Hypervirulent and hypermucoviscous extended-spectrum ß-lactamase-producing Klebsiella pneumoniae and Klebsiella variicola in Chile.

Convergence of virulence and antibiotic-resistance has been reported in Klebsiella pneumoniae, but not in Klebsiella variicola. We, hereby, report the detection and genomic characterization of hypervirulent and hypermucoviscous K. pneumoniae and K.variicola recovered in Chile from health-care associated infections, which displayed resistance to broad-spectrum cephalosporins. One hundred forty-six K. pneumoniae complex isolates were screened by hypermucoviscosity by the "string test." Two hypermucoid isolates, one hypermucoviscous K. pneumoniae (hmKp) and one K. variicola (hmKv), were further investigated by whole-genome sequencing. In vivo virulence was analyzed by the Galleria mellonella killing assay. In silico analysis of hmKp UCO-494 and hmKv UCO-495 revealed the presence of multiple antibiotic-resistance genes, such as blaCTX-M-1, blaDHA-1 and blaLEN-25 among others clinically relevant resistance determinants, including mutations in a two-component regulatory system related to colistin resistance. These genetic features confer a multidrug-resistant (MDR) phenotype in both strains. Moreover, virulome in silico analysis confirmed the presence of the aerobactin gene iutA, in addition to yersiniabactin and/or colicin V encoding genes, which are normally associated to high virulence in humans. Furthermore, both isolates were able to kill G. mellonella and displayed higher virulence in comparison with the control strain. In summary, the convergence of virulence and the MDR-phenotype in K. pneumoniae complex members is reported for the first time in Chile, denoting a clinical problem that deserves special attention and continuous surveillance in South America.

Molecular diversity of Staphylococcus aureus and the role of milking equipment adherences or biofilm as a source for bulk tank milk contamination.

Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on milking equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus-containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.

Occurrence of antibiotics and bacterial resistance in wastewater and sea water from the Antarctic.

The potential presence of introduced antibiotics in the aquatic environment is a hot topic of concern, particularly in the Antarctic, a highly vulnerable area protected under the Madrid protocol. The increasing presence of human population, especially during summer, might led to the appearance of pharmaceuticals in wastewater. The previous discovery of Escherichia coli strains resistant to antibiotics in sea water and wastewater collected in King George Island motivated our investigation on antibiotics occurrence in these samples. The application of a multi-residue LCMS/MS method for 20 antibiotics, revealed the presence of 8 compounds in treated wastewater, mainly the quinolones ciprofloxacin and norfloxacin (92% and 54% of the samples analyzed, average concentrations 0.89 µg/L and 0.75 µg/L, respectively) and the macrolides azithromycin and clarithromycin (15% positive samples, and average concentrations near 0.4 µg/L), and erythromycin (38% positive samples, average concentration 0.003 µg/L). Metronidazole and clindamycin were found in one sample, at 0.17 and 0.1 µg/L, respectively; and trimethoprim in two samples, at 0.001 µg/L. Analysis of sea water collected near the outfall of the wastewater discharges also showed the sporadic presence of 3 antibiotics (ciprofloxacin, clindamycin, trimethoprim) at low ng/L level, illustrating the impact of pharmaceuticals consumption and the poor removal of these compounds in conventional WWTPs. The most widespread antibiotic in sea water was ciprofloxacin, which was found in 15 out of 34 sea water samples analyzed, at concentrations ranging from 4 to 218 ng/L. Bacteria resistance was observed for some antibiotics identified in the samples (e.g. trimetropim and nalidixic acid -a first generation quinolone). However, resistance to some groups of antibiotics could not be correlated to their presence in the water samples due to analytical limitations (penicillins, tetraciclines). On the contrary, for some groups of antibiotics detected in samples (macrolides), the antibacterial activity against E. Coli was not investigated because these antibiotics do not include this bacterial species in their spectrum of activity. Our preliminary data demonstrate that antibiotics occurrence in the Antarctic aquatic environment is an issue that needs to be properly addressed. Periodical monitoring of water samples and the implementation of additional treatments in the WWTPs are recommended as a first step to prevent potential problems related to the presence of antibiotics and other emerging contaminants in the near future in Antarctica.

