Papers by Keyword: Acidithiobacillus ferrivorans

Abstract: The identification of genes involved in cold adaptations of psychrotolerant bacteria Acidithiobacillus ferrivorans is important for biomining processes that take place at low temperatures like Andean mining installations in Peru. We have performed relative quantification RT-qPCR on candidate genes to have a role in adaptations at low temperature (5°C). The candidate genes analyzed were six: Two trehalose synthesis pathway genes, trehalose synthase (treS) and malto-oligosiltrehalose trehalohydrolase (treZ) showing no overexpression at 5°C. Two diguanylate cyclases genes related to exopolymer synthesis and biofilm formation (designated as dgc-I and dgc-II in this paper) were overexpressed at 21°C. The rusA and rusB genes involved in iron oxidation showed no significant change for rusA and no expression for rusB gene in any of both conditions. Genes rpoC, gyrB and alaS were validated as reference genes. These results show congruency with trancriptomics studies about gene expression of A. ferrivorans. Furthermore, the trehalose synthesis genes show no overexpression at low temperatures suggesting that other cold adaptation mechanisms are involved.

Abstract: The draft genome of newly isolated Acidithiobacillus ferrivorans ZB-1 and DX-1 were deciphered to obtain a comprehensive insight into the genetic information and to discover the cellular mechanisms during its high activity in low temperature environment. Genome analysis speculated that Acidithiobacillus ferrivorans ZB-1 and DX-1 could fix carbon dioxide through the Calvin cycle and other central carbon metabolism potentially, and may be able to absorb and utilize nitrate or nitrite in the environment. The related cryophylactic genes (CspD, CspE, Fad and FabG) and gene clusters in fatty acid synthesis were discovered and suggested to play a crucial role in cold resistance.

Abstract: Acidophilic iron-oxidizing microorganisms are important in both environmental and biotechnological applications. These microorganisms are known to accelerate the dissolution of sulfur minerals such as pyrite (FeS₂), leading to the acid mine drainage generation , a serious pollution problem, that makes these microorganisms essential to the commercial processing of minerals and sulfur. In order to answer this question, diversity of native acidophilic bacteria isolated from acid mine drainage of Peru was evaluated. The samples were collected from Yanacocha mining (3000 m.a.s.l.) located in the North of Cajamarca region, Yanamina mining (4440 m.a.s.l.) located in the middle of Huancavelica region; finally, SPCC mining (2000 m.a.s.l.) located in the South of Moquegua region. We isolated 11 strains from which three were identified as Acidithiobacillus ferrooxidans, two as At. ferrivorans, two as At. ferridurans, three as Leptospirillum ferrooxidans and one as Acidiphilium sp. by comparative sequencing of PCR-amplified 16S rRNA genes. Phylogenetic analysis of the 16S rRNA genes revealed that some of the strains isolated are closely related to other already known, but there are some with similarities lower than < 95 percent. Our results provide the first study on the diversity of iron-oxidizing bacteria isolated from acid mine drainage of Peru.

Abstract: Four well-differentiated clusters have been identified among iron-oxidizing acidithiobacilli. One monophyletic group clusters with At. ferrooxidans^T and another with strains of At. ferrivorans. While At. ferrooxidans and At. ferrivorans share many physiological traits, they differ in some phenotypic characteristics such as motility, pH and temperature minima, and also in terms of genes involved in ferrous iron oxidation. The genome of a strain (CF27) of At. ferrivorans, which is characterized by its marked propensity to form macroscopic growths and biofilms, was sequenced at Genoscope (Evry, France). Comparative genomic studies were carried with all related Acidithiobacillus strains that have been sequenced to date, in order to identify genetic determinants responsible for physiological traits relating to the oxidation of iron and sulfur, and also to extracellular polymeric substances formation.

Abstract: It has long been recognized that isolates of iron- and sulfur-oxidizing acidophiles referred to as “Acidithiobacillus ferrooxidans” probably include more than one species, on the basis of differences in chromosomal GC contents and 16S rRNA gene sequences. Phylogenetic heterogeneity among these isolates was confirmed by phylogenetic analysis using the sequences of the 16S-23S intergenic spacers (ITS). Two main groups have been identified: the first includes the type strain of Acidithiobacillus ferrooxidans and a second comprises a cluster of newly isolated strains that have 98.5% 16S rRNA gene sequence identity with the type strain. Given that the new group of isolates have GC contents of 56 mol% as opposed to 58.8 mol% for At. ferrooxidansT, and that they share only 37% homologous DNA, these were given the new species name Acidithiobacillus ferrivorans. Further studies showed that, while strains of At. ferrivorans have many physiological traits in common with At. ferrooxidans, they also differ in some key characteristics. These include the ability to grow at temperatures as low as 4°C (as opposed to the lower limit of between 10 and 12°C for At. ferrooxidans) and the greater sensitivity of At. ferrivorans to low pH (minimum of 1.9 for growth as opposed to 1.3 for At. ferrooxidansT). Important genotypic differences include the fact that all strains of At. ferrivorans do not contain the archetypal rusticyanin gene (rusA), rather most contain a rusA homologue (rusB). Furthermore, the high potential iron-sulfur protein-encoding gene of all At. ferrivorans strains analyzed is more similar to the iro than to the hip gene characterized in At. ferrooxidansT. These results suggest that the iron oxidation pathways are different in At. ferrivorans and At. ferrooxidans.