Comparison of microbial communities in pilot-scale bioreactors treating Bayer liquor organic wastes.

Western Australian bauxite deposits are naturally associated with high amounts of humic and fulvic materials that co-digest during Bayer processing. Sodium oxalate remains soluble and can co-precipitate with aluminium hydroxide unless it is removed. Removal of sodium oxalate requires a secondary crystallisation step followed by storage. Bioreactors treating oxalate wastes have been developed as economically and environmentally viable treatment alternatives but the microbial ecology and physiology of these treatment processes are poorly understood. Analysis of samples obtained from two pilot-scale moving bed biofilm reactors (MBBRs) and one aerobic suspended growth bioreactor (ASGB) using polymerase chain reaction- denaturing gradient gel electrophoresis of 16S rRNA genes showed that members of the α-, ß- and γ-Proteobacteria subgroups were prominent in all three processes. Despite differing operating conditions, the composition of the microbial communities in the three reactors was conserved. MBBR2 was the only configuration that showed complete degradation of oxalate from the influent and the ASGB had the highest degradation rate of all three configurations. Several strains of the genus Halomonas were isolated from the bioreactors and their morphology and physiology was also determined.

Acidianus sulfidivorans sp. nov., an extremely acidophilic, thermophilic archaeon isolated from a solfatara on Lihir Island, Papua New Guinea, and emendation of the genus description.

A novel, extremely thermoacidophilic, obligately chemolithotrophic archaeon (strain JP7(T)) was isolated from a solfatara on Lihir Island, Papua New Guinea. Cells of this organism were non-motile, Gram-negative staining, irregular-shaped cocci, 0.5-1.5 microm in size, that grew aerobically by oxidation of sulfur, Fe(2+) or mineral sulfides. Cells grew anaerobically using Fe(3+) as a terminal electron acceptor and H(2)S as an electron donor but did not oxidize hydrogen with elemental sulfur as electron acceptor. Strain JP7(T) grew optimally at 74 degrees C (temperature range 45-83 degrees C) and pH 0.8-1.4 (pH range 0.35-3.0). On the basis of 16S rRNA gene sequence similarity, strain JP7(T) was shown to belong to the Sulfolobaceae, being most closely related to the type strains of Acidianus ambivalens (93.7 %) and Acidianus infernus (93.6 %). Cell-membrane lipid structure, DNA base composition and 16S rRNA gene sequence similarity data support the placement of this strain in the genus Acidianus. Differences in aerobic and anaerobic metabolism, temperature and pH range for growth, and 16S rRNA gene sequence differentiate strain JP7(T) from recognized species of the genus Acidianus, and an emendation of the description of the genus is proposed. Strain JP7(T) is considered to represent a novel species of the genus Acidianus, for which the name Acidianus sulfidivorans sp. nov. is proposed. The type strain is JP7(T) (=DSM 18786(T)=JCM 13667(T)).

Characterization of a thermophilic sulfur oxidizing enrichment culture dominated by a Sulfolobus sp. obtained from an underground hot spring for use in extreme bioleaching conditions.

A thermoacidophilic elemental sulfur and chalcopyrite oxidizing enrichment culture VS2 was obtained from hot spring run-off sediments of an underground mine. It contained only archaeal species, namely a Sulfolobus metallicus-related organism (96% similarity in partial 16S rRNA gene) and Thermoplasma acidophilum (98% similarity in partial 16S rRNA gene). The VS2 culture grew in a temperature range of 35-76 degrees C. Sulfur oxidation by VS2 was optimal at 70 degrees C, with the highest oxidation rate being 99 mg S(0 )l(-1 )day(-1). At 50 degrees C, the highest sulfur oxidation rate was 89 mg l(-1 )day(-1 )(in the presence of 5 g Cl(-) l(-1)). Sulfur oxidation was not significantly affected by 0.02-0.1 g l(-1) yeast extract or saline water (total salinity of 0.6 M) that simulated mine water at field application sites with availability of only saline water. Chloride ions at a concentration above 10 g l(-1) inhibited sulfur oxidation. Both granular and powdered forms of sulfur were bioavailable, but the oxidation rate of granular sulfur was less than 50% of the powdered form. Chalcopyrite concentrate oxidation (1% w/v) by the VS2 resulted in a 90% Cu yield in 30 days.

Ferroplasma cupricumulans sp. nov., a novel moderately thermophilic, acidophilic archaeon isolated from an industrial-scale chalcocite bioleach heap.

