Permanent draft genome of Thiobacillus thioparus DSM 505T, an obligately chemolithoautotrophic member of the Betaproteobacteria

Thiobacillus sedimenti sp. nov., a chemolithoautotrophic sulphur-oxidizing bacterium isolated from freshwater sediment

A sulphur-oxidizing bacterium, designated strain SCUT-2T, was isolated from freshwater sediment collected from the Pearl River in Guangzhou, PR China. This strain was an obligate chemolithoautotroph, utilizing reduced sulphur compounds (elemental sulphur, thiosulphate, tetrathionate and sulphite) as the electron donor. Growth of strain SCUT-2T was observed at 20-40 ℃ (optimum at 30 °C), pH 5.0-9.0 (optimum at 6.0), and NaCl concentration range of 0-9 g L-1 (optimum at 1 g L-1). The major cellular fatty acids were C16:0 ω7c and cyclo-C17:0. The DNA G + C content of the complete genome sequence was 66.8 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain SCUT-2T formed a lineage within the genus Thiobacillus, showing gene sequence identity of 98.0% with its closest relative Thiobacillus thioparus THI 115. The genome of strain SCUT-2T contains multiple genes encoding sulphur-oxidizing enzymes that catalyse the oxidation of reduced sulphur compounds, partial genes that are necessary for denitrification, and the genes encoding cbb3-type cytochrome c oxidase, aa3-type cytochrome c oxidase and bd-type quinol oxidase. Facultative anaerobic growth occurs when using nitrate as the electron acceptor and thiosulphate as the electron donor. On the basis of phenotypic, chemotaxonomic, genotypic and phylogenetic analysis, strain SCUT-2T (= GDMCC 1.4108T = JCM 39443T) is deemed to represent a novel Thiobacillus species, for which we propose the name Thiobacillus sedimenti sp. nov.

pH and thiosulfate dependent microbial sulfur oxidation strategies across diverse environments

Sulfur oxidizing bacteria (SOB) play a key role in sulfur cycling in mine tailings impoundment (TI) waters, where sulfur concentrations are typically high. However, our understanding of SOB sulfur cycling via potential S oxidation pathways (sox, rdsr, and S4I) in these globally ubiquitous contexts, remains limited. Here, we identified TI water column SOB community composition, metagenomics derived metabolic repertoires, physicochemistry, and aqueous sulfur concentration and speciation in four Canadian base metal mine, circumneutral-alkaline TIs over four years (2016 - 2019). Identification and examination of genomes from nine SOB genera occurring in these TI waters revealed two pH partitioned, metabolically distinct groups, which differentially influenced acid generation and sulfur speciation. Complete sox (csox) dominant SOB (e.g., Halothiobacillus spp., Thiomonas spp.) drove acidity generation and S2O3 2- consumption via the csox pathway at lower pH (pH ~5 to ~6.5). At circumneutral pH conditions (pH ~6.5 to ~8.5), the presence of non-csox dominant SOB (hosting the incomplete sox, rdsr, and/or other S oxidation reactions; e.g. Thiobacillus spp., Sulfuriferula spp.) were associated with higher [S2O3 2-] and limited acidity generation. The S4I pathway part 1 (tsdA; S2O3 2- to S4O6 2-), was not constrained by pH, while S4I pathway part 2 (S4O6 2- disproportionation via tetH) was limited to Thiobacillus spp. and thus circumneutral pH values. Comparative analysis of low, natural (e.g., hydrothermal vents and sulfur hot springs) and high (e.g., Zn, Cu, Pb/Zn, and Ni tailings) sulfur systems literature data with these TI results, reveals a distinct TI SOB mining microbiome, characterized by elevated abundances of csox dominant SOB, likely sustained by continuous replenishment of sulfur species through tailings or mining impacted water additions. Our results indicate that under the primarily oxic conditions in these systems, S2O3 2- availability plays a key role in determining the dominant sulfur oxidation pathways and associated geochemical and physicochemical outcomes, highlighting the potential for biological management of mining impacted waters via pH and [S2O3 2-] manipulation.