Metagenomic study of bacterial microbiota in persistent endodontic infections using Next-generation sequencing.

AIM: To determine the bacterial microbiota in root canals associated with persistent apical periodontitis and their relationship with the clinical characteristics of patients using next-generation sequencing (NGS). METHODOLOGY: Bacterial samples from root canals associated with teeth having persistent apical periodontitis were taken from 24 patients undergoing root canal retreatment. Bacterial DNA was extracted, and V3-V4 variable regions of the 16S rRNA gene were amplified. The amplification was deep sequenced by Illumina technology to establish the metagenetic relationships among the bacterial species identified. The composition and diversity of microbial communities in the root canal and their relationships with clinical features were analysed. Parametric and nonparametric tests were used to analyse differences between patient characteristics and microbial data. RESULTS: A total of 86 different operational taxonomic units (OTUs) were identified and Good's nonparametric coverage estimator method indicated that 99.9 ± 0.00001% diversity was recovered per sample. The largest number of bacteria belonged to the phylum Proteobacteria. According to the medical history from the American Society of Anesthesiologists (ASA) Classification System, ASA II-III had higher richness estimates and distinct phylogenetic relationships compared to ASA I individuals (P < 0.05). Periapical index (PAI) score 5 was associated with increased microbiota diversity in comparison to PAI score 4, and this index was reduced in symptomatic patients. CONCLUSIONS: Based on the findings of this study, it is possible to suggest a close relationship between several clinical features and greater microbiota diversity with persistent endodontic infections. This work provides a better understanding on how microbial communities interact with their host and vice versa.

Synthesis of Copper Nanowires and Their Antimicrobial Activity on Strains Isolated Persistent Endodontic Infections.

Copper nanowires, Cu-NWs may have a good antimicrobial effect in endodontic treatment. The objective of this work was to synthesize, characterize and evaluate the antibacterial activity of Cu-NWs on strains obtained from human root canal. A wide distribution of Cu-NWs diameters from 30 to 90 nm was obtained with lengths ranging from 5 to 40 µm. Structural analysis of Cu-NWs showed crystalline planes, which corresponded to Cu, with preferential growth in the direction [110]. The geometric mean MICs was of 289.30 µg/mL, with a MIC50 of 256 µg/mL and a MIC90 of 512 µg/mL for Cu-NWs. Cellular viability of 28 a biofilm tends to decrease the longer it is exposed to Cu-NWs. Synthesized and characterized Cu-NWs have a good antimicrobial effect against clinical strains used in the present study and has a potential to be used for disinfection of the root canal system.

Sistema de Apoyo para la Cuantificación Semiautomática de Fibrosis Pulmonar en Imágenes de TAC / Support System for Semiautomatic Quantification of Pulmonary Fibrosis in CT Images

Resumen: En este trabajo se presenta un método para calcular los niveles de fibrosis pulmonar en imágenes de tomografía axial computarizada. Se utilizó un algoritmo de segmentación semiautomática basado en el método de Chan-Vese. El método mostró similitudes de forma cualitativa en la región de la fibrosis con respecto al experto clínico. Sin embargo es necesario validar los resultados con una base de datos mayor. El método propuesto aproxima un porcentaje de fibrosis de forma fácil para apoyar su implementación en la práctica clínica minimizando la subjetividad del experto médico y generando una estimación cuantitativa de la región de fibrosis.

Abstract: A method to estimate the pulmonary fibrosis in computed tomography (CT) imaging is presented. A semi-automatic segmentation algorithm based on the Chan-Vese method was used. The proposed method shows a similar fibrosis región with respect to clinical expert. However, the results need to be validated in a bigger data base. The proposed method approximates a fibrosis percentage that allows to achieve this procedure easily in order to support its implementation in the clinical practice minimizing the clinical expert subjectivity and generating a quantitative estimation of fibrosis region.

Acoustic evaluation of pirfenidone on patients with combined pulmonary fibrosis emphysema syndrome.

