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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

On a Self-Tuning Impact Vibration Damper for Rotating Turbomachinery

A self-tuning impact damper is investigated analytically and experimentally as a device to inhibit vibration and increase the fatigue life of rotating components in turbomachinery. High centrifugal loads in rotors can inactivate traditional impact dampers because of friction or misalignment of the damper in the g-field. Giving an impact damper characteristics of an acceleration tuned-mass damper enables the resulting device to maintain damper mass motion and effectiveness during high-g loading. Experimental results presented here verify that this self-tuning impact damper can be designed to follow an engine order line. damping rotor component resonance crossings.

Duffy, Kirsten P.↗
NASA NTRS2001

Viscosity Relaxation in Molten HgZnTe

Rotating cup measurements of the viscosity of the pseudo-binary melt, HgZnTe have shown that the isothermal liquid with zinc mole fraction 0.16 requires tens of hours of equilibration time before a steady viscous state can be achieved. Over this relaxation period, the viscosity at 790 C increases by a factor of two, while the viscosity at 810 C increases by 40%. Noting that the Group VI elements tend to polymerize when molten, we suggest that the viscosity of the melt is enhanced by the slow formation of Te atom chains. To explain the build-up of linear Te n-mers, we propose a scheme, which contains formation reactions with second order kinetics that increase the molecular weight, and decomposition reactions with first order kinetics that inactivate the chains. The resulting rate equations can be solved for the time dependence of each molecular weight fraction. Using these molecular weight fractions, we calculate the time dependence of the average molecular weight. Using the standard semi-empirical relation between polymer average molecular weight and viscosity, we then calculate the viscosity relaxation curve. By curve fitting, we find that the data imply that the rate constant for n-mer formation is much smaller than the rate constant for n-mer deactivation, suggesting that Te atoms only weakly polymerize in molten HgZnTe. The steady state toward which the melt relaxes occurs as the rate of formation of an n-mer becomes exactly balanced by the sum of the rate for its deactivation and the rate for its polymerization to form an (n+1)-mer.

Su, Ching-Hua↗
NASA NTRS1995

Inhibition of the ATPase from Halobacterium Saccharovorum by Thiol Inhibitors: Evidence for the Presence of More Than One Essential Cysteinyl Residue

The vacuolar-like ATPase from Halobacterium saccha vorum is inhibited by N-ethylmaleimide and p-chloromercudphenylsulfonate. The failure of adenine nucleotides to protect against p-chloromercuriphenyisulfonate inhibition, of p-chloromercuriphenylsulfonate to protect against N-ethylmaleimide inhibition, and the difference in the temperature dependence of inactivation infers that the enzyme contains at least two thiols that are essential for enzyme activity. CNBr cleavage of C-14-N-ethylmaleimide labeled subunit results in two radioactive peptides that locates the N-ethylmaleimide-reactive cysteinyl residue as cysteine-262 in the H. salinarium sequence.

Hochstein, Lawrence I.↗
NASA NTRS2002

Functional Characterization of G12, a Gene Required for Mitotic Progression during Gastrulation in Zebrafish

In a differential RNA display screen we have isolated a zebrafish gene, G12, for which homologs can only be found in DNA databases for vertebrates, but not invertebrates. This suggests that this is a gene required specifically in vertebrates. G12 expression is upregulated at mid-blastula transition (MBT). Morpholino inactivation of this gene by injection into 1-cell embryos results in mitotic defects and apoptosis shortly after MBT. Nuclei in morpholino treated embryos also display segregation defects. We have characterized the localization of this gene as a GFP fusion in live and fixed embryos. Overexpression of G12-GFP is non-toxic. Animals retain GFP expression for at least 7 days with no developmental defects, Interestingly in these animals G12-GFP is never detectable in blood cells though blood is present. In the deep cells of early embryos, G 12GFP is localized to nuclei and cytoskeletal elements in interphase and to the centrosome and spindle apparatus during mitosis. In the EVL, G12-GFP shows additional localization to the cell periphery, especially in mitosis. In the yolk syncytium, G12-GFP again localizes to nuclei and strongly to cytoplasmic microtubules of migrating nuclei at the YSL margin. Morpholinc, injection specifically into the YSL after cellularization blocks epiboly and nuclei of the YSL show mitotic defects while deep cells show no mitotic defects and continue to divide. Rescue experiments in which morpholino and G12-GFP RNA are co-injected indicate partial rescue by the G12-GFP. The rescue is cell autonomous; that is, regions of the embryo with higher G12-GFP expression show fewer mitotic defects. Spot 14, the human bomolog of G12, has been shown to be amplified in aggressive breast tumors. This finding, along with our functional and morphological data suggest that G12 and spot 14 are vertebrate-specific and may function either as mitotic checkpoints or as structural components of the spindle apparatus.

