Exploring Rhodospirillum rubrum response to high doses of carbon monoxide under light and dark conditions.

Environmental concerns about residues and the traditional disposal methods are driving the search for more environmentally conscious processes, such as pyrolysis and gasification. Their main final product is synthesis gas (syngas) composed of CO, CO2, H2, and methane. Syngas can be converted into various products using CO-tolerant microorganisms. Among them, Rhodospirillum rubrum is highlighted for its biotechnological potential. However, the extent to which high doses of CO affect its physiology is still opaque. For this reason, we have studied R. rubrum behavior under high levels of this gas (up to 2.5 bar), revealing a profound dependence on the presence or absence of light. In darkness, the key variable affected was the lag phase, where the highest levels of CO retarded growth to more than 20 days. Under light, R. rubrum ability to convert CO into CO2 and H2 depended on the presence of an additional carbon source, such as acetate. In those conditions where CO was completely exhausted, CO2 fixation was unblocked, leading to a diauxic growth. To enhance R. rubrum tolerance to CO in darkness, a UV-accelerated adaptive laboratory evolution (UVa-ALE) trial was conducted to isolate clones with shorter lag phases, resulting in the isolation of clones 1.4-2B and 1.7-2A. The adaptation of 1.4-2B was mainly based on mutated enzymes with a metabolic function, while 1.7-3A was mostly affected at regulatory genes, including the anti-repressor PpaA/AerR. Despite these mutations having slight effects on biomass and pigment levels, they successfully provoked a significant reduction in the lag phase (-50%). KEYPOINTS: • CO affects principally R. rubrum lag phase (darkness) and growth rate (light) • CO is converted to CO2/H2 during acetate uptake and inhibits CO2 fixation (light) • UVa-ALE clones showed a 50% reduction in the lag phase (darkness).

RrA, an enzyme from Rhodospirillum rubrum, is a prototype of a new family of short-chain L-asparaginases.

L-Asparaginases (ASNases) catalyze the hydrolysis of L-Asn to L-Asp and ammonia. Members of the ASNase family are used as drugs in the treatment of leukemia, as well as in the food industry. The protomers of bacterial ASNases typically contain 300-400 amino acids (typical class 1 ASNases). In contrast, the chain of ASNase from Rhodospirillum rubrum, reported here and referred to as RrA, consists of only 172 amino acid residues. RrA is homologous to the N-terminal domain of typical bacterial class 1 ASNases and exhibits millimolar affinity for L-Asn. In this study, we demonstrate that RrA belongs to a unique family of cytoplasmic, short-chain ASNases (scASNases). These proteins occupy a distinct region in the sequence space, separate from the regions typically assigned to class 1 ASNases. The scASNases are present in approximately 7% of eubacterial species, spanning diverse bacterial lineages. They seem to be significantly enriched in species that encode for more than one class 1 ASNase. Here, we report biochemical, biophysical, and structural properties of RrA, a member of scASNases family. Crystal structures of the wild-type RrA, both with and without bound L-Asp, as well as structures of several RrA mutants, reveal topologically unique tetramers. Moreover, the active site of one protomer is complemented by two residues (Tyr21 and Asn26) from another protomer. Upon closer inspection, these findings clearly outline scASNases as a stand-alone subfamily of ASNases that can catalyze the hydrolysis of L-Asn to L-Asp despite the lack of the C-terminal domain that is present in all ASNases described structurally to date.

Boosting hydrogen production in Rhodospirillum rubrum by syngas-driven photoheterotrophic adaptive evolution.

Rhodospirillum rubrum is a photosynthetic purple non-sulphur bacterium with great potential to be used for complex waste valorisation in biotechnological applications due to its metabolic versatility. This study investigates the production of hydrogen (H2) and polyhydroxyalkanoates (PHA) by R. rubrum from syngas under photoheterotrophic conditions. An adaptive laboratory evolution strategy (ALE) has been carried out to improve the yield of the process. After 200 generations, two evolved strains were selected that showed reduced lag phase and enhanced poly-3-hydroxybutyrate (PHB) and H2 synthesis compared to the parental strain. Genomic analysis of the photo-adapted (PA) variants showed four genes with single point mutations, including the photosynthesis gene expression regulator PpsR. The proteome of the variants suggested that the adapted variants overproduced H2 due to a more efficient CO oxidation through the CO-dehydrogenase enzyme complex and confirmed that energy acquisition was enhanced through overexpression of the photosynthetic system and metal cofactors essential for pigment biosynthesis.