The combined pulmonary fibrosis emphysema syndrome (CPFES) overall has a poor prognosis with a 5-year survival of 35-80%. Consequently, to evaluate possible positive effects on patients of novel agents as pirfenidone is relevant. However, the efficacy of pirfenidone in CPFES patients is still not well-known. In this study we propose an alternative to evaluate the effects of pirfenidone treatment on CPFES patients via acoustic information. Quantitative analysis of discontinuous adventitious lung sounds (DLS), known as crackles, has been promising to detect and characterize diverse pulmonary pathologies. The present study combines independent components (ICs) analysis of LS and the automated selection of ICs associated with DLS. ICs's features as fractal dimension, entropy and sparsity produce several clusters by kmeans. Those clusters containing ICs of DLS are exclusively considered to finally estimate the number of DLS per ICs by a time-variant AR modeling. For the evaluation of the effects of pirfenidone, the 2D DLS-ICs spatial distribution in conjunction with the estimated number of DLS events are shown. The methodology is applied to two real cases of CPFES with 6 and 12 months of treatment. The acoustical evaluation indicates that pirfenidone treatment may not be satisfactory for CPFES patients but further evaluation has to be performed.

Carbon disulfide formation in papaya under conditions of dithiocarbamate residue analysis.

Golden, Sunrise Solo and Tainung cultivars of papaya were found to release CS2 when submitted to experimental conditions of dithiocarbamate residue analysis. Three common analytical methods were used to quantitate CS2; one spectrophotometric method and two chromatographic methods. All three methods gave positive CS2 results for all three papaya varieties. Other endogenous compounds present in isooctane extracts of papaya fractions detected via gas chromatography (GC/ITD) using electron ionization (EI) were: carbonyl sulfide, dimethyl sulfide, carbon disulfide, 2-methylthiophene, 3-methylthiophene, 2-ethylthiophene, 3-ethylthiophene, benzylisothiocyanate, benzylthiocyanate and benzonitrile. Control samples were obtained from papaya plantations cultivated in experimental areas, in which no treatment with fungicides of the dithiocarbamate group was applied. Endogenous CS2 levels were compared with true dithiocarbamate residues measured in papaya samples from the field trials following applications of the mancozeb fungicide. Three days after application, true dithiocarbamate residues, measured by the procedure with isooctane partitioning and GC-ITD, were at the average level of 2 mg kg(-1).

Vaginosis bacteriana en estudiantes universitarias de Antofagasta / BacteriaI vaginosis in university students of Antofagasta

The bacterial vaginosis (VE) is a clinical entity that one has proposed as sexually transmitted disease (ETS), which still is in discussion, provided that the principal agents etiologic (Gardnerella vaginalis and Mobiluncus spp), also are a part of the normal vaginal flora. VE's prevalence was investigated according to the Nugent's microbiological and Amsel's clinical criteria between 190 university students of Antofagasta city who consult spontaneously, during April and October, 2006. Other agents (bacteria, fungi and parasites) isolated of the vaginal secretion were diagnosed by means of standardized methods. One found a prevalence of 19% (36/190) of VE and 38% (72/190) of other pathologies: Candida albicans 76% (55/72); bacteria, predominating over Enterobacteriaceas 15% (21/72) and Trichomonas vaginalis 3% (2/72). One concludes that the high indicators of VE and other infectious pathologies of ETS's type in this group of women who begin in the sexual activity it needs of major educational support, special1y the related ones to the entity bacterial vaginosis, who still is not very frequently studied in these groups.

