Anaerobic benzene mineralization by natural microbial communities from Niger Delta

The Niger Delta is one of the most damaged ecosystems in the world, mainly due to petroleum contamination by oil exploration accidents. We investigated the natural attenuation potential of Niger Delta subsurface sediment samples for anaerobic hydrocarbon degradation using benzene as a model compound under iron-reducing, sulfate-reducing, and methanogenic conditions. Benzene was slowly mineralized under methanogenic and iron-reducing conditions using nitrilotriacetic acid (NTA)-Fe(III), or poorly crystalline Fe(III) oxyhydroxides as electron acceptors, analyzed by measurement of 13CO2 produced from added 13C-labelled benzene. Highest mineralization rates were observed in microcosms amended with Fe(III) oxyhydroxides. The microbial communities of benzene-mineralizing enrichment cultures were characterized by next-generation sequencing of the genes coding for 16S rRNA and methyl coenzyme M reductase A (mcrA). Abundant phylotypes were affiliated to Betaproteobacteriales, Ignavibacteriales, Desulfuromonadales, and Methanosarcinales of the genera Methanosarcina and Methanothrix, illustrating that the enriched benzene-mineralizing communities were diverse and may contain more than a single benzene degrader. The diversity of the microbial communities was furthermore confirmed by scanning helium-ion microscopy which revealed the presence of various rod-shaped as well as filamentous microbial morphotypes.

Nanobacteria associated with mucous intestines of freshwater fishes and tegument of their parasites (Cestoda)

The teguments of four cestode species (Triaenophorus nodulosus, Proteocephalus torulosus, P. percae, P. cernuae) and the intestines of their freshwater fish hosts (Esox lucius, Barbatula barbatula, Perca fluviatilis, Gymnocephalus cernuus) inhabited by bacteria have been investigated with scanning electron microscopy. Most of the bacteria have sizes very similar to nanobacteria (that is, 0.25–0.3 μm in diameter). At least 4 microbial morphotypes were identified. These observations indicate that the normal indigenous microflora in cestodes and their fish hosts, associated with the digestive transport surfaces and consist of bacteria and nanobacteria.

Bacterial aggregation in infected root canal

The aim of this study was to investigate different microbial morphotypes in the root canal infection associated with chronic diffuse periapical lesion. In forty cases of asymptomatic teeth with radiographically diagnosed diffuse periapical lesion we took specimens of infected tissue from the root canals at the beginning of endodontic treatment. Fixation and four different staining methods of the specimens were obtained to provide microscope examination. All examined root canal specimens were heavily infected by bacteria. The most commonly identified were cocci 92 %, small mostly G+ diplococci and large G+cocci in clusters and grapelike groups, bacilli found in 67%, coccobacilli 37%, fungi 17%, and spirochetes in 5%.

Evaluation of Two Upflow Anaerobic Digesters Purifying Industrial Wastewaters High in Organic Matter

Two full-scale anaerobic digesters, one a clarigester purifying a maize processing wastewater and the other with an upflow anaerobic sludge blanket (UASB) configuration treating brewery effluent, contained well settling, granular sludges efficient in pollutant removal. Due to differences in both digester design and feed composition, the sludges differed in activity and microbial population. The clarigester granules contained a diverse population with a multiformity of hydrolytic, acidogenic and acetogenic bacteria while the predominant methanogens, in order of significance, were Methanothrix and Methanosarcina. These granules did not reconstitute on re-start up following digester shutdown and possible reasons for this are discussed. The UASB granules contained a more uniform population with three major microbial morphotypes, the predominant methanogens being Methanothrix and, possibly, Methanobacterium. In this paper the differences in digester design, feed composition, sludge microbiology and process performance are discussed.