Reinsch, Sigrid↗
NASA NTRS2002

Magnetic Microspheres for Therapeutical Applications

Hyperthermia is a well known cancer therapy and consists of heating a tumor region to the elevated temperatures in the range of 40-45 C for an extended period of time (2-8 hours). This leads to thermal inactivation of cell regulatory and growth processes with resulting widespread necrosis, carbonization and coagulation. Moreover, heat boosts the tumor response to other treatments such as radiation, chemotherapy or immunotherapy. Of particular importance is careful control of generated heat in the treated region and keeping it localized. Higher heating, to about 56 C can lead to tissue thermo-ablation. With accurate temperature control, hyperthermia has the advantage of having minimal side effects. Several heating techniques are utilized for this purpose, such as whole body hyperthermia, radio-frequency (RF) hyperthermia, ultrasound technique, inductive microwave antenna hyperthermia, inductive needles (thermoseeds), and magnetic fluid hyperthermia (MFH).MFH offers many advantages as targeting capability by applying magnets. However, this technology still suffers significant inefficiencies due to lack of thermal control. This paper will provide a review of the topic and outline the ongoing work in this area. The main emphasis is in devising ways to overcome the technical difficulty in hyperthermia therapy of achieving a uniform therapeutic temperature over the required region of the body and holding it steady. The basic obstacle of the present heating methods are non-uniform thermal properties of the tissue. Our approach is to develop a novel class of magnetic fluids which have inherent thermoregulating properties. We have identified a few magnetic alloys which can serve as a suitable nano-particle material. The objective is to synthesize, characterize and evaluate the efficacy of TRMF for hyperthermia therapy.

Mazuruk, K.↗
NASA NTRS2003

Magnetic Microspheres and Tissue Model Studies for Therapeutical Applications

Hyperthermia is a well known cancer therapy and consists of heating a tumor region to the elevated temperatures in the range of 40-45 C for an extended period of time (2-8 hours). This leads to thermal inactivation of cell regulatory and growth processes with resulting widespread necrosis, carbonization and coagulation. Moreover, heat boosts the tumor response to other treatments such as radiation, chemotherapy or immunotherapy. Of particular importance is careful control of generated heat in the treated region and keeping it localized. Higher heating, to about 56 C can lead to tissue thermo-ablation. With accurate temperature control, hyperthermia has the advantage of having minimal side effects. Several heating techniques are utilized for this purpose, such as whole body hyperthermia, radio-frequency (RF) hyperthermia, ultrasound technique, inductive microwave antenna hyperthermia, inductive needles (thermoseeds), and magnetic fluid hyperthermia (MFH).MFH offers many advantages as targeting capability by applying magnets. However, this technology still suffers significant inefficiencies due to lack of thermal control. This paper will provide a review of the topic and outline the ongoing work in this area. The main emphasis is in devising ways to overcome the technical difficulty in hyperthermia breast therapy of achieving a uniform therapeutic temperature over the required region of the body and holding it steady for an extended period (2-3 hours). The basic shortcomings of the presently utilized heating methods stem from the non-uniform thermal properties of the tissue and the point heating characteristics of the techniques without any thermal control. Our approach is to develop a novel class of magnetic fluids, which have inherent thermoregulating properties. We have identified a few magnetic alloys which can serve as suitable nano to micron-size particle material. The objective is to synthesize, characterize and evaluate the efficacy of Thermo Regulating Magnetic Fluids (TRMF) for hyperthermia therapy. The development of a tissue model and testing the fluid dynamics of particle motion, settling, distribution in the tissue matrix and heat generation will be discussed.

