Two-dimensional multiwavelength fluorescence spectra of dipicolinic acid and calcium dipicolinate

Dipicolinic acid (DPA) and the Ca2+ complex of DPA (CaDPA) are major chemical components of bacterial spores. With fluorescence being considered for the detection and identification of spores, it is important to understand the optical properties of the major components of the spores. We report in some detail on the room-temperature fluorescence excitation and emission spectra of DPA and its calcium ion complex and provide a comparison of the excitation-emission spectrum in a dry, wet paste and aqueous form. DPA solutions have weak, if any, fluorescence, with increased fluorescence when the DPA is dry. After exposure to a broad source UV light of the DPA, wet or dry, we observe a large increase in fluorescence with a maximum intensity emission peak at around 440 nm for excitation light with a wavelength of around 360 nm. There is a slight blueshift in the absorption spectra of UV-exposed DPA from the unexposed DPA solution. CaDPA in solution shows a slight fluorescence with increased fluorescence in the dry form, and a substantial increase of fluorescence was observed after UV exposure with an emission peak of around 410 nm for excitation around 305 nm. The detailed excitation-emission spectra are necessary for better interpretation of the fluorescence spectra of bacterial spores where DPA is a major chemical component.

Potentiometric sensor for dipicolinic acid

A potentiometric chemosensor for selective determination of dipicolinic acid (2,6-pyridinedicarboxylic acid, DPA) was developed based on the surface imprinting technique coupled with a nanoscale transducer: an indium tin oxide (ITO)-coated glass plate. The sensor fabrication conditions, optimal recognition condition, as well as selectivity, sensitivity, and stability of the DPA sensor have been investigated. The DPA sensor could recognize DPA from 3,5-pyridinedicarboxylic acid. Potentiometric measurements demonstrated selective detection of DPA in a concentration range of 1.5 x 10(-6) to 0.0194 M. The response time of DPA sensor for 4 x 10(-4) M DPA was 25 s. The potentiometric response of the DPA sensor to DPA is at 90% of its initial magnitude after 550 times measurement. The viability of such a modified ITO electrode in the presence of other inorganic, organic, and biological materials was probed.

A validated method for analysis of chromium picolinate in nutraceuticals by reversed phase high performance liquid chromatography

A validated high performance liquid chromatographic method was developed for the determination of chromium picolinate in pharmaceutical dosage forms. The analysis was performed at room temperature using a reversed-phase Supelcosil LC-18 (250 x 4.6 mm, 5 microm) column. The mobile phase consisted of acetonitrile:water (40:60 v/v) at a fl ow rate of 0.8 mL/min. The UV-detector was set at 264 nm. The developed method showed a good linear relationship in the concentration range from 0.125 to 12.5 microg/mL with a correlation coefficient from 0.999. The limit of detection and limit of quanti fi cation were 0.091 and 0.181 microg/mL, respectively.

Intensities of calcium dipicolinate and Bacillus subtilis spore Raman spectra excited with 244 nm light

Ultraviolet (UV) resonance Raman spectra of Bacillus subtilis endospores have been excited at 244 nm. Spectra can be interpreted in terms of contributions from calcium dipicolinate and nucleic acid components. Differences between spectra of spores and vegetative cells are very large and are due to the dominance of the dipicolinate features in the spore spectra. Because the DNA and RNA composition of B. subtilis spores is known and because the cross-sections of Raman bands belonging to DNA and RNA bases are known, it is possible to calculate resonance Raman spectral cross-sections for the spore Raman peaks associated with the nucleic acids. The cross-sections of peaks associated with calcium dipicolinate have been measured from aqueous solutions. Cross-section values of the dominant 1017 cm(-1) calcium dipicolinate peak measured from the Bacillus spores have been shown to be consistent with a calcium dipicolinate composition of ten percent or less by weight in the spores. It is suggested that spectral cross-sections of endospores excited at 244 nm can be estimated to be the sum of the cross-sections of the calcium dipicolinate, DNA, and RNA components of the spore. It appears that the peaks due to DNA and RNA can be used as an internal standard in the calculation of spore Raman peak cross-sections, and potentially the amount of calcium dipicolinate in spores. It is estimated on the basis of known nucleic acid base cross-sections that the most intense Raman band of the Bacillus subtilis spore spectra has a cross-section of no more than 4 x 10(-18) cm(2)/mol-sr.

