Phosphorus composition and release in sediment bacteria of the genus Pseudomonas during aerobic and anaerobic conditions

A substantial amount of sediment phosphorus can be bound in bacterial biomass. In this study the fractional composition of phosphorus in the bacteria Pseudomonas was determined by sequential extraction with ammonium chloride, sodium hydroxide and hydrochloric acid according to the scheme of Hieltjes & Lijklema (1980). Both non-labelled and ³²P-labelled bacteria were used for fractionation. Up to 80% of the bacterial phosphorus was found in the NaOH-nRP fraction, which is in agreement with the results of Hupfer & Uhlman (1992) for Acinetobacter and activated sludge obtained with the sequential extraction scheme of Psenner et al. (1985). A significant correlation was found between bacterial biomass and the amount of phosphorus retained in the NaOH-nRP fraction when sediments were fractionated. Additional experiments with ³²P-labelled Pseudomonas in sediment-water systems were performed in order to follow bacterial release of phosphorus under aerobic and anaerobic conditions. These studies did not sustain the hypothesis that anaerobic conditions lead to rapid release of phosphorus from bacterial cells.     

The rate of permafrost carbon release under aerobic and anaerobic conditions and its potential effects on climate

Recent observations suggest that permafrost thaw may create two completely different soil environments: aerobic in relatively well‐drained uplands and anaerobic in poorly drained wetlands. The soil oxygen availability will dictate the rate of permafrost carbon release as carbon dioxide (CO₂) and as methane (CH₄), and the overall effects of these emitted greenhouse gases on climate. The objective of this study was to quantify CO₂ and CH₄ release over a 500‐day period from permafrost soil under aerobic and anaerobic conditions in the laboratory and to compare the potential effects of these emissions on future climate by estimating their relative climate forcing. We used permafrost soils collected from Alaska and Siberia with varying organic matter characteristics and simultaneously incubated them under aerobic and anaerobic conditions to determine rates of CO₂ and CH₄ production. Over 500 days of soil incubation at 15 °C, we observed that carbon released under aerobic conditions was 3.9–10.0 times greater than anaerobic conditions. When scaled by greenhouse warming potential to account for differences between CO₂ and CH₄, relative climate forcing ranged between 1.5 and 7.1. Carbon release in organic soils was nearly 20 times greater than mineral soils on a per gram soil basis, but when compared on a per gram carbon basis, deep permafrost mineral soils showed carbon release rates similar to organic soils for some soil types. This suggests that permafrost carbon may be very labile, but that there are significant differences across soil types depending on the processes that controlled initial permafrost carbon accumulation within a particular landscape. Overall, our study showed that, independent of soil type, permafrost carbon in a relatively aerobic upland ecosystems may have a greater effect on climate when compared with a similar amount of permafrost carbon thawing in an anaerobic environment, despite the release of CH₄ that occurs in anaerobic conditions.     

Swarming characteristics of Proteus mirabilis under anaerobic and aerobic conditions

Nutrients have a pronounced effect on the growth and swarming behaviour of Proteus mirabilis 7002. Iron, zinc, amino acids, and dioxygen are important for rapid growth and normal swarming. Anaerobically grown cultures of P. mirabilis 7002 were unable to swarm on anaerobically maintained rich nutrient agar. Upon exposure to aerobic conditions, P. mirabilis 7002 resumed swarming behaviour. Scanning electron microscopy was used to demonstrate the presence of community organization and mature rafts during normal swarming. These results support the importance of dioxygen and redox status in cell differentiation.     

Siderophore production by Pseudomonas stutzeri under aerobic and anaerobic conditions