Identification of sulfur-oxidizing bacteria from fishponds and their performance to remove hydrogen sulfide under aquarium conditions

Hydrogen sulfide is a highly toxic gas that causes many economic losses in aquaculture ponds. The application of sulfur-oxidizing bacteria (SOB) to remove hydrogen sulfide is an eco-friendly approach. This study aimed to isolate and identify the most efficient SOBs from the sediment of warm-water fish farms. Enrichment and isolation were performed in three different culture media (Starkey, Postgate, and H-3) based on both mineral and organic carbon. Overall, 27 isolates (14 autotrophic and 13 heterotrophic isolates) were purified based on colony and cell morphology differences. Initial screening was performed based on pH decrease. For final screening, the isolates were assessed based on their efficacy in thiosulfate oxidation and the sulfate production on Starkey liquid medium. Among isolated strains, 3 strains of Iran 2 (FH-13), Iran 3 (FH-21), and Iran 1 (FH-14) that belonged to Thiobacillus thioparus species (identified by 16s rRNA) showed the highest ability in thiosulfate oxidation (413.21, 1362.50, and 4188.03 mg/L for 14 days) and the highest sulfate production (3350, 2075, and 1600 mg/L). In the final phase, the performance of these strains under aquarium conditions showed that Iran 1 and Iran 2 had the highest ability in sulfur oxidation. In conclusion, Iran 1 and 2 strains can be used as effective SOB to remove hydrogen sulfide in fish farms. It is very important to evaluate strains in an appropriate strategy using a combination of different criteria to ensure optimal performance of SOB in farm conditions.

Spatial characterization of microbial sulfur cycling in horizontal-flow constructed wetland models

Constructed wetlands (CWs) are a cost-effective technology for wastewater treatment in which plant-microorganism relationships play a key role in transforming pollutants. However, there is little knowledge about the spatial organization of microbial metabolic processes in CWs. Here we show the structuring of microbial transformation of inorganic sulfur compounds (ISCs) in two horizontal subsurface-flow CW models fed with sulfate-rich artificial wastewater. One model was fully planted with Juncus effusus, while the other was planted only in the middle to investigate further the influence of the plant on ISC transformations. Chemical analyses revealed that sulfate reduction and re-oxidation of sulfide/sulfur occurred simultaneously along the flow paths, with net reduction at the beginning of the CWs, where organic carbon from the influent was still present, and predominant re-oxidation in the downstream sections. Porewater ISC concentrations hardly differed between the two CWs. However, analysis of the bacterial communities showed that sulfur cycling in the fully planted CW was much higher. Total bacterial abundances were about 50 times and 3-4 orders of magnitude higher in the rhizoplane than in porewater and on gravel, respectively, as quantified by qPCR determination of the 16S rRNA gene. Sequencing of 16S rRNA gene amplicons revealed that bacterial communities on the roots and in the porewater differed substantially, apparently a consequence of the fluxes of oxygen and exudates from the roots. Furthermore, we observed partitioning of ISC transforming bacteria into different niches of the CWs. The results of the chemical and microbial analyses collectively support that extensive sulfur cycling occurred in the rhizospheres of the CW models. The study is relevant to the treatment of sulfur-containing wastewater and the elucidation of microbial communities involved in biogeochemical activities to improve water quality.

Thiomicrorhabdus heinhorstiae sp. nov. and Thiomicrorhabdus cannonii sp. nov.: novel sulphur-oxidizing chemolithoautotrophs isolated from the chemocline of Hospital Hole, an anchialine sinkhole in Spring Hill, Florida, USA

