Comparison of the Bacterial Communities in Anaerobic, Anoxic, and Oxic Chambers of a Pilot A2O Process Using Pyrosequencing Analysis

A₂O process is a sequential wastewater treatment process that uses anaerobic, anoxic, and oxic chambers for nitrogen and phosphorus removal. In this study, the bacterial communities among these chambers were compared, and the diversity of the bacteria involved in nitrogen and phosphorus removal was surveyed. A pilot-scale A₂O process (50 m³ day^?1) was operated for more than 6 months, and bacterial 16S rRNA gene diversity was analyzed using pyrosequencing. A total of 7,447 bacterial sequence reads were obtained from anaerobic (1,546), anoxic (2,158), and oxic (3,743) chambers. Even though there were differences in the atmospheric condition and functionality, no prominent differences could be found in the bacterial community of the three chambers of the pilot A₂O process. All sequence reads, which were taxonomically analyzed using the Eztaxon-e database, were assigned into 638 approved or tentative genera. Among them, about 72.2 % of the taxa were contained in the phyla Proteobacteria and Bacteroidetes. Phosphate-accumulating bacteria, Candidatus Accumulibacter phosphatis, and two other Accumulibacter were found to constitute 3.1 % of the identified genera. Ammonia-oxidizing bacteria, Nitrosomonas oligotropha, and four other phylotypes in the same family, Nitrosomonadaceae, constituted 0.2 and 0.9 %, respectively. Nitrite-oxidizing bacteria, Nitrospira defluvii, and other three phylotypes in the same family, Nitrospiraceae, constituted 2.5 and 0.1 %, respectively. In addition, Dokdonella and a phylotype of the phylum Chloroflexi, function in nitrogen and/or phosphate removal of which have not been reported in the A₂O process, constituted the first and third composition among genera at 4.3 and 3.8 %, respectively.     

Diversity of Both the Cultivable Protease-Producing Bacteria and Their Extracellular Proteases in the Sediments of the South China Sea

Protease-producing bacteria are known to play an important role in degrading sedimentary particular organic nitrogen, and yet, their diversity and extracellular proteases remain largely unknown. In this paper, the diversity of the cultivable protease-producing bacteria and their extracellular proteases in the sediments of the South China Sea was investigated. The richness of the cultivable protease-producing bacteria reached 10⁶ cells/g in all sediment samples. Analysis of the 16S rRNA gene sequences revealed that the predominant cultivated protease-producing bacteria are Gammaproteobacteria affiliated with the genera Pseudoalteromonas, Alteromonas, Marinobacter, Idiomarina, Halomonas, Vibrio, Shewanella, Pseudomonas, and Rheinheimera, with Alteromonas (34.6%) and Pseudoalteromonas (28.2%) as the predominant groups. Inhibitor analysis showed that nearly all the extracellular proteases from the bacteria are serine proteases or metalloproteases. Moreover, these proteases have different hydrolytic ability to different proteins, reflecting they may belong to different kinds of serine proteases or metalloproteases. To our knowledge, this study represents the first report of the diversity of bacterial proteases in deep-sea sediments.     

Diversity of Both the Cultivable Protease-Producing Bacteria and Bacterial Extracellular Proteases in the Coastal Sediments of King George Island,Antarctica

Protease-producing bacteria play a vital role in degrading sedimentary organic nitrogen. However, the diversity of these bacteria and their extracellular proteases in most regions remain unknown. In this paper, the diversity of the cultivable protease-producing bacteria and of bacterial extracellular proteases in the sediments of Maxwell Bay, King George Island, Antarctica was investigated. The cultivable protease-producing bacteria reached 10⁵ cells/g in all 8 sediment samples. The cultivated protease-producing bacteria were mainly affiliated with the phyla Actinobacteria, Firmicutes, Bacteroidetes, and Proteobacteria, and the predominant genera were Bacillus (22.9%), Flavobacterium (21.0%) and Lacinutrix (16.2%). Among these strains, Pseudoalteromonas and Flavobacteria showed relatively high protease production. Inhibitor analysis showed that nearly all the extracellular proteases from the bacteria were serine proteases or metalloproteases. These results begin to address the diversity of protease-producing bacteria and bacterial extracellular proteases in the sediments of the Antarctic Sea.     

