Phenotypic biomonitoring using multivariate flow cytometric analysis of multi-stained microorganisms

A new method for monitoring phenotypic profiles of pure cultures and complex microbial communities was evaluated. The approach was to stain microorganisms with a battery of fluorescent dyes prior to flow cytometry analysis (FCM) and to analyse the data using multivariate methods, including principal component analysis and partial least squares. The FCM method was quantitatively evaluated using different mixtures of pure cultures as well as microbial communities. The results showed that the method could quantitatively and reproducibly resolve both populations and communities of microorganisms with 5% abundance in a diverse microbial background. The feasibility of monitoring complex microbial communities over time during the biodegradation of naphthalene using the FCM method was demonstrated. The biodegradation of naphthalene occurred to differing extents in microcosms representing three different types of aromatic-contaminated groundwater and a sample of bio-basin water. The FCM method distinguished each of these four microbial communities. The phenotypic profiles were compared with genotypic profiles generated by random-amplified polymorphic DNA analysis. The genotypic profiles of the microbial communities described only the microbial composition, and not their functional change, whereas the phenotypic profiles seemed to contain information on both the composition and the functional change of the microorganisms. Furthermore, event analysis of the FCM data showed that microbial communities with initially differing compositions could converge towards a similar composition if they had a capacity for high levels of degradation, whereas microbial communities with similar initial compositions could diverge if they differed in biodegrading ability.

Intramuscular pressure of the infra- and supraspinatus muscles in relation to hand load and arm posture

In work engaging the upper extremities, the musculoskeletal system of the shoulder is sometimes exposed to prolonged excessive load, leading to musculoskeletal disorders of the shoulder. One way of reducing work-related shoulder disorders is to establish guidelines for working postures. The purpose of this study was to identify harmful working positions, by performing a comprehensive survey of the intramuscular pressure (IMP) in the infra- and supraspinatus muscles in relation to different arm positions and external loads. Ten healthy males participated, and the IMP in the infra- and supraspinatus muscles was studied in a total of 112 combinations of arm positions and hand loads at levels that occur frequently in industrial work. High-precision spatial recordings were accomplished with a three-dimensional motion-analysis system, and the IMP was measured using the microcapillary infusion technique. The mean IMP of the infraspinatus muscle as well as that of the supraspinatus muscle increased continuously from a resting pressure at 0 degrees of upper arm elevation to a maximal pressure at 90 degrees of upper arm elevation, for all elevation planes. The mean IMP of the supraspinatus muscle appeared to be more dependent upon the elevation plane and less dependent upon the hand load, compared to the infraspinatus muscle. Even during only moderate arm elevation, the mean IMP of the infra- and supraspinatus muscles, presented here in polar diagrams, had already exceeded the levels of reduced recovery from local muscle fatigue and blood flow impairment. The elevation angle and the hand load primarily influence the development of IMP in the infra- and supraspinatus muscles.

Influence of TNT transformation on microbial community structure in four different lake microcosms

After World War II, large amounts of obsolete ammunition were dumped in various lakes in Sweden. Trinitrotoluene, TNT, was one of the main components of the dumped explosives. In this study, four different lake microcosms originating from lakes where relatively large amounts of ammunition were dumped were used to mimic the effect of TNT release on the natural microbial community. Increased microbial growth was found in lake microcosms amended with TNT. However, negligible mineralization of TNT was detected, suggesting that TNT was not utilized as a carbon source, but as a nitrogen source. Random amplified polymorphic DNA (RAPD) analysis indicated that the TNT induced no significant differences in microbial community composition and therefore, no major changes in natural selection, despite the increased microbial growth in the presence of the compound. More than 95% of the added TNT bound irreversibly to the sediments, possibly as a result of microbial transformation to reactive metabolites that subsequently bound covalently to components of the sediment. The results, taken together, suggest that no permanent change in the microbial ecology occurred as a result of the TNT amendment. This was probably due partly to the transient exposure of the microbial communities to the TNT before it became irreversibly bound to the sediment, and partly to the fact that TNT was not a primary growth substrate that strongly affects natural selection.