Two sulphur-oxidizing, chemolithoautotrophic aerobes were isolated from the chemocline of an anchialine sinkhole located within the Weeki Wachee River of Florida. Gram-stain-negative cells of both strains were motile, chemotactic rods. Phylogenetic analysis of the 16S rRNA gene and predicted amino acid sequences of ribosomal proteins, average nucleotide identities, and alignment fractions suggest the strains HH1^T and HH3^T represent novel species belonging to the genus Thiomicrorhabdus. The genome G+C fraction of HH1^T is 47.8 mol% with a genome length of 2.61 Mb, whereas HH3^T has a G+C fraction of 52.4 mol% and 2.49 Mb genome length. Major fatty acids of the two strains included C_16 : 1, C_18 : 1 and C_16 : 0, with the addition of C_10:0 3-OH in HH1^T and C_12 : 0 in HH3^T. Chemolithoautotrophic growth of both strains was supported by elemental sulphur, sulphide, tetrathionate, and thiosulphate, and HH1^T was also able to use molecular hydrogen. Neither strain was capable of heterotrophic growth or use of nitrate as a terminal electron acceptor. Strain HH1^T grew from pH 6.5 to 8.5, with an optimum of pH 7.4, whereas strain HH3^T grew from pH 6 to 8 with an optimum of pH 7.5. Growth was observed between 15-35 °C with optima of 32.8 °C for HH1^T and 32 °C for HH3^T. HH1^T grew in media with [NaCl] 80-689 mM, with an optimum of 400 mM, while HH3^T grew at 80-517 mM, with an optimum of 80 mM. The name Thiomicrorhabdus heinhorstiae sp. nov. is proposed, and the type strain is HH1^T (=DSM 111584^T=ATCC TSD-240^T). The name Thiomicrorhabdus cannonii sp. nov is proposed, and the type strain is HH3^T (=DSM 111593^T=ATCC TSD-241^T).

Diversity and Metabolic Potentials of As(III)-Oxidizing Bacteria in Activated Sludge

Biological arsenite [As(III)] oxidation is an important process in the removal of toxic arsenic (As) from contaminated water. However, the diversity and metabolic potentials of As(III)-oxidizing bacteria (AOB) responsible for As(III) oxidation in wastewater treatment facilities are not well documented. In this study, two groups of bioreactors inoculated with activated sludge were operated under anoxic or oxic conditions to treat As-containing synthetic wastewater. Batch tests of inoculated sludges from the bioreactors further indicated that microorganisms could use nitrate or oxygen as electron acceptors to stimulate biological As(III) oxidation, suggesting the potentials of this process in wastewater treatment facilities. In addition, DNA-based stable isotope probing (DNA-SIP) was performed to identify the putative AOB in the activated sludge. Bacteria associated with Thiobacillus were identified as nitrate-dependent AOB, while bacteria associated with Hydrogenophaga were identified as aerobic AOB in activated sludge. Metagenomic binning reconstructed a number of high-quality metagenome-assembled genomes (MAGs) associated with the putative AOB. Functional genes encoding As resistance, As(III) oxidation, denitrification, and carbon fixation were identified in these MAGs, suggesting their potentials for chemoautotrophic As(III) oxidation. In addition, the presence of genes encoding secondary metabolite biosynthesis and extracellular polymeric substance metabolism in these MAGs may facilitate the proliferation of these AOB in activated sludge and enhance their capacity for As(III) oxidation. IMPORTANCE AOB play an important role in the removal of toxic arsenic from wastewater. Most of the AOB have been isolated from natural environments. However, knowledge regarding the structure and functional roles of As(III)-oxidizing communities in wastewater treatment facilities is not well documented. The combination of DNA-SIP and metagenomic binning provides an opportunity to elucidate the diversity of in situ AOB community inhabiting the activated sludges. In this study, the putative AOB responsible for As(III) oxidation in wastewater treatment facilities were identified, and their metabolic potentials, including As(III) oxidation, denitrification, carbon fixation, secondary metabolite biosynthesis, and extracellular polymeric substance metabolism, were investigated. This observation provides an understanding of anoxic and/or oxic AOB during the As(III) oxidation process in wastewater treatment facilities, which may contribute to the removal of As from contaminated water.

Parasulfuritortus cantonensis gen. nov., sp. nov., a microaerophilic sulfur-oxidizing bacterium isolated from freshwater sediment

