteors by radio: Getting started
Authors: Lonc William
Published: April 2003

A system for detecting meteors by radio is described which is simple and reliable, and thought to be suitable as a science fair project. There is a relatively detailed discussion of the various factors involved in such a project, along with some typical results to indicate the kind of data that is possible.
Rutherford meets Einstein
Authors: Bouffard Karen
Published: April 2003

This fourth Olympics column has two activities based on the concept of reflection. The first, an adaptation of the traditional Rutherford scattering activity, can also be used as a lab experiment.
Another look at Atwood’s machine
Authors: LoPresto Michael C.
Published: April 2003

Atwood’s machine is a standard experimental apparatus that is likely to get pushed out of the laboratory portion of the general physics course due to the ever increasing use of microcomputers. To avoid this, I now use the apparatus for an experiment during the work and energy portion of the course which not only allows us to demonstrate those principles but also compare them with Newton’s laws of motion.
The Atwood machine: Two special cases
Authors: West Joseph O. , Weliver Barry N.
Published: April 2003

The effects of the variation of Earth’s gravitational field on a simple Atwood’s machine with identical masses is considered. From rest, the time required for one of the masses to reach the ground is independent of the scale of the problem.
On projectile motion
Authors: Sarafian Haiduke
Published: April 2003

An analytic expression for the path length of a projectile thrown with an initial velocity V0 and angle θ above the horizontal in a vacuum is derived. It is shown that a 56.46° projectile angle maximizes the projectile's path length and this angle is independent of the initial velocity.
Qualitative demonstrations of parallel/series resonance
Authors: Mak Se-yuen
Published: April 2003

Although circuits to show electrical resonance can be found in textbooks, and corresponding components can be purchased easily from equipment suppliers, most students and even teachers do not know why and how each particular value of inductance L, capacitance C, or resistance R has to be chosen.
Another surprise in mechanics
Authors: Cowley E. Roger , Horton George K. , Holton Brian E.
Published: April 2003

We recently published a note describing a spectacular mechanics demonstration. It illustrated simultaneously the three conservation laws of mechanics for momentum, energy, and angular momentum and resulted in an amazingly counterintuitive outcome. In this article we are reporting on a follow-up of a conjecture by Professor John Mallinckrodt of the California State Polytechnic University.
Heath Physics
Authors: Martindale David G. , Heath Robert W. , Konrad William W. , Macnaughton Robert R. , Carle Mark A. ,   Physics Textbook Review Committee
Published: April 2003

This 1992 textbook by D.C. Heath and Co. is one of seven textbooks reviewed in this issue of The Physics Teacher.
Conceptual Physics
Authors: Hewitt Paul ,   Physics Textbook Review Committee
Published: April 2003

The third edition of this textbook by Paul Hewitt is one of seven textbooks reviewed in this issue of The Physics Teacher.
Quibbles, misunderstandings, and egregious mistakes
Authors:   Physics Textbook Review Committee
Published: April 2003

One of the assignments of the review committee was to note physics mistakes in the seven high school texts selected. The items we discuss are common to many of the texts, though not all.
The retrograde motion of Mars
Authors: Erlichson Herman
Published: April 2003

This paper describes the opening laboratory activity in our liberal-arts physics course entitled “Galileo to Newton and Beyond.” The students first draw the orbits of Mars and Earth as seen in a heliocentric reference frame and then examine their drawing from a geocentric reference frame. It is in this frame that they observe the retrograde motion of Mars.
Sound science—A simple and robust hands-on loudspeaker activity
Authors: Johnson Molly , Stonick Virginia
Published: April 2003

This article describes a simple and very robust loudspeaker, comprising nothing more than a cream-cheese tub with lid, a screw, a magnet, wire, and tape. When plugged into a boom-box speaker output, it generates “high-fidelity” sound and much student enthusiasm.
Doing physics blind
Authors: Windelborn Augden F.
Published: April 2003

Originally intended as aids to a visually impaired student, these laboratory ideas are also a learning tool for sighted students and valuable experiences for those seeking to become physics teachers.
The error of our ways
Authors: Swartz Clifford E.
Published: April 2003

