Acidithiobacillus thiooxidans is an acidophilic chemolithoautotrophic bacterium widely used in the mining industry due to its metabolic sulfur-oxidizing capability. The biooxidation of sulfide minerals is enhanced through the attachment of At. thiooxidans cells to the mineral surface. The Type IV pili (TfP) of At. thiooxidans may play an important role in the bacteria attachment since TfP play a key adhesive role in the attachment and colonization of different surfaces. In this work, we report for the first time the mRNA sequence of three TfP proteins from At. thiooxidans, the adhesin protein PilY1 and the TfP pilins PilW and PilV. The nucleotide sequences of these TfP proteins show changes in some nucleotide positions with respect to the corresponding annotated sequences. The bioinformatic analyses and 3D-modeling of protein structures sustain their classification as TfP proteins, as structural homologs of the corresponding proteins of Ps. aeruginosa, results that sustain the role of PilY1, PilW and PilV in pili assembly. Also, that PilY1 comprises the conserved Neisseria-PilC (superfamily) domain of the tip-associated adhesin, while PilW of the superfamily of putative TfP assembly proteins and PilV belongs to the superfamily of TfP assembly protein. In addition, the analyses suggested the presence of specific functional domains involved in adhesion, energy transduction and signaling functions. The phylogenetic analysis indicated that the PilY1 of Acidithiobacillus genus forms a cohesive group linked with iron- and/or sulfur-oxidizing microorganisms from acid mine drainage or mine tailings.
Pyrite bio-oxidation by chemolithotrophic acidophile bacteria has been applied in the mining industry to bioleach metals or to remove pyritic sulfur from coal. In this process, it is desirable to use autochthonous and already adapted bacteria isolated directly from the mining sites where biomining will be applied. Bacteria present in the remnant solution from a mining company were identified through cloning techniques. For that purpose, we extracted total RNA and performed reverse transcription using a novel pair of primers designed from a small region of the 16S gene (V1–V3) that contains the greatest intraspecies diversity. After cloning, a high proportion of individuals of the strains ATCC-23270 (NR_074193.1 and NR_041888.1) and DQ321746.1 of the well-known species Acidithiobacillus ferrooxidans were found, as well as two new wild strains of A. ferrooxidans. This result showed that the acidic remnant solution comprises a metapopulation. We assayed these strains to produce bioferric flocculant to enhance the subsequent pyrite bio-oxidation, applying two-stage chemical–bacterial oxidation. It was shown that the strains were already adapted to a high concentration of endogenous Fe2+ (up to 20 g·L−1), increasing the volumetric productivity of the bioferric flocculant. Thus, no preadaptation of the community was required. We detected Au and Ag particles originally occluded in the old pyritic flotation tailings assayed, but the extraction of Au and Ag by cyanidation resulted in ca. 30.5% Au and 57.9% Ag.
Although the expression of several connexins has been reported in the central nervous system, only Cx36 and Cx45 have been undoubtedly demonstrated as part of electrical synapses. Dopamine neurons of the substantia nigra pars compacta (SNc), whose electrical activity is important for goal directed behavior, learning, working memory, reward and modulation of motor activity, communicate with other Dopamine neurons through electrical synapses. However, the expression profile of connexins in the SNc has only been determined in the rat. Considering that electrical synchronization of Dopamine neurons could have important roles in the modulation of levels of Dopamine released both locally and in the areas of innervation, and therefore in the functioning of Dopamine circuits, we decided to determine the expression profile of connexins in freshly isolated cells from SNc of adult mice. Using single cell RT-PCR, we show that a subset of DA neurons, and neurons of glutamate and GABA phenotypes, express Cx45 as well Cx26, Cx30, Cx31.1, Cx32 and Cx43, but not Cx36. Thus our results suggest that in adult mice, Cx45 is the connexin used by some of DA neurons of the SNc to be electrically coupled. Our results also suggest that glutamate and GABA neurons of the SNc, could also be electrically coupled with DA neurons. Despite the inability of the other connexins to form functional gap junctions in neurons, the expression of Cx26, Cx30, Cx32 and Cx43 may be the reflect of the ability of the neurons of SNc to release neuromodulators through hemichannel activity.
24 Acidithiobacillus thiooxidans is an acidophilic chemolithoautotrophic bacterium 25 widely used in the mining industry due to its metabolic sulfur-oxidizing capability. The 26 biooxidation of sulfide minerals is enhanced through the attachment of A. thiooxidans 27 cells to the mineral surface. The Type IV pili (TfP) of At. thiooxidans may play an 28 important role in the bacteria attachment, since among other functions, TfP play a 29 key adhesive role in the attachment to and colonization of different surfaces. In this 30 work, we reported for the first time the confirmed mRNA sequences of three TfP 31 proteins from At. thiooxidans, the protein PilY1 and the TfP pilins PilW and PilV. The 32 nucleotide sequences of these TfP proteins show changes of some nucleotide 33 positions with respect to the corresponding annotated sequences. The bioinformatic 34 analyses and 3D-modeling of protein structures sustain their classification as TfP 35 proteins, as structural homologs of the corresponding proteins of P. aeruginosa, 36 results that sustain the role of PilY1, PilW and PilV in pili assembly. Also, that PilY1 37 comprises the conserved Neisseria-PilC (superfamily) domain of the tip-associated 38 adhesin, while PilW of the superfamily of putative TfP assembly proteins and PilV 39 belongs to the superfamily of TfP assembly protein. Also, the analyses suggested 40 the presence of specific functional domains involved in adhesion, energy 41 transduction and signaling functions. The phylogenetic analysis indicated that the 42 PilY1 of Acidithiobacillus genus forms a cohesive group linked with iron-and/or 43 sulfur-oxidizing microorganisms from acid mine drainage or mine tailings. This work 3 44 enriches knowledge regarding colonization, adhesion and biooxidation of inorganic 45 sulfurs by A. thiooxidans. 46 4 47 Introduction 48 Acidithiobacillus thiooxidans is an acidophilic chemolithoautotroph that uses reduced 49 sulfurs as a source of electrons and reducing power, including elemental sulfur (S 0 ), 50 polysulfides (S n 2-) and sulfide minerals, such as pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ) 51 or sphalerite (ZnS). 52 Bacterial attachment to mineral surfaces influences the rate of dissolution of the 53 mineral because of surficial phenomena: Mixed potential decreases, changes in 54 kinetics and mass-transport processes [1]. Accordingly, bacterial attachment is due 55 to self-organization by a bioelectrochemical evolution on the interface. Interfacial 56 studies on charge and mass transfer demonstrate that S 0 biooxidation by At. 57 thiooxidans begins in the early stages of interaction (1 to 24 h) when the biofilm is 58 not constituted, and it is primarily controlled by surficial characteristics that pivoted 59 the bacterial attachment to the hydrophobic S 0 ; such attachment is an energy-60 dependent process in which At. thiooxidans essentially activates or modifies the 61 reactive properties of S 0 [2, 3]. The hydrophobic character of the interface 62 "determines the free energy of the adhesion process" [4]. The Typ...
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