Genomic Characterization of Multidrug-Resistant Escherichia coli BH100 Sub-strains.

The rapid emergence of multidrug-resistant (MDR) bacteria is a global health problem. Mobile genetic elements like conjugative plasmids, transposons, and integrons are the major players in spreading resistance genes in uropathogenic Escherichia coli (UPEC) pathotype. The E. coli BH100 strain was isolated from the urinary tract of a Brazilian woman in 1974. This strain presents two plasmids carrying MDR cassettes, pBH100, and pAp, with conjugative and mobilization properties, respectively. However, its transposable elements have not been characterized. In this study, we attempted to unravel the factors involved in the mobilization of virulence and drug-resistance genes by assessing genomic rearrangements in four BH100 sub-strains (BH100 MG2014, BH100 MG2017, BH100L MG2017, and BH100N MG2017). Therefore, the complete genomes of the BH100 sub-strains were achieved through Next Generation Sequencing and submitted to comparative genomic analyses. Our data shows recombination events between the two plasmids in the sub-strain BH100 MG2017 and between pBH100 and the chromosome in BH100L MG2017. In both cases, IS3 and IS21 elements were detected upstream of Tn21 family transposons associated with MDR genes at the recombined region. These results integrated with Genomic island analysis suggest pBH100 might be involved in the spreading of drug resistance through the formation of resistance islands. Regarding pathogenicity, our results reveal that BH100 strain is closely related to UPEC strains and contains many IS3 and IS21-transposase-enriched genomic islands associated with virulence. This study concludes that those IS elements are vital for the evolution and adaptation of BH100 strain.

Insights into the Genome Sequence of Chromobacterium amazonense Isolated from a Tropical Freshwater Lake.

Members of the genus Chromobacterium have been isolated from geographically diverse ecosystems and exhibit considerable metabolic flexibility, as well as biotechnological and pathogenic properties in some species. This study reports the draft assembly and detailed sequence analysis of Chromobacterium amazonense strain 56AF. The de novo-assembled genome is 4,556,707 bp in size and contains 4294 protein-coding and 95 RNA genes, including 88 tRNA, six rRNA, and one tmRNA operon. A repertoire of genes implicated in virulence, for example, hemolysin, hemolytic enterotoxins, colicin V, lytic proteins, and Nudix hydrolases, is present. The genome also contains a collection of genes of biotechnological interest, including esterases, lipase, auxins, chitinases, phytoene synthase and phytoene desaturase, polyhydroxyalkanoates, violacein, plastocyanin/azurin, and detoxifying compounds. Importantly, unlike other Chromobacterium species, the 56AF genome contains genes for pore-forming toxin alpha-hemolysin, a type IV secretion system, among others. The analysis of the C. amazonense strain 56AF genome reveals the versatility, adaptability, and biotechnological potential of this bacterium. This study provides molecular information that may pave the way for further comparative genomics and functional studies involving Chromobacterium-related isolates and improves our understanding of the global genomic diversity of Chromobacterium species.

Insights into the skin microbiome dynamics of leprosy patients during multi-drug therapy and in healthy individuals from Brazil.

Leprosy is a chronic infectious peripheral neuropathy that is caused by Mycobacterium leprae, and the skin is one of its preferred target sites. However, the effects of this infection on the skin microbiome remain largely unexplored. Here, we characterize and compare the lesional and non-lesional skin microbiomes of leprosy patients and healthy individuals through the deep sequencing of 16 S rRNA genes. Additionally, a subset of patients was monitored throughout the multi-drug therapy to investigate its effect on the leprous skin microbiome. Firmicutes-associated OTUs (primarily Staphylococcus) prevailed in healthy individuals. By contrast, Firmicutes was underrepresented and Proteobacteria was enriched in the patients' skin, although a single dominant taxon has not been observed at a finer taxonomic resolution. These differences can be explained by the significant decrease in Staphylococcus and Streptococcus as well as the enrichment in Brevundimonas. The overrepresentation of Micrococcus in patients is also remarkable. Genus-level compositional profiles revealed no significant intrapersonal difference between lesional and non-lesional sites. Treatment-associated changes indicated a loss of diversity and a shift in the community composition, with stronger impacts on the OTUs that are considered indigenous bacteria. Therefore, the molecular signatures associated with leprosy identified herein might be of importance for early diagnostics.