Mid-ultraviolet light-emitting diode detects dipicolinic acid

Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA (lambda(max) doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.

Structural characterization of 5,6-dichlorotetradecanoic acid, an isolated metabolite of 9,10-dichlorooctadecanoic acid, by studying picolinyl esters, pyrrolidides and methyl esters with electron ionization mass spectrometry

A method is presented for identification of positional isomers of dichlorinated fatty acids, based on derivatization to picolinyl esters prior to gas chromatographic/mass spectrometric analysis in the electron ionization mode. The mass spectra of the picolinyl esters showed structure-specific fragmentation patterns. By using the picolinyl ester, 5,6-dichlorotetradecanoic acid was identified as a metabolite from a cell-culture medium obtained by culturing human cell lines in media supplemented with threo-9,10-dichlorooctadecanoic acid. This indicates that dichlorinated fatty acids are degraded by beta-oxidation. It is also possible to locate tentatively the position of chlorine atoms in 5,6-dichlorotetradecanoic acid as its methyl ester or pyrrolidide.

Toward understanding the ionization of biomarkers from micrometer particles by bio-aerosol mass spectrometry

The appearance of informative signals in the mass spectra of laser-ablated bio-aerosol particles depends on the effective ionization probabilities (EIP) of individual components during the laser ionization process. This study investigates how bio-aerosol chemical composition governs the EIP values of specific components and the overall features of the spectra from the bio-aerosol mass spectrometry (BAMS). EIP values were determined for a series of amino acid, dipicolinic acid, and peptide aerosol particles to determine what chemical features aid in ionization. The spectra of individual amino acids and dipicolinic acid, as well as mixtures, were examined for extent of fragmentation and the presence of molecular ion dimers, which are indicative of ionization conditions. Standard mixtures yielded information with respect to the significance of secondary ion plume reactions on observed spectra. A greater understanding of how these parameters affect EIP and spectra characteristics of bio-aerosols will aid in the intelligent selection of viable future biomarkers for the identification of bio-terrorism agents.

Steady-State and Frequency-Domain Lifetime Measurements of an Activated Molecular Imprinted Polymer Imprinted to Dipicolinic Acid

We recently demonstrated the synthesis and fluorescence activity associated with an optical detector incorporating a molecular imprinted polymer (MIP). Steady-state and time-resolved (lifetime) fluorescence measurements were used to characterize the binding activity associated with MIP microparticles imprinted to dipicolinic acid (DPA). DPA is a unique biomarker associated with the sporulation phase of endospore-forming bacteria. Vinylic monomers were polymerized in a dimethylformamide solution containing DPA as a template. The resulting MIP was then pulverized and sorted into small microscale particles. Tests were conducted on replicate samples of biologically active cultures representing both vegetative stationary phase and sporulation phase of Bacillus subtilis in standard media. Samplers were adapted incorporating the MIP particles within a dialyzer cartridge (500 MW). The permeability of the dialyzer membrane permitted diffusion of lighter molecular weight constituents from microbial media effluents to enter the dialyzer chamber and come in contact with the MIP. Results showed dramatic (10-fold over background) steady-state fluorescence changes (as a function of excitation, emission and intensity) for samples associated with high endospore biomass (DPA), and a frequency-domain lifetime of 5.3 ns for the MIP-DPA complex.

Mechanisms of killing of Bacillus subtilis spores by Decon and OxoneTM, two general decontaminants for biological agents

AIMS

To determine the mechanisms of Bacillus subtilis spore killing by and resistance to the general biological decontamination agents, Decon and Oxone.

METHODS AND RESULTS

Spores of B. subtilis treated with Decon or Oxone did not accumulate DNA damage and were not mutagenized. Spore killing by these agents was increased if spores were decoated. Spores prepared at higher temperatures were more resistant to these agents, consistent with a major role for spore coats in this resistance. Neither Decon nor Oxone released the spore core's depot of dipicolinic acid (DPA), but Decon- and Oxone-treated spores more readily released DPA upon a subsequent normally sublethal heat treatment. Decon- and Oxone-killed spores initiated germination with dodecylamine more rapidly than untreated spores, but could not complete germination triggered by nutrients or Ca(2+)-DPA and did not degrade their peptidoglycan cortex. However, lysozyme treatment did not recover these spores.

