1,721,025 research outputs found
Some facts about the respiratory enzymes of Pseudomonas pseudoalcaligenes KF707 recently renamed as Pseudomonas furukawaii sp. nov., type strain KF707
No full textRecently proposed renaming the obligate aerobe Pseudomonas pseudoalcaligenes KF707 as Pseudomonas furukawiisp. nov. type strain KF707. Since the first quasi-complete genome sequence of KF707 was reported in 2012 (accession number: PRJNA83639) numerous reports on chemotaxis and function/composition of the respiratory redox chain of KF707 have been published, demonstrating that KF707 contains three cheA genes for aerobic motility, four cytochrome oxidases of c(c)aa3- and cbb3-type and one bd-type quinol oxidase. With this background in mind, it has been quite a surprise to read within Table 1 of the paper by Kimura et al. that strain KF707 is phenotypically characterized as cytochrome oxidase-negative. Further, Table 1 also reports that KF707 is b-galactosidase-positive, an affirmation that is not consistent with results documented in the current literature. In this present ‘Letter to the Editor’ we show that Kimura et al. have contradicted themselves and provided inaccurate information in respect to the respiratory phenotypic features of P. furukawii
Characterization of methanotrophic microbial community in a soil sample from Terre Calde di Medolla (Italy)
No full textMethane-oxidizing bacteria (methanotrophs) have a ubiquitous distribution in the environment and play an important role in global climate warming by lowering methane emission into the atmosphere. “Terre Calde di Medolla” (literally, “Warm Earths of Medolla”) refers to a farming area, located near the town of Modena (Emilia-Romagna region, northern Italy), which has always been known for the relatively high temperatures of the soil. After the 2012 Emilia earthquake that affected this area, soil temperatures of 44°C were revealed (20–25°C above the local background value) together with diffuse soil fluxes of methane (CH4) and minor, though significant, of carbon dioxide (CO2). Ground heating and gas seepage appeared to be spatially correlated, thus suggesting a close relationship between the two phenomena.The aim of this work was to characterize the methanotrophic microbial community present in soil samples collected from this area using a cultivation-independent approach. We performed clone library analysis and terminal restriction fragment length polymorphism (T-RFLP) fingerprinting of the 16S rDNA and pmoA gene (coding for the alpha-subunit of the particulate methane monooxygenase). Results from 16S rDNA analysis showed that methanotrophic bacteria represented around 10% of the entire microbial community. In particular, bacteria belonging to Acidobacteria and Actinobacteria phyla were detected as well as members of Ammonifex, Sphingomonas and Bacillus genera.
Through the analysis of pmoA gene, Methylococcus, Methylocaldum and Methylomonas were found to be the dominant genera (around 90%) of the methanotrophic community under analysis. In addition to these Gammaproteobacteria, Methylocystis spp. were detected which belong to Alphaproteobacteria class. Further studies will define the correlation between the composition and the role of the methanotrophic microbial community and the peculiar characteristics of “Terre Calde di Medolla” soil
Diversity of methane-oxidizing bacteria in soils from “hot lands of medolla” (Italy) featured by anomalous high-temperatures and biogenic CO2 emission
Full text link“Terre Calde di Medolla” (TCM) (literally, “Hot Lands of Medolla”) refers to a farming area in Italy with anomalously high temperatures and diffuse emissions of biogenic CO2, which has been linked to CH4 oxidation processes from a depth of 0.7 m to the surface. We herein assessed the composition of the total bacterial community and diversity of methane-oxidizing bacteria (MOB) in soil samples collected at a depth at which the peak temperature was detected (0.6 m). Cultivation independent methods were used, such as: i) a clone library analysis of the 16S rRNA gene and pmoA (coding for the α-subunit of the particulate methane monooxygenase) gene, and ii) Terminal Restriction Fragment Length Polymorphism (T-RFLP) fingerprinting. The 16S rRNA gene analysis assessed the predominance of Actinobacteria, Acidobacteria, Proteobacteria, and Bacillus in TCM samples collected at a depth of 0.6 m along with the presence of methanotrophs (Methylocaldum and Methylobacter) and methylotrophs (Methylobacillus). The phylogenetic analysis of pmoA sequences showed the presence of MOB affiliated with Methylomonas, Methylocystis, Methylococcus, and Methylocaldum in addition to as yet uncultivated and uncharacterized methanotrophs. Jaccard’s analysis of T-RFLP profiles at different ground depths revealed a similar MOB composition in soil samples at depths of 0.6 m and 0.7 m, while this similarity was weaker between these samples and those taken at a depth of 2.5 m, in which the genus Methylocaldum was absent. These results correlate the anomalously high temperatures of the farming area of “Terre Calde di Medolla” with the presence of microbial methane-oxidizing bacteria