Novel arsenic-transforming bacteria and the diversity of their arsenic-related genes and enzymes arising from arsenic-polluted freshwater sediment.

Bacteria are essential in arsenic cycling. However, few studies have addressed 16S rRNA and arsenic-related functional gene diversity in long-term arsenic-contaminated tropical sediment. Here, using culture-based, metagenomic and computational approaches, we describe the diversity of bacteria, genes and enzymes involved in AsIII and AsV transformation in freshwater sediment and in anaerobic AsIII- and AsV-enrichment cultures (ECs). The taxonomic profile reveals significant differences among the communities. Arcobacter, Dechloromonas, Sedimentibacter and Clostridium thermopalmarium were exclusively found in ECs, whereas Anaerobacillus was restricted to AsV-EC. Novel taxa that are both AsV-reducers and AsIII-oxidizers were identified: Dechloromonas, Acidovorax facilis, A. delafieldii, Aquabacterium, Shewanella, C. thermopalmarium and Macellibacteroides fermentans. Phylogenic discrepancies were revealed among the aioA, arsC and arrA genes and those of other species, indicating horizontal gene transfer. ArsC and AioA have sets of amino acids that can be used to assess their functional and structural integrity and familial subgroups. The positions required for AsV reduction are conserved, suggesting strong selective pressure for maintaining the functionality of ArsC. Altogether, these findings highlight the role of freshwater sediment bacteria in arsenic mobility, and the untapped diversity of dissimilatory arsenate-reducing and arsenate-resistant bacteria, which might contribute to arsenic toxicity in aquatic environments.

Antibacterial activity of different types of snake venom from the Viperidae family against Staphylococcus aureus / Atividade antibacteriana de diferentes tipos de veneno de serpentes da família Viperidae contra Staphylococcus aureus

Toxins and venoms produced by living organisms have exhibited a variety of biological activities against microorganisms. In this study, we tested seven snake venoms from the family Viperidae for antibacterial activity and the activities of reversal of antibiotic resistance and inhibition of biofilm formation against 22 clinical isolates of Staphylococcus aureus. Bothrops moojeni venom exhibited anti staphylococcal activity with the lowest mean value of minimum inhibitory concentration (MIC). Moreover, reversal of antibiotic resistance was observed for combinations of B. moojeni venom (½ x MIC) and norfloxacin or ampicillin (both ½ x MIC) for 86.4% and 50% of the isolates, respectively. B. moojeni venom alone at ½ MIC inhibited 90% of biofilm formation, whereas in combination with ciprofloxacin, both at ½ MIC, a reduction on the NorA efflux pump activity was observed. The detection of in vitro mutants colonies of S. aureus resistant to B. moojeni venom was low and they did not survive. A phospholipase A2 was purified from the venom of B. moojeni and displayed anti-staphylococcal activity when tested alone or in combination with ciprofloxacin. The results presented here will contribute to the search for new antimicrobial agents against resistant S. aureus.