CONCLUSIONS

Decon and Oxone do not kill B. subtilis spores by DNA damage, and a major factor in spore resistance to these agents is the spore coat. Spore killing by both agents renders spores defective in germination, possibly because of damage to the inner membrane of spore.

SIGNIFICANCE AND IMPACT OF STUDY

These results provide information on the mechanisms of the killing of bacterial spores by Decon and Oxone.

Mechanisms of killing of Bacillus subtilis spores by hypochlorite and chlorine dioxide

AIMS

To determine the mechanisms of Bacillus subtilis spore killing by hypochlorite and chlorine dioxide, and its resistance against them.

METHODS AND RESULTS

Spores of B. subtilis treated with hypochlorite or chlorine dioxide did not accumulate damage to their DNA, as spores with or without the two major DNA protective alpha/beta-type small, acid soluble spore proteins exhibited similar sensitivity to these chemicals; these agents also did not cause spore mutagenesis and their efficacy in spore killing was not increased by the absence of a major DNA repair pathway. Spore killing by these two chemicals was greatly increased if spores were first chemically decoated or if spores carried a mutation in a gene encoding a protein essential for assembly of many spore coat proteins. Spores prepared at a higher temperature were also much more resistant to these agents. Neither hypochlorite nor chlorine dioxide treatment caused release of the spore core's large depot of dipicolinic acid (DPA), but hypochlorite- and chlorine dioxide-treated spores much more readily released DPA upon a subsequent normally sub-lethal heat treatment than did untreated spores. Hypochlorite-killed spores could not initiate the germination process with either nutrients or a 1 : 1 chelate of Ca2+-DPA, and these spores could not be recovered by lysozyme treatment. Chlorine dioxide-treated spores also did not germinate with Ca2+-DPA and could not be recovered by lysozyme treatment, but did germinate with nutrients. However, while germinated chlorine dioxide-killed spores released DPA and degraded their peptidoglycan cortex, they did not initiate metabolism and many of these germinated spores were dead as determined by a viability stain that discriminates live cells from dead ones on the basis of their permeability properties.

CONCLUSIONS

Hypochlorite and chlorine dioxide do not kill B. subtilis spores by DNA damage, and a major factor in spore resistance to these agents appears to be the spore coat. Spore killing by hypochlorite appears to render spores defective in germination, possibly because of severe damage to the spore's inner membrane. While chlorine dioxide-killed spores can undergo the initial steps in spore germination, these germinated spores can go no further in this process probably because of some type of membrane damage.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results provide information on the mechanisms of the killing of bacterial spores by hypochlorite and chlorine dioxide.

Qualitative and quantitative analysis of three amino acid derivatives of anticonvulsant activity

Qualitative and quantitative methods of analysis of three new amino-acid derivatives potential anticonvulsants of low neurotoxicity: picolinic acid benzylamide (1), nicotinic acid benzylamide (2) and isonicotinic acid benzylamide (3) were developed. Qualitative analysis includes characteristic reactions, chromatographic (TLC) investigations, IR and UV spectra interpretation. The quantitative analysis involves spectophotometric, chromatographic (HPLC) and acidimetric methods.

Native fluorescence and excitation spectroscopic changes in Bacillus subtilis and Staphylococcus aureus bacteria subjected to conditions of starvation

Fluorescence emission and excitation spectra were measured over a 7-day period for Bacillus subtilis (Bs), a spore-forming, and Staphylococcus aureus (Sa), a nonspore-forming bacteria subjected to conditions of starvation. Initially, the Bs fluorescence was predominantly due to the amino acid tryptophan. Later, a fluorescence band with an emission peak at 410 nm and excitation peak at 345 m, from dipicolinic acid, appeared. Dipicolinic acid is produced during spore formation and serves as a spectral signature for detection of spores. The intensity of the 410-nm band continued to increase over the next 3 days. The Sa fluorescence was predominantly from tryptophan and did not change over time. In 6 of the 17 Bs specimens studied, an additional band appeared with a weak emission peak at 460 cm and excitation peaks at 250, 270, and 400 nm. The addition of beta-hydroxybutyric acid to the Bs or the Sa cultures resulted in a two-order of magnitude increase in the 460-nm emission. The addition of Fe2+ quenched the 460 emission, indicating that a source of the 460-nm emission was a siderophore produced by the bacteria. We demonstrate that optical spectroscopy-based instrumentation can detect bacterial spores in real time.

