Morphological and phenotypical characterization of Bacillus sporothermodurans

AIMS

Enumeration of resistant bacteria in ultra-high temperature (UHT) treated milk; morphological characterization and phenotyping of resistant strains by traditional and nontraditional methods and their identification by molecular biology.

METHODS AND RESULTS

Modified standard plate count agar (PCA) and modified brain-heart infusion (BHI) agar were used for colony counts. Physiological culture traits were determined as suggested by Bergey's Manual of Systematic Bacteriology or in modified J-broth or in modified BHI agar. Scanning electron microscope (SEM) was used for microscopic examination. Strain identification was carried out by polymerase chain reaction (PCR). A total of 125 (62.81% of 199) samples were positive and the bacterial load was higher than 10(5) CFU ml(-1) in 46 samples (28.80% of 125). The 16S rRNA sequence of bacterial cultures obtained from UHT-treated milk was similar to that of Bacillus sporothermodurans M215 type strain((T)) and different biotypes were found by analysis of colony appearance, cell morphology and physiological traits.

CONCLUSIONS

Bacillus sporothermodurans was the predominant sporigenous micro-organisms in UHT milk.

SIGNIFICANCE AND IMPACT OF THE STUDY

BHI agar is more suitable than PCA for quality control of milk after UHT treatment. Modified J-broth medium is useful to determine selected physiological traits of B. sporothermodurans. The strains characterized and identified as B. sporothermodurans were significantly different compared with the type strain.

Sex chromosome analysis in Turner Syndrome by a pentaplex PCR assay

In this study, we describe a pentaplex PCR to determine the parental origin of the X chromosome and the presence of mosaicism, via amplification of four polymorphic markers located along the X chromosome (DXS10011, DXS6807, HUMARA, DXS101) and the X-Y amelogenin marker, in 41 families having a daughter with Turner Syndrome. Our results confirmed the cytogenetic findings and we found that the parental origin of the single X chromosome to be maternal in 84% of cases.

Different informativeness of the three hypervariable mitochondrial DNA regions in the population of Bologna (Italy)

Mitochondrial DNA (mtDNA) sequence variations at hypervariable regions HVI, HVII and HVIII were analysed in 100 unrelated Italians from Bologna. The values of the statistical parameters are in agreement with the range of European populations. We suggest that the less informative HVIII region may be useful to distinguish HVI-HVII identical sequences in forensic analysis especially when nuclear DNA cannot be investigated.

The HUMFIBRA (FGA) polymorphism in an italian population and a world-wide frequency distribution analysis

OBJECTIVE

The study investigated the highly polymorphic HumFGA short tandem repeat in a sample of 219 unrelated and native individuals from Bologna, and analysed a complete database of FGA allele frequency distributions in 57 world-wide populations collected from the literature.

METHOD

The HumFGA polymorphism was screened by automated fluorescence analysis of PCR-amplified labelled sample fragments performed with an ABI PRISM 310 Genetic Analyser. Genetic distances (Dsw, delta mu2 and Fst) between populations were computed with the MSAT.2 program. Non-metric multidimensional scaling (nmMDS) and neighbour-joining trees (NJTs) were used to investigate patterns of population affinities. Correspondence analysis of the genetic relationships among populations was also performed.

MAIN RESULTS AND CONCLUSIONS

The FGA microsatellite locus is a population marker with a high degree of polymorphism throughout the world. Fourteen HumFGA alleles, ranging in size from 18 to 29 repeats, were identified and sequenced in the Bologna population. The sample was in Hardy-Weinberg equilibrium and had a heterozygosity value of 0.86. Results obtained from the multivariate analyses were consistent in showing great similarity among Europeans. The few African populations investigated were characterized by an even higher level of polymorphism, probably related to the ancient peopling of that continent.