Ramachandran, N.↗
NASA NTRS2004

Enzymatic Properties of an Alkaline and Chelator Resistant alpha-amylase from the Alkaliphilic Bacillus sp. Isolate L1711

An alkaliphilic amylase producing bacterium, Bacillus sp. strain L 711, was selected among 13 soda lakes isolates. When grown at pH 10.5 and 37 C, strain L711 produced multiple forms of amylases in the culture broth. One of these, BAA, was purified from the culture supernatant by QAE column chromatography and preparative native gel electrophoresis. The molecular weight of BAA was determined to be 51 kDa by denaturing gel electrophoresis. The pH optima for activity below and above 40 C were 9.5 - 10.0 and 7.0 - 7.5 respectively. BAA was stable in the pH range 6-11 and was completely inactivated at 55 C. The thermostability was not increased in the presence of Ca(2+). The enzyme was strongly inhibited by Ca(2+), Zn(2+), Mg(2+), Mn(2+), Ba(2+) and Cu(2+), whereas the presence of Na(+), Co(2+) and EDTA (10 mM) enhanced enzymatic activity. The K(sub m), and specific activity of BAA on soluble starch were 1.9 mg/ml and 18.5 U/mg respectively. The main end products of hydrolysis were maltotetraose, maltose and glucose.

Bernhardsdotter, Eva C. M. J.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Astrobiology Stew: Pinch of Microbes, Smidgen of UV, Touch of Organics, and Dash of Meteorites

The session Astrobiology Stew: Pinch of Microbes, Smidgen of UV, Touch of Organics, and Dash of Meteorites includes the following topics: 1) Investigating the Impact of UV Radiation on High-Altitude Shallow Lake Habitats, Life Diversity, and Life Survival Strategies: Clues for Mars' Past Habitability Potential? 2) An Analysis of Potential Photosynthetic Life on Mars; 3) Radiation Inactivation of Bacterial spores on Mars; 4) Hydrophobic Surfaces of Spacecraft Components Enhance the Aggregation of Microorganisms and May Lead to Higher Survival Rates of Bacteria on Mars Landers; 5) Optical Detection of Organic Chemical Biosignatures at Hydrothermal Vents; 6) Signs of Life in Meridiani Planum-What Might Opportunity See (or Miss)? 7) Isolation of PUrines and Pyrimidines from the Murchison Meteorite Using Sublimation; and 8) Relative Amino Acid Composition of CM1 Carbonaceous Chondrites.

Source record↗
NASA NTRS2004

Enzymatic Properties of an Alkaline and Chelator Resistant Proportional to alpha-Amylase from the Alkaliphilic Bacillus sp. Isolate L1711

An alkaliphilic amylase producing bacterium, Bacillus sp. strain L1711, was selected among 13 soda lakes isolates. When grown at pH 10.5 and 370 C, strain L1711 produced multiple forms of amylases in the culture broth. One of these, BAA, was purified from the culture supernatant by QAE column chromatography and preparative native gel electrophoresis. The molecular weight of BAA was determined to be 51 kDa by denaturing gel electrophoresis. The pH optima for activity below and above 40 C were 9.5-10.0 and 7.0-7.5 respectively. BAA was stable in the pH range 6-11 and was completely inactivated at 55?C. The thermostability was not increased in the presence of Ca(2+). The enzyme was strongly inhibited by Ca(2+), Zn(2+), Mg(2+), Mn(2+), Ba(2+) and Cu(2+), whereas the presence of Na(+), Co2+ and EDTA (10 mM) enhanced enzymatic activity. The K(sub m) and specific activity of BAA on soluble starch were 1.9 mg/ml and 18.5 U/mg respectively. The main end products of hydrolysis were maltotetraose, maltose and glucose .