La vaginosis bacteriana (VB) es una entidad clínica que se ha propuesto como enfermedad de transmisión sexual (ETS), lo cual aún está en discusión, dado que los principales agentes etiológicos (Gardnerella vaginalis y Mobiluncus spp), también son parte de la flora normal vaginal. Se investigó la prevalencia de VB, según los criterios microbiológico de Nugent y clínico de Amsel en 190 estudiantes universitarias de la ciudad de Antofagasta que consultan espontáneamente, durante abril y octubre del 2006. Otros agentes patógenos (bacterias, hongos y parásitos) aislados de la secreción vaginal fueron diagnosticados mediante técnicas estandarizadas. Se encontró una prevalencia del 19% (36/190) de VB y 38% (72/190) de otras patologías causadas por: Candida albicans 76% (55/72); bacterias, predominando Enterobacteriaceas 15% (21/72); Y Trichomonas vaginalis 3% (2/72). Se concluye que los elevados indicadores de VB y de otras patologías infecciosas del tipo de las ETS, en este grupo de mujeres que se inician en la actividad sexual, requiere de mayor apoyo educativo y profiláctico, especialmente las relacionadas con la entidad vaginosis bacteriana, la cual aún no es muy frecuentemente estudiada en estos grupos etarios.

A phase I clinical trial of a multi-epitope polypeptide TAB9 combined with Montanide ISA 720 adjuvant in non-HIV-1 infected human volunteers.

A phase I clinical trial was performed to examine the safety and immunogenicity of a multi-epitope polypeptide comprising the central 15 amino acids of the V3 loop from six HIV-1 isolates. This protein called TAB9 was emulsified in Montanide ISA720 (Seppic, Paris) and administered intramuscularly at doses of 0, 0.2 and 1 mg to 24 healthy, HIV-1 seronegative adult males. Three immunisations were given at months 0, 1 and 6 in a randomised, double blind, placebo controlled clinical trial. The placebo was generally well tolerated. However, severe local reactions were observed in TAB9 vaccinated subjects after the second and third inoculations. Seven out of eight volunteers from the lower dose group showed moderate or severe local inflammation, while four out of eight subjects from the higher dose group developed granulomas and sterile abscesses. In general, the reactogenicity depended on the number of inoculations given and the dose of TAB9. Both doses were immunogenic, all immunised volunteers seroconverted and antibodies were broadly reactive against the V3 peptides included in the protein. All vaccine's sera reacted against gp120 in Western blot and 50% of them also neutralised at least one out of five laboratory isolates tested. No differences between doses were found. Anti TAB9 lymphoproliferative responses were observed, being more intense in the high dose group. Due to the strong local reactions that were found in this study, a change in the formulation will be required for further trials with this vaccine candidate in humans.

[Semont maneuver and vestibular rehabilitation exercises in the treatment of benign paroxysmal postural vertigo. A comparative study]. / Maniobra de Semont y ejercicios de rehabilitación vestibular en el tratamiento del vértigo postural paroxístico benigno. Estudio comparativo.

BACKGROUND: Benign paraoxysmal postural vertigo (BPPV) is one of the most frequent causes of peripheral dizziness. Treatment based on vestibular rehabilitation exercises (VRE) is effective in 90% of the cases in an interval of 3 to 4 weeks. This treatment however is often abandoned by the patient. The only therapeutic maneuvers (based on otolyte release) are equally effective but present a high medium term recurrence. AIM: To compare the efficacy of the Semont maneuver (SM), the VRE and the combination of both in the treatment of BPPV at three months of follow up. MATERIAL AND METHODS: Forty patients with the clinical and electronystagmographic diagnosis of BPPV were divided into three groups: 1. SM, 2. VRE and 3. SM + VRE. The results were compared in regard to the signs and symptoms observed in the three groups of patients at 15 days, one month and at three months of treatment. RESULTS: The SM was effective in 80% of the patients at 15 days of treatment versus 45% of those receiving only VRE. The third group of patients, receiving the combined treatment, demonstrated a cure in 100% of the cases when evaluated at three months while only 66% of the SM group were found to be asymptomatic at the same time period (p < 0.05). CONCLUSIONS: The SM is easy to perform, rapid and effective in the short term, however has high recurrence. The VRE are effective in the long term based on the patient persistence. Combination of the two treatment leads to symptom remission in 100% of the patients at three months of treatment.