Structure of a Natural Microbial Community in a Nitroaromatic Contaminated Groundwater Is Altered during Biodegradation of Extrinsic, but Not Intrinsic Substrates

A BSTRACTThis study demonstrates microbial community changes over time in a nitroaromatic-contaminated groundwater upon amendment with hydrocarbons previously unknown to the microbial community (extrinsic) and hydrocarbons previously known to the microbial community (intrinsic). Sealed flasks, shaken and incubated at 25 degrees C, containing contaminated groundwater and salts were amended twice with extrinsic hydrocarbons including phenol, benzoic acid, and naphthalene, and intrinsic hydrocarbons including 2,4-dinitrotoluene (2,4-DNT) and para-nitrotoluene ( p-NT). Microbial growth, biodegradation, and community structure changes measured by random amplified polymorphic DNA (RAPD) and quantitative PCR (qPCR) targeting catechol-2,3-dioxygenase (C23O) genes were monitored over time. All amended substrates were biodegraded after both substrate amendments except for 2,4-DNT, which was only partially degraded after the second amendment. Unique microbial communities were developed in flasks amended with phenol, benzoic acid, and naphthalene. However, in the flasks amended with intrinsic hydrocarbons the microbial community remained similar to the unamended control flasks. The relative amount of C23O genes detected by qPCR correlated with the biodegradation of phenol and naphthalene but not with 2,4-DNT. The results showed that a selection for microorganisms capable of catabolizing extrinsic hydrocarbons naturally and initially present in the nitroaromatic-contaminated groundwater occurred. However, growth-linked biodegradation of added intrinsic hydrocarbons was not selective.

Intragastric movement assessment by measuring magnetic field decay of magnetised tracer particles in a solid meal

The aim of the study is to evaluate and further develop a non-invasive method for the measurement of intragastric movements. Ferrimagnetic particles (gamma-Fe2O3) are ingested within a standard test meal (pancakes), and given a permanent magnetisation by an applied homogeneous magnetic field. Magnetic measurements are performed outside the stomach, using fluxgate magnetometers anterior and posterior, in seven periods of 12 minutes each. Any movements caused by grinding and mixing in the ingesta would result in a misalignment of the magnetic moments, and hence in a decay of the external magnetic field. Twelve healthy male volunteers, aged 26.7 +/- 2.7 years (mean +/- SD), are studied. After an initial phase of low and almost linear flux density decay (32 +/- 19%, from minute 10 to minute 22 postprandially), the mean rotation and decay gradually increases (67 +/- 21%, from minute 100 to 112), and the decay becomes bi-exponential. It is hypothesised that the bi-exponential nature of the decay corresponds to the relative fractions, solid and semifluid, of gastric content. The decay curves often show superimposed 3 cycles min-1 variations, which correlate well with the basic electrical rhythm of the stomach measured by electrogastrography (EGG). It is concluded that these variations are induced by gastric contractions.

Comparative analysis of PCR versus culture for diagnosis of ulceroglandular tularemia

PCR and culture were comparatively evaluated for their abilities to demonstrate Francisella tularensis in wound specimens from tularemia patients during an outbreak in Sweden in 1998. For transport of the specimens used for PCR, a buffer solution containing a nuclease inhibitor was used, and for transport of the specimens used for culture, a commercial transport system was selected after experimental comparison of various systems. Of 40 patients with culture- and/or serology-verified ulceroglandular tularemia, PCR detected F. tularensis DNA in 30 (75%) patients, whereas culture detected bacterial growth in 25 (62%) patients. Compared to data from a previous study, the present inclusion of a nuclease inhibitor in the transport medium did not improve the sensitivity of the PCR, whereas the sensitivity of the culture procedure was significantly increased by selection of the system used for transport. Among eight patients with clinically suspected tularemia but with negative serology and culture, specimens from four patients showed detectable DNA. In three of these patients the diagnosis was verified by the demonstration of an F. tularensis-specific T-cell response in vitro. In conclusion, PCR was more sensitive than culture for demonstration of F. tularensis in wound specimens. Besides, we showed that tularemia may proceed without development of serum antibodies, and in these patients, PCR may be of special importance for verification of the diagnosis.