In Victorian literature it was usually some poor female who came to see the error of her ways. How prescient of her! How I wish that all writers of manuscripts for The Physics Teacher would come to similar recognition of this centerpiece of measurement. For, Brothers and Sisters, we all err.
Student-friendly precision pendulum
Authors: Peters Randall D.
Published: April 2003

This “simple” Kater pendulum permits students to easily measure Earth’s gravitational field, g≈9.8 m/s2, to a few parts in 10,000. Although an inexpensive commercial instrument will be soon available for purchase, enterprising students are capable of building their own pendulum using the information provided.
Measurement of aeroplane takeoff speed and cabin pressure
Authors: Wardle D. A.
Published: April 2003

Two experiments have been performed aboard a commercial airliner. The first experiment used a pendulum to determine the kinematics of the take-off run. The second experiment used a water-filled manometer to investigate changes in cabin pressure.
Free-body diagrams revisited—I
Authors: Court James E.
Published: April 2003

In 1993 TPT published a set of free-body exercises that I cooked up, and in 1998, Ed van den Berg and Cor van Huis contributed a note with some on-the-mark comments about what to do and what not to do when teaching free-body diagrams. I have a lot of feedback from the original printing, and in response I've prettied up the diagrams, added some, subtracted some, arranged them into categories, and included a separate set of solutions.
Exercises in drawing and utilizing free-body diagrams
Authors: Fisher Kurt
Published: April 2003

A set of graded exercises in drawing free-body diagrams (FBD’s) for one- and two-body configurations is presented. The main focus of these exercises, however, is on the follow-up to the FBD’s in terms of utilizing them to generate the correct expressions for net force.
Looking for scaling laws, or physics with nuts and shells
Authors: Sheets H. David , Lauffenburger James C.
Published: April 2003

Scaling laws relating the volume of a class of objects to a characteristic dimension of the object appear commonly in physics, chemistry, and biology. In this laboratory exercise for an introductory physics course scaling laws are derived for machine nuts and clam shells. In addition to covering a standard problem in physics, determining volume of the object by measuring the buoyant force on it, the biologically interesting idea of scaling laws are incorporated into the same lab.
Puddle of light
Authors: Allocco Maria
Published: April 2003

It’s astounding how many physics principles are visible in a simple puddle in a parking lot.
Artificial right-hand rule device
Authors: Van Domelen David J.
Published: April 2003

A device for aiding disabled students incapable of using the traditional “right-hand rules” in physics is presented, along with instructions for building one from easily obtained materials.
Basic physics of the incandescent lamp (lightbulb)
Authors: MacIsaac Dan , Kanner Gary , Anderson Graydon
Published: April 2003

We describe the basic electrical and optical characteristics of the incandescent lamp (lightbulb), as an appropriate exemplar for use in teaching introductory electricity and magnetism. We discuss filament characteristics, blackbody physics, mechanical bulb manufacture, and halogen technology. Variants of the incandescent bulb are also addressed.
How “full” are the outer planets?
Authors: Shaw Jim
Published: April 2003

The percent “fullness” of the outer planets (using Mars as an example) is calculated.
Festive fractals
Authors: Camp Dane , Chiaverina Chris , Senior Tom
Published: April 2003

Inspired by the laboratory observations of a research group at the University of Maryland, we set out to capture the spirit of the holiday season by photographing festive colored patterns. Red, green, and white light enter the openings in a pyramid of four silver spheres stacked cannonball fashion, while ambient light enters the opening through which the photograph was taken.
“What is man, that thou art mindful of him?”
Authors: Swartz Clifford E.
Published: April 2003

The year ends, a new millennium begins, and we are mindful of the psalmist’s question. Within this century we have expanded the universe we know to profound limits. We have learned that our Sun is a star within a galaxy of 100 billion other stars. We have counted 100 billion other galaxies racing away from each other. There is a limit to all of this. It is our role as humans to measure our universe, and someday, perhaps, to understand it.
A mathematical physics for all students
Authors: Brekke Stewart E.
Published: April 2003

For 23 years I have been teaching physics and other subjects in science and math in Chicago public high schools. In the 1970s, an integration consent decree issued in federal court mandated that, except for impaired learners, all students in the high school where I was teaching must take four years of science and mathematics. The students at Robeson High were poor African-American students, most of whom had weak reading and math backgrounds.
Getting a charge out of transparent tape
Authors: Harrington Randal
Published: April 2003

