Acidithiobacillus acidisediminis sp. nov., an acidophilic sulphur-oxidizing chemolithotroph isolated from acid mine drainage sediment.

Strain S30A2T, isolated from the acid mine drainage sediment of Mengzi Copper Mine, Yunnan, is proposed to represent a novel species of the sulphur-oxidizing genus Acidithiobacillus. Cells were Gram-stain-negative, non-endospore forming, highly motile with one or two monopolar flagella and rod-shaped. The strain was mesophilic, growing at 30-50 °C (optimum, 38 °C), acidophilic, growing at pH 2.0-4.5 (optimum, pH 2.5), and tolerant of 0-4 % (w/v; 684 mol l-1) NaCl. The 16S rRNA gene-based sequence analysis showed that strain S30A2T belongs to the genus Acidithiobacillus and shows the largest similarity of 96.6 % to the type strain Acidithiobacillus caldus KUT. The genomic DNA G+C content of strain S30A2T was 59.25 mol%. The average nucleotide identity ANIb and ANIm values between strain S30A2T and A. caldus KUT were 70.95 and 89.78 %, respectively and the digital DNA-DNA hybridization value was 24.9 %. Strain S30A2T was strictly aerobic and could utilize elementary sulphur and tetrathionate to support chemolithotrophic growth. The major cellular fatty acid of S30A2T was C19 : 1ω7c. The respiratory quinones were ubiquinone-8 and ubiquinone-7. Based upon its phylogenetic, genetic, phenotypic, physiologic and chemotaxonomic characteristics, strain S30A2T is considered to represent a novel species of the genus Acidithiobacillus, for which the name Acidithiobacillus acidisediminis sp. nov. is proposed. The type strain is S30A2T (=CGMCC 1.17059T=KCTC 72580T).

Acidithiobacillus sulfuriphilus sp. nov.: an extremely acidophilic sulfur-oxidizing chemolithotroph isolated from a neutral pH environment.

The genus Acidithiobacillus currently includes seven species with validly published names, which fall into two major groups, those that can oxidize ferrous iron and those that do not. All seven species can use zero-valent sulfur and reduced sulfur oxy-anions as electron donors, are obligately chemolithotrophic and acidophilic bacteria with pH growth optima below 3.0. The 16S rRNA gene of a novel strain (CJ-2T) isolated from circum-neutral pH mine drainage showed 95-97 % relatedness to members of the genus Acidithiobacillus. Digital DNA-DNA hybridization (dDDH) values between strains and whole-genome pairwise comparisons between the CJ-2T strain and the reference genomes available for members of the genus Acidithiobacillus confirmed that CJ-2Trepresents a novel species of this genus. CJ-2T is a strict aerobe, oxidizes zero-valent sulfur and reduced inorganic sulfur compounds but does not use ferrous iron or hydrogen as electron donors. The isolate is mesophilic (optimum growth temperature 25-28 °C) and extremely acidophilic (optimum growth pH 3.0), though its pH optimum and maximum were significantly higher than those of non-iron-oxidising acidithiobacilli with validly published names. The major fatty acids of CJ-2T were C18 : 1ω7c, C:16 : 1ω7c/iso-C15 : 0 2-OH, C16 : 0 and C19 : 0 cyclo ω8c and the major respiratory quinone present was Q8. The name Acidithiobacillussulfuriphilus sp. nov. is proposed, the type strain is CJ-2T (=DSM 105150T=KCTC 4683T).

Phylogeny, Divergent Evolution, and Speciation of Sulfur-Oxidizing Acidithiobacillus Populations.

