Bacteria and protozoa as integral components of the forest ecosystem--their role in creating a naturally varied soil fertility

The paper explores interactions between the two first organism groups to appear on earth, the bacteria and protozoa, and their interplay with the rest of the ecosystem focusing upon northern boreal forests. The microbial loop is suggested as a mechanism for local inputs of new N to the ecosystem. The possibility to couple short-term microbial processes with their long-term effects, — as registered in plants, soil and the atmosphere, via the abiotic variables — is explored. The latter are investigated in relation to the environments they create for the micro-organisms, and how this results in varying soil fertility. A chain of events is presented that relate high Ca concentration in the mineral soil and high water availability to increased nitrogen availability for plants via the micro-organisms. An example is given of the influence of these parameters directly upon protozoa along an extreme fertility gradient, and also indirect evidence from a Finnish field study of 30 sites with four fertility levels. Finally, there is a discussion about ways to convert knowledge gained in detailed studies of microbial interactions into forms useful when evaluating the present status of and effects of ameliorative management on ecosystems strongly affected by humans. This revised version was published online in August 2006 with corrections to the Cover Date.     

Physiological and Biochemical Characteristics and Capacity for Polyhydroxyalkanoates Synthesis in a Glucose-Utilizing Strain of Hydrogen-Oxidizing Bacteria, Ralstonia eutropha B8562

The physiological, biochemical, genetic, and cultural characteristics of the glucose-utilizing mutant strain Ralstonia eutropha B8562 were investigated in comparison with the parent strain R. eutropha B5786. The morphological, cultural, and biochemical characteristics of strain R. eutropha B8562 were similar to those of strain R. eutropha B5786. Genetic analysis revealed differences between the 16S rRNA gene sequences of these strains. The growth characteristics of the mutant using glucose as the sole carbon and energy source were comparable with those of the parent strain grown on fructose. Strain B8562 was characterized by high yields of polyhydroxyalkanoate (PHA) from different carbon sources (CO₂, fructose, and glucose). In batch culture with glucose under nitrogen limitation, PHA accumulation reached 90% of dry weight. In PHA, β-hydroxybutyrate was predominant (over 99 mol %); β-hydroxyvalerate (0.25–0.72 mol %) and β-hydroxyhexanoate (0.008–1.5 mol %) were present as minor components. The strain has prospects as a PHA producer on glucose-containing media.     

RNA assay as a method of viable biomass determination in the organic fraction of municipal solid waste suspension

A method of RNA determination by means of alkaline hydrolysis and UV detection was applied to evaluate the amount of viable biomass during the aerobic biodegradation of the organic fraction of the municipal solid waste suspension. The relative standard deviation of this determination was from 0.7 to 4%. The viable biomass constituted only 9% of the volatile suspended solids in the activated sludge.     

High Rate Production in Static Culture of Bacterial Cellulose from Sucrose by a Newly Isolated Acetobacter Strain

For the industrial production of bacterial cellulose from sucrose in static cultures, the possibility of a high rate of cellulose production was investigated. An Acetobacter strain, S-35, which had been isolated from a grape, was selected from 1500 isolates. This strain was found to produce a large amount of cellulose from either glucose or fructose. Using this strain, high cellulose production rates of 3.3g/liter/d or 40g/m²/d from sucrose were seen in static culture.     

Synthesis of Anabiosis Autoinducers by Non-Spore-Forming Bacteria as a Mechanism Regulating Their Activity in Soil and Subsoil Sedimentary Rocks

Non-spore-forming bacteria of the genera Arthrobacterand Micrococcus, isolated from permafrost subsoil, were found to produce greater amounts of the d ₁extracellular factor than closely related collection strains isolated from soil. The effect of this factor, responsible for cell transition to anabiosis, was not species-specific. Thus, the d ₁preparation isolated from the culture liquid of the permafrost isolate Arthrobacter globiformis245 produced an effect on the collection strain Arthrobacter globiformisB-1112 and also on Micrococcus luteusand Bacillus cereus.The d ₁preparation from the permafrost isolate of Arthrobacterdiffered from the chemical analogue of this factor, 4-n-hexylresorcinol, in the level of the induced cell response, which may have resulted from different cell sensitivity to various homologs of alkylhydroxybenzenes contained in the d ₁preparation. Thus, additional evidence was obtained indicating that autoregulation of bacterial growth and development is implemented at the level of intercellular interactions in microbial communities. Abundant production of the d ₁anabiosis-inducing factors by bacteria isolated from permafrost subsoil is probably a result of special antistress mechanisms responsible for the survival of these bacteria under extreme conditions of natural long-term cooling.     