Spatiotemporal distribution of bacteriochlorophylls in the meromictic Lake Suigetsu, Japan

The spatiotemporal distribution of chlorophyll pigments (chloropigments) in the water column of a meromictic lake, Lake Suigetsu (Fukui, Japan), was investigated. Water samples were collected from the central basin of Lake Suigetsu bimonthly between May 2008 and March 2010 at appropriate depths, including the oxic surface, oxic–anoxic interface, and anoxic bottom layers. Chlorophyll a, related to cyanobacteria and eukaryotic phytoplankton, was detected throughout the water column during the years of the study, whereas bacteriochlorophyll e, related to brown-colored green sulfur bacteria, was detected in the anoxic layers below the chemocline at a maximum concentration of 825 μg L^?1. The concentration of bacteriochlorophyll e was generally maximal at or just below the chemocline of the lake. The cellular content of bacteriochlorophyll e was estimated to be low in the upper part of the chemocline and tended to increase with increasing water depth. Bacteriochlorophyll a, which was presumably related to purple sulfur bacteria, was only detected at the chemocline during summer and autumn at concentrations of 5.4–16.3 μg L^?1. Our analysis of the chloropigment distribution for the two years of the study suggested that brown-colored green sulfur bacteria are the predominant phototroph in the anoxic layers of Lake Suigetsu, and that these play a significant role in the carbon and sulfur cycling of the lake, especially from spring to summer.     

Vertical distribution of diazotrophic bacterial community associated with temperature and oxygen gradients in a subtropical reservoir

Nitrogen-fixing microorganisms play important roles in the structure and function of aquatic ecosystems. However, the diversity and distribution of diazotrophic bacteria along the lake depth continuum are so far poorly understood. In this study, we investigated the dynamic variations of diazotrophs in a subtropical deep reservoir during the stratified period. We applied an in-depth biomolecular approach (DGGE, clone libraries, and quantitative real-time PCR) to explore the nitrogenase (nifH) gene diversity and abundance. The diazotrophic community shifted between the oxic/anoxic interface and the nifH diversity increased with depth. The Cyanobacteria, affiliated to the toxic bloom-forming Cylindrospermopsis raciborskii, were the dominant diazotrophic cluster in the surface waters, whereas diazotrophic Alphaproteobacteria were dominant in the bottom waters. The relationships between microbial and environmental factors clearly demonstrated that the temperature gradient and the oxygen concentration affect the heterogeneity of the diazotrophic community, thereby influencing the entire aquatic nitrogen cycle.     

Prokaryotic diversity in a Tunisian hypersaline lake,Chott El Jerid

Prokaryotic diversity was investigated in a Tunisian salt lake, Chott El Jerid, by quantitative real-time PCR, denaturing gradient gel electrophoresis (DGGE) fingerprinting methods targeting the 16S rRNA gene and culture-dependent methods. Two different samples S1-10 and S2-10 were taken from under the salt crust of Chott El Jerid in the dry season. DGGE analysis revealed that bacterial sequences were related to Firmicutes, Proteobacteria, unclassified bacteria, and Deinococcus-Thermus phyla. Anaerobic fermentative and sulfate-reducing bacteria were also detected in this ecosystem. Within the domain archaea, all sequences were affiliated to Euryarchaeota phylum. Quantitative real-time PCR showed that 16S rRNA gene copy numbers of bacteria was 5 × 10⁶ DNA copies g^?1 whereas archaea varied between 5 × 10⁵ and 10⁶ DNA copies g^?1 in these samples. Eight anaerobic halophilic fermentative bacterial strains were isolated and affiliated with the species Halanaerobium alcaliphilum, Halanaerobium saccharolyticum, and Sporohalobacter salinus. These data showed an abundant and diverse microbial community detected in the hypersaline thalassohaline environment of Chott El Jerid.     