BACKGROUND: Habitats colonized by acidophiles as an ideal physical barrier may induce genetic exchange of microbial members within the common communities, but little is known about how species in extremely acidic environments diverge and evolve. RESULTS: Using the acidophilic sulfur-oxidizer Acidithiobacillus as a case study, taxonomic reclassifications of many isolates provides novel insights into their phylogenetic lineage. Whole-genome-based comparisons were attempted to investigate the intra- and inter-species divergence. Recent studies clarified that functional and structural specificities of bacterial strains might provide opportunities for adaptive evolution responding to local environmental conditions. Acidophilic microorganisms play a key role in the acidification of natural waters and thus the formation of extremely acidic environments, and the feedbacks of the latter might confer the distinct evolutionary patterns of Acidithiobacillus spp. Varied horizontal gene transfer events occurred in different bacterial strains, probably resulting in the expansion of Acidithiobacillus genomes. Gene loss as another evolutionary force might cause the adaptive phenotypic diversity. A conceptual model for potential community-dependent evolutionary adaptation was thus proposed to illustrate the observed genome differentiation. CONCLUSIONS: Collectively, the findings shed light on the phylogeny and divergent evolution of Acidithiobacillus strains, and provided a useful reference for evolutionary studies of other extremophiles.

Acidithiobacillus ferrooxidans.

Acidithiobacillus ferrooxidans is by far the most widely studied of all extremely acidophilic prokaryotes. While it is found in many types of natural low-pH environments in a variety of geoclimatic contexts, it has been more widely cited in anthropogenic (mostly mine-impacted) environments. It is responsible for accelerating the oxidative dissolution of sulfide minerals, causing the generation of polluting acidic metal-rich drainage waters but also facilitating the recovery of base and precious metals from mineral leachates. It can colonize barren mineral landscapes, is a driver of ecological successions in acidic biotopes, and is an important model organism in astrobiology. It catalyses the dissimilatory oxidation of iron, sulfur, and hydrogen, and the reduction of iron and sulfur, and has a major impact in the geochemical cycling of these elements in low-pH environments. This infographic summarizes the fundamental phylogeny, physiology and genomic features of this extremophile.

The microbial community in a moving bed biotrickling filter operated to remove hydrogen sulfide from gas streams.

The information available on the microbial communities responsible for pollutant degradation is increasingly accessible. Its use to optimize process design and operation is an important challenge in the field of effluent treatment research. Therefore, a prototype of a moving bed biotrickling filter (MBBTF) reactor was designed and, for the first time, operated at full-scale for the removal of sulfides desorbing from tannery industrial wastewater. The bacterial community operating in this innovative reactor was studied, and its composition and response to different operating conditions were characterized. A stable biomass, dominated by sulfur-oxidizing bacteria of the genus Acidithiobacillus was selected from inside the MBBTF reactor, and temperature, pH and bed rotation were shown to be the main factors driving the community structure. Moreover, data from different approaches indicated an uneven spatial distribution of biofilm inside the studied reactor, due to the combined effect of fluid dynamics and substrate gradients within the bed volume. Despite the high removal efficiency achieved by this innovative prototype (80% on average), the data suggested that the result could be improved by adopting solutions for a more stable and even biofilm distribution. It was shown that short frequent bed rotations, rather than long scattered rotations, ensured biomass stability. Furthermore, diversifying biofilm support media as a function of expected local pollutant concentrations should be considered. Data obtained from the bacterial community can therefore provide indications for possible further improvement of MBBTF reactor design and performance.

Functionality of tRNAs encoded in a mobile genetic element from an acidophilic bacterium.

The genome of the acidophilic, bioleaching bacterium Acidithiobacillus ferrooxidans, strain ATCC 23270, contains 95 predicted tRNA genes. Thirty-six of these genes (all 20 species) are clustered within an actively excising integrative-conjugative element (ICEAfe1). We speculated that these tRNA genes might have a role in adapting the bacterial tRNA pool to the codon usage of ICEAfe1 genes. To answer this question, we performed theoretical calculations of the global tRNA adaptation index to the entire A. ferrooxidans genome with and without the ICEAfe1 encoded tRNA genes. Based on these calculations, we observed that tRNAs encoded in ICEAfe1 negatively contribute to adapt the tRNA pool to the codon use in A. ferrooxidans. Although some of the tRNAs encoded in ICEAfe1 are functional in aminoacylation or protein synthesis, we found that they are expressed at low levels. These findings, along with the identification of a tRNA-like RNA encoded in the same cluster, led us to speculate that tRNA genes encoded in the mobile genetic element ICEAfe1 might have acquired mutations that would result in either inactivation or the acquisition of new functions.