Changes in Sexual Expression as Result of Defoliation and Environment in a Monoecious Shrub in Mexico: Implications for Pollination

Folivory may indirectly impact plant reproduction through changes in sexual expression ( i.e. , number or proportion of male and female flowers produced), which influence plant–pollinator interactions via changes in pollinator preference or efficiency. This study is an experimental evaluation of the effect that defoliation has on sex expression in the monoecious shrub Cnidoscolus aconitifolius , how such effect varies across sites, as well as how such changes indirectly affect pollinator visitation rates. The present study used three populations of C. aconitifolius , each one located in a different site in Yucatán (México): pasture, deciduous forest and subdeciduous medium height forest and three levels of defoliation: 50 percent, 100 percent, and a control (no damage). Results showed that defoliation reduced significantly the total number of male flowers produced in two of the sites. Defoliation did not impact female flower production or the proportion of female flowers produced. Finally, floral visit rates were not affected by defoliation via changes in sexual expression and neither by site or by the interaction site × defoliation. Findings showed that defoliation had an effect on sex expression in C. aconitifolius , although apparently this change did not affect the plant–pollinator interactions.     

Assessment of Soluble and Biomass K in Culture Medium Is a Reliable Tool for Estimation of K Releasing Efficiency of Bacteria

Abstract

Assessing the amount of released K from minerals in bacterial liquid culture is the main process for screening and isolation of efficient potassium releasing bacteria (KRB). This study was aimed to determine the amount of released K in solution phase or supernatant (SK) as well as microbial biomass K (MBK). Therefore, 20 different bacterial isolates belonging to the 10 bacterial genera (Beijerinckia, Klebsiella, Azotobacter, Pseudomonas, Agrobacterium, Rhizobium, Sphingomonas, Citrobacter, Microbacterium, and Achromobacter) were individually used to inoculate Aleksandrov medium in presence of biotite or muscovite. Our results from in-vitro experiments revealed that the MBK (K in pellet) is more important than in SK. Although some genera such as Azotobacter and Citrobacter released more SK (16?mg/l from biotite and 12.77?mg/l from muscovite, respectively), the Klebsiella isolates with the highest MBK could release an average of 90?mg/l total K. This study indicated that the assimilated K in microbial cells is the main part of K dissolution from minerals. Due to the fast turnover of nutrients in bacterial biomass, it can be concluded that both SK and MBK could be available for plants. It seems that the finding of this research should be considered in the isolation of KRB.

Highlights

• This study reports, assessment of soluble and biomass K in the culture medium is a reliable tool for estimation of K releasing efficiency of bacteria

• Our results from in vitro experiments revealed that the assimilated K in microbial cells is the main part of K dissolved from minerals.

• Although some genera such as Azotobacter released more K in solution phase, the Klebsiella isolates with the highest biomass K could release more total K

     

Ozonolysate of excess sludge as a carbon source in an enhanced biological phosphorus removal for low strength wastewater

Potential use of the municipal sludge ozonolysate as a carbon source was examined for phosphorus removal from low strength wastewater in a modified intermittently decanted extended aeration (IDEA) process. At ozone dosage of 0.2 g O₃/g solids, readily biodegradable COD accounted for about 36% of COD from sludge ozonolysate. The denitrification potential of ozonolysate as a carbon source was comparable to that of acetate. Although, the first order constant for phosphorus release with the ozonolysate was half that of acetate, it was much higher than that of wastewater. Continuous operation of the modified IDEA process showed that the removals of nitrogen and phosphorus were simultaneously enhanced by addition of the ozonolysate. Phosphorus release was significantly induced after complete denitrification indicating that phosphorus release was strongly depended on nitrate concentration. Effectiveness of the ozonolysate as a carbon source for EBPR was also confirmed in a track study of the modified IDEA.     