The siderophore production of the facultative anaerobe Pseudomonas stutzeri, strain CCUG 36651, grown under both aerobic and anaerobic conditions, was investigated by liquid chromatography and mass spectrometry. The bacterial strain has been isolated at a 626-m depth at the Äspö Hard Rock Laboratory, where experiments concerning the geological disposal of nuclear waste are performed. In bacterial culture extracts, the iron in the siderophore complexes was replaced by gallium to facilitate siderophore identification by mass spectrometry. P. stutzeri was shown to produce ferrioxamine E (nocardamine) as the main siderophore together with ferrioxamine G and two cyclic ferrioxamines having molecular masses 14 and 28 atomic mass units lower than that of ferrioxamine E, suggested to be ferrioxamine D₂ and ferrioxamine X₁, respectively. In contrast, no siderophores were observed from anaerobically grown P. stutzeri. None of the siderophores produced by aerobically grown P. stutzeri were found in anaerobic natural water samples from the Äspö Hard Rock Laboratory.In order to facilitate iron(III) acquisition, plants and microorganisms, such as fungi and bacteria, produce and excrete strong iron(III) chelators, i.e., siderophores (18, 22, 23, 33, 34). While fungal siderophores bind to iron(III) by hydroxamate ligands, bacterial siderophores are more structurally diverse, and common ligands are catecholates, hydroxamates, and carboxylates (21). The iron(III) stability constants for bacterial siderophores vary in the range of 10²⁰ to 10⁵² (6). In addition to iron(III), other metals can be complexed by siderophores. For the trihydroxamate siderophore desferrioxamine B, sometimes called proferrioxamine B (10), some actinides have been shown to have stability constants in the same range as the ferric stability constant (10^30.6), e.g., 10^26.6 with thorium(IV) and 10^30.8 with plutonium(VI) (32), while the stability constant for uranium(VI) was lower, i.e., 10¹⁸ (2).Concerning bacteria, there are several reports on siderophore production by Pseudomonas spp. (1, 3, 4, 19). More than 50 structurally related siderophores, i.e., pyoverdins, produced by the fluorescent Pseudomonas spp., especially Pseudomonas fluorescens and Pseudomonas aeruginosa, have been characterized (3). All pyoverdins emit yellow fluorescent light due to the presence of a 5-amino-2,3-dihydro-8,9-dihydroxy-1-H-pyrimido-quinoline-carboxylic chromophore, to which a peptide chain and a carboxyl chain are attached (1, 3). Nonfluorescent Pseudomonas has also been shown to produce siderophores, such as ferrioxamine E, also called nocardamine (Fig. ​(Fig.1),1), which was produced by one strain of Pseudomonas stutzeri (19). In addition to ferrioxamines, the P. stutzeri strain KC produced a smaller siderophore, i.e., pyridine-2,6-bis(thiocarboxylic acid) (35). Conversely, a catecholate-type siderophore was shown to be produced by another strain of P. stutzeri, which did not produce any hydroxamate siderophores (4).Open in a separate windowFIG. 1.Structures, molecular masses (mw), and stability constants (K_s) of ferric complexes of the three ferrioxamines: ferrioxamine B (B), ferrioxamine E (E), and ferrioxamine G (G) (5, 18).Most of the studies on bacterial siderophore production have been conducted on microorganisms growing under aerobic conditions. One field-based report, however, indicates the occurrence of putative siderophores in anaerobic environments also (29). In the present study, siderophore production has been studied with both aerobic and anaerobic cultures of P. stutzeri. This species is a facultative aerobe, able to grow with oxygen or nitrate as the electron acceptor, meaning that it can be active under both anaerobic and aerobic conditions. The P. stutzeri strain CCUG 36651, studied here, has been isolated from a depth of 626 m below ground at the Äspö Hard Rock Laboratory (16), where research concerning the geological disposal of nuclear waste is performed. The possibility of mobilizing radionuclides by complexing compounds from bacteria is an important research area in the context of nuclear waste disposal research. It is unknown if such compounds are produced in aquifers under conditions relevant to a disposal site, which would be approximately 500 m underground in granitic rock (27).A study from 2004 shows that P. stutzeri growing aerobically in the presence of uranium-containing shale leached Fe, Mo, V, and Cr from the shale material (17). More recently it was shown that the supernatant of aerobically and anaerobically cultured P. stutzeri was able to increase the partitioning of added Fe, Pm, Am, and Th into the aqueous phase in samples where quartz sand was used as a solid surface (16). Aerobic supernatants maintained 60% or more of the added metals in solution, while anaerobic supernatants were best at maintaining Am in solution, reaching a value of 40% in solution. The increased partitioning to the aqueous phase in the presence of the supernatants was ascribed to the production of organic ligands. Supernatants of both aerobically and anaerobically grown P. stutzeri strain CCUG 36651 yielded a positive response on the universal siderophore assay, the CAS assay (16). This assay is based on ligand competition for iron bound to the colored chrome azurol complex (25, 30).In this study, siderophore production by P. stutzeri strain CCUG 36651 was investigated using mass spectrometry (MS) and liquid chromatography (LC) followed by mass spectrometric detection. Electrospray ionization mass spectrometry (ESI-MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) are useful tools in characterizing siderophores such as ferrioxamines (10, 13, 14, 28, 31). In order to detect iron(III)-chelating compounds, the ferric iron can be replaced by gallium(III) through ascorbate-mediated reduction of iron(III) (8, 20). In mass spectra, gallium-bound substances are easily recognized due to the characteristic isotope pattern of gallium, where the intensity of the ⁷¹Ga signal is about 66% of that of the ⁶⁹Ga signal. The use of ESI provides so-called soft ionization; thus, information about the molecular weight is obtained. However, by employing MS/MS, fragmentation is achieved, providing more information about the compound structure.In order to verify the chemical difference between the siderophores found by ESI-MS, chromatographic separation was performed. In this case, one reversed-phase C₁₈ column and one column containing a porous graphitic carbon (PGC) stationary phase were used. The separation mechanism of PGC is a combination of hydrophobic interactions, as in C₁₈, and electrostatic interactions between π-electrons. In order to detect substances at low concentrations, column-switched capillary chromatography with MS detection was used. The detection limits of the combined LC-MS/MS system used in this study are in the range of 1 to 5 nM for hydroxamate siderophores of the ferrichrome and ferrioxamine families (9). In order to facilitate analysis of lower concentrations of ferrioxamines, natural water samples were preconcentrated by solid-phase extraction (SPE), resulting in minimum detectable concentrations in the range of 0.02 to 0.1 nM, depending on the initial sample volume.     