Removal of the N-terminal hexapeptide from human beta2-microglobulin facilitates protein aggregation and fibril formation

The solution structure and stability of N-terminally truncated beta2-microglobulin (deltaN6beta2-m), the major modification in ex vivo fibrils, have been investigated by a variety of biophysical techniques. The results show that deltaN6beta2-m has a free energy of stabilization that is reduced by 2.5 kcal/mol compared to the intact protein. Hydrogen exchange of a mixture of the truncated and full-length proteins at microM concentrations at pH 6.5 monitored by electrospray mass spectrometry reveals that deltaN6beta2-m is significantly less protected than its wild-type counterpart. Analysis of deltaN6beta2-m by NMR shows that this loss of protection occurs in beta strands I, III, and part of II. At mM concentration gel filtration analysis shows that deltaN6beta2-m forms a series of oligomers, including trimers and tetramers, and NMR analysis indicates that strand V is involved in intermolecular interactions that stabilize this association. The truncated species of beta2-microglobulin was found to have a higher tendency to self-associate than the intact molecule, and unlike wild-type protein, is able to form amyloid fibrils at physiological pH. Limited proteolysis experiments and analysis by mass spectrometry support the conformational modifications identified by NMR and suggest that deltaN6beta2-m could be a key intermediate of a proteolytic pathway of beta2-microglobulin. Overall, the data suggest that removal of the six residues from the N-terminus of beta2-microglobulin has a major effect on the stability of the overall fold. Part of the tertiary structure is preserved substantially by the disulfide bridge between Cys25 and Cys80, but the pairing between beta-strands far removed from this constrain is greatly perturbed.

Conformational dynamics of the beta2-microglobulin C terminal in the cell-membrane-anchored major histocompatibility complex type I

We have recently described an anti-beta2-microglobulin (beta2-m) monoclonal antibody (mAb 14H3) capable of recognizing the epitope 92-99 of the protein in the monomeric native state as well as in the fibrillar polymeric state, but not in the major histocompatibility complex type I (MHCI) anchored to the cell membrane. In the present study, we investigated the molecular basis for the inaccessibility of the C-terminal end of beta2-m in the MHCI complex, and demonstrated that mAb 14H3 binds the soluble fraction of the MHCI complex with a Kd of 0.3 microM. An interaction between the complex and the membrane protects beta2-m from immunological recognition at the MHCI level. This protection from antibody recognition can be weakened by procedures such as heat shock or gamma irradiation that perturb the membrane structure and commit the cell to the apoptotic pathway. mAb 14H3 can recognize MHCI in a transient state that most likely precedes beta2-m shedding and may be proposed as a useful tool for dynamic analysis of MHCI conformational modifications.

Myotonic dystrophy CTG repeats in an Italian population sample: evaluation of the polymorphism for forensic applications

The myotonic dystrophy (DM) CTG repeat polymorphism has been studied in an Italian population sample. Polymerase chain reaction (PCR) amplification, manual polyacrylamide gel electrophoresis (PAGE), and silver staining were employed. Alleles were typed by comparison with a sequenced allelic ladder. A total of 25 different alleles, spanning the range from 5 to 31 CTG triplets, was observed. The heterozygosity was 79%, and no significant deviation from Hardy-Weinberg equilibrium was found. Eighty-one meioses from parentage testing were also analyzed, and a Mendelian pattern of inheritance was observed in all cases. In addition, we could successfully type the DM locus in 20 laboratory-prepared bloodstains, with 1 ng of DNA allowing clear definition of alleles. We conclude that the CTG repeats at the DM locus may be useful for forensic applications.

Management of animal health emergencies: general principles and legal and international obligations

The Eighth Round of the General Agreement on Tariffs and Trade led to the creation of the World Trade Organization and to the adoption of the Sanitary and Phytosanitary (SPS) Agreement, thus considerably changing the rules of international trade in animals and animal products. Animal health measures may result in trade restrictions, but governments accept that these restrictions may sometimes be necessary and appropriate to ensure food safety and animal health protection. The SPS Agreement acknowledges the rights of governments to adopt measure to protect human, animal and plant health. To ensure effective animal health protection, without unjustifiable discrimination, the operational procedures of Veterinary Services must be standardised, especially those concerning disease notification, epidemiological information, certification for international trade and management of animal health emergencies. Veterinary Services must be further supported by a proper legislative framework and adequate financial resources.