A novel sulfur-oxidizing bacterium, designated strain LSR1^T, was enriched and isolated from a freshwater sediment sample collected from the Pearl River in Guangzhou, PR China. The strain was an obligate chemolithoautotroph, using thiosulfate or sulfide as an electron donor and energy source. Growth of strain LSR1^T was observed at 15-40 °C, pH 6.0-7.5 and NaCl concentrations of 0-1.5 %. Strain LSR1^T was microaerophilic, with growth only at oxygen content less than 10 %. Anaerobic growth was also observed when using nitrate as the sole electron acceptor. The major cellular fatty acids were C_16 : 0 and summed feature 3 (comprising C_16 : 1 ω7c and/or C_16 : 1 ω6c). The DNA G+C content of the draft genome sequence was 67.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LSR1^T formed a lineage within the family Thiobacillaceae, showing sequence identities of 92.87, 92.33 and 90.80 % with its closest relative genera Sulfuritortus, Annwoodia and Thiobacillus, respectively. The genome of strain LSR1^T contained multiple genes encoding sulfur-oxidizing enzymes that catalyse thiosulfate and sulfide oxidation, and the gene encoding cbb ₃-type cytochrome c oxidase and bd-type quinol oxidase, which enables strain LSR1^T to perform sulphur oxidation under microaerophilic conditions. On the basis of phenotypic, genotypic and phylogenetic results, strain LSR1^T is considered to represent a novel species of a new genus Parasulfuritortus within the family Thiobacillaceae, for which the name Parasulfuritortus cantonensis gen. nov., sp. nov. is proposed. The type strain is LSR1^T (=GDMCC 1.1549=JCM 33645).

Identification and Metabolism of Naturally Prevailing Microorganisms in Zinc and Copper Mineral Processing

It has only recently been discovered that naturally prevailing microorganisms have a notable role in flotation in addition to chemical process parameters and overall water quality. This study’s aim was to assess the prevailing microbial communities in relation to process chemistry in a zinc and copper mineral flotation plant. Due to the limitations of cultivation-based microbial methods that detect only a fraction of the total microbial diversity, DNA-based methods were utilised. However, it was discovered that the DNA extraction methods need to be improved for these environments with high mineral particle content. Microbial communities and metabolism were studied with quantitative PCR and amplicon sequencing of bacterial, archaeal and fungal marker genes and shotgun sequencing. Bacteria dominated the microbial communities, but in addition, both archaea and fungi were present. The predominant bacterial metabolism included versatile sulfur compound oxidation. Putative Thiovirga sp. dominated in the zinc plant and the water circuit samples, whereas Thiobacillus spp. dominated the copper plant. Halothiobacillus spp. were also an apparent part of the community in all samples. Nitrogen metabolism was more related to assimilatory than dissimilatory nitrate and nitrite oxidation/reduction reactions. Abundance of heavy metal resistance genes emphasized the adaptation and competitive edge of the core microbiome in these extreme conditions compared to microorganisms freshly entering the process.

Insights into growth kinetics and roles of enzymes of Krebs' cycle and sulfur oxidation during exochemolithoheterotrophic growth of Achromobacter aegrifaciens NCCB 38021 on succinate with thiosulfate as the auxiliary electron donor

Achromobacter aegrifaciens NCCB 38021 was grown heterotrophically on succinate versus exochemolithoheterotrophically on succinate with thiosulfate as auxiliary electron donor. In batch culture, no significant differences in specific molar growth yield or specific growth rate were found for the two growth conditions, but in continuous culture in the succinate-limited chemostat, the maximum specific growth yield coefficient increased by 23.3% with thiosulfate present, consistent with previous studies of endo- and exochemolithoheterotrophs and thermodynamic predictions. Thiosulfate oxidation was coupled to respiration at cytochrome c₅₅₁, and thiosulfate-dependent ATP biosynthesis occurred. Specific activities of cytochrome c-linked thiosulfate dehydrogenase (E.C. 1.8.2.2) and two other enzymes of sulfur metabolism were significantly higher in exochemolithoheterotrophically grown cell extracts, while those of succinyl-transferring 2-oxoglutarate dehydrogenase (E.C. 1.2.4.2), fumarate hydratase (E.C. 4.2.1.2) and malate dehydrogenase (NAD⁺, E.C. 1.1.1.37) were significantly lower-presumably owing to less need to generate reducing equivalents during Krebs' cycle, since they could be produced from thiosulfate oxidation.

