Bernd Bendinger

Complete nitrification by Nitrospira bacteria

Nitrification, the oxidation of ammonia via nitrite to nitrate, has always been considered to be a two-step process catalysed by chemolithoautotrophic microorganisms oxidizing either ammonia or nitrite. No known nitrifier carries out both steps, although complete nitrification should be energetically advantageous. This functional separation has puzzled microbiologists for a century. Here we report on the discovery and cultivation of a completely nitrifying bacterium from the genus Nitrospira, a globally distributed group of nitrite oxidizers. The genome of this chemolithoautotrophic organism encodes the pathways both for ammonia and nitrite oxidation, which are concomitantly activated during growth by ammonia oxidation to nitrate. Genes affiliated with the phylogenetically distinct ammonia monooxygenase and hydroxylamine dehydrogenase genes of Nitrospira are present in many environments and were retrieved on Nitrospira-contigs in new metagenomes from engineered systems. These findings fundamentally change our picture of nitrification and point to completely nitrifying Nitrospira as key components of nitrogen-cycling microbial communities.

In situ probing reveals Aquabacterium commune as a widespread and highly abundant bacterial species in drinking water biofilms

Abstract Drinking water biofilm communities originated from distribution systems in Hamburg, Berlin, Mainz and Stockholm were subjected to a top-to-bottom in situ analysis with rRNA-targeted, fluorescently labeled oligonucleotide probes including beta1–8, specific for drinking water bacteria within the beta-subclass of Proteobacteria . Independent from the raw water source used, between 19 and 77% of the total attached bacterial cell counts on polyethylen slides could be hybridized with probes beta1–8 and 19–53% of the bacteria were affiliated to the autochthonous species Aquabacterium commune . To investigate seasonal fluctuations of the bacterial population composition, polyethylen slides exposed during different times of the year were analyzed. Although changes in the species composition of the biofilms could be observed, A. commune was a dominant community member in all of the investigated biofilms. In situ probing with two oligonucleotide probes specific for A. commune revealed that during distinct sampling times an additional yet unknown species was present in the biofilm. Material induced population shifts were studied using glass, polyethylene low and high density and soft-PVC as biofilm substrata. The community composition on soft-PVC differed significantly from the other materials, the dominant species A. commune was replaced by other beta- Proteobacteria hybridizing to an amount of 66% with the Aquabacterium citratiphilum specific probe beta4.

Gordona hydrophobica sp. nov., Isolated from Biofilters for Waste Gas Treatment

The taxonomic position of Gordona sp. strain DSM 44015T, isolated from the packing material of a biofilter used for biological odor abatement of animal rendering emissions, has been clarified by a polyphasic study comprising chemotaxonomic, sequencing, and phenotypic results. The strain possesses a wall chemotype IV, MK-9 (H2), as the predominant menaquinone; relatively long-chain mycolic acids (54 to 62 carbon atoms); and straight-chain, saturated, and monounsaturated fatty acids with considerable amounts of tuberculostearic acid. The polar lipids include phosphatidylethanolamine, and the G+C content of the DNA is 69 mol%. Similarity values for genes encoding 16S rRNA indicate that Gordona sp. strain DSM 44015T represents a new species within the genus Gordona for which the name Gordona hydrophobica is proposed.