Beta2-microglobulin can be refolded into a native state from ex vivo amyloid fibrils

Beta2-microglobulin fibrils have been extracted from the femoral head of a patient who has been under chronic haemodialysis for 11 years. The primary structure of the N-terminal portion of the protein and mass determination by electrospray mass spectrometry demonstrate that beta2-microglobulin, extracted as fibrils by the water extraction procedure, was not glycated and that Asn17 was not deamidated. Limited proteolysis was observed in more than 20% of beta2-microglobulin molecules and the main cleavage sites were at the C-terminus of Lys6 and Tyr10. Beta2-microglobulin from fibrils has been purified by gel filtration in 6 M Gdn/HCl and submitted to a refolding procedure. The refolding conditions have been determined through the study of the unfolding pathway of the native protein. Beta2-microglobulin is stable at neutral pH where it displays a lower tendency to self-aggregate than in acidic conditions. Pulse dilution and extensive dialysis in refolding buffer at pH 7.5 yields beta2-microglobulin with a tertiary structure identical to that of the native form. The CD spectrum in the near-ultraviolet region and the spectrum of the intrinsic fluorescence of Trp overlap those of the native protein, but the CD spectrum in the far-ultraviolet region is affected by the contribution of oligomers created by beta2-microglobulin fragments that reduce the positive light polarisation at 205 nm typical of native beta2-microglobulin.

Determination of HPRT mutant frequency and molecular analysis of T-lymphocyte mutants derived from coke-oven workers

We measured the frequency of mutant (MF) lymphocytes at the hprt locus in a population of 43 coke-oven workers exposed to PAH and in a group of 26 non-exposed workers. A non-significant increase in MF in the exposed group (19.0 +/- 16.3) compared to the non-exposed group (15.8 +/- 14.6) was observed. Moreover, when we considered smoking habits for the overall population, the MF values were higher, although not significantly, in smokers than in non-smokers. For some T-cell mutant clone structural alterations, splicing and coding errors were detected by PCR-based methods. We analysed 161 HPRT- clones, derived from exposed and non-exposed workers by multiplex-PCR and 56 HPRT- clones by reverse transcriptase-PCR. Overall, the percentages of the different types of gene alterations were similar in exposed and non-exposed subjects. Only the frequency of splice mutations in mutant clones derived from coke-oven workers was higher (22%) than in non-exposed donors (11%).

Use of anti-(beta2 microglobulin) mAb to study formation of amyloid fibrils

Three mAbs, IgG1k 1F11, 7B6 and 14H3, were raised against in vitro-self-aggregated beta2-microglobulin. They recognize the native and unfolded forms of the protein and bind its fibrillar form that is present in amyloid tissue. When assayed in fibrillogenesis tests in vitro, mAb 14H3 inhibited fibril formation from beta2-microglobulin. This mAb recognizes a sequential epitope corresponding to the C-terminal octapeptide, residues 92-99, of beta2-microglobulin. By using synthetic peptides it has been found that the integrity of the sequence is essential for the formation of the immunocomplex: the binding affinity is lowered by one order of magnitude (Kd from 10(-7) M to 10(-6) M) by removal of Met99 and completely abolished when both Asp98 and Met99 are lost or Arg98 is substituted with Lys. The other two mAbs, 1F11 and 7B6, which bind sequences 20-41 and 63-75, respectively, are without effect on beta2-microglobulin fibrillogenesis. These two mAbs recognize beta2-microglobulin bound to the heavy chain in the major histocompatibility complex of type I located in the cell membrane, a property which is not shared by mAb 14H3.

