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The enumeration of methanotrophic bacteria in the cover soil of an aged municipal landfill was carried out using (1) fluorescent in situ hybridization (FISH) with horseradish peroxidase-labeled oligonucleotide probes and tyramide signal amplification, also known as catalyzed reporter deposition-FISH (CARD-FISH), and (2) most probable number (MPN) method. The number of methanotrophs was determined in cover soil samples collected during April-November 2003 from a point with low CH(4) emission. The number of types I and II methanotrophs obtained by CARD-FISH varied from 15 +/- 2 to 56 +/- 7 x 10(8) cells g(-1) absolute dry mass (adm) of soil and methanotrophs of type I dominated over type II. The average number of methanotrophs throughout the cover soil profile was highest during May-September when the cover soil temperature was above 13 degrees C. Methanotrophs accounted for about 50% of the total bacterial population in the deepest cover soil layer owing to higher availability of substrate (CH(4)). A lower number of methanotrophs (7 x 10(2) to 17 x 10(5) cells g(-1) adm of soil) was determined by the MPN method compared to the CARD-FISH counts, thus confirming previous results that the MPN method is limited to the estimation of the culturable species that can be grown under the incubation conditions used. The number of culturable methanotrophs correlated with the methane-oxidizing activity measured in laboratory assays. In comparison to the incubation-based measurements, the number of methanotrophs determined by CARD-FISH better reflected the actual characteristics of the environment, such as release and uptake of CH(4), temperature, and moisture, and availability of substrates.

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Food industry wastewater served as a carbon source for the synthesis of poly-beta-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5 degrees C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11 degrees C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3-7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.