Paraplegia after thoracotomy--not caused by the epidural catheter

BACKGROUND

Paraplegia and peripheral nerve injuries may arise after general anaesthesia from many causes but are easily ascribed to central block if the latter has been used.

CASE REPORT

A 56-yr-old woman, with Bechterev disease but otherwise healthy, was operated with left-sided thoracotomy to remove a tumour in the left lower lobe. She had an epidural catheter inserted in the mid-thoracic area before general anaesthesia was started. Bupivacaine 0.5% 5 ml was injected once and the infusion of bupivacaine 0.1% with 2 micrograms/ml fentanyl and 2 micrograms/ml adrenaline (5 ml/h) started at the end of surgery. The patient woke up with total paralysis in the lower limb and sensory analgesia at the level of T8, which remained unchanged at several observations. Laminectomy, performed 17 h after the primary operation, showed a large piece of a haemostatic sponge (Surgicel) compressing the spinal cord, which was then decompressed but the motor and sensory deficit remained virtually unchanged both then and a year later.

CONCLUSIONS

This case shows--once again--that although central blocks may cause serious neurological complications and paraplegia, other causes are possible and have to be considered. However, all patients with an epidural catheter must be monitored for early signs and symptoms of an intraspinal process and the appropriate treatment has to be instituted instantly.

Recruitment of low threshold motor-units in the trapezius muscle in different static arm positions

A prevailing hypothesis for development of myalgia symptoms in the trapezius muscle is based on observations that in stereotypic activation of muscle the same low-threshold motor-units are the first ones to be recruited, and that these units are active throughout the contraction, until total relaxation. The theory suggests that these units are the first ones in monotonous repetitive work to be subject to degenerative processes, causing pain. The present project was undertaken to evaluate to what extent recruitment of motor-units in the trapezius muscle is position-specific, i.e. if there are motor-units that are recruited over a wide range of arm postures. Fine wire electrode pairs, inserted 2 cm lateral to the midpoint between the acromion and the C7 spinous processus, were used for signal acquisition. Methods for decomposition of the interference patterns were developed, allowing identification of single motor-units in signals registered in different arm positions. Voluntary recruitment of motor-units in the descending portion of the trapezius muscle was studied in 24 different arm positions (0-90 degrees shoulder flexion, 0-45 degrees humeral abduction, and 45-135 degrees elbow flexion) in three subjects. The results showed that the wire electrode technique and the signal processing algorithm employed allowed motor-unit identification in non-isometric conditions. It was found that low threshold motor-units in the trapezius muscle, active over a wide range of arm positions, could be identified in all three subjects. We refer to those as Cinderella, or C, units. These results support the research hypothesis addressed.

Comparison of multipole and mean value methods to quantify dust in human lungs: simulating the magnetopneumography procedure

Magnetopneumography (MPG) can quantify the retention of magnetisable particles in the lung acquired, for instance, in welding work. MPG is non-invasive and is used in occupational health, industrial hygiene and lung physiology. Following a brief magnetisation, the remanent magnetic field is mapped with magnetometers outside the thorax. There is no unique analytical inverse solution to this class of magnetostatic problem, and various inverse methods have been proposed. In the present study, the influence of variations in size and shape of the lungs and chest, magnetic measurement noise, positional noise and spatial dust distribution are investigated in five inverse methods. The mean value of the field map, calibrated against a lung phantom, is the commonly used method. Lung and chest size influence the mean value method solutions strongly. Correction for chest size reduces these errors, but bias errors and sensitivity to the deposition pattern remains a problem. A multipolar expansion, including dipolar, quadrupolar and octopolar moments, yields best results overall, provided the single-to-noise ratio is sufficient. This inverse solution is unbiased, requires no calibration with phantom lung models and serves to minimise errors due to inter-individual differences in anatomy and to inhomogeneous retention of inhaled dust.