Determination of spore concentration in Bacillus thuringiensis through the analysis of dipicolinate by capillary zone electrophoresis

A new capillary zone electrophoresis (CZE) method for the analysis of dipicolinic acid, a specific component found in spores but not in vegetative cells, was used to determine spore concentration in Bacillus thuringiensis according to the relationship between the spore concentration and the content of dipicolinate. The quantitative relationship was established by using purified spores. Electrolyte conditions that affected the separation efficiency of dipicolinate and the reproducibility were investigated. With 10 mM phosphate, 10 mM ethylenediaminetetraacetic acid and 0.25 mM tetradecyltrimethylammonium bromide at pH 6.2 as the carrier electrolyte, dipicolinate can be determined within 8 min at an applied voltage of -25 kV (anode at detector) and a capillary temperature of 25 degrees C. The method has a high separation efficiency with which the number of theoretical plates is above 300,000 plates m(-1). The relative standard deviations for migration time and peak area are less than 0.5% and 2.0%, respectively. The detection limit for dipicolinate was 10 ng ml(-1), which corresponds to 7.2 x 10(5) spores ml(-1). The method was used to determine spores in fermentation broths, and the results obtained agreed well with the values obtained by plate counting.

ECNI GC-MS analysis of picolinic and quinolinic acids and their amides in human plasma, CSF, and brain tissue

To study the complex inter-relationships between inflammatory and apoptotic responses and the kynurenine pathway, we have utilized electron-capture negative ion mass spectrometry to develop trace analyses to concurrently quantify nicotinic acid (NIC), picolinic acid (PIC) and quinolinic acid (QUIN) in biological samples. We have shown that NIC and its amide nicotinamide (NAM) can be separately quantified by analyzing samples pre- and post-acid hydrolysis. We have now examined human plasma, CSF and brain tissue samples for the presence of putative picolinamide (PAM) and quinolinamide (QAM) by comparing PIC and QUIN concentrations pre- and post- gas phase hydrolysis. We report for the first time that, with respect to the free acids, relatively high concentrations of the amides (or, at least, hydrolysable precursors of the acids) are present in plasma and brain with marked relative increases in CSF. In normal control subjects (n=22) pre-hydrolysis plasma levels (+/- sem) of PIC and QUIN were 0.299 +/- 0.034 and 0.47 +/- 0.047 micromol/L respectively. Following hydrolysis the concentrations rose more than 4-fold to 1.33 +/- 0.115 and 2.2 +/- 0.27 micromol/L respectively. In CSF samples from patients with no sign of brain injury or pathology (n=10) pre-hydrolysis concentrations of PIC and QUIN were 0.017 +/- 0.005 and 0.018 +/- 0.006 micromol/L, respectively, which rose to 0.30 +/- 0.06 and 0.06 +/- 0.008 micromol/L respectively, after hydrolysis. In CSF samples from patients with a range of brain oedema or injury (eg subdural haemorrage, motor vehicle accident) (n=6) pre-hydrolysis concentrations of PIC and QUIN were 0.053 +/- 0.03 and 0.29 +/- 0.12 micromol/L, respectively. Following hydrolysis the concentrations were markedly increased to 6.06 +/- 1.5 and 0.94 +/- 0.63 micromol/L, respectively. The present investigation has shown for the first time that PAM and QAM are present endogenously with PAM being relatively higher than QAM, especially in CSF samples from patients with presumed brain inflammation. The site and mechanism of amidation of PIC and QUIN needs investigation.

