Microbial heterotrophs

A new concept for improved CSO impact assessment must include physical and microbial characteristics and processes. As far as the microbial heterotrophic transformations are concerned, intensive investigations have shown that suspended particles originating from sewer sediments follow the concept for wastewater depicted in Figure 5.5 (Vollertsen and Hvitved-Jacobsen, 1998 Vollertsen and Hvitved-Jacobsen, 1999 Vollertsen et al., 1999). This finding is important, because it shows that the concept and corresponding model developed for transformations of wastewater in sewers... 

Gremm, T. J., and L. A. Kaplan. 1998. Dissolved carbohydrate concentration, composition, and bioavailability to microbial heterotrophs in stream water. Acta Hydrochimica Hydro-biologica 26 167—171. 

Where primary production is the sole source of organic matter for heterotrophic N formation, the maximum ratio of heterotrophic organic N (HON) formation to autotrophic organic N (AON) formation can be calculated from autotrophic production (AP), microbial heterotrophic production (MHP), and the C N ratios of autotrophs (C Naut) and microbial heterotrophs (C N ), such that... 

Kaplan, L. A., and T. L. Bott. 1983. Microbial heterotrophic utilization of dissolved organic matter in a piedmont stream. Freshwater Biology 13 363-377. 

Numerous studies have attempted to sort out the nature of relationships among the values of microbial heterotrophic carbon substrates, biomass and individual biomarker compounds. For example, Abraham et al. (2000) evaluated the contents of fatty acids derived from different lipid classes within prokaryotic and fungal heterotrophs that were grown on glycerol, glucose, lactose or a complex medium. Consistent with previous work (e.g. Monson and Hayes 1980, 1982a,b Zyakun et al. 1998), biomass and lipids in this study were isotopically depleted relative to the substrate for organisms... 

J. L. Garland and A. L. Mills, Classification and characterisation of heterotrophic microbial communities on the basis of patterns of community-level sole carbon-source utilisation, Appl. Environ. Microbiol. 57 2351 (1991). 

Garland JL, Mills AL (1991) Classification and characterization of heterotrophic microbial communities on the basis of patterns of community-level sole-carbon-source utilization. Appl Environ Microbiol 57 2351-2359 Giuffre L, Piccolo G, Rosell R, Pascale C, Heredia OS, Ciarlo E (2001) Anthropogenic effect on soil organic phosphorus fractions in tropical ecosystems. Commun Soil Sci Plant Anal 32 1621-1628 Gottlieb S (1976) The production and role of antibiotics in soil. J Antibiot 29 987-1000... 

Measurement of exoenzymatic activities is potentially useful in detecting the effects of toxicants on heterotrophic biofilm communities. Sensitivity and direct relationship with organic matter use and, therefore, microbial growth make extracellular enzyme activities a relevant tool to assess the toxicity of specific compounds. Use of novel approaches that combine enzymatic and microscopic tools (e.g. ELF-phosphatase) may be extremely useful to detect anomalies at the sub-cellular scale. 

In a system defined by wastewater in a sewer network, the heterotrophic bacteria dominate the microbial community, i.e., organic compounds are required as a carbon source. Furthermore, the energy source (electron donor) for the heterotrophs is primarily also organic compounds, i.e., the heterotrophs that dominate wastewater in sewers are chemoheterotrophic (chemoorganotrophic) microorganisms. 

An example of an aerobic, heterotrophic microbial reaction is the degradation of glucose (cf. Examples 2.2 and 2.3) ... 

When wastewater components are applied as model parameters for simulation of the transformations taking place in a sewer, the fundamental requirements depend on model objectives. A basic requirement (following the concept depicted in Figure 2.2) is that the following two types of components be included when focusing on the heterotrophic microbial transformations ... 

This chapter deals with the microbial transformations of wastewater under aerobic conditions in a sewer network. It emphasizes the transformations of the organic matter and includes processes in both the water phase and the biofilm. Furthermore, transformations of particles in suspension originating from sewer sediments are included. A concept and a corresponding model for the integration of the major microbial processes, i.e., growth of the heterotrophic biomass, the respiration and the hydrolysis, are also dealt with. The basic chemical and biological aspects of sewer processes are focused on in Chapters 2 and 3. The reaeration process is dealt with in Chapter 4. 

---