Degradation of Alkanes in Rhodococcus
No full textAlkanes are widely distributed in the environment as they not only constitute the large fraction of crude oil but are also produced by many living organisms. They are saturated hydrocarbons of different sizes and structures, which pose a variety of challenges to degradative microorganisms due to their physicochemical properties, i.e., the extremely limited solubility and the high energy required for activation. The hydrophobic cell surface of Rhodococcus spp., the ability to produce biosurfactants, and the possession of a wide range of oxygenases allow coping with such challenges. In particular, monooxygenase enzymes are involved in the activation of alkanes by converting them into alcohols, which undergo a series of oxidation steps before being converted to fatty acids. Rhodococcus alkane monooxygenases belong to different families (i.e., AlkB-like monooxygenase, soluble di-iron monooxygenase, cytochrome P450), have different genetic organization, and are subject to different regulatory mechanisms, which are poorly known. Because of their long-term survival capacity, broad catabolic abilities, and effective contact mechanisms with hydrocarbon molecules, alkanotrophic Rhodococcus strains have biotechnology applications and potential in bioremediation and biotransformation reactions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Aerobic cometabolism of 1,1,2,2-tetrachloroethane by Rhodococcus aetherivorans TPA grown on propane: kinetic study and bioreactor configuration analysis
No full textBACKGROUND
1,1,2,2-tetrachloroethane (TeCA) has been generally considered as non-biodegradable under aerobic conditions, while its complete biodegradation was reported with microbial consortia growing anaerobically. This study describes TeCA aerobic co-metabolic degradation by the propanotroph Rhodococcus aetherivorans strain TPA isolated from a TeCA-degrading consortium.
RESULTS
R. aetherivorans TPA was able to grow on aliphatic hydrocarbons from propane to pentane and on gaseous n-alkane metabolic intermediates. The Michaelis–Menten model allowed a satisfactory fit of the TPA propane utilization rates under resting cell conditions, while the TeCA degradation rates were successfully interpolated with Andrew's inhibition model. A significant propane–TeCA mutual inhibition was observed, although the results did not allow distinguishing between competitive and non-competitive inhibition. Among different bioreactor options for the on-site bioremediation of TeCA-contaminated groundwater, a single suspended-cell continuous stirred-tank reactor (CSTR) appeared to be the optimal one.
CONCLUSIONS
This study provides for the first time the kinetic and microbiological characterization of a bacterial strain capable of degrading TeCA under aerobic conditions
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Cometabolic treatment of chlorinated solvents: influence of operational conditions on the adaptation of indigenous biomasses
No full textThe effect of several operational conditions on the adaptation of indigenous biomasses was investigated in a microcosms study of chloroform (CF) cometabolic degradation with butane. The objective was to minimize the duration of the adaptation phase and the amount of growth substrate to provide in field applications. The adaptation to butane and CF was monitored at 5 concentrations of butane (1.50, 1.00, 0.50, 0.25 and 0.10 mg/L), at 3 concentrations of CF (1, 5 and 10 mg/L), at 4 temporal sequences of exposition to butane (continuous, 5 h/d, 7 h/d, 24 h every other day) and at 3 temperatures (15, 25 and 30°C). The results indicate that the most favorable condition for the adaptation of indigenous biomasses consists in the continuous exposition to a very low concentration of growth substrate (0.1 mg/L). In all the tests the degradation of CF started within 48 days. The microbiological characterization of the consortia indicated that the prolonged degradation of CF led to the selection of 3 specific butane-utilizing strains
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