The metabolic pathways of carbon assimilation and polyhydroxyalkanoate production by Rhodospirillum rubrum in response to different atmospheric fermentation.

The purple nonsulfur bacteria, Rhodospirillum rubrum, is recognized as a potential strain for PHAs bioindustrial processes since they can assimilate a broad range of carbon sources, such as syngas, to allow reduction of the production costs. In this study, we comparatively analyzed the biomass and PHA formation behaviors of R. rubrum under 100% CO and 50% CO gas atmosphere and found that pure CO promoted the PHA synthesis (PHA content up to 23.3% of the CDW). Hydrogen addition facilitated the uptake and utilization rates of CO and elevated 3-HV monomers content (molar proportion of 3-HV up to 9.2% in the presence of 50% H2). To elucidate the genetic events culminating in the CO assimilation process, we performed whole transcriptome analysis of R. rubrum grown under 100% CO or 50% CO using RNA sequencing. Transcriptomic analysis indicated different CO2 assimilation strategy was triggered by the presence of H2, where the CBB played a minor role. An increase in BCAA biosynthesis related gene abundance was observed under 50% CO condition. Furthermore, we detected the α-ketoglutarate (αKG) synthase, converting fumarate to αKG linked to the αKG-derived amino acids synthesis, and series of threonine-dependent isoleucine synthesis enzymes were significantly induced. Collectively, our results suggested that those amino acid synthesis pathways represented a key way for carbon assimilation and redox potential maintenance by R. rubrum growth under syngas condition, which could partly replace the PHA production and affect its monomer composition in copolymers. Finally, a fed-batch fermentation of the R. rubrum in a 3-l bioreactor was carried out and proved H2 addition indeed increased the PHA accumulation rate, yielding 20% ww-1 PHA production within six days.

Molecular structure and characterization of the Thermochromatium tepidum light-harvesting 1 photocomplex produced in a foreign host.

Purple phototrophic bacteria possess light-harvesting 1 and reaction center (LH1-RC) core complexes that play a key role in converting solar energy to chemical energy. High-resolution structures of LH1-RC and RC complexes have been intensively studied and have yielded critical insight into the architecture and interactions of their proteins, pigments, and cofactors. Nevertheless, a detailed picture of the structure and assembly of LH1-only complexes is lacking due to the intimate association between LH1 and the RC. To study the intrinsic properties and structure of an LH1-only complex, a genetic system was constructed to express the Thermochromatium (Tch.) tepidum LH1 complex heterologously in a modified Rhodospirillum rubrum mutant strain. The heterologously expressed Tch. tepidum LH1 complex was isolated in a pure form free of the RC and exhibited the characteristic absorption properties of Tch. tepidum. Cryo-EM structures of the LH1-only complexes revealed a closed circular ring consisting of either 14 or 15 αß-subunits, making it the smallest completely closed LH1 complex discovered thus far. Surprisingly, the Tch. tepidum LH1-only complex displayed even higher thermostability than that of the native LH1-RC complex. These results reveal previously unsuspected plasticity of the LH1 complex, provide new insights into the structure and assembly of the LH1-RC complex, and show how molecular genetics can be exploited to study membrane proteins from phototrophic organisms whose genetic manipulation is not yet possible.

Delayed allergic reaction to terbinafine with a positive lymphocyte transformation test