Maniobra de semont y ejercicios de rehabilitación vestibular en el tratamiento del vértigo postural paroxístico benigno. estudio comparativo / Semont maneuver and vestibular rehabilitation exercises in the treatment of benign paroxysmal postural vertigo. A comparative study

Fundamento: El vértigo postural paroxístico benigno (VPPB) es una de las causas más frecuentes de vértigo periférico. El tratamiento con ejercicios de rehabilitación vestibular (ERV) es efectivo en el 90 por ciento de los casos en un intervalo de 3 a 4 semanas; sin embargo, frecuentemente es abandonado por el paciente. Las maniobras terapéuticas únicas (basadas en la liberación de otolitos) son igualmente efectivas pero presentan alta recurrencia a medio plazo. Objetivo: Comparar la eficacia de la maniobra de Semont (MS), los ERV y la combinación de ambos en el tratamiento del VPPB a los 3 meses de seguimiento. Material y métodos: Se estudiaron 40 pacientes con el diagnóstico clínico y electronistagmográfico de VPPB divididos en 3 grupos: I MS, II ERV y III MS + ERV. Se compararon los resultados en cuanto a síntomas y signos observados en los tres grupos a los 15 días, al mes y a los 3 meses de tratamiento. Resultados: La MS fue eficaz en el 80 por ciento de los pacientes a los 15 días de tratamiento frente al 45 por ciento de los que recibieron únicamente ERV. El grupo de pacientes sometidos a ambos tratamientos se curó en el 100 por ciento de los casos valorados a los 3 meses, mientras que sólo el 66 por ciento del grupo de MS se encontraron asintomáticos en el mismo período de tiempo (p < 0,05). Conclusiones: La MS es fácil de realizar, rápida y eficaz a corto plazo; sin embargo, cursa con alta recurrencia. Los ERV son efectivos a largo plazo, en función de la persistencia del paciente. Combinar ambos tratamientos lleva a la remisión de los síntomas en el 100 por ciento de los pacientes a los 3 meses de tratamiento (AU)

[Acute myeloid leukemia in the adult. Results of the National Antineoplastic Drug Protocol at the Hospital del Salvador, 1990-1998]. / Leucemia mieloide aguda del adulto. Resultados del Protocolo Nacional de Drogas Antineoplásica. Hospital del Salvador 1990-1998.

BACKGROUND: The incidence of acute myeloid leukemia is 3 cases per 100,000 inhabitants/year and its five years event free survival is 15 to 20%. Since the incorporation of trans retinoic acid, event free survival of M3 acute myeloid leukemia is 80%. AIM: To report the results of acute myeloid leukemia treatment at the Hospital del Salvador, between 1990 and 1998. PATIENTS AND METHODS: The medical records of 117 patients (66 female, mean age 48.2 years), treated between 1990 and 1998 using PANDA protocol, were retrospectively reviewed. Immunophenotyping was done in 69 patients and cytogenetic studies were done in 65. RESULTS: Sixteen percent of patients had M3 acute myeloid leukemia. The most frequent phenotype was the association of DR, CD34 plus a panmyeloid marker. DR and CD34 were negative in seven of nine patients with M3 acute myeloid leukemia. Cariotype was abnormal in 78% of patients. Complete remission was achieved in 65% of cases with a 13% of failures. Early mortality was 21.3% and decreased to 6.1% in the last three years. Infections and coagulation disorders were the main causes of death. Mean survival was 10.5 months. Five years event free survival was 11%. In M3 acute myeloid leukemia, the figure is 50%. CONCLUSIONS: Treatment results are less effective than protocols that consider more aggressive chemotherapeutic protocols or bone marrow transplantation. The reduction in early mortality is due to a better management of febrile neutropenia.

Molecular cloning, sequencing, and expression of a chemoreceptor gene from Leptospirillum ferrooxidans.