Structural and functional characterization of three human immunoglobulin kappa light chains with different pathological implications

The structural properties of three immunoglobulins light chains: kappa SCI, responsible for light chain deposition disease (Bellotti, V., Stoppini, M., Merlini, G., Zapponi, M.C., Meloni, M.L., Banfi, G. and Ferri, G. (1991) Biochim. Biophys. Acta 1097, 177-182), k INC responsible for light chain amyloidosis (Ferri, G., Stoppini, M., Iadarola, P., Bellotti, V. and Merlini, G. (1989) Biochim. Biophys. Acta 995, 103-108) and the non-pathogenic kappa MOS were analyzed by fluorescence spectroscopy and circular dichroism. Comparative evaluation of the data shows that SCI and MOS have similar stability under different conditions, while the amyloid k INC behaves as a very unstable protein. As calculated from the GdnHCl curves, the midpoint of unfolding transition was 1.35 M for SCI, 1.20 M for MOS and 0.1 M for INC. Analysis of CD spectra evidences that the three proteins conserve their conformation in the range of pH 4-8. Change in temperature at pH 4.0 produces the premature transition of INC (Tm 40 degrees C) with respect to SCI and MOS (Tm 50 degrees C). At this pH both the pathological SCI and INC light chains aggregate at a temperature of 20 degrees C lower than the normal counterpart. The specific kidney deposition of kappa SCI has been evidenced after injection of the 125I labelled light chain into mice. No deposition was detectable in the case of INC and MOS.

Cytogenetic studies in coke oven workers

Chromosome aberrations, micronuclei, and sister chromatid exchanges (SCE) were evaluated in cultured lymphocytes of coke oven workers of an Italian steel industry plant, occupationally exposed to polycyclic aromatic hydrocarbons, and in a group of unexposed controls from a non-oven plant in the same area. No differences were found between exposed and controls for rates of total abnormal metaphases (including and excluding gaps), chromatid-type and chromosome-type aberrations, cells with 2 or more breaks, and for micronuclei. On the contrary, SCE were significantly increased in the exposed versus the controls, but, when smoking habits were considered, the increase was significant only for smokers.

Affinity labelling of the catalytic and allosteric ATP binding sites on pyruvate kinase type I from Escherichia coli

The allosterically regulated pyruvate kinase type I (PKI) from E. coli was inactivated by the ATP analog 2',3'-dialdehyde ATP (o-ATP) with a Ki of 3.6 mM. ATP and phosphoenolpyruvate protected the enzyme activity while the allosteric activator fructose 1,6-bisphosphate enhanced the rate of inactivation. Incubation with o-ATP, followed by reduction of the formed Schiff bases with radioactive sodium borohydride, was employed to determine the ATP binding sites of PKI. After tryptic digestion, the purification of the labelled peptides and the sequence analysis allowed to identify four modified lysyl residues, namely Lys173, Lys175, Lys272, and Lys317 of the known DNA-deduced sequence of PKI. The close lysines 173 and 175 reacted with o-ATP in a mutually exclusive way and accounted together for 53% of the recovered radioactivity, the rest being distributed on Lys272 (31%) and Lys317 (16%). When fitted on the available three-dimensional structure of muscle pyruvate kinase, the position of the modified lysines defines both the catalytic and the allosteric ATP binding sites on PKI.