Toxinas e venenos exibem uma variedade de atividades biológicas contra micro-organismos. Neste estudo, investigou-se a atividade de sete venenos de serpentes, da família Viperidae, sobre o crescimento de Staphylococcus aureus, na reversão fenotípica da resistência a antibióticos e inibição de formação de biofilme contra 22 isolados clínicos de S. aureus. O veneno de Bothrops moojeni apresentou a menor média de concentração inibitória mínima (CIM). Além disso, observou-se reversão da resistência a antibióticos para combinações do veneno de B. moojeni (½ x CIM) e norfloxacina ou ampicilina (ambos ½ x CIM) para 86,4% e 50% dos isolados, respectivamente. O veneno de B. moojeni na concentração de ½ CIM inibiu 90% de formação de biofilme, enquanto ele em combinação com ciprofloxacina, ambos na concentração de ½ CIM, diminuiu a atividade da bomba de efluxo NorA. A detecção in vitro de colônias mutantes de S. aureus resistente ao veneno de B. moojeni foi baixa e eles não sobreviveram. Uma fosfolipase A2 purificada a partir do veneno de B. moojeni exibiu atividade antibacteriana quando testada sozinha ou em combinação com ciprofloxacina. Os dados obtidos poderão contribuir para a pesquisa de novos agentes antimicrobianos contra S. aureus.

Occurrence and characterization of class 1 integrons in Escherichia coli from healthy individuals and those with urinary infection.

PURPOSE: Class 1 integrons are among the main vehicles that facilitate the spread of antibiotic-resistance genes, with serious public health consequences. The aim of this cross-sectional study was to investigate the presence of class 1 integrons and to characterize their variable regions, as well as the antimicrobial resistance profiles and phylogenetic groups of a collection of Escherichia coli isolates recovered from healthy subjects (n=42) and those with urinary infection (n=40). METHODOLOGY: The methods used included PCR, sequencing and antimicrobial susceptibility testing. RESULTS: PCR screening for the integrase gene (intI1) revealed a higher incidence of class 1 integrons in uropathogenic E. coli (65 %, UPEC) than in commensal isolates (11.9 %). Eight of 31 intI1-positive isolates, all of them UPEC, harboured empty integrons. The variable regions of the other 23 contained gene cassettes encoding resistance to ß-lactams (blaOXA-1), aminoglycosides (aadA1 and aadA5), trimethoprim (dfrA1 and dfrA17) and an ORF. To our knowledge this is the first report of an ORF identified as a putative phage tail protein associated with a class 1 integron. The aadA1 and dfrA17-addA5 arrays prevailed in commensal E. coli and UPEC, respectively. UPEC isolates were highly resistant to the antimicrobials tested, in contrast to commensal isolates. The E. coli isolates carrying gene cassettes associated with class 1 integrons were found to be unrelated to any phylogroup or multiresistance. CONCLUSION: Co-resistance to clinically relevant fluoroquinolone and trimethoprim-sulfamethazole in all UPEC isolates is a cause for concern. These results expand the current knowledge of gene cassettes in both commensal and pathogenic E. coli.

Seasonality of freshwater bacterioplankton diversity in two tropical shallow lakes from the Brazilian Atlantic Forest.

Bacteria are highly important for the cycling of organic and inorganic matter in freshwater environments; however, little is known about the diversity of bacterioplankton in tropical systems. Studies on carbon and nutrient cycling in tropical lakes suggest a very different seasonality from that of temperate climates. Here, we used 16S rRNA gene next-generation sequencing (NGS) to investigate seasonal changes in bacterioplankton communities of two tropical lakes, which differed in trophic status and mixing regime. Our findings revealed seasonally and depth-wise highly dynamic bacterioplankton communities. Differences in richness and structure appeared strongly related to the physicochemical characteristics of the water column, especially phosphate, pH and oxygen. Bacterioplankton communities were dominated by common taxonomic groups, such as Synechococcus and Actinobacteria acI, as well as rare and poorly characterized taxa such as 'Candidatus Methylacidiphilum' (Verrucomicrobia). Stratification and oxygen depletion during the rainy season promoted the occurrence of anoxygenic phototrophic and methanotrophic bacteria important for carbon and nutrient cycling. Differences in lake mixing regime were associated with seasonal beta diversity. Our study is the first attempt to use NGS for cataloging the diversity of bacterioplankton communities in Brazilian lakes and thus contributes to the ongoing worldwide endeavor to characterize freshwater lake bacterioplankton signatures.

Metagenomic signatures of a tropical mining-impacted stream reveal complex microbial and metabolic networks.

