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PubMed2002

Calorimetry: a tool for assessing microbial activity under aerobic and anoxic conditions.

For many years, calorimetric measurements have been used for understanding, modelling, controlling, and optimising chemical reactions. Calorimetry could be as well utilised to investigate biological processes, which however, involve very small amount of heat and therefore require very sensitive instruments. For this purpose, a Mettler Toledo RCI (Reaction calorimeter) was modified, changing both hardware and software, increasing its resolution up to 5 10m W/l. Such sensitivity allows the monitoring of aerobic and anoxic processes. This paper points out the excellent agreement between calorimetric and respirometric data, obtained simultaneously under aerobic conditions using activated sludge from a lab-scale scale reactor. Heat production rate can be directly converted in oxygen uptake rate by means of a correlation factor, whose value is approximately the same for all aerobic respiratory metabolisms. Taking into account this factor, calorimetric data were introduced in a chemical oxygen demand based model and processed for the estimation of kinetic parameters of heterotrophic biomass. Aerobic heterotrophic, denitrifying, and autotrophic nitrifying activity were determined by specific calorimetric tests. The effect of potentially toxic or inhibitory substances on the activity of all microbial communities was as well pointed out in these measurements.

Bacteria, Aerobic↗

PubMed1977

Epigenetic variation of cultured somatic cells: evidence for gradual changes in the requirement for factors promoting cell division.

Cells of higher plant species in culture sometimes lose their requirement for an exogenous supply of a cell division factor that, thereafter, they are able to produce. This heritable change, known as cytokinin habituation, appears to be an epigenetic one rather than a classical mutation because it is directed, potentially reversible, leaves the cell totipotent, and involves the expression of a latent differentiated function. By using cloned cell lines derived from pith parenchyma of tobacco, we have obtained evidence that the habituation process is gradual rather than all-or-none and leads to progressively more autotrophic tissues. Cells in culture show reversible shifts among a range of habituated states but remain totipotent and can be induced to regain their requirement for a cell division factor. Thus, it appears that habituation involves epigenetic changes in a quantitative cellular phenotype. Our findings support the hypothesis that tumor progression in crown gall, a neoplastic disease of higher plants, can be accounted for by heritable changes in the pattern of gene expression.

Cell Differentiation↗

PubMed1981

Physiological and ultrastructural characterization of a new acidophilic Thiobacillus species (T. kabobis).

A new autotrophic acidophilic Thiobacillus sp. was isolated from acidic soil adjacent to a natural gas processing plant's sulfur stockpile. This isolate metabolized S2O3(2-) to S4O6(2-) during growth and could not reoxidize this product; instead, the remaining S2O3(2-) substrate was oxidized to SO4(2-) in the stationary phase which represented a significant metabolic change as compared with other acidophilic thiobacilli. In contrast the isolate oxidized S0 to H2SO4 during the log-phase growth with no S4O6(2-) being formed. Ultrastructural studies revealed that the isolate's cytoplasm contained unidentified membrane-bound granules, volutin type bodies, and carboxysomes. Cleavage planes within the cell wall revealed a pattern of highly ordered subunits in the outer leaflet of the outer membrane and these ordered subunits were also discerned through the eutectic at the cell surface. This regular structure was not observed at the surface of cells of other acidophilic thiobacilli. The isolate bears a single pilus and one unusually long polar flagellum. The physiological and ultrastructural data are discussed in relation to other known thiobacilli and show this isolate to be a new Thiobacillus sp. named T. kabobis.

Cell Membrane↗

PubMedDate not supplied

[Carbon metabolism of filamentous anoxygenic phototrophic bacteria of the family Oscillochloridaceae].