Characterization of the two unique human anti-flavin monoclonal immunoglobulins

Form A of two previously described human monoclonal anti-riboflavin IgGs, the GAR [Farhangi, M. & Osserman, E. F. (1976) N. Engl. J. Med. 294, 177-183] and DOT [Merlini, G., Bruening, R., Kyle, R. & Osserman, E. F. (1990) Mol. Immunol. 27, 385-394], has been characterized in terms of binding properties and primary structure. Both forms were isolated as immunocomplexes with bound riboflavin and gave a reconstitutable apoprotein. The riboflavin-reconstituted IgGs showed a similar visible absorption spectrum, with a marked resolution of the 445-nm band and a ratio 445-nm/370-nm peaks of 1.13 for DOT and 1.19 for GAR. Both proteins bind riboflavin, FMN and FAD with a molar ratio ligand/protein of 2:1. DOT and GAR share a very similar affinity for the flavinic ligands; the Kd values for riboflavin and FMN are in the range 1 nM; that for FAD is an order of magnitude higher. DOT and GAR do not form an adduct between the nucleophilic group sulfite and the N(5) position of the flavin, and do not stabilize any flavinic semiquinone during reduction with the xantine/xantine oxidase benzylviologen system. The primary structure of fragment antigen binding (Fab) DOT and heavy-chain variable region (VH) GAR determined in the present study and that already known for the light-chain variable region (VL) GAR [Kiefer, C. R., McGuire, B. S., Osserman, E. F. & Garver, F. A. (1983) J. Immunol. 131, 1871-1875] evidenced that the two IgGs are assembled with VL and VH chains of different subgroups; a lambda III/HIII pair in GAR, and a lambda II/HI pair in DOT. Although less similar each other than to the counterparts of the same subclasses, DOT and GAR share an exclusive identity in the VH CDR3 region.

Urinary excretion of mutagens in coke oven workers

The influence of occupational exposure to polycyclic aromatic hydrocarbons (PAHs) on urinary mutagenic activity was assessed in 75 coke oven workers, using a highly sensitive bacterial mutagen technique (extraction with C18 resin and liquid micro-preincubation test on strain TA98 of Salmonella typhimurium in the presence of metabolizing and deconjugating enzymes). Exposure to PAHs was assessed according to the urinary excretion of 1-pyrenol; the main confounding factors were checked by the number of cigarettes smoked per day and the levels of nicotine and its metabolites in urine, or by ascertaining whether recommended dietary restrictions had been followed. Of the 20 urine samples which turned out to be positive (producing at least double the number of spontaneous revertants), 19 (95%) belonged to smokers. Only one non-smoker had obvious urinary mutagenic activity, and was highly exposed occupationally to PAHs (urinary 1-pyrenol of 3.930 mumol/mol of creatinine). Of the five urine samples from subjects who had not followed the recommended diet, two (40%) were clearly mutagenic. Multiple regression analysis (n = 67) showed that the presence of samples positive for urinary mutagenic activity depended only on smoking habits, if this confounding factor was assessed according to the number of cigarettes smoked per day, while the significant influence of exposure to PAH could be shown when the confounding factor was objectively estimated according to the urinary levels of nicotine and its metabolites. Assessment of the mutagenic potency of urinary extracts (net revertants/mmol creatinine) confirmed the strong influence of smoking habits on urinary mutagenic activity (all smokers 2156 +/- 2691 versus non-smokers 939 +/- 947 net revertants/mmol creatinine; Mann-Whitney test: P < 0.01). In smokers highly exposed to PAHs, greater excretion of mutagens with respect to low-exposure smokers was revealed (3548 +/- 4009 versus 1552 +/- 1227 net revertants/mmol creatinine; Mann-Whitney test: P < 0.01). Multiple regression analysis showed that the mutagenic potency of urinary extracts of coke oven workers depended on exposure to PAHs, tobacco smoking habits, and consumption of fried, grilled or barbecued meat. Increased urinary mutagenic activity strengthens epidemiological evidence of the increased risk of renal and urinary tract tumours in these workers. The presence of mutagenic metabolites in urine as a result of occupational exposure to PAH may be demonstrated only by using highly sensitive techniques for assessing urinary mutagenic activity in studies which include careful checking of the main confounding factors.

Feasibility and reliability of flow-cytometry (fcm) DNA analysis of fresh and fixed urine samples

The qualitative results of FCM DNA analysis on fresh and fixed urine specimens (28 and 97, respectively) from 68 normal subjects and 10 patients with a past history of bladder cancer were compared. FCM DNA evaluability was not significantly different in fresh and fixed samples (63% vs 73%, respectively) whereas mean CV was significantly higher (7.3% vs 5.7%, respectively; p=0.04). A double FCM analysis on fresh and fixed urine was also performed in 16 cases. In this subgroup, the percentage of evaluable histograms from fixed urine specimens was slightly higher than that from fresh specimens. Aneuploid cases were found only in the fixed urine samples but the CVs from fresh and fixed cell suspensions did not differ. The absence of inflammatory cells with cytological analysis of the same samples was associated with low percentages of FCM evaluability and higher CVs. The use of fixed samples improves the quality of FCM DNA analysis permitting its use for screening programs.

