Gene organization and primary structure of a ribosomal RNA operon from Escherichia coli

Seasonal Variation on Microbial Community and Methane Production during Anaerobic Digestion of Cattle Manure in Brazil

Anaerobic digestion is an alternative method for the treatment of animal manure and wastewater. The anaerobic bioconversion of biomass requires a multi-step biological process, including microorganisms with distinct roles. The diversity and composition of microbial structure in pilot-scale anaerobic digestion operating at ambient temperature in Brazil were studied. Influence of the seasonal and temporal patterns on bacterial and archaeal communities were assessed by studying the variations in density, dynamic and diversity and structure. The average daily biogas produced in the summer and winter months was 18.7 and 16 L day(-1), respectively, and there was no difference in the average methane yield. Quantitative PCR analysis revealed that no differences in abundances and dynamics were found for bacterial communities and the total number of Archaea in different seasons. Analysis of bacterial clone libraries revealed a predominance of Firmicutes (54.5 %/summer and 46.7 %/winter) and Bacteroidetes (31.4 %/summer and 44.4 %/winter). Within the Archaea, the phylum Euryarchaeota was predominant in both digesters. Phylogenetic distribution showed changes in percentage between the phyla identified, but no alterations were recorded in the quality and amount of produced methane or community dynamics. The results may suggest that redundancy of microbial groups may have occurred, pointing to a more complex microbial community in the ecosystem related to this ambient temperature system.

Exploring the Bacterial Diversity of Belgian Steak Tartare Using Metagenetics and Quantitative Real-Time PCR Analysis

Steak tartare is a popular meat dish in Belgium. It is prepared with raw minced beef and is eaten with sauce, vegetables, and spices. Because it contains raw meat, steak tartare is highly prone to bacterial spoilage. The objective of this study was to explore the diversity of bacterial flora in steak tartare in Belgium according to the source and to determine which bacteria are able to grow during shelf life. A total of 58 samples from butchers' shops, restaurants, sandwich shops, and supermarkets were collected. These samples were analyzed using 16S rDNA metagenetics, a classical microbiological technique, and quantitative real-time PCR (qPCR) targeting the Lactobacillus genus. Samples were analyzed at the beginning and at the end of their shelf life, except for those from restaurants and sandwich shops, which were analyzed only on the purchase date. Metagenetic analysis identified up to 180 bacterial species and 90 genera in some samples. But only seven bacterial species were predominant in the samples, depending on the source: Brochothrix thermosphacta, Lactobacillus algidus, Lactococcus piscium, Leuconostoc gelidum, Photobacterium kishitani, Pseudomonas spp., and Xanthomonas oryzae. With this work, an alternative method is proposed to evaluate the total flora in food samples based on the number of reads from metagenetic analysis and the results of qPCR. The degree of underestimation of aerobic plate counts at 30°C estimated with the classical microbiology method was demonstrated in comparison with the proposed culture-independent method. Compared with culture-based methods, metagenetic analysis combined with qPCR targeting Lactobacillus provides valuable information for characterizing the bacterial flora of raw meat.

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 × 10(6) DNA copies g(-1) whereas archaea varied between 5 × 10(5) and 10(6) 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.

Biopreservative methods to control the growth of foodborne pathogens on fresh-cut lettuce

Fruits and vegetables can become contaminated by foodborne pathogens such as Escherichia coli O157:H7, Salmonella and Listeria monocytogenes, and it has been demonstrated that current industrial sanitizing treatments do not eliminate the pathogens when present. Chemical control is widely used, but biological control appears to be a better solution, mainly using the native microbiota present on fresh produce. The first objective of this study was to isolate native microbiota from whole and fresh-cut produce and to determine whether these bacteria were antagonistic toward foodborne pathogens. A total of 112 putative antagonist isolates were screened for their ability to inhibit the growth of Salmonella enterica on lettuce disks. Five different genera reduced S. enterica growth more than 1-log unit at 20°C at the end of 3 days. When tested against L. monocytogenes 230/3, only Pseudomonas sp. strain M309 (M309) was able to reduce pathogen counts by more than 1-log unit. Therefore, M309 strain was selected to be tested on lettuce disks at 10°C against S. enterica, E. coli O157:H7 and L. monocytogenes. M309 strain was only able to reduce S. enterica and E. coli O157:H7 populations. The second objective was to test different biopreservative methods including M309 strain, Pseudomonas graminis CPA-7 (CPA-7), bacteriophages (Listex P100 and Salmonelex) and nisin at conditions simulating commercial applications against Salmonella and L. monocytogenes on fresh-cut lettuce. The addition of the biopreservative agents did not result in a significant reduction of Salmonella population. However, CPA-7 strain together with nisin reduced L. monocytogenes numbers after 6 days of storage at 10°C. The cocktail of Salmonella and L. monocytogenes was not markedly inactivated by their respective bacteriophage solutions. This study highlighted the potential of biocontrol, but the combination with other technologies may be required to improve their application on fresh-cut lettuce.

Short communication: Typing and tracking Bacillaceae in raw milk and milk powder using pyroprinting

Contamination of fluid and processed milk products with endospore-forming bacteria, such as Bacillaceae, affect milk quality and longevity. Contaminants come from a variety of sources, including the dairy farm environment, transportation equipment, or milk processing machinery. Tracking the origin of bacterial contamination to allow specifically targeted remediation efforts depends on a reliable strain-typing method that is reproducible, fast, easy to use, and amenable to computerized analysis. Our objective was to adapt a recently developed genotype-based Escherichia coli strain-typing method, called pyroprinting, for use in a microbial source-tracking study to follow endospore-forming bacillus bacteria from raw milk to powdered milk. A collection of endospores was isolated from both raw milk and its finished powder, and, after germination, the vegetative cells were subject to the pyroprinting protocol. Briefly, a ribosomal DNA intergenic transcribed spacer present in multiple copies in Bacillaceae genomes was amplified by the PCR. This multicopy locus generated a mixed PCR product that was subsequently subject to pyrosequencing, a quantitative real-time sequencing method. Through a series of enzymatic reactions, each nucleotide incorporation event produces a photon of light that is quantified at each nucleotide dispensation. The pattern of light peaks generated from this mixed template reaction is called a pyroprint. Isolates with pyroprints that match with a Pearson correlation of 0.99 or greater are considered to be in the same group. The pyroprint also contains some sequence data useful for presumptive species-level identification. This method identified groups with isolates from raw milk only, from powdered milk only, or from both sources. This study confirms pyroprinting as a rapid, reproducible, automatically digitized tool that can be used to distinguish bacterial strains into taxonomically relevant groups and, thus, indicate probable origins of bacterial contamination in powdered milk.

