Synthetic phytochelatin surface display in Cupriavidus metallidurans CH34 for enhanced metals bioremediation

This work describes the effects of the cell surface display of a synthetic phytochelatin in the highly metal tolerant bacterium Cupriavidus metallidurans CH34. The EC20sp synthetic phytochelatin gene was fused between the coding sequences of the signal peptide (SS) and of the autotransporter β-domain of the Neisseria gonorrhoeae IgA protease precursor (IgAβ), which successfully targeted the hybrid protein toward the C. metallidurans outer membrane. The expression of the SS-EC20sp-IgAβ gene fusion was driven by a modified version of the Bacillus subtilis mrgA promoter showing high level basal gene expression that is further enhanced by metal presence in C. metallidurans. The recombinant strain showed increased ability to immobilize Pb(2+), Zn(2+), Cu(2+), Cd(2+), Mn(2+), and Ni(2+) ions from the external medium when compared to the control strain. To ensure plasmid stability and biological containment, the MOB region of the plasmid was replaced by the E. coli hok/sok coding sequence.

In vitro effects of gamma radiation from 60Co and 137Cs on plasmid DNA

The effects of gamma radiation from (60)Co and (137)Cs on DNA in aqueous solution are studied experimentally. Using an improved plasmid purification protocol and improved electrophoretic gel analysis techniques provided results with relatively small uncertainties. The results are compared with both theoretical and experimental results. In particular, the results obtained here are discussed in the light of recent discussion on supposed differences of the effects induced by gamma radiation from (60)Co and (137)Cs. We find that the effects of both types of gamma radiation are similar.

Weight evolution in girls treated for idiopathic central precocious puberty with GnRH analogues

Data concerning the effects of GnRHa on weight gain are scarce.

OBJECTIVE

To assess the variation of the body mass index (BMI) in girls during GnRHa treatment for idiopathic central precocious puberty (CPP).

PATIENTS AND METHODS

Semestral anthropometric data from 176 girls treated with goserelin or leuprorelin were analyzed.

RESULTS

BMI z-score increased from 1.5 +/- 0.1 SD before treatment (n = 176) to 1.7 +/- 0.2 SD after 24 months (n = 61, p = 0.008). In girls with normal weight before treatment, this variation was greater (n = 112, 0.2 +/- 0.1 SD, p = 0.01) than in those who were overweight (n = 63, -0.9 +/- 0.2 SD, p = 0.7). In the goserelin group the weight change adjusted for bone age was greater (n = 28, 0.4 +/- 0.1 SD) than in the leuprorelin group (n = 5, 0.04 +/- 0.1 SD, p = 0.05).

CONCLUSIONS

A slight increase in BMI was noted, mainly in girls with normal weight before treatment. The influence of different GnRHa on weight must be further investigated.

Pectinolytic activity secreted by yeasts isolated from fermented citrus molasses

AIMS

The aim of this study was to obtain improved strains of pectinolytic yeasts adapted to the conditions of an industrial fermentation process, which was continuously operated to convert citrus molasses into ethanol.

METHODS AND RESULTS

The starter yeast of the industrial fermentation process was a commercial baker's yeast, which was capable of growing without forming any secretion halo of pectinase activity on solid medium. Nevertheless, isolates showing secretion of pectinolytic activity on plates were obtained from the fermentation process. The secretion of pectin-degrading activity by isolates on plates was repressed by galactose and improved as the result of colony aging on polygalacturonic acid plates at 30 degrees C. Liquefaction of polygalacturonate gels as well as the splitting of the pectin-degrading activity into a wall-linked and a supernatant fraction were also observed when the starter yeast was propagated under agitation in liquid medium containing pectin.

CONCLUSIONS

Isolates capable of secreting pectinolytic activity on plates were predominant at the end of the citrus molasses fermentation. Nevertheless, the sizes of the secretion haloes on plates were not necessarily an indication of the levels of pectinolytic activity secreted in the liquid medium.

SIGNIFICANCE AND IMPACT OF THE STUDY

Improved pectinolytic strains of Saccharomyces can be used as a source of pectinases for a variety of applications. This organism also participates in plant deterioration processes.