The carbon metabolism of representatives of the family Oscillochloridaceae (Oscillochloris trichoides DG6 and the recent isolates Oscillochloris sp. R, KR, and BM) has been studied. Based on data from an inhibitory analysis of autotrophic CO2 assimilation and measurements of the activities of the enzymes involved in this process, it is concluded that, in all Oscillochloris strains, CO2 fixation occurs via the operation of the Calvin cycle. Phosphoenolpyruvate (PEP), which is formed in this cycle, can be involved in the metabolism via the following reaction sequence: PEP (+ CO2) --> oxalacetate --> malate --> fumarate --> succinate --> succinyl-CoA (+ CO2) --> 2-oxoglutarate (+ CO2) --> isocitrate. Acetate, utilized as and additional carbon source, can be carboxylated to pyruvate by pyruvate synthase and further involved in the metabolism via the above reaction sequence. Propionyl-CoA synthase and malonyl-CoA reductase, the key enzymes of the 3-hydroxypropionate cycle, have not been detected in Oscillochloris representatives.

Acetates↗

PubMed2005

Characteristics and adaptability of iron- and sulfur-oxidizing microorganisms used for the recovery of metals from minerals and their concentrates.

Microorganisms are used in large-scale heap or tank aeration processes for the commercial extraction of a variety of metals from their ores or concentrates. These include copper, cobalt, gold and, in the past, uranium. The metal solubilization processes are considered to be largely chemical with the microorganisms providing the chemicals and the space (exopolysaccharide layer) where the mineral dissolution reactions occur. Temperatures at which these processes are carried out can vary from ambient to 80 degrees C and the types of organisms present depends to a large extent on the process temperature used. Irrespective of the operation temperature, biomining microbes have several characteristics in common. One shared characteristic is their ability to produce the ferric iron and sulfuric acid required to degrade the mineral and facilitate metal recovery. Other characteristics are their ability to grow autotrophically, their acid-tolerance and their inherent metal resistance or ability to acquire metal resistance. Although the microorganisms that drive the process have the above properties in common, biomining microbes usually occur in consortia in which cross-feeding may occur such that a combination of microbes including some with heterotrophic tendencies may contribute to the efficiency of the process. The remarkable adaptability of these organisms is assisted by several of the processes being continuous-flow systems that enable the continual selection of microorganisms that are more efficient at mineral degradation. Adaptability is also assisted by the processes being open and non-sterile thereby permitting new organisms to enter. This openness allows for the possibility of new genes that improve cell fitness to be selected from the horizontal gene pool. Characteristics that biomining microorganisms have in common and examples of their remarkable adaptability are described.

Journal Article↗

PubMed2003

Complete denitrification in coculture of obligately chemolithoautotrophic haloalkaliphilic sulfur-oxidizing bacteria from a hypersaline soda lake.

Eight anaerobic enrichment cultures with thiosulfate as electron donor and nitrate as electron acceptor were inoculated with sediment samples from hypersaline alkaline lakes of Wadi Natrun (Egypt) at pH 10; however, only one of the cultures showed stable growth with complete nitrate reduction to dinitrogen gas. The thiosulfate-oxidizing culture subsequently selected after serial dilution developed in two phases. Initially, nitrate was mostly reduced to nitrite, with a coccoid morphotype prevailing in the culture. During the second stage, nitrite was reduced to dinitrogen gas, accompanied by mass development of thin motile rods. Both morphotypes were isolated in pure culture and identified as representatives of the genus Thioalkalivibrio, which includes obligately autotrophic sulfur-oxidizing haloalkaliphilic species. Nitrate-reducing strain ALEN 2 consisted of large nonmotile coccoid cells that accumulated intracellular sulfur. Its anaerobic growth with thiosulfate, sulfide, or polysulfide as electron donor and nitrate as electron acceptor resulted in the formation of nitrite as the major product. The second isolate, strain ALED, was able to grow anaerobically with thiosulfate as electron donor and nitrite or nitrous oxide (but not nitrate) as electron acceptor. Overall, the action of two different sulfur-oxidizing autotrophs resulted in the complete, thiosulfate-dependent denitrification of nitrate under haloalkaliphilic conditions. This process has not yet been demonstrated for any single species of chemolithoautotrophic sulfur-oxidizing haloalkaliphiles.

Cell Division↗

PubMed2001

Kinetic model of autotrophic denitrification in sulphur packed-bed reactors.