Bacterial clade with the ribosomal RNA operon on a small plasmid rather than the chromosome

rRNA is essential for life because of its functional importance in protein synthesis. The rRNA (rrn) operon encoding 16S, 23S, and 5S rRNAs is located on the "main" chromosome in all bacteria documented to date and is frequently used as a marker of chromosomes. Here, our genome analysis of a plant-associated alphaproteobacterium, Aureimonas sp. AU20, indicates that this strain has its sole rrn operon on a small (9.4 kb), high-copy-number replicon. We designated this unusual replicon carrying the rrn operon on the background of an rrn-lacking chromosome (RLC) as the rrn-plasmid. Four of 12 strains close to AU20 also had this RLC/rrn-plasmid organization. Phylogenetic analysis showed that those strains having the RLC/rrn-plasmid organization represented one clade within the genus Aureimonas. Our finding introduces a previously unaddressed viewpoint into studies of genetics, genomics, and evolution in microbiology and biology in general.

Variovorax gossypii sp. nov., isolated from Gossypium hirsutum

A beige-pigmented bacterial strain (JM-310T), isolated from the healthy internal root tissue of 4-week-old cotton (Gossypium hirsutum, cultivar 'DES-119') in Tallassee (Macon county), Alabama, USA, was studied taxonomically. The isolate produced small rod-shaped cells, which showed a Gram-negative staining behaviour. A comparison of the 16S rRNA gene sequence of the isolate revealed 99.2, 98.8, 98.7, 98.7, 98.1 and 97.6 % similarity to the 16S rRNA gene sequences of the type strains of Variovorax paradoxus, Variovorax boronicumulans, Variovorax ginsengisoli, Variovorax soli, Variovorax defluvii and Variovorax dokdonensis, respectively. In phylogenetic trees based on 16S rRNA gene sequences, strain JM-301T was placed within the monophyletic cluster of Variovorax species. The fatty acid profile of strain JM-310T consisted mainly of the major fatty acids C16 : 0, C10 : 0 3-OH and summed feature 4 (iso-C15 : 0 2-OH/C16 : 1ω7c/t). The quinone system of strain JM-310T contained predominantly ubiquinone Q-8 and lesser amounts of Q-7 and Q-9. The major polyamine was putrescine and the diagnostic polyamine 2-hydroxyputrescine was detected as well. The polar lipid profile consisted of the major lipids phosphatidylethanolamine, phosphatidylglycerol, diphospatidylglycerol and several unidentified lipids. DNA-DNA hybridization experiments with V. paradoxus LMG 1797T, V. boronicumulans 1.22T, V. soli KACC 11579T and V. ginsengisoli 3165T gave levels of relatedness of < 70 %. These DNA-DNA hybridization results in addition to differential biochemical properties indicate clearly that strain JM-310T is a member of a novel species, for which the name Variovorax gossypii sp. nov. is proposed. The type strain is JM-310T ( = LMG 28869T = CIP 110912T = CCM 8614T).

Novosphingobium gossypii sp. nov., isolated from Gossypium hirsutum

A Gram-stain-negative, rod-shaped, non-spore-forming bacterium (strain JM-1396T) producing a yellow pigment, was isolated from the healthy internal stem tissue of post-harvest cotton (Gossypium hirsutum, cultivar ‘DES-119’) grown at the Plant Breeding Unit at the E. V. Smith Research Center in Tallassee (Macon county), AL, USA. 16S rRNA gene sequence analysis of strain JM-1396T showed high sequence similarity values to the type strains of Novosphingobium mathurense, Novosphingobium panipatense (both 98.6 %) and Novosphingobium barchaimii (98.5 %); sequence similarities to all other type strains of species of the genus Novosphingobium were below 98.3 %. DNA–DNA pairing experiments of the DNA of strain JM-1396T and N. mathurense SM117T, N. panipatense SM16T and N. barchaimii DSM 25411T showed low relatedness values of 8 % (reciprocal 7 %), 24 % (reciprocal 26 %) and 19 % (reciprocal 25 %), respectively. Ubiquinone Q-10 was detected as the dominant quinone; the fatty acids C18 : 1ω7c (71.0 %) and the typical 2-hydroxy fatty acid, C14 : 0 2-OH (11.7 %), were detected as typical components. The polar lipid profile contained the diagnostic lipids diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid and phosphatidylcholine. The polyamine pattern contained the major compound spermidine and only minor amounts of other polyamines. All these data revealed that strain JM-1396T represents a novel species of the genus Novosphingobium. For this reason we propose the name Novosphingobium gossypii sp. nov. with the type strain JM-1396T ( = LMG 28605T = CCM 8569T = CIP 110884T).

Bacillus gossypii sp. nov., isolated from the stem of Gossypium hirsutum

A Gram-stain-positive, facultatively anaerobic, endospore-forming organism, isolated from the stem of Gossypium hirsutum, was studied to determine its taxonomic position. On the basis of 16S rRNA gene sequence similarity comparisons, strain JM-267T was grouped in the genus Bacillus, related most closely to the type strains of Bacillus simplex and Bacillus huizhouensis (both 97.8%), Bacillus muralis (97.7%), Bacillus butanolivorans and Bacillus psychrosaccharolyticus (both 97.3%). 16S rRNA gene sequence similarity to the sequences of the type strains of other Bacillus species was < 97.0%. The fatty acid profile supported the grouping of the strain to the genus Bacillus. As major fatty acids, anteiso-C15:0, iso-C15:0, iso-C14:0 and iso-C16:0 were detected. The polar lipid profile contained the major components diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The major quinone was menaquinone 7 (MK-7). DNA-DNA hybridizations with B. simplex DSM 1321T, B. huizhouensis GSS03T, B. muralis LMG 20238T, B. butanolivorans LMG 23974T and B. psychrosaccharolyticus DSM 6T resulted in values clearly below 70%. In addition, physiological and biochemical test results allowed the clear phenotypic differentiation of strain JM-267T from the most closely related species. Hence, strain JM-267T is considered to represent a novel species of the genus Bacillus, for which the name Bacillus gossypii sp. nov. is proposed. The type strain is JM-267T ( = DSM 100034T = LMG 28742T).

Insights into transcription termination of Hfq-binding sRNAs of Escherichia coli and characterization of readthrough products

The genes encoding Hfq-dependent sRNAs possess a typical Rho-independent transcription terminator. Here, we have studied the molecular events occurring at Rho-independent terminators of sRNA genes, focusing on two well-characterized Hfq-binding sRNAs, SgrS and RyhB. We constructed several hybrid genes in which the DNA sequence corresponding to a strong Rho-independent terminator was placed just downstream from the Rho-independent terminators of sRNA genes. By using this system, we demonstrate that transcripts frequently read through the Rho-independent terminators of sgrS and ryhB in normally growing cells. We show that Hfq does not affect the transcriptional readthrough event itself. We also find that the readthrough products no longer bind to Hfq in vivo. We have developed a competition assay based on a biotin-streptavidin system to analyze the interaction of Hfq and a particular RNA molecule in vitro. By using this method, we verify that the 3'-extended form of SgrS does not bind to Hfq in vitro. Finally, we demonstrate that transcription termination is significantly enhanced under stress conditions where transcription initiation of sRNA genes on the chromosome is induced. We conclude that the production of sRNAs is regulated not only at the step of transcription initiation but also at the step of transcription termination. The mechanism by which transcription termination is enhanced under stress conditions remains to be understood.