A new species of Archaea was isolated from an industrial mineral sulphide bioleach heap. Strain BH2, a non-motile pleomorphic coccus, was capable of chemomixotrophic growth on ferrous sulphate and yeast extract. Growth was not supported in the absence of yeast extract. Phylogenetic analysis based on the 16S rRNA gene showed that strain BH2 was most closely related to the species Ferroplasma acidiphilum; however, it showed only 95% sequence similarity with this species. Strain BH2 had a temperature optimum of 53.6 degrees C and a temperature range for growth between 22 and 63 degrees C. Thus, it is the first moderately thermophilic member of the genus Ferroplasma. The optimum pH for the growth of the strain occurred between pH 1.0 and 1.2 and the lowest pH at which growth was observed was 0.4. Based on 16S rRNA gene sequence analysis and other physiological characteristics, strain BH2 constitutes a new species within the genus Ferroplasma. The name Ferroplasma cupricumulans is proposed for the new species and strain BH2 (DSM 16651) is proposed as the type strain.

Novel thermophilic sulfate-reducing bacteria from a geothermally active underground mine in Japan.

Thermophilic sulfate-reducing bacteria were enriched from samples obtained from a geothermal underground mine in Japan. The enrichment cultures contained bacteria affiliated with the genera Desulfotomaculum, Thermanaeromonas, Thermincola, Thermovenabulum, Moorella, "Natronoanaerobium," and Clostridium. Two novel thermophilic sulfate-reducing strains, RL50JIII and RL80JIV, affiliated with the genera Desulfotomaculum and Thermanaeromonas, respectively, were isolated.

Effects of hydraulic retention time and sulfide toxicity on ethanol and acetate oxidation in sulfate-reducing metal-precipitating fluidized-bed reactor.

The effects of hydraulic retention time (HRT) and sulfide toxicity on ethanol and acetate utilization were studied in a sulfate-reducing fluidized-bed reactor (FBR) treating acidic metal-containing wastewater. The effects of HRT were determined with continuous flow FBR experiments. The percentage of ethanol oxidation was 99.9% even at a HRT of 6.5 h (loading of 2.6 g ethanol L(-1) d(-1)), while acetate accumulated in the FBR with HRTs below 12 h (loading of 1.4 g ethanol L(-1) d(-1)). Partial acetate utilization was accompanied by decreased concentrations of dissolved sulfide (DS) and alkalinity in the effluent, and eventually resulted in process failure when HRT was decreased to 6.1 h (loading of 2.7 g ethanol L(-1) d(-1)). Zinc and iron precipitation rates increased to over 600 mg L(-1) d(-1) and 300 mg L(-1) d(-1), respectively, with decreasing HRT. At HRT of 6.5 h, percent metal precipitation was over 99.9%, and effluent metal concentrations remained below 0.08 mg L(-1). Under these conditions, the alkalinity produced by substrate utilization increased the wastewater pH from 3 to 7.9-8.0. The percentage of electron flow from ethanol to sulfate reduction averaged 76 +/- 10% and was not affected by the HRT. The lowest HRT did not result in significant biomass washout from the FBR. The effect of sulfide toxicity on the sulfate-reducing culture was studied with batch kinetic experiments in the FBR. Noncompetitive inhibition model described well the sulfide inhibition of the sulfate-reducing culture. (DS) inhibition constants (K(i)) for ethanol and acetate oxidation were 248 mg S L(-1) and 356 mg S L(-1), respectively, and the corresponding K(i) values for H(2)S were 84 mg S L(-1) and 124 mg S L(-1). In conclusion, ethanol oxidation was more inhibited by sulfide toxicity than the acetate oxidation.

Simple organic electron donors support diverse sulfate-reducing communities in fluidized-bed reactors treating acidic metal- and sulfate-containing wastewater.

Bacterial diversity of lactate- and ethanol-utilizing sulfate-reducing fluidized-bed reactor (FBR) communities was investigated with culture-independent methods. The FBRs were fed for 500 days with synthetic mineral processing wastewater containing sulfate, zinc and iron with hydraulic retention time of 16-24 h. Sodium lactate or ethanol was used as electron donor for microbial sulfate reduction. For microbial characterization, 16S rRNA gene clone libraries and denaturing gradient gel electrophoresis (DGGE) fingerprinting were employed. The FBR communities were diverse and contained many previously undescribed bacteria. The clone library indicated significant differences between bacterial communities of the two reactors. Most notable was the large number of Proteobacterium sequences retrieved from the ethanol-fed reactor, whereas in the lactate-fed reactor, sequences clustering with Nitrospira phylum were most abundant. Ethanol-utilizing FBR culture was more diverse than the lactate-utilizing one. Some sequences from each reactor were closely related to known sulfate reducers, such as Desulfobacca acetoxidans, Desulforhabdus amnigenus, and species of Desulfovibrio. DGGE profiling showed some changes in the bacterial communities over 393 days of continuous FBR operation. This study showed that it is possible to maintain diverse sulfate-reducing consortia using simple electron donors, lactate or ethanol in an open engineered ecosystem.

Performance and ethanol oxidation kinetics of a sulfate-reducing fluidized-bed reactor treating acidic metal-containing wastewater.