When two pieces of transparent tape are placed on top of each other (sticky side to nonsticky side) and then separated, it is observed that one piece becomes negatively charged and the other positively charged. The sign of the charge on each piece depends on the brand of tape used. This phenomenon is frequently used to investigate the properties of charge and charged objects in introductory physics courses.
A web-based video digitizing system for the study of projectile motion
Authors: Chow John W. , Carlton Les G. , Ekkekakis Panteleimon , Hay James G.
Published: April 2003

This paper describes a web-based digitized video system for the teaching of projectile motion. The major advantage of a web-based system is that students can complete the digitizing at any location that has access to the World Wide Web.
Novel approach to the oil-drop experiment
Authors: Papirio Anthony , Penchina Claude M. , Sakai Hajime
Published: April 2003

Millikan’s oil-drop experiment has limited accuracy. Using video-imaging techniques, students find the experiment less tedious and more interesting than using the microscope. By providing absolute calibration in the viewing field, and measuring distance directly, students now obtain improved accuracy.
The falling stick with a>g
Authors: Härtel Hermann
Published: April 2003

An inclined stick with one end on the ground drops faster than a free falling object. The traditional form in which this experiment is often carried out has some problems. Its explanation, based on the model of the rigid body, lacks any causal relation. The use of computer simulations can lead to substantial improvements without relying on the model of the rigid body nor on any further mathematical concepts or pre-knowledge.
Decoding the TV remote control
Authors: O’Connell James
Published: April 2003

Digital infrared pulses are generated by a semiconductor light-emitting diode in the remote control devices used with consumer electronics. The pulse string is detected and analyzed using a silicon solar cell as a receiver and educational data taking and analyzing computer programs.
An experiment with Saxon bowls
Authors: Greer Allan , Kincanon Eric
Published: April 2003

To introduce our first-semester physics students to some basic analytic methods, we integrate a bit of history and a unique timing device into our lab. The story is that the Saxons placed a bowl with a hole in its bottom in water and used the time it took the bowl to submerge to limit orations. (A famous Greek prostitute also used such bowls to allocate her customer’s time, an example we do not use in class.) We have our students find a relationship between the diameter of the hole and the time till submergence. Though the original Saxon bowls varied both in hole size and bowl size, for simplicity we vary only the size of the hole.
Measuring Earth’s magnetic field simply
Authors: Stewart Gay B.
Published: April 2003

We describe a simple experiment that allows students to measure, within a factor of two, one of the fundamental quantities of the natural world using inexpensive, familiar materials. Students recruited to physics in the class cite this type of experience as the reason.
A respectable component of learning
Authors: Rehfuss Donald E.
Published: April 2003

The student taking an introductory physics course in which overwhelming emphasis is on open-book problem-solving, or in which formula sheets are allowed with exams, is enrolled in what might be called a “disposable course.”
That for which there is no methods course
Authors: Windelborn Augden F.
Published: April 2003

Storeroom management is a skill that every physics teacher needs to possess in order to be an effective teacher, but it is not taught in the usual generic teaching methods course. The included suggestions serve to draw attention to potential problems and to offer suggestions that could be of benefit to novice as well as experienced teachers.
Cool in the kitchen: Radiation, conduction, and the Newton “hot block” experiment
Authors: Silverman Mark P. , Silverman Christopher R.
Published: April 2003

Despite frequent reference to Newton’s law of cooling in physics and math books, the paper in which Newton reported this law is quite obscure and rarely cited. We have managed to acquire a copy of this paper and discuss the interesting experiment that Newton did in his kitchen. Surprisingly, the paper contains no procedural details or data of any experiments measuring the rate at which a hot object cools. We have performed our own kitchen experiments to investigate the cooling of (a) the burner of an electric range and (b) a block of Styrofoam. Newton’s law provides a poor model for both systems, whose th!!ermal energy loss we can much better understand by examining closely the effects of radiation and conduction.
Kinematics of the long jump
Authors: Tan Ajun , Zumerchik John
Published: April 2003