Gastric emptying of solids measured by means of magnetised iron oxide powder

The aim of this study was to develop a radiation-free method to measure gastric emptying. Such a method would be useful e.g. for patients who need repeated measurements and in pregnancy. Ferrimagnetic particles (gamma-Fe2O3), ingested within a solid test meal (pancakes), were magnetised by an applied magnetic field. After magnetisation, the remanent magnetic field was measured with fluxgate magnetometers outside the stomach (anterior and posterior). The intragastric contents was estimated from the strength of the remanent field. The procedure was repeated 18 times over a period of up to 2 h postprandially. The test meal was chosen to correspond to a radiolabelled test meal that had previously been used in a scintigraphic study with (other) healthy persons. In vivo measurements were carried out on 16 healthy male volunteers. The estimated retained magnetic tracer in the stomach after the 2 h measurement time was 31 +/- 12% (mean +/- SD) and the lag phase time was 31 +/- 11 min. The corresponding scintigraphic curve (from the previous study) from 16 males showed 40 +/- 14% retained isotope after 2 h. The early part of the mean emptying curve decreased slightly faster than the corresponding scintigraphic one, but the similarity of the two seems promising enough for further development of the present method.

The two beta-lactamase genes of Streptomyces cacaoi, blaL and blaU, are under the control of the same regulatory system

The production of beta-lactamase in Streptomyces cacaoi, which contains two beta-lactamase-encoding genes, blaL and blaU, is inducible by beta-lactam compounds. The two genes have been cloned independently in S. lividans TK24, a beta-lactamase-negative species. The blaU clone did not respond to the presence of beta-lactams, whereas the blaL clone appeared to be inducible in S. lividans. The latter clone contains two open reading frames, blaA and blaB, located just upstream of but transcribed divergently from blaL, which were shown to be required for the production as well as the induction of BlaL. The deduced BlaA protein belongs to the LysR family of transcription regulators. In order to examine the role of BlaA in regulation, we here report on over-expression of a GST-BlaA fusion protein in Escherichia coli and its use for antibody preparation. The GST-BlaA fusion protein was partially purified and bandshift assays showed that it bound the 197-bp blaL-blaA intergenic region. The BlaA DNA binding-site was further restricted to a 30-bp sequence containing a T-N11-A motif, a characteristic of LysR-type promoters. Another T-N11-A motif upstream of the blaU gene was also shown to bind BlaA. The affinities of these two T-N11-A motifs in BlaA binding were comparable. A plasmid bearing the blaU structural gene and the blaA-blaB regulatory region was constructed and shown to confer on an S. lividans host the capacity to produce inducible beta-lactamase. It can thus be concluded that the S. cacaoi blaL and blaU genes are controlled by the same regulatory system.

DNA recovery and PCR quantification of catechol 2,3-dioxygenase genes from different soil types

With the objective of monitoring xenobiotic degrading bacteria in soil, a method for rapid extraction of DNA from soil, amenable to amplification by PCR, was developed. The method was based on lysis by freeze-thawing and subsequent addition of sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide and proteinase K. The extraction method required 2 h and was tested on six different soils differing in organic content, water holding capacity and pH, including ones from which DNA extraction is difficult. DNA yields from the soils ranged from 6.1 to 54.0 micrograms of DNA per g soil. The efficiency and reproducibility of the DNA extraction method were evaluated by competitive PCR. The organic content in the soils was a major factor affecting the amount of obtained DNA amenable for amplification by PCR. A PCR primer-pair was designed on the basis of the known nucleotide sequences of several catechol 2,3-dioxygenase genes. The specificity of the primer-pair was demonstrated on different sequenced catechol 2,3-dioxygenase genes and on site-specific bacterial isolates from polycyclic aromatic hydrocarbon (PAH)-contaminated soil. The concentration of catechol 2,3-dioxygenase DNA in PAH-contaminated sediment undergoing an ex situ compost process was quantified by competitive PCR over a period of 16 weeks. The concentration of PAHs and catechol 2,3-dioxygenase DNA in the soil samples, was found to correlate.

Adverse effects of hyperoxemia during cardiopulmonary bypass

OBJECTIVE

Aiming at elucidating the effects on capillary blood flow and tissue oxygenation of hyperoxemia during cardiopulmonary bypass, we studied skeletal muscle surface oxygen tensions in 10 patients undergoing elective cardiac operations.