Iron sulphides mediated autotrophic denitrification: An emerging bioprocess for nitrate pollution mitigation and sustainable wastewater treatment

Iron sulphides, mainly in the form of mackinawite (FeS), pyrrhotite (Fe_1-xS, x = 0-0.125) and pyrite (FeS₂), are the most abundant sulphide minerals and can be oxidized under anoxic and circumneutral pH conditions by chemoautotrophic denitrifying bacteria to reduce nitrate to N₂. Iron sulphides mediated autotrophic denitrification (ISAD) represents an important natural attenuation process of nitrate pollution and plays a pivotal role in linking nitrogen, sulphur and iron cycles in a variety of anoxic environments. Recently, it has emerged as a promising bioprocess for nutrient removal from various organic-deficient water and wastewater, due to its specific advantages including high denitrification capacity, simultaneous nitrogen and phosphorus removal, self-buffering properties, and fewer by-products generation (sulphate, waste sludge, N₂O, NH₄⁺, etc.). This paper provides a critical overview of fundamental and engineering aspects of ISAD, including the theoretical knowledge (biochemistry, and microbial diversity), its natural occurrence and engineering applications. Its potential and limitations are elucidated by summarizing the key influencing factors including availability of iron sulphides, low denitrification rates, sulphate emission and leaching heavy metals. This review also put forward two key questions in the mechanism of anoxic iron sulphides oxidation, i.e. dissolution of iron sulphides and direct substrates for denitrifiers. Finally, its prospects for future sustainable wastewater treatment are highlighted. An iron sulphides-based biotechnology towards next-generation wastewater treatment (NEO-GREEN) is proposed, which can potentially harness bioenergy in wastewater, incorporate resources (P and Fe) recovery, achieve simultaneous nutrient and emerging contaminants removal, and minimize waste sludge production.

Ridge Tillage Improves Soil Properties, Sustains Diazotrophic Communities, and Enhances Extensively Cooperative Interactions Among Diazotrophs in a Clay Loam Soil

Reduced tillage practices [such as ridge tillage (RT)] have been potential solutions to the weed pressures of long-term no tillage (NT) and the soil-intensive disturbances caused by conventional tillage [such as moldboard plow (MP) tillage]. Although soil diazotrophs are significantly important in global nitrogen (N) cycling and contribute to the pool of plant-available N in agroecosystems, little is currently known about the responses of diazotrophic communities to different long-term tillage practices. In the current study, we investigated the differences among the effects of NT, RT, and MP on soil properties, diazotrophic communities, and co-occurrence network patterns in bulk and rhizosphere soils under soybean grown in clay loam soil of Northeast China. The results showed that RT and MP led to higher contents of total C, N, and available K compared to NT in both bulk and rhizosphere soils, and RT resulted in higher soybean yield than NT and MP. Compared to NT and RT, MP decreased the relative abundances of free-living diazotrophs, while it promoted the growth of copiotrophic diazotrophs. Little differences of diazotrophic community diversity, composition, and community structure were detected between RT and NT, but MP obviously decreased diazotrophic diversity and changed the diazotrophic communities in contrast to NT and RT in bulk soils. Soil nitrogenous nutrients had negative correlations with diazotrophic diversity and significantly influenced the diazotrophic community structure. Across all diazotrophs' networks, the major diazotrophic interactions transformed into a cooperatively dominated network under RT, with more intense and efficient interactions among species than NT and MP. Overall, our study suggested that RT, with minor soil disturbances, could stabilize diazotrophic diversity and communities as NT and possessed highly positive interactions among diazotrophic species relative to NT and MP.

Form III RubisCO-mediated transaldolase variant of the Calvin cycle in a chemolithoautotrophic bacterium

The Calvin-Benson-Bassham (CBB) cycle assimilates CO₂ for the primary production of organic matter in all plants and algae, as well as in some autotrophic bacteria. The key enzyme of the CBB cycle, ribulose-bisphosphate carboxylase/oxygenase (RubisCO), is a main determinant of de novo organic matter production on Earth. Of the three carboxylating forms of RubisCO, forms I and II participate in autotrophy, and form III so far has been associated only with nucleotide and nucleoside metabolism. Here, we report that form III RubisCO functions in the CBB cycle in the thermophilic chemolithoautotrophic bacterium Thermodesulfobium acidiphilum, a phylum-level lineage representative. We further show that autotrophic CO₂ fixation in T. acidiphilum is accomplished via the transaldolase variant of the CBB cycle, which has not been previously demonstrated experimentally and has been considered unlikely to occur. Thus, this work reveals a distinct form of the key pathway of CO₂ fixation.