Distribution of iron- and sulfate-reducing bacteria across a coastal acid sulfate soil (CASS) environment: implications for passive bioremediation by tidal inundation

Coastal acid sulfate soils (CASS) constitute a serious and global environmental problem. Oxidation of iron sulfide minerals exposed to air generates sulfuric acid with consequently negative impacts on coastal and estuarine ecosystems. Tidal inundation represents one current treatment strategy for CASS, with the aim of neutralizing acidity by triggering microbial iron- and sulfate-reduction and inducing the precipitation of iron-sulfides. Although well-known functional guilds of bacteria drive these processes, their distributions within CASS environments, as well as their relationships to tidal cycling and the availability of nutrients and electron acceptors, are poorly understood. These factors will determine the long-term efficacy of "passive" CASS remediation strategies. Here we studied microbial community structure and functional guild distribution in sediment cores obtained from 10 depths ranging from 0 to 20 cm in three sites located in the supra-, inter- and sub-tidal segments, respectively, of a CASS-affected salt marsh (East Trinity, Cairns, Australia). Whole community 16S rRNA gene diversity within each site was assessed by 454 pyrotag sequencing and bioinformatic analyses in the context of local hydrological, geochemical, and lithological factors. The results illustrate spatial overlap, or close association, of iron-, and sulfate-reducing bacteria (SRB) in an environment rich in organic matter and controlled by parameters such as acidity, redox potential, degree of water saturation, and mineralization. The observed spatial distribution implies the need for empirical understanding of the timing, relative to tidal cycling, of various terminal electron-accepting processes that control acid generation and biogeochemical iron and sulfur cycling.

Elizabethkingia endophytica sp. nov., isolated from Zea mays and emended description of Elizabethkingia anophelis Kämpfer et al. 2011

A slightly yellow bacterial strain (JM-87T), isolated from the stem of healthy 10 day-old sweet corn (Zea mays), was studied for its taxonomic allocation. The isolate revealed Gram-stain-negative, rod-shaped cells. A comparison of the 16S rRNA gene sequence of the isolate showed 99.1, 97.8, and 97.4 % similarity to the 16S rRNA gene sequences of the type strains of Elizabethkingia anophelis, Elizabethkingia meningoseptica and Elizabethkingia miricola, respectively. The fatty acid profile of strain JM-87T consisted mainly of the major fatty acids C15:0 iso, C17:0 iso 3-OH, and C15:0 iso 2-OH/C16:1ω7c/t. The quinone system of strain JM-87T contained, exclusively, menaquinone MK-6. The major polyamine was sym-homospermidine. The polar lipid profile consisted of the major lipid phosphatidylethanolamine plus several unidentified aminolipids and other unidentified lipids. DNA–DNA hybridization experiments with E. meningoseptica CCUG 214T ( = ATCC 13253T), E. miricola KCTC 12492T ( = GTC 862T) and E. anophelis R26T resulted in relatedness values of 17 % (reciprocal 16 %), 30 % (reciprocal 19 %), and 51 % (reciprocal 54 %), respectively. These DNA–DNA hybridization results, in addition to some differentiating biochemical properties, clearly indicate that strain JM-87T is a representative of a novel species, for which the name Elizabethkingia endophytica sp. nov. is proposed. The type strain is JM-87T ( = CIP 110885T = LMG 28604T = CCM 8570T).

Mesonia hippocampi sp. nov., isolated from the brood pouch of a diseased Barbour's Seahorse (Hippocampus barbouri)

An orange-pigmented, Gram-staining-negative, rod-shaped bacterium, designated 96_Hippo_TS_3/13T was isolated from the brood pouch of a diseased seahorse male of the species Hippocampus barbouri from the animal facility of the University of Giessen, Germany. Phylogenetic analyses based on the nearly full-length 16S rRNA gene sequence placed strain 96_Hippo_TS_3/13T into the monophyletic cluster of the genus Mesonia within the family Flavobacteriaceae. However, the strain shared only 92.2–93.8 % sequence similarity to type strains of species of the genus Mesonia, with highest sequence similarity to the type strain of Mesonia aquimarina. Cellular fatty acid analysis showed a Mesonia-typical fatty acid profile including several branched and hydroxyl fatty acids with highest amounts of iso-C15 : 0 (40.9 %) followed by iso-C17 : 0 3-OH (14.8 %). In the polyamine pattern, sym-homospermidine was predominant. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The quinone system contained exclusively menaquinone MK-6. The only identified compound in the polar lipid profile was phosphatidylethanolamine present in major amounts. Additionally, major amounts of an unidentified aminolipid and two unidentified lipids not containing a phosphate group, an amino group or a sugar residue were detected. The genomic G+C content of strain 96_Hippo_TS_3/13T was 30 mol%. Based on genotypic, chemotaxonomic and physiological characterizations we propose a novel species of the genus Mesonia, Mesonia hippocampi sp. nov., with strain 96_Hippo_TS_3/13T ( = CIP 110839T =  LMG 28572T = CCM 8557T) as the type strain. An emended description of the genus Mesonia is also provided.

Effects of Xylo-Oligosaccharides on Broiler Chicken Performance and Microbiota

In broiler chickens, feed additives, including prebiotics, are widely used to improve gut health and to stimulate performance. Xylo-oligosaccharides (XOS) are hydrolytic degradation products of arabinoxylans that can be fermented by the gut microbiota. In the current study, we aimed to analyze the prebiotic properties of XOS when added to the broiler diet. Administration of XOS to chickens, in addition to a wheat-rye-based diet, significantly improved the feed conversion ratio. XOS significantly increased villus length in the ileum. It also significantly increased numbers of lactobacilli in the colon and Clostridium cluster XIVa in the ceca. Moreover, the number of gene copies encoding the key bacterial enzyme for butyrate production, butyryl-coenzyme A (butyryl-CoA):acetate CoA transferase, was significantly increased in the ceca of chickens administered XOS. In this group of chickens, at the species level, Lactobacillus crispatus and Anaerostipes butyraticus were significantly increased in abundance in the colon and cecum, respectively. In vitro fermentation of XOS revealed cross-feeding between L. crispatus and A. butyraticus. Lactate, produced by L. crispatus during XOS fermentation, was utilized by the butyrate-producing Anaerostipes species. These data show the beneficial effects of XOS on broiler performance when added to the feed, which potentially can be explained by stimulation of butyrate-producing bacteria through cross-feeding of lactate and subsequent effects of butyrate on gastrointestinal function.