A novel system of genetic transformation allows multiple integrations of a desired gene in Saccharomyces cerevisiae chromosomes

Increasing industrial competitiveness and productivity demand that recombinant yeast strains, used in many different processes, be constantly adapted and/or genetically improved to suit changing requirements. Among yeasts, Saccharomyces cerevisiae is the best-studied organism, and the most frequently employed yeast in industrial processes. In the present study, laboratory strains and industrial S. cerevisiae strains were stably transformed with a novel vector containing the glucoamylase cDNA of Aspergillus awamori flanked by delta-sequences (deltaGlucodelta), and lacking a positive selection marker. Co-transformation with known plasmids allowed selection by auxotrophic complementation of the leu2 mutation and/or geneticin resistance (G418). In all cases, several copies of the deltaGlucodelta vector were inserted into the genome of the yeast cell without selective pressure, showing 100% stability after 80 generations. Transformation frequency of the new vector was similar for S. cerevisiae laboratory strains and industrial wild-type S. cerevisiae strains. This novel genetic transformation system is versatile and suitable to introduce several stable copies of a desired expression cassette into the genome of different S. cerevisiae yeast strains.

Phenotypic characterization of Trichophyton rubrum isolates from two geographic locations in Brazil

To characterize possible Trichophyton rubrum phenotypes, which circulate in two Brazilian localities, we tested 53 isolates of this dermatophyte for their ability to assimilate several carbon sources, for keratinase, proteinase, phospholipase, lipase and desoxiribonuclease (DNase) secretions, and for their susceptibility to the antifungals fluconazole, ketoconazole and itraconazole. For each method, the isolates were submitted to similarity analysis and the methods were evaluated for their discriminatory indexes. None of the isolates were capable of assimilating arabinose, dulcitol, lactose, melibiose, ribose and xylose, while all of the isolates assimilated maltose, sucrose and sorbitol. However, adonitol, cellobiose, dextrin, erythritol, fructose, galactose, inulin, mannitol, mannose, raffinose, rhamnose and trehalose were assimilated by some isolates but not by others. All isolates secreted keratinase and DNase, while none secreted phospholipase. Proteinase and lipase were secreted only by some isolates. All but four isolates were resistant to fluconazole, most of them were sensitive to ketoconazole and all were sensitive to itraconazole. Carbohydrate assimilation was the method that presented the highest discriminatory index, and also the method that displayed the largest number of biotypes. Taken together, these data suggest that significant phenotypic variations exist among T. rubrum isolates. They seem to occur independently from their geographic origins.

Studies on polyhydroxyalkanoate (PHA) accumulation in a PHA synthase I-negative mutant of Burkholderia cepacia generated by homogenotization

In the genome of Burkholderia cepacia strain IPT64, which accumulates a blend of the two homopolyesters poly(3-hydroxybutyrate), poly(3HB), and poly(3-hydroxy-4-pentenoic acid), poly(3H4PE), from sucrose or gluconate as single carbon source, the polyhydroxyalkanoate (PHA) synthase structural gene was disrupted by the insertion of a chloramphenicol-resistant gene cassette (phaC1::Cm). The suicide vector pSUP202 harboring phaC1::Cm was transferred to B. cepacia by conjugation. The inactivated gene was integrated into the chromosome of B. cepacia by homologous recombination. This mutant and also 15 N-methyl-N'-nitrosoguanidine (NMG)-induced mutants still accumulated low amounts of PHAs and expressed low PHA synthase activity. The analysis of the mutant phaC1::Cm showed that it accumulated about 1% of PHA consisting of 68.2 mol% 3HB and 31.8 mol% 3H4PE from gluconate. The wild-type, in contrast, accumulated 49.3% of PHA consisting of 96.5 mol% 3HB and 3. 5 mol% 3H4PE. Our results indicated that the genome of B. cepacia possesses at least two PHA synthase genes, which probably have different substrate specificities.

Antimicrobial resistance patterns of Haemophilus influenzae isolated from patients with meningitis in São Paulo, Brazil

From 1989 to 1995, a total of 391 Haemophilus influenzae isolates were recovered from the cerebrospinal fluid (CSF) of hospitalized patients in São Paulo, Brazil. The majority of strains were isolated from infants aged less than 5 years. Strains belonging to biotype I (64.7%), biotype II (34.5%) and biotype IV (0.76%) were detected. Ninety-nine percent of these strains were serotype b. Minimal inhibitory concentration (MIC) was determined for ampicillin, chloramphenicol and ceftriaxone. The ss-lactamase assay was performed for all strains. The rate of ss-lactamase producer strains ranged from 10 to 21.4% during a period of 7 years, with an overall rate of 13.8%. Of the 391 strains analyzed, none was ss-lactamase negative ampicillin resistant (BLNAR). A total of 9.7% of strains showed resistance to both ampicillin and chloramphenicol; however, 4% of them were resistant to ampicillin only and 2% to chloramphenicol. All strains were susceptible to ceftriaxone and the MIC90 was 0.007 microg/ml, suggesting that ceftriaxone could be an option for the treatment of bacterial meningitis in pediatric patients who have not been screened for drug sensitivity.

