Heribert Insam

Relationship between soil organic carbon and microbial biomass on chronosequences of reclamation sites

The interrelationship between soil microorganisms and soil organic carbon was studied on an agricultural and on a forest chronosequence of open-pit mine reclamation soils. Thirty years after reclamation, soil carbon levels of 0.8% on the agricultural sites and 1.7% on the forest sites (A-horizon) were reached. Microbial biomass rose very fast to levels characteristic of undisturbed soils. Microbial carbon (Cmier) was 57 mg·100 g−1 soil after 15 years on the agricultural sites and 43 mg·100 g−1 on the forest sites. The contribution of Cmier to the total organic carbon (Corg) decreased with time, more rapidly on the forest sites than on the agricultural ones. From the Cmierr/Corg ratio it became evident that both chronosequences had not yet reached a steady state within the 50 years of reclamation. A significant decrease of the metabolic quotient qCO2 (microbial respiration per unit biomass) with time was observed on the agricultural sites but not on the forest sites. The Cmier/Corg ratio proved to be a reliable soil microbial parameter for describing changes in man-made ecosystems. For evaluating reclamation efforts, the Cmier/Corg ratio can be considered superior to its single components (Cmier or Corg) and to other parameters.

EVALUATION OF METHODS TO ESTIMATE THE SOIL MICROBIAL BIOMASS AND THE RELATIONSHIP WITH SOIL TEXTURE AND ORGANIC MATTER

Abstract Three methods to estimate soil microbial biomass, CHC13 fumigation-incubation (CFI), CHC13 fumigation-extraction (CFE), and substrate-induced respiration (SIR), were compared with each other and with arginine ammonification and basal respiration using soils over a wide range of textural classes and organic matter content. Biomass and activity of the soil microflora were significantly related to clay, soil organic C and especially to total N content. Values for microbial biomass C as estimated by CFI, CFE and SIR were highly correlated and not affected by soil texture. Only the estimation of biomass C by CFE was slightly influenced by soil organic matter including the two peat soils into the regression analysis. While the absolute values for biomass C deviated considerably when estimated by CFI, CFE and SIR, the ranking of the soils was the same for all these methods. These differences were usually not caused by the abiotic soil conditions we examined. The factors to convert the additional amount of organic C extracted after CHC13 fumigation or the substrate-induced respiration to microbial biomass C are discussed.

Soil microbial biomass and respiration measurements: an automated technique based on infra-red gas analysis

An automated system for continuous soil respiration and microbial biomass measurements based on Infra Red Gas Analysis was constructed. The switching device is computer controlled and allows hourly measurements of up to 24 samples when switching intervals of 2.5 min are selected. This allows the use of the substrate-induced respiration method for biomass determination. A software package to run the system was developed.

A New Set of Substrates Proposed for Community Characterization in Environmental Samples

The selection of substrates offered on commercially available multisubstrate plates (Biolog®, PhenePlate®) is not targeted at environmental samples. In a post-conference workshop of the SUBMECO conference at Innsbruck, Austria (Oct. 16–18, 1996) the need for a set of substrates meeting the requirements of environmental analyses was recognized. Further, a reduction in the number of substrates was advised to allow statistics at a reasonable number of replications (Hitzl et al., 1997b). Also Haack et al. (1995) argued that far less substrates than the 95 offered on the Biolog plates are sufficient to distinguish between microbial communities of terrestrial and aquatic ecosystems. According to the information given by Hitzl et al. (1997a), Campbell et al. (1997), Bochner (pers. comm.) and to previous experience with phenolic compounds (Burkhardt et al., 1993) I proposed a 96-well microplate with 31 substrates plus control, each in 3 replications (Table 1). Such ‘EcoPlates’ are now available from Biolog®.