Quality Control of Widely Used Therapeutic Recombinant Proteins by a Novel Real-Time PCR Approach

Background:

Existence of bacterial host-cell DNA contamination in biopharmaceutical products is a potential risk factor for patients receiving these drugs. Hence, the quantity of contamination must be controlled under the regulatory standards. Although different methods such as hybridization assays have been employed to determine DNA impurities, these methods are labor intensive and rather expensive. In this study, a rapid real-time PCR test was served as a method of choice to quantify the E. coli host- cell DNA contamination in widely used recombinant streptokinase (rSK), and alpha interferon (IFN-α) preparations.

Methods:

A specific primer pair was designed to amplify a sequence inside the E. coli 16S rRNA gene. Serial dilutions of DNA extracted from E. coli host cells, along with DNA extracted from Active Pharmaceutical Ingredients of rSK, and IFN-α samples were subjected to an optimized real-time PCR assay based on SYBR Green chemistry.

Results:

The test enabled us to detect a small quantity of genomic DNA contamination as low as 0.0002 pg in recombinant protein-based drugs. For the first time, this study showed that DNA contamination in rSK and IFN-α preparation manufactured in Pasteur Institute of Iran is much lower than the safety limit suggested by the US FDA.

Conclusion:

Real-time PCR is a reliable test for rapid detection of host-cell DNA contamination, which is a major impurity of therapeutic recombinant proteins to keep manufacturers’ minds on refining drugs, and provides consumers with safer biopharmaceuticals.

Thermophilic and cellulolytic consortium isolated from composting plants improves anaerobic digestion of cellulosic biomass: Toward a microbial resource management approach

A cellulolytic consortium was isolated from a composting plant in order to boost the initial hydrolysis step encountered in anaerobic digestion. Improvement of the cellulose degradation, as well as biogas production, was observed for the cultures inoculated with the exogenous consortium. Metagenomics analyses pointed out a weak richness (related to the number of OTUs) of the exogenous consortium induced by the selective pressure (cellulose as sole carbon source) met during the initial isolation steps. Main microbial strains determined were strictly anaerobic and belong to the Clostridia class. During cellulose anaerobic degradation, pH drop induced a strong modification of the microbial population. Despite the fact that richness and evenness were very weak, the exogenous consortium was able to adapt and to maintain the cellulolytic degradation potential. This important result point out the fact that simplified microbial communities could be used in order to increase the robustness of mixed cultures involved in environmental biotechnology.

Proposal of Novosphingobium rhizosphaerae sp. nov., isolated from the rhizosphere

A yellow, Gram-stain-negative, rod-shaped, non-spore-forming bacterium (strain JM-1T) was isolated from the rhizosphere of a field-grown Zea mays plant in Auburn, AL, USA. 16S rRNA gene sequence analysis of strain JM-1T showed high sequence similarity to the type strains of Novosphingobium capsulatum (98.9 %), Novosphingobium aromaticivorans (97.4 %), Novosphingobium subterraneum (97.3 %) and Novosphingobium taihuense (97.1 %); sequence similarities to all other type strains of species of the genus Novosphingobium were below 97.0 %. DNA–DNA hybridizations of strain JM-1T and N. capsulatum DSM 30196T, N. aromaticivorans SMCC F199T and N. subterraneum SMCC B0478T showed low similarity values of 33 % (reciprocal: 21 %), 14 % (reciprocal 16 %) and 36 % (reciprocal 38 %), respectively. Ubiquinone Q-10 was detected as the major respiratory quinone. The predominant fatty acid was C18 : 1ω7c (71.0 %) and the typical 2-hydroxy fatty acid C14 : 0 2-OH (11.7 %) was detected. The polar lipid profile contained the diagnostic lipids diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid and phosphatidylcholine. Characterization by 16S rRNA gene sequence analysis, physiological parameters, pigment analysis, and ubiquinone, polar lipid and fatty acid composition revealed that strain JM-1T represents a novel species of the genus Novosphingobium . For this species we propose the name Novosphingobium rhizosphaerae sp. nov. with the type strain JM-1T ( = LMG 28479T = CCM 8547T).

Study on the Characteristics of Biological Phosphorus Removal Sludge in Different Operation Mode of Reactor

The characteristics of the P removal sludge were studied in 3 different operation modes (AO, AOA and A2O mode) of the sequencing batch membrane reactor (SBMBRs). The results showed that the sludge P content was positively correlated with the P removal ability. The relative P content of the saturated P uptake sludge was 30.6%, 36.7% and 42.9%, respectively in the 3 modes. PHB was synthesized in anaerobic activated sludge and the polyp-P granules were decreased. The opposite trend appeared in aerobic condition. The amount of PHB change in anaerobic stage was proportional to the P release capacity. The FISH detection showed that the more proportion of PAOs to the whole cell the more P removal ability in the system.

Approach to analyze the diversity of myxobacteria in soil by semi-nested PCR-denaturing gradient gel electrophoresis (DGGE) based on taxon-specific gene

The genotypic diversity of insoluble macromolecules degraded myxobacteria, provided an opportunity to discover new bacterial resources and find new ecological functions. In this study, we developed a semi-nested-PCR-denaturing gradient gel electrophoresis (DGGE) strategy to determine the presence and genotypic diversity of myxobacteria in soil. After two rounds of PCR with myxobacteria-specific primers, an 194 bp fragment of mglA, a key gene involved in gliding motility, suitable for DGGE was obtained. A large number of bands were observed in DGGE patterns, indicating diverse myxobacteria inhabiting in soils. Furthermore, sequencing and BLAST revealed that most of the bands belonged to the myxobacteria-group, and only three of the twenty-eight bands belonged to other group, i.e., Deinococcus maricopensis. The results verified that myxobacterial strains with discrepant sequence compositions of gene mglA could be discriminated by DGGE with myxobacteria-specific primers. Collectively, the developed semi-nested-PCR-DGGE strategy is a useful tool for studying the diversity of myxobacteria.