Autotrophic denitrification of synthetic wastewater by Thiobacillus denitrificans in upflow sulphur packed-bed reactors was studied in order to establish the process kinetics for prediction of effluent concentration. Elemental sulphur particles of different size served as energy substrate as well as the physical support for the microbial biofilm. Experiments were performed under operating conditions of (i) different flow rates at constant influent nitrate concentration; and (ii) different influent nitrate concentrations at constant flow rate. The experimental results show that autotrophic denitrification rates in upflow sulphur packed-bed reactors can be described by a half-order kinetic model for biofilms. It was found that the half-order kinetic constants of upflow packed-bed reactors are 2.94-3.60, 1.47-2.04, and 1.12-1.29 mg1/2/L1/2 h for sulphur particle sizes of 2.8-5.6, 5.6-11.2, and 11.2-16 mm, respectively. The half-order kinetic constants could be related to the specific surface area of the reactor media by a simple equation. Successful application of the half-order reaction rate model was demonstrated for an actual wastewater (nitrified leachate). A comparison with the literature showed that the half-order reaction rate constants for autotrophic denitrification using elemental sulphur are approximately one order of magnitude lower than those of heterotrophic denitrification. An improved stoichiometric equation for autotrophic denitrification using elemental sulphur as electronic donor is also proposed.

Biodegradation, Environmental↗

PubMed1998

The anaerobic oxidation of ammonium.

From recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'Aerobic' ammonium oxidizers like Nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. The maximum rate for anaerobic ammonium oxidation was about 2 nmol NH4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor. This reaction, which may involve NO as an intermediate, is thought to generate energy sufficient for survival under anoxic conditions, but not for growth. A novel obligately anaerobic ammonium oxidation (Anammox) process was recently discovered in a denitrifying pilot plant reactor. From this system, a highly enriched microbial community with one dominating peculiar autotrophic organism was obtained. With nitrite as electron acceptor a maximum specific oxidation rate of 55 nmol NH4+ min-1 (mg protein)-1 was determined. Although this reaction is 25-fold faster than in Nitrosomonas, it allowed growth at a rate of only 0.003 h-1 (doubling time 11 days). 15N labeling studies showed that hydroxylamine and hydrazine were important intermediates in this new process. A novel type of hydroxylamine oxidoreductase containing an unusual P468 cytochrome has been purified from the Anammox culture. Microsensor studies have shown that at the oxic/anoxic interface of many ecosystems nitrite and ammonia occur in the absence of oxygen. In addition, the number of reports on unaccounted high nitrogen losses in wastewater treatment is gradually increasing, indicating that anaerobic ammonium oxidation may be more widespread than previously assumed. The recently developed nitrification systems in which oxidation of nitrite to nitrate is prevented form an ideal partner for the Anammox process. The combination of these partial nitrification and Anammox processes remains a challenge for future application in the removal of ammonium from wastewater with high ammonium concentrations.

Anaerobiosis↗

PubMed1990

The small-scale production of [U-14C]acetylene from Ba14CO3: application to labeling of ammonia monooxygenase in autotrophic nitrifying bacteria.

A small-scale method has been adapted from an established procedure for the generation of [U-14C]acetylene from inexpensive and commonly available precursors. The method involves the fusing of Ba14CO3 with excess barium metal to produce Ba14C2. The BaC2 is reacted with water to generate acetylene which is then selectively dissolved into dimethyl sulfoxide (DMSO). The results presented demonstrate the effect of Ba:BaCO3 ratio on the concentrations of various gases released during the hydrolysis reaction and quantify the selectivity of the DMSO-trapping process for each gas. [U-14C]Acetylene generated by this method has been used to inactivate ammonia monooxygenase in three species of autotrophic nitrifying bacteria: Nitrosomonas europaea, Nitrosococcus oceanus, and Nitrosolobus multiformis. Our results demonstrate that acetylene inactivation of this enzyme in all three species results in the covalent incorporation of radioactive label into a polypeptide of apparent Mr of 25,000-27,000, as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis and fluorography.

Acetylene↗

PubMed2004

Start-up of autotrophic nitrogen removal reactors via sequential biocatalyst addition.