Microbiology of composting

Microbial Communities.- How Resilient Are Microbial Communities to Temperature Changes During Composting?.- Survey of Fungal Diversity in Mushroom Compost Using Sequences of PCR-Amplified Genes Encoding 18S Ribosomal RNA.- Bacterial Community Structure During Yard Trimmings Composting.- Characterisation of Microbial Communities During Composting of Organic Wastes.- Microbial Succession During Composting of Source-Separated Urban Organic Household Waste Under Different Initial Temperature Conditions.- Bacterial Diversity in Livestock Manure Composts as Characterized by Terminal Restriction Fragment Length Polymorphisms (T-RLFP) of PCR-amplified 16S rRNA Gene Sequences.- Amplified 16S Ribosomal DNA Restriction Analysis of Microbial Community Structure During Rapid Degradation of a Biopolymer, PHA, by Composting.- Comparative Investigation of Vermicompost Microbial Communities.- Processes and Controls.- Heat Production During Thermophilic Decomposition of Municipal Wastes in the Dano-System Composting Plant.- Composting of Different Horticultural Wastes: Effect of Fungal Inoculation.- Backyard Composting: General Considerations and a Case Study.- N-Dynamics During Composting - Overview and Experimental Results.- Unsuitability of Anaerobic Compost from Solid Substrate Anaerobic Digestion as a Soil Amendment.- Pile Composting of Two-phase Centrifuged Olive Husks: Bioindicators of the Process.- Organic Acids as a Decisive Limitation to Process Dynamics During Composting of Organic Matter.- Effects of Interrupted Air Supply on the Composting Process - Composition of Volatile Organic Acids.- Reduction of Ammonia Emission and Waste Gas Volume by Composting at Low Oxygen Pressure.- Review of Compost Process-Control for Product Function.- Using Agricultural Wastes for Tricholoma crassum (Berk.) Sacc. Production.- Microbial Transformation of Nitrogen During Composting.- Effect of Additives on the Nitrification-Denitrification Activities During Composting of Chicken Manure.- Biodegradability.- Biodegradability Study on Films for Packaging Based on Isotactic Polypropylene Modified with Natural Terpene Resins.- Isolation and Characterization of Thermophilic Microorganisms Able to Grow on Cellulose Acetate.- PCBs Biotransformation by a White-Rot Fungus Under Composting and Liquid Culture Conditions.- Tests on Composting of Degradable Polyethylene in Respect to the Quality of the End-Product Compost.- Microbial Degradation of Sulfonylurea Herbicides:Chlorsulfuron and Metsulfuron-Methyl.- Maturity Testing.- Hydrogen Peroxide Effects on Composting and Its Use in Assessing the Degree of Maturity.- Plant Performance in Relation to Oxygen Depletion, CO2-Rate and Volatile Organic Acids in Container Media Composts of Varying Maturity.- Microbiological and Chemical Characterisation of Composts at Different Levels of Maturity, with Evaluation of Phytotoxicity and Enzymatic Activities.- Monitoring of a Composting Process: Thermal Stability of Raw Materials and Products.- Compost Maturity - Problems Associated with Testing.- Use of CLPP for Evaluating the Role of Different Organic Materials in Composting.- Evaluation of Organic Matter Stability During the Composting Process of Agroindustrial Wastes.- Characterization of Organic Substances in Stabilized Composts of Rest Wastes.- Application and Environmental Impact.- Composting of Posidonia oceanica and Its Use in Agriculture.- Practical Use of Quality Compost for Plant Health and Vitality Improvement.- Environmental Impacts of Cattle Manure Composting.- Agronomic Value and Environmental Impacts of Urban Composts Used in Agriculture.- Composting in the Framework of the EU Landfill Directive.- Occurence of Aspergillus fumigatus in a Compost Polluted with Heavy Metals.- Important Aspects of Biowaste Collection and Composting in Nigeria.- Plant and Human Pathogens.- Use of Actinobacteria in Composting of Sheep Litter.- Methods for Health Risk Assessment by Clostridium botulinum in Biocompost.- The Fate of Plant Pathogens and Seeds During Backyard Composting of Vegetable, Fruit and Garden Waste.- Survival of Phytopathogen Viruses During Semipilot-Scale Composting.- Air-Borne Emissions and Their Control.- Composting Conditions Preventing the Development of Odorous Compounds.- Odour Emissions During Yard Waste Composting: Effect of Turning Frequency.- Imission of Microorganisms from Composting Facilities.- Molecular Identification of Airborne Microorganisms from Composting Facilities.- Bioaerosols and Public Health.- Passively Aerated Composting of Straw-Rich Organic Pig Manure.