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Effects of extremely low frequency magnetic fields on hydrolysis of F0F1-ATPases and their relationship with turnover rates of F1 / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effects of extremely low frequency sinusoidal magnetic fields on hydrolysis of F(0)F(1)-ATPase and its mechanism.</p><p><b>METHODS</b>The F(0)F(1)-ATPases which was localized on the outer surface of chromatophores were prepared from the cells of Rhodospirillum rubrum and were exposed to 0.1 approximately 0.5 mT, 4.7 approximately 96.0 Hz magnetic fields.</p><p><b>RESULTS</b>The hydrolysis activity of F(0)F(1)-ATPase was stimulated by 0.5 mT, 4.7, 12.0, 60.0, 72.0, 84.0 and 96.0 Hz magnetic fields respectively and inhibited by 0.5 mT, 24.0 Hz magnetic field (P < 0.05); 0.3 mT, 4.7, 24.0 and 60.0 Hz magnetic fields also distinctly affected F(0)F(1)-ATPases activity respectively (P < 0.05), whereas 0.1 mT exposure caused no significant changes on that activity. When the hydrolysis activity of the F(0)F(1)-ATPases was inactivated by its inhibitor DCCD, the 0.5 mT, 24.0 Hz magnetic field still inhibited the hydrolysis activity of the F(0)F(1)-ATPase and 0.5 mT, 60.0 Hz magnetic field also had stimulating effects (P < 0.05).</p><p><b>CONCLUSION</b>The effects of magnetic fields on the hydrolysis activity of the F(0)F(1)-ATPases depend on not only magnetic frequency but also magnetic intensity. The threshold of magnetic intensity is between 0.1 mT and 0.3 mT. F(0)F(1)-ATPases, especially F1-portion may be an end-point of magnetic fields.</p>

Frecuencia y etiología de la dermatofitosis en niños de entre 0 y 12 años en el estado de Amazonas, Brasil / Frequency and aetiology of dermatophytosis in children age 12 and under in the state of Amazonas, Brazil

Antecedentes. Apenas se dispone de estudios científicos que hayan investigado las dermatofitosis en niños que viven en el estado de Amazonas o en la región más septentrional de Brasil. Objetivos. El objetivo de este estudio fue investigar la frecuencia y la etiología de las dermatofitosis en niños de 12 años de edad o menores, que fueron examinados entre marzo de 1996 y noviembre de 2005 en el Laboratorio de Micología del Instituto Nacional de Investigaciones de Amazonia. Métodos. Para el diagnóstico micológico, se utilizaron muestras de escamas epidérmicas y/o cabello. Una parte de la muestra se trasladó a un portaobjetos y se añadió una solución de hidróxido de potasio para examen microscópico directo. La otra parte de la muestra se sembró en medio de cultivo (Mycobiotic Agar) para el aislamiento de los dermatofitos. Resultados. De las 590 muestras analizadas, en 210 se aislaron dermatofitos mediante examen microscópico directo y cultivo. La tiña del cuero cabelludo (153 casos) fue la dermatofitosis más frecuente, y Trichophyton tonsurans (121 casos) fue el patógeno aislado más habitual. En 48 casos se detectó tiña corporal, siendo también T. tonsurans el hongo aislado más frecuente (17 casos), y las regiones corporales más afectadas fueron la cara, extremidades superiores y tronco. El laboratorio confirmó un pie de atleta en 6 casos y los principales hongos aislados fueron Trichophyton rubrum (3) y Trichophyton mentagrophytes (3). La tiña crural solo se confirmó en 3 casos, en los que se aislaron T. rubrum, T. tonsurans y Epidermophyton floccosum. Conclusiones. En los niños examinados, la tiña del cuero cabelludo fue la afectación principal y el patógeno responsable de estas dermatofitosis fue T. tonsurans(AU)

Background. Few scientific studies have evaluated dermatophytosis among children in the state of Amazonas or in the greater northern region of Brazil. Aims. The aim of this study was to research the frequency and aetiology of dermatophytosis in children age 12 and under, who were seen between March 1996 and November 2005 at the Mycology Laboratory of the National Institute of Amazonian Research. Methods. For mycological diagnoses, epidermal scales and/or hairs were used. A portion of this material was treated with potassium hydroxide for direct examination, and another portion was cultivated in Mycobiotic Agar for the isolation of dermatophytes. Results. Of the 590 samples analysed, 210 showed positive diagnoses by direct examination and cultivation. Tinea capitis (153 cases) was the most frequent type of dermatophytosis, and Trichophyton tonsurans (121 cases) was the most frequently isolated fungal agent. Tinea corporis was observed in 48 cases where the most frequently isolated fungal agent was also T. tonsurans (17 cases), and the corporal regions most affected were the face, arms and trunk. The laboratory confirmed tinea pedis in 6 cases, and the principal fungal agents isolated were Trichophyton rubrum (3) and Trichophyton mentagrophytes (3). The presence of tinea cruris was confirmed in 3 cases, and T. rubrum, T. tonsurans and Epidermophyton floccosum were isolated from these cases. Conclusions. The children examined were primarily affected by tinea capitis, and the main fungal agent for this dermatophytosis was T. tonsurans(AU)

