Methane cycling within compost heaps has not yet been investigated in detail. We show that thermophilic methane oxidation occurred after a lag phase of up to one day in 4-week old, 8-week old and mature (>10-week old) compost material. The potential rate of methane oxidation was between 2.6 and 4.1 micromol CH4(gdw)(-1)h(-1). Profiles of methane concentrations within heaps of different ages indicated that 46-98% of the methane produced was oxidised by methanotrophic bacteria. The population size of thermophilic methanotrophs was estimated at 10(9) cells (gdw)(-1), based on methane oxidation rates. A methanotroph (strain KTM-1) was isolated from the highest positive step of a serial dilution series. This strain belonged to the genus Methylocaldum, which contains thermotolerant and thermophilic methanotrophs. The closest relative organism on the basis of 16S rRNA gene sequence identity was M. szegediense (>99%), a species originally isolated from hot springs. The temperature optimum (45-55 degrees C) for methane oxidation within the compost material was identical to that of strain KTM-1, suggesting that this strain was well adapted to the conditions in the compost material. The temperatures measured in the upper layer (0-40 cm) of the compost heaps were also in this range, so we assume that these organisms are capable of effectively reducing the potential methane emissions from compost.

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A Gram-positive, non-endospore-forming bacterium (GW41-1564 T ) was isolated from soil. Comparison of 16S rRNA gene sequences showed that strain GW41-1564 T is a member of the genus Streptomyces, exhibiting highest similarities with Streptomyces hainanensis YIM 47672 T (97.8 %) and Streptomyces cacaoi subsp. cacaoi NBRC 12748 T (97.5 %). Strain GW41-1564 T could be distinguished from any other Streptomyces species with validly published names by sequence similarity values less than 97.5 %. Strain GW41-1564 T exhibited an unusual quinone system, with the predominant compounds MK-10(H 4 ) and MK-10(H 6 ) and smaller amounts of MK-9(H 4 ) and MK-9(H 6 ). The type strain of the most closely related species, S. hainanensis YIM 47672 T , also contained an unusual quinone system composed of MK-9(H 6 ) and MK-9(H 8 ) in addition to MK-9(H 4 ) and MK-10(H 0 ), whereas the type strain of the second most closely related species, S. cacaoi NBRC 12748 T , contained a quinone system, composed of MK-9(H 6 ) and MK-9(H 8 ), typical of Streptomyces. The polar lipid profile of GW41-1564 T consisted of the predominant compound diphosphatidylglycerol, moderate amounts of phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol and minor to trace amounts of two phosphatidylinositol mannosides and several unknown lipids, and the major fatty acids were iso-C 16 : 0, anteiso-C 17 : 1 v9c and anteiso-C 17 : 0 . The results of physiological and biochemical tests allowed further phenotypic differentiation of strain GW41-1564 T from the related species S. hainanensis. Strain GW41-1564 T clearly merits species status, and we propose the name Streptomyces specialis sp. nov., with the type strain GW41-1564 T (5DSM 41924 T 5CCM 7499 T ).

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