Volatile organic compounds (VOCs) in soils

Soils may act as sources or sinks of volatile organic compounds (VOCs). Many of the formed VOCs are produced by microorganisms, and it would be a challenge to investigate soil microbial communities by studying their VOC profile. Such “volatilomics” would have the advantage of avoiding extraction steps that are often a limit in genomic or proteomic approaches. Abundant literature on microbially produced VOCs is available, and in particular novel detection methods allow additional insight. The aim of this paper was to give an overview on the current knowledge of microbial VOC emissions from soils.

Microbial diversity in soil: ecological theories, the contribution of molecular techniques and the impact of transgenic plants and transgenic microorganisms

This review mainly discusses three related topics: the application of ecological theories to soil, the measurement of microbial diversity by molecular techniques and the impact of transgenic plants and microorganisms on genetic diversity of soil. These topics were debated at the Meeting on Soil Emergency held in Erice (Trapani, Italy) in 2001 for the celebration of the 50th anniversary of the Italian Society of Soil Science. Ecological theories have been developed by studying aboveground ecosystems but have neglected the belowground systems, despite the importance of the latter to the global nutrient cycling and to the presence of life on the Earth. Microbial diversity within the soil is crucial to many functions but it has been difficult in the past to determine the major components. Traditional methods of analysis are useful but with the use of molecular methods it is now possible to detect both culturable and unculturable microbial species. Despite these advances, the link between microbial diversity and soil functions is still a major challenge. Generally studies on genetically modified bacteria have not addressed directly the issue of microbial diversity, being mainly focused on their persistence in the environment, colonization ability in the rhizosphere, and survival. Concerns have been raised that transgenic plants might affect microbial communities in addition to environmental factors related to agricultural practice, season, field site and year. Transgenic plant DNA originating from senescent or degraded plant material or pollen has been shown to persist in soil. Horizontal transfer of transgenic plant DNA to bacteria has been shown by the restoration of deleted antibiotic resistance genes under laboratory in filter transformations, in sterile soil or in planta. However, the transformation frequencies under field conditions are supposed to be very low. It is important to underline that the public debate about antibiotic resistant genes in transgenic plants should not divert the attention from the real causes of bacterial resistance to antibiotics, such as the continued abuse and overuse of antibiotics prescribed by physicians and in animal husbandry.

Changes in functional abilities of the microbial community during composting of manure

The objective of this study was (a) to detect changes of the functional abilities of the microflora during composting of manure as a result of windrow turning frequency and (b) to detect differences between distinct zones within the windrows. Biolog GN microtiter plates containing 95 different carbon sources were inoculated with diluted suspensions of compost material containing 15,000 microorganisms per well (120 μl). We found a dramatic shift in functional microbial community structure during the 8-week composting process. The shift was more rapid when the compost windrows were turned. The substrate use pattern in the outer, well-aerated zone of the unturned windrow was similar to that of the turned windrows. Microbial biomass and respiration decreased more rapidly in the turned than in the unturned windrows, indicating a different pace of compost maturation. The data suggest that the Biolog assay may be a suitable approach to determine compost maturity.

Investigation into the effect of high concentrations of volatile fatty acids in anaerobic digestion on methanogenic communities.

Highlights • Different methanogenic communities in mesophilic and thermophilic reactors.• High VFA levels do not cause major changes in archaeal communities.• Real-time PCR indicated greater diversity than ANAEROCHIP microarray.

Effects of heavy metal stress on the metabolic quotient of the soil microflora

Abstract A variety of quantitative measurements such as viable counts, microbial biomass (C mic ), respiration, enzyme activities or ATP contents may be used to study the effects of heavy metals on the soil microflora (Babich and Stotzky, 1985; Brookes et al. , 1986). Studies on biochemical abilities of certain isolates, such as heavy metal resistance, have also been made (e.g. Schmidt and Schlegel, 1989). Few papers address the physiological status of the microbial community. Among them are studies on the metabolic quotient (qCO 2 ), which is respiratory CO 2 release per unit biomass. A change of qCO 2 may indicate (i) changes in substrates that an unchanged community uses, (ii) a change of community composition, (iii) a change in both (i) and (ii), (iv) no changes of substrates or community, but a change in the physiological status of the community due to altered maintenance requirements. The results of the studies on qCO 2 -response upon heavy metal contamination, however, are contradictory, since some authors reported an increase (Brookes and McGrath, 1984; Fliesbach et al. , 1994; Ortiz et al. , 1993) and some a decrease of the qCO 2 (Baath et al. , 1991).