Changes in root-shoot ratio and ion uptake of maize (Zea mays L.) from soil as influenced by a plant growth regulator

A pot experiment with maize cv. Limac was conducted to investigate the influence of BAS 110.. W, a plant growth regulator (PGR), on root and shoot development and nutrient uptake. The PGR was applied via the soil with 0, 5, 10, 20, and 40 mg a.i. per pot. Shoot dry matter production was reduced to a higher degree than root length, resulting in a higher root-shoot ratio (RSR) of the treated plants. Shoots of treated plants contained higher concentrations of N, P, Ca, Mg, and unchanged K concentrations. The alterations in concentration could be explained by the changes in RSR induced by the plant growth retardant. The effect was strongest with P (+40%) which was limited by soil supply. N, Ca, and Mgconcentrations were positively influenced (+20%), there was no increase for Kvs RSR.     

In vitro Decline in Plant Cultures: Detection of a Legion of Covert Bacteria as the Cause for Degeneration of Long-term Micropropagated Triploid Watermelon Cultures

In vitro cultures of triploid seedless watermelon cv. Arka Manik displayed a decline in shoot and root growth after 4–5 years of active culturing. Visibly clean cultures upon indexing on enriched media showed covert bacteria, and a significant improvement in proliferation and rooting in response to surface sterilization. The bacteria however survived endophytically. Low pH and reduced clarity of agar gelled medium were found to mask the expression of bacteria in the tissue culture medium. Gentamycin, streptomycin or broad-spectrum bactericide cefazolin provided as a 2 ml overlay in the medium in factorial combination at 0 or 50 mg l^–1 resulted in selective suppression of some bacteria depending on the treatment and eight bacterial clones comprising of four Gram-positive (Bacillus spp.) and four-Gram negative (3 × Pseudomonas spp. and 1 × Aeromonas sp.) strains were isolated from the cultures. Provision of 50 mg l^–1 gentamycin in 2 ml overlay in the multiplication or rooting medium coupled with occasional decontamination of cultures helped in circumventing the decline problem. The plants established in the field after 6 years of active in vitro culturing appeared normal and fertile suggesting the feasibility of keeping cultures for long periods, thus saving time and other resources. Freeing the cultures from covert bacteria was complicated by the presence of different bacterial types and this will be addressed later.     

Growth requirement for N as a criterion to assess the effects of physical manipulation on nitrate uptake fluxes in spinach

The effects of physical manipulation of hydroponically grown plants of spinach (Spinacia oleracea L., cvs Subito and Glares) on nitrate uptake fluxes were studied in a long-term experiment (3 days), and in short-term label experiments (2 h) with ¹³N-nitrate and ¹⁵N-nitrate. In the long-term experiment, net nitrate uptake rate (NNUR) was measured by following the nitrate depletion in the uptake solution, which was replaced at regular intervals. In the short-term experiments, NNUR and nitrate influx were measured by simultaneous application of ¹³N-nitrate and ¹⁵N-nitrate. Plants were gently transferred into the labelled uptake solution, as is usually done in nutrient uptake studies. In addition, a more severe physical manipulation was carried out, including blotting of the roots, to mimic pretreatments which involve more handling of the plants prior to uptake measurements. Nitrate influx was measured immediately after physical manipulation and after 2 h of recovery. To assess the impact of the physical manipulation the experimentally determined nitrate uptake fluxes were compared with the N demand for growth, defined as relative growth rate (RGR) times plant nitrogen concentration (PNC) of parallel plants, which were left undisturbed. Nitrate influx and efflux were both subject to changes after physical manipulation of the plants. Physical handling, however, did not always result in an alteration of NNUR, which complicates the determination of the length of the recovery period. The impact of the handling and the time course of the recovery depended on the severity of the disturbance and were independent of the light conditions during the experiments. Even after a gentle transfer of the plants, recovery, in most cases, was not complete within 2 h. The data emphasise the need for minimal disturbance of plants during the last hours prior to nutrient uptake measurements.     

