Changes in populations of soil microorganisms,nematodes, and enzyme activity associated with application of powdered pine bark

Evaluation of enzyme activities in combination with taxonomic analyses may help define the mechanisms involved in microbial decomposition of orgaic amendments and biological control of soilborne pathogens. In this study, powdered pine bark was added to nematode-infested soil at rates of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 g kg^–1. Total fungal populations did not differ among treatments immediately after application of pine bark. After 7 days, fungal populations were positively correlated with increasing levels of pine bark. This increase was sustained through 14 and 21 days.Penicillium chrysogenum andPaecilomves variotii were the predominant fungal species isolated from soil amended with pine bark. Total bacterial populations did not change with addition of pine bark at 0, 7, and 14 days after treatment. At 21 and 63 days, total bacterial populations declined in soil receiving the highest rates of pine bark. Addition of pine bark powder to soil caused a shift in predominant bacterial genera fromBacillus spp. in nonamended soil, toPseudomonas spp. in amended soil. Soil enzyme activities were positively correlated with pine bark rate at all sampling times. Trehalase activity was positively correlated with total fungal populations and with predominant fungal species, but was not related to bacterial populations. The number of non-parasitic (non-stylet bearing) nematodes andMeloidogyne arenaria in soil and roots were not correlated with pine bark rate. However,Heterodera glycines juveniles in roots, and the number of cysts g^–1 root, declined with increasing levels of pine bark.Journal Series Series No. 18-933598 Alabama Agricultural Experiment Station     

Microbial indicators for sawdust and bark compost stability and humification processes

To what extent some microbial index ratios are suitable for use as early criteria for the level of compost stability during aerobic composting of coniferous sawdust and bark at mesophilic conditions was studied. Evolution of the specific respiration activity (CO₂-C/biomass C) and the ratios between some groups of microorganisms were followed as a function of composting time. The specific respiration activity was found to be an early and most reliable indicator of compost stability. The peroxidase and polyphenoloxidase enzyme activity during composting, as well as the composition of newly-formed humus substances were studied. The duration of composting increased the quality of newly-formed humus substances (C_h.a.:C_f.a ratio; Ca-complexed humic acid and resistance of organo-mineral complexes). The quality of humus substances could be used to assess compost stability. However, the results can be applied only under defined conditions.     

生淀粉高浓度酒精发酵的研究

本研究利用国内常用的糖化酶制剂糖化生玉米面中的淀粉,同时接种酵母菌,在30℃下,探讨了玉米淀粉的高浓度酒精发酵工艺。选择到了一株产高浓度酒精酵母菌,H0菌株。发酵温度为30℃、pH4一s、加糖化酶量为每克原料300单位、酵母接种量3％(v／v)和原料加量为33．0％(w／v)时,这株酵母菌在70小时内可产生17．5％(v／v)的乙醇。如果原料加量为36．0％(w／v)时,该菌株在96小时内可以产生18．O％(v／v)的乙醇。在前一种加料情况下,成熟发酵醪中的pH为5、残还原糖为O．19％、残总糖为3．5“。在后一种加料情况下,成熟发酵醪中的pH为5、残还原糖为0．81％、残总糖为5．1％。     

Detection of mycoplasma contaminations by the polymerase chain reaction

The polymerase chain reaction (PCR) has been used for the general detection ofMollicutes. 25Mycoplasma andAcholeplasma species were detected including important contaminants of cell cultures such asM. orale, M. arginini, M. hyorhinis, M. fermentans, A. laidlawii and additional human and animal mycoplasmas. PCR reactions were performed using a set of nested primers defined from conserved regions of the 16S rRNA gene. The detection limit was determined to be 1 fg mycoplasma DNA, which is equivalent to 1–2 genome copies of the 16S rRNA coding region. The identity of the amplification products was confirmed by agarose gel electrophoresis and restriction enzyme analysis. DNA from closely and distantly related micro-organisms did not give rise to specific amplification products. The method presented here offers a much more sensitive, specific and rapid assay for the detection of mycoplasmas than the existing ones.     

Algae as indicators of environmental change

Despite an increased awareness by governments and the general public of the need for protecting all types of aquatic habitats, human impacts continue to impair the services that these ecosystems provide. Increased monitoring activities that locus on all major biological compartments are needed to quantify the present condition of Earth's aquatic resources and to evaluate the effectiveness of regulations designed to rehabilitate damaged ecosystems. Algae are an ecologically important group in most aquatic ecosystems but are often ignored as indicators of aquatic ecosystem change. We attribute this situation both to an underappreciation of the utility of algal indicators among non-phycologists and to a lack of standardized methods for monitoring with algae.Because of their nutritional needs and their position at the base of aquatic foodwebs, algal indicators provide relatively unique information concerning ecosystem condition compared with commonly used animal indicators. Algae respond rapidly and predictably to a wide range of pollutants and, thus, provide potentially useful early warning signals of deteriorating conditions and the possible causes. Algal assemblages provide one of the few benchmarks for establishing historical water quality conditions and for characterizing the minimally impacted biological condition of many disturbed ecosystems. Preliminary comparisons suggest that algal indicators are a cost-effective monitoring tool as well.Based on available evidence from field studies, we recommend development of taxonomic indicators based on diatoms (Bacillariophyceae) as a standardized protocol for monitoring ecosystem change. Both population- and community-level indices have inherent strengths, and limitations and information from both levels of biological organization should be utilized in tandem. However, further information concerning species tolerances to a variety of anthropogenic stressors is needed if autecological indices are to be used routinely for monitoring purposes. While functional measures (e.g. productivity) may also prove useful as monitoring tools, further investigation is required to characterize the reliability of alternative methodologies and to assess the consistency of these indicators under varying field conditions.Author for correspondence     