Bernhardsdotter, Eva C. M. J.↗
NASA NTRS2003

Survival of endospores of Bacillus subtilis on spacecraft surfaces under simulated martian environments: implications for the forward contamination of Mars

Experiments were conducted in a Mars simulation chamber (MSC) to characterize the survival of endospores of Bacillus subtilis under high UV irradiation and simulated martian conditions. The MSC was used to create Mars surface environments in which pressure (8.5 mb), temperature (-80, -40, -10, or +23 degrees C), gas composition (Earth-normal N2/O2 mix, pure N2, pure CO2, or a Mars gas mix), and UV-VIS-NIR fluence rates (200-1200 nm) were maintained within tight limits. The Mars gas mix was composed of CO2 (95.3%), N2 (2.7%), Ar (1.7%), O2 (0.2%), and water vapor (0.03%). Experiments were conducted to measure the effects of pressure, gas composition, and temperature alone or in combination with Mars-normal UV-VIS-NIR light environments. Endospores of B. subtilis, were deposited on aluminum coupons as monolayers in which the average density applied to coupons was 2.47 x 10(6) bacteria per sample. Populations of B. subtilis placed on aluminum coupons and subjected to an Earth-normal temperature (23 degrees C), pressure (1013 mb), and gas mix (normal N2/O2 ratio) but illuminated with a Mars-normal UV-VIS-NIR spectrum were reduced by over 99.9% after 30 sec exposure to Mars-normal UV fluence rates. However, it required at least 15 min of Mars-normal UV exposure to reduce bacterial populations on aluminum coupons to non-recoverable levels. These results were duplicated when bacteria were exposed to Mars-normal environments of temperature (-10 degrees C), pressure (8.5 mb), gas composition (pure CO2), and UV fluence rates. In other experiments, results indicated that the gas composition of the atmosphere and the temperature of the bacterial monolayers at the time of Mars UV exposure had no effects on the survival of bacterial endospores. But Mars-normal pressures (8.5 mb) were found to reduce survival by approximately 20-35% compared to Earth-normal pressures (1013 mb). The primary implications of these results are (a) that greater than 99.9% of bacterial populations on sun-exposed surfaces of spacecraft are likely to be inactivated within a few tens of seconds to a few minutes on the surface of Mars, and (b) that within a single Mars day under clear-sky conditions bacterial populations on sun-exposed surfaces of spacecraft will be sterilized. Furthermore, these results suggest that the high UV fluence rates on the martian surface can be an important resource in minimizing the forward contamination of Mars. c2003 Elsevier Inc. All rights reserved.

Bacillus subtilis/growth & development/physiology/↗
NASA NTRS2003

Control of T lymphocyte morphology by the GTPase Rho

BACKGROUND: Rho family GTPase regulation of the actin cytoskeleton governs a variety of cell responses. In this report, we have analyzed the role of the GTPase Rho in maintenance of the T lymphocyte actin cytoskeleton. RESULTS: Inactivation of the GTPase Rho in the human T lymphocytic cell line HPB-ALL does not inhibit constitutively high adhesion to the integrin beta1 substrate fibronectin. It did however result in the aberrant extension of finger-like dendritic processes on the substrates VCAM-1, Fn, and mAb specific to beta1 integrins. Time-lapse video microscopy demonstrated that C3 induced extensions were primarily the result of an altered pseudopod elongation rather than retraction. Once the stellate pseudopodia extended, none retracted, and cells became completely immobile. Filipodial structures were absent and the dendritic-like processes in C3 treated cells were rich in filamentous actin. Immunolocalization of RhoA in untreated HPB-ALL cells spreading on fibronectin demonstrated a diffuse staining pattern within the pseudopodia. In C3 treated cells, clusters of RhoA were pronounced and localized within the altered extensions. CONCLUSIONS: GTPase Rho is actively involved in the regulation of T lymphocyte morphology and motility.