The long jump is one of the most natural events in track and field athletics. The jumper is allowed to run a 40-m runway at top speed and jump as far as possible from a takeoff board. It is an event in which the natural ability of the athlete plays a large role and technique is of secondary importance. The two most important factors in the long jump are speed and elevation.
Demonstrating the Meissner effect and persistent current
Authors: Brown Ronald
Published: April 2003

The Meissner effect is often demonstrated by levitating a small magnet over a superconducting disk. The demonstration can be extended to show persistent current as well by inducing surface currents and detecting their magnetic field with a small compass.
Knock off the match
Authors: Gardner Martin
Published: April 2003

Carefully balance a nickel on its edge and lay a paper match on top of it as shown. Place an empty glass upside down over the coin and match. The problem: Knock the match off the nickel without causing the nickel to topple over.
Computer-based experiments to measure RC
Authors: Hart Francis X.
Published: April 2003

In this paper I describe the use of Vernier Instrumentation Amplifiers and their ULI interface, controlled by their Datalogger application, to measure the RC time constant of a circuit. Students obtain excellent results for a certain range of resistance and capacitance values.
Kinesthetic astronomy: The sky time lesson
Authors: Morrow Cherilynn A.
Published: April 2003

This kinesthetic astronomy lesson asks students to bend, twist, and move to simulate the Earth’s orbit around the Sun, including an explanation of calendars and seasons.
High Plant Diversity in Eocene South America: Evidence from Patagonia
Authors: Wilf Peter , Cúneo N. Rubén , Johnson Kirk R. , Hicks Jason F. , Wing Scott L. , Obradovich John D.
Published: April 2003

Tropical South America has the highest plant diversity of any region today, but this richness is usually characterized as a geologically recent development (Neogene or Pleistocene). From caldera-lake beds exposed at Laguna del Hunco in Patagonia, Argentina, paleolatitude ∼47°S, we report 102 leaf species. Radioisotopic and paleomagnetic analyses indicate that the flora was deposited 52 million years ago, the time of the early Eocene climatic optimum, when tropical plant taxa and warm, equable climates reached middle latitudes of both hemispheres. Adjusted for sample size, observed richness exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.
Informatics and Quantitative Analysis in Biological Imaging
Authors: Swedlow Jason R. , Goldberg Ilya , Brauner Erik , Sorger Peter K.
Published: April 2003

Biological imaging is now a quantitative technique for probing cellular structure and dynamics and is increasingly used for cell-based screens. However, the bioinformatics tools required for hypothesis-driven analysis of digital images are still immature. We are developing the Open Microscopy Environment (OME) as an informatics solution for the storage and analysis of optical microscope image data. OME aims to automate image analysis, modeling, and mining of large sets of images and specifies a flexible data model, a relational database, and an XML-encoded file standard that is usable by potentially any software tool. With this design, OME provides a first step toward biological image informatics.
Visualizing Signals Moving in Cells
Authors: Weijer Cornelis J.
Published: April 2003

Cells display a highly complex spatiotemporal organization, required to exert a wide variety of different functions, for example, detection, processing, and propagation of nerve impulses by neurons; contraction and relaxation by muscle cells; movement by leukocytes; and adsorption and secretion of nutrients and metabolites by epithelial cells lining the gut. Successful execution of these complex processes requires highly dynamic information transfer between different regions and compartments within cells. Through the development of fluorescent sensors for intracellular signaling molecules coupled with improved microscopic imaging techniques, it has now become possible to investigate signal propagation in cells with high spatial and temporal resolution.
Regulated Cycling of Mitochondrial Hsp70 at the Protein Import Channel
Authors: Liu Qinglian , D'Silva Patrick , Walter William , Marszalek Jaroslaw , Craig Elizabeth A.
Published: April 2003

Hsp70 of the mitochondrial matrix (mtHsp70) provides a critical driving force for the import of proteins into mitochondria. Tim44, a peripheral inner-membrane protein, tethers it to the import channel. Here, regulated interactions were found to maximize occupancy of the active, adenosine 5′-triphosphate (ATP)–bound mtHsp70 at the channel through its intrinsic high affinity for Tim44, as well as through release of adenosine diphosphate (ADP)–bound mtHsp70 from Tim44 by the cofactor Mge1. A model peptide substrate rapidly released mtHsp70 from Tim44, even in the absence of ATP hydrolysis. In vivo, the analogous interaction of translocating polypeptide would release mtHsp70 from the channel. Consistent with the ratchet model of translocation, subsequent hydrolysis of ATP would trap the polypeptide, driving import by preventing its movement back toward the cytosol.
Identification of
Streptomyces coelicolor
Proteins That Are Differentially Expressed in the Presence of Plant Material
Authors: Langlois P. , Bourassa S. , Poirier G. G. , Beaulieu C.
Published: April 2003