Effects of pyrite and sphalerite on population compositions, dynamics and copper extraction efficiency in chalcopyrite bioleaching process.

This study used an artificial microbial community with four known moderately thermophilic acidophiles (three bacteria including Acidithiobacillus caldus S1, Sulfobacillus thermosulfidooxidans ST and Leptospirillum ferriphilum YSK, and one archaea, Ferroplasma thermophilum L1) to explore the variation of microbial community structure, composition, dynamics and function (e.g., copper extraction efficiency) in chalcopyrite bioleaching (C) systems with additions of pyrite (CP) or sphalerite (CS). The community compositions and dynamics in the solution and on the ore surface were investigated by real-time quantitative PCR (qPCR). The results showed that the addition of pyrite or sphalerite changed the microbial community composition and dynamics dramatically during the chalcopyrite bioleaching process. For example, A. caldus (above 60%) was the dominant species at the initial stage in three groups, and at the middle stage, still dominated C group (above 70%), but it was replaced by L. ferriphilum (above 60%) in CP and CS groups; at the final stage, L. ferriphilum dominated C group, while F. thermophilum dominated CP group on the ore surface. Furthermore, the additions of pyrite or sphalerite both made the increase of redox potential (ORP) and the concentrations of Fe3+ and H+, which would affect the microbial community compositions and copper extraction efficiency. Additionally, pyrite could enhance copper extraction efficiency (e.g., improving around 13.2% on day 6) during chalcopyrite bioleaching; on the contrary, sphalerite restrained it.

[Phylogenetic and genetic heterogeneity of 23 Acidithiobacillus strains isolated from different geographical locations].

Objective: To study the phylogenetic and genetic heterogeneity of 23 Acidithiobacillus strains from various geographical locations, as well as the relationship between the DNA fingerprinting classification and geographical origin of Acidithiobacillus. Methods: Partial 16S-23S rRNA gene intergenic spacer (ITS) was used to construct corresponding phylogenetic trees based on the sequence homology. rus gene amplification and rep-PCR assay with two different primers (BOXAIR and ERIC) were performed to analyze genetic heterogeneity of Acidithiobacillus strains from diverse environment. Results: Acidithiobacillus revealed a great genetic heterogeneity. The whole isolates were classified into five groups by ITS sequence analysis. This result was similar with that obtained by rep-PCR. Acidithiobacillus ferrooxidans strains were always divided into two groups of phylogenetic and BOXAIR fingerprinting cluster analysis. However, these were clustered one group in the ERIC dendrogram. Genotypic analysis of the rus gene suggested that different iron oxidation pathways have been evolved in these closely related bacteria. Taken together, the iron oxidation pathway of Acidithiobacillus and phylogenetic groups have no obvious correlation. ITS gene has been proven very useful in distinguishing closely related species or subspecies of Acidithiobacillus, to BOXAIR-PCR, which has been recommended as reliable tool for genetic heterogeneity analysis of Acidithiobacillus.

Comparative genomics unravels metabolic differences at the species and/or strain level and extremely acidic environmental adaptation of ten bacteria belonging to the genus Acidithiobacillus.

Members of the Acidithiobacillus genus are widely found in extreme environments characterized by low pH and high concentrations of toxic substances, thus it is necessary to identify the cellular mechanisms needed to cope with these harsh conditions. Pan-genome analysis of ten bacteria belonging to the genus Acidithiobacillus suggested the existence of core genome, most of which were assigned to the metabolism-associated genes. Additionally, the unique genes of Acidithiobacillus ferrooxidans were much less than those of other species. A large proportion of Acidithiobacillus ferrivorans-specific genes were mapped especially to metabolism-related genes, indicating that diverse metabolic pathways might confer an advantage for adaptation to local environmental conditions. Analyses of functional metabolisms revealed the differences of carbon metabolism, nitrogen metabolism, and sulfur metabolism at the species and/or strain level. The findings also showed that Acidithiobacillus spp. harbored specific adaptive mechanisms for thriving under extreme environments. The genus Acidithiobacillus had the genetic potential to resist and metabolize toxic substances such as heavy metals and organic solvents. Comparison across species and/or strains of Acidithiobacillus populations provided a deeper appreciation of metabolic differences and environmental adaptation, as well as highlighting the importance of cellular mechanisms that maintain the basal physiological functions under complex acidic environmental conditions.