Non-NASA Center↗
NASA NTRS2000

The ultraviolet environment of Mars: biological implications past, present, and future

A radiative transfer model is used to quantitatively investigate aspects of the martian ultraviolet radiation environment, past and present. Biological action spectra for DNA inactivation and chloroplast (photosystem) inhibition are used to estimate biologically effective irradiances for the martian surface under cloudless skies. Over time Mars has probably experienced an increasingly inhospitable photobiological environment, with present instantaneous DNA weighted irradiances 3.5-fold higher than they may have been on early Mars. This is in contrast to the surface of Earth, which experienced an ozone amelioration of the photobiological environment during the Proterozoic and now has DNA weighted irradiances almost three orders of magnitude lower than early Earth. Although the present-day martian UV flux is similar to that of early Earth and thus may not be a critical limitation to life in the evolutionary context, it is a constraint to an unadapted biota and will rapidly kill spacecraft-borne microbes not covered by a martian dust layer. Microbial strategies for protection against UV radiation are considered in the light of martian photobiological calculations, past and present. Data are also presented for the effects of hypothetical planetary atmospheric manipulations on the martian UV radiation environment with estimates of the biological consequences of such manipulations.

NASA Center ARC↗
NASA NTRS1994

An initiation-promotion model of tumour prevalence from high-charge and energy radiations

A repair/misrepair kinetic model for multiple radiation-induced lesions (mutation inactivation) is coupled to a two-mutation model of initiation-promotion in tissue to provide a parametric description of tumour prevalence in the mouse Harderian gland from high-energy and charge radiations. Track-structure effects are considered using an action-cross section model. Dose-response curves are described for gamma rays and relativistic ions, and good agreement with experiment is found. The effects of nuclear fragmentation are also considered for high-energy proton and alpha-particle exposures. The model described provides a parametric description of age-dependent cancer induction for a wide range of radiation fields. Radiosensitivity parameters found in the model for an initiation mutation (sigma 0 = 7.6 x 10(-10) cm2 and D0 = 148.0 Gy) are somewhat different than previously observed for neoplastic transformation of C3H10T1/2 cell cultures (sigma 0 = 0.7 x 10(-10) cm2 and D0 = 117.0 Gy). We consider the two hypotheses that radiation acts solely as an initiator or as both initiator and promoter and make model calculations for fractionation exposures from gamma rays and relativistic Fe ions. For fractionated Fe exposures, an inverse-dose-rate effect is provided by a promotion hypothesis with an increase of 30% or more, dependent on the dose level and fractionation schedule, using a mutation rate for promotion similar to that of single-gene mutations.

NASA Discipline Radiation Health↗
NASA NTRS1995

A novel root gravitropism mutant of Arabidopsis thaliana exhibiting altered auxin physiology

A root gravitropism mutant was isolated from the DuPont Arabidopsis thaliana T-DNA insertional mutagenesis collection. This mutant has reduced root gravitropism, hence the name rgr1. Roots of rgr1 are shorter than those of wild-type, and they have reduced lateral root formation. In addition, roots of rgr1 coil clockwise on inclined agar plates, unlike wild-type roots which grow in a wavy pattern. The rgr1 mutant has increased resistance, as measured by root elongation, to exogenously applied auxins (6-fold to indole-3-acetic acid, 3-fold to 2,4-dichlorophenoxyacetic acid, and 2-fold to napthyleneacetic acid). It is also resistant to polar auxin transport inhibitors (2-fold to triiodobenzoic acid and 3- to 5-fold to napthylphthalamic acid). The rgr1 mutant does not appear to be resistant to other plant hormone classes. When grown in the presence of 10(-7) M 2,4-dichlorophenoxyacetic acid, rgr1 roots have fewer root hairs than wild type. All these rgr1 phenotypes are Mendelian recessives. Complementation tests indicate that rgr1 is not allelic to previously characterized agravitropic or auxin-resistant mutants. The rgr1 locus was mapped using visible markers to 1.4 +/- 0.6 map units from the CH1 locus at 1-65.4. The rgr1 mutation and the T-DNA cosegregate, suggesting that rgr1 was caused by insertional gene inactivation.