Streptomyces coelicolor
and
Lemna minor
were used as a model to study the modulation of bacterial gene expression during plant-streptomycete interactions.
S. coelicolor
was grown in minimal medium with and without
L. minor
fronds. Bacterial proteomes were analyzed by two-dimensional gel electrophoresis, and a comparison of the two culture conditions resulted in identification of 31 proteins that were induced or repressed by the presence of plant material. One-half of these proteins were identified by peptide mass fingerprinting by using matrix-assisted laser desorption ionization-time of flight mass spectrometry. The induced proteins were involved in energetic metabolism (glycolysis, pentose phosphate pathway, oxidative phosphorylation), protein synthesis, degradation of amino acids, alkenes, or cellulose, tellurite resistance, and growth under general physiological or oxidative stress conditions. The repressed proteins were proteins synthesized under starvation stress conditions. These results suggest that root exudates provide additional carbon sources to the bacteria and that physiological adaptations are required for efficient bacterial growth in the presence of plants.
mRNA Extraction and Reverse Transcription-PCR Protocol for Detection of
nifH
Gene Expression by
Azotobacter vinelandii
in Soil
Authors: Bürgmann Helmut , Widmer Franco , Sigler William V. , Zeyer Josef
Published: April 2003

The study of free-living nitrogen-fixing organisms in bulk soil is hampered by the great diversity of soil microbial communities and the difficulty of relating nitrogen fixation activities to individual members of the diazotroph populations. We developed a molecular method that allows analysis of
nifH
mRNA expression in soil in parallel with determinations of nitrogen-fixing activity and bacterial growth. In this study,
Azotobacter vinelandii
growing in sterile soil and liquid culture served as a model system for
nifH
expression, in which sucrose served as the carbon source and provided nitrogen-limited conditions, while amendments of NH
4
NO
3
were used to suppress nitrogen fixation. Soil RNA extraction was performed with a new optimized direct extraction protocol that yielded nondegraded total RNA. The RNA extracts were of high purity, free of DNA contamination, and allowed highly sensitive and specific detection of
nifH
mRNA by a reverse transcription-PCR. The level of
nifH
gene expression was estimated by PCR amplification of reverse-transcribed
nifH
mRNA fragments with
A. vinelandii
-specific
nifH
primers. This new approach revealed that
nifH
gene expression was positively correlated with bulk nitrogen fixation activity in soil (
r
2
= 0.72) and in liquid culture (
r
2
= 0.84) and therefore is a powerful tool for studying specific regulation of gene expression directly in the soil environment.
Enumeration and Characterization of Acidophilic Microorganisms Isolated from a Pilot Plant Stirred-Tank Bioleaching Operation
Authors: Okibe Naoko , Gericke Mariekie , Hallberg Kevin B. , Johnson D. Barrie
Published: April 2003

Microorganisms were enumerated and isolated on selective solid media from a pilot-scale stirred-tank bioleaching operation in which a polymetallic sulfide concentrate was subjected to biologically accelerated oxidation at 45°C. Four distinct prokaryotes were isolated: three bacteria (an
Acidithiobacillus caldus
-like organism, a thermophilic
Leptospirillum
sp., and a
Sulfobacillus
sp.) and one archaeon (a
Ferroplasma
-like isolate). The relative numbers of these prokaryotes changed in the three reactors sampled, and the
Ferroplasma
isolate became increasingly dominant as mineral oxidation progressed, eventually accounting for >99% of plate isolates in the third of three in-line reactors. The identities of the isolates were confirmed by analyses of their 16S rRNA genes, and some key physiological traits (e.g., oxidation of iron and/or sulfur and autotrophy or heterotrophy) were examined. More detailed studies were carried out with the
Leptospirillum
and
Ferroplasma
isolates. The data presented here represent the first quantitative study of the microorganisms in a metal leaching situation and confirm that mixed cultures of iron- and sulfur-oxidizing prokaryotic acidophiles catalyze the accelerated dissolution of sulfidic minerals in industrial tank bioleaching operations. The results show that indigenous acidophilic microbial populations change as mineral dissolution becomes more extensive.
Kraft Pulp Biobleaching and Mediated Oxidation of a Nonphenolic Substrate by Laccase from
Streptomyces cyaneus
CECT 3335
Authors: Arias M. Enriqueta , Arenas María , Rodríguez Juana , Soliveri Juan , Ball Andrew S. , Hernández Manuel
Published: April 2003