METHODS

In a prospective investigation each patient was exposed to normoxemia (arterial oxygen tension 75 to 115 mm Hg) and hyperoxemia (arterial oxygen tension > 185 mm Hg, inspired oxygen fraction = 1.00) during normal anesthetized conditions before and after cardiopulmonary bypass, as well as during normothermic and hypothermic continuous-flow bypass. In each state hemodynamic variables and arterial and mixed venous blood gas and acid base values were measured. From these data oxygen transport variables were calculated. Tissue oxygenation was studied with the use of a multiple-point polarographic oxygen microelectrode, known to provide measures of oxygen tensions at the capillary level. The oxygen distribution profile of such a sample is also indicative of capillary blood flow distribution changes.

RESULTS

In all patients and at each occasion of the investigation markedly low mean surface oxygen tensions in skeletal muscle were registered. When hyperoxemia was instituted, a significant decrease in these surface oxygen tensions together with an increase in distribution heterogeneity was seen during all stages. Contrary to prebypass, postbypass, and hypothermic bypass, where vascular resistance, oxygen delivery, and oxygen consumption remained similar during hyperoxemia and normoxemia, a significant (p < 0.05) increase in vascular resistance together with a decline in oxygen consumption was seen during hyperoxemic normothermic (35 degrees to 36 degrees C) cardiopulmonary bypass.

CONCLUSION

These findings show that the microcirculatory response to hyperoxemia, seen under other circumstances, persists during continuous-flow cardiopulmonary bypass, normothermic as well as hypothermic. If these adverse effects on tissue oxygenation by hyperoxemia can be further verified and shown to be valid for other organs than skeletal muscle, we would suggest that hyperoxemia should be avoided, especially during normothermic cardiopulmonary bypass.

Nitrendipine and mefruside in elderly hypertensives: effects on blood pressure, cardiac output, cerebral blood flow and metabolic parameters

In this multicentre, randomised, double-blind, cross-over study, we evaluated and compared the effects of nitrendipine (a calcium entry blocker of the dihydropyridine group) and mefruside (a diuretic) on BP, cardiac output, cerebral blood flow and metabolic parameters in 22 elderly hypertensives. Eight weeks of treatment with nitrendipine (27.3 mg daily) and mefruside (30.7 mg daily) significantly reduced BP values to almost the same extent. Heart rate, cardiac output (n = 14), cerebral blood flow (n = 20), renin activity and aldosterone remained unchanged during nitrendipine and mefruside treatment. Nitrendipine did not alter any metabolic parameter (electrolytes, lipid values and blood glucose); in patients treated with mefruside serum potassium fell by 0.4 mmol/l (P < 0.001). Minor adverse events were reported in both treatment groups, mostly due to vasodilation. We conclude that both drugs possess potent and comparable haemodynamic and anti-hypertensive properties. They reduce BP by reducing total peripheral vascular resistance with maintained autoregulation of cerebral blood flow. The metabolic disturbances induced by mefruside seem to be less pronounced than that observed with other thiazide diuretics.

An aromatic effector specificity mutant of the transcriptional regulator DmpR overcomes the growth constraints of Pseudomonas sp. strain CF600 on para-substituted methylphenols

The pVI150 catabolic plasmid of Pseudomonas sp. strain CF600 carries the dmp system, which comprises the divergently transcribed dmpR gene and the dmp operon coding for the catabolic enzymes required for growth on (methyl)phenols. The constitutively expressed DmpR transcriptional activator positively controls the expression of the RpoN-dependent dmp operon promoter in the presence of the aromatic effector in the growth medium. However, the magnitude of the transcriptional response differs depending on the position of the methyl substituent on the aromatic ring. Experiments involving an elevated copy number of the dmp system demonstrate that growth on para-substituted methylphenols is limited by the level of the catabolic enzymes. An effector specificity mutant of DmpR, DmpR-E135K, that responded to the presence of 4-ethylphenol, a noneffector of the wild-type protein, was isolated by genetic selection. The single point mutation in DmpR-E135K, which results in a Glu-to-Lys change in residue 135, also results in a regulator with enhanced recognition of para-substituted methylphenols. The DmpR-E135K mutation, when introduced into the wild-type strain, confers enhanced utilization of the para-substituted methylphenols. These experiments demonstrate that the aromatic effector activation of wild-type DmpR by the para-substituted methylphenols is a major factor limiting the catabolism of these compounds.

