Bioaccessibility of Cd and Pb in tailings from a zinc smelting in Brazil: implications for human health.

Soils and wastes enriched with heavy metals may present ecological and human health risks. A considerable number of mining areas exist in Brazil, where high levels of metals have been found. However, studies of bioaccessibility of metals in soils/tailings from these areas are scarce, despite their potential informational contribution concerning exposure risks of residents near these areas. This study evaluated tailings collected from four sites of a zinc smelting area located in Brazil with aims to: (1) evaluate the presence of metals of potential concern; (2) investigate Cd and Pb bioaccessibility; and (3) determine the desorption kinetics of Cd and Pb. High concentrations of total Cd and Pb (up to 1743 mg Cd kg(-1) and 8675 mg Pb kg(-1)) and great variability were found in the tailings, indicating the importance of adequate planning for their final disposal, in order to avoid contamination in the surrounding environment. Cadmium and Pb bioaccessibility percentages in the intestinal phase were less than 47 and 4 %, respectively, which represents significant fractions not available for absorption in the intestinal tract. However, this material has to be monitored since its bioaccessibility may increase with eventual physicochemical changes, releasing Cd and Pb. Desorption kinetics experiments revealed that Pb in the samples remained in less labile fractions, whereas Cd was found in more labile fractions, which is in accordance with the bioaccessibility results.

Binding intensity and metal partitioning in soils affected by mining and smelting activities in Minas Gerais, Brazil.

Mining and smelting activities are potential sources of heavy metal contamination, which pose a threat to human health and ecological systems. This study investigated single and sequential extractions of Zn, Pb, and Cd in Brazilian soils affected by mining and smelting activities. Soils from a Zn mining area (soils A, B, C, D, E, and the control soil) and a tailing from a smelting area were collected in Minas Gerais state, Brazil. The samples were subjected to single (using Mehlich I solution) and sequential extractions. The risk assessment code (RAC), the redistribution index (U ts ), and the reduced partition index (I R ) have been applied to the sequential extraction data. Zinc and Cd, in soil samples from the mining area, were found mainly associated with carbonate forms. This same pattern did not occur for Pb. Moreover, the Fe-Mn oxides and residual fractions had important contributions for Zn and Pb in those soils. For the tailing, more than 70 % of Zn and Cd were released in the exchangeable fraction, showing a much higher mobility and availability of these metals at this site, which was also supported by results of RAC and I R . These differences in terms of mobility might be due to different chemical forms of the metals in the two sites, which are attributable to natural occurrence as well as ore processing.

Distinct groups of plasmids correlated with bacteriocin production in Staphylococcus aureus.

The genetic basis of bacteriocin (Bac) production by six strains of Staphylococcus aureus was examined. Gene transfer experiments (in which the plasmids were tagged with the erythromycin resistance transposon Tn551) and plasmid-elimination experiments by growth at 43 degrees C associated bacteriocin production with a particular plasmid in each strain. The Bac plasmids could be separated into two distinct groups: the first comprised plasmids larger than 40 kb, which did not specify immunity to bacteriocins; the second comprised small plasmids (8.0-10.4 kb) which also specified immunity to bacteriocins. The sequence relations among the small plasmids (pRJ6, pRJ9, pRJ10 and pRJ11) were investigated by comparing restriction enzyme digest patterns and by hybridization. Plasmids pRJ10 and pRJ11 were indistinguishable and very closely related to plasmid pRJ9. Plasmid pRJ6, although different from the others, shared regions of sequence homology with them. No homology was found between plasmids pRJ6 or pRJ9 and the large Bac plasmids.

Production of a bacteriophage, a phage tail-like bacteriocin and an antibiotic by Bacillus azotofixans.

Twenty-two nitrogen-fixing Bacillus azotofixans strains were shown to produce an inhibition zone against themselves in plate assays. The B. azotofixans type strain P3L-5, chosen for further studies, produced inhibition zones against various Bacillus strains and other bacterial genera. This antibacterial substance was also produced in liquid medium and its production was enhanced in semisolid medium (0.4% agar) after 3 to 5 days of incubation. The substance was suggested to be an antibiotic and its preliminary characterization showed resistance to heat (100 degrees C, 15 minutes), to trypsin, pronase, deoxyribonuclease I, ribonuclease A, phospholipase C, ethanol, acetone, and ether, and sensitivity to strong alkali treatment. Its molecular weight was estimated to be between 3500 to 6000. After induction of B. azotofixans P3L-5 with mitomycin C or ultraviolet light, two types of particles were detected in the lysate: one similar to a phage tail and the other, less frequent, similar to a complete bacteriophage. Lysates containing these particles showed a killing effect in some but not all B. azotofixans strains, but neither the other Bacillus species nor Micrococcus were inhibited by these lysates.

Identification of Bacillus azotofixans using API tests.

The identification of Bacillus azotofixans strains using API tests is described. Twenty-two strains were studied according to their fermentation pattern on 49 different carbohydrates. A profile of the B. azotofixans type strain is presented, together with an average profile of all strains tested. The fermentation pattern for B. azotofixans is also compared to those of the closely similar species B. polymyxa and B. macerans. These profiles may be useful for the identification of new strains.

Bacillus polymyxa bacteriophages from Brazilian soils.

Ten phages of Bacillus polymyxa were isolated from four different Brazilian soils. All were dsDNA-containing phages belonging to Bradley types A and B. Data obtained from electron microscopy and tests of resistance against physical and chemical agents showed that the isolates could be distributed among six different groups. Host range data were in agreement with this classification. When tested against 88 strains of 18 Bacillus species, these phages only infected B. polymyxa strains, thus revealing specificity for this species. Three phage groups lysed all 42 available B. polymyxa strains and are suggested for use in rapid identification of this species.