Biodegradation of NOM in Rapid Sand Filters for Removing Iron and Manganese

In order to examine the Corg flow in rapid sand filter columns for the elimination of iron and manganese, reduced groundwater was treated in a pilot plant consisting of a trickling filter column (TF I) followed by a wet type filter column (WF II) and a separate wet type filter column (WF sep). Additionally the effect of filtration on BOM was studied by measuring AOC and BDOC. The biological processes in TF I and WF sep led to an elimination of iron, ammonia, and manganese. Moreover, the filtration decreased the NOM content. 21% and 23% of the TOC were eliminated in TF I and in WF sep, respectively. WF II caused no significant Corg reduction. The calculation of the Corg flow in the filter columns showed that bacteria took part in the TOC elimination. From the TOC removed, about 24% was eliminated by metabolic activities of the bacterial population whereas 86% was adsorbed onto iron sludge. Similar results were obtained for the TF I column and for the WF sep column as well. The calculated Corg flow was confirmed by the BDOC measurements. The filtration process led to a BDOC decrease. TF I and WF sep reduced appoximately 35% of the biodegradable organic carbon. In contrast there was no significant elimination by WF II. The AOC results suggest that an AOC production and an AOC elimination process exist in rapid sand filters for groundwater treatment. In the trickling filter column significant AOC production was found, whereas in the wet type filter columns AOC elimination was predominating. Biologischer Abbau von NOM in Schnellfiltern zur Enteisenung und Entmanganung Um den Corg-Fluss in Schnellfiltern zur Enteisenung und Entmanganung zu untersuchen, wurde ein reduziertes Grundwasser in einer halbtechnischen Versuchsanlage sowohl durch Trockenfiltration (TF I) mit nachfolgender Nassfiltration (WF II) als auch durch separate Nassfiltration (WF sep) aufbereitet. Weiterhin wurde der Einfluss der Aufbereitung auf den Gehalt an biologisch abbaubaren organischen Wasserinhaltsstoffen mit Hilfe einer AOC- und einer BDOC-Methode untersucht. Die biologischen Prozesse in TF I und WF sep fuhrten zu einer Elimination von Eisen, Ammonium und Mangan. Zudem bewirkte die Filtration eine NOM-Verringerung. Der TOC des Rohwassers wurde durch TF I um 21% bzw. durch WF sep um 23% vermindert. WF II fuhrte zu keiner messbaren TOC-Abnahme. Die Bilanzierung des Corg-Flusses im Filter zeigte, dass die Filterbiozonose an der TOC-Verringerung beteiligt war. Vom eliminierten TOC-Anteil wurden sowohl in TF I als auch im WF[TH]sep ca. 24% durch die metabolische Aktivitat der Bakterienpopulation in den Filtern vermindert und ca. 86% am Eisenschlamm adsorbiert. Die Ergebnisse der Bilanzierung des Corg-Flusses wurden durch die BDOC-Bestimmungen bestatigt. Die Filtration bewirkte eine BDOC-Abnahme. Durch TF I und WF sep wurde der biologisch abbaubare organisch gebundene Kohlenstoff um etwa 35% vermindert. Im Gegensatz dazu veranderte WF II den BDOC nicht. Die AOC-Untersuchungen liesen in den Filtern zur Grundwasseraufbereitung AOC-Produktions- und AOC-Eliminationsprozesse erkennen. Der Trockenfilter fuhrte uberwiegend zur AOC-Produktion, wohingegen der AOC in den Nassfiltern vornehmlich vermindert wurde.

Organic sulfur compounds: persistent odourants in the biological treatment of complex waste gases.

Abstract Rendering activities are important with respect to the conservation of public health. By collecting and processing materials such as dead animal bodies, slaughterhouse offal, blood etc, these potential sources of infectious diseases are eliminated from the environment. However, due to the nature of the materials processed, rendering activities result in the emission of odourous wastes gases, causing odour nuisance in the plants neighbourhood. In order to limit odourous emissions, biological methods for waste gas treatment can be used. In this paper results are presented of measurements of the performance of biological systems for treatment of rendering emissions. Results indicate that elimination efficiencies of the biofilters differ largely with the chemical nature of the volatiles. In rendering waste gases carbonyl compounds are efficiently eliminated. For organic sulfur compounds on the other hand, the efficiency seems to depend on the input concentration but in general, efficiencies are low and unpredictable.

Chemical analysis of isolated cell walls of Gram-positive bacteria and determination of the cell wall to cell mass ratio

Abstract Cell walls of five Gram-positive bacterial strains, including four coryneforms and a Bacillus brevis strain were isolated and subsequently chemically analysed. The wall contribution to the total cell mass is calculated from a comparison of d -Lactate concentrations in hydrolysates of whole cells and isolated walls. d -Lactate concentrations are measured enzymatically after purification of the samples with active carbon. The optimum condition for the quantitative elimination of d -lactate from the peptidoglycan appears to be at 120°C and 4 M HCl. The wall fraction for the cells of the coryneform bacteria are in the range of 26–32% and is about 75% for the B. brevis cells. The peptidoglycan fraction in the walls of the coryneform bacteria was found to be rather high and constitutes about 23 to 31% of the cell wall dry weight. The protein content of the cell wall dry weight is somewhat lower and in the range of 7 to 14%. The peptidoglycan in the wall of the B. brevis strain forms a thin layer and contributes only about 5% to the cell wall dry weight. The high amount of proteins in the B. brevis cell wall (>56%) can be attributed to a so called S(urface)-layer.