A procedure for start-up of oxygen-limited autotrophic nitrification-denitrification (OLAND) in a lab-scale rotating biological contactor (RBC) is presented. In this one-step process, NH4+ is directly converted to N2 without the need for an organic carbon source. The approach is based on a sequential addition of two types of easily available biocatalyst to the reactor during start-up: aerobic nitrifying and anaerobic, granular methanogenic sludge. The first is added as a source of aerobic ammonia-oxidizing bacteria (AAOB), the second as a possible source of planctomycetes including anaerobic ammonia-oxidizing bacteria (AnAOB). The initial nitrifying biofilm serves as a matrix for anaerobic cell incorporation. By subsequently imposing oxygen limitation, one can create an optimal environment for autotrophic N removal. In this way, N removal of about 250 mg of N L(-1) d(-1) was achieved after 100 d treating a synthetic NH4+-rich wastewater. By gradually imposing higher loads on the reactor, the N elimination could be increased to about 1.8 g of N L(-1) d(-1) at 250 d. The resulting microbial community was compared with that of the inocula using general bacterial and AAOB- and planctomycete-specific PCR primers. Subsequently, the RBC reactor was shown to treat a sludge digestor effluent under suboptimal and strongly varying conditions. The RBC biocatalyst was also submitted to complete absence of oxygen in a fixed-film bioreactor (FFBR) and proved able to remove NH4+ with NO2- as electron acceptor (maximal 434 mg of NH4+-N (g of VSS)(-1) d(-1) on day 136). DGGE and real-time PCR analysis demonstrated that the RBC biofilm was dominated by members of the genus Nitrosomonas and close relatives of Kuenenia stuttgartiensis, a known AnAOB. The latter was enriched during FFBR operation, but AAOB were still present and the ratio planctomycetes/AAOB rRNA gene copies was about 4.3 after 136 d of reactor operation. Whether this relates to an active role of AAOB in the anoxic N removal process remains to be solved.

Bacteria, Aerobic↗

PubMed2006

Interactive effects of light and nutrients on phytoplankton stoichiometry.

The stoichiometric composition of autotrophs can vary greatly in response to variation in light and nutrient availability, and can mediate ecological processes such as C sequestration, growth of herbivores, and nutrient cycling. We investigated light and nutrient effects on phytoplankton stoichiometry, employing five experiments on intact phytoplankton assemblages from three lakes varying in productivity and species composition. Each experiment employed two nutrient and eight irradiance levels in a fully factorial design. Light and nutrients interactively affected phytoplankton stoichiometry. Thus, phytoplankton C:N, C:P, and N:P ratios increased with irradiance, and slopes of the stoichiometric ratio versus irradiance relationships were steeper with ambient nutrients than with nutrients added. Our results support the light-nutrient hypothesis, which predicts that phytoplankton C:nutrient ratios are functions of the ratio of available light and nutrients; however, we observed considerable variation among lakes in the expression of this relationship. Phytoplankton species diversity was positively correlated with the slopes of the C:N and C:P versus irradiance relationships, suggesting that diverse assemblages may exhibit greater flexibility in the response of phytoplankton nutrient stoichiometry to light and nutrients. The interactive nature of light and nutrient effects may render it difficult to generate predictive models of stoichiometric responses to these two factors. Our results point to the need for future studies that examine stoichiometric responses across a wide range of phytoplankton communities.

Animals↗

PubMedDate not supplied

[Kinetic parameters of a culture of the hydrogen-oxidizing Ralstonia eutropha, grown under the regimen of biosynthesis of polyhydroxybutyrate].

Kinetic parameters of a culture of the hydrogen-oxidizing bacterium Ralstonia eutropha, grown on a gas substrate under the conditions favoring autotrophic biosynthesis of polyhydroxybutyrate, were studied. The following parameters, making it possible to control and optimize the process in industrial situations, were determined: specific rate of substrate consumption, physical properties of culture medium, and coefficients of heat emission and mass transfer.

Culture Media↗

PubMed2004

Patterns of intramolecular carbon isotopic heterogeneity within amino acids of autotrophs and heterotrophs.

