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To investigate the potential transfer of Escherichia coli O157:H7 from contaminated manure to fresh produce, lettuce seedlings were transplanted into soil fertilized with bovine manure which had been inoculated with approximately 10 4 CFU g ؊1 E. coli O157:H7. The lettuce was grown for approximately 50 days in beds in climate-controlled rooms in a greenhouse. As the bacterium was not detected in the edible parts of the lettuce, the outer leaves of the lettuce, or the lettuce roots at harvest it was concluded that transmission of E. coli O157:H7 from contaminated soil to lettuce did not occur. The pathogen persisted in the soil for at least 8 weeks after fertilizing but was not detected after 12 weeks. Indigenous E. coli was detected only sporadically on the lettuce at harvest, and enterococci were not detected at all. The numbers of enterococci declined more rapidly than those of E. coli in the soil. Pseudomonas fluorescens, which inhibited growth of E. coli O157:H7 in vitro, was isolated from the rhizosphere.

A cellulolytic anaerobic bacterium, strain 177RlBT, was isolated from a biomat sample of an Icelandic, slightly alkaline, hot spring (78 "C). Strain 177R1BT was rod-shaped, non-spore-forming, non-motile and stained Gram-negative at all stages of growth. It grew at 45-82 "C, with an optimum growth temperature around 78 "C. A t 70 "C, growth occurred at pH 58-8-0, with an optimum near pH 7.0. At the optimum temperature and pH, with 2 g cellobiose I-' as substrate, strain 177R1BT had a generation time of 2 h. During growth on Avicel, strain 177R1BT produced acetate, hydrogen and carbon dioxide as major fermentation products together with small amounts of lactic acid and ethanol. INTRODUCTIONAnaerobic micro-organisms from extreme environments and, in particular, their fermentation products and thermostable enzymes, have been the subject of much research over the past 15-20 years. Much interest has been centred on the cellulose-and hemicellulosedegrading bacteria, as these polymers constitute a large renewable resource in nature. Many of the validly described anaerobic, thermophilic, cellulose-degrading bacteria form spores and are placed in the genus Clostridium (Wiegel, 1992). In contrast, a number of anaerobic, cellulolytic, extremely thermophilic, non-spore-forming bacteria have been isolated (Huang et al., 1998;Hudson et al., 1990; t Present address: MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 As, Norway.The EMBL accession number for the 165 rRNA gene sequence of strain l77R1 BT is NO0481 1. Rainey et al., 1993a; Sissons et al., 1987;Svetlichnii & Svetlichnaya, 1988; Svetlichnii et al., 1990; Taya et al., 1985; Wiegel, 1992). The cellulolytic strains have been mostly isolated from neutral to alkaline hot springs. Two strains were isolated from compost (Rainey et al., 1993a) and Caldicellulosiruptor owensensis was isolated from sediment taken from Owens Lake, California, USA (Huang et al., 1998). Common features of the isolates are their high temperature habitat, ability to ferment polysaccharides, high optimum growth temperature (68-75 "C), a maximum growth temperature lower than 85 OC, a pH range for growth between pH 4.0 and 9-0, and their apparent lack of ability to form spores. By comparative 16s rDNA sequence studies, Rainey and co-workers, and later Huang and co-workers, have shown that these organisms cluster together in one group (Huang et al., 1998; Rainey et al., 1993a, b;Rainey & Stackebrandt, 1993). MladenovskaIn the present study, we have characterized a new METHODSAll diagnostic tests were performed at least twice, with triplicate determinations. Mean values are reported.Growth medium. The anaerobic medium used for cultivation was as previously described (Angelidaki et al., 1990), with the following adjustments. Avicel (2 g IF1 ; microcrystalline cellulose, FMC International) was used as carbon and energy source. The medium was supplemented with 0.10 g yeast extract 1-1 and no cysteine was added. The medium was adjusted to pH 7.0 and autoclaved at 140 "C for 20 min. Befor...