Detection, identification and typing of Acidithiobacillus species and strains: a review.

The genus Acidithiobacillus comprises several species of Gram-negative acidophilic bacteria that thrive in natural and man-made low pH environments in a variety of geo-climatic contexts. Beyond their fundamental interest as model extreme acidophiles, these bacteria are involved in the processing of minerals and the desulfurization of coal and natural gas, and are also sources of environmental pollution due to their generation of acid mine drainage and corrosion of cement and concrete structures. Acidithiobacillus spp. are therefore considered a biotechnologically relevant group of bacteria, and their identification and screening in natural and industrial environments is of great concern. Several molecular typing methodologies have been instrumental in improving knowledge of the inherent diversity of acidithiobacilli by providing information on the genetic subtypes sampled in public and private culture collections; more recently, they have provided specific insight into the diversity of acidithiobacilli present in industrial and natural environments. The aim of this review is to provide an overview of techniques used in molecular detection, identification and typing of Acidithiobacillus spp. These methods will be discussed in the context of their contribution to the general and specific understanding of the role of the acidithiobacilli in microbial ecology and industrial biotechnology. Emerging opportunities for industrial and environmental surveillance of acidithiobacilli using next-generation molecular typing methodologies are also reviewed.

Generation of acid mine drainage around the Karaerik copper mine (Espiye, Giresun, NE Turkey): implications from the bacterial population in the Acisu effluent.

The Karaerik Cu mine is a worked-out deposit with large volumes of tailings and slags which were left around the mine site without any protection. Natural feeding of these material and run-off water from the mineralised zones into the Acisu effluent causes a serious environmental degradation and creation of acid mine drainage (AMD) along its entire length. This research aims at modelling the formation of AMD with a specific attempt on the characterisation of the bacterial population in association with AMD and their role on its occurrence. Based on 16SrRNA analyses of the clones obtained from a composite water sample, the bacterial community was determined to consist of Acidithiobacillus ferrivorans, Ferrovum myxofaciens, Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans as iron-oxidising bacteria, Acidocella facilis, Acidocella aluminiidurans, Acidiphilium cryptum and Acidiphilium multivorum as iron-reducing bacteria, and Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidiphilium cryptum as sulphur-oxidising bacteria. This association of bacteria with varying roles was interpreted as evidence of a concomitant occurrence of sulphur and iron cycles during the generation of AMD along the Acisu effluent draining the Karaerik mine.

Biogeography of sulfur-oxidizing Acidithiobacillus populations in extremely acidic cave biofilms.

Extremely acidic (pH 0-1.5) Acidithiobacillus-dominated biofilms known as snottites are found in sulfide-rich caves around the world. Given the extreme geochemistry and subsurface location of the biofilms, we hypothesized that snottite Acidithiobacillus populations would be genetically isolated. We therefore investigated biogeographic relationships among snottite Acidithiobacillus spp. separated by geographic distances ranging from meters to 1000s of kilometers. We determined genetic relationships among the populations using techniques with three levels of resolution: (i) 16S rRNA gene sequencing, (ii) 16S-23S intergenic transcribed spacer (ITS) region sequencing and (iii) multi-locus sequencing typing (MLST). We also used metagenomics to compare functional gene characteristics of select populations. Based on 16S rRNA genes, snottites in Italy and Mexico are dominated by different sulfur-oxidizing Acidithiobacillus spp. Based on ITS sequences, Acidithiobacillus thiooxidans strains from different cave systems in Italy are genetically distinct. Based on MLST of isolates from Italy, genetic distance is positively correlated with geographic distance both among and within caves. However, metagenomics revealed that At. thiooxidans populations from different cave systems in Italy have different sulfur oxidation pathways and potentially other significant differences in metabolic capabilities. In light of those genomic differences, we argue that the observed correlation between genetic and geographic distance among snottite Acidithiobacillus populations is partially explained by an evolutionary model in which separate cave systems were stochastically colonized by different ancestral surface populations, which then continued to diverge and adapt in situ.