Bacteria from aquatic ecosystems significantly contribute to biogeochemical cycles, but details of their community structure in tropical mining-impacted environments remain unexplored. In this study, we analyzed a bacterial community from circumneutral-pH tropical stream sediment by 16S rRNA and shotgun deep sequencing. Carrapatos stream sediment, which has been exposed to metal stress due to gold and iron mining (21 [g Fe]/kg), revealed a diverse community, with predominance of Proteobacteria (39.4%), Bacteroidetes (12.2%), and Parcubacteria (11.4%). Among Proteobacteria, the most abundant reads were assigned to neutrophilic iron-oxidizing taxa, such as Gallionella, Sideroxydans, and Mariprofundus, which are involved in Fe cycling and harbor several metal resistance genes. Functional analysis revealed a large number of genes participating in nitrogen and methane metabolic pathways despite the low concentrations of inorganic nitrogen in the Carrapatos stream. Our findings provide important insights into bacterial community interactions in a mining-impacted environment.

Diversity of gene cassettes and the abundance of the class 1 integron-integrase gene in sediment polluted by metals.

The integron-gene cassette system has typically been associated with antibiotic-resistant pathogens. However, the diversity of gene cassettes and the abundance of class 1 integrons outside of the clinical context are not fully explored. Primers targeting the conserved segments of attC recombination sites were used to amplify gene cassettes from the sediment of the Mina stream, which exhibited a higher degree of stress to metal pollution in the dry season than the rainy season. Of the 143 total analyzed sequences, 101 had no matches to proteins in the database, where cassette open reading frames could be identified by homology with database entries. There was a predominance of sequences encoding essential cellular functions. Each season that was sampled yielded a specific pool of gene cassettes. Real-time PCR revealed that 8.5 and 41.6 % of bacterial cells potentially harbored a class 1 integron in the rainy and dry seasons, respectively. In summary, our findings demonstrate that most of the gene cassettes have no ascribable function and, apparently, historically metal-contaminated sediment favors the maintenance of bacteria containing the intI1 gene. Thus, the diversity of gene cassettes is far from being fully explored deserving further attention.

Endophytic Microbiota Associated with the Root Tips and Leaves of Baccharis dracunculifolia

ABSTRACT Although endophytic bacteria impact the health, and ultimately the fitness, of their hosts, our understanding of the diversity of endophytic species remains limited. Here we report on the endophytic microbiota inhabiting the roots, healthy leaves and leaves attacked by a gall-inducing insect of Baccharis dracunculifolia, a species of major economic relevance in South America, using 16S rRNA gene new generation sequencing. Rhodoplanes and Nitrospira were well represented in the communities of roots and leaves; known to be important for nitrogen cycling. The difference in bacterial diversity between healthy and galled leaves was not pronounced. The leaves seem to harbor specialized bacteria with high tolerances to abiotic stresses such as wide variation in temperature, low humidity, shallow and nutrient-poor soils and high solar irradiation. These findings suggest taxon-specific ecological niches in the leaves and roots, which may be the result of different physicochemical characteristics between these structures. This study provides a basis for further investigations and adds significant new information to the current knowledge of the endophytic bacterial composition in B. dracunculifolia.

The effect of human settlement on the abundance and community structure of ammonia oxidizers in tropical stream sediments.

Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are a diverse and functionally important group in the nitrogen cycle. Nevertheless, AOA and AOB communities driving this process remain uncharacterized in tropical freshwater sediment. Here, the effect of human settlement on the AOA and AOB diversity and abundance have been assessed by phylogenetic and quantitative PCR analyses, using archaeal and bacterial amoA and 16S rRNA genes. Overall, each environment contained specific clades of amoA and 16S rRNA genes sequences, suggesting that selective pressures lead to AOA and AOB inhabiting distinct ecological niches. Human settlement activities, as derived from increased metal and mineral nitrogen contents, appear to cause a response among the AOB community, with Nitrosomonas taking advantage over Nitrosospira in impacted environments. We also observed a dominance of AOB over AOA in mining-impacted sediments, suggesting that AOB might be the primary drivers of ammonia oxidation in these sediments. In addition, ammonia concentrations demonstrated to be the driver for the abundance of AOA, with an inversely proportional correlation between them. Our findings also revealed the presence of novel ecotypes of Thaumarchaeota, such as those related to the obligate acidophilic Nitrosotalea devanaterra at ammonia-rich places of circumneutral pH. These data add significant new information regarding AOA and AOB from tropical freshwater sediments, albeit future studies would be required to provide additional insights into the niche differentiation among these microorganisms.