Microbial diversity along a gradient in peatlands treating mining-affected waters

Peatlands are used for the purification of mining-affected waters in Northern Finland. In Northern climate, microorganisms in treatment peatlands (TPs) are affected by long and cold winters, but studies about those microorganisms are scarce. Thus, the bacterial, archaeal and fungal communities along gradients of mine water influence in two TPs were investigated. The TPs receive waters rich in contaminants, including arsenic (As), sulfate (SO42-) and nitrate (NO3-). Microbial diversity was high in both TPs, and microbial community composition differed between the studied TPs. Bacterial communities were dominated by Proteobacteria, Actinobacteria, Chloroflexi and Acidobacteria, archaeal communities were dominated by Methanomicrobia and the Candidate phylum Bathyarchaeota, and fungal communities were dominated by Ascomycota (Leotiomycetes, Dothideomycetes, Sordariomycetes). The functional potential of the bacterial and archaeal communities in TPs was predicted using PICRUSt. Sampling points affected by high concentrations of As showed higher relative abundance of predicted functions related to As resistance. Functions potentially involved in nitrogen and SO42- turnover in TPs were predicted for both TPs. The results obtained in this study indicate that (i) diverse microbial communities exist in Northern TPs, (ii) the functional potential of the peatland microorganisms is beneficial for contaminant removal in TPs and (iii) microorganisms in TPs are likely well-adapted to high contaminant concentrations as well as to the Northern climate.

Paired RNA Radiocarbon and Sequencing Analyses Indicate the Importance of Autotrophy in a Shallow Alluvial Aquifer

Determining the carbon sources for active microbial populations in the subsurface is a challenging but highly informative component of subsurface microbial ecology. This work developed a method to provide ecological insights into groundwater microbial communities by characterizing community RNA through its radiocarbon and ribosomal RNA (rRNA) signatures. RNA was chosen as the biomolecule of interest because rRNA constitutes the majority of RNA in prokaryotes, represents recently active organisms, and yields detailed taxonomic information. The method was applied to a groundwater filter collected from a shallow alluvial aquifer in Colorado. RNA was extracted, radiometrically dated, and the 16S rRNA was analyzed by RNA-Seq. The RNA had a radiocarbon signature (Δ14C) of -193.4 ± 5.6‰. Comparison of the RNA radiocarbon signature to those of potential carbon pools in the aquifer indicated that at least 51% of the RNA was derived from autotrophy, in close agreement with the RNA-Seq data, which documented the prevalence of autotrophic taxa, such as Thiobacillus and Gallionellaceae. Overall, this hybrid method for RNA analysis provided cultivation-independent information on the in-situ carbon sources of active subsurface microbes and reinforced the importance of autotrophy and the preferential utilization of dissolved over sedimentary organic matter in alluvial aquifers.

Broad Phylogenetic Diversity Associated with Nitrogen Loss through Sulfur Oxidation in a Large Public Marine Aquarium

Denitrification by sulfur-oxidizing bacteria is an effective nitrate removal strategy in engineered aquatic systems. However, the community taxonomic and metabolic diversity of sulfur-driven denitrification (SDN) systems, as well as the relationship between nitrate removal and SDN community structure, remains underexplored. This is particularly true for SDN reactors applied to marine aquaria, despite the increasing use of this technology to supplement filtration. We applied 16S rRNA gene, metagenomic, and metatranscriptomic analyses to explore the microbial basis of SDN reactors operating on Georgia Aquarium's Ocean Voyager, the largest indoor closed-system seawater exhibit in the United States. The exhibit's two SDN systems vary in water retention time and nitrate removal efficiency. The systems also support significantly different microbial communities. These communities contain canonical SDN bacteria, including a strain related to Thiobacillus thioparus that dominates the system with the higher water retention time and nitrate removal but is effectively absent from the other system. Both systems contain a wide diversity of other microbes whose metagenome-assembled genomes contain genes of SDN metabolism. These include hundreds of strains of the epsilonproteobacterium Sulfurimonas, as well as gammaproteobacterial sulfur oxidizers of the Thiotrichales and Chromatiales, and a relative of Sedimenticola thiotaurini with complete denitrification potential. The SDN genes are transcribed and the taxonomic richness of the transcript pool varies markedly among the enzymatic steps, with some steps dominated by transcripts from noncanonical SDN taxa. These results indicate complex and variable SDN communities that may involve chemical dependencies among taxa as well as the potential for altering community structure to optimize nitrate removal.IMPORTANCE Engineered aquatic systems such as aquaria and aquaculture facilities have large societal value. Ensuring the health of animals in these systems requires understanding how microorganisms contribute to chemical cycling and waste removal. Focusing on the largest seawater aquarium in the United States, we explore the microbial communities in specialized reactors designed to remove excess nitrogen through the metabolic activity of sulfur-consuming microbes. We show that the diversity of microbes in these reactors is both high and highly variable, with distinct community types associated with significant differences in nitrogen removal rate. We also show that the genes encoding the metabolic steps of nitrogen removal are distributed broadly throughout community members, suggesting that the chemical transformations in this system are likely a result of microbes relying on other microbes. These results provide a framework for future studies exploring the contributions of different community members, both in waste removal and in structuring microbial biodiversity.