Trichophyton rubrum como agente etiológico de un caso de Querion de Celso / Trycophyton rubrum as a causal agent in a case of Celso´s Kerion

Introducción. El querion de Celso, típico de la infancia, es una forma de presentación inflamatoria de la tiña del cuero cabelludo. Se trata de una lesión inflamatoria en placa, habitualmente única, sobreelevada, bien delimitada y de tamaño variable. Se manifiesta como eritema, edema y formación de costras. Contiene pústulas en su interior y está cubierta de pelos fracturados que se desprenden con facilidad. Suele cursar sin afectación del estado general ni fiebre. Normalmente se acompaña de adenopatías retroauriculares i laterocervicales dolorosas. Tricophyton rubrum com a agent etiològic d’un cas de quèrion de Cels Cinta Rosa Gas-Colomé, Sara Hernàndez-Luque, Antoni Soriano-Arandes, Frederic Gómez-Bertomeu Servei de Pediatria. Hospital Universitari Joan XXIII. Tarragona Caso clínico. Paciente de 8 años que presenta lesión en placa, exudativa, en región parietal izquierda, de 5 días de evolución. No refiere fiebre ni otra sintomatología sistémica acompañante. Se orienta el caso como querion de Celso, confirmado por estudios micológicos. Se inicia tratamiento antifúngico con griseofulvina, con buena respuesta. Comentario. Los dermatofitos más frecuentes causantes de querion de Celso en nuestro medio son Tricophyton mentagrophytes y Microsporum canis. Menos frecuentemente, entre el género Tricophyton podemos encontrar T. tonsurans, T. rubrum, T. verrucosum y T. violaceum, y entre el género Microsporum podemos encontrar M. gipseum, entre otros. El diagnóstico se obtiene fundamentalmente a través de la tinción KOH y el cultivo en medio Sabouraud; éste último identificará la especie. Las primeras líneas terapéuticas son la griseofulvina micronizada a dosis entre 10 y 20 mg/kg/día, la terbinafina a dosis de 2,5 mg/kg/día i el itraconazol a dosis de 5 mg/kg/día. El tratamiento se deberá instaurar cuanto antes, para así minimizar las secuelas(AU)

Introduction. Celso’s kerion, typical in childhood, is a form of inflammatory presentation of ringworm of the scalp. This is an inflammatory lesion in the form of a plaque, normally a single one (although it can be multiple), raised, well outlined, and of variable size. It manifests as erythema, oedema, and the formation of scabs. It has pustules inside, and is covered by fractured hairs that detach easily. It tends to run its course without affecting the general condition or causing fever. It is normally accompanied by swollen lymph nodes behind the ears and pain on the sides of the cervical vertebrae. Clinical case. 8-year-old patient who presented with a painful plaque lesion, exudative, in the left parietal region, with 5 days of evolution. There was no fever or other accompanying systemic symptoms. The case was oriented as Celso’s kerion, and the presence of Trichophyton rubrum was determined in the fungal culture. Fungicidal treatment was given with oral griseofulvin, with a good response. Comment. Celso’s kerion is mainly caused by Trichophyton mentagrophytes, Trichophyton tonsurans and Microsporumn canis. Trichophyton rubrum as a causal agent responsible for these clinical symptoms is exceptional. The diagnosis is fundamentally obtained by way of direct microscopic observation with KOH and a culture in Sabouraud agar, DTM (dermatophyte test medium) or others. The first therapeutic lines are micronized Griseofulvin at a dosage of 10 to 20 mg/kg/day, terbinafine at a dosage of 2.5 mg/kg/day, and itraconazole at a dosage of 5 mg/kg/day. The treatment must be started as soon as possible to minimise the sequelas(AU)