Draft Genome Sequence of Micrococcus sp. Strain MS-AsIII-49, an Arsenate-Reducing Isolate from Tropical Metal-Rich Sediment.

Micrococcus sp. strain MS-AsIII-49, which was isolated from a tropical metal-polluted stream sediment in Brazil, has the ability to reduce AsV to AsIII. Analysis of its draft genome revealed 186 contigs with a total size of 2,440,924 bp encoding several metal resistance genes.

Leprous lesion presents enrichment of opportunistic pathogenic bacteria.

Leprosy is a chronic infectious disease that remains a major challenge to public health in endemic countries. Increasing evidence has highlighted the importance of microbiota for human general health and, as such, the study of skin microbiota is of interest. But while studies are continuously revealing the complexity of human skin microbiota, the microbiota of leprous cutaneous lesions has not yet been characterized. Here we used Sanger and massively parallel small sub-unit rRNA (SSU) rRNA gene sequencing to characterize the microbiota of leprous lesions, and studied how it differs from the bacterial skin composition of healthy individuals previously described in the literature. Taxonomic analysis of leprous lesions revealed main four phyla: Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, with Proteobacteria presenting the highest diversity. There were considerable differences in the distribution of Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria, with the first two phyla enriched and the other markedly diminished in the leprous lesions, when compared with healthy skin. Propionibacterium, Corynebacterium and Staphylococcus, resident and abundant in healthy skin, were underrepresented in skin from leprous lesions. Most of the taxa found in skin from leprous lesions are not typical in human skin and potentially pathogenic, with the Burkholderia, Pseudomonas and Bacillus genera being overrepresented. Our data suggest significant shifts of the microbiota with emergence and competitive advantage of potentially pathogenic bacteria over skin resident taxa.

Metagenome of a microbial community inhabiting a metal-rich tropical stream sediment.

Here, we describe the metagenome and functional composition of a microbial community in a historically metal-contaminated tropical freshwater stream sediment. The sediment was collected from the Mina Stream located in the Iron Quadrangle (Brazil), one of the world's largest mining regions. Environmental DNA was extracted and was sequenced using SOLiD technology, and a total of 7.9 Gbp was produced. A taxonomic profile that was obtained by comparison to the Greengenes database revealed a complex microbial community with a dominance of Proteobacteria and Parvarcheota. Contigs were recruited by bacterial and archaeal genomes, especially Candidatus Nitrospira defluvii and Nitrosopumilus maritimus, and their presence implicated them in the process of N cycling in the Mina Stream sediment (MSS). Functional reconstruction revealed a large, diverse set of genes for ammonium assimilation and ammonification. These processes have been implicated in the maintenance of the N cycle and the health of the sediment. SEED subsystems functional annotation unveiled a high degree of diversity of metal resistance genes, suggesting that the prokaryotic community is adapted to metal contamination. Furthermore, a high metabolic diversity was detected in the MSS, suggesting that the historical arsenic contamination is no longer affecting the prokaryotic community. These results expand the current knowledge of the microbial taxonomic and functional composition of tropical metal-contaminated freshwater sediments.

The influence of human settlement on the distribution and diversity of iron-oxidizing bacteria belonging to the Gallionellaceae in tropical streams.