Further characterization of the yeast pso4-1 mutant: interaction with rad51 and rad52 mutants after photoinduced psoralen lesions

The pso4-1 mutant was characterized as deficient in some types of recombination, including gene conversion, crossing over, and intrachromosomal recombination. The mode of interaction between pso4-1 and rad51 and between pso4-1 and rad52 mutants indicated that the PSO4 gene belongs to the RAD52 epistasis group for strand-break repair. Moreover, the presence of the pso4-1 mutation decreased 8-MOP-photoinduced mutagenesis of the rad51 and rad52 mutants. Complementation tests using heterozygous diploid strains showed that the pso4 protein might interact with the rad52 protein during repair of 8-mop photolesions. The pso4-1 mutant, even though defective in inter- and intra-chromosomal recombination, conserves the ability for plasmid integration of circular and linear plasmid DNA. On the other hand, similar to the rad51 mutant, pso4-1 was able to incise but did not restore high-molecular-weight DNA during the repair of cross links induced by 8-MOP plus UVA. These results, together with those of previous reports, indicate that the PSO4 gene belongs to the RAD52 DNA repair group and its product participates in the DNA rejoining step of the repair of cross-link lesions, which are crucial for induced mutagenesis and recombinogenesis.

Immunogenic properties of the M. leprae recombinant 18-kDa antigen purified from Saccharomyces cerevisiae; enhancement of delayed-type hypersensitivity after gamma-irradiation

In this paper we report the purification and study of the immunogenic properties of the Mycobacterium leprae 18-kDa protein antigen produced and secreted by the yeast Saccharomyces cerevisiae, using an expression system we recently described [Biotech. Lett. 16 (1994) 1241-1246]. The 18-kDa protein was purified from the yeast culture media by precipitation, ion exchange chromatography (MonoQ) and exclusion size chromatography (Sephacryl S-100). The biological properties of the recombinant protein, previously irradiated with gamma rays, were assayed by immunization of mice. Humoral and cellular responses, monitored by antibody production and delayed-type hypersensitivity, respectively, were obtained. Furthermore, gamma-irradiation of the recombinant protein prior to the administration was shown to significantly potentiate the T-cell response. The data suggest that this irradiated recombinant antigen could be used in a more sensitive standardized skin test to monitor M. leprae infection.

PSO4: a novel gene involved in error-prone repair in Saccharomyces cerevisiae

The haploid xs9 mutant, originally selected for on the basis of a slight sensitivity to the lethal effect of X-rays, was found to be extremely sensitive to inactivation by 8-methoxypsoralen (8MOP) photoaddition, especially when cells are treated in the G2 phase of the cell cycle. As the xs9 mutation showed no allelism with any of the 3 known pso mutations, it was now given the name of pso4-1. Regarding inactivation, the pso4-1 mutant is also sensitive to mono- (HN1) or bi-functional (HN2) nitrogen mustards, it is slightly sensitive to 254 nm UV radiation (UV), and shows nearly normal sensitivity to 3-carbethoxypsoralen (3-CPs) photoaddition or methyl methanesulfonate (MMS). Regarding mutagenesis, the pso4-1 mutation completely blocks reverse and forward mutations induced by either 8MOP or 3CPs photoaddition, or by gamma-rays. In the cases of UV, HN1, HN2 or MMS treatments, while reversion induction is still completely abolished, forward mutagenesis is only partially inhibited for UV, HN1, or MMS, and it is unaffected for HN2. Besides severely inhibiting induced mutagenesis, the pso4-1 mutation was found to be semi-dominant, to block sporulation, to abolish the diploid resistance effect, and to block induced mitotic recombination, which indicates that the PSO4 gene is involved in a recombinational pathway of error-prone repair, comparable to the E. coli SOS repair pathway.