Field fungi

The fact that the fungal population on dew-retted flax and hemp consists very largely of the same field fungi found on field-weathered cotton fiber was noted earlier Alternaria and Cladosporium herbarum are prominent (17). 

BKects on pfants. Field fungi are primary invaders of seeds on field plat ... 

A. I Sources. Toxins of concern are produced primarily by field fungi, including Fusarnim rporotricMdrifes (T-2 toxin and DAS) and Fusarium roseum (DON). 

The other major genera that were isolated on a less frequent basis in the survey included many of the same field fungi that have been isolated from commercial tobacco samples such as Alternaria spp.> Rhizopus nigricans Fusarium spp., Cladosporium> Chaetomium> Trichoderma viride> Phoma spp., and Mucor spp. (Table A). These field fungi invade the substrate prior to harvest and require an abundance of moisture (at least 24% to 25%) on the substrate in order to support their growth (Christensen and Kaufman, 1965). 

Electroporation. When bacteria are exposed to an electric field a number of physical and biochemical changes occur. The bacterial membrane becomes polarized at low electric field. When the membrane potential reaches a critical value of 200—300 mV, areas of reversible local disorganization and transient breakdown occur resulting in a permeable membrane. This results in both molecular influx and efflux. The nature of the membrane disturbance is not clearly understood but bacteria, yeast, and fungi are capable of DNA uptake (see Yeasts). This method, called electroporation, has been used to transform a variety of bacterial and yeast strains that are recalcitrant to other methods (2). Apparatus for electroporation is commercially available, and constant improvements in the design are being made. 

Disinfection tests can be classified according to the test organism, ie, whether the test employs certain species of bacteria, fungi, or vimses classified as to whether it is a static test or a cidal test, as in a bactericidal vs bacteriostatic test or sporicidal vs sporistatic test or classified as to whether it is a microbial reduction test or an end-point test where all the organisms in the test are apparently killed. Procedures may be distinguished by in vitro or in vivo testing. Another way to consider tests is whether they are screening tests, practical type laboratory tests, or field tests. 

This section considers, in three separate chapters, the anatomy and physiology of bacteria, fungi and yeasts, and viruses, together with a survey of the characters of individual members of these groups likely to be of importance to the applied field covered by this book. Additional information is provided about more rapid methods for detecting bacteria. The final chapter in this section (Chapter 4) considers the principles of microbial pathogenicity and epidemiology. 

Although a number of white-rot fungi have been examined and shown to degrade PAHs (Field et al. 1992), greatest attention has probably been directed to Phanerochaete chrysosporium and Pleurotus ostreatus, and to the PAHs anthracene, phenanthrene, pyrene, and benzo[a]pyrene that will be used to illustrate the cardinal principles. A substantial fraction of PAHs may also be sorbed to the biomass—40% for phenanthrene and 22% for benzo[a]pyrene (Barclay et al. 1995). The degree of mineralization of PAHs by white-rot fungi may sometimes be quite low, for example, for Pleurotus ostreatus, yields were 3.0, 0.44, 0.19, and 0.19% for phenanthrene, pyrene, fluorene, and benzo[a]pyrene, respectively (Bezalel et al. 1996a). 

Field JA, E de Jong, GF Costa GF, JAM de Bont (1992) Biodegradation of polycyclic aromatic hydrocarbons by new isolates of white-rot fungi. Appl Environ Microbiol 58 2219-2226. 

Lueders T, B Wagner, P Claus, MW Friedrich (2004a) Stable isotope probing of rRNA and DNA reveals a dynamic methylotroph community and trophic interactions with fungi and protozoa in oxic rice field soil. Environ Microbiol 6 60-72. 

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