Isolation and phylogenetic analysis of cultivable manganese bacteria in sediments from the Arctic Ocean

Isolation, molecular identification and phylogenetic analysis were carried out to investigate the biodiversity of manganese bacteria in sediments which were collected from the Arctic Ocean during the 2nd Chinese Arctic Scientific Expedition. 21 and 19 species of cultivable strains were isolated from sediments at Stations P11 and S11, respectively, according to their distinct morphological character on the screening plate of manganese medium. Molecular identification and phylogenetic analysis showed that the cultivable manganese bacteria from Station P11 were basically composed of γ-Proteobacteria (γ subgroup of the Proteobacteria branch of the domain Bacteria) and Actinobacteria, which accounted for 86% and 14%, respectively. The isolates of γ-Proteobacteria mainly included Psychrobacter, Shewanella, Acinetobacter and Marinobacter, of which Psychrobacter was the major genus, which accounted for 67% of the γ-Proteobacteria. The cultivable manganese bacteria from Station S11 included α-Proteobacteria, γ-Proteobacteria and Flavobacteria of Bacteroides. The γ-Proteobacteria mainly included Shewanella, Marinomonas and Alteromonas. The majority of α-Proteobacteria was Sphingomonas. The phylogenetic analysis indicated that bacteria from sediments at Stations P11 and S11 had different cultivable manganese microbial communities. All tested strains had higher resistance to Mn2+, of which Marinomonas sp. S11-S-4 had the highest resistant ability.     

Seasonal dynamics of ammonia/ammonium-oxidizing prokaryotes in oxic and anoxic wetland sediments of subtropical coastal mangrove

Mangrove wetlands are an important ecosystem in tropical and subtropical regions, and the sediments may contain both oxic and anoxic zones. In this study, ammonia/ammonium-oxidizing prokaryotes (AOPs) in yellow and black sediments with vegetation and non-vegetated sediments in a mangrove wetland of subtropical Hong Kong were investigated in winter and summer. The phylogenetic diversity of anammox bacterial 16S rRNA genes and archaeal and bacterial amoA genes (encoding ammonia monooxygenase alpha-subunit) were analyzed using PCR amplification and denaturing gradient gel electrophoresis to reveal their community structures. Quantitative PCR was also used to detect their gene abundances. The results showed that seasonality had little effect, but sediment type had a noticeable influence on the community structures and abundances of anammox bacteria. For ammonia-oxidizing archaea (AOA), seasonality had a small effect on their community structures, but a significant effect on their abundances: AOA amoA genes were significantly higher in winter than in summer. In winter, the vegetated yellow sediments had lower AOA amoA genes than the other types of sediments, but in summer, the vegetated yellow sediments had higher AOA amoA genes than the other types of sediments. Sediment type had no apparent effect on AOA community structures in winter. In summer, however, the vegetated yellow sediments showed obviously different AOA community structures from the other types of sediments. For ammonia-oxidizing bacteria (AOB), seasonality had a significant effect on their community structures and abundances: AOB amoA genes in winter were apparently higher than in summer, and AOB community structures were different between winter and summer. Sediment type had little effect on AOB community structures, but had a noticeable effect on the abundances: AOB amoA genes of the vegetated yellow sediments were obviously lower than the black ones in both seasons. This study has demonstrated that seasonality and sediment type affected community structures and abundances of AOPs differently in oxic and anoxic sediments of the mangrove wetland.     

Abundant Trimethylornithine Lipids and Specific Gene Sequences Are Indicative of Planctomycete Importance at the Oxic/Anoxic Interface in Sphagnum-Dominated Northern Wetlands

Northern wetlands make up a substantial terrestrial carbon sink and are often dominated by decay-resistant Sphagnum mosses. Recent studies have shown that planctomycetes appear to be involved in degradation of Sphagnum-derived debris. Novel trimethylornithine (TMO) lipids have recently been characterized as abundant lipids in various Sphagnum wetland planctomycete isolates, but their occurrence in the environment has not yet been confirmed. We applied a combined intact polar lipid (IPL) and molecular analysis of peat cores collected from two northern wetlands (Saxnäs Mosse [Sweden] and Obukhovskoye [Russia]) in order to investigate the preferred niche and abundance of TMO-producing planctomycetes. TMOs were present throughout the profiles of Sphagnum bogs, but their concentration peaked at the oxic/anoxic interface, which coincided with a maximum abundance of planctomycete-specific 16S rRNA gene sequences. The sequences detected at the oxic/anoxic interface were affiliated with the Isosphaera group, while sequences present in the anoxic peat layers were related to an uncultured planctomycete group. Pyrosequencing-based analysis identified Planctomycetes as the major bacterial group at the oxic/anoxic interface at the Obukhovskoye peat (54% of total 16S rRNA gene sequence reads), followed by Acidobacteria (19% reads), while in the Saxnäs Mosse peat, Acidobacteria were dominant (46%), and Planctomycetes contributed to 6% of the total reads. The detection of abundant TMO lipids in planctomycetes isolated from peat bogs and the lack of TMO production by cultures of acidobacteria suggest that planctomycetes are the producers of TMOs in peat bogs. The higher accumulation of TMOs at the oxic/anoxic interface and the change in the planctomycete community with depth suggest that these IPLs could be synthesized as a response to changing redox conditions at the oxic/anoxic interface.     