Growth response of marigold (Tagetes erecta L.) to inoculation withGlomus mosseae,Trichoderma aureoviride andPythium ultimum in a peat-perlite mixture

The interactions between the mycorrhizal fungusGlomus mosseae, the plant pathogenPythium ultimum, and a pathogen-antagonistTrichoderma aureoviride in the rhizosphere ofTagetes erecta (marigold) were studied for their effects on plant growth in a peat-perlite substrate. Mycorrhizal fungus inoculation protected the plant againstP. ultimum, since both phytomass production and foliar development were higher in mycorrhizal plants.T. aureoviride had no effect on nonmycorrhizal plants in the presence or absence ofP. ultimum. However, more biomass was produced by mycorrhizal plants whenT. aureoviride was present, whether or not soil was infested withP. ultimum. ei]R Rodriguez-Kabana     

Physico-chemical characteristics of a permanent Spanish hypersaline lake: La Salada de Chiprana (NE Spain)

La Salada de Chiprana Lake, located in the Ebro River basin, northeastern Spain, is the only permanent and deep water hypersaline ecosystem in all of western Europe. With a total surface of 31 ha and a maximum depth of 5.6 m, it has several basins bounded by elongated sandstone-bodies or ribbons which are paleochannels of Miocene age. Its salinity varied from 30 to 73 g 1^–1 during the 1989 hydrological cycle and the most abundant ions were magnesium and sulphate. Depth-time distributions of major physico-chemical variables demonstrated that the lake was stratified in two distinctive layers during most of the year. The chemocline disappeared only in October, with the complete overturn of the water column. In the deep water, three conditions occurred which allowed development of green sulphur bacteria populations: (1) oxygen depletion, (2) presence of hydrogen sulphide and (3) presence of light. Benthic microbial mats covered the sediments of shallow shores of moderate slope.     

Continuous measurement of microbial heat production in laboratory fermentors

The possibility of continuously measuring the heat produced by microorganisms in an ordinary laboratory fermentor was studies. An inventory of the heat flows influencing the temperature of the culture was made. The magnitude and standard deviation in these heat flows were studied from theoretical and practical viewpoints. Calibration procedures were tested, and a model describing the heat flows in steady state and during dynamic conditions was made. Microbial heat production could be calculated accurately with the help of this model, appropriate temperature measurements, and equipment properties measured during the calibration procedures. It was found that the measurement of heat production could be done with an accuracy similar to that in the O(2) uptake measurement. (c) 1993 John Wiley & Sons, Inc.     

Kinetics of competitive inhibition and cometabolism in the biodegradation of benzene, toluene, and p-xylene by two Pseudomonas isolates

Two Pseudomonas species (designated strains B1 and X1) were isolated from an aerobic pilot-scale fluidized bed reactor treating groundwater containing benzene, toluene, and p-xylene (BTX). Strain B1 grew with benzene and toluene as the sole sources of carbon and energy, and it cometabolized p-xylene in the presence of toluene. Strain X1 grew on toluene and p-xylene, but not benzene. In single substrate experiments, the appearance of biomass lagged the consumption of growth substrates, suggesting that substrate uptake may not be growth-rate limiting for these substrates. Batch tests using paired substrates (BT, TX, or BX) revealed competitive inhibition and cometabolic degradation patterns. Competitive inhibition was modeled by adding a competitive inhibition term to the Monod expression. Cometabolic transformation of nongrowth substrate (p-xylene) by strain B1 was quantified by coupling xylene transformation to consumption of growth substrate (toluene) during growth and to loss of biomass during the decay phase. Coupling was achieved by defining two transformation capacity terms for the cometabolizing culture: one that relates consumption of growth substrate to the consumption of nongrowth substrate, and second that relates consumption of biomass to the consumption of nongrowth substrate. Cometabolism increased decay rates, and the observed yield for strain B1 decreased in the presence of p-xylene. (c) 1993 Wiley & Sons, Inc.     

Morphology,distribution, and preservation potential of microbial mats in the hydromagnesite-magnesite playas of the Cariboo Plateau,British Columbia,Canada

Benthic microbial mats are common in the alkaline hydromagnesite-magnesite playa lakes of Interior British Columbia. Four main zones are recognized based on mat morphology that can be related to the type and duration of wetting. From the basin margin toward the playa centre they are: (i) vegetated hummocky ground; (ii) polygonal hummocky ground; (iii) low-domal and stratiform mats, and (iv) laterally continuous and pustular mats. Mats in peripheral mudflats are commonly mineralized by hydromagnesite, mostly precipitated by capillary evaporation of shallow groundwaters. Mats forming in the ephemeral lake tend to have lower carbonate content.Although widespread, the mats are poorly preserved in the Holocene sedimentary record. Underlying sediments are commonly weakly bedded, disturbed or massive. Desiccation, dehydration, wetting-drying cycles, and grazing by invertebrates cause fragmentation of mats at the surface, facilitating erosion. Cryogranulation, interstitial mineral precipitation, vesiculation, bioturbation, compaction, and volume changes associated with diagenesis, disrupt and destroy lamination in the upper few centimetres. Most surviving organic matter is lost by early microbial degradation.