Psychrotrophic lactic acid bacteria associated with production batch recalls and sporadic cases of early spoilage in Belgium between 2010 and 2014

Between 2010 and 2014 several spoilage cases in Belgium occurring in retail foodstuffs prior to the end of shelf-life have been reported to our laboratory. Overall, seven cases involved strictly psychrotrophic lactic acid bacteria (LAB) contamination in packaged and chilled-stored food products. The products derived either from recalls of entire production batches or as specimens of sporadic spoilage manifestations. Some of these samples were returned to the manufacturing companies by consumers who observed the alterations after purchasing the products. The products covered a wide range of foodstuffs (i.e. meat, dairy, vegetable, egg products and composite food) and denoted different spoilage defects. However, the microbiota determined by means of 16S rRNA gene high-throughput sequencing analysis underpin few LAB genera (i.e. Leuconostoc, Lactobacillus, Weissella and Lactococcus), which are frequently encountered nowadays as specific spoilage organisms (SSO) albeit overlooked by mesophilic enumeration methods due to their strictly psychrotrophic character. The present study confirms the spreading of psychrotrophic LAB in Belgian food processing environments leading to unexpected spoilage, corroborating their spoilage dynamics and prevalence in all kinds of packaged and refrigerated foodstuffs in Northern Europe.

Microbiota characterization of a Belgian protected designation of origin cheese, Herve cheese, using metagenomic analysis

Herve cheese is a Belgian soft cheese with a washed rind, and is made from raw or pasteurized milk. The specific microbiota of this cheese has never previously been fully explored and the use of raw or pasteurized milk in addition to starters is assumed to affect the microbiota of the rind and the heart. The aim of the study was to analyze the bacterial microbiota of Herve cheese using classical microbiology and a metagenomic approach based on 16S ribosomal DNA pyrosequencing. Using classical microbiology, the total counts of bacteria were comparable for the 11 samples of tested raw and pasteurized milk cheeses, reaching almost 8 log cfu/g. Using the metagenomic approach, 207 different phylotypes were identified. The rind of both the raw and pasteurized milk cheeses was found to be highly diversified. However, 96.3 and 97.9% of the total microbiota of the raw milk and pasteurized cheese rind, respectively, were composed of species present in both types of cheese, such as Corynebacterium casei, Psychrobacter spp., Lactococcus lactis ssp. cremoris, Staphylococcus equorum, Vagococcus salmoninarum, and other species present at levels below 5%. Brevibacterium linens were present at low levels (0.5 and 1.6%, respectively) on the rind of both the raw and the pasteurized milk cheeses, even though this bacterium had been inoculated during the manufacturing process. Interestingly, Psychroflexus casei, also described as giving a red smear to Raclette-type cheese, was identified in small proportions in the composition of the rind of both the raw and pasteurized milk cheeses (0.17 and 0.5%, respectively). In the heart of the cheeses, the common species of bacteria reached more than 99%. The main species identified were Lactococcus lactis ssp. cremoris, Psychrobacter spp., and Staphylococcus equorum ssp. equorum. Interestingly, 93 phylotypes were present only in the raw milk cheeses and 29 only in the pasteurized milk cheeses, showing the high diversity of the microbiota. Corynebacterium casei and Enterococcus faecalis were more prevalent in the raw milk cheeses, whereas Psychrobacter celer was present in the pasteurized milk cheeses. However, this specific microbiota represented a low proportion of the cheese microbiota. This study demonstrated that Herve cheese microbiota is rich and that pasteurized milk cheeses are microbiologically very close to raw milk cheeses, probably due to the similar manufacturing process. The characterization of the microbiota of this particular protected designation of origin cheese was useful in enabling us to gain a better knowledge of the bacteria responsible for the character of this cheese.

Bacterial community structure and activity of sulfate reducing bacteria in a membrane aerated biofilm analyzed by microsensor and molecular techniques

The activities and vertical spatial distribution of sulfate reducing bacteria (SRB) in an oxygen (O2 )-based membrane aerated biofilm (MAB) were investigated using microsensor (O2 and H2 S) measurements and molecular techniques (polymerase chain reaction-denaturing gradient gel electrophoresis [PCR-DGGE] and fluorescence in situ hybridization [FISH]). The O2 concentration profile revealed that O2 penetrated from the bottom (substratum) of the gas permeable membrane, and was gradually consumed within the biofilm until it was completely depleted near the biofilm/bulk liquid interface, indicating oxic and anoxic zone in the MAB. The H2 S concentration profile showed that H2 S production was found in the upper 285 µm of the biofilm, indicating a high activity of SRB in this region. The results from DGGE of the PCR-amplified dissimilatory sulfite reductase subunit B (dsrB) gene and FISH showed an uneven spatial distribution of SRB. The maximum SRB biomass was located in the upper biofilm. The information from the molecular analysis can be supplemented with that from microsensor measurements to better understand the microbial community and activity of SRB in the MAB.

Elucidation of insertion elements carried on plasmids and in vitro construction of shuttle vectors from the toxic cyanobacterium Planktothrix

Several gene clusters that are responsible for toxin synthesis in bloom-forming cyanobacteria have been found to be associated with transposable elements (TEs). In particular, insertion sequence (IS) elements were shown to play a role in the inactivation or recombination of the genes responsible for cyanotoxin synthesis. Plasmids have been considered important vectors of IS element distribution to the host. In this study, we aimed to elucidate the IS elements propagated on the plasmids and the chromosome of the toxic cyanobacterium Planktothrix agardhii NIVA-CYA126/8 by means of high-throughput sequencing. In total, five plasmids (pPA5.5, pPA14, pPA50, pPA79, and pPA115, of 5, 6, 50, 79, and 120 kbp, respectively) were elucidated, and two plasmids (pPA5.5, pPA115) were found to propagate full IS element copies. Large stretches of shared DNA information between plasmids were constituted of TEs. Two plasmids (pPA5.5, pPA14) were used as candidates to engineer shuttle vectors (named pPA5.5SV and pPA14SV, respectively) in vitro by PCR amplification and the subsequent transposition of the Tn5 cat transposon containing the R6Kγ origin of replication of Escherichia coli. While pPA5.5SV was found to be fully segregated, pPA14SV consistently co-occurred with its wild-type plasmid even under the highest selective pressure. Interestingly, the Tn5 cat transposon became transferred by homologous recombination into another plasmid, pPA50. The availability of shuttle vectors is considered to be of relevance in investigating genome plasticity as a consequence of homologous recombination events. Combining the potential of high-throughput sequencing and in vitro production of shuttle vectors makes it simple to produce species-specific shuttle vectors for many cultivable prokaryotes.

Characterization and genetic analyses of a carbazole-degrading gram-positive marine isolate, Janibacter sp. strain OC11

Strain OC11 was isolated from seawater sampled at the coast of Chiba, Japan, in artificial seawater medium with carbazole (CAR) as the sole carbon source. Its 16S ribosomal RNA gene sequence suggested that strain OC11 belongs to the genus Janibacter. The CAR-degradation genes (car genes) of strain OC11 were PCR amplified, using degenerate primers designed based on the car gene sequences of other CAR-degrading bacteria. Complete nucleotide sequences encoding six complete open reading frames were determined, and the first known ferredoxin reductase gene (carAd) was found from a CAR-degrading bacterium isolated from the marine environment. An experiment using a mutant strain suggested that the car genes of strain OC11 are functional in CAR degradation. Southern hybridization indicated that strain OC11 had one car gene cluster in vivo. RT-PCR revealed that transcription of carOC11 constitutes an operon.