A survey of the intramolecular C isotopic composition of a variety of organisms was conducted to investigate the potential of intramolecular isotopic measurements as a tracer of biological or geochemical processes. Based on a consideration of inorganic C sources and enzymatic fractionations, contrasting predictions were made for the relative (13)C enrichments of the alpha-carboxyl carbons fixed by the anapleurotic (beta)-carboxylation pathway during amino acid synthesis by photoautotrophs and heterotrophs. To test the model predictions, the stable C isotopic compositions of the acid hydrolyzable C fraction, the total amino acid alpha-carboxyl C fraction and the alpha-carboxyl C of glutamate from a variety of autotrophic and heterotrophic organisms were compared. The relative (13)C enrichments of carboxyl carbons in the bulk amino acid fraction and in glutamate conformed qualitatively to model predictions. Macroalgal taxa possessed a significantly less enriched carboxyl C fraction than did either C3 or C4 vascular plants, indicating the presence of a different beta-carboxylation pathway operating in these organisms. In most multicellular heterotrophs, the isotopic composition of the amino acid carboxyl carbons closely resembled that of their food sources. Amino acids are apparently assimilated into tissue proteins directly from their diets without significant metabolic modification. However, shifts in the isotopic composition of the carboxyl C fractions in some organisms were detected that were consistent with the occurrence of significant resynthesis of amino acids from non-amino acid precursors. Comparison of plant leaves and roots provided evidence of environmentally controlled assimilate partitioning. Intramolecular isotopic measurements of biological molecules provide unique insights into the origins and transformations of bio-molecules.

Amino Acids↗

PubMed2003

Nitrification, denitrification and biological phosphorus removal in piggery wastewater using a sequencing batch reactor.

Nutrients in piggery wastewater with high organic matter, nitrogen (N) and phosphorus (P) content were biologically removed in a sequencing batch reactor (SBR) with anaerobic, aerobic and anoxic stages. The SBR was operated with 3 cycles/day, temperature 30 degrees C, sludge retention time (SRT) 1 day and hydraulic retention time (HRT) 11 days. With a wastewater containing 1500 mg/l ammonium and 144 mg/l phosphate, a removal efficiency of 99.7% for nitrogen and 97.3% for phosphate was obtained. Experiments set up to evaluate the effect of temperature on the process showed that it should be run at temperatures higher than 16 degrees C to obtain good removals (> 95%). Batch tests (ammonia utilization rate, nitrogen utilization rate and oxygen utilization rate) proved to be good tools to evaluate heterotrophic and autotrophic biomass activity. The SBR proved to be a very flexible tool, and was particularly suitable for the treatment of piggery wastewater, characterized by high nutrient content and by frequent changes in composition and therefore affecting process conditions.

Animals↗

PubMed2000

The responses of photosynthesis and oxygen consumption to short-term changes in temperature and irradiance in a cyanobacterial mat (Ebro Delta, Spain).

We have evaluated the effects of short-term changes in incident irradiance and temperature on oxygenic photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat from the Ebro Delta, Spain, in which Microcoleus chthonoplastes was the dominant phototrophic organism. The mat was incubated in the laboratory at 15, 20, 25 and 30 degrees C at incident irradiances ranging from 0 to 1,000 micromol photons m(-2) s(-1). Oxygen microsensors were used to measure steady-state oxygen profiles and the rates of gross photosynthesis, which allowed the calculation of areal gross photosynthesis, areal net oxygen production, and oxygen consumption in the aphotic layer of the mat. The lowest surface irradiance that resulted in detectable rates of gross photosynthesis increased with increasing temperature from 50 micromol photons m(-2) s(-1) at 15 degrees C to 500 micromol photons m(-2) s(-1) at 30 degrees C. These threshold irradiances were also apparent from the areal rates of net oxygen production and point to the shift of M. chthonoplastes from anoxygenic to oxygenic photosynthesis and stimulation of sulphide production and oxidation rates at elevated temperatures. The rate of net oxygen production per unit area of mat at maximum irradiance, J0, did not change with temperature, whereas, JZphot, the flux of oxygen across the lower boundary of the euphotic zone increased linearly with temperature. The rate of oxygen consumption per volume of aphotic mat increased with temperature. This increase occurred in darkness, but was strongly enhanced at high irradiances, probably as a consequence of increased rates of photosynthate exudation, stimulating respiratory processes in the mat. The compensation irradiance (Ec) marking the change of the mat from a heterotrophic to an autotrophic community, increased exponentially in this range of temperatures.