Among the neutrophilic iron-oxidizing bacteria (FeOB), Gallionella is one of the most abundant genera in freshwater environments. By applying qPCR and DGGE based on 16S rRNA gene-directed primers targeting Gallionellaceae, we delineated the composition and abundance of the Gallionellaceae-related FeOB community in streams differentially affected by metal mining, and explored the relationships between these community characteristics and environmental variables. The sampling design included streams historically impacted by mining activity and a non-impacted stream. The sediment and water samples harbored a distinct community represented by Gallionella, Sideroxydans, and Thiobacillus species. Sequences affiliated with Gallionella were exclusively observed in sediments impacted by mining activities, suggesting an adaptation of this genus to these environments. In contrast, Sideroxydans-related sequences were found in all sediments including the mining impacted locations. The highest and lowest relative frequencies of Gallionellaceae-related FeOB were associated with the lowest and highest concentrations of Fe, respectively. The data enclosed here clearly show distinct species-specific ecological niches, with Gallionella species dominating in sediments impacted by anthropogenic activities over Sideroxydans species.

A survey on cultivable heterotrophic bacteria inhabiting a thermally unstratified water column in an Atlantic Rainforest lake.

Due to the importance of heterotrophic bacteria in biogeochemical cycles and their influence on water quality, many studies have assessed the composition of the bacterial community. Most of these were made in temperate freshwaters. Eighteen heterotrophic bacteria communities distributed over time and space in the water column of Carioca Lake, not exposed to anthropogenic activities, were analyzed to characterize their composition. A polyphasic approach was used, including 16S rDNA restriction analysis, 16S rRNA gene sequence analysis, BIOLOG Ecoplates and statistical methods. The physiological profiles among the 18 microbial communities were diverse. Clustering analysis and the metabolic fingerprint of the Biolog Ecoplate(TM) system data separated the communities based on temporal scale. A set of 673 isolates were recovered on high nutrient medium. The 673 isolates obtained yielded 360 Amplified Ribosomal DNA Restriction Analysis (ARDRA) Operational Taxonomic Units (OTUs). Most (313) of the ARDRA patterns, OTUs, were from isolates obtained in a single sampling point, in temporal and spatial scales, indicating changes in the bacterial community. A subset of representative isolates for each ARDRA OTU was identified by 16S rRNA gene fragment sequencing and categorized into five phyla, Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Deinococcus-Thermus, represented by 38 genera. The results of this work contribute to a better understanding about the phylogeny of tropical freshwater heterotrophic bacteria.

Bacteria and genes involved in arsenic speciation in sediment impacted by long-term gold mining.

The bacterial community and genes involved in geobiocycling of arsenic (As) from sediment impacted by long-term gold mining were characterized through culture-based analysis of As-transforming bacteria and metagenomic studies of the arsC, arrA, and aioA genes. Sediment was collected from the historically gold mining impacted Mina stream, located in one of the world's largest mining regions known as the "Iron Quadrangle". A total of 123 As-resistant bacteria were recovered from the enrichment cultures, which were phenotypically and genotypically characterized for As-transformation. A diverse As-resistant bacteria community was found through phylogenetic analyses of the 16S rRNA gene. Bacterial isolates were affiliated with Proteobacteria, Firmicutes, and Actinobacteria and were represented by 20 genera. Most were AsV-reducing (72%), whereas AsIII-oxidizing accounted for 20%. Bacteria harboring the arsC gene predominated (85%), followed by aioA (20%) and arrA (7%). Additionally, we identified two novel As-transforming genera, Thermomonas and Pannonibacter. Metagenomic analysis of arsC, aioA, and arrA sequences confirmed the presence of these genes, with arrA sequences being more closely related to uncultured organisms. Evolutionary analyses revealed high genetic similarity between some arsC and aioA sequences obtained from isolates and clone libraries, suggesting that those isolates may represent environmentally important bacteria acting in As speciation. In addition, our findings show that the diversity of arrA genes is wider than earlier described, once none arrA-OTUs were affiliated with known reference strains. Therefore, the molecular diversity of arrA genes is far from being fully explored deserving further attention.