GC/MS determination of fatty acid picolinyl esters by direct curie-point pyrolysis of whole bacterial cells

A single-step method suitable for cellular fatty acid derivatization to picolinyl esters with the use of a pyrolyzer as a thermochemical micro-reactor was developed for whole bacterial cells. This reduced the preparation time from several hours to less than two minutes. In addition, the minimal bacterial mass required for analysis was reduced from several milligrams to micrograms. The profiling of cellular fatty acids of gram-positive and gram-negative bacteria was achieved using three derivatization methods: preparation of methyl esters, beta-picolinyl esters by Harvey's method and a new method based on pyrolytic derivatization to beta-picolinyl esters. It was shown that there are great similarities between profiles of bacterial fatty acids determined by the pyrolytic derivatization method and traditional preparation methods of picolinyl and methyl esters prior to GC analysis. Results obtained by application of the new technique have immense diagnostic value due to vast similarities between profiles of fatty acids derivatized to either picolinyl and methyl esters. Although the latter are referred to in the literature most often, mass spectra of picolinyl esters contain fragment ions that provide structural information about the chain branching, position of unsaturation, and other substituents.

Concurrent quantification of quinolinic, picolinic, and nicotinic acids using electron-capture negative-ion gas chromatography-mass spectrometry

Quinolinic, picolinic, and nicotinic acids and nicotinamide are end products of the kynurenine pathway from l-tryptophan and are intermediates in the biosynthesis of nicotinamide adenine dinucleotide. These compounds are involved in complex interrelationships with inflammatory and apoptotic responses associated with neuronal cell damage and death in the central nervous system. To facilitate the study of these compounds, we have utilized gas chromatography-mass spectrometry in electron capture negative ionization mode for their concurrent trace quantification in a single sample. Deuterium-labeled quinolinic, picolinic, and nicotinic acids were used as internal standards and the compounds were converted to their hexafluoroisopropyl esters prior to chromatography. Nicotinamide was readily quantified after conversion to nicotinic acid using gas-phase hydrolysis-a process which did not affect the deuterated internal standards. The on-column limit of quantification was less than 1 fmol for each of the analytes and calibration curves were linear. A packed column liner was used in the gas chromatograph inlet to effectively eliminate sample interference effects in the analysis of trace (femtomolar) levels of quinolinic acid. The method enables rapid and specific concurrent quantification of quinolinic, picolinic, and nicotinic acids in tissue extracts and physiological and culture media.

New high-performance liquid chromatographic method for the detection of picolinic acid in biological fluids

A HPLC method is described to quantify picolinic acid in milk, blood serum and tissue culture supernatant. The method requires very little sample preparation because acid precipitation allows total recovery of picolinic acid. High specificity and sensitivity were obtained using ion-pair chromatography on a C18 reversed-phase column with tetrabutylammonium hydrogen sulfate as ion pairing reagent. We describe the conditions for the automated testing of multiple samples and for the detection of L-tryptophan and L-kynurenine together with picolinic acid. This system will be utilized to elucidate the relationship between picolinic acid production and human disease. Furthermore, we provide the first evidence of picolinic acid in human blood serum.

Electron monochromator mass spectrometry for the analysis of whole bacteria and bacterial spores

Spores from a variety of Bacillus species were analyzed with direct probe mass spectrometry using an electron monochromator to select electrons of distinct energies for ionization. Electron energies were chosen to match the electron capture energies of taxonomically important compounds such as dipicolinic acid and fatty acids. Previous negative ion interferences were not observed when the monochromator was used, and the signal-to-noise ratio of targeted compounds was significantly enhanced using this approach. To demonstrate the selectivity of the technique, the monochromator was swept over a range of electron energies while monitoring the masses of compounds with known electron capture energies. Scanning the monochromator while the mass spectrometer was operated in single-ion mode enabled dipicolinic acid to be detected in 10(5) spores. The results presented here demonstrate the utility of the electron monochromator for selectively ionizing compounds directly in bacteria and bacterial spores.