Cyanobacteria↗

PubMed2002

Nitrate removal by a combination of elemental sulfur-based denitrification and membrane filtration.

In this paper, a new method for removal of nitrate from groundwater, in which elemental sulfur-based denitrification (autotrophic denitrification) and membrane separation are combined, is proposed. By using a membrane, autotrophic denitrifiers, whose growth rate is considerably low, can be kept at a high concentration. The performance of the proposed process was examined through a long-term experiment in the laboratory using synthetic feed water. A rotating membrane disk module equipped with UF membrane (750,000 Da) was used in this study. Complete removal of nitrate (25 mg N/L) was achieved under the conditions of a biomass concentration of about 1000 mg protein/L and HRT of 160 min. Dissolved oxygen concentration and sulfur/biomass ratio in the membrane chamber were found to be the key factors in maintenance of high-process performance. Deterioration in membrane permeability was insignificant. It was found that membrane filtration could be continued with a water flux of 0.5 m3/m2/day for about 100 days without any chemical membrane cleaning. The proposed process, however, caused a slight increase in assimilable organic carbon. Sulfide was not detected in the denitrified water.

Biomass↗

PubMed1995

Investigation of the prebiotic synthesis of amino acids and RNA bases from CO2 using FeS/H2S as a reducing agent.

An autotrophic theory of the origin of metabolism and life has been proposed in which carbon dioxide is reduced by ferrous sulfide and hydrogen sulfide by means of a reversed citric acid cycle, leading to the production of amino acids. Similar processes have been proposed for purine synthesis. Ferrous sulfide is a strong reducing agent in the presence of hydrogen sulfide and can produce hydrogen as well as reduce alkenes, alkynes, and thiols to saturated hydrocarbons and reduce ketones to thiols. However, the reduction of carbon dioxide has not been demonstrated. We show here that no amino acids, purines, or pyrimidines are produced from carbon dioxide with the ferrous sulfide and hydrogen sulfide system. Furthermore, this system does not produce amino acids from carboxylic acids by reductive amination and carboxylation. Thus, the proposed autotrophic theory, using carbon dioxide, ferrous sulfide, and hydrogen sulfide, lacks the robustness needed to be a geological process and is, therefore, unlikely to have played a role in the origin of metabolism or the origin of life.

Amino Acids↗

PubMed2006

Hydrogen limitation--a method for controlling the performance of membrane biofilm reactor for autotrophic denitrification of wastewater.

Hydrogen-driven denitrification using the fiber membrane biofilm reactor (MBfR) was evaluated for consistent operation in tertiary wastewater treatment. The possibility of controlling the process rates, as well as biofilm parameters by supplying limited amounts of electron donor (hydrogen), was tested. Limiting the hydrogen supply proved to be efficient in controlling the biofilm growth and performance of the MBfR. Denitrification rates remained unchanged for both synthetic wastewater (SWW) and real municipal wastewater (MWW) effluent as well through the fluctuations in the substrate (NO3-N) concentration. The average denitrification rates were 0.50 (+/- 0.02) g NO3-N per day per m2 for SWW and 0.59 (+/- 0.04) g NO3-N per day per m2 for MWW. Biofilm density rather than thickness was the determining factor in substrate diffusion and biofilm sloughing, ultimately determining operating stability. Limited hydrogen supply assured constant volatile solids (VS) concentration in the biofilm. It was determined that VS/TS ratio higher than 0.25 assured stable biofilm operation. Decrease of VS/TS ratio below 0.25 led to shearing of the nonbiological outer layers of the biofilm. The values of chemical oxygen demand (COD), volatile suspended solids (VSS) and total suspended solids (TSS) in the final effluent were stable and well below wastewater effluent guidelines. Substitutions of bicarbonate with gaseous carbon dioxide as the carbon source did not affect denitrification rates despite lower than optimum pH conditions.

Biofilms↗