A screening of resistance and virulence factors in Staphylococcus aureus.

O estudo de 137 estirpes de Staphylococcus aureus, recentemente isoladas de pacientes nao hospitalizados e de alimentos, mostrou alta percentagem de resistencia a penicilina G e percentual variavel a eritromicina, cloranfenicol, tetraciclina, canamicina, amicacina, sulfadiazina e estreptomicina. Uma estirpe produziu enterotoxina B e mal produziram enterotoxina C. Agentes estafilococcinogenicos foram detectados em 13 estirpes

Characterization of a new Bacillus megaterium bacteriophage, MJ-1, from tropical soil.

A new Bacillus megaterium bacteriophage is characterized. It is a tailed phage with regular polyhedral head belonging to Bradley's group B. Head and tail dimensions are 56.4 and 300 nm, respectively. Lysis was restricted to strains of B. megaterium. No antigenic relationship with pumilus phage FP-1 or subtilis phage FS-1 was observed. The phage is sensitive to 60 degrees C and moderately sensitive to chloroform. The nucleic acid is double-stranded linear DNA with a G-C mole% of 38.8 and a mol wt of (53 +/- 3) X 10(6).

Host range specificity of two groups of soil-isolated Bacillus phages.

Foram testadas 95 estirpes de Bacillus e 10 de Staphylococcus aureus quanto a sensibilidade face a 14 fagos recem isolados de B. subtilis e 16 de B. pumilus.Todas as estirpes de S. aureus e 65 de Bacillus mostraram-se resistentes a lise por quaisquer dos fagos de Bacillus.Entre as estirpes de referencia, apenas aquelas de B.subtilis e B. pumilus foram lisadas por fagos de ambos os hospedeiros. As estirpes sensiveis recentemente isoladas foram identificadas como B. subtilis e B. pumilus Todos os fagos de B. subtilis eram especies especificos; no entanto, a maioria dos fagos de B. pumilus lisava ambas as especies. Tais dados confirmam a proximidade taxonomica destas especies

Properties of a new Bacillus megaterium bacteriophage with elongated head.

Foi isolado do solo um fago de Bacillus megaterium, com aspecto morfologico anormal. Difere dos outros fagos de B. megaterium pela presenca de cabeca alongada, a semelhanca do fago BLE de B. licheniformis. Como outras caracteristicas analisadas neste fago apontou-se sensibilidade a temperatura de 60 graus C; resistencias ao cloroformio e luz ultra violeta e incapacidade de evidenciar placas de lise a 42 graus C. O fago esta constituido de ADN de dupla fita com um teor G-C de 34,7 a 36,7%

Characterization of phages of Bacillus subtilis isolated from Brazilian soils.

Quatorze fagos de Bacilus subtilis foram isolados de 5 solos diferentes e caracterizados quanto a morfologia e suas placas de lise, estabilidade a 4oC, microscopia eletronica, propriedades antigenicas, resistencia ao calor e quanto ao espectro de lise. O uso desses criterios permitiu que estes fagos fossem classificados em 7 grupos diferentes. O grupo maior consiste de 7 fagos estaveis, relativamente resistentes ao calor, sorologicamente relacionados entre si e pertencentes ao tipo B de Bradley. Todos os outros fagos isolados pertencem ao tipo A de Bradley. Oa fagos aqui descritos, sao comparados com fagos de B.subtilis anteriormente descritos

Constitutive erythromycin resistance plasmid in Staphylococcus aureus.

A plasmid with a molecular mass of 1.4 x 10(6) daltons has been identified in Staphylococcus aureus. This plasmid determines constitutive resistance to erythromycin and lincomycin and is the smallest naturally occurring element coding for antibiotic resistance in this species.

Loss of extrachromosomal resistances in Staphylococcus aureus by treatment with guanidine hydrochloride.

The addition of subinhibitory concentrations (optimal 1.8 mg ml-1) of guanidine hydrochloride to broth cultures of three strains of Staphylococcus aureus was followed by loss of penicillin and cadmium resistance. The proportion of sensitive variants, although variable, was higher than in untreated cultures. The 'penicillinase plasmid' was absent from two cultures sensitive to penicillin and cadmium. The genes for penicillinase production in one culture (13136) were apparently carried by a plasmid of 105 x 10(6) daltons.

Behavior of coliphage lambda in hybrids between Escherichia coli and Salmonella.

Salmonella typhosa hybrids able to adsorb lambda were obtained by mating S. typhosa recipients with Escherichia coli K-12 donors. After adsorption of wild-type lambda to these S. typhosa hybrids, no plaques or infective centers could be detected. E. coli K-12 gal(+) genes carried by the defective phage lambdadg were transduced to S. typhosa hybrids with HFT lysates derived from E. coli heterogenotes. The lysogenic state which resulted in the S. typhosa hybrids after gal(+) transduction differed from that of E. coli. Ability to produce lambda, initially present, was permanently segregated by transductants of the S. typhosa hybrid. S. typhosa lysogens did not lyse upon treatment for phage induction with mitomycin C, ultraviolet light, or heat in the case of thermoinducible lambda. A further difference in the behavior of lambda in Salmonella hybrids was the absence of zygotic induction of the prophage when transferred from E. coli K-12 donors to S. typhosa. A new lambda mutant class, capable of forming plaques on S. typhosa hybrids refractory to wild-type lambda, was isolated at low frequency by plating lambda on S. typhosa hybrid WR4254. Such mutants have been designated as lambdasx, and a mutant allele of lambdasx was located between the P and Q genes of the lambda chromosome. Plaques were formed also on the S. typhosa hybrid host with a series of lambda(i21) hybrid phages which contain the N gene of phage 21. The significance of these results in terms of Salmonella species as hosts for lambda is discussed.