Evaluation of the genus Thiothrix Winogradsky 1888 (Approved Lists 1980) emend. Aruga et al. 2002: reclassification of Thiothrix disciformis to Thiolinea disciformis gen. nov., comb. nov., and of Thiothrix flexilis to Thiofilum flexile gen. nov., comb nov., with emended description of Thiothrix

Thiothrix is the type genus of the Thiotrichaceae in the Thiotrichales of the Gammaproteobacteria, comprising nine species of sulfur-oxidising filamentous bacteria, which are variously autotrophic, heterotrophic or have mixed metabolic modes. Within the genus, four species show 16S rRNA gene identities lower the Yarza threshold for the rank of genus (94.5 %) - Thiothrix disciformis, Thiothrix flexilis, Thiothrix defluvii and Thiothrix eikelboomii - as they show no affiliation to extant genera, a polyphasic study was undertaken including biochemical, physiological and genomic properties and phylogeny based on the 16S rRNA gene (rrs), recombination protein A (RecA), polynucleotide nucleotidyltransferase (Pnp), translation initiation factor IF-2 (InfB), glyceraldehyde-3-phosphate dehydrogenase (GapA), glutaminyl-tRNA synthetase (GlnS), elongation factor EF-G (FusA) and concatamers of 53 ribosomal proteins encoded by rps, rpl and rpm operons, all of which support the reclassification of these species. We thus propose Thiolinea gen. nov. and Thiofilum gen. nov. for which the type species are Thiolinea disciformis gen. nov., comb. nov. and Thiofilum flexile gen. nov., comb. nov. We also propose that these genera are each circumscribed into novel families Thiolinaceae fam. nov. and Thiofilaceae fam. nov., and that Leucothrix and Cocleimonas are circumscribed into Leucotrichaceaefam. nov. and provide emended descriptions of Thiothrix and Thiotrichaceae.

Genomes of ubiquitous marine and hypersaline Hydrogenovibrio, Thiomicrorhabdus and Thiomicrospira spp. encode a diversity of mechanisms to sustain chemolithoautotrophy in heterogeneous environments

Chemolithoautotrophic bacteria from the genera Hydrogenovibrio, Thiomicrorhabdus and Thiomicrospira are common, sometimes dominant, isolates from sulfidic habitats including hydrothermal vents, soda and salt lakes and marine sediments. Their genome sequences confirm their membership in a deeply branching clade of the Gammaproteobacteria. Several adaptations to heterogeneous habitats are apparent. Their genomes include large numbers of genes for sensing and responding to their environment (EAL- and GGDEF-domain proteins and methyl-accepting chemotaxis proteins) despite their small sizes (2.1-3.1 Mbp). An array of sulfur-oxidizing complexes are encoded, likely to facilitate these organisms' use of multiple forms of reduced sulfur as electron donors. Hydrogenase genes are present in some taxa, including group 1d and 2b hydrogenases in Hydrogenovibrio marinus and H. thermophilus MA2-6, acquired via horizontal gene transfer. In addition to high-affinity cbb₃ cytochrome c oxidase, some also encode cytochrome bd-type quinol oxidase or ba₃ -type cytochrome c oxidase, which could facilitate growth under different oxygen tensions, or maintain redox balance. Carboxysome operons are present in most, with genes downstream encoding transporters from four evolutionarily distinct families, which may act with the carboxysomes to form CO₂ concentrating mechanisms. These adaptations to habitat variability likely contribute to the cosmopolitan distribution of these organisms.