Establishment of anaerobic,reducing conditions in lake sediment after deposition of acidic,aerobic sediment by a major storm

Hurricane Danny resulted in the rapid deposition of 10cm of oxidized, acidic sediment in the Contrary Creek arm of Lake Anna, Virginia. Several biological and geochemical parameters were monitored with time to ascertain how long it took the newly-deposited lake sediments to attain the anaerobic, circumneutral, actively sulfate-reducing state normally observed in this portion of the lake. The sediment platinum-electrode potential dropped from 350 mV to 100 mV within the first week after the storm. The pH of the pore water increased from 4.5 to 5.8 within three weeks, and titratable alkalinity was detected within two weeks and three weeks at 3 cm and 1 cm depths, respectively. Accumulation of reduced products of sulfate reduction (acid volatile sulfide) began by three to four weeks after the storm event. Both methanogens and sulfate reducers were present in high and approximately equal numbers in the freshly deposited material. The rapid neutralization of the acidity in the fresh sediment prior to the onset of sulfate reduction suggests that reactions other than sulfate reduction caused the initial increase in pH and alkalinity in this system.     

传统厌氧/好氧生物除磷与厌氧/缺氧反硝化除磷效能的比较

采用序批式反应器(SBR),对比厌氧/好氧(A/O)和厌氧/缺氧(A/A)2种运行模式对模拟生活和工业混合污水同时脱氮除磷的效能。结果表明:反硝化聚磷菌完全可以在厌氧/缺氧交替运行条件下得到富集,稳定运行的2种模式对有机物和P的去除率分别保持在90%和85%以上,且A/A SBR具有更强的释磷能力,其释磷量比A/O SBR高出1.2倍。进一步试验表明:磷的释放在有无硝酸盐的情况下效果是不同的。2个系统内污泥均有反硝化除磷能力,A/A SBR中所含反硝化聚磷菌(DPAO)的比例是A/O SBR的4.56倍。2种模式出水水质都能取得较好的效果,且能实现同步除磷脱氮,而反硝化除磷在生物除磷方面更具优势。     

Behaviour of toluene, benzene and naphthalene under anaerobic conditions in sediment columns

The biotransformation of toluene, benzene and naphthalene was examined in anaerobic sediment columns. Five columns filled with a mixture of sediments were operated in the presence of bicarbonate, sulfate, iron, manganese, or nitrate as electron acceptor. The columns were continuously percolated with a mixture of the three organic compounds (individual concentrations 25–200 M) at 20°C.Toluene was transformed readily (within 1 to 2 months) under all redox conditions tested. Benzene was recalcitrant over the test period of 375–525 days in all five columns. Naphthalene was partly transformed in the column with nitrate or manganese as electron acceptor present; the addition of benzoate had a positive effect in the column with nitrate. In the column with sulfate, the majority of the added naphthalene disappeared. No effect was observed after adding and omitting an easier degradable substrate. [¹⁴C]naphthalene was used to confirm this disappearance to be the result of degradation; two third of the naphthalene was converted to CO₂.     