We have cloned and sequenced a 2,262-bp chromosomal DNA fragment from the chemolithoautotrophic acidophilic bacterium Leptospirillum ferrooxidans. This DNA contained an open reading frame for a 577-amino-acid protein showing several characteristics of the bacterial chemoreceptors and, therefore, we named this gene lcrI for Leptospirillum chemotaxis receptor I. This is the first sequence reported for a gene from L. ferrooxidans encoding a protein. The lcrI gene showed both sigma 28-like and sigma 70-like putative promoters. The LcrI deduced protein contained two hydrophobic regions most likely corresponding to the two transmembrane regions present in all of the methyl-accepting chemotaxis proteins (MCPs) which make them fold with both periplasmic and cytoplasmic domains. We have proposed a cytoplasmic domain for LcrI, which also contains the highly conserved domain (HCD region), present in all of the chemotactic receptors, and two probable methylation sites. The in vitro expression of a DNA plasmid containing the 2,262-bp fragment showed the synthesis of a 58-kDa protein which was immunoprecipitated by antibodies against the Tar protein (an MCP from Escherichia coli), confirming some degree of antigenic conservation. In addition, this 58-kDa protein was expressed in E. coli, being associated with its cytoplasmic membrane fraction. It was not possible to determine a chemotactic receptor function for LcrI expressed in E. coli. This was most likely due to the fact that the periplasmic pH of E. coli, which differs by 3 to 4 pH units from that of acidophilic chemolithotrophs, does not allow the right conformation for the LcrI periplasmic domain.

Defective neutrophil function in workers occupationally exposed to hexachlorobenzene.

In this work we have studied the respiratory burst and chemotaxis of polymorphonuclear leukocytes from 51 workers exposed to chlorinated compounds, which were compared with those of non-exposed, age- and sex-matched individuals. These two neutrophil functions were significantly reduced as compared to controls. No correlation was observed between the length of exposure, hexachlorobenzene (HCB) blood concentrations and neutrophil chemotaxis or the extent of nitroblue tetrazolium reduction.

BiP is a substrate for src kinase in vitro.

In a study to investigate the ability of chaperones to modulate src kinase activity, it was observed that BiP, a member of the HSP70 family found in the endoplasmic reticulum, is an excellent substrate for src kinase in vitro. The reaction requires polylysine and the results suggest that two tyrosine residues are phosphorylated. Although there is no evidence for this reaction in vivo, it does provide a very efficient method to label BiP.

Dissociation of glucose-regulated protein Grp78 and Grp78-IgE Fc complexes by ATP.

Recent studies have shown that ATP can dissociate dimers of the glucose-regulated protein Grp78 to monomers. In the present study, we have used purified recombinant Grp78 from Escherichia coli to investigate this reaction in more detail. During the course of the Grp78 dimer-monomer conversion, a stable Grp78 monomer-ATP complex is formed. Upon removal of the ATP, the Grp78 dimer is reformed. ADP, nonhydrolyzable ATP analogues, and GTP do not effect the dissociation of Grp78 dimers. A cell line that overproduces IgE Fc has been used to examine the nature of the Grp78-IgE Fc complexes present and the effect of ATP on them. Grp78-IgE Fc complexes ranging from 100 kDa to 300 kDa were observed by sucrose gradient analysis, suggesting that aggregate forms of Grp78 may be present in some of these complexes. Treatment of the extracts with ATP resulted in release of a Grp78 monomer from the complex. These results suggest that the dissociation of Grp78 oligomers by ATP may be involved in the function of Grp78 in protein translocation through the endoplasmic reticulum.

Chemotaxis of Leptospirillum ferrooxidans and other acidophilic chemolithotrophs: comparison with the Escherichia coli chemosensory system.

Ni2+, Fe2+ and Cu2+ were attractants and aspartate was an apparent repellent for Leptospirillum ferrooxidans, a behaviour opposite to that for Escherichia coli. Membranes from L. ferrooxidans contained proteins with a molecular mass in the range of 80 kDa which were methylated in vitro. Methylation was stimulated in the presence of a membrane-free extract from E. coli, showing the response pattern expected for L. ferrooxidans, increased methylation by Ni2+, and demethylation by aspartate. This suggests the existence of sensory transducers having a common methylation domain with the E. coli methyl-accepting chemotaxis proteins. Total chromosomal DNA digests from L. ferrooxidans, Thiobacillus ferrooxidans and T. thiooxidans hybridized with probes containing different domains of the tar gene from E. coli, implying the presence of tar type genes in the acidophilic bacteria studied.