Seasonal and altitudinal changes of culturable bacterial and yeast diversity in Alpine forest soils

The effect of altitude and season on abundance and diversity of the culturable heterotrophic bacterial and yeast community was examined at four forest sites in the Italian Alps along an altitude gradient (545–2000 m). Independently of altitude, bacteria isolated at 0 °C (psychrophiles) were less numerous than those recovered at 20 °C. In autumn, psychrophilic bacterial population increased with altitude. The 1194 bacterial strains were primarily affiliated with the classes Alpha-, Beta-, Gammaproteobacteria, Spingobacteriia and Flavobacteriia. Fifty-seven of 112 operational taxonomic units represented potential novel species. Strains isolated at 20 °C had a higher diversity and showed similarities in taxa composition and abundance, regardless of altitude or season, while strains isolated at 0 °C showed differences in community composition at lower and higher altitudes. In contrast to bacteria, yeast diversity was season-dependent: site- and altitude-specific effects on yeast diversity were only detected in spring. Isolation temperature affected the relative proportions of yeast genera. Isolations recovered 719 strains, belonging to the classes Dothideomycetes, Saccharomycetes, Tremellomycetes and Mycrobotryomycetes. The presence of few dominant bacterial OTUs and yeast species indicated a resilient microbial population that is not affected by season or altitude. Soil nutrient contents influenced significantly abundance and diversity of culturable bacteria, but not of culturable yeasts.     

Microbial Diversity in Water and Sediment of Lake Chaka, an Athalassohaline Lake in Northwestern China

We employed culture-dependent and -independent techniques to study microbial diversity in Lake Chaka, a unique hypersaline lake (32.5% salinity) in northwest China. It is situated at 3,214 m above sea level in a dry climate. The average water depth is 2 to 3 cm. Halophilic isolates were obtained from the lake water, and halotolerant isolates were obtained from the shallow sediment. The isolates exhibited resistance to UV and gamma radiation. Microbial abundance in the sediments ranged from 10⁸ cells/g at the water-sediment interface to 10⁷ cells/g at a sediment depth of 42 cm. A major change in the bacterial community composition was observed across the interface. In the lake water, clone sequences affiliated with the Bacteroidetes were the most abundant, whereas in the sediments, sequences related to low G+C gram-positive bacteria were predominant. A similar change was also present in the archaeal community. While all archaeal clone sequences in the lake water belonged to the Halobacteriales, the majority of the sequences in the sediments were related to those previously obtained from methanogenic soils and sediments. The observed changes in the microbial community structure across the water-sediment interface were correlated with a decrease in salinity from the lake water (32.5%) to the sediments (approximately 4%). Across the interface, the redox state also changed from oxic to anoxic and may also have contributed to the observed shift in the microbial community.     

Dominant bacterioplankton populations in the meromictic Lake Suigetsu as determined by denaturing gradient gel electrophoresis of 16S rRNA gene fragments

Lake Suigetsu is a typical meromictic lake in Japan characterized by a permanent chemocline at a depth of between 3 and 8 m separating the oxic freshwater mixolimnion from anoxic saline sulfidogenic monimolimnion. Dominant bacterioplankton populations in Lake Suigetsu were investigated using PCR-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments. The bacterial population was vertically stratified, and temporal shifts in the microbial communities were observed in both the oxic and anoxic layers of Lake Suigetsu during the sampling period. Several dominant DGGE bands were excised and sequenced. In the chemocline, green sulfur bacteria phylogenetically related to the genera Prosthecochloris, Pelodyctyon, and Chlorobium within the phylum Chlorobi were dominant; the colorless sulfur bacteria closely related to the genus Thiomicrospira were detected. These sulfur bacterial groups appear to be important in the biogeochemical cycling of sulfur and/or carbon in Lake Suigetsu. Bacterial sequences affiliated with the Bacteroidetes phylum were frequent among the dominant fragments in the DGGE profiles throughout the water column. Populations possessing a fermentative metabolism exist in Bacteroidetes, suggesting they may contribute to the degradation of organic matter in the anoxic environment of Lake Suigetsu.     