Investigation of Acidithiobacillus ferrooxidans in pure and mixed-species culture for bioleaching of Theisen sludge from former copper smelting.

AIMS: The aim of this study was to investigate the potential of bioleaching for the treatment of an environmentally hazardous waste, a blast-furnace flue dust designated Theisen sludge. METHODS AND RESULTS: Bioleaching of Theisen sludge was investigated at acidic conditions with Acidithiobacillus ferrooxidans in pure and mixed-species culture with Acidiphilium. In shaking-flask experiments, bioleaching parameters (pH, redox potential, zinc extraction from ZnS, ferrous- and ferric-iron concentration) were controlled regularly. The analysis of the dissolved metals showed that 70% zinc and 45% copper were extracted. Investigations regarding the arsenic and antimony species were performed. When iron ions were lacking, animonate (Sb(V)) and total arsenic concentration were highest in solution. The bioleaching approach was scaled up in stirred-tank bioreactors resulting in higher leaching efficiency of valuable trace elements. Concentrations of dissolved antimony were approx. 23 times, and of cobalt, germanium, and rhenium three times higher in comparison to shaking-flask experiments, when considering the difference in solid load of Theisen sludge. CONCLUSIONS: The extraction of base and trace metals from Theisen sludge, despite of its high content of heavy metals and organic compounds, was feasible with iron-oxidizing acidophilic bacteria. In stirred-tank bioreactors, the mixed-species culture performed better. SIGNIFICANCE AND IMPACT OF THE STUDY: To the best of our knowledge, this study is the first providing an appropriate biological technology for the treatment of Theisen sludge to win valuable elements.

[Phylogenetic and diversity analysis of Acidithiobacillus spp. based on 16S rRNA and RubisCO genes homologues].

Objective: The purpose of the study was to reveal geographic region-related Acidithiobacillus spp. distribution and allopatric speciation. Phylogenetic and diversity analysis was done to expand our knowledge on microbial phylogeography, diversity-maintaining mechanisms and molecular biogeography. Methods: We amplified 16S rRNA gene and RubisCO genes to construct corresponding phylogenetic trees based on the sequence homology and analyzed genetic diversity of Acidithiobacillus spp.. Results: Thirty-five strains were isolated from three different regions in China (Yunnan, Hubei, Xinjiang). The whole isolates were classified into five groups. Four strains were identified as A. ferrivorans, six as A. ferridurans, YNTR4-15 Leptspirillum ferrooxidans and HBDY3-31 as Leptospirillum ferrodiazotrophum. The remaining strains were identified as A. ferrooxidans. Analysis of cbbL and cbbM genes sequences of representative 26 strains indicated that cbbL gene of 19 were two copies (cbbL1 and cbbL2) and 7 possessed only cbbL1. cbbM gene was single copy. In nucleotide-based trees, cbbL1 gene sequences of strains were separated into three sequence types, and the cbbL2 was similar to cbbL1 with three types. Codon bias of RubisCO genes was not obvious in Acidithiobacillus spp.. Conclusion: Strains isolated from three different regions in China indicated a great genetic diversity in Acidithiobacillus spp. and their 16S rRNA/RubisCO genes sequence was of significant difference. Phylogenetic tree based on 16S rRNA genes and RubisCO genes was different in Acidithiobacillus spp..

Acidithiobacillus ferriphilus sp. nov., a facultatively anaerobic iron- and sulfur-metabolizing extreme acidophile.