General intelligence and cognitive profile in women with congenital adrenal hyperplasia (CAH)

To investigate possible effects of prenatal androgen exposure on cognitive functions, general intelligence and cognitive profile were studied in 22 women, 17-34 years old, with prenatal virilization due to congenital adrenal hyperplasia (CAH) (21-hydroxylase deficiency) and 22 healthy controls matched for region and date of birth. The tests were selected to measure abilities where gender differences repeatedly had been observed or that had earlier shown differences between CAH subjects and controls. The following cognitive functions were tested: Verbal, Visuo-Spatial, Visuo-Motor, Arithmetical, Logical Inductive abilities, and Field Dependence. Contrary to earlier reports, the mean general intelligence level of the CAH (22) group was significantly lower than the controls' and the earlier observed inferiority for calculation abilities in female CAH subjects was not supported by the results of the present study. A possible verbal disadvantage with significantly inferior results was noted for the two verbal tests for the CAH (22) group. For the 13 CAH/control pairs with equal general intelligence levels, the discrepancy between the inferior verbal vs. visual, arithmetic, and logical category scores was significantly larger for the CAH group than the controls. These results may suggest that CAH women develop a more masculine cognitive pattern under the influence of increased prenatal androgen exposure.

Analysis of 16S ribosomal DNA sequences of Francisella strains and utilization for determination of the phylogeny of the genus and for identification of strains by PCR

The 16S ribosomal DNAs (rDNAs) of two strains of Francisella tularensis and one strain of Francisella philomiragia were sequenced. On the basis of phylogenetic analysis data, the genus Francisella was placed in the gamma subclass of the Proteobacteria. The most closely related organism was the intracellular bacterium Wolbachia persica. The sequenced 16S rDNA molecules of the Francisella species exhibited very high levels of similarity (98.5 to 99.9%). Two variable regions, comprising 390 to 450 nucleotides of the 16S rDNA molecules of 17 additional Francisella strains, including members of the species F. tularensis and F. philomiragia, were also sequenced. At most, six nucleotide differences were observed among the sequences of the F. tularensis strains. The sequence of Francisella novicida was virtually identical to the sequences of the F. tularensis strains, thereby supporting the hypothesis that these organisms are members of the same species. On the basis of the observed differences, primer pairs were designed to distinguish strains by using the PCR at the genus, species, and subspecies levels. This permitted sensitive identification of strains belonging to the genus Francisella and discrimination of the species F. tularensis and F. philomiragia.

Identification and classification of different isolates of Francisella tularensis

The causative agent of tularemia, Francisella tularensis, occurs in two main biovars, the highly virulent F. t. biovar tularensis, found in North America; and the less virulent biovar palaearctica, found all over the northern hemisphere. Two other biovars have been proposed, F. t. biovar mediaasiatica and F. t. biovar palaearctica var. japonica. In Sweden tularemia is most frequently observed in man and varying hares (Lepus timidus), and occasionally in other species. Tularemia in hares is normally an acute fatal disease, although less fatal infections have been reported. The diagnosis of tularemia is routinely based on immunological reactions. We studied 10 different isolates of F. tularensis from varying hares, one isolate from an Ural owl (Strix uralensis), one vaccine strain, one strain of F. t. biovar japonica, and six isolates from a virulence study of F. tularensis, by biochemical tests and by hybridization experiments with probes complementary to 16S rRNA. All isolates, except the isolate F. t. biovar japonica, were characterized as F. t. biovar palaearctica by biochemical tests. In the 16S rRNA analysis all isolates were positive to the probe for Francisella tularensis and the probe for F. t. biovar palaearctica with the exception that F. t. biovar japonica reacted with the probe specific to F. t. biovar tularensis. To further confirm that the strains used belonged to F. t. biovar palaearctica virulence tests in rabbits were performed which disclosed this phenotype. The results presented in this work show that the isolated strains from the western part of Europe were F. t. biovar palaearctica, irrespective of animal origin or virulence.