Detoxification of furfural in Corynebacterium glutamicum under aerobic and anaerobic conditions

The toxic fermentation inhibitors in lignocellulosic hydrolysates raise serious problems for the microbial production of fuels and chemicals. Furfural is considered to be one of the most toxic compounds among these inhibitors. Here, we describe the detoxification of furfural in Corynebacterium glutamicum ATCC13032 under both aerobic and anaerobic conditions. Under aerobic culture conditions, furfuryl alcohol and 2-furoic acid were produced as detoxification products of furfural. The ratio of the products varied depending on the initial furfural concentration. Neither furfuryl alcohol nor 2-furoic acid showed any toxic effect on cell growth, and both compounds were determined to be the end products of furfural degradation. Interestingly, unlike under aerobic conditions, most of the furfural was converted to furfuryl alcohol under anaerobic conditions, without affecting the glucose consumption rate. Both the NADH/NAD⁺ and NADPH/NADP⁺ ratio decreased in the accordance with furfural concentration under both aerobic and anaerobic conditions. These results indicate the presence of a single or multiple endogenous enzymes with broad and high affinity for furfural and co-factors in C. glutamicum ATCC13032.     

Bacterial survival and association with sludge flocs during aerobic and anaerobic digestion of wastewater sludge under laboratory conditions.

The fate of indicator bacteria, a bacterial pathogen, and total aerobic bacteria during aerobic and anaerobic digestion of wastewater sludge under laboratory conditions was determined. Correlation coefficients were calculated between physical and chemical parameters (temperature, dissolved oxygen, pH, total solids, and volatile solids) and either the daily change in bacterial numbers or the percentage of bacteria in the supernatant. The major factor influencing survival of Salmonella typhimurium and indicator bacteria during aerobic digestion was the temperature of sludge digestion. At 28 degrees C with greater than 4 mg of dissolved oxygen per liter, the daily change in numbers of these bacteria was approximately -1.0 log10/ml. At 6 degrees C, the daily change was less than -0.3 log10/ml. Most of the bacteria were associated with the sludge flocs during aerobic digestion of sludge at 28 degrees C with greater than 2.4 mg of dissolved oxygen per liter. Lowering the temperature or the amount of dissolved oxygen decreased the fraction of bacteria associated with the flocs and increased the fraction found in the supernatant.     

Behaviour of toluene, benzene and naphthalene under anaerobic conditions in sediment columns

The biotransformation of toluene, benzene and naphthalene was examined in anaerobic sediment columns. Five columns filled with a mixture of sediments were operated in the presence of bicarbonate, sulfate, iron, manganese, or nitrate as electron acceptor. The columns were continuously percolated with a mixture of the three organic compounds (individual concentrations 25–200 μM) at 20°C. Toluene was transformed readily (within 1 to 2 months) under all redox conditions tested. Benzene was recalcitrant over the test period of 375–525 days in all five columns. Naphthalene was partly transformed in the column with nitrate or manganese as electron acceptor present; the addition of benzoate had a positive effect in the column with nitrate. In the column with sulfate, the majority of the added naphthalene disappeared. No effect was observed after adding and omitting an easier degradable substrate. [¹⁴C]naphthalene was used to confirm this disappearance to be the result of degradation; two third of the naphthalene was converted to CO₂.     

Performance and diversity of polyvinyl alcohol-degrading bacteria under aerobic and anaerobic conditions

Objectives

To compare the degradation performance and biodiversity of a polyvinyl alcohol-degrading microbial community under aerobic and anaerobic conditions.

Results

An anaerobic–aerobic bioreactor was operated to degrade polyvinyl alcohol (PVA) in simulated wastewater. The degradation performance of the bioreactor during sludge cultivation and the microbial communities in each reactor were compared. Both anaerobic and aerobic bioreactors demonstrated high chemical oxygen demand removal efficiencies of 87.5 and 83.6 %, respectively. Results of 16S rDNA sequencing indicated that Proteobacteria dominated in both reactors and that the microbial community structures varied significantly under different operating conditions. Both reactors obviously differed in bacterial diversity from the phyla Planctomycetes, Chlamydiae, Bacteroidetes, and Chloroflexi. Betaproteobacteria and Alphaproteobacteria dominated, respectively, in the anaerobic and aerobic reactors.

Conclusions

The anaerobic–aerobic system is suitable for PVA wastewater treatment, and the microbial genetic analysis may serve as a reference for PVA biodegradation.