The genus Acidithiobacillus includes three species that conserve energy from the oxidation of ferrous iron, as well as reduced sulfur, to support their growth. Previous work, based on multi-locus sequence analysis, identified a fourth group of iron- and sulfur-oxidizing acidithiobacilli as a potential distinct species. Eleven strains of 'Group IV' acidithiobacilli, isolated from different global locations, have been studied. These were all shown to be obligate chemolithotrophs, growing aerobically by coupling the oxidation of ferrous iron or reduced sulfur (but not hydrogen) to molecular oxygen, or anaerobically by the oxidation of reduced sulfur coupled to ferric iron reduction. All strains were mesophilic, although some were also psychrotolerant. Strain variation was also noted in terms of tolerance to extremely low pH and to elevated concentrations of transition metals. One strain was noted to display far greater tolerance to chloride than reported for other iron-oxidizing acidithiobacilli. All of the strains were able to catalyse the oxidative dissolution of pyrite and, on the basis of some of the combined traits of some of the strains examined, it is proposed that these may have niche roles in commercial mineral bioprocessing operations, such as for low temperature bioleaching of polysulfide ores in brackish waters. The name Acidithiobacillus ferriphilus sp. nov. is proposed to accommodate the strains described, with the type strain being M20T ( = DSM 100412T = JCM 30830T).

A Novel Uncultured Bacterium of the Family Gallionellaceae: Description and Genome Reconstruction Based on the Metagenomic Analysis of Microbial Community in Acid Mine Drainage.

Drainage waters at the metal mining areas often have low pH and high content of dissolved metals due to oxidation of sulfide minerals. Extreme conditions limit microbial diversity in- such ecosystems. A drainage water microbial community (6.5'C, pH 2.65) in an open pit at the Sherlovaya Gora polymetallic open-cast mine (Transbaikal region, Eastern Siberia, Russia) was studied using metagenomic techniques. Metagenome sequencing provided information for taxonomic and functional characterization of the micro- bial community. The majority of microorganisms belonged to a single uncultured lineage representing a new Betaproteobacteria species of the genus Gallionella. While no.acidophiles are known among the cultured members of the family Gallionellaceae, similar 16S rRNA gene sequences were detected in acid mine drain- ages. Bacteria ofthe genera Thiobacillus, Acidobacterium, Acidisphaera, and Acidithiobacillus,-which are com- mon in acid mine drainage environments, were the minor components of the community. Metagenomic data were -used to determine the almost complete (-3.4 Mb) composite genome of the new bacterial. lineage desig- nated Candidatus Gallionella acididurans ShG14-8. Genome analysis revealed that Fe(II) oxidation probably involved the cytochromes localized on the outer membrane of the cell. The electron transport chain included NADH dehydrogenase, a cytochrome bc1 complex, an alternative complex III, and cytochrome oxidases of the bd, cbb3, and bo3 types. Oxidation of reduced sulfur compounds probably involved the Sox system, sul- fide-quinone oxidoreductase, adenyl sulfate reductase, and sulfate adenyltransferase. The genes required for autotrophic carbon assimilation via the Calvin cycle were present, while no pathway for nitrogen fixation was revealed. High numbers of RND metal transporters and P type ATPases were probably responsible for resis- tance to heavy metals. The new microorganism was an aerobic chemolithoautotroph of the group of psychrotolerant iron- and sulfur-oxidizing acidophiles of the family Gallionellaceae, which are common in acid mine drainages.

Microbial malaise: how can we classify the microbiome?

The names and lineages of microorganisms are critical to our understanding of the microbiome. However, microbial taxonomy and phylogeny are in perpetual flux, with emerging criteria being used to rename and reshape our views of the microbial world. Different candidate molecular and nonmolecular criteria are often broadly consistent with one another, which underpins the pluralistic approach to taxonomy. However, the taxonomic picture is clouded when underlying criteria are not in agreement, or when reference datasets contain erroneously named organisms. How does the shifting taxonomic landscape impact our interpretation of microbial communities, especially in the face of inconsistencies and errors? How can taxonomy be applied in a consistent way when different users have different requirements of the classifications that emerge? The key path forward involves finding ways to integrate conflicting taxonomic criteria, choosing the right units of analysis for microbiomic studies, and making molecular taxonomy transparent and accessible in a way that complements current genomic resources.

[Physiological Properties of Acidithiobacillus ferrooxidans Strains Isolated from Sulfide Ore Deposits in Kazakhstan].