Azepexole, a potent alpha 2-agonist with anaesthetic effects, does not affect cerebral energy consumption in dogs given isoflurane

The effects of the alpha 2-agonist azepexole on the cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) were studied by a sagittal sinus outflow technique in dogs. Azepexole, 1 mg kg-1 (reported to decrease the anaesthetic requirement for isoflurane by almost 90%), caused no change in CMRO2 when given during 1.4% isoflurane anaesthesia. CBF was reduced by 26%. When the concentration of isoflurane was reduced to 0.2%, CMRO2 increased by 26% as would have been expected for the change in isoflurane concentration alone. Concomitantly CBF increased to a level not significantly different from control. Azepexole might be a useful adjunct to inhalational anaesthetics, and combined with a low dose of isoflurane it should be an excellent background anaesthetic when studying the effect of other drugs on CMRO2 in dogs as the combination seems to have little effect on the CMRO2.

Two different beta-lactamase genes are present in Streptomyces cacaoi

Two beta-lactamase genes called blaL and blaU have been cloned independently in Liège and in Umeå, from Streptomyces cacaoi. Genes blaL and blaU were found to differ largely in their nucleotide sequences, although the encoded proteins both belonged to the class A of beta-lactamases (active-site serine penicillinases). DNA-hybridization and polymerase chain reaction assays have now demonstrated that both blaL and blaU genes were present in the S. cacaoi strains used in Liège and in Umeå.

Mutagenic analysis of the promoter of the Streptomyces fradiae beta-lactamase-encoding gene

The Streptomyces fradiae beta-lactamase promoter (PblaF) was sequenced and characterized by promoter probing, primer extension, and exonuclease III-mediated deletions. The transcription start point (tsp) was the same in both S. lividans and S. fradiae. Oligodeoxyribonucleotide-directed random mutations and site-specific mutations were introduced in the promoter region. The effects of these mutations on transcription were assayed by an RNA colony hybridization method. This analysis identified cis-acting sequence determinants located similarly to the -10 and -35 regions of a typical Escherichia coli promoter. Also, a change in the distance between these regions from 19 to 17 bp drastically reduced promoter activity. PblaF was shown not to be recognized by sigma-whiG or by sigma-hrdA, hrdC, or hrdD. Sequence alignment of PblaF to sigma factor-classified Streptomyces promoters revealed little homology. Thus, PblaF is probably recognized by an as yet unidentified sigma factor.

Characterization and classification of strains of Francisella tularensis isolated in the central Asian focus of the Soviet Union and in Japan

The two subspecies of Francisella tularensis, F. tularensis subsp. tularensis (type A) and F. tularensis subsp. palaearctica (type B), differ from each other in biochemistry and virulence. Strains of F. tularensis subsp. tularensis are believed to be confined to North America, whereas strains of F. tularensis subsp. palaearctica occur in Europe, in Asia, and in North America. Moreover, the existence of two other subspecies, designated F. tularensis subsp. mediaasiatica and F. tularensis subsp. palaearcitica japonica, has been suggested for strains of F. tularensis isolated in the central Asian focus of the Soviet Union and in Japan, respectively. In the present study, strains biochemically classified as F. tularensis subsp. mediaasiatica or F. tularensis subsp. palaearctica japonica have been investigated by hybridization with probes specific to 16S rRNAs of the two main subspecies. Furthermore, the virulence and biochemical characteristics of the strains were compared with those of strains belonging to F. tularensis subsp. palaearctica and F. tularensis subsp. tularensis. It was found that 16S rRNAs of F. tularensis subsp. mediaasiatica and F. tularensis subsp. palaearctica japonica hybridize with the probe specific to a genotype proposed herein, genotype A (F. tularensis subsp. tularensis), which shows that strains genetically related to this subspecies are found outside North America. However, the central Asian strains differed from F. tularensis subsp. palaearctica and F. tularensis subsp. tularensis strains when investigated by fermentation of glucose. The results of the biochemical tests could not be unambiguously used for differentiation of strains into F. tularensis subsp. palaearctica or F. tularensis subsp. tularensis. These drawbacks suggest that classification of strains of Francisella on the basis of 16S rRNA analysis may be preferable to classification on the basis of biochemical analysis.