Isotopic Fractionation of Sulfur in Carbonyl Sulfide by Carbonyl Sulfide Hydrolase of Thiobacillus thioparus THI115

Carbonyl sulfide (COS) is one of the major sources of stratospheric sulfate aerosols, which affect the global radiation balance and ozone depletion. COS-degrading microorganisms are ubiquitous in soil and important for the global flux of COS. We examined the sulfur isotopic fractionation during the enzymatic degradation of COS by carbonyl sulfide hydrolase (COSase) from Thiobacillus thioparus THI115. The isotopic fractionation constant (34ɛ value) was -2.2±0.2‰. Under experimental conditions performed at parts per million by volume level of COS, the 34ɛ value for intact cells of T. thioparus THI115 was -3.6±0.7‰, suggesting that, based on Rees' model, the 34ɛ value mainly depended on COS transport into the cytoplasm. The 34ɛ value for intact cells of T. thioparus THI115 was similar to those for Mycobacterium spp. and Williamsia sp., which are known to involve the conserved region of nucleotide sequences encoding the clade D of β-class carbonic anhydrase (β-CA) including COSase. On the other hand, the 34ɛ value was distinct from those for bacteria in the genus Cupriavidus. These results provide an insight into biological COS degradation, which is indispensable for estimating the COS global budget based on the isotope because of the significant contribution of COS degradation by microorganisms harboring β-CA family enzymes.

Reclassification of Thiobacillus aquaesulis (Wood & Kelly, 1995) as Annwoodia aquaesulis gen. nov., comb. nov., transfer of Thiobacillus (Beijerinck, 1904) from the Hydrogenophilales to the Nitrosomonadales, proposal of Hydrogenophilalia class. nov. within the 'Proteobacteria', and four new families within the orders Nitrosomonadales and Rhodocyclales

The genus Thiobacillus comprises four species with validly published names, of which Thiobacillus aquaesulis DSM 4255T (=ATCC 43788T) is the only species that can grow heterotrophically or mixotrophically - the rest being obligate autotrophs - and has a significant metabolic difference in not producing tetrathionate during the oxidation of thiosulfate during autotrophic growth. On the basis of this and differential chemotaxonomic properties and a 16S rRNA gene sequence similarity of 93.4 % to the type species Thiobacillus thioparus DSM 505T, we propose that it is moved to a novel genus, Annwoodia gen. nov., for which the type species is Annwoodia aquaesulis gen. nov., comb. nov. We confirm that the position of the genus Thiobacillus in the Betaproteobacteria falls within the Nitrosomonadales rather than the Hydrogenophilales as previously proposed. Within the Nitrosomonadales we propose the circumscription of genera to form the Thiobacilliaceae fam. nov. and the Sterolibacteriaceae fam. nov. We propose the merging of the family Methylophilaceae into the Nitrosomonadales, and that the Sulfuricellaceae be merged into the Gallionellaceae, leaving the orders Methylophilales and Sulfuricellales defunct. In the Rhodocyclales we propose the Azonexaceae fam. nov. and the Zoogloeaceae fam. nov. We also reject the Hydrogenophilales from the Betaproteobacteria on the basis of a very low 16S rRNA gene sequence similarity with the class-proper as well as physiological properties, forming the Hydrogenophilalia class. nov. in the 'Proteobacteria'. We provide emended descriptions of Thiobacillus, Hydrogenophilales, Hydrogenophilaceae, Nitrosomonadales, Gallionellaceae, Rhodocyclaceae and the Betaproteobacteria.

Draft Genome Sequence of Thiohalobacter thiocyanaticus Strain FOKN1, a Neutrophilic Halophile Capable of Thiocyanate Degradation

A draft genome sequence of a neutrophilic halophile capable of thiocyanate degradation, Thiohalobacter thiocyanaticus FOKN1, was determined using a PacBio RSII sequencer. A 3.23-Mb circular genome sequence was assembled, in which 3,026 gene-coding sequences, 45 tRNAs, and 1 rrn operon were annotated.