Dynamics of different bacterial communities are capable of generating sustainable electricity from microbial fuel cells with organic waste

The relationship between the bacterial communities in anolyte and anode biofilms and the electrochemical properties of microbial fuel cells (MFCs) was investigated when a complex organic waste-decomposing solution was continuously supplied to MFCs as an electron donor. The current density increased gradually and was maintained at approximately 100 to 150 mA m⁻². Polarization curve analyses revealed that the maximum power density was 7.4 W m⁻³ with an internal resistance of 110 Ω. Bacterial community structures in the organic waste-decomposing solution and MFCs differed from each other. Clonal analyses targeting 16S rRNA genes indicated that bacterial communities in the biofilms on MFCs developed to specific communities dominated by novel Geobacter. Multidimensional scaling analyses based on DGGE profiles revealed that bacterial communities in the organic waste-decomposing solution fluctuated and had no dynamic equilibrium. Bacterial communities on the anolyte in MFCs had a dynamic equilibrium with fluctuations, while those of the biofilm converged to the Geobacter-dominated structure. These bacterial community dynamics of MFCs differed from those of control-MFCs under open circuit conditions. These results suggested that bacterial communities in the anolyte and biofilm have a gentle symbiotic system through electron flow, which resulted in the advance of current density from complex organic waste.

Ten lessons with Carl Woese about RNA and comparative analysis

A few years before I started my graduate studies, Carl Woese was establishing a collaboration with his friend, colleague, and my PhD advisor, Harry Noller. Carl was introducing comparative methods to Harry's lab to determine the secondary structure for the 16S and 23S rRNAs. In addition to an experimental project that had minimal to no success, I was attempting to predict an RNA secondary structure from a single sequence. I determined after a few months that the complexity of RNA folding was much greater than ever anticipated. Ten lessons were learned about the dynamics of RNA folding, the comparative methods used to accurately predict the RNAs secondary structure and the beginnings of its tertiary structure, the use of comparative methods to reveal much more than ever anticipated about RNA structure, other applications beyond RNA structure, and the lessons about the process of scientific discovery.

Construction of a dual fluorescence whole-cell biosensor to detect N-acyl homoserine lactones

Detection of N-acyl homoserine lactones (AHLs) is useful for understanding quorum sensing (QS) behaviors, including biofilm formation, virulence and metabolism. For detecting AHLs and indicating the host cells in situ, we constructed the plasmid pUCGMA2T(1-4) to make a dual fluorescent whole-cell biosensor based on the AhlIR AHL system of Pseudomonas syringae pv. syringae B728a. The plasmid contains three components: constitutively expressed P(npatII::gfp) for indicating host cells, P(ahlI::mcherry) that produces red fluorescence in response to AHL, and the ahlR gene that encodes an AHL regulatory protein. Meanwhile, two copies of T(1-4) (four tandem copies of a transcriptional terminator) were added into the plasmid to reduce background. The results showed that when the plasmid was placed into Escherichia coli, the dual fluorescence whole-cell biosensor was able to respond with red fluorescence within 6 hr to 5 x 10(-8)-1 x 10(-5) mol/L of 3OC6-HSL. Bright green fluorescence indicated the host cells. Furthermore, when the plasmid was transferred to wildtype Pseudomonas PhTA125 (an AHL-producing bacterium), it also showed both green and red fluorescence. This result demonstrates that this plasmid can be used to construct whole-cell indicators that can indicate the AHL response and spatial behaviors of microbes in a microenvironmental niche.

Characterization of inverted repeat sequences and ribosomal RNA genes of chloroplast DNA from Chlorella ellipsoidea

Chloroplast DNA isolated from a green alga Chlorella was shown by agarose gel electrophoresis and electron microscopy to contain a pair of large inverted repeat sequences of ca. 23 kbp. Electron microscopy revealed that the repeats were separated from each other by a small single strand loop of 29.5 kbp and a large single strand region of 98.5 kbp.Digestion with the restriction endonucleases Kpnl, Sstl, and Xhol, and hybridization with (32)P-labelled tobacco rDNAs revealed that the genes for 16S and 23S rRNAs are present in the repeated sequences. From the hybridization pattern, a restriction map around the sequences were constructed, and the rRNA genes were found to be on the 10.8 kbp SstI fragment. This location was supported by electron microscopy (R-loop formation).Unlike Chlamydomonas reinhardii, Chlorella lacks a large intron in its 23S rRNA gene, and the 16S-23S spacer region is considerably long; the organization of rRNA operon is similar to that of higher plants.

Microbial community composition of Tirez lagoon (Spain), a highly sulfated athalassohaline environment

BACKGROUND

The aim was to study the seasonal microbial diversity variations of an athalassohaline environment with a high concentration of sulfates in Tirez lagoon (La Mancha, Spain). Despite the interest in these types of environments there is scarce information about their microbial ecology, especially on their anoxic sediments.

RESULTS

We report the seasonal microbial diversity of the water column and the sediments of a highly sulfated lagoon using both molecular and conventional microbiological methods. Algae and Cyanobacteria were the main photosynthetic primary producers detected in the ecosystem in the rainy season. Also dinoflagelates and filamentous fungi were identified in the brines. The highest phylotype abundance in water and sediments corresponded to members of the bacterial phylum Proteobacteria, mainly of the Gamma- and Alphaproteobacteria classes. Firmicutes and Actinobacteria were isolated and identified in Tirez brines and sediment samples. Halophilic sulfate reducing Deltaproteobacteria were also detected (Desulfohalobium).

CONCLUSIONS

Important differences have been found in the microbial diversity present in the Tirez water column and the sediments between the wet and dry seasons. Also the Tirez lagoon showed a high richness of the bacterial Alpha- and Deltaproteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and for the archaeal Euryarchaeota.