A new laccase (EC 1.10.3.2) produced by
Streptomyces cyaneus
CECT 3335 in liquid media containing soya flour (20 g per liter) was purified to homogeneity. The physicochemical, catalytic, and spectral characteristics of this enzyme, as well as its suitability for biobleaching of eucalyptus kraft pulps, were assessed. The purified laccase had a molecular mass of 75 kDa and an isoelectric point of 5.6, and its optimal pH and temperature were 4.5 and 70°C, respectively. The activity was strongly enhanced in the presence of Cu
2+
, Mn
2+
, and Mg
2+
and was completely inhibited by EDTA and sodium azide. The purified laccase exhibited high levels of activity against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,6-dimethoxyphenol and no activity against tyrosine. The UV-visible spectrum of the purified laccase was the typical spectrum of the blue laccases, with an absorption peak at 600 nm and a shoulder around 330 to 340 nm. The ability of the purified laccase to oxidize a nonphenolic compound, such as veratryl alcohol, in the presence of ABTS opens up new possibilities for the use of bacterial laccases in the pulp and paper industry. We demonstrated that application of the laccase from
S. cyaneus
in the presence of ABTS to biobleaching of eucalyptus kraft pulps resulted in a significant decrease in the kappa number (2.3 U) and an important increase in the brightness (2.2%, as determined by the International Standard Organization test) of pulps, showing the suitability of laccases produced by streptomycetes for industrial purposes.
Evolutionary Engineering of
Saccharomyces cerevisiae
for Anaerobic Growth on Xylose
Authors: Sonderegger Marco , Sauer Uwe
Published: April 2003

Xylose utilization is of commercial interest for efficient conversion of abundant plant material to ethanol. Perhaps the most important ethanol-producing organism,
Saccharomyces cerevisiae
, however, is incapable of xylose utilization. While
S. cerevisiae
strains have been metabolically engineered to utilize xylose, none of the recombinant strains or any other naturally occurring yeast has been able to grow anaerobically on xylose. Starting with the recombinant
S. cerevisiae
strain TMB3001 that overexpresses the xylose utilization pathway from
Pichia stipitis
, in this study we developed a selection procedure for the evolution of strains that are capable of anaerobic growth on xylose alone. Selection was successful only when organisms were first selected for efficient aerobic growth on xylose alone and then slowly adapted to microaerobic conditions and finally anaerobic conditions, which indicated that multiple mutations were necessary. After a total of 460 generations or 266 days of selection, the culture reproduced stably under anaerobic conditions on xylose and consisted primarily of two subpopulations with distinct phenotypes. Clones in the larger subpopulation grew anaerobically on xylose and utilized both xylose and glucose simultaneously in batch culture, but they exhibited impaired growth on glucose. Surprisingly, clones in the smaller subpopulation were incapable of anaerobic growth on xylose. However, as a consequence of their improved xylose catabolism, these clones produced up to 19% more ethanol than the parental TMB3001 strain produced under process-like conditions from a mixture of glucose and xylose.
Isolation and Antifungal and Antioomycete Activities of Aerugine Produced by
Pseudomonas fluorescens
Strain MM-B16
Authors: Lee Jung Yeop , Moon Surk Sik , Hwang Byung Kook
Published: April 2003