Detection of the dipicolinic acid biomarker in Bacillus spores using Curie-point pyrolysis mass spectrometry and Fourier transform infrared spectroscopy

Thirty-six strains of aerobic endospore-forming bacteria confirmed by polyphasic taxonomic methods to belong to Bacillus amyloliquefaciens, Bacillus cereus, Bacillus licheniformis, Bacillus megaterium, Bacillus subtilis (including Bacillus niger and Bacillus globigii), Bacillus sphaericus, and Brevi laterosporus were grown axenically on nutrient agar, and vegetative and sporulated biomasses were analyzed by Curie-point pyrolysis mass spectrometry (PyMS) and diffuse reflectance-absorbance Fourier-transform infrared spectroscopy (FT-IR). Chemometric methods based on rule induction and genetic programming were used to determine the physiological state (vegetative cells or spores) correctly, and these methods produced mathematical rules which could be simply interpreted in biochemical terms. For PyMS it was found that m/z 105 was characteristic and is a pyridine ketonium ion (C6H3ON+) obtained from the pyrolysis of dipicolinic acid (pyridine-2,6-dicarboxylic acid; DPA), a substance found in spores but not in vegetative cells; this was confirmed using pyrolysis-gas chromatography/mass spectrometry. In addition, a pyridine ring vibration at 1447-1439 cm-1 from DPA was found to be highly characteristic of spores in FT-IR analysis. Thus, although the original data sets recorded hundreds of spectral variables from whole cells simultaneously, a simple biomarker can be used for the rapid and unequivocal detection of spores of these organisms.

Dipicolinic acid (DPA) assay revisited and appraised for spore detection

Delayed gate fluorescence detection of dipicolinic acid (DPA), a universal and specific component of bacterial spores, has been appraised for use in a rapid analytical method for the detection of low concentrations of bacterial spores. DPA was assayed by fluorimetric detection of its chelates with lanthanide metals. The influence of the choice and concentration of lanthanide and buffer ions on the fluorescence assay was studied as well as the effects of pH and temperature. The optimal system quantified the fluorescence of terbium monodipicolinate in a solution of 10 microM terbium chloride buffered with 1 M sodium acetate, pH 5.6 and had a detection limit of 2 nM DPA. This assay allowed the first real-time monitoring of the germination of bacterial spores by continuously quantifying exuded DPA. A detection limit of 10(4) Bacillus subtilis spores ml-1 was reached, representing a substantial improvement over previous rapid tests.

Real-time monitoring of Bacillus subtilis endospore components by attenuated total reflection Fourier-transform infrared spectroscopy during germination

Chemical changes of particular Bacillus subtilis spore components were monitored by attenuated total reflection Fourier-transform infrared spectroscopy (ATR/FTIR) during spore germination on a ZnSe internal reflection element. Within minutes of the initiation of spore germination, significant changes in the amount of calcium dipicolinate (DPA-Ca) and proteins were noted in the wild-type strain. The changes in a germination mutant (strain 1G9, gerD) were similar to those in the wild-type strain, but the rates of change were slower. The changes in another germination mutant (strain 1G7, gerA) were very different from those in the first two strains: germination was slow and incomplete, and proteins and DPA-Ca remained unaltered throughout the course of the germination study. This technique thus offers a sensitive and non-destructive method for real-time monitoring of various cellular components during spore germination.

Direct mass spectrometric analysis of Bacillus spores

Spores from the Bacillus species, B. cereus, B. anthracis, B. thuringensis, B. lichenformis, B. globigi, and B. subtilis, were examined by direct probe mass spectrometry using electron ionization (EI) and positive and negative chemical ionization (CI). Molecular ions from free fatty acids and nucleic acids were observed in the 70eV spectra as were fragments from glycerides. Spectra obtained with isobutane positive chemical ionization (CI(+)) were dominated by ions associated with pyranose compounds such as N-acetylglucosamine (NAG). Unlike the positive ion spectra, the negative ion spectra of the spores were very simple and contained few peaks. The M(-.) ion from dipicolinic acid (DPA) was the base peak in the negative ion spectra of all spore species except those from B. lichenformis. The negative ion of DPA produced such a strong signal that 10(8) colony forming units (CFUs) of B. cereus spores could be detected directly in 0.5 g of ground rice. Principal component analysis (PCA) of the spectra revealed that only CI(+) spectra contained differences that could be used to identify the spectra by species. Differentiation of the CI(+) spectra by PCA was attributed to variances in the peaks associated with the bacterial polymer poly(3-hydroxybutyrate) (PHB) and NAG. Similar differences in PHB and NAG peaks were detected in the CI(+) spectra of a suite of vegetative Bacillus stains grown with various media.