Recovery strategies for tackling the impact of phenolic compounds in a UASB reactor treating coal gasification wastewater

The impact of phenolic compounds (around 3.2 g/L) resulted in a completely failed performance in a mesophilic UASB reactor treating coal gasification wastewater. The recovery strategies, including extension of HRT, dilution, oxygen-limited aeration, and addition of powdered activated carbon were evaluated in batch tests, in order to obtain the most appropriate way for the quick recovery of the failed reactor performance. Results indicated that addition of powdered activated carbon and oxygen-limited aeration were the best recovery strategies in the batch tests. In the UASB reactor, addition of powdered activated carbon of 1 g/L shortened the recovery time from 25 to 9 days and oxygen-limited aeration of 0-0.5 mgO₂/L reduced the recovery time to 17 days. Reduction of bioavailable concentration of phenolic compounds and recovery of sludge activity were the decisive factors for the recovery strategies to tackle the impact of phenolic compounds in anaerobic treatment of coal gasification wastewater.     

State of the art of aerobic granulation in continuous flow bioreactors

In the wake of the success of aerobic granulation in sequential batch reactors (SBRs) for treating wastewater, attention is beginning to turn to continuous flow applications. This is a necessary step given the advantages of continuous flow treatment processes and the fact that the majority of full-scale wastewater treatment plants across the world are operated with aeration tanks and clarifiers in a continuous flow mode. As in SBRs, applying a selection pressure, based on differences in either settling velocity or the size of the biomass, is essential for successful granulation in continuous flow reactors (CFRs). CFRs employed for aerobic granulation come in multiple configurations, each with their own means of achieving such a selection pressure. Other factors, such as bioaugmentation and hydraulic shear force, also contribute to aerobic granulation to some extent. Besides the formation of aerobic granules, long-term stability of aerobic granules is also a critical issue to be addressed. Inorganic precipitation, special inocula, and various operational optimization strategies have been used to improve granule long-term structural integrity. Accumulated studies reviewed in this work demonstrate that aerobic granulation in CFRs is capable of removing a wide spectrum of contaminants and achieving properties generally comparable to those in SBRs. Despite the notable research progress made toward successful aerobic granulation in lab-scale CFRs, to the best of our knowledge, there are only three full-scale tests of the technique, two being seeded with anammox-supported aerobic granules and the other with conventional aerobic granules; two other process alternatives are currently in development. Application of settling- or size-based selection pressures and feast/famine conditions are especially difficult to implement to these and similar mainstream systems. Future research efforts needs to be focused on the optimization of the granule-to-floc ratio, enhancement of granule activity, improvement of long-term granule stability, and a better understanding of aerobic granulation mechanisms in CFRs, especially in full-scale applications.     

Indocyanine green clearance varies as a function of N-acetylcysteine treatment in a murine model of acetaminophen toxicity

Standard assays to assess acetaminophen (APAP) toxicity in animal models include determination of ALT (alanine aminotransferase) levels and examination of histopathology of liver sections. However, these assays do not reflect the functional capacity of the injured liver. To examine a functional marker of liver injury, the pharmacokinetics of indocyanine green (ICG) were examined in mice treated with APAP, saline, or APAP followed by N-acetylcysteine (NAC) treatment.Male B6C3F1 mice were administered APAP (200 mg/kg IP) or saline. Two additional groups of mice received APAP followed by NAC at 1 or 4 h after APAP. At 24 h, mice were injected with ICG (10 mg/kg IV) and serial blood samples (0, 2, 10, 30, 50 and 75 min) were obtained for determination of serum ICG concentrations and ALT. Mouse livers were removed for measurement of APAP protein adducts and examination of histopathology. Toxicity (ALT values and histology) was significantly increased above saline treated mice in the APAP and APAP/NAC 4 h mice. Mice treated with APAP/NAC 1 h had complete protection from toxicity. APAP protein adducts were increased in all APAP treated groups and were highest in the APAP/NAC 1 h group. Pharmacokinetic analysis of ICG demonstrated that the total body clearance (Cl_T) of ICG was significantly decreased and the mean residence time (MRT) was significantly increased in the APAP mice compared to the saline mice. Mice treated with NAC at 1 h had Cl_T and MRT values similar to those of saline treated mice. Conversely, mice that received NAC at 4 h had a similar ICG pharmacokinetic profile to that of the APAP only mice. Prompt treatment with NAC prevented loss of functional activity while late treatment with NAC offered no improvement in ICG clearance at 24 h. ICG clearance in mice with APAP toxicity can be utilized in future studies testing the effects of novel treatments for APAP toxicity.