The bacterial strain MM-B16, which showed strong antifungal and antioomycete activity against some plant pathogens, was isolated from a mountain forest soil in Korea. Based on the physiological and biochemical characteristics and 16S ribosomal DNA sequence analysis, the bacterial strain MM-B16 was identical to
Pseudomonas fluorescens
. An antibiotic active against
Colletotrichum orbiculare
and
Phytophthora capsici
in vitro and in vivo was isolated from the culture filtrates of
P. fluorescens
strain MM-B16 using various chromatographic procedures. The molecular formula of the antibiotic was deduced to be C
10
H
11
NO
2
S (M
+
,
m/z
209.0513) by analysis of electron impact mass spectral data. Based on the nuclear magnetic resonance and infrared spectral data, the antibiotic was confirmed to have the structure of a thiazoline derivative, aerugine [4-hydroxymethyl-2-(2-hydroxyphenyl)-2-thiazoline].
C. orbiculare
,
P. capsici
, and
Pythium ultimum
were most sensitive to aerugine (MICs for these organisms were approximately 10 μg ml
−1
). However, no antimicrobial activity was found against yeasts and bacteria even at concentrations of more than 100 μg ml
−1
. Treatment with aerugine exhibited a significantly high protective activity against development of phytophthora disease on pepper and anthracnose on cucumber. However, the control efficacy of aerugine against the diseases was in general somewhat less than that of the commercial fungicides metalaxyl and chlorothalonil. This is the first study to isolate aerugine from
P. fluorescens
and demonstrate its in vitro and in vivo antifungal and antioomycete activities against
C. orbiculare
and
P. capsici
.
Chlorination of Indicator Bacteria and Viruses in Primary Sewage Effluent
Authors: Tree Julia A. , Adams Martin R. , Lees David N.
Published: April 2003

Wastewater disinfection is used in many countries for reducing fecal coliform levels in effluents. Disinfection is therefore frequently used to improve recreational bathing waters which do not comply with microbiological standards. It is unknown whether human enteric viruses (which are responsible for waterborne disease) are simultaneously inactivated alongside fecal coliforms. This laboratory study focused on the chlorination of primary treated effluent with three doses (8, 16, and 30 mg/liter) of free chlorine as sodium hypochlorite. Seeding experiments showed that inactivation (>5 log
10
units) of
Escherichia coli
and
Enterococcus faecalis
was rapid and complete but that there was poor inactivation (0.2 to 1.0 log
10
unit) of F
+
-specific RNA (FRNA) bacteriophage (MS2) (a potential virus indicator) at all three doses. However, seeded poliovirus was significantly more susceptible (2.8 log
10
units) to inactivation by chlorine than was the FRNA bacteriophage. To ensure that these results were not artifacts of the seeding process, comparisons were made between inactivation rates of laboratory-seeded organisms in sterilized sewage and inactivation rates of organisms occurring naturally in sewage. Multifactorial analysis of variance showed that there was no significant difference (
P
> 0.05) between the inactivation rates for seeded and naturally occurring FRNA bacteriophage. However, laboratory-grown poliovirus was inactivated much more rapidly than were naturally occurring, indigenous enteroviruses (
P
< 0.001). This may reflect differences in the way indigenous virus is presented to the disinfectant. Inactivation rates for indigenous enteroviruses were quite similar to those seen for FRNA bacteriophage at lower doses of chlorine. These results have significance for the effectiveness of chlorination as a sewage treatment process, particularly where virus contamination is of concern, and suggest that FRNA bacteriophage would be an appropriate indicator of such viral inactivation under field conditions.
Effects of Inactivation and Constitutive Expression of the Unfolded- Protein Response Pathway on Protein Production in the Yeast
Saccharomyces cerevisiae
Authors: Valkonen Mari , Penttilä Merja , Saloheimo Markku
Published: April 2003