Organic loading rate and food-to-microorganism ratio shape prokaryotic diversity in a demo-scale up-flow anaerobic sludge blanket reactor treating domestic wastewater.

We investigated the microbial community in an up-flow anaerobic sludge blanket (UASB) reactor treating domestic wastewater (DW) during two different periods of organic loading rate (OLR) and food-to-microorganism (F/M) ratio. 16S rDNA clone libraries were generated, and quantitative real-time PCR (qPCR) analyses were performed. Fluctuations in the OLR and F/M ratio affected the abundance and the composition of the UASB prokaryotic community, mainly at the species level, as well as the performance of the UASB reactor. The qPCR analysis suggested that there was a decrease in the bacterial cell number during the rainy season, when the OLR and F/M ratio were lower. However, the bacterial diversity was higher during this time, suggesting that the community degraded more diversified substrates. The diversity and the abundance of the archaeal community were higher when the F/M ratio was lower. Shifts in the methanogenic community composition might have influenced the route of methane production, with methane produced by acetotrophic methanogens (dry season), and by hydrogenotrophic, methylotrophic and acetotrophic methanogens (rainy season). This study revealed higher levels of bacterial diversity, metabolic specialization and chemical oxygen demand removal efficiency of the DW UASB reactor during the rainy season.

The prokaryotic community of a historically mining-impacted tropical stream sediment is as diverse as that from a pristine stream sediment.

Mining negatively affects the environment by producing large quantities of metallic tailings, such as those contaminated with arsenic, with harmful consequences for human and aquatic life. A culture-independent molecular analysis was performed to assess the prokaryotic diversity and community structural changes of the tropical historically metal-contaminated Mina stream (MS) and the relatively pristine Mutuca stream (MTS) sediments. A total of 234 bacterial operational taxonomic units (OTUs) were affiliated with 14 (MS) and 17 (MTS) phyla and 53 OTUs were associated with two archaeal phyla. Although the bacterial community compositions of these sediments were markedly distinct, no significant difference in the diversity indices between the bacterial communities was observed. Additionally, the rarefaction and diversity indices indicated a higher bacterial diversity than archaeal diversity. Most of the OTUs were affiliated with the Proteobacteria and Bacteroidetes phyla. Alphaproteobacteria, Gemmatimonadetes and Actinobacteria were only found in the MS clone library. Crenarchaeal 16S rDNA sequences constituted 75 % of the MS archaeal clones, whereas Euryarchaeota were dominant in the MTS clones. Despite the markedly different characteristics of these streams, their bacterial communities harbor high diversity, suggesting that historically mining-impacted sediments promote diversity. The findings also provide basis for further investigation of members of Alphaproteobacteria as potential biological indicators of arsenic-rich sediments.

Crystal structure, antibacterial and cytotoxic activities of a new complex of bismuth(III) with sulfapyridine.

A new complex of Bi(III) and sulfapyridine was synthesized and characterized by elemental analysis, atomic absorption spectrometry, conductivity analysis, electrospray ionization mass spectrometry (ESI-MS), infrared spectroscopy, and single crystal X-ray diffraction methods. The antimicrobial and the cytotoxic activities of the compound were investigated. Elemental and conductivity analyses are in accordance to the formulation [BiCl3(C11H11N3O2S)3]. The structure of the complex reveals a distorted octahedral geometry around the bismuth atom, which is bound to three sulfonamidic nitrogens from sulfapyridine, acting as a monodentate ligand, and to three chloride ions. The presence of the compound in solution was confirmed by ESI-MS studies. The complex is 3 times more potent than the ligand against Salmonella typhimurium, 4 times against Staphylococcus aureus, Shigella dysenteriae, and Shigella sonnei and 8 times more potent against Pseudomonas aeruginosa and Escherichia coli. The compound inhibits the growth of chronic myelogenous leukemia cells with an IC50 value of 44 µM whereas the free ligand has no effect up to 100 µM.