Distribution of anammox bacteria in domestic WWTPs and their enrichments evaluated by real-time quantitative PCR

Enrichment of anaerobic ammonium oxidation (anammox) bacteria using five activated sludges in three domestic wastewater treatment plants (WWTPs) were processed in a short term of 70 days and evaluated by real-time quantitative PCR (RTQ-PCR). Before the enrichment, building phylogenetic trees of Planctomycetes phylum in four reactors of sequencing batch reactor (SBR), anoxic and oxic reactors of anaerobic–anoxic–oxic (A2O) process, and rotating biological contactor (RBC) revealed six groups of distantly relative genera of Planctomyces, Pirellula, Gemmata, Isophaera, Candidatus and putative anammox bacteria. All clones of Candidatus sp. were affiliated with anammox bacteria and the majority of anammox clones were related to Planctomycete KSU-1 (AB057453). The discovery of anammox bacteria in raw activated sludges provided a partial rationale for the utilization of activated sludge as a seeding source of the anammox process. To verify the activity of anammox bacteria in the activated sludges, enrichment cultivations were conducted using SBRs. The enrichment of anammox bacteria resulted in the significant anammox activity of three samples. Quantification of 16S rRNA gene of anammox bacteria using RTQ-PCR showed the highest concentration of anammox bacteria of 2.48 ± 0.22 × 10⁹ copies of 16S rRNA gene/mg-volatile suspended solids (VSS), which was the same order of magnitude as that of the referential granular anammox sludge, 6.23 ± 0.59 × 10⁹ copies of 16S rRNA gene/mg-VSS, taken from an anammox upflow anaerobic sludge blanket (UASB) reactor. The doubling time of anammox bacteria enriched in this study was 1.18 days. The growth yield of anammox bacteria enriched in this study was 4.75 ± 0.57 × 10⁶ copies of 16S rRNA gene/mg of ammonium- and nitrite-nitrogen, which was similar to 4.50 ± 0.61 × 10⁶ copies of 16S rRNA gene/mg of ammonium- and nitrite-nitrogen for the referential anammox sludge. Substrate uptake rates of three successful enrichments at the end of the enrichment were comparable to those of granular and suspended anammox sludges. Rapid enrichment of anammox bacteria using activated sludge could offer an alternative method for obtaining a large volume of seeding anammox sludge.     

Incorporation of Glucose under Anoxic Conditions by Bacterioplankton from Coastal North Sea Surface Waters

It has been hypothesized that the potential for anaerobic metabolism might be a common feature of bacteria in coastal marine waters (L. Riemann and F. Azam, Appl. Environ. Microbiol. 68: 5554-5562, 2002). Therefore, we investigated whether different phylogenetic groups of heterotrophic picoplankton from the coastal North Sea were able to take up a simple carbon source under anoxic conditions. Oxic and anoxic incubations (4 h) or enrichments (24 h) of seawater with radiolabeled glucose were performed in July and August 2003. Bacteria with incorporated substrate were identified by using a novel protocol in which we combined fluorescence in situ hybridization and microautoradiography of cells on membrane filters. Incorporation of glucose under oxic and anoxic conditions was found in α-Proteobacteria, γ-Proteobacteria, and the Cytophaga-Flavobacterium cluster of the Bacteroidetes at both times, but not in marine Euryarchaeota. In July, the majority of cells belonging to the α-proteobacterial Roseobacter clade showed tracer incorporation both in oxic incubations and in oxic and anoxic enrichments. In August, only a minority of the Roseobacter cells, but most bacteria affiliated with Vibrio spp., were able to incorporate the tracer under either condition. A preference for glucose uptake under anoxic conditions was observed for bacteria related to Alteromonas and the Pseudoalteromonas-Colwellia group. These genera are commonly considered to be strictly aerobic, but facultatively fermentative strains have been described. Our findings suggest that the ability to incorporate substrates anaerobically is widespread in pelagic marine bacteria belonging to different phylogenetic groups. Such bacteria may be abundant in fully aerated coastal marine surface waters.     

Isolation and Characterization of Iron and Sulfur-Oxidizing Bacteria from Maiduk Copper Mine at Shahrbabk Province in Iran

Microbial oxidation of iron and sulfur are important steps in biogeochemical cycles in mining environments. The aim of this study was the enrichment and identification of two important groups of bacteria that are involved in bioleaching of copper ores. Some soil samples were collected from the Maiduk copper mine. Iron-oxidizing bacteria were enriched in 9K medium containing ferrous sulfate, and sulfur oxidizers were enriched in 9K medium containing powdered sulfur instead of ferrous sulfate as energy source. After three subcultures, autotrophic bacteria were isolated on 9K agarose medium with appropriate energy sources. The autotrophic bacteria from the enrichments were identified by amplification of 16S rRNA gene and sequencing. Bioleaching experiments were performed in 100 ml of 9K medium containing 5 g of low-grade copper ore instead of ferrous sulfate. Twelve different iron and sulfur-oxidizing bacteria were isolated from the collected soil samples of Maiduk copper mine. Molecular identification indicated that two prevalent strains in the ore enrichments could be assigned to the Acidithiobacillus ferooxidans strain HGM and the Thiobacillus thioparus strain HGE. These two strains reached their logarithmic phase of growth after 8 days of incubation in their respective media at 30°C. Of these two cultures, strain HGM leached more copper ore (300 ppm) from the Maiduk copper ore than did strain HGE (200 ppm). Application of these two strains to the Maiduk copper ore in situ and to ore heaps should improve the leaching process.     

Novel Bacterial Lineages at the (Sub)Division Level as Detected by Signature Nucleotide-Targeted Recovery of 16S rRNA Genes from Bulk Soil and Rice Roots of Flooded Rice Microcosms

Using a newly developed 16S rRNA gene (rDNA)-targeted PCR assay with proposed group specificity for planctomycetes, we examined anoxic bulk soil of flooded rice microcosms for the presence of novel planctomycete-like diversity. For comparison, oxic rice roots were included as an additional sample in this investigation. The bacterial diversity detectable by this PCR assay was assessed by using a combined approach that included terminal restriction fragment length polymorphism (T-RFLP) analysis and comparative sequence analysis of cloned 16S rDNA. T-RFLP fingerprint patterns generated from rice roots contained 12 distinct terminal restriction fragments (T-RFs). In contrast, the T-RFLP fingerprint patterns obtained from the anoxic bulk soil contained 33 distinct T-RFs, a clearly higher level of complexity. A survey of 176 bulk soil 16S rDNA clone sequences permitted correlation of 20 T-RFs with phylogenetic information. The other 13 T-RFs remained unidentified. The predominant T-RFs obtained from rice roots could be assigned to members of the genus Pirellula within the Planctomycetales, while most of the T-RFs obtained from the bulk soil corresponded to novel lines of bacterial descent. Using a level of 16S rDNA sequence dissimilarity to cultured microorganisms of approximately 20% as a threshold value, we detected 11 distinct bacterial lineages for which pure-culture representatives are not known. Four of these lineages could be assigned to the order Planctomycetales, while one lineage was affiliated with the division Verrucomicrobia and one lineage was affiliated with the spirochetes. The other five lineages either could not be assigned to any of the main lines of bacterial descent or clearly expanded the known diversity of division level lineages WS3 and OP3. Our results indicate the presence of bacterial diversity at a subdivision and/or division level that has not been detected previously by the so-called universal 16S rDNA PCR assays.     

Agar-degrading bacteria isolated from Antarctic macroalgae

This study describes the taxonomic diversity of pigmented, agar-degrading bacteria isolated from the surface of macroalgae collected in King George Island, Antarctica. A total of 30 pigmented, agarolytic bacteria were isolated from the surface of the Antarctic macroalgae Adenocystis utricularis, Monostroma hariotii, Iridaea cordata, and Pantoneura plocamioides. Based on the 16S rRNA data, the agarolytic isolates were affiliated to the genera Algibacter, Arthrobacter, Brachybacterium, Cellulophaga, Citricoccus, Labedella, Microbacterium, Micrococcus, Salinibacterium, Sanguibacter, and Zobellia. Isolates phylogenetically related to Cellulophaga algicola showed the highest agarase activity in culture supernatants when tested at 4 and 37 °C. This is the first investigation of pigmented agar-degrading bacteria, members of microbial communities associated with Antarctic macroalgae, and the results suggest that they represent a potential source of cold-adapted agarases of possible biotechnological interest.     

Bacterial diversity of extremely alkaline bauxite residue site of alumina industrial plant using culturable bacteria and residue 16S rRNA gene clones

Bauxite residue (red mud), generated during the extraction of alumina from bauxite ore is characterized by high pH, high concentrations of soluble ions with low or virtually no organic matter. These extreme conditions along with numerous nutrient deficiencies, limit the microbial growth and vegetation establishment. In the present study, diversity of both cultivable and non-cultivable bacteria present in the red mud was investigated by 16S rDNA sequence analyses. The cultivable bacteria were identified as Agromyces indicus, Bacillus litoralis, B. anthracis, Chungangia koreensis, Kokuria flava, K. polaris, Microbacterium hominis, Planococcus plakortidis, Pseudomonas alcaliphila and Salinococcus roseus based on their 16S rDNA sequence analysis. These isolates were alkali tolerant, positive for one or more of the enzyme activities tested, able to produce organic acids and oxidize wide range of carbon substrates. For non-cultivable diversity of bacteria, DNA was extracted from the bauxite residue samples and 16S rDNA clone library was constructed. The 16S rDNA clones of this study showed affiliation to three major phyla predominant being betaproteobacteria (41.1 %) followed by gammaproteobacteria (37.5 %) and bacteroidetes (21.4 %). We are reporting for the first time about the bacterial diversity of this unique and extreme environment.     

Microbial diversity in Los Azufres geothermal field (Michoacán,Mexico) and isolation of representative sulfate and sulfur reducers

Los Azufres spa consists of a hydrothermal spring system in the Mexican Volcanic Axis. Five samples (two microbial mats, two mud pools and one cenote water), characterized by high acidity (pH between 1 and 3) and temperatures varying from 27 to 87 °C, were investigated for their microbial diversity by Terminal-Restriction Fragment Length Polymorphism (T-RFLP) and 16S rRNA gene library analyses. These data are the first to describe microbial diversity from Los Azufres geothermal belt. The data obtained from both approaches suggested a low bacterial diversity in all five samples. Despite their proximity, the sampling points differed by their physico-chemical conditions (mainly temperature and matrix type) and thus exhibited different dominant bacterial populations: anoxygenic phototrophs related to the genus Rhodobacter in the biomats, colorless sulfur oxidizers Acidithiobacillus sp. in the warm mud and water samples, and Lyzobacter sp.-related populations in the hot mud sample (87 °C). Molecular data also allowed the detection of sulfate and sulfur reducers related to Thermodesulfobium and Desulfurella genera. Several strains affiliated to both genera were enriched or isolated from the mesophilic mud sample. A feature common to all samples was the dominance of bacteria involved in sulfur and iron biogeochemical cycles (Rhodobacter, Acidithiobacillus, Thiomonas, Desulfurella and Thermodesulfobium genera).     

Diversity and Bioprospective Potential (Cold-Active Enzymes) of Cultivable Marine Bacteria from the Subarctic Glacial Fjord, Kongsfjorden

The diversity and abundance of culturable bacteria in Kongsfjorden water (15 stations) and sediments (12 stations) were studied. Viable numbers ranged between 10⁵–10⁶ CFU l^?1 in water and 10²–10⁴ CFU g^?1 in the sediments. A total of 291 and 43 bacterial isolates were retrieved from the water (KJF) and sediments (FS), respectively. Based on 16S rRNA gene sequence similarities, the KJF and FS isolates were grouped into 49 and 23 phylotypes, respectively. The KJF and FS phylotypes represented three phyla namely, Actinobacteria, Bacteroidetes, and Proteobacteria. At the genus level, Flavobacterium and Shewanella and at the species level, Pseudoaltermonas arctica and Colwellia psychrerythraea were dominant in the water and sediments, respectively. Most phylotypes were psychrotolerant with upper growth temperature limit of 25–37 °C and tolerated 0.3–2.5 M NaCl and pH values of 5.0–11.0. Majority of the phylotypes produced one or more of the extracellular hydrolytic enzymes amylase, lipase, caseinase, urease, gelatinase, and DNase at 4 and 18 °C, while none were chitinolytic. Few of the FS phylotypes exhibited extracellular activity only at 4 or 18 °C. Nine FS and 21 KJF isolates were pigmented. The predominant cellular fatty acids were unsaturated, branched, and modified fatty acids, which are unique to cold-adapted bacteria.