NASA Discipline Plant Biology↗
NASA NTRS1992

Mechanism of blue-light-induced plasma-membrane depolarization in etiolated cucumber hypocotyls

A large, transient depolarization of the plasma membrane precedes the rapid blue-light (BL)-induced growth suppression in etiolated seedlings of Cucumis sativus L. The mechanism of this voltage transient was investigated by applying inhibitors of ion channels and the plasma-membrane H(+)-ATPase, by manipulating extracellular ion concentrations, and by measuring cell input resistance and ATP levels. The depolarizing phase was not affected by Ca(2+)-channel blockers (verapamil, La3+) or by reducing extracellular free Ca2+ by treatment with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). However, these treatments did reduce the rate of repolarization, indicating an inward movement of Ca2+ is involved. No effects of the K(+)-channel blocker tetraethylammonium (TEA+) were detected. Vanadate and KCN, used to inhibit the H(+)-ATPase, reduced or completely inhibited the BL-induced depolarization. Levels of ATP increased by 11-26% after 1-2 min of BL. Input resistance of trichrome cells, measured with double-barreled microelectrodes, remained constant during the onset of the depolarization but decreased as the membrane voltage became more positive than -90 mV. The results indicate that the depolarization mechanism initially involves inactivation of the H(+)-ATPase with subsequent transient activation of one or more types of ion channels.

NASA Program Space Biology↗
NASA NTRS1994

Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts

The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 micrometer2 and 0.09 to 5.56 x 10(-3) micrometer2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(-5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

NASA Center JSC↗
NASA NTRS1985

In vivo inhibition of polyamine biosynthesis and growth in tobacco ovary tissues

Post fertilization growth of tobacco ovary tissues treated with inhibitors of polyamine (PA) biosynthesis was examined in relation to endogenous PA titers and the activities of arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17). DL-alpha-Difluoromethylornithine (DFMO) and DL-alpha-difluoromethylarginine (DFMA), specific, irreversible ("suicide") inhibitors of ODC and ADC in vitro, were used to modulate PA biosynthesis in excised flowers. ODC represented >99% of the total decarboxylase activity in tobacco ovaries. In vivo inhibition of ODC with DFMO resulted in a significant decrease in PA titers, ovary fresh weight and protein content. Simultaneous inhibition of both decarboxylases by DFMO and DFMA produced only a marginally greater depression in growth and PA titers, indicating that ODC activity is rate-limiting for PA biosynthesis in these tissues. Paradoxically, DFMA alone inhibited PA biosynthesis, not as a result of a specific inhibition of ADC, but primarily through the inactivation of ODC. In vivo inhibition of ODC by DFMA appears to result from arginase-mediated hydrolysis of this inhibitor to urea and DFMO, the suicide substrate for ODC. Putrescine conjugates in tobacco appear to function as a storage form of this amine which, upon hydrolysis, may contribute to Put homeostasis during growth.

NASA Program Space Biology↗
NASA NTRS1993

A prototype stable RNA identification cassette for monitoring plasmids of genetically engineered microorganisms

A prototype stable RNA identification cassette for monitoring genetically engineered plasmids carried by strains of Escherichia coli has been developed. The cassette consists of a Vibrio proteolyticus 5S ribosomal RNA (rRNA) gene surrounded by promoters and terminators from the rrnB operon of Escherischia coli. The identifier RNA is expressed and successfully processed so that approximately 30% of the 5S rRNA isolated from either whole cells or 70S ribosomes is of the V. proteolyticus type. Cells carrying the identifier are readily detectable by hybridization. Accurate measurements show that the identification cassette has little effect on fitness compared to a strain containing an analogous plasmid carrying wild type E. coli 5S rRNA, and the V. proteolyticus 5S rRNA gene is not inactivated after prolonged growth. These results demonstrate the feasibility of developing small standardized identification cassettes that can utilize already existing highly sensitive rRNA detection methods. Cassettes of this type could in principle be incorporated into either the engineered regions of recombinant plasmids or their hosts.

Non-NASA Center↗