Acidithiobacillus ferroxidans strains were isolated from acidophilic microbial communities of Kazakhstan sulfide ore deposits. Their biotechnologically important properties (optimal and maximal growth temperatures and resistance to NaCl) were determined. While temperature optima of the strains were the same (30-32 degrees C), temperature ranges were different. Thus, strain TFBK oxidized iron very poorly at 37 degrees C, while for strain TFV, the iron oxidation rate at this temperature was insignificantly lower than at lesser temperatures. NaCl inhibited the oxidative activity of both strains. Iron oxidation by strain TFV was inhibited at 5 g/L NaCl and was suppressed almost completely at 20 g/L. Iron oxidation by strain TFBK was inhibited by NaCl to a lesser degree, so that iron oxidation rate was relatively high at 10 g/L, while at 20 g/L NaCl the process was not suppressed completely, although the oxidation rate was low. Sulfur oxidation by these strains was less affected by NaCl than oxidation of ferrous iron. Sulfur oxidation by strain TFV was considerably inhibited only at 20 g/L NaCl, but was not suppressed completely. Sulfur oxidation by strain TFBK was more affected by NaCl. At 10 g/L NaCl the oxidation rate was much lower than at lower NaCl concentrations (sulfate concentrations after 6 days of oxidation at 5 and 10 g/L NaCl were -130 and -100 mM, respectively). While sulfur oxidation by strain TFBK was considerably inhibited at 10 and 20 g/L NaCl, similar to strain TFV it was not suppressed completely. Our results indicate the adaptation of the species A. ferrooxidans to a broad range of growth conditions.

Metagenomic analysis reveals adaptations to a cold-adapted lifestyle in a low-temperature acid mine drainage stream.

An acid mine drainage (pH 2.5-2.7) stream biofilm situated 250 m below ground in the low-temperature (6-10°C) Kristineberg mine, northern Sweden, contained a microbial community equipped for growth at low temperature and acidic pH. Metagenomic sequencing of the biofilm and planktonic fractions identified the most abundant microorganism to be similar to the psychrotolerant acidophile, Acidithiobacillus ferrivorans. In addition, metagenome contigs were most similar to other Acidithiobacillus species, an Acidobacteria-like species, and a Gallionellaceae-like species. Analyses of the metagenomes indicated functional characteristics previously characterized as related to growth at low temperature including cold-shock proteins, several pathways for the production of compatible solutes and an anti-freeze protein. In addition, genes were predicted to encode functions related to pH homeostasis and metal resistance related to growth in the acidic metal-containing mine water. Metagenome analyses identified microorganisms capable of nitrogen fixation and exhibiting a primarily autotrophic lifestyle driven by the oxidation of the ferrous iron and inorganic sulfur compounds contained in the sulfidic mine waters. The study identified a low diversity of abundant microorganisms adapted to a low-temperature acidic environment as well as identifying some of the strategies the microorganisms employ to grow in this extreme environment.

Identification and characterization of Acidithiobacillus ferrooxidans YY2 and its application in the biodesulfurization of coal.

The acidophilic Fe-oxidizing and S-oxidizing bacterium YY2 was isolated from the acid drainage of a coalmine. Based on morphological and physiological characteristics and phylogenetic analysis, it was identified as Acidithiobacillus ferrooxidans. Significant differences were observed in the oxidation efficiency and cell morphology when YY2 was cultured in 9K medium with ferrous ion (Fe(2+)), elemental sulfur (S(0)), and pyrite as the sole energy source. YY2 exhibited marked Fe(2+) oxidation activity; 44.2 g · L(-1) FeSO4 · 7H2O was completely oxidized in 30 h, but the rates of S(0) and pyrite oxidization were slower. After 20 days, the efficiencies of oxidizing 10 g · L(-1) S(0) and 10 g · L(-1) pyrite were approximately 9.6% and 20%, respectively. Cells cultured in pyrite as substrate secreted more extracellular polymeric substances than they did when cultured in Fe(2+) or S(0). Additionally, 75% total sulfur removal and 86% pyritic sulfur removal was achieved in a sequencing batch reactor of biodesulfurization of coal.