One strategy to obtain better yields of secreted proteins has been overexpression of single endoplasmic reticulum-resident foldases or chaperones. We report here that manipulation of the unfolded-protein response (UPR) pathway regulator,
HAC1
, affects production of both native and foreign proteins in the yeast
Saccharomyces cerevisiae
. The effects of
HAC1
deletion and overexpression on the production of a native protein, invertase, and two foreign proteins,
Bacillus amyloliquefaciens
α-amylase and
Trichoderma reesei
endoglucanase EGI, were studied. Disruption of
HAC1
caused decreases in the secretion of both α-amylase (70 to 75% reduction) and EGI (40 to 50% reduction) compared to the secretion by the parental strain. Constitutive overexpression of
HAC1
caused a 70% increase in α-amylase secretion but had no effect on EGI secretion. The invertase levels were twofold higher in the strain overexpressing
HAC1
. Also, the effect of the active form of
T. reesei hac1
was tested in
S. cerevisiae
.
hac1
expression caused a 2.4-fold increase in the secretion of α-amylase in
S. cerevisiae
and also slight increases in invertase and total protein production. Overexpression of both
S. cerevisiae HAC1
and
T. reesei hac1
caused an increase in the expression of the known UPR target gene
KAR2
at early time points during cultivation.
Identification of Equine Cecal Bacteria Producing Amines in an In Vitro Model of Carbohydrate Overload
Authors: Bailey S. R. , Baillon M.-L. , Rycroft A. N. , Harris P. A. , Elliott J.
Published: April 2003

Acute laminitis has been associated with the overgrowth of gram-positive bacteria within the equine hindgut, causing the release of factor(s) leading to ischemia-reperfusion of the digits. The products of fermentation which trigger acute laminitis are, as yet, unknown; however, vasoactive amines are possible candidates. The objectives of this study were to use an in vitro model of carbohydrate overload to study the change in populations of cecal streptococci and lactobacilli and to establish whether certain species of these bacteria were capable of producing vasoactive amines from amino acids. Cecal contents from 10 horses were divided into aliquots and incubated anaerobically with either corn starch or inulin (fructan; both at 1 g/100 ml). Samples were taken at 6-h intervals over a 24-h period for enumeration of streptococci, lactobacilli, and gram-negative anaerobes by a dilution method onto standard selective growth media. The effects of the antibiotic virginiamycin (1 mg/100 ml) and calcium hydrogen phosphate (CaHPO
4
; 0.3 g/100 ml) were also examined. Fermentation of excess carbohydrate was associated with increases in numbers of streptococci and lactobacilli (2- to 3.5-log unit increases; inhibited by virginiamycin) but numbers of gram-negative anaerobes were not significantly affected. A screening agar technique followed by 16S rRNA gene sequence analysis enabled the identification of 26 different bacterial strains capable of producing one or more vasoactive amines. These included members of the species
Streptococcus bovis
and five different
Lactobacillus
spp. These data suggest that certain bacteria, whose overgrowth is associated with carbohydrate fermentation, are capable of producing vasoactive amines which may play a role in the pathogenesis of acute laminitis.
Metabolism of Fructooligosaccharides by
Lactobacillus paracasei
1195
Authors: Kaplan Handan , Hutkins Robert W.
Published: April 2003

Fermentation of fructooligosaccharides (FOS) and other oligosaccharides has been suggested to be an important property for the selection of bacterial strains used as probiotics. However, little information is available on FOS transport and metabolism by lactic acid bacteria and other probiotic bacteria. The objectives of this research were to identify and characterize the FOS transport system of
Lactobacillus paracasei
1195. Radiolabeled FOS was synthesized enzymatically from [
3
H]sucrose and purified by column and thin-layer chromatography, yielding three main products: glucose (G) α-1,2 linked to two, three, or four fructose (F) units (GF
2
, GF
3
, and GF
4
, respectively). FOS hydrolysis activity was detected only in cell extracts prepared from FOS- or sucrose-grown cells and was absent in cell supernatants, indicating that transport must precede hydrolysis. FOS transport assays revealed that the uptake of GF
2
and GF
3
was rapid, whereas little GF
4
uptake occurred. Competition experiments showed that glucose, fructose, and sucrose reduced FOS uptake but that other mono-, di-, and trisaccharides were less inhibitory. When cells were treated with sodium fluoride, iodoacetic acid, or other metabolic inhibitors, FOS transport rates were reduced by up to 60%; however, ionophores that abolished the proton motive force only slightly decreased FOS transport. In contrast, uptake was inhibited by
ortho
-vanadate, an inhibitor of ATP-binding cassette transport systems. De-energized cells had low intracellular ATP concentrations and had a reduced capacity to accumulate FOS. These results suggest that FOS transport in
L. paracasei
1195 is mediated by an ATP-dependent transport system having specificity for a narrow range of substrates.