Use of PCR-DGGE Based Molecular Methods to Analyse Microbial Community Diversity and Stability during the Thermophilic Stages of an ATAD Wastewater Sludge Treatment Process as an Aid to Performance Monitoring

PCR and PCR-DGGE techniques have been evaluated to monitor biodiversity indexes within an ATAD (autothermal thermophilic aerobic digestion) system treating domestic sludge for land spread, by examining microbial dynamics in response to elevated temperatures during treatment. The ATAD process utilises a thermophilic population to generate heat and operates at elevated pH due to degradation of sludge solids, thus allowing pasteurisation and stabilisation of the sludge. Genera-specific PCR revealed that Archaea, Eukarya and Fungi decline when the temperature reaches 59°C, while the bacterial lineage constitutes the dominant group at this stage. The bacterial community at the thermophilic stage, its similarity index to the feed material, and the species richness present were evaluated by PCR-DGGE. Parameters such as choice of molecular target (16S rDNA or rpoB genes), and electrophoresis condition, were optimised to maximise the resolution of the method for ATAD. Dynamic analysis of microbial communities was best observed utilising PCR-DGGE analysis of the V6-V8 region of 16S rDNA, while rpoB gene profiles were less informative. Unique thermophilic communities were shown to quickly adapt to process changes, and shown to be quite stable during the process. Such techniques may be used as a monitoring technique for process health and efficiency.

Elimination of high concentration hydrogen sulfide and biogas purification by chemical-biological process

A chemical-biological process was performed to remove a high concentration of H2S in biogas. The high iron concentration tolerance (20gL(-1)) of Acidithiobacillus ferrooxidans CP9 provided sufficient ferric iron level for stable and efficient H2S elimination. A laboratory-scale apparatus was setup for a 45 d operation to analyze the optimal conditions. The results reveal that the H2S removal efficiency reached 98% for 1500ppm H2S. The optimal ferric iron concentration was kept between 9 and 11gL(-1) with a cell density of 10(8)CFUg(-1) granular activated carbon and a loading of 15gSm(-3)h(-1). In pilot-scale studies for biogas purification, the average inlet H2S concentration was 1645ppm with a removal efficiency of up to 97% for a 311d operation and an inlet loading 40.8gSm(-3)h(-1). When 0.1% glucose was added, the cell density increased twofold under the loading of 65.1gSm(-3)h(-1) with an H2S removal efficiency still above 96%. The analysis results of the distribution of microorganisms in the biological reactor by DGGE show that microorganism populations of 96.7% and 62.7% were identical to the original strain at day 200 and day 311, respectively. These results clearly demonstrate that ferric iron reduction by H2S and ferrous iron oxidation by A. ferrooxidans CP9 are feasible processes for the removal of H2S from biogas.

The effect of heavy metals on microbial community structure of a sulfidogenic consortium in anaerobic semi-continuous stirred tank reactors

The effect of heavy metals on community structure of a heavy metal tolerant sulfidogenic consortium was evaluated by using a combination of denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene and dissimilatory sulfite reductase (dsrB) gene fragments, 16S rRNA gene cloning analysis and fluorescence in situ hybridization (FISH). For this purpose, four anaerobic semi-continuous stirred tank reactors (referred as R1-R4) were run in parallel for 12 weeks at heavy metal loading rates of 1.5, 3, 4.5 and 7.5 mg l(-1) d(-1) each of Cu(2+), Ni(2+), Zn(2+), and Cr(6+), respectively. The abundance ratio of Desulfovibrio vulgaris detected by FISH to total cell counts was consistent with the obtained results of cloning and DGGE. This indicated that D. vulgaris was dominant in all analyzed samples and played a key role in heavy metal removal in R1, R2, and R3. In contrast, after 4 weeks of operation of R4, a distinct biomass loss was observed and no positive hybridized cells were detected by specific probes for the domain Bacteria, sulfate-reducing bacteria and D. vulgris. High removal efficiencies of heavy metals were achieved in R1, R2 and R3 after 12 weeks, whereas the precipitation of heavy metals in R4 was significantly decreased after 4 weeks and almost not observed after 6 weeks of operation. In addition, the anaerobic bacteria, such as Pertrimonas sulfuriphila, Clostridium sp., Citrobacter amalonaticus, and Klebsiella sp., identified from DGGE bands and clone library were hypothesized as heavy metal resistant bacteria at a loading rate of 1.5 mg l(-1) d(-1) of Cu(2+), Ni(2+), Zn(2+), and Cr(6+.)

Bacterial composition of soils of the Lake Wellman area, Darwin Mountains, Antarctica

The aim of this study was to examine the bacterial composition of high latitude soils from the Darwin-Hatherton glacier region of Antarctica. Four soil pits on each of four glacial drift sheets were sampled for chemical and microbial analyses. The four drifts-Hatherton, Britannia, Danum, and Isca-ranged, respectively, from early Holocene (10 ky) to mid-Quaternary (ca 900 ky). Numbers of culturable bacteria were low, with highest levels detected in soils from the younger Hatherton drift. DNA was extracted and 16S rRNA gene clone libraries prepared from samples below the desert pavement for each of the four drift sheets. Between 31 and 262 clones were analysed from each of the Hatherton, Britannia, and Danum drifts. Bacterial sequences were dominated by members of the phyla Deinococcus-Thermus, Actinobacteria, and Bacteroidetes. Culturable bacteria, including some that clustered with soil clones (e.g., members of the genera Arthrobacter, Adhaeribacter, and Pontibacter), belonged to Actinobacteria and Bacteroidetes. The isolated bacteria are ideal model organisms for genomic and phenotypic investigations of those attributes that allow bacteria to survive and/or grow in Antarctic soils because they have close relatives that are not tolerant of these conditions.

Long-term starvation and subsequent recovery of nitrifiers in aerated submerged fixed-bed biofilm reactors

The effectiveness of three operational strategies for maintaining nitrifiers in bench-scale, aerated, submerged fixed-bed biofilm reactors (SFBBRs) during long-term starvation at 20 degrees C were evaluated. The operational strategies were characterized by the resulting oxidation-reduction potential (ORP) in the SFBBRs. The activity rates of the nitrifiers were measured and the activity decay was expressed by half-life times. It was found that anoxic and alternating anoxic/aerobic conditions were the best ways to preserve ammonia-oxidizing bacteria (AOB) during long starvation periods and resulted in half-life times of up to 34 and 28 days, respectively. Extended anaerobic conditions caused the half-life for AOB to decrease to 21 days. In comparison, the activity decay of nitrite-oxidizing bacteria (NOB) tended to be slightly faster. The activity of AOB biofilms that were kept for 97 days under anoxic conditions could be completely recovered in less than one week, while over 4 weeks was needed for AOB kept under anaerobic conditions. NOB were more sensitive to starvation and required longer recovery periods than AOB. For complete recovery, NOB needed approximately 7 weeks, regardless of the starvation conditions applied. Using the fluorescence in situ hybridization (FISH) technique, Nitrospira was detected as the dominant NOB genus. Among the AOB, the terminal restriction fragment length polymorphism (TRFLP) technique showed that during starvation and recovery periods, the relative frequency of species shifted to Nitrosomonas europaea/eutropha, regardless of the starvation condition. The consequences of these findings for the operation of SFBBRs under low-load and starvation conditions are discussed.