Limited proteolysis of chloroplast glyceraldehyde-3-phosphate dehydrogenase (NADP) from Spinacia oleracea

The structural and functional properties of chloroplast glyceraldehyde-3-P-dehydrogenase I (D-Glyceraldehyde-3-phosphate: NADP oxidoreductase (phosphorylating) EC 1.2.1.13) from Spinacia oleracea were investigated by limited proteolysis. The enzyme is insensitive to trypsin and chymotrypsin, while Staphylococcus aureus V8 protease cleaves the C-terminal region of its subunits. Subunit A (36 kDa) is only partially cleaved at Glu 317. No intact subunit B (39 kDa) is found at the end of the proteolytic experiment: two forms are originated from this subunit which is cleaved at Glu 342 and Glu 320. Proteolytic cleavage at these sites does not significantly alter enzymatic activity, but leads to destabilization of the protein. Unlike the intact parent enzyme (600 kDa) the cleaved enzyme behaves as a 150-kDa species in size exclusion chromatography.

Relation between sex hormones and serum lipoprotein and lipoprotein(a) concentrations in premenopausal obese women

Lipoprotein(a) (Lp[a]) is generally considered to be a risk factor for the development of cardiovascular disease, but little is known about the possible influence of obesity on the circulating levels of this lipoprotein. The present study was undertaken to examine this aspect in 136 menstrually active women by comparing the serum concentrations of Lp(a) between 72 obese and 64 age-matched nonobese women. Since an adverse effect of androgens and a protective effect of estrogens have been described for plasma lipoprotein profiles in obese women, the relation between the circulating levels of Lp(a) and those of these other hormones was also investigated in obese patients. In addition, other lipoproteins, anthropometric parameters (body mass index and waist-to-hip ratio), and insulin were evaluated. The levels of Lp(a) were not significantly different (Mann-Whitney U test chi 2, 3.59; p = 0.0582 [NS]) between obese (rank sum, 5,367) and control (rank sum, 3,949) women; in addition, the percentage of patients with high Lp(a) levels (cutoff defined at 30 mg/dL) did not differ between the two groups (obese women, 30%; control, 21.8%; chi 2, 0.90; two-sided p = 0.341 [NS]). Moreover, no correlation was found between Lp(a) and body mass index. Lastly, when the Lp(a) prevalence odds ratio for obesity was examined by adjusting the levels of this lipoprotein for age, triglycerides, total cholesterol, and high density lipoprotein cholesterol, the probability value (0.88) was far from significant. In obese women, no correlation was found between the logarithmically transformed Lp(a) concentrations and all the other variables evaluated in the study. In conclusion, the present study shows that the circulating levels of Lp(a) are not influenced by body weight and cardiovascular risk factors commonly associated with obesity, such as enhanced androgenic activity, hyperinsulinemia, adverse lipoprotein profile, and abdominal fat accumulation.

Divergent binding sites in pyruvate kinases I and II from Escherichia coli

Pyridoxal 5'-phosphate incorporation into pyruvate kinase II from E. coli was decreased by the substrate phosphoenolpyruvate and increased by the allosteric activator ribose 5-phosphate, the total incorporation being linearly related to inactivation. Four lysyl residues were substantially modified, whatever the incubation conditions were while two additional residues became reactive only in the presence of the allosteric activator. Six tryptic peptides containing modified lysines were purified and sequenced. They defined five regions of pyruvate kinase II, since one of them contained two labelled lysines and included a peptide which also appeared independently. Sequence comparison with E. coli type I, yeast and cat muscle pyruvate kinases shows that the binding regions of pyruvate kinase II are clearly divergent from those of pyruvate kinase I and of the eukaryotic enzymes.