The treatment of simulated acidic wastewater (pH 2.5-5) containing sulfate (1.0-2.2 g l(-1)), zinc (15-340 mg l(-1)) and iron (57 mg l(-1)) was studied in a sulfate-reducing fluidized-bed reactor (FBR) at 35 degrees C. The original lactate feed for enrichment and maintenance of the FBR culture was replaced stepwise with ethanol over 50 days. The robustness of the process was studied by increasing stepwise the Zn, sulfate and ethanol feed concentrations and decreasing the feed pH. The following precipitation rates were obtained: 360 mg l(-1) d(-1) for Zn and 86 mg l(-1) d(-1) for Fe, with over 99.8% Zn and Fe removal, with a hydraulic retention time of 16 h. Under these conditions, 77-95% of the electrons were accepted by sulfate reduction. The alkalinity produced from ethanol oxidation increased the wastewater pH from 2.5 to 7.5-8.5. Michaelis-Menten constants (Km) determined in batch FBR experiments, were 4.3-7.1 mg l(-1) and 2.7-3.5 mg l(-1) for ethanol and acetate oxidation, respectively. The maximum oxidation velocities (Vmax) were 0.19-0.22 mg gVS(-1) min(-1) and 0.033-0.035 mg gVS(-1) min(-1), for ethanol and acetate, respectively. In summary, the FBR process produced a good quality effluent as indicated by its low organic content and Zn and Fe concentrations below 0.1 mg l(-1).

Mechanisms of thermal adaptation revealed from the genomes of the Antarctic Archaea Methanogenium frigidum and Methanococcoides burtonii.

We generated draft genome sequences for two cold-adapted Archaea, Methanogenium frigidum and Methanococcoides burtonii, to identify genotypic characteristics that distinguish them from Archaea with a higher optimal growth temperature (OGT). Comparative genomics revealed trends in amino acid and tRNA composition, and structural features of proteins. Proteins from the cold-adapted Archaea are characterized by a higher content of noncharged polar amino acids, particularly Gln and Thr and a lower content of hydrophobic amino acids, particularly Leu. Sequence data from nine methanogen genomes (OGT 15 degrees -98 degrees C) were used to generate 1111 modeled protein structures. Analysis of the models from the cold-adapted Archaea showed a strong tendency in the solvent-accessible area for more Gln, Thr, and hydrophobic residues and fewer charged residues. A cold shock domain (CSD) protein (CspA homolog) was identified in M. frigidum, two hypothetical proteins with CSD-folds in M. burtonii, and a unique winged helix DNA-binding domain protein in M. burtonii. This suggests that these types of nucleic acid binding proteins have a critical role in cold-adapted Archaea. Structural analysis of tRNA sequences from the Archaea indicated that GC content is the major factor influencing tRNA stability in hyperthermophiles, but not in the psychrophiles, mesophiles or moderate thermophiles. Below an OGT of 60 degrees C, the GC content in tRNA was largely unchanged, indicating that any requirement for flexibility of tRNA in psychrophiles is mediated by other means. This is the first time that comparisons have been performed with genome data from Archaea spanning the growth temperature extremes from psychrophiles to hyperthermophiles.

Effects of temperature on mineralisation of petroleum in contaminated Antarctic terrestrial sediments.

Although petroleum contamination has been identified at many Antarctic research stations, and is recognized as posing a significant threat to the Antarctic environment, full-scale in situ remediation has not yet been used in Antarctica. This is partly because it has been assumed that temperatures are too low for effective biodegradation. To test this, the effects of temperature on the hydrocarbon mineralisation rate in Antarctic terrestrial sediments were quantified. 14C-labelled octadecane was added to nutrient amended microcosms that were incubated over a range of temperatures between -2 and 42 degrees C. We found a positive correlation between temperature and mineralisation rate, with the fastest rates occurring in samples incubated at the highest temperatures. At temperatures below or near the freezing point of water there was a virtual absence of mineralisation. High temperatures (37 and 42 degrees C) and the temperatures just above the freezing point of water (4 degrees C) showed an initial mineralisation lag period, then a sharp increase in the mineralisation rate before a protracted plateau phase. Mineralisation at temperatures between 10 and 28 degrees C had no initial lag phase. The high rate of mineralisation at 37 and 42 degrees C was surprising, as most continental Antarctic microorganisms described thus far have an optimal temperature for growth of between 20 and 30 degrees C and a maximal growth temperature <37 degrees C. The main implications for bioremediation in Antarctica from this study are that a high-temperature treatment would yield the most rapid biodegradation of the contaminant. However, in situ biodegradation using nutrients and other amendments is still possible at soil temperatures that occur naturally in summer at the Antarctic site we studies (Casey Station 66 degrees 17(') S, 110 degrees 32(') E), although treatment times could be excessively long.