Monitoring the performance and microbial diversity dynamics of a full scale anaerobic wastewater treatment plant treating sugar factory wastewater

Microbial community dynamics and the overall system performance of a real scale anaerobic wastewater treatment plant treating sugar industry wastewater were studied. Dominant bacterial and archaeal communities were monitored by 16S rRNA gene targeted PCR amplification and single strand conformation polymorphism analysis (SSCP). Chemical oxygen demand (COD) removal efficiency and operational parameters such as pH, temperature, alkalinity, volatile fatty acids in the methanogenic reactor remained within respective optimal ranges. All bacterial profiles in acidogenic and methanogenic reactors and in the lamella separator presented complex patterns; and the bacterial diversity, measured as SSCP profile richness and structure, was quite chaotic. In contrast to the results obtained for the bacterial community, archaeal 16S rDNA patterns in acidogenic and methanogenic reactors and the lamella separator remained relatively stable over the whole operation period of the anaerobic wastewater treatment plant. Evaluation of microbial community dynamics and overall system performance using the Mantel test revealed that there was no correlation between the dynamics of the microbial communities and the abiotic parameters.

Biological sludge reduction during abattoir wastewater treatment process using a sequencing batch aerobic system

Excess sludge disposal during biological treatment of wastewater is subject to numerous constraints, including social, health and regulatory factors. To reduce the amount of excess sludge, coupled processes involving different biological technologies are currently under taken. This work presents a laboratory scale sequencing batch aerobic system included an anaerobic zone for biomass synchronization (SBAAS: sequencing batch aerobic anaerobic system). This system was adopted to reduce sludge production during abattoir wastewater (AW) treatment. The average chemical oxygen demand (COD) removal efficiency of 89% was obtained at a hydraulic retention time (HRT) and a sludge retention time (SRT) of 2 days and 15-20 days, respectively. The comparison of SBAAS performances with a conventional sequencing batch activated sludge system (SBASS) found that the observed biomass production yield (Y(obs)) were in the ranges of 0.26 and 0.7 g suspended solids g(-1) COD removed, respectively. A significant reduction in the excess biomass production of 63% was observed by using the SBAAS. In fact, in the anaerobic zone microorganisms consume the intracellular stocks of energy by endogenous metabolism, which limits biosynthesis and accelerates sludge decay. The single strand conformation polymorphism (SSCP) method was used to study the dynamic and the diversity of bacterial communities. Results showed a significant change in the population structure by including the anaerobic stage in the process, and revealed clearly that the sludge production yield can be correlated with the bacterial communities present in the system.

Repeatedly evolved host-specific ectosymbioses between sulfur-oxidizing bacteria and amphipods living in a cave ecosystem

Ectosymbioses between invertebrates and sulfur-oxidizing bacteria are widespread in sulfidic marine environments and have evolved independently in several invertebrate phyla. The first example from a freshwater habitat, involving Niphargus ictus amphipods and filamentous Thiothrix ectosymbionts, was recently reported from the sulfide-rich Frasassi caves in Italy. Subsequently, two new Niphargus species, N. frasassianus and N. montanarius, were discovered within Frasassi and found to co-occur with N. ictus. Using a variety of microscopic and molecular techniques, we found that all three Frasassi-dwelling Niphargus species harbor Thiothrix ectosymbionts, which belong to three distinct phylogenetic clades (named T1, T2, and T3). T1 and T3 Thiothrix dominate the N. frasassianus ectosymbiont community, whereas T2 and T3 are prevalent on N. ictus and N. montanarius. Relative distribution patterns of the three ectosymbionts are host species-specific and consistent over different sampling locations and collection years. Free-living counterparts of T1-T3 are rare or absent in Frasassi cave microbial mats, suggesting that ectosymbiont transmission among Niphargus occurs primarily through inter- or intraspecific inoculations. Phylogenetic analyses indicate that the Niphargus-Thiothrix association has evolved independently at least two times. While ectosymbioses with T1 and T2 may have been established within Frasassi, T3 ectosymbionts seem to have been introduced to the cave system by Niphargus.

Effects of remediation on the bacterial community of an acid mine drainage impacted stream

Acid mine drainage (AMD) represents a global threat to water resources, and as such, remediation of AMD-impacted streams is a common practice. During this study, we examined bacterial community structure and environmental conditions in a low-order AMD-impacted stream before, during, and after remediation. Bacterial community structure was examined via polymerase chain reaction amplification of 16S rRNA genes followed by denaturing gradient gel electrophoresis. Also, bacterial abundance and physicochemical data (including metal concentrations) were collected and relationships to bacterial community structure were determined using BIO-ENV analysis. Remediation of the study stream altered environmental conditions, including pH and concentrations of some metals, and consequently, the bacterial community changed. However, remediation did not necessarily restore the stream to conditions found in the unimpacted reference stream; for example, bacterial abundances and concentrations of some elements, such as sulfur, magnesium, and manganese, were different in the remediated stream than in the reference stream. BIO-ENV analysis revealed that changes in pH and iron concentration, associated with remediation, primarily explained temporal alterations in bacterial community structure. Although the sites sampled in the remediated stream were in relatively close proximity to each other, spatial variation in community composition suggests that differences in local environmental conditions may have large impacts on the microbial assemblage.

Bacterioplankton community diversity in a maritime Antarctic lake, determined by culture-dependent and culture-independent techniques

Abstract The biodiversity of the pelagic bacterioplankton community of a maritime Antarctic freshwater lake was examined by cultivation-dependent and cultivation-independent techniques to determine predominant bacterioplankton populations present. The culture-dependent techniques used were direct culture and observation, polymerase chain reaction amplification of 16S rRNA gene fragments, restriction fragment length polymorphism (RFLP) analysis followed by selective sequencing and fatty acid methyl ester analysis. The culture-independent techniques used were 16S ribosomal DNA gene cloning, RFLP analysis and sequencing, in situ hybridisation with group-specific, fluorescently labelled oligonucleotide probes and cloning and sequencing of dominant denaturing gradient gel electrophoresis products. Significant differences occurred between the results obtained with each method. However, sufficient overlap existed between the different methods to identify potentially significant groups. At least six different bacterial divisions including 24 genera were identified using culture-dependent techniques, and eight different bacterial divisions, including 23 genera, were identified using culture-independent techniques. Only five genera, Corynebacterium, Cytophaga, Flavobacterium, Janthinobacterium and Pseudomonas, could be identified using both sets of techniques, which represented four different bacterial divisions. Significantly for Antarctic freshwater lakes, pigment production is found within members of each of these genera. This work illustrates the importance of a comprehensive polyphasic approach in the analysis of lake bacterioplankton, and supports